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PubMed1980

Does pulsatile flow improve perfusion during hypothermic cardiopulmonary bypass?

Each of 10 patients undergoing hypothermic cardiopulmonary bypass was perfused in turn with (1) the standard flow delivered by a roller pump and (2) pulsatile flow induced by a "pulsatile assist device" (Datascope Corp., Paramus, N. J), presented in random order at the same mean flow. Whole-body oxygen consumption, blood lactate concentration, systemic vascular resistance, urinary flow, and thermal gradients were measured during each type of flow and after rewarming. No significant difference in any of these variables was seen between the two types of flow. After conventional rewarming the temperature gradient between core tissues and muscle was not influenced by the type of flow used during rewarming.

Aged↗
PubMed1995

[Use of Finapres during warming for postoperative patients].

We used Finapres during rewarming after extracorporeal circulation in 16 patients who underwent cardiac surgery. In patients with passive rewarming there were no differences in blood pressure measured with a Finapres and that by an invasive monitor. On the other hand, in patients rewarmed with the aid of nitroglycerin, there were statistically significant differences between blood pressures measured with indirect and direct methods.

Aged↗
PubMedDate not supplied

Cryopreservation extenders affect calcium flux in bovine spermatozoa during a temperature challenge.

Bovine spermatozoa are commercially cryopreserved by diluting the cells in media, known as extenders, followed by slow cooling and freezing. Previous work has shown that this process of cryopreservation alters the cells' ability to control divalent calcium (Ca2+) movement. This study evaluated the effect of a brief exposure to common extenders on bovine spermatozoa during subsequent cooling and rewarming. Three fresh ejaculates from each of three bulls were each split and incubated for 30 minutes at 25 degrees C in milk extender or phosphate-buffered saline (PBS) (control); three other fresh ejaculates from each of three bulls were similarly incubated in egg yolk-Tris extender (EYT) or PBS. Spermatozoa were washed and the fluorescent Ca2+ indicator, indo-1 acetoxymethyl ester, was used to monitor the internal Ca2+ in the spermatozoa in Ca(2+)-free PBS over a continuous temperature gradient of 25 degrees C (15 minutes), cooling to 5 degrees C (32 minutes), at 5 degrees C (15 minutes), rewarming to 25 degrees C (25 minutes), and at 25 degrees C (15 minutes). Milk exposure reduced the initial percentage of missing acrosomes and EYT exposure improved the initial viability and acrosome morphology compared to the controls; only milk immediatetly increased internal Ca2+. The initial rate of Ca2+ uptake at 25 degrees C was greater for milk or EYT-exposed spermatozoa than controls (P < 0.05). During cooling, the rate of Ca2+ uptake in all spermatozoa increased (P < 0.01), and it continued to increase during the 15 minutes at 5 degrees C. During rewarming to 25 degrees C, the internal Ca2+ in all spermatozoa declined.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Open heart surgery with bloodless priming for ventricular septal defect and pulmonary hypertension].

In 17 patients with ventricular septal defect and pulmonary hypertension (VSD, PH) weighing 5.2 kg to 9.5 kg, open heart surgery was conducted with bloodless priming (total priming volume: 370-470 ml). None of the patients required blood transfusion during their hospital stay. The post-operative respiratory status was excellent in all cases with duration of intubation being 6 +/- 3 hours. While 12 patients weighing over 6.6 kg maintained individual constant hematocrit (Hct) values during cardiopulmonary bypass (CPB), all 5 patients weighing under 6.1 kg showed significant decrease during rewarming (17 +/- 2% after initiation of CPB to 14 +/- 2% during rewarming). The lowest Hct value was 12% during rewarming in 6.0 kg infant. The pre-operative circulating blood volume (CBV) was calculated retrospectively from the priming volume, the Hct value after anesthetic induction and the Hct value after initiation of CPB. The relationship, CBV (ml) = body weight (kg) x 72-13 (r = 0.85, p < 0.01) was derived. Using this equation, we calculated the predicted Hct level after initiation of CPB using the 370 ml bypass circuit in 43 VSD PH patients weighing 3.4 kg-5.9 kg. The Hct values were 17 +/- 2% in 13 patients weighing over 5 kg with 12 (91 percent) above 15%, and 13 +/- 2% in 30 patients weighing under 4 kg with 3 (11 percent) above 15%. Hct levels of 34%-36% before CPB were essential in patients weighing 4.0 kg-4.9 kg for the Hct level after initiation of CPB to exceed 15%.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Loss, Surgical↗
PubMed1995

The role of magnesium in myocardial preservation.

