Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Rewarming”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources
PubMed1995

The role of free radicals in cold injuries.

Cold injury is a tissue trauma produced by exposure to freezing temperatures and even brief exposure to a severely cold and windy environment. Rewarming of frozen tissue is associated with blood reperfusion and the simultaneous generation of free oxygen radicals. In this review is discussed the current understanding of the mechanism of action of free oxygen radicals as related to cold injury during rewarming. Decreased energy stores during ischaemia lead to the accumulation of adenine nucleotides and liberation of free fatty acids due to the breakdown of lipid membranes. On rewarming, free fatty acids are metabolized via cyclo-oxygenase and adenine nucleotides are metabolized via the xanthine oxidase pathway. These may be the source of free oxygen radicals. Leukocytes may also play a major role in the pathogenesis of cold injury. Oxygen radical scavengers, such as superoxide dismutase and catalase, may help to reduce the cold induced injury but their action is limited due to the inability readily to cross the plasma membrane. Lipid soluble antioxidants are likely to be more effective scavengers because of their presence in membranes where peroxidative reactions can be arrested.

Animals↗
PubMed2001

Effect of hemodilution on the adequacy of cerebral perfusion under hypothermic cardiopulmonary bypass.

OBJECTIVE: Open heart surgery without transfusion has been performed even in children. However, the critical limit of the hemoglobin level has not yet been ascertained. Here, we have assessed experimentally the effect of the hemoglobin level on brain metabolism under hypothermic cardiopulmonary bypass. METHODS: Brain tissue pH was measured in 14 rabbits that were put on bypass with a different degree of hemodilution. Cardiopulmonary bypass was started at 37 degrees C and cooled down to 25 degrees C. After maintaining the bypass at 25 degrees C for 60 minutes, the animal was rewarmed to 37 degrees C for 30 minutes and then kept on-bypass for another 30 minutes. The perfusion flow was maintained as 10 ml/kg/min. RESULTS: The lowest hemoglobin level in each rabbit was from 2.5 through 8.5 g/dl. During hypothermic bypass, brain tissue pH increased from 7.21 +/- 0.16 (mean +/- SD, at the normothermic baseline) to 7.55 +/- 0.27 except 2 cases (6.91 +/- 0.16) whose hemoglobin level was lower than 3.0 g/dl. The brain tissue pH after 60 minutes on hypothermic bypass had a good correlation with the hemoglobin level (r = 0.831). After rewarming for 60 minutes, the brain tissue pH was decreased to 7.18 +/- 0.31. In 4 rabbits with less than 4.0 g/dl of hemoglobin, the brain tissue pH (6.67 +/- 0.24) was lower than the baseline level. In the other 10 rabbits, the brain tissue pH (7.22 +/- 0.16) was almost the same as the baseline level. The correlation coefficient between the brain tissue pH and the hemoglobin level after rewarming for 60 minutes was 0.778. CONCLUSIONS: These results indicated that severe hemodilution in cardiopulmonary bypass promoted acidosis in brain even during hypothermia.

Animals↗
PubMed1979

[Accidental hypothermia: treatment of a case using peritoneal irrigation].

A case of accidental hypothermia is reported. This patient was rewarmed by using a peritoneal irrigation. Rewarming was rapid and without complication. The patient was discharged from the hospital free from any sequellae. Peritoneal irrigation constitutes a fast and effective technique of core body rewarming in cases of moderate or severe hypothermia. Another advantage of this method is that it can be accomplished without complicated equipment and that it can be used even in small community hospitals.

Aged↗
PubMed1987

The effects of cardiopulmonary bypass and profound hypothermic circulatory arrest on anterior fontanel pressure in infants.

The Ladd transducer was used to measure anterior fontanel pressure in 23 infants undergoing cardiopulmonary bypass and profound hypothermic circulatory arrest for surgical correction of congenital heart disease. Mean (+/- SD) minimum oesophageal and rectal temperatures of 11.3 +/- 1.5 degrees C and 18.1 +/- 2.2 degrees C respectively were achieved with a mean duration of arrest of 53.4 +/- 13.9 minutes. During reperfusion cardiopulmonary bypass after circulatory arrest, mean anterior fontanel pressure (18.3 +/- 6.4 mmHg) increased above baseline pre-bypass values (10.6 +/- 2.9 mmHg) (p less than 0.005). Mean arterial blood pressure decreased significantly from pre-bypass values (57.0 +/- 11.8 mmHg) during both cooling (38.8 +/- 8.4 mmHg) and rewarming cardiopulmonary bypass (45.8 +/- 8.9 mmHg) (p less than 0.005). These changes were associated with a significant decrease in cerebral perfusion pressure during cooling (27.3 +/- 11.0 mmHg) and rewarming cardiopulmonary bypass (27.5 +/- 10.6 mmHg), compared with baseline pre-bypass values (46.5 +/- 12.3 mmHg) (p less than 0.005). The data demonstrate significant but transient decreases in cerebral perfusion pressure during cooling and rewarming bypass.

