Publications by authors named "Petter Aadahl"

38 Publications

Cardiac surgery does not lead to loss of oscillatory components in circulatory signals.

Physiol Rep 2020 05;8(9):e14423

Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology, Trondheim, Norway.

The circulatory system is oscillatory in its nature. Oscillatory components linked to physiological processes and underlying regulatory mechanisms are identifiable in circulatory signals. Autonomic regulation is essential for the system's ability to deal with external exposure, and the integrity of oscillations may be considered a hallmark of a healthy system. Loss of complexity is seen as a consequence of several diseases and aging. Heart rate variability is known to decrease after cardiac surgery and remain reduced for up to 6 months. Oscillatory components of circulatory signals are linked to the system's overall complexity. We therefore hypothesize that the frequency distributions of circulatory signals show loss of oscillatory components after cardiac surgery and that the observed changes persist. We investigated the development of the circulatory frequency distributions of eight patients undergoing cardiac surgery by extracting three time series from conventional blood pressure and electrocardiography recordings: systolic blood pressure, heart rate, and amplitude of the electrocardiogram's R-wave. Four 30-min selections, representing key events of the perioperative course, were analyzed with the continuous wavelet transform, and average wavelet power spectra illustrated the circulatory frequency distributions. We identified oscillatory components in all patients and variables. Contrary to our hypothesis, they were randomly distributed through frequencies, patients, and situations, thus, not representing any reduction in the overall complexity. One patient showed loss of a 25-s oscillation after surgery. We present a case where noise is misclassified as an oscillation, raising questions about the robustness of such analyses.
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http://dx.doi.org/10.14814/phy2.14423DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7202984PMC
May 2020

Influence of patient-specific rehearsal on operative metrics and technical success for endovascular aneurysm repair.

Minim Invasive Ther Allied Technol 2021 Aug 14;30(4):195-201. Epub 2020 Feb 14.

Department of Circulation and Medical Imaging, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.

Introduction: Patient-specific rehearsal (PsR) is a recent technology within virtual reality (VR) simulation that lets the operators train on patient-specific data in a simulated environment prior to the procedure. Endovascular aneurysm repair (EVAR) is a complex procedure where operative metrics and technical success might improve after PsR.

Material And Methods: We compared technical success and operative metrics (endovascular procedure time, contralateral gate cannulation time, fluoroscopy time, total radiation dose, number of angiograms and contrast medium use) between 30 patients, where the operators performed PsR (the PsR group), and 30 patients without PsR (the control group).

Results: The endovascular procedure time was significantly shorter in the PsR group than in the control group (median 44 versus 55 min, = .017). The other operative metrics were similar. Technical success rates were higher in the PsR group, 96.7% primary and assisted primary outcome versus 90.0% in the control group. The differences were not significant ( = .076).

Conclusions: PsR before EVAR reduced endovascular procedure time, and our results indicate that it might improve technical success, but further studies are needed to confirm those results.
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http://dx.doi.org/10.1080/13645706.2020.1727523DOI Listing
August 2021

Optimal timing of assessment tasks depending on experience level of surgical trainees.

Minim Invasive Ther Allied Technol 2020 Jun 8;29(3):161-169. Epub 2019 May 8.

Department of Gastrointestinal Surgery, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway.

Box trainers with motion analysis are important add-ons to surgical training and skills assessment outside the operating room, given that they exhibit construct validity. Four different tasks were tested for construct validity on a new laparoscopic box trainer with integrated motion analysis. Tracking data from the simulator were analyzed for eighteen parameters per task using an in-house software comparing participants with three different experience levels. In total, ten novices, 22 intermediates and 16 experts enrolled. No or limited significant differences were found for the and . For the task 12 parameters showed significant difference between novices and intermediates, 14 between novices and experts and one between intermediates and experts. For the task the corresponding results were one, 15 and six. The and task both showed construct validity for many of the parameters. While the task distinguished best between novices and the other two groups, the task distinguished best between experts and the other two groups. These results show the importance of the timing of an assessment task, and that an assessment task might have limited value if experience levels are not considered.
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http://dx.doi.org/10.1080/13645706.2019.1612441DOI Listing
June 2020

Team talk and team decision processes: a qualitative discourse analytical approach to 10 real-life medical emergency team encounters.

BMJ Open 2018 11 3;8(11):e023749. Epub 2018 Nov 3.

Department of Circulation and Medical Imaging, The Norwegian University of Science and Technology, Trondheim, Norway.

Objectives: Explore the function of three specific modes of talk (discourse types) in decision-making processes.

Design: Ten real-life admissions of patients with critical illness were audio/video recorded and transcribed. Activity-type analysis (a qualitative discourse analytical method) was applied.

Setting: Interdisciplinary emergency teams admitting patients with critical illness in a Norwegian university hospital emergency department (ED).

Participants: All emergency teams consisted of at least two internal medicine physicians, two ED nurses, one anaesthetist and one nurse anaesthetist. The number of healthcare professionals involved in each emergency team varied between 11 and 20, and some individuals were involved with more than one team.

Results: The three discourse types played significant roles in team decision-making processes when negotiating meaning. Online commentaries (ONC) and metacommentaries (MC) created progression while offline commentaries (OFC) temporarily placed decisions on hold. Both ONC and MC triggered action and distributed tasks, resources and responsibility in the team. OFC sought mutual understanding and created a broader base for decisions.

Conclusion: A discourse analytical perspective on team talk in medical emergencies illuminates both the dynamics and complexity of teamwork. Here, we draw attention to the way specific modes of talk function in negotiating mutual understanding and distributing tasks and responsibilities in non-algorithm-driven activities. The analysis uncovers a need for an enhanced focus on how language can trigger safe team practice and integrate this knowledge in teamwork training to improve communication skills in ad hoc emergency teams.
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http://dx.doi.org/10.1136/bmjopen-2018-023749DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231597PMC
November 2018

Bronchial microdialysis monitoring of inflammatory response in open abdominal aortic aneurysm repair; an observational study.

