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Query: UMLS:C0020672 (hypothermia)
 17,327 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxygen availability during cardiopulmonary bypass was assessed in 22 patients under hypothermic and relatively normothermic conditions. The patients were divided into two groups, 17 of whom received ACD blood and 5, CPD blood. The mean P50 for all patients fell from a preoperative value of 25.9 +/- 2.4 (SD) to 15.6 +/- 2.1 during hypothermia confirming a leftward shift of the oxyhemoglobin dissociation curve. Oxygen uptake, calculated from a-v oxygen content differences (avDO2) and flow, was significantly lower during hypothermic bypass (65 +/- 27 ml/min) than during rewarming (121 +/- 41 ml/min). The increase in oxygen affinity during hypothermia was influenced also by changes in acid base and 2,3-DPG concentrations, the changes being similar in both the ACD and CPD groups of patients. During rewarming, however, oxygen availability was increased in the CPD group presumably from significantly increased 2,3-DPG concentrations. A "functional" value of hemoglobin, based upon the effects of the shift of the oxyhemoglobin dissociation curve and, therefore, reflecting the true capacity of hemoglobin to unload oxygen at the tissue level, was calculated. During the hypothermic phase of bypass, this functional hemoglobin was only 4.2 g/100 ml blood, suggesting that, in spite of reduced metabolic demands, oxygenation reserves are minimal.
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PMID:Oxygen availability during hypothermic cardiopulmonary bypass. 1 30

The well known effects of the lowering of the intraerythrocyte 2, 3, diphosphoglycerate (2, 3, DPG) level and hypothermia, on the affinity of oxygen for hemoglobin, lead the authors to study the influence of these parameters on this affinity during general anesthesia. The following observations were made in 15 adult subjects, undergoing prolonged general anaesthesia (average time: 3 hrs. 10 minutes): the dissociation curve of oxyhemoglobin (DCO) by the method of mixing, the intraerythrocyte 2,3, DPG level, the hemoglobin concentration and arterial blood parameters (PO2, PCO2, pH). These measurements were recorded before and after the general anaesthesia. The results were the following: a significant reduction of P50, measured under standard conditions (from 27.64 +/- 1.74 torr to 25.57 +/- 2.28, p less than or equal to 0.01) associated with a decrease in 2,3, DPG (from 0.94 +/- 0.31 mol/mol Hb at 0.64 +/- 0.24 p less than 0.01). Among the factors responsible for this variation in the affinity, it was proved that the volume of blood transfused was of importance as well as a decrease in body temperature during the operation. When the temperature is made to vary from 37 degrees C to 35 degrees C. the P50 ranges from 25.57 +/- 2.28 to 22.86 +/- 0.97 (p less than 0.01). To conclude the authors underline the importance of hypothermia and the volume of blood transfused (average time of preservation = 15 days) on the effects of the affinity of oxygen for hemoglobin.
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PMID:[Changes in the affinity of oxygen for hemoglobin during general anesthesia]. 2 19

This is a report a a new system for freezing human red blood cells in the same polyvinyl chloride plastic container in which the blood is collected and separated into components. This polyvinyl chloride plastic collection bag with integrally attached transfer packs for blood collection, component separation, red blood cell biochemical modification, freezing, storage, and post-thaw dilution before washing, represents a major advancement in the freeze-preservation process. The label with the donor's blood type and identification number affixed to the bag at the time of collection remains in place throughout the freezing and thawing process. The transfused red blood cells are of superior quality, and the processing cost is less than with other methods of freeze-preservation. There is a lower risk of contamination with these red blood cells because manipulation of the product is kept at a minimum. "Rejuvenation", a bioengineering process by which outdated red blood cells can be salvaged, can be incorporated into the preservation process using one of the attached transfer packs of the primary collection bag. This process has been introduced as a possible means of alleviating the dramatic blood shortages which occur periodically. Red blood cells may also be "rejuvenated" after storage in the liquid state to increase their 2,3 DPG and ATP levels to 150 to 200% of normal, and these red blood cells with improved oxygen transport function have been administered to anemic patients with and without cardiopulmonary insufficiency, patients undergoing cardiopulmonary bypass and treatment with hypothermia during cardiac surgery, and in instances where nonhemolytic transfusion reactions might be expected.
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PMID:Human red blood cells with normal or improved oxygen transport function prepared and frozen in the primary polyvinyl chloride plastic blood collection container. 39 73