Cardiopulmonary Bypass↗
PubMed1998

[Validity of transcranial Doppler measurement of cerebral artery blood flow velocity during selective cerebral perfusion--an experimental study and clinical experiences].

The validity of transcranial doppler (TCD) as a monitor of cerebral blood flow during hypothermic selective cerebral perfusion (SCP) was investigated in dogs. Cerebral flow was maintained by infusing blood into the aortic arch while the descending aorta was totally crossclamped. The anterior cerebral arterial blood flow velocity (ACAv) was continuously measured with the EME TC2-64 TCD velocimeter by transorbital approach. In five dogs, cerebral flows were varied in steps from 5 to 10, 15, and 20 ml/kg/min in both cooling phase (rectal temp.: 25 degrees C, 20 degrees C) and rewarming phase (25 degrees C, 30 degrees C). ACAv was 46 +/- 7 cm/sec before cardiopulmonary bypass (CPB) started. Correlations between cerebral perfusion flow rate and ACAv were 0.59 in cooling phase and 0.85 in rewarming phase. In eight beagles, after core cooling at a constant systemic perfusion flow rate of 80 ml/kg/min, SCP was performed for 90 min at 25 degrees C; Group I (n = 4): 5 ml/kg/min, Group II (n = 4): 10 ml/kg/min, and rewarmed. Carotid arterial pressure (CAP) and ACAv were monitored continuously. Furthermore changes of jugular venous blood lactate/pyruvate concentration ratio after SCP were compared between groups. Percent changes of CAP during SCP for pre-CPB value were not significant between groups. Percent change of ACAv during SCP was significantly higher in Group II (59 +/- 12%) than in Group I (34 +/- 8%). Ninety minutes after SCP, lactate/pyruvate concentration ratio was increased in Group I (125 +/- 44%) and decreased in Group II (73 +/- 18%) for pre-CPB value. In Group I, it was considered that anaerobic metabolism and glycolysis were progressed. These results suggest that changes in ACAv reliably correlate with changes in cerebral perfusion flow rate and reflect cerebral metabolism. In five clinical cases, ACAv during SCP were about 50% of preoperative values. All the patients awoke well after operations and had no neurological complications. In conclusion, ACAv measured with TCD is available in monitoring cerebral blood flow during hypothermic SCP.

Aged↗
PubMed1994

[Diabetic coma with deep hypothermia. Successful resuscitation with hemofiltration].

A 41-year-old woman with severe juvenile diabetes mellitus suffered from profound hypothermia after loss of thermoregulation in diabetic ketoacidosis. She was found unconscious, without measurable blood pressure; the electrocardiogram (ECG) showed bradycardia of 30 min and the rectal temperature was 23.7 degrees C. The patient received mechanical ventilation, fluid therapy, warmed gastric lavage, and, unfortunately, inotropic medication. She was transferred to a department of cardiac surgery in order to continue the therapy with cardiopulmonary bypass (CPB). On arrival, the patient had a rectal temperature of 27.3 degrees C, the ECG showed an absolute arrhythmia with a frequency of 70/min, and the blood pressure was 63/43 mmHg. We decided to use a rapidly available but not highly invasive venovenous hemofiltration technique for slowly rewarming the patient. Vascular access was achieved by percutaneous femoral vein cannulation with a Shaldon catheter. The hemofiltration system (Gambro AK-10, Gambro AB, Sweden) was instituted with a blood flow rate of 200 ml/min. The hemofiltration monitor controls the pumps for filtering and substituting fluid volumes and allows the infusion solutions to be heated up to 40 degrees C. Sinus rhythm resumed without antiarrhythmic medications at a temperature of 29.5 degrees C, and within 8 h the patient was rewarmed to 35.5 degrees C. After treatment of the adult respiratory distress syndrome caused by pneumonia, she was discharged from the intensive care unit to complete treatment with no evidence of any permanent organ damage. We conclude that hemofiltration may be the method of choice for rewarming deeply hypothermic patients when their circulation is preserved.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2002

Was basking important in the evolution of mammalian endothermy?