The purpose of this review is to look at the role of magnesium in the formation of preservation and reperfusion solutions for the ischaemic heart. Preservation of the heart during cardiac surgery procedures, including cardiac transplantation, can be divided into distinct phases: arrest, cold storage in the case of transplantation, global ischaemia during implantation or cardiac surgery procedures, followed by reperfusion when the heart is rewarmed and restarted. Although the magnesium ion can play a significant role in myocardial protection, it is important to recognize the different types of protection required during these different phases of surgical procedures. The rationale for the inclusion of magnesium in cardioplegic solutions is threefold: (i) for its negative inotropic effect; (ii) to prevent ischaemia-induced magnesium loss; (iii) to influence cellular ionic movements. Preservation temperature as well as the concentration of other ionic constituents present in the preservation solution alter the effects of magnesium. Results obtained from animal models suggest that elevated magnesium (16 mM) is beneficial to the hypothermic preservation of hearts with extracellular type solutions, especially when calcium is elevated in the solution formulation. Research has shown that the amplitude of the inotropic effect of magnesium varies from one species to another so that the beneficial effect of magnesium is inferior in the less sensitive species. Using the human atrial trabecular preparation as a model for myocardial preservation, we have assessed the effects of elevated magnesium on the recovery of developed force, both for long-term preservation (24 h) during hypothermic arrest (4 degrees C) and for reperfusion during rewarming of the trabeculae. No clear pattern emerged when the ratio of calcium to magnesium was altered in St Thomas' I and II solutions used for the storage. However, when the atrial trabecular preparation was rewarmed in a Krebs Henseleit buffer containing an elevated level of magnesium (16 mM), a greater number of trabeculae reached a greater developed force and had higher levels of energetic metabolites than when the magnesium in the Krebs Henseleit buffer was 1.2 mM. Several studies have suggested that an elevated magnesium prevents calcium overload by competing with this ion at the membrane, and reduces the workload, while ATP reserves and ion homoeostasis are re-established. The role of the magnesium ion in hypothermic preservation of the human myocardium is still not clear after many clinical and experimental studies and requires further investigation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

[The changes on cerebral hemodynamics during selective cerebral perfusion cooling].

We studied the influence on cerebral hemodynamics with 10 pigs, weighing 25 to 30 kg, when the temperature of perfusion blood changed in both rapid cooling and rewarming, and in slow them. As for the protocol of temperature, we decided that rapid change was the large temperature gradient of more than 0.5 degree C/min, and slow change was the small gradient of less than 0.3 degree C/min. Cardiopulmonary bypass (CPB) was established with a flow rate of 60 ml/kg/min, and core cooling was performed until the temperature of the returned blood from internal jugular vein reached 25 degrees C/min. For selective cerebral perfusion (SCP), blood was infused into aortic arch with the clamp of descending aorta at the temperature of less than 20 degrees C. We measured regional tissue cerebral blood flow (TCBF), intracranial pressure (ICP), carotid arterial flow (CAF), and carotid arterial pressure (CAP), and PCO2 in both CPB and SCP. Rapid cooling during CPB caused an elevation in CAP, and marked decrease in CAF, ICP, and PCO2. In contrast, rapid rewarming caused the significant increase in CAF, ICP. Slow change did not cause marked difference in CAP, CAF, and ICP, and PCO2. Moreover, TCBF was not significant in both rapid and slow changes. On the other hand, rapid change in SCP caused a significant decrease in CAP, significant difference in CAF, ICP. Slow change did not cause significant difference in them as same as in CPB. In conclusion, we presume that the influence on cerebral hemodynamics is less in slow cooling and rewarming than in rapid changes.

