Ketil Grong

Rewarming from accidental hypothermia by extracorporeal circulation. A retrospective study

OBJECTIVE Twenty-six patients with accidental hypothermia combined with circulatory arrest or severe circulatory failure were rewarmed to normothermia by use of extracorporeal circulation (ECC). The aim of the present study was to evaluate our results. PATIENTS AND METHODS The treatment of six female and 20 male patients (median age: 26.7 years; range 1.9--76.3 years) rewarmed in the period 1987--2000 was evaluated retrospectively. Hypothermia was related to immersion/submersion in cold water (n=17), avalanche (n=1) or prolonged exposure to cold surroundings (n=8). Prior to admission, the trachea was intubated and cardiopulmonary resuscitation (CPR) initiated in all patients with cardiorespiratory arrest (n=22), whereas in those with respiration/circulation (n=4) only oxygen therapy via a face mask was given. RESULTS Nineteen of the 26 patients were weaned off ECC whereas seven died because of refractory respiratory and/or cardiac failure. Eight of the 19 successfully weaned patients were discharged from hospital after a median of 10 days. One patient died 3 days after circulatory arrest (complete atrioventricular block) resulting in severe cerebral injury. The remaining ten patients died following 1--2 days due to severe hypoxic brain injury (n=5), cerebral bleeding (n=1) or irreversible cardiopulmonary insufficiency (n=4). Based on the reports from the site of accident, two groups of patients were identified: the asphyxia group (n=15) (submersions (n=14); avalanche accident (n=1)) and the non-asphyxia group (n=11) (patients immersed or exposed to cold environment). Seven intact survivors discharged from hospital belonged to the non-asphyxia group whereas one with a severe neurological deficit was identified within the asphyxia group. CONCLUSION Patients with non-asphyxiated deep accidental hypothermia have a reasonable prognosis and should be rewarmed before further therapeutic decisions are made. In contrast, drowned patients with secondary hypothermia have a very poor prognosis. The treatment protocol under such conditions should be the subject for further discussion.

Tissue Reaction to Polypropylene Mesh: A Study of Oedema, Blood Flow, and Inflammation in the Abdominal Wall

The purpose of the present work was to study the tissue reaction to polypropylene mesh (Marlex) implanted in three different layers of the abdominal wall, comparable to common clinical practices. The reaction to mesh was compared in terms of tissue oedema, blood flow, and histological appearance in rats. When mesh was placed between muscle layers, blood flow in the abdominal wall was high during the first 4 days after implantation but similar to flow in nonoperated rats 14 and 140 days after implantation. When mesh was placed under skin or on the peritoneum, there was no hyperaemia early after implantation, and flow rate was clearly lower than in non-operated controls 140 days after implantation. The operative procedure produced increased tissue water content, declining from the 1st to the 14th day after operation. Mesh induced additional oedema in adjacent muscle tissue irrespective of localization of the implant (p less than 0.01, vs. sham). Except when separated by peritoneum, mesh caused hyperaemia in muscle tissue in direct contact with mesh the 1st and the 4th day after implantation. After 14 and 140 days no mesh-induced hyperaemia was present. The inflammatory response to mesh was similar in the peritoneum and between muscles, less pronounced in the subcutis. It was characterized by the accumulation of macrophages and the formation of inflammatory granulation tissue in the subacute phase, later followed by the formation of fibrous tissue around mesh fibres. This study suggests that mesh implants should be placed in apposition to muscles in order to obtain well-vascularized healing.

Effects of prolonged increased intra-abdominal pressure on gastrointestinal blood flow in pigs

BackgroundThe aim of the study was to investigate the effects of prolonged intra-abdominal pressure on systemic hemodynamics and gastrointestinal blood circulation.MethodsThe intra-abdominal pressure in anesthetized pigs was elevated to 20 mmHg (7 animals), 30 mmHg (7 animals), and 40 mmHg (4 animals), respectively. These pressures were maintained for 3 h by intra-abdominal infusion of Ringer’s solution. A control group of seven animals had normal intra-abdominal pressure (IAP). Transit time flowmetry and colored microspheres were used to measure blood flow.ResultsAn IAP of 20 mmHg did not cause significant changes in systemic hemodynamics or tissue blood flow. An IAP of 30 mmHg caused reduced blood flow in the portal vein, gastric mucosa, small bowel mucosa, pancreas, spleen, and liver. Serum lactate increased in animals with an IAP of 30 mmHg, but microscopy did not disclose mucosal damage in the stomach or small bowel. An IAP of 40 mmHg was followed by severe circulatory changes.ConclusionsProlonged IAP at 20 mmHg did not cause changes in general hemodynamics or gastrointestinal blood flow. Prolonged IAP at 30 mmHg caused reduced portal venous blood flow and reduced tissue flow in various abdominal organs, but no mucosal injury. A prolonged IAP of 40 mmHg represented a dangerous trauma to the animals.