The first mammals were small, nocturnal, and presumably had low metabolic rates and were therefore probably unable to maintain a constant high body temperature throughout cool nights. How these animals, without sufficient heat production for endogenous rewarming, were able to become warm and active again before the next activity period remains unresolved. However, we discovered that, similar to reptiles, the carnivorous marsupial mammal Pseudantechinus macdonnellensis (body mass 30.8 +/- 5.0 g) uses the morning sun to rewarm from low (26.3 +/- 4.5 degrees C) body temperatures during torpor. Our findings provide the first evidence of basking during rewarming from torpor in mammals and may provide an alternative explanation as to how ancestral mammals could have become nocturnal to avoid diurnal predators despite their small size and a low endogenous heat production.

Animals↗
PubMed1998

Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.

OBJECTIVE: Acute normovolaemic haemodilution with subsequent autologous blood transfusion after surgery is widely used to reduce homologous blood requirements during cardiac surgery. The hypothesis tested was whether a low intraoperative haematocrit (Hct) resulting from haemodilution decreases gastric mucosal pH (pHi). DESIGN: Prospective clinical investigation. SETTING: University Hospital of Vienna, Austria. PATIENTS: 16 consecutive patients scheduled for elective cardiac surgery. INTERVENTIONS: The patients were randomly assigned to one of two groups: In 10 patients (group 1), 500 ml of blood was withdrawn and stored after anaesthesia induction. An equal amount of 6% hydroxyethyl starch was simultaneously infused. After discontinuation of cardiopulmonary bypass (CPB), the autologous blood unit was transfused. Six patients (group 2), who were not subjected to haemodilution and autologous blood transfusion served as controls. In all patients, a gastric tonometry probe was inserted. MEASUREMENTS AND RESULTS: Measurements of pHi and Hct were performed before and after acute normovolaemic haemodilution, during pulsatile hypothermic (30-32 degrees C) CPB, after rewarming, and 30 min after autologous blood transfusion in group 1, and at corresponding time intervals in group 2. Repeated measures analysis of variance and the Mann-Whitney U test were used for statistical analysis. Data are presented as means +/- standard error of the mean. Haemodilution in group 1 caused a significant and persistent decrease in Hct (after haemodilution in group 1 34 +/- 1 vs 40 +/- 1% in group 2). In both groups, pHi decreased during rewarming and after termination of CPB. However, in group 1, pHi was better preserved than in group 2 (rewarming: 7.44 +/- 0.02 vs 7.34 +/- 0.04; after CPB: 7.38 +/- 0.03 vs 7.28 +/- 0.02; p < 0.05). CONCLUSIONS: Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery.

Acidosis↗
PubMed2000

The role of bone scanning in severe frostbite of the extremities: a retrospective study of 88 cases.

We performed a retrospective study of the results of two-phase technetium-99m hydroxymethylene diphosphonate bone scans in 88 patients with severe frostbite of the extremities. All patients were evaluated within 48 h after rewarming and all underwent a first bone scan (BS1) within 5 days after rewarming (median, day 2) (group 1). An excellent correlation was found between absence of tracer uptake in the phalanges and later amputation; this correlation was especially strong during the bone phase of the scans (specificity = 0.99, sensitivity = 0.96, positive predictive value = 0.92). Normal or high uptake in the phalanges was a reliable indicator of ultimate healing (negative predictive value = 0.99). The sensitivity of the examination was enhanced by performing a second scan (BS2) more than 5 days (median, day 8) after rewarming (group 2, n = 36). A comparative analysis of BS1 and BS2 demonstrated that some of the lesions continued to evolve between day 2 and day 8. This suggests that the lesions could still be modified during this period. On the basis of the findings it is recommended that bone scan be performed close to day 2 in all patients who present with lesions extending proximally to include the entirety of one or more phalanges. In the case of severe sepsis, the results of the first bone scan, BS1, can serve as an indication for emergency amputation. BS2 should be performed close to day 8 only if there is an area of low or absent uptake on BS1. It is concluded that scintigraphy is an excellent means of evaluating patients with severe frostbite of the extremities: as early as day 2 after the injury it can indicate whether amputation is necessary, and between days 2 and 8 it provides valuable information on the efficacy of treatment.