Animals↗
PubMed1994

Effects of fatty acids on myocardial calcium control during hypothermic perfusion.

Although hypothermia is regarded as providing protection of the myocardium during cardiac operations, rapid cooling of the myocardium in the nonarrested state may have detrimental effects on the function of the myocardial cell membrane as a permeability barrier. We therefore measured total cellular calcium in isolated working rat hearts, receiving either glucose (11.1 mmol/L) or glucose plus palmitate (1.2 mmol/L), before, during, and after a 40-minute hypothermic arrest (10 degrees C, Langendorff perfusion). In both groups a rise in total cellular calcium, measured by 45Ca2+ technique, was observed during hypothermia, followed by a decline on rewarming. However, the rise in total cellular calcium during hypothermia was significantly (p < 0.05) higher in hearts perfused with palmitate (from 1.0 +/- 0.2 to 3.5 +/- 0.2 nmol/mg dry weight) compared with that in glucose-perfused hearts (from 1.1 +/- 0.13 to 2.6 +/- 0.2 nmol/mg dry weight). Palmitate-perfused, but not glucose-perfused, hearts showed arrhythmias and delayed pressure development 1 to 2 minutes after rewarming. In addition cardiac output of these hearts was significantly lower (p < 0.025) than that of glucose-perfused hearts 5 to 10 minutes after rewarming. These data show that hypothermia per se causes a net calcium uptake in isolated rat hearts and that this effect is aggravated by high concentrations of fatty acids. Thus the impaired recovery of myocardial function in palmitate-perfused hearts can possibly be related to a distorted calcium handling.

Adenosine Triphosphate↗
PubMed1993

Role of platelets in hepatic allograft preservation injury in the rat.

Cold preservation of liver allografts injuries hepatic sinusoidal lining cells. This injury is exacerbated on reperfusion, in part because of adhesion of leukocytes. Platelets also adhere to activated endothelial surfaces. In this study we examined the role of platelets in preservation injury. Our specific aim was to determine whether the degree of platelet adhesion on reperfusion of preserved rat livers was related to duration of cold or warm ischemia and whether platelet adhesion resulted in injury to allografts. We also examined the effect of prior activation of platelets on adhesion and injury. Rat livers were preserved at 1 degree C for different time periods in University of Wisconsin solution and then reperfused for 3 hr on the isolated perfused rat liver system with Krebs-Henseleit solution to which unactivated isolated rat platelets were added. Other livers were rewarmed before reperfusion or reperfused with activated platelets. Platelets were lost from the circulation in all studies; the percentage reduction of circulating platelets was dependent on the length of preservation. The initial platelet concentration did not affect the rate of reduction of platelets in the circuit. Rewarming before reperfusion increased platelet adherence, and prior activation also increased adherence. With electron microscopy we determined that platelets adhered in small aggregates to endothelial cells or endothelial cell remnants. Adherent platelets appeared more activated and contained fewer granules than did unperfused platelets. Liver injury as measured by release of transaminases into perfusate was worsened by longer periods of cold preservation and by addition of rewarming to the protocol. The presence of platelets under these circumstances aggravated injury. Prior activation of platelets also increased the extent of injury. These studies show that platelets have an important role in cold preservation-reperfusion injury.

Alanine Transaminase↗
PubMed1993

[Resuscitation in heart arrest due to severe hypothermia].

Two patients were resuscitated after cardiopulmonary arrest due to severe hypothermia. The first patient, a 76-year-old man, had ventricular fibrillation resistant to conventional therapy; he was rapidly rewarmed by means of cardiopulmonary bypass. In the second patient, a 77-year-old woman, classical resuscitation led to restoration of spontaneous circulation. The patient was subsequently rapidly rewarmed with hemodialysis with fluid of 40 degrees C. We conclude that rapid rewarming with cardiopulmonary bypass is the treatment of choice in severely hypothermic patients presenting with cardiac arrest that is resistant to conventional therapy. Hemodialysis seems a suitable technique in patients who remain deeply hypothermic after resuscitation. However, it is difficult to assess its value because of the lack of clinical studies comparing this technique with other procedures.