Physiol Rep 2017 Jul;5(14)

Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.

Aortic surgery results in ischemia-reperfusion injury that induces an inflammatory response and frequent complications. The magnitude of the inflammatory response in blood and bronchi may be associated with the risk of immediate complications. The purpose of the study was to evaluate bronchial microdialysis as a continuous monitoring of cytokines in bronchial epithelial lining fluid (ELF) and to determine whether bronchial ELF cytokine levels reflect the ischemia-reperfusion injury and risk for complications during open abdominal aortic aneurysm (AAA) repair. We measured cytokines in venous blood using microdialysis and in serum for comparison. Sixteen patients scheduled for elective open AAA repair were included in a prospective observational study. Microdialysis catheters were introduced into a bronchi and a cubital vein. Eighteen cytokines were measured using a Bio-Plex Magnetic Human Cytokine Panel. Samples were collected before and during cross-clamping of the aorta as well as from 0 to 60 min and from 60 to 120 min of reperfusion. The ELF levels of several cytokines changed significantly during reperfusion. In particular, IL-6 increased more than 10-fold and IL-13 more than 5-fold during ischemia and reperfusion. Also, the venous levels of several inflammatory and anti-inflammatory cytokines increased and exhibited their highest concentration during reperfusion. Both bronchial and venous cytokine levels correlated with duration of the procedure, intensive care days, and preoperative kidney disease. Three patients suffered organ failure as a direct consequence of the procedure, and in these patients the bronchial ELF concentrations of 17 of 18 cytokines differed significantly from patients without such complications. Bronchial microdialysis is suited for continuous monitoring of inflammation during open AAA repair. The bronchial ELF cytokine levels may be useful in predicting immediate complications such as organ failure in patients undergoing vascular surgery.
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http://dx.doi.org/10.14814/phy2.13348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5532484PMC
July 2017

Reduced reactive hyperemia may explain impaired flow-mediated dilation after on-pump cardiac surgery.

Physiol Rep 2017 May;5(10):e13274

Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.

In previous studies, Flow Mediated Dilation (FMD) was used to study the effect of cardiac surgery on endothelial function. This study investigated the effect of on-pump cardiac surgery on FMD and reactive hyperemia. The FMD-response and reactive hyperemia were measured in 25 patients the morning before- and the first morning after cardiac surgery. Brachial artery diameter and blood flow were measured with ultrasound at baseline before 5 min occlusion of the blood flow to the forearm, and continuously for 3 min after release of the occlusion. An exponential wash-out model was fitted to the blood flow over time. Nineteen patients remained for final data analysis. Data are mean ± SEM The FMD response was reduced after surgery from 3.3 ± 0.5% to 1.4 ± 0.6% ( = 0.02). Max blood flow after cuff release was reduced from 342 ± 30 mL preoperatively to 305 ± 30 mL postoperatively ( < 0.00) and fell toward baseline significantly quicker; preoperative half-life was 36 ± 2.4 sec. versus 29 ± 1.9 sec postoperatively ( < 0.00). Resting blood flow was reduced from 84 ± 9 mL/min to 66 ± 9 mL/min, ( < 0.00). Brachial artery baseline diameter was unaffected by coronary artery bypass surgery ( = 0.3). The observed reduction in brachial artery FMD after surgery, by previous authors taken to represent endothelial dysfunction, may at least partly be due to reduced hyperemic flow postoperatively. In studies where FMD is measured on multiple occasions, flow data should also be included. Reduced postoperative blood flow to the arm may indicate regional differences in vascular resistance after cardiac surgery.
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http://dx.doi.org/10.14814/phy2.13274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5449560PMC
May 2017

The coherence of macrocirculation, microcirculation, and tissue metabolic response during nontraumatic hemorrhagic shock in swine.

Physiol Rep 2017 Apr;5(7)

Department of Anesthesiology and Intensive Care Medicine, Trondheim University Hospital, Trondheim, Norway.

Hemorrhagic shock is clinically observed as changes in macrocirculatory indices, while its main pathological constituent is cellular asphyxia due to microcirculatory alterations. The coherence between macro- and microcirculatory changes in different shock states has been questioned. This also applies to the hemorrhagic shock. Most studies, as well as clinical situations, of hemorrhagic shock include a "second hit" by tissue trauma. It is therefore unclear to what extent the hemorrhage itself contributes to this lack of circulatory coherence. Nine pigs in general anesthesia were exposed to a controlled withdrawal of 50% of their blood volume over 30 min, and then retransfusion over 20 min after 70 min of hypovolemia. We collected macrocirculatory variables, microcirculatory blood flow measurement by the fluorescent microspheres technique, as well as global microcirculatory patency by calculation of Pv-aCO, and tissue metabolism measurement by the use of microdialysis. The hemorrhage led to anticipated changes in macrocirculatory variables with a coherent change in microcirculatory and metabolic variables. In the late hemorrhagic phase, the animals' variables generally improved, probably through recruitment of venous blood reservoirs. After retransfusion, all variables were normalized and remained same throughout the study period. We find in our nontraumatic model consistent coherence between changes in macrocirculatory indices, microcirculatory blood flow, and tissue metabolic response during hemorrhagic shock and retransfusion. This indicates that severe, but brief, hemorrhage with minimal tissue injury is in itself not sufficient to cause lack of coherence between macro- and microcirculation.
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http://dx.doi.org/10.14814/phy2.13216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5392510PMC
April 2017

Team talk and team activity in simulated medical emergencies: a discourse analytical approach.

Scand J Trauma Resusc Emerg Med 2016 Nov 14;24(1):135. Epub 2016 Nov 14.

Department of Language and Literature, Norwegian University of Science and Technology, Trondheim, Norway.