Adult↗
PubMed2003

Differential effects of surgical sympathetic block at the T2 and T4 level on vasoconstrictor function.

Endoscopic sympathetic block (ESB) is used as a treatment of excessive palmar sweating. In a prospective study we compared the effect of ESB at the level of the second (T2) and fourth thoracic ganglion (T4) on vasoconstriction and sweating of the hands. Sympathetic vasoconstriction was measured by computerassisted infrared thermography following ice water immersion of the hands in 22 hyperhidrosis patients before, two days and 3 months post op. In addition, palmar sweating before and 3 months post op was assessed by sudometry. After ESB the rewarming was accelerated in both T2 and T4 patients, but was significantly slower in the T4 group. Three months postoperatively rewarming had returned to the preoperative pattern in T4 patients but was still significantly faster in the T2 group. These effects were more pronounced in the fingertips than the hand dorsum. Sudomotor function was blocked in all T2 patients but had relapsed in 2 patients in the T4 group. Two T4 patients had not shown an effect on sudomotor function postoperatively. The normalization of rewarming kinetics may be explained by remaining fibers, denervation hypersensitivity or stimulation of catecholamine receptors, or neuronal reorganization. The effect of ESB T4 on sudomotor function has to be proven.

Adult↗
PubMed1992

Effects of temperature and flow rate on regional blood flow and metabolism during cardiopulmonary bypass.

Eleven dogs were subjected to a 150-minute period of cardiopulmonary bypass that consisted of a high-flow, normothermic phase, a high-flow, hypothermic phase, a low-flow, hypothermic phase, and then a high-flow, rewarming phase. Regional blood flow and oxygen consumption to the brain, intestines, kidney, and hind limb were determined at baseline and at 10-minute intervals during cardiopulmonary bypass. Blood flow to the carotid artery, superior mesenteric artery, and renal artery declined significantly with hypothermic cardiopulmonary bypass whereas blood flow to the femoral artery increased significantly. Although total body oxygen consumption returned to baseline values at the end of the rewarming phase, oxygen consumption for these regions differed somewhat from their baseline values. We conclude that blood flow during hypothermic cardiopulmonary bypass is shunted to skeletal muscle, particularly with high pump flows. Additionally, the return of total body oxygen consumption to baseline after rewarming is not necessarily reflected at the regional level.

Animals↗
PubMed1994

Cerebral metabolic effects of sequential periods of hypothermic circulatory arrest.

During repair of congenital heart defects, extended periods of hypothermic circulatory arrest (CA) have been shown to cause short-term cerebral metabolic and flow abnormalities as well as long-term neuropsychologic dysfunction. Occasionally, a second period of CA is required during the same operative setting to revise a complicated repair. However, the metabolic effects of two consecutive periods of CA on the brain are unclear. In this study, we compared the recovery of cerebral metabolism after 60 minutes of CA with that after two sequential 30-minute periods of CA separated by a brief period of rewarming (30'SEQ). Fifteen neonatal piglets (2 to 3 kg) were placed on cardiopulmonary bypass at 100 mL.kg-1 x min-1 and cooled to 18 degrees C. Each animal then underwent either 60 minutes of uninterrupted cardiopulmonary bypass at 18 degrees C, 60 minutes of CA, or two 30-minute periods of CA separated by a brief period of rewarming. After these experimental periods, animals were rewarmed to 37 degrees C and weaned from cardiopulmonary bypass. Data were obtained before cardiopulmonary bypass and after cardiopulmonary bypass at 37 degrees C and included measurements of cerebral blood flow by xenon 133 clearance, arterial and sagittal sinus blood gases, and cerebral metabolism (mL O2.100 g-1 x min-1). Our results demonstrated that acute recovery of cerebral metabolism was significantly impaired after 60 minutes of CA and that recovery of cerebral metabolism after two sequential 30-minute periods of CA was significantly better than after 60 minutes of continuous CA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Gingival blood flow and temperature changes in young humans with a history of periodontitis.