Aged↗
PubMed1993

Thermoregulation and afterdrop during hypothermia in patients with poikilothermia.

The pathophysiology of afterdrop of core temperature during rewarming in patients with induced or accidental hypothermia remains controversial. We studied the effect of cooling and rewarming in four female patients with acquired poikilothermia and in four normal females. Exposure to cold air (16.5 degrees C) induced shivering and adequate vasoconstriction in normal individuals, without a fall in rectal temperature (Tr; 36.3 +/- 0.2 degrees C [mean +/- SD]); subsequent heating (40 degrees C) induced a rise in Tr to 37.0 +/- 0.3 degrees C and generalized sweating. The four patients all had spontaneous hypothermia (Tr 34.1 +/- 0.9 degrees C) before cooling. Tr decreased by 0.3-0.9 degrees C during cold exposure, and a marked afterdrop of Tr (0.3-0.5 degrees C) occurred during rewarming: this did not occur in normal individuals. Cooling failed to induce shivering and vasoconstriction in three patients. No patient showed visible sweating during heating despite a Tr of up to 38.0-38.5 degrees C and skin temperature of up to 37.7-38.5 degrees C. The basal metabolic rate was decreased by 71-82% in all patients during steady-state hypothermia and remained lowered during normothermia in two patients. We conclude that during hypothermia three of the four patients showed severe disorders of peripheral vasomotor function and shivering response. These data provide evidence for thermal conduction as the major mechanism of afterdrop during hypothermia.

Adult↗
PubMed1995

[Cardiopulmonary resuscitation with continuous veno-venous hemofiltration for intraoperative cardiac arrest owing to hypothermia--a case report].

A 77-year-old female was scheduled for an exploratory laparotomy under nitrous oxide-oxygen-neurolept anesthesia. At the time of admission to the operating room, the rectal temperature was 36.0 degrees C. From the beginning of operation, the body temperature dropped slowly despite constant efforts of warming with a blanket and warm intravenous fluids. At 5 hours and 15 minutes after the beginning of operation, she developed cardiac arrest due to hypothermia. At this time the rectal temperature was 31.8 degrees C. In spite of cardioversion and intravenous administration of epinephrine, we could not resuscitate her successfully. Immediately, rewarming was started with continuous veno-venos hemofiltration (CVVH). When the rectal temperature rose to 32.9 degrees C one hour after the rewarming, cardioversion was performed again and spontaneous heart beat was observed. As soon as the rectal temperature rose to 34.0 degrees C, CHF was stopped. Her consciousness recovered 2 hours and 10 minutes after cardiopulmonary resuscitation, we conclude that rewarming with CVVH can be an effective method of cardiopulmonary resuscitation in a patient suffering cardiac arrest due to hypothermia.

Aged↗
PubMed1995

[The evaluation of cerebral oxygen balance during moderate hypothermic cardiopulmonary bypass].

The aim of this study was to evaluate cerebral oxygen balance during moderate hypothermic cardiopulmonary bypass (CPB). We measured jugular bulb venous oxygen saturation (SjO2), oxygen extraction ratio (O2 ER), glucose extraction ratio (Glu ER), and lactate production ratio (Lac PR) in 20 adult patients undergoing cardiac surgery. Fentanyl and midazolam anesthesia, alpha-stat blood gas management, non-pulsatile flow of 2.0-2.4 l.min-1.m-2, and moderate hypothermia were used in all cases. During cooling (at 34 degrees C of nasopharyngeal temperature), jugular-arterial blood difference of carbon dioxide partial pressure and O2 ER decreased, and SjO2 increased significantly. On the other hand, O2 ER increased, and SjO2 decreased significantly during rewarming (at 34 degrees C). There were no significant changes in oxygen-glucose index, lactate-glucose index, lactate-oxygen index, lactate production ratio, and lactate-pyruvate ratio. Ten (50 %) of 20 patients who met reduced saturation criteria (defined as SjO2 < 55 %), showed significantly higher O2 ER and lower SjO2 than the non-reduced saturation group from postinduction to rewarming period. We conclude that cerebral venous reduced saturation represents a global imbalance in cerebral oxygen supply-demand-utility that may occur during rewarming period, and that the reduced saturation group represents a significant difference in cerebral oxygen balance during even stable hypothermic CPB. These episodes, however, are not associated with the acceleration of anaerobic glycolysis.