Background: Communication errors can reduce patient safety, especially in emergency situations that require rapid responses by experts in a number of medical specialties. Talking to each other is crucial for utilizing the collective expertise of the team. Here we explored the functions of "team talk" (talking between team members) with an emphasis on the talk-work relationship in interdisciplinary emergency teams.

Methods: Five interdisciplinary medical emergency teams were observed and videotaped during in situ simulations at an emergency department at a university hospital in Norway. Team talk and simultaneous actions were transcribed and analysed. We used qualitative discourse analysis to perform structural mapping of the team talk and to analyse the function of online commentaries (real-time observations and assessments of observations based on relevant cues in the clinical situation).

Results: Structural mapping revealed recurring and diverse patterns. Team expansion stood out as a critical phase in the teamwork. Online commentaries that occurred during the critical phase served several functions and demonstrated the inextricable interconnections between team talk and actions.

Discussion: Discourse analysis allowed us to capture the dynamics and complexity of team talk during a simulated emergency situation. Even though the team talk did not follow a predefined structure, the team members managed to manoeuvre safely within the complex situation. Our results support that online commentaries contributes to shared team situation awareness.

Conclusions: Discourse analysis reveals naturally occurring communication strategies that trigger actions relevant for safe practice and thus provides supplemental insights into what comprises "good" team communication in medical emergencies.
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http://dx.doi.org/10.1186/s13049-016-0325-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5109640PMC
November 2016

Minimally invasive beat-by-beat monitoring of cardiac power in normal hearts and during acute ventricular dysfunction.

Physiol Rep 2016 10;4(19)

Department of Anaesthesiology and Intensive care, Trondheim University Hospital, Trondheim, Norway Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway Circulation research group Trondheim (CIRCUT), Trondheim, Norway.

Cardiac power, the product of aortic flow and blood pressure, appears to be a fundamental cardiovascular parameter. The simplified version named cardiac power output (CPO), calculated as the product of cardiac output (CO) in L/min and mean arterial pressure (MAP) in mmHg divided by 451, has shown great ability to predict outcome in a broad spectrum of cardiac disease. Beat-by-beat evaluation of cardiac power (PWR) therefore appears to be a possibly valuable addition when monitoring circulatory unstable patients, providing parameters of overall cardiovascular function. We have developed a minimally invasive system for cardiac power measurement, and aimed in this study to compare this system to an invasive method (ttPWR). Seven male anesthetized farm pigs were included. A laptop with in-house software gathered audio from Doppler signals of aortic flow and blood pressure from the patient monitor to continuously calculate and display a minimally invasive cardiac power trace (uPWR). The time integral per cardiac cycle (uPWR-integral) represents cardiac work, and was compared to the invasive counterpart (ttPWR-integral). Signals were obtained at baseline, during mechanically manipulated preload and afterload, before and after induced global ischemic left ventricular dysfunction. We found that the uPWR-integral overestimated compared to the ttPWR-integral by about 10% (P < 0.001) in both normal hearts and during ventricular dysfunction. Bland-Altman limits of agreement were at +0.060 and -0.054 J, without increasing spread over the range. In conclusion we find that the minimally invasive system follows its invasive counterpart, and is ready for clinical research of cardiac power parameters.
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http://dx.doi.org/10.14814/phy2.12989DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5064141PMC
October 2016

Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers.

BMC Anesthesiol 2016 06 30;16(1):31. Epub 2016 Jun 30.

Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway.

Background: Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure. We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure ventilation (NPPV).

Methods: Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, -20, -40, -60 and -80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with LBNP-levels.

Results: Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous breathing increasing 103 % (p < 0.001) from baseline to LBNP -80 mmHg. Respiratory variation in pulse pressure was the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP -80 mmHg. The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to LBNP -80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV.

Conclusions: Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly better than equivalent flow parameters, and far better than equivalent pressure parameters.
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http://dx.doi.org/10.1186/s12871-016-0195-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4929737PMC
June 2016

The Precision of Pulmonary Artery Catheter Bolus Thermodilution Cardiac Output Measurements Varies With the Clinical Situation.

J Cardiothorac Vasc Anesth 2015 Aug 12;29(4):881-8. Epub 2014 Dec 12.

Department of Anesthesiology and Intensive Care, St. Olav University Hospital, Trondheim, Norway; Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.

Objective: To investigate the effects of ventilatory mode, injectate temperature, and clinical situation on the precision of cardiac output measurements.

Design: Randomized, prospective observational study.

Setting: Single university hospital.

Participants: Forty patients undergoing planned cardiac surgery, receiving a pulmonary artery catheter according to institutional routine.

Interventions: Cardiac output was measured at 4 predefined time points during the perioperative patient course, twice during controlled and twice during spontaneous ventilation, using 2 blocks of 8 measurement replications with cold and tepid injectate in random order.

Measurements And Main Results: The data were analyzed using a hierarchical linear mixed model. Clinical precision was determined as half the width of the 95% confidence interval for the underlying true value. The single-measurement precision measured in 2 different clinical situations for each temperature/ventilation combination was 8% to 10%, 11% to 13%, 13% to 15%, and 23% to 24% in controlled ventilation with cold injectate, controlled ventilation with tepid injectate, spontaneous breathing with cold injectate, and spontaneous breathing with tepid injectate, respectively. Tables are provided for the number of replications needed to achieve a certain precision and for how to identify significant changes in cardiac output.

Conclusions: Clinical precision of cardiac output measurements is reduced significantly during spontaneous relative to controlled ventilation. The differences in precision between repeated measurement series within the temperature/ventilation combinations indicate influence of other situation-specific factors not related to ventilatory mode. Compared with tepid injectate in patients breathing spontaneously, the precision is 3-fold better with cold injectate and controlled ventilation.
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http://dx.doi.org/10.1053/j.jvca.2014.12.016DOI Listing
August 2015

Cardiac function assessed by exercise echocardiography on the first morning after coronary artery bypass grafting.

Clin Physiol Funct Imaging 2016 Jul 23;36(4):274-80. Epub 2014 Dec 23.