Whether such individuals have different gingival blood flow and temperature responses to local cooling than age- and sex-matched healthy controls was tested. Ten patients with a history of localized juvenile periodontitis or rapidly progressive periodontitis were selected from a periodontal clinic and matched with healthy controls. Gingival blood flow and temperature were monitored continuously before and after cooling via a twin probe placed in the gingival sulcus on the buccal of tooth No. 26. Blood flow was assessed by laser Doppler flowmetry and temperature by a small metal thermistor. Resting values were first recorded for 5 min, followed by 3 min of cooling to 19 degrees C by a gentle stream of cool air, then 12 min of rewarming was allowed. This protocol was repeated twice. Blood flow changes were analysed as the slope of the line formed between the last 2 min of cooling and the last 2 min of rewarming; temperature curves were analysed by a least-squares curve fit of a bi-exponential function. Patients with localized juvenile periodontitis and rapidly progressive periodontitis had similar rewarming temperature curves, but significantly faster blood flow recovery curves than controls (p less than 0.03). Thus, gingival blood flow in young periodontitis patients recovered more rapidly after local cooling than in healthy controls.

Adolescent↗
PubMed1996

Effects of hypothermia during cardiopulmonary bypass and circulatory arrest on sympathetic nerve activity in rabbits.

OBJECTIVES: Little is known about the effect of hypothermia on neural regulation. We investigated the effects of hypothermia during cardiopulmonary bypass (CPB) on control of renal (RSNA) and lumbar sympathetic nerve activity (LSNA), and plasma catecholamine levels. METHODS: We directly measured RSNA (n = 14) and LSNA (n = 6) during CPB in anesthetized rabbits. CPB was performed via cannulae in the aortic root for arterial perfusion and the right atrium for venous drainage. Systemic hypothermia was induced by core cooling. RSNA and LSNA were recorded at the nasopharyngeal temperature of 37, 30, 24, and 18 degrees C and after rewarming up to 37 degrees C while keeping mean arterial pressure at 70 mmHg by altering perfusion flow. Other variables such as blood gases or electrolytes were kept constant. RESULTS: RSNA at the temperature of 30, 24, and 18 degrees C significantly decreased by 91, 97, and 95% from control (37 degrees C), respectively. LSNA decreased by 18, 57, and 89% from control as well. The decreases in RSNA at 30 and 24 degrees C were greater than those in LSNA (P < 0.05). At 18 degrees C both RSNA and LSNA nearly disappeared. Circulatory arrest for 20 min during hypothermia at 18 degrees C caused no increase in RSNA while it increased LSNA. Plasma catecholamine levels at 18 degrees C were not different from those at 37 degrees C. Rewarming to 37 degrees C increased RSNA and LSNA by 321 and 92% from control (37 degrees C before cooling), respectively (P < 0.01). CONCLUSIONS: Hypothermia progressively decreased and rewarming markedly increased sympathetic nerve activity, but the effects of hypothermia on RSNA and LSNA were not uniform.

Animals↗
PubMed1985

Salutary effects of moderate hypothermia on the circulatory and myocardial consequences of acute coronary occlusion in dogs.

The efficacy of moderate hypothermia with rewarming in attenuating the myocardial and circulatory consequences of acute coronary ligation was studied in open-chest, anesthetized dogs. Thirty minutes after ligation of the proximal left anterior descending coronary artery, 14 dogs were surface-cooled to 27 degrees C, maintained at this temperature for 2 hr, rewarmed to normothermic levels, and monitored for an additional hour. Fifteen dogs were maintained for a corresponding time period after coronary ligation at normothermic levels. Dogs maintained normothermic demonstrated significant depression (from preligation values) of dP/dt, cardiac output (CO), stroke volume (SV), and left ventricular stroke work and power (LVSW, LVSP) at elevated levels of left ventricular end-diastolic pressure (LVEDP). Dogs subjected to the hypothermic procedure demonstrated decreased inotropic status during hypothermia, but with rewarming, exhibited significantly greater values of left ventricular pressure, dP/dt, CO, SV, LVSW, and LVSP at lower values of LVEDP than observed in dogs maintained normothermic. Increased dysrhythmic activity was not observed during hypothermia. Hearts from dogs subjected to the hypothermic protocol demonstrated qualitatively greater dehydrogenase activity both at the periphery and in the center of the nonperfused region. The results suggest that moderate hypothermia during evolving myocardial infarction may preserve left ventricular cardio- and hemodynamics and thus may be useful in delaying morphological and functional deterioration until definitive treatment can be instituted.

Animals↗
PubMed1986

Whole body protection during three hours of total circulatory arrest: an experimental study.