Adult↗
PubMed1977

Induced hypothermia in dogs with acute myocardial infarction and shock.

Acute myocardial infarction with shock (AMI/S) was produced in 46 anesthetized "closed-chest" dogs by catheter injection of metallic mercury into the circumflex coronary artery. Twenty-four dogs were kept normothermic and 22 were maintained at 32 degrees C. Nine of the latter were rewarmed to 37 degrees C. and the experiments then were terminated, so that true survival time was arbitrarily shortened. Including these dogs, the survival time was three times longer than in the normothermic series (p less than 0.001). Hypothermia reduced heart rate (HR) by 34 percent, oxygen consumption by 38 percent, and myocardial oxygen consumption by an estimated 30 to 40 percent, while cardiac output (CO), stroke volume, and stroke work were unchanged. Left ventricular end-diastolic pressure (LVEDP) was reduced by 40 percent during hypothermia (p less than 0.05) and increased by 60 percent on rewarming. HR during rewarming increased substantially more than CO and thereby significantly reduced stroke volume.

Acute Disease↗
PubMed1995

Hemodynamics and oxygen metabolism in the pig during long-term hypothermia: comparison of 2 pH strategies.

The aim of this study was to investigate the influence of acid-base management (pH stat or alpha stat) on hemodynamics and oxygen metabolism during long-term hypothermia in the pig. Seventeen female pigs were anesthetized, slowly cooled to 28 degrees C with cooling mats and kept at this temperature for 36 h. Thereafter, slow rewarming was performed with inhalation of a 40 degrees C warm air/oxygen mixture and insulation. Eight of the 17 pigs were ventilated according to the pH stat strategy and 9 according to the alpha stat strategy. Both groups were compared 4 times each for hemodynamics and metabolism during cooling, hypothermia and rewarming. The 2 strategies showed no significant difference in cardiac output, heart rate or mean arterial pressure. The only difference in hemodynamics was observed in mean pulmonary artery pressure and pulmonary artery resistance during hypothermia, showing higher values in pH stat animals. As for oxygen metabolism, oxygen consumption during hypothermia was significantly higher in alpha stat animals. Long-term hypothermia with spontaneous circulation revealed significant differences in oxygen metabolism and pulmonary artery pressure as well as resistance between alpha and pH stat acid-base management. These differences may be of importance when using moderate hypothermia in a clinical or experimental setting.

Acid-Base Equilibrium↗
PubMed1994

Oxygen consumption following pediatric cardiac surgery.

Metabolic responses during recovery from cardiac operations for various congenital heart defects were studied in 30 mechanically ventilated pediatric patients in two groups: infants 1 year or less (group I) and children more than 1 year old (group II). Oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured using a pediatric metabolic monitor intermittently after induction of anesthesia, after skin closure, 2 to 4 hours postoperatively, and on the first postoperative morning in the pediatric intensive care unit. Energy expenditure and respiratory quotient were determined from respiratory gas measurements. Rectal and skin temperatures and hemodynamic variables were recorded at the same time. VO2 increased during rewarming 2 to 4 hours after the operation by 12 +/- 15% in group I and by 24 +/- 19% in group II, while rectal temperature increased by 2.0 +/- 1.2 degrees C and 1.8 +/- 1.4 degrees C, respectively. No further increase in VO2 occurred until the first postoperative morning. A hypermetabolic response was not seen in all cases despite marked thermal changes. High-dose fentanyl anesthesia partly explains the low responses. On the other hand, low cardiac output may also compromise oxygen supply. Sixty-three percent of infants were treated for cardiac failure before surgery and 75% needed inotropic support immediately after the operation. Low central venous oxyhemoglobin saturation values (ScvO2 < 60%) were observed during rewarming, indicating an increase in oxygen extraction secondary to an increased oxygen demand in the brain during recovery from anesthesia, and a low cardiac output or delayed restoration of cerebral blood flow after CPB and deep hypothermia.