The question as to what extent the hematocrit (Hct) is a strong indicator for or against the need for transfusion of whole blood or blood products is still controversial. In order to enable the clinician to make a definite decision, a number of aspects have to be taken into consideration. The human organism has only limited oxygen reserves, and these are even more limited under pathological conditions. Oxygen flux - the amount of oxygen transported by the blood in 1 min - is a critical factor in the oxygenation of the human body. Another critical factor is oxygen consumption, which is highly variable depending on the presence of conditions such as rest, shivering, seizures, hypothermia, etc. Furthermore, different organ systems have different oxygen consumption rates. The ratio of oxygen consumption to oxygen flux is referred to as the oxygen extraction rate or oxygen utilization. Under normal conditions oxygen uptake is independent of oxygen flux, and thus independent of blood flow. Under conditions of organ dysfunction, however, oxygen deficiency may be present without being recognized on standard clinical diagnostic parameters. The normal human organism has a number of possibilities to compensate for acute or chronic anemia, i.e., increases in cardiac output, organ perfusion, 2,3-DPG content, a shift in the oxygen dissociation curve, etc. These compensatory mechanisms may, however, be restricted or cease to function under conditions of acute or chronic disease. Arterial and mixed-venous PO2 and oxygen content are some of the parameters used to assess the oxygen reserves available to the organism even under critical conditions. Although oxygen content is the most significant of these parameters, accurate measurement of this parameter remains a problem of laboratory medicine. PVO2 is of only limited importance under conditions of anemia. Minimum oxygen content or minimum oxygen flux values should under no conditions be approximated during anesthesia or intensive care. The critical Hct as an indicator for or against transfusion of blood or blood products is considerably modified by restricted organ function, anesthesia, intensive care treatment, resuscitation, etc.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Which factors determine the critical hematocrit as an indication for transfusion?]. 153 35

Basic factors of O2 transport disturbances and mechanisms of their compensation have been studied in 1200 patients after cardiac surgery. It has been shown that O2 transport decrease is induced by damages in oxygenating blood function, decreased cardiac performance and hemoglobin blood level, oxyhemoglobin dissociation curve deviation and changes in Hb affinity to O2 with regard to 2,3-DPG content. The causes of arterial O2 transport damage affect the treatment procedures, including oxygen therapy, controlled lung ventilation, erythrocyte mass transfusion, inotropic drug administration, hypothermia.
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PMID:[Disorders of O2 transport and their correction in heart surgery patients]. 262 30

Preserved stored blood undergoes metabolic changes depending on the duration of storage. These metabolic changes include a deprivation of 2,3-diphosphoglycerate (2,3-DPG), acidosis and hyperkalemia. The preservative contains citrate as an anticoagulant which binds the ionised serum calcium. 2,3-DPG depleted erythrocytes show a clearly elevated oxygen affinity. Following massive transfusion, these changes can also occur in the recipient. Under these conditions, patients with coronary artery disease show impaired heart function. Prejudicial changes concerning other vital systems have not yet been definitely proved. Acidosis, hypocalcemia and hyperkalemia can take place under massive transfusion. Normally the body's own compensatory mechanisms ensure sufficient recompensation; however, under hypothermia or shock these mechanisms can be impaired. Disturbances of the electrolyte and acid base system are safely detected by ECG and regularly performed acid base analysis.
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PMID:[Metabolic disorders caused by blood transfusions]. 306 47

Blood may provide superior cardioplegia compared with crystalloid cardioplegic solution. However, the results are controversial. This may be due to a leftward shift of the hemoglobin (Hb)-O2 dissociation curve induced by hypothermia, increasing the oxygen affinity for Hb. This effect may negate the potential benefit of blood cardioplegia. The oxygen affinity for Hb can be decreased by increasing the red cell 2,3-diphosphoglycerate (2,3-DPG), and hence, more oxygen can be delivered to the myocardium. The present investigation was undertaken to study the effects of 2,3-DPG-enriched blood cardioplegia on the functional recovery of the myocardium and changes in the coronary sinus red blood cell (RBC) adenosine-triphosphate (ATP), lactate, and RBC DPG after one and a half hours of reperfusion following one hour of ischemic cardiac arrest in dogs. The dogs were divided into three groups: crystalloid (CR); stored blood (SB), and high 2,3-DPG blood (HDPG) cardioplegic groups. Incubation of canine RBC in phosphoenal pyruvate (PEP) led to a 36% increase in DPG and a rightward shift in the Hb-O2 dissociation curve. There was a 4 mm Hg shift in the P50. When compared with the CR group, there was a significant decrease in the cardiac index (CI) and left ventricular work index (LVWI) and a significant increase in the total systemic vascular resistance (TSVR) in the SB group. The CI and LVWI of the HDPG group were similar to those of the CR group, but the TSVR was significantly greater in the former group. The LVWI was significantly greater and the TSVR smaller in the HDPG group as compared with those in the SB group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:High 2,3-DPG blood cardioplegia and myocardial preservation during cardiopulmonary bypass. 334 90