Survival following 3 hr of total circulatory arrest under profound hypothermic conditions was explored in 19 adult mongrel dogs. Thermoregulatory management included combined surface/perfusion hypothermia and azeotrope anesthesia in 95% O2/5% CO2. All animals were resuscitated and survived for at least 12 hr. During the last seven trials (Group II) the following principles were applied: uniform whole-body cooling where differences between rectal, esophageal, and pharyngeal temperatures averaged less than 1 degree C, induction of circulatory arrest at approximately 3 degrees C, constant lung inflation (10-12 cm H2O between 20 degrees C cooling and 20 degrees C rewarming, including the 3-hr arrest period) and ventilation assistance with positive end-expiratory pressure (4 cm H2O) after 20 degrees C rewarming, intraoperative maintenance of colloid osmotic pressure (COP) above 11 mm Hg, replacement of the cooling perfusate with a colloid-rich rewarming prime (COP = 15 mm Hg) and restoration of hemostasis with fresh whole blood transfusions. The application of these principles resulted in the long-term survival of five animals with four survivors displaying no clinically detectable neurological abnormalities. However, two animals developed optic impairment and one animal died from intusseption on the fourth postoperative day. Despite the improved results, it should also be noted that during pilot (Group I) studies (from which the aforementioned principles were derived) fatalities from complications attributed to systemic edema, central nervous system, or pulmonary or coagulation dysfunctions occurred in 9 out of 12 trials. We conclude that whole body protection following 3 hr of total circulatory arrest at a uniform temperature less than 5 degrees C can be successfully accomplished.

Animals↗
PubMed1991

Glycine prevention of cold ischemic injury in isolated hepatocytes.

Isolated hepatocytes suspended in a liver preservation solution (University of Wisconsin (UW) solution) and exposed to cold (5 degrees C) ischemia lose viability (LDH release) after 3 (76.5 +/- 2.6% extracellular LDH) and 4 days (90.3 +/- 5.7% extracellular LDH) storage when rewarmed (37 degrees C) in Krebs-Henseleit buffer. However, if 3 mM glycine is added to Krebs-Henseleit buffer the loss of LDH on rewarming was suppressed (% LDH = 24.4 +/- 2.2% and 33.2 +/- 3.0%, at 3 and 4 days, respectively). The protection by glycine could also be obtained by storing the hepatocytes in the UW solution containing 15 mM glycine and rewarming in the absence of glycine in Krebs-Henseleit buffer. There did not appear to be a relationship between the protection by glycine and glutathione concentration of the hepatocytes as shown by the lack of effect of a glutathione synthetase inhibitor (butathionine sulfoximine) on the protective effects of glycine. Other amino acids did not provide protection to hepatocytes exposed to cold ischemia. The mechanism of action of glycine is not known, but this compound may be important in improving cold storage of livers for transplantation.

Animals↗
PubMed1988

Hypothermia prevents increased capillary permeability following ischemia-reperfusion injury.

UNLABELLED: Severely injured trauma victims are frequently hypothermic. It is unclear, however, whether hypothermia itself is a detrimental or protective physiologic response to injury. One of the major consequences of fluid resuscitation following ischemic injury is edema formation, characterized by ischemia-reperfusion injury models. The purpose of this study was to examine the effect of regional hypothermia on a feline intestinal model of ischemia-reperfusion injury. An autoperfused segment of cat ileum was isolated and arterial, venous, and lymphatic vessels were cannulated. Lymph flow (Q1), lymph (C1), and plasma (Cp) protein concentrations and segmental blood flow (Qb) were measured. Permeability changes were characterized by the minimal C1/Cp ratio obtained by elevating venous outflow pressure. Animals were divided into the following groups: Group I: 1 hr of intestinal ischemia (30 mm Hg) with autoreperfusion; Group II: 1 hr of intestinal hypothermia (28 degrees C) with subsequent rewarming; Group III: 1 hr of combined ischemia and hypothermia. Group III animals were either kept hypothermic (IIIA) or rewarmed (IIIB) during autoreperfusion. Minimal C1/Cp ratios (mean +/- SEM) were as follows: CONTROL: 0.15 +/- 0.02; Group I*: 0.32 +/- 0.03; Group II: 0.15 +/- 0.01; Group IIIA: 0.18 +/- 0.02; Group IIIB*: 0.42 +/- 0.02; (* = P less than 0.01 vs control). Reperfusion flow rates were no different between Group IIIA and Group IIIB animals. Ischemia-reperfusion, but not hypothermia alone, caused a marked increase in intestinal capillary permeability. Permeability increased after combined ischemia and hypothermia only if reperfusion was accompanied by rewarming. Hypothermic reperfusion protected against the increased permeability following ischemia.

Animals↗