Anesthesia, Intravenous↗
PubMed2006

Successful transcutaneous pacing in 2 severely hypothermic patients.

The clinical condition of profound hypothermia is well described in the medical literature. There have been many case reports and studies describing successful aspects of caring for this problem. Significant bradycardia is a known pathophysiologic consequence of profound hypothermia. Transcutaneous pacing for this condition is not a routine or recommended practice in the literature. This case report details 2 patients with profound hypothermia and resultant bradycardia with hypotension. In both cases, transcutaneous pacing was successfully applied and used as part of the resuscitation. In both cases, transcutaneous pacing was required to maintain an adequate blood pressure so that continuous arteriovenous rewarming could be used during the resuscitation. Both cases had successful outcomes, and the rewarming process was greatly assisted by the pacing procedure.

Aged, 80 and over↗
PubMed2006

[Resuscitation from accidental hypothermia of 22 degrees C with circulatory arrest: importance of prehospital management].

In winter, French Medicalised Ambulance Service rescued a 50-year-old patient after suicide attempts by jump from a bridge in the Seine. The body was discovered after more than 10 minutes of immersion. She was unconscious and in deep hypothermia with circulatory arrest. Basic CPR was started immediately and oral intubation and 100% oxygen ventilation was performed. Ventricular fibrillation appeared but repeated defibrillation failed due to profound hypothermia (rectal temperature: 28 degrees C). The patient was immediately transported to hospital. CPR and mechanical ventilation was continued during transport. The patient was taken in emergency room. The oesophageal temperature was 22 degrees C. Rewarming using extracorporeal circulation was immediately initiated after insertion of femoral access. At 27 degrees C, ventricular fibrillation started and was converted by external defibrillation to a pulse-generating cardiac rhythm. At 360 minutes, the patient's rectal temperature had reached 36 degrees C and she was disconnected from cardiopulmonary bypass with inotropic support. She was transferred to the intensive care unit after 9 hours of resuscitation, rewarming and stabilisation. Mechanical ventilation was needed for 15 days because of adult respiratory distress syndrome. Renal failure, pneumonia also occurred. She was successfully extubated on day 15 and was discharged from intensive care unit on day 21, suffering no neurological side effects.

Acute Kidney Injury↗
PubMed2007

Temperature changes stimulate contraction in the human radial artery and affect response to vasoconstrictors.

BACKGROUND: Radial artery conduits are increasingly used in coronary artery bypass grafting as an additional arterial graft to the internal thoracic artery. Their reactive nature remains a concern, often necessitating the routine use of topically applied vasodilators, such as glyceryl trinitrate, papaverine, phenoxybenzamine, or calcium channel antagonists, in theatre. During preparation prior to surgery and grafting, radial artery conduits are exposed to cooling and rewarming. We investigated how these temperature changes would affect radial artery contractility and how commonly used topical treatments might be used to prevent this. METHODS: Human radial artery was obtained excess to surgery and arterial sections used in organ bath tension experiments or for the culture of smooth muscle cells from medial explants. RESULTS: The radial artery responded to rapid cooling by the addition of 22 degrees C buffer with contraction. Gradual cooling, over a 20 to 30 minute period, reduced basal tension and the response to potassium chloride (KCl) and noradrenaline. Subsequent rewarming from 22 degrees C to 37 degrees C reestablished contraction at precooled levels and led to an elevation of the basal tension. Increases in tension measured in the radial artery were paralleled by increases in intracellular calcium in smooth muscle cells. Contraction induced by rapid temperature changes could be blocked by glyceryl trinitrate but not by phenoxybenzamine. Papaverine and calcium channel blockers had only limited activity. CONCLUSIONS: Temperature changes commonly encountered in theatre during the preparation of radial artery grafts are likely to cause contraction. If rapid temperature change cannot be avoided during graft preparation, then topically applied glyceryl trinitrate will block these responses.

Aged↗