Distribution of cardiac output during pentobarbital versus midazolam/fentanyl/fluanisone anaesthesia in the rat.

Differences in effects on central haemodynamics, organ blood flow, and serum corticosterone were studied in 11 rats anaesthetized with midazolam/fentanyl/fluanisone (MFF) and 11 other rats anaesthetized with sodium pentobarbital. Compared with pentobarbital, MFF reduced aortic blood pressure by 25%, increased heart rate by 20%, and increased cardiac output by 80%. Unlike most tissues, MFF produced a fivefold increase in blood flow to skeletal muscle, and decreased adrenal blood flow compared to pentobarbital anaesthesia. Initial serum corticosterone levels were lower in rats given MFF anaesthesia, indicating better stress protection. This study also indicates that MFF anaesthesia is preferable to pentobarbital because tissue perfusion generally was better preserved.

Lipid accumulation in the myocardium during acute regional ischaemia in cats

Accumulation of lipid material in the myocardium was studied in cat hearts with acute regional ischaemia of 3 h duration. The fractional volume of lipid droplets in cytosol was analysed by electron microscopy of myocardial biopsies using a quantitative stereologic technique. Ischaemic and normally perfused myocardium were identified by fluoresceine injection, and tissue blood flow measurements were performed with labelled microspheres. In normal myocardium only small amounts of lipid droplets were found. A marked accumulation of lipid droplets occurred in borderline tissue between the two types of myocardium, whereas lipid accumulation in ischaemic myocardium was less pronounced. The arterial concentration of nonesterified fatty acids was clearly increased during the 3 h coronary artery occlusion period. Increased triglyceride synthesis from arterial fatty acids, or redistribution of intracellular lipids, are suggested as possible explanations for lipid accumulation during acute myocardial ischaemia.

Carvedilol Protects Against Lethal Reperfusion Injury Through Antiadrenergic Mechanisms

We examined the effect of carvedilol as compared with that of a combination of propranolol and doxazosin on lethal reperfusion injury in 21 feline hearts subjected to 40-min regional ischemia and 180-min reperfusion. A control group (n = 7) was compared with one group given carvedilol, a nonselective beta - and alpha 1-adrenoceptor blocker and antioxidant (n = 7) and another group given nonselective beta - and alpha 1-adrenoceptor blockade with propranolol and doxazosin (n = 7) during initial reperfusion. Infarct size (IS: percent of area at risk, AAR) determined by staining the myocardium with triphenyl tetrazolium chloride (TTC), was reduced both in the carvedilol-treated group (median 1.8%, p < 0.05) and in the group given propranolol/doxazosin (median 6.5%, p < 0.05) as compared with controls (median 14.4%). Treatment with carvedilol reduced IS more than did treatment with propranolol/doxazosin (p < 0.05). Longitudinal segment shortening measured with sonomicrometry, improved in both treatment groups as compared with control (p < 0.05), but to a greater extent in the group treated with carvedilol. In circumferential segments, only carvedilol significantly improved segment shortening. The incidence of ventricular fibrillation (VF) after reperfusion was reduced in both treatment groups as compared with control. Oxidized glutathione and thiobarbituric acid-reactive substances (TBARS) measured at the end of reperfusion did not differ between groups. Carvedilol protected against lethal reperfusion injury mainly through blockade of adrenoceptors.

Carvedilol improves function and reduces infarct size in the feline myocardium by protecting against lethal reperfusion injury

