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

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

Even during adequate general anesthesia, hypertension is a common phenomenon in patients undergoing aortocoronary bypass grafting (CABG). In such cases application of vasodilators is recommended in order to decrease myocardial oxygen consumption. This study was performed to compare two commonly used substances, i.e., nitrates and nifedipine, with regard to their influence on hemodynamics, renal blood flow, kidney function, and the requirement for homologous blood transfusions. METHODS. Forty-four patients gave their informed consent to the study. They were randomly divided into 2 groups: group 1 received nitroglycerin (3.0 micrograms/kg.min), group 2 nifedipine (Adalat, 0.5 microgram/kg.min) in order to prevent hypertension in the phase before onset of cardiopulmonary bypass (CPB). Anesthesia was induced by etomidate and succinylcholine and maintained as a modified neuroleptanalgesia with fentanyl (up to 50 micrograms/kg), midazolam (0.3 mg/kg.h), and pancuronium (0.1 mg/kg). Systolic blood pressure was kept within the range of 120-160 mm Hg; in case of higher values boluses of either 0.25 mg nitroglycerin or 0.5 mg nifedipine were administered. Cardiac index, stroke volume index, rate-pressure product, intrapulmonary shunt, and pulmonary and total peripheral resistances were evaluated at five predefined points: (1) after induction of anesthesia; (2) before incision; (3) before cannulating the aorta; (4) after decannulating the aorta; and (5) at the end of operation. Creatinine and free-water clearances as well as sodium and potassium excretion were calculated for three phases of the operation: (A) induction of anesthesia--onset of CPB; (B) during CPB; and (C) end of CPB--end of operation. CPB was performed using a membrane oxygenator (Sorin 51) and a nonpulsatile blood flow of 2.5 1/min.m2, which was reduced during mild hypothermia of 30-32 degrees C to 1.7 l/min.m2. Mean arterial pressure in both groups was kept at approximately 70 mm Hg. In case of lower pressures norepinephrine (50-100 micrograms/bolus) was administered; higher pressures were treated as described above. Volume substitution was performed initially by 500 ml hydroxyethyl starch and continued, if necessary, by homologous blood or 5% human albumin in order to keep the hematocrit greater than 30 in the phases before and after CPB. RESULTS. Group 2 showed significantly higher values of cardiac index and stroke volume index at point 3 while the rate-pressure product was clearly lower, indicating better myocardial performance and lower oxygen consumption than in group 1. Creatinine and free-water clearances in all three phases did not differ. However, sodium excretion during CPB was significantly higher in the nifedipine group while potassium excretion showed no differences. The average requirement for blood and blood substitutes was lower in group 2, but the difference could not be confirmed statistically because of the large dispersion of values. Nevertheless, 4 patients in the nifedipine group but no patient in group 1 did not need homologous blood transfusion. CONCLUSION. In comparison to nitrates, nifedipine showed some advantages in the treatment of hypertension during CABG: (1) it provided better myocardial performance; (2) it had a more reliable but not too long-lasting effect on elevated total peripherial resistance, leading to better hemodynamic stability; and (3) by not affecting the capacitance vessels it may necessitate fewer homologous blood transfusions.
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PMID:[Nifedipine versus nitroglycerin in aortocoronary bypass surgery. The effect on hemodynamics, kidney function and homologous blood requirement]. 153 39

Leucocyte counts, rectal temperature, P-cortisol, P-glucose, P-transferrin, P-orosomucoid, P-IgM and hematocrit were investigated in 24 men undergoing inguinal herniotomy. The patients were randomised to epidural analgesia (n = 8), local infiltration anaesthesia (n = 8) or local infiltration anaesthesia plus local wound hypothermia with ice bags (n = 8). The rectal temperature rose (p less than 0.01) in patients randomised to epidural analgesia but not in the other groups. However, blood granulocyte and acute phase protein changes were similar in all groups. The neural blockade was sufficient in all patients as judged by lack of increase in P-cortisol and P-glucose. Thus, local infiltration anaesthesia and wound hypothermia could not prevent the inflammatory response to small clean surgery.
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PMID:Influence of local anaesthesia and local hypothermia on leucocyte, temperature, and transferrin response to surgery. 156 99

A successful emergency replacement of the ruptured ascending thoracic aorta by means of ringed Dacron tube graft for 69-year-old male was presented, who had been admitted to our hospital with deep cyanosis and shock. He had experienced severe chest pain one hour prior to admission followed by mental confusion and was brought by ambulant service. Emergency chest enhanced computed tomography showed a clear ruptured dissecting aneurysm (DeBakey Type I) with complicated with pericardial tamponade. Soon after this admission he developed bradycardia with hypotension and quickly went into shock. After induction of anesthesia, cardiac arrest developed. External cardiac massage was started at the same time. Partial cardiopulmonary bypass using femoral vein to artery bypass with the membrane oxygenator was instituted and the body was cooled until moderate hypothermia (25 degrees C). The pericardium was opened and blood clot was removed. The ascending aorta ruptured which was replaced with ringed Dacron tube graft (24 mm in diameter). Patient tolerated procedure well and made good postoperative recovery with temporally mild mental confusion. He discharged 2 months after the surgery without any neurological or mental complication. He has been followed up for six months in excellent condition.
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PMID:[A successful emergency surgical treatment of DeBakey type I dissecting aneurysm complicated with cardiac tamponade and bleeding shock]. 156 16