Department of Cardiology, St. Olav's Hospital, Trondheim University Hospital, Trondheim, Norway.

Cardiac surgery patients are urged to resume light physical activity on the first postoperative day, even if cardiac function may not have recovered fully after the operation. To elucidate the postoperative recovery process, we examined cardiac surgery patients with exercise echocardiography before and on the first day after the operation. Patients undergoing on-pump coronary artery bypass grafting were examined with echocardiography during semirecumbent cycle exercise. Patients exercised for five minutes at 10 W intensity and five minutes at 30 W intensity in bed with the upper body supported to approximately 30°. Fourteen patients were studied. Mitral annulus excursion and pulsed wave Doppler from the left ventricular outflow tract indicated postoperatively reduced cardiac stroke volume. Early diastolic tissue velocities of the mitral annulus were reduced, and early trans-mitral flow velocity was increased. The ratio between early mitral flow velocity and early diastolic mitral tissue velocity was increased postoperatively, indicating impaired left ventricular relaxation and increased left atrial pressure. Postoperative systolic mitral annulus tissue velocities were similar to preoperative velocities, indicating maintained systolic function. Postoperative exercise was associated with improvements in myocardial function indices and cardiac stroke volume similar to preoperative improvements. There were no signs of further deterioration in myocardial function during 30 W exercise. In summary, reduced left ventricular diastolic function after surgery resulted in reduced cardiac stroke volume, increased left atrial pressure and a higher rate of perceived exertion on the first postoperative day.
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http://dx.doi.org/10.1111/cpf.12224DOI Listing
July 2016

Elevated arterial lactate concentrations early after coronary artery bypass grafting are associated with increased anaerobic metabolism in skeletal muscle.

J Cardiothorac Vasc Anesth 2015 Apr 17;29(2):367-73. Epub 2014 Dec 17.

Department of Cardiothoracic Anesthesiology and Intensive Care, St. Olav's Hospital, Trondheim, Norway.

Objective: To assess the effect of coronary artery bypass grafting with cardiopulmonary bypass on muscle perfusion, oxygen extraction, and lactate release during postoperative rest and exercise.

Design: Prospective observational study.

Setting: University hospital.

Participants: Patients undergoing planned coronary artery bypass grafting.

Intervention: Knee-extensor exercise before and after coronary artery bypass grafting.

Measurements And Main Results: Femoral artery blood flow was measured with ultrasound. Femoral vein blood and arterial blood were sampled at rest and during light exercise and were analyzed for hemoglobin, lactate, oxygen saturation, and oxygen partial pressure. Fourteen patients were tested before and after surgery. The arterial lactate concentrations were increased after surgery, both at rest and during light exercise. Resting arterial lactate increased from 0.65 (0.5-0.8) to 1.0 (0.9-1.3) mmol/L (p=0.01) (median and interquartile range). Furthermore, lactate was released from the leg even during postoperative rest, and the release of lactate was increased during postoperative exercise. There were no significant differences between the preoperative and postoperative femoral artery blood flow. Femoral vein oxygen partial pressure was reduced significantly after surgery, indicating reduced muscle cell oxygen partial pressure.

Conclusions: The patients had elevated anaerobic metabolism in skeletal muscle after surgery to compensate for anemia. Lactate was released from the leg into the general circulation during postoperative rest and exercise. The postoperatively reduced hemoglobin concentration of 11.4 mg/dL (10.6-12.3) resulted in increased anaerobic metabolism and release of lactate from skeletal muscle. The authors concluded that coronary artery bypass grafting patients are susceptible to anaerobic metabolism even with maintained peripheral blood flow.
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http://dx.doi.org/10.1053/j.jvca.2014.08.001DOI Listing
April 2015

Team competence among nurses in an intensive care unit: the feasibility of in situ simulation and assessing non-technical skills.

Intensive Crit Care Nurs 2014 Dec 21;30(6):312-7. Epub 2014 Jul 21.

Norwegian University of Science and Technology, Department of Circulation and Medical Imaging, Trondheim, Norway; St. Olavs Hospital, Trondheim University Hospital, Department of Anesthesiology and Intensive Care, Trondheim, Norway.

Objectives: Nursing competence affects quality of care in intensive care units (ICUs). Team competence is particularly important for preventing errors. This paper focuses on the feasibility of using an in situ simulation model to explore team competence in the ICU, and on using parts of the Anaesthetists' Non-Technical Skills (ANTS) taxonomy for assessing Non-Technical Skills (NTS) in nursing teams.

Methodology/design: Seventy-two nurses were randomised into two groups and introduced to a new guideline via either lecture-based or simulation-based teaching. A preprogrammed patient simulator and a video camera were installed inside the ICU, and a scenario was enacted to simulate the admission of a patient with septic shock. All available facilities in the ICU were used. Two blinded raters evaluated "Team Working" and "Situation Awareness" via video recordings using the ANTS taxonomy.

Results: Due to high activity in the ICU, 54 nurses completed the in situ simulation. Assessments of the video recordings revealed moderate agreement between the two raters. Observations revealed issues deviating from expected standards of competence.

Conclusion: In situ simulation may be feasible for assessing competence in ICUs. The ANTS appears to be a promising foundation for developing a team assessment tool for ICUs.
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http://dx.doi.org/10.1016/j.iccn.2014.06.007DOI Listing
December 2014

Animal study assessing safety of an acoustic coupling fluid that holds the potential to avoid surgically induced artifacts in 3D ultrasound guided operations.

BMC Med Imaging 2014 Mar 25;14:11. Epub 2014 Mar 25.

Department of Neurosurgery, St,Olavs University Hospital, Trondheim, N-7006, Norway.

Background: Use of ultrasound in brain tumor surgery is common. The difference in attenuation between brain and isotonic saline may cause artifacts that degrade the ultrasound images, potentially affecting resection grades and safety. Our research group has developed an acoustic coupling fluid that attenuates ultrasound energy like the normal brain. We aimed to test in animals if the newly developed acoustic coupling fluid may have harmful effects.