This study examined the effect of carvedilol, a vasodilating beta-adrenoceptor antagonist and antioxidant, on lethal reperfusion injury in feline hearts subjected to 40 min of regional ischemia and 180 min of reperfusion. 30 open chest anaesthetized cats were randomized into three groups. A control (n = 10) was compared with a group given carvedilol before coronary artery occlusions (n = 10) and a group given carvedilol immediately before and during early reperfusion (n = 10). Regional myocardial function was measured by sonomicrometry. Infarct size was determined by staining the left ventricle with triphenyl tetrazolium chloride. Myocardial blood flow was measured by radiolabeled microspheres. Tissue levels of glutathione were measured after reperfusion. Infarct size was significantly reduced compared to control both when carvedilol was given before ischemia (0.2 +/- 0.1 vs. 17.6 +/- 3.6%, P < 0.05). and when given immediately before reperfusion (3.7 +/- 1.3 vs. 17.6 +/- 3.6%, P < 0.05). Regional shortening improved significantly and the incidence of ventricular fibrillation during early reperfusion was reduced in both groups treated with carvedilol compared to control. Oxidized glutathione did not differ between groups in the post-ischaemic myocardium. This study supports that lethal reperfusion injury is a significant phenomenon. Furthermore, carvedilol reduces infarct size and reperfusion arrhythmias, and improves post-ischaemic regional myocardial function by protecting against both ischaemic and lethal reperfusion injury. The present study does not answer whether it is the non-selective beta- or alpha 1-receptor antagonism, the antiarrhythmic or the antioxidant actions of carvedilol that is responsible for the protective effect.

An anaesthetic protocol in the young domestic pig allowing neuromuscular blockade for studies of cardiac function following cardioplegic arrest and cardiopulmonary bypass

Background:  Neuromuscular blockade should, for ethical reasons, not be allowed in animal experiments unless the use is strongly motivated. Beforehand, the anaesthetic protocol must be documented without muscle relaxation in the species studied. Documentation is difficult to obtain from the scientific literature. When focusing on cardiac function over time, in particular, the ideal anaesthetic protocol should cause no or minor alterations in cardiac variables.

Comparison of the centrifugal and roller pump in elective coronary artery bypass surgery—a prospective, randomized study with special emphasis upon platelet activation

Objective—Evaluation of the centrifugal pump vs roller pump concerning effects upon platelet function, hemolysis and clinical outcome in elective coronary artery bypass surgery. Design—Thirty‐four patients were randomized to centrifugal or roller pump. Platelet activation was studied by flow cytometry before, during and up to 3 days after bypass. Results—Duration of bypass, ischemic period, peripheral anastomoses, hospital stay and mortality did not differ. In roller pump patients, platelet aggregates increased by 250% between end of bypass and 3 h postoperatively (p < 0.001). A secondary, fivefold increase in number of platelet aggregates was found on the 3rd postoperative day (p < 0.001). In the centrifugal pump group, these changes were not significant. Hemolysis increased (20%) at end of bypass and 3 h postoperatively (p < 0.005), and decreased to preoperative levels the next day without group difference. Conclusion—Platelet aggregation was significantly increased in roller compared with centrifugal pump patients, indicating higher susceptibility to postoperative thrombotic complications with the roller pump. Otherwise, there was no clinical evidence for superiority of the centrifugal pump.

Left ventricular strain, rotation, and torsion as markers of acute myocardial ischemia

This study investigates how tissue Doppler imaging (TDI) and speckle tracking echocardiography (STE) describe regional myocardial deformation during controlled reductions of left anterior descending (LAD) coronary artery perfusion pressure. In eight anesthetized pigs, a shunt with constrictor was installed from the brachiocephalic artery to the LAD. Data were obtained with open shunt, followed by four degrees of stenosis (S1-S4) of increasing severity: S1, ∼15%; S2, ∼35%; S3, ∼50%; and S4, ∼60% reductions of LAD perfusion pressure. At each situation, microspheres for perfusion measurements were injected and left ventricular (LV) short- and long-axis cineloops were recorded. In the anterior wall, radial, circumferential, and longitudinal one-layer STE strain, one-layer radial TDI strain, and three-layer radial TDI and STE strain were measured. LV peak mean rotation was measured at six equidistant levels from apex to base (in 7 pigs). LV torsion was calculated from end-systolic mean rotation. With open shunt, three-layer TDI analysis showed a transmural strain gradient with no perfusion gradient. Perfusion, one-layer TDI strain, and strain in the mid- and subendocardium from three-layer TDI were reduced at S2 (P < 0.05). STE strain was not affected until S3 (P < 0.05). Peak mean rotation, increasing toward the apex, decreased at the three apical levels at S4 (P < 0.05). LV torsion did not decrease (P = 0.26). In conclusion, TDI strain detected dysfunction already with minor changes in global hemodynamics, whereas STE strain was first reduced with moderate changes. LV peak mean rotation was not reduced until severe reduction of LAD perfusion pressure, but remained increasingly counterclockwise toward the apex. LV torsion remained unaffected by ischemia.