A 20-year-old woman in status asthmaticus who failed to respond to conventional therapy and ventilation of the lungs with 0.5-2.0% halothane, was cooled to 30 degrees C for almost 5 days as the arterial carbon dioxide tension rose above 15 kPa. Halothane was not of immediate value, contrary to other reports. A reduction in carbon dioxide production by controlled hypothermia permitted more suitable ventilation parameters, but extensive muscle weakness caused by a steroid-induced myopathy complicated weaning from respiratory support. Prospective measurement of serum creatinine phosphokinase concentration in patients given high dose corticosteroids may herald the onset of a myopathy.
Anaesthesia 1992 Mar
PMID:Treatment of acute severe asthma assisted by hypothermia. 156 91

Earlier work has shown that thyrotropin releasing hormone (TRH) produces dose-dependent decreases in body temperature (Tb) and metabolic rate when microinjected into the dorsal hippocampus (HPC) or preoptic/anterior hypothalamus (PO/AH) of awake ground squirrels. This study employed a behavioral paradigm to investigate the possibility that TRH-induced hypothermia is associated with a decrease in thermoregulatory set point. Six animals were successfully trained to press a bar for radiant heat escape and cool air reinforcement in order to obtain a cooler ambient temperature (Ta). During experimental testing, the animals were microinjected remotely with TRH (10-1000 ng/microliters) or a control solution (sterile saline or TRH-OH) into the PO/AH. The micro-injections were delivered via bilateral injection cannulae inserted through chronic bilateral cannula guides that had been stereotaxically implanted under pentobarbital anesthesia. Cumulative and time-integrated bar presses were obtained on a computer generated display. Tb, measured in the brain via a bead-type thermistor, and chamber Ta were recorded continuously. Following TRH administration, a significant increase in mean bar-press rate was observed during the period in which Tb was falling, when compared to a comparable time period just prior to the microinjection. These findings complement results obtained from four animals that were trained to press a bar for heat reinforcement in a cold (- 10 degrees C) environment. In this alternative behavioral paradigm, microinjection of TRH into the PO/AH or HPC induced a decrease in mean bar-press rate as Tb was falling. The results support the hypothesis that TRH-induced hypothermia in golden-mantled ground squirrels is achieved by lowering thermoregulatory set point.
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PMID:Thyrotropin-releasing hormone action in the preoptic/anterior hypothalamus decreases thermoregulatory set point in ground squirrels. 157 2

The effects of hypothermia on hypoglycemic brain damage were studied in rats after a 30-min period of hypoglycemic coma, defined as cessation of spontaneous EEG activity. The rats were either normothermic (37 degrees C) or moderately hypothermic (33 degrees C). Morphological brain damage was evaluated after various periods of recovery. Hypothermic animals with halothane anesthesia never resumed spontaneous respiration, thus requiring artificial ventilation during recovery (maximally 8 h). In contrast, when isoflurane was used as the anesthetic agent, all animals survived and were examined after 1 week of recovery. There was a tendency towards gradually higher arterial plasma glucose levels during hypoglycemia with lower body temperature. The time period from insulin injection until isoelectric EEG appeared was gradually prolonged by hypothermia, and was shorter when isoflurane was used for anesthesia. Brain damage was examined within the neocortex, caudoputamen and hippocampus (CA1, subiculum and the tip of the dentate gyrus). Damage to neurons was found to be of two types, namely condensed dark purple neurons (pre-acidophilic) and shrunken bright red-staining neurons (acidophilic). In the neocortex, no clear influence of temperature on the degree of injury was seen. In the caudoputamen, the number of injured neurons clearly decreased at lower temperature (33 degrees C, P less than 0.001) when halothane was used, while no such difference was seen when isoflurane was used as the anesthetic agent. Likewise, a protective effect of hypothermia was seen in subiculum (P less than 0.01) when halothane, but not isoflurane was used.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The influence of hypothermia on hypoglycemia-induced brain damage in the rat. 157 15

The authors tested the extent to which thermoregulatory vasoconstriction decreases cutaneous heat loss during isoflurane anesthesia. Thermoregulatory vasoconstriction was provoked by central hypothermia in five nonsurgical volunteers given isoflurane anesthesia. Peripheral arteriovenous shunt flow was quantified using forearm-fingertip skin-surface temperature gradients and volume plethysmography. Capillary blood flow on the chest was evaluated using laser Doppler flowmetry. The central temperature triggering peripheral vasoconstriction (the thermoregulatory threshold) was 34.6 +/- 0.4 degrees C. Central body temperature decreased less than or equal to 0.2 degrees C in the period from 1 h preceding onset of significant vasoconstriction until 1.5 h afterward. Chest skin-surface blood flow decreased 21% during the period from 2 h before to 1 h after significant fingertip vasoconstriction. In contrast, fingertip blood flow decreased approximately 50-fold in the same period. The correlation between fingertip blood flow and skin-temperature gradient was excellent. Total heat loss decreased approximately 26% (25.3 +/- 3.9 W) in the period from 2 h before significant peripheral vasoconstriction to 1 h afterward. Loss from the arms and legs (upper arm, lower arm, thigh, and calf) decreased