Methods: Eight rats were included for intraparenchymal injection into the brain, and if no adverse reactions were detected, 6 pigs were to be included with injection of the coupling fluid into the subarachnoid space. Animal behavior, EEG registrations, histopathology and immunohistochemistry were used in assessment.

Results: In total, 14 animals were included, 8 rats and 6 pigs. We did not detect any clinical adverse effects, seizure activity on EEG or histopathological signs of tissue damage.

Conclusion: The novel acoustic coupling fluid intended for brain tumor surgery appears safe in rats and pigs under the tested circumstances.
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http://dx.doi.org/10.1186/1471-2342-14-11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3977940PMC
March 2014

Cardiac power integral: a new method for monitoring cardiovascular performance.

Physiol Rep 2013 Nov 19;1(6):e00159. Epub 2013 Nov 19.

Department of Thoracic Anesthesiology and Intensive Care, Trondheim University Hospital Trondheim, Norway.

Cardiac power (PWR) is the continuous product of flow and pressure in the proximal aorta. Our aim was to validate the PWR integral as a marker of left ventricular energy transfer to the aorta, by comparing it to stroke work (SW) under multiple different loading and contractility conditions in subjects without obstructions in the left ventricular outflow tract. Six pigs were under general anesthesia equipped with transit time flow probes on their proximal aortas and Millar micromanometer catheters in their descending aortas to measure PWR, and Leycom conductance catheters in their left ventricles to measure SW. The PWR integral was calculated as the time integral of PWR per cardiac cycle. SW was calculated as the area encompassed by the pressure-volume loop (PV loop). The relationship between the PWR integral and SW was tested during extensive mechanical and pharmacological interventions that affected the loading conditions and myocardial contractility. The PWR integral displayed a strong correlation with SW in all pigs (R (2) > 0.95, P < 0.05) under all conditions, using a linear model. Regression analysis and Bland Altman plots also demonstrated a stable relationship. A mixed linear analysis indicated that the slope of the SW-to-PWR-integral relationship was similar among all six animals, whereas loading and contractility conditions tended to affect the slope. The PWR integral followed SW and appeared to be a promising parameter for monitoring the energy transferred from the left ventricle to the aorta. This conclusion motivates further studies to determine whether the PWR integral can be evaluated using less invasive methods, such as echocardiography combined with a radial artery catheter.
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http://dx.doi.org/10.1002/phy2.159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3871473PMC
November 2013

Blood glucose control using a novel continuous blood glucose monitor and repetitive intravenous insulin boluses: exploiting natural insulin pulsatility as a principle for a future artificial pancreas.

Int J Endocrinol 2013 27;2013:245152. Epub 2013 Nov 27.

Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, MTFS, Postbox 8905, 7491 Trondheim, Norway ; Department of Anesthesiology and Intensive Care Medicine, Trondheim University Hospital, Postbox 3250 Sluppen, 7006 Trondheim, Norway.

The aim of this study was to construct a glucose regulatory algorithm by employing the natural pulsatile pattern of insulin secretion and the oscillatory pattern of resting blood glucose levels and further to regulate the blood glucose level in diabetic pigs by this method. We developed a control algorithm based on repetitive intravenous bolus injections of insulin and combined this with an intravascular blood glucose monitor. Four anesthetized pigs were used in the study. The animals developed a mildly diabetic state from streptozotocin pretreatment. They were steadily brought within the blood glucose target range of 4.5-6.0 mmol/L in 21 to 121 min and kept within that range for 128 to 238 min (hypoglycemic values varied from 2.9 to 51.1 min). The study confirmed our hypotheses regarding the feasibility of this new principle for blood glucose control, and the algorithm was constantly improved during the study to produce the best results in the last animals. The main obstacles were the drift of the IvS-1 sensor and problems with the calibration procedure, which calls for an improvement in the sensor stability before this method can be applied fully in new studies in animals and humans.
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http://dx.doi.org/10.1155/2013/245152DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3863478PMC
December 2013

Comparison of arterial and mixed venous blood glucose levels in hemodynamically unstable pigs: implications for location of a continuous glucose sensor.

Acta Diabetol 2012 Dec 17;49(6):489-91. Epub 2012 Apr 17.

Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.

One of several unsolved challenges in the construction of an artificial endocrine pancreas (a system for automatically adjusting the blood glucose level) is the positioning of the glucose sensor. We believe the best positioning to be either intraarterial or in a central vein. It is therefore important to know whether the glucose content in these blood locations is the same. We conducted a post hoc analysis of previously collected data from pigs exposed to gross inflammatory and circulatory stress. Paired arterial and mixed venous glucose values were compared with a mixed effects model. We found the blood glucose values from the arterial and mixed venous blood to be the same.
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http://dx.doi.org/10.1007/s00592-012-0394-1DOI Listing
December 2012

Three-dimensional electromagnetic navigation vs. fluoroscopy for endovascular aneurysm repair: a prospective feasibility study in patients.

J Endovasc Ther 2012 Feb;19(1):70-8

Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.

Purpose: To evaluate the in vivo feasibility of a 3-dimensional (3D) electromagnetic (EM) navigation system with electromagnetically-tracked catheters in endovascular aneurysm repair (EVAR).

Methods: The pilot study included 17 patients undergoing EVAR with a bifurcated stent-graft. Ten patients were assigned to the control group, in which a standard EVAR procedure was used. The remaining 7 patients (intervention group) underwent an EVAR procedure during which a cone-beam computed tomography image was acquired after implantation of the main stent-graft. The 3D image was presented on the navigation screen. From the contralateral side, the tip of an electromagnetically-tracked catheter was visualized in the 3D image and positioned in front of the contralateral cuff in the main stent-graft. A guidewire was inserted through the catheter and blindly placed into the stent-graft. The placement of the guidewire was verified by fluoroscopy before the catheter was pushed over the guidewire. If the guidewire was incorrectly placed outside the stent-graft, the procedure was repeated. Successful placement of the guidewire had to be achieved within a 15-minute time limit.