In the management of severe pediatric brain injury, attention has previously been paid to brain edema, ICP elevation and low cerebral perfusion pressure (CPP). However, in the acute stage within 3-6 hours after trauma, brain hypoxia and hyperglycemia associated with diffuse brain injury are often observed. We have pointed out brain thermo-pooling (elevation of brain tissue temperature) and brain hypoxia caused by defective release of oxygen from hemoglobin (due to decrease in red blood cell enzyme (DPG)) as a new mechanism of brain injury. To treat these pathologic changes, we have developed a brain hypothermia treatment, the major purpose of which is to prevent brain hypoxia, brain thermo-pooling, neurohormonal changes causing cytokine encephalopathy, and a selective, radical-mediated damage of the dopamine A10 nervous system. The brain tissue temperature is initially adjusted to 35 degrees C with adequate cerebral oxygenation, followed by brain hypothermia at 34 degrees C for 1 weeks to prevent brain hypoxia, free radical reactions, brain edema and ICP elevation. What is most difficult in the pediatric brain hypothermia treatment is to maintain metabolic balance in the injured brain tissue and pulmonary infections associated with an immune crisis. When a rapid elevation of serum glucose is noted it is critical to lower the value because glucose quickly penetrates the blood-brain barrier and increases pyruvate and lactate by inhibiting the TCA cycle metabolism. Thus, hyperglycemia during brain hypothermia treatment is one of the major target of management. Another problem is immune crisis associated with secondary pulmonary infections. To prevent them, early enteral nutrition and replacement of L-arginine were most useful, as well as preconditioning for rewarming as follows: serum albumin > 3.0 g/dl; lymphocyte > 1500/mm3; T-H (CD4) lymphocytes > 55%; serum glucose, 120-140 mg/dl; vitamin A > 50 mg/dl; Hb > 12 g/dl and 2,3 DPG, 10-15 mumol/gHb; O2 ER, 23-25% and AT-III, > 100%. The clinical benefit of this therapy is still controversial.
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PMID:[Brain hypothermia treatment for the management of severe pediatric brain injury]. 1072 86

Pediatricians in the hospital setting must frequently treat children who require massive transfusion (MT) in a variety of clinical situations ranging from major trauma to neonatal hyperbilirubinemia. After identifying the need for massive transfusion, the pediatrician must select the appropriate blood components. Different blood components have specific temperature, preservative, and time requirements for their storage. Changes, termed storage lesions, occur over time in blood components during storage; biochemical changes include decreased levels of 2,3-DPG, a decrease in pH, and an increase in supernatant potassium (K+) with a concurrent decrease in intracellular K+. These changes may affect the function and the viability of components. Additionally, physical changes such as deformation of the red cell membrane occur during storage. Knowledge of these storage lesions is necessary for the pediatrician to make the most appropriate decisions regarding the preparation and selection of components during MT. Serious complications of MT include hemostatic abnormalities, biochemical/metabolic abnormalities, hypothermia, mechanical injury and the effect of Rh incompatibility, each of which has a specific management response. Pediatricians need to be aware of the potential complications associated with massive transfusion, to take measures to prevent them when possible, to anticipate additional transfusion requirements, and to know how to manage them in the pediatric patient.
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PMID:Massive blood transfusion. 1128 83

In 1990's, use of machine perfusion for organ preservation has been abandoned because of improvement of preservation solutions, efficient without perfusion, easy to use and cheaper. Since the last 15 years, a renewed interest for machine perfusion emerged based on studies performed on preclinical model and seems to make consensus in case of expanded criteria donors or deceased after cardiac death donations. We present relevant studies highlighted the efficiency of preservation with hypothermic machine perfusion compared to static cold storage. Machines for organ preservation being in constant evolution, we also summarized recent developments included direct oxygenation of the perfusat. Machine perfusion technology also enables organ reconditioning during the last hours of preservation through a short period of perfusion on hypothermia, subnormothermia or normothermia. We present significant or low advantages for machine perfusion against ischemia reperfusion injuries regarding at least one primary parameter: risk of DFG, organ function or graft survival.
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PMID:Does machine perfusion decrease ischemia reperfusion injury? 2495 Sep 33


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