Results: Within 15 minutes, the guidewire was placed correctly inside the stent-graft in 6 of 7 patients in the intervention group and in 8 of 10 patients in the control group. In the intervention group, fewer attempts were needed to insert the guidewire correctly.

Conclusion: A 3D EM navigation system, used in conjunction with fluoroscopy and angiography, has the potential to provide more spatial information and reduce the use of radiation and contrast during endovascular interventions. This pilot study showed that 3D EM navigation is feasible in patients undergoing EVAR. However, a larger study must be performed to determine if 3D EM navigation is better than the existing practice for these patients.
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http://dx.doi.org/10.1583/11-3557.1DOI Listing
February 2012

Pharmacology of intravenous insulin administration: implications for future closed-loop glycemic control by the intravenous/intravenous route.

Diabetes Technol Ther 2012 Jan 13;14(1):23-9. Epub 2011 Jul 13.

Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.

Background: Our group is attempting to construct an artificial pancreas based on intravenous glucose monitoring and intravenous insulin delivery. To do so, the pharmacology of intravenous insulin administration must be studied. We used a pig model to determine the inherent lag time in the insulin/blood glucose system. The goal was to suggest a method that reduces the blood glucose level in a rapid and yet predictable manner.

Methods: Six pigs received continuous intravenous insulin infusions at 0.04, 0.08, or 0.4 IU/kg/h for 60 min. Two pigs received short-term intravenous infusions at 0.4 IU/kg/h for 2 min, repeated five times at 60-min intervals. Four animals received five intravenous insulin bolus injections at 60-min intervals, two at 0.01 IU/kg and two 0.02 IU/kg, with a final dose of 0.04 IU/kg. The blood glucose level was measured every 1-5 min.

Results: A high rate of intravenous insulin infusion led to rapid declines in blood glucose levels. The same rapid decline was achieved when the infusion was halted after 2 min. Using the latter method and with intravenous insulin boluses, blood glucose levels started to rise again after approximately 15-20 min. Insulin boluses led to a first detectable decrease in blood glucose level after 2-6 min and to a maximum rate of decrease shortly thereafter.

Conclusions: We found that intravenous bolus injections of insulin lowered blood glucose levels rapidly and predictably. Repetitive small intravenous insulin boluses together with an accurate and fast-responding intravascular continuous glucose monitor should be studied as a method of closed-loop glycemic control.
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http://dx.doi.org/10.1089/dia.2011.0118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3249623PMC
January 2012

Three-dimensional endovascular navigation with electromagnetic tracking: ex vivo and in vivo accuracy.

J Endovasc Ther 2011 Apr;18(2):230-40

Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway.

Purpose: To evaluate the accuracy of a 3-dimensional (3D) navigation system using electromagnetically tracked tools to explore its potential in patients.

Methods: The 3D navigation accuracy was quantified on a phantom and in a porcine model using the same setup and vascular interventional suite. A box-shaped phantom with 16 markers was scanned in 5 different positions using computed tomography (CT). The 3D navigation system registered each CT volume in the magnetic field. A tracked needle was pointed at the physical markers, and the spatial distances between the tracked needle positions and the markers were calculated. Contrast-enhanced CT images were acquired from 6 swine. The 3D navigation system registered each CT volume in the magnetic field. An electromagnetically tracked guidewire and catheter were visualized in the 3D image and navigated to 4 specified targets. At each target, the spatial distance between the tracked guidewire tip position and the actual position, verified by a CT control, was calculated.

Results: The mean accuracy on the phantom was 1.28±0.53 mm, and 90% of the measured distances were ≤1.90 mm. The mean accuracy in swine was 4.18±1.76 mm, and 90% of the measured distances were ≤5.73 mm.

Conclusion: This 3D navigation system demonstrates good ex vivo accuracy and is sufficiently accurate in vivo to explore its potential for improved endovascular navigation.
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http://dx.doi.org/10.1583/10-3301.1DOI Listing
April 2011

Continuous measurement of blood glucose: validation of a new intravascular sensor.

Anesthesiology 2011 Jan;114(1):120-5

Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway.

Background: Tight blood glucose control is used extensively in perioperative and critically ill patients. Several studies, however, have shown contradictory effects on patient outcomes. A major problem of these studies has been inadequate control of the prime variable, blood glucose. This paper describes the validation of a new intravascular continuous blood glucose sensor.

Methods: The glucose sensor was placed in the superior caval vein of seven anesthetized pigs. Sensor readings were compared with arterial blood gas readings. Fluctuations in blood glucose were created using intravenous glucose and insulin. A total of 807 paired sensor and blood gas readings were obtained.

Results: The sensor was tested with a range of blood glucose values (0.63-15.75 mM [mean bias, 0.0131 mM]). Analysis using Bland-Altman plots yielded 95% limits of agreement at -0.908 and 0.934 mM. There were 121 paired measurements with a mean value below 2.2 mM, yielding 95% limits of agreement at -0.553 and 0.466 mM.

Conclusions: The performance of the sensor was in agreement with blood gas measurements in a wide range of glucose values. For the clinician, it is noteworthy that performance was equally good in the hypoglycemic area.
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http://dx.doi.org/10.1097/ALN.0b013e3181ff4187DOI Listing
January 2011

Bronchial microdialysis of cytokines in the epithelial lining fluid in experimental intestinal ischemia and reperfusion before onset of manifest lung injury.

Shock 2010 Nov;34(5):517-24

Department of Anesthesia and Intensive Care, St Olavs Hospital, Trondheim, Norway.

Today, there is no continuous monitoring of the bronchial epithelial lining fluid. This study used microdialysis as a method of continuous monitoring of early lung cytokine response secondary to intestinal ischemia-reperfusion in pigs. The authors aimed to examine bronchial microdialysis for continuous monitoring of IL-1β, TNF-α, IL-8, and fluorescein isothiocyanate Dextran 4,000 Da (FD-4). The superior mesenteric artery was cross-clamped for 120 min followed by 240 min of reperfusion (ischemia group, n = 8). Four sham-operated pigs served as controls. The pigs were anesthetized and normoventilated (peak inspiratory pressure, <20 cm H2O; positive end-expiratory pressure, 7 cm H2O). Samples from bronchial and luminal intestinal and arterial microdialysis catheters (flow-rate of 1 μL/min) were collected during reperfusion in 60-min fractions. Samples were analyzed for TNF-α, IL-1β, IL-8, and FD-4. Data are presented as median (interquartile range). A lung biopsy was collected at the end of the experiment. During reperfusion, there was an increase in bronchial concentrations of both IL-8 (3.70 [1.47-8.93] ng/mL per h vs. controls, 0.61 [0.47-0.91] ng/mL per h; P < 0.001) and IL-1β (0.32 [0.05-0.56] ng/mL per h vs. controls, 0.07 [0.04-0.10] ng/mL per h; P = 0.008). In the intestinal lumen, IL-8 was increased in the ischemia group (6.33 [3.13-9.23] ng/mL per h vs. controls, 0.89 [0.21-1.86] ng/mL per h; P < 0.001). The FD-4 did not differ between groups. Pulmonary vascular resistance and pulmonary shunt increased versus controls. During reperfusion, PaO2/FiO2 ratio decreased in the ischemia group. Histology was normal in both groups. Bronchial microdialysis detects altered levels of cytokines in the epithelial lining fluid and can be used for continuous monitoring of the immediate local lung cytokine response secondary to intestinal ischemia-reperfusion.
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http://dx.doi.org/10.1097/SHK.0b013e3181dfc430DOI Listing
November 2010

[How to secure free airway?].

Tidsskr Nor Laegeforen 2010 Mar;130(5):507-10

Anestesiavdelingen, Oslo universitetssykehus, Ullevål.

Background: To secure the airway has the highest priority when handling critically ill and injured patients. The aim of this article is to present simple and new devices and techniques to secure the airway.

Material And Methods: The paper is based on international algorithms for optimal treatment of patients with acute airway problems, and the authors' experience from clinical work and organizing of courses.

Results: Unconscious patients have obstructed airways because the tongue slides back and blocks the airway. This can be prevented by lifting the jaw, possibly supplemented by insertion of an oropharyngeal airway. When these active techniques are not used, patients must be placed in the semi-prone position and air passage checked. The non-breathing patient must be ventilated with simple devices: mouth-to-mouth, pocket-mask or face-mask and bag. Endotracheal intubation is difficult and supraglottic devices are easier and safer to handle. Anaesthetists may use special equipment when securing of airway is particularly difficult. Hospitals routinely intubate with bronchoscopy when presented with patients who breathe spontaneously and for whom airway is expected to have very difficult access. Direct transtracheal access can be obtained by emergency tracheotomy or with various puncturing techniques.

Interpretation: In the unconscious patient, it is of vital importance to maintain a secure airway with simple devices. Hypoxia subsequent to obstructed airways in unconscious patients will become life-threatening, and may cause cerebral ischemia and cardiac arrest within 5-6 minutes. All doctors should be able to ventilate patients with face-mask and bag-valve device. Intubation and tracheotomy should only be performed by trained personnel.
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http://dx.doi.org/10.4045/tidsskr.08.0548DOI Listing
March 2010

Continuous monitoring of the bronchial epithelial lining fluid by microdialysis.

Respir Res 2007 Nov 1;8:78. Epub 2007 Nov 1.

Department of Anesthesia and Intensive Care, St, Olavs Hospital, Trondheim, Norway.

Background: Contents of the epithelial lining fluid (ELF) of the bronchi are of central interest in lung diseases, acute lung injury and pharmacology. The most commonly used technique broncheoalveolar lavage is invasive and may cause lung injury. Microdialysis (MD) is a method for continuous sampling of extracellular molecules in the immediate surroundings of the catheter. Urea is used as an endogenous marker of dilution in samples collected from the ELF. The aim of this study was to evaluate bronchial MD as a continuous monitor of the ELF.

Methods: Microdialysis catheters were introduced into the right main stem bronchus and into the right subclavian artery of five anesthetized and normoventilated pigs. The flowrate was 2 mul/min and the sampling interval was 60 minutes. Lactate and fluorescein-isothiocyanate-dextran 4 kDa (FD-4) infusions were performed to obtain two levels of steady-state concentrations in blood. Accuracy was defined as [bronchial-MD] divided by [arterial-MD] in percent. Data presented as mean +/- 95 percent confidence interval.

Results: The accuracy of bronchial MD was calculated with and without correction by the arteriobronchial urea gradient. The arteriobronchial lactate gradient was 1.2 +/- 0.1 and FD-4 gradient was 4.0 +/- 1.2. Accuracy of bronchial MD with a continuous lactate infusion was mean 25.5% (range 5.7-59.6%) with a coefficient of variation (CV) of 62.6%. With correction by the arteriobronchial urea gradient accuracy was mean 79.0% (57.3-108.1%) with a CV of 17.0%.

Conclusion: Urea as a marker of catheter functioning enhances bronchial MD and makes it useful for monitoring substantial changes in the composition of the ELF.
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http://dx.doi.org/10.1186/1465-9921-8-78DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2169243PMC
November 2007

Post-ischaemic restituted intestinal mucosa is more resistant to further ischaemia than normal mucosa in the pig.

Scand J Clin Lab Invest 2008 21;68(2):106-16. Epub 2007 Nov 21.

Department of Surgery, St. Olav University Hospital, NO-7006 Trondheim, Norway.

Objective: Ischaemic preconditioning may protect the intestine from subsequent prolonged ischaemia. This study evaluates whether a much longer initial ischaemia, encountered clinically, may modify intestinal resistance to further ischaemia in a pig model.

Material And Methods: After cross-clamping of the superior mesenteric artery for 1 h, the intestine was either reperfused for 8 h or a second cross-clamping for 1 h was performed at 4 h of reperfusion. Based on microarray analysis of intestinal samples at 1, 4 and 8 h of reperfusion, mRNA of selected genes was measured with QRT-PCR.

Results: The first ischaemic period caused exfoliation of surface epithelial cells from the basement membrane comprising about 90 % of the villi tips, a marked increase in permeability and depletion of ATP. The second ischaemic challenge caused about 30 % less denudation of the basement membrane (p = 0.008), no increase in permeability (p = 0.008) and less depletion of ATP (p = 0.039). mRNAs for superoxide dismutase 2, heat shock proteins and signal transducer and activator of transcription 3, which may protect against ischaemia/reperfusion injury, were up-regulated throughout the reperfusion period. mRNAs for matrix metalloproteinase 1, connexin 43 and peripheral myelin 22, which may be associated with cell migration or tight junctions, showed a particular up-regulation at 4 h of reperfusion.

Conclusion: One hour of initial ischaemia followed by 4 h of reperfusion is associated with increased intestinal resistance to further ischaemia. The differential regulation of genes identified in this study provides working hypotheses for mechanisms behind this observation.
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http://dx.doi.org/10.1080/00365510701534833DOI Listing
July 2008

Gut luminal lactate measured by microdialysis mirrors permeability of the intestinal mucosa after ischemia.

Shock 2008 Feb;29(2):245-51

Department of Anesthesiology and Intensive Care, St. Olav University Hospital, Trondheim, Norway.

The aim of the present study was to investigate the influence of a prolonged initial intestinal ischemic insult on transmucosal permeability after a subsequent ischemic event and whether microdialysis of biomarkers released to the gut lumen is able to reflect changes in intestinal permeability. The superior mesenteric artery was cross-clamped for 60 min followed by 4 h of reperfusion in 16 pigs. Nine pigs had a second cross-clamp of 60 min and 3 h of reperfusion, whereas seven pigs were observed for a further 4 h of reperfusion. Intestinal mucosal integrity was assessed by permeability of C-polyethylene glycol (PEG-4000) over the gut mucosa, luminal microdialysis of lactate, glucose and glycerol, and tonometry. During reperfusion, the PEG-4000 amount in venous blood was two times higher after the first than after the second ischemia (area under the curve, 44,780 [13,441-82,723] vs. 22,298 (12,213-49,698] counts min mL(-1), P=0.026 [mean {range}]). There was less lactate detected in the gut lumen after the second ischemia compared with the first (area under the curve, 797 [412-1,700] vs. 1,151 [880-1,969] mmol min L(-1), P=0.02) and a lower maximum concentration (4.8 [2.7-9.4] vs. 8.5 [5.0-14.9] mM, P=0.01). The same pattern was also seen for luminal glycerol and glucose. During the second ischemia, the intestinal mucosal/arterial CO2 gap was identical to the level during the first ischemic episode. A prolonged ischemic insult of the intestine confers protection, for reduced hyperpermeability against further ischemia. Microdialysis of biomarkers mirrors permeability changes associated with this type of protection. Lactate reflects permeability across the intestinal mucosa more precisely than glycerol.
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http://dx.doi.org/10.1097/SHK.0b013e3180cab3ceDOI Listing
February 2008

[A 58.year old woman with short bowel syndrome and nutrition failure].

Tidsskr Nor Laegeforen 2007 May;127(10):1370-1

Klinikk for anestesi og akuttmedisin, St. Olavs Hospital, 7006 Trondheim.

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May 2007

Gut luminal microdialysis of glycerol as a marker of intestinal ischemic injury and recovery.

Crit Care Med 2005 Oct;33(10):2278-85

Department of Anesthesiology and Intensive Care, St. Olav University Hospital, Norwegian University of Science and Technology, N-7006 Trondheim, Norway.

Objective: To evaluate microdialysis as a method to assess different degrees of intestinal damage and recovery during ischemia and reperfusion; to evaluate information obtained from microdialysis catheters in the peritoneum, the gut wall, and the gut lumen.

Design: Randomized, controlled animal experiment.

Setting: University laboratory animal center.

Subjects: Twenty-seven domestic pigs.

Interventions: The superior mesenteric artery was cross-clamped for 60 mins (n = 14) or 120 mins (n = 10) followed by 2 or 4 hrs of reperfusion. Three pigs served as controls.

Measurements And Main Results: Intestinal mucosal integrity was assessed by morphometry, adenosine triphosphate in the gut wall, and permeability of C-polyethylene glycol. Lactate, glycerol, pyruvate, and glucose were measured by microdialysis. Changes in adenosine triphosphate, permeability, or lactate did not correlate to different extents of intestinal damage caused by 60 or 120 mins of ischemia. During the reperfusion period, pigs with 60 mins of intestinal ischemia showed a faster recovery of these variables than pigs with 120 mins of intestinal ischemia. Glycerol increased with increasing duration of the ischemic insult. After 60 mins of intestinal ischemia, glycerol in the gut lumen decreased toward baseline but remained high after 120 mins of intestinal ischemia. There was a good correlation between gut luminal glycerol and recovery of mucosal damage throughout the reperfusion period. In the peritoneal cavity, both glycerol and lactate decreased to baseline relatively shortly after onset of reperfusion independent of the duration of intestinal ischemia.

Conclusions: Microdialysis of glycerol provides information about the extent and severity of intestinal damage after ischemia and about the ensuing recovery. The gut lumen is to be preferred as a site for placement of microdialysis catheters.
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http://dx.doi.org/10.1097/01.ccm.0000178187.84732.6cDOI Listing
October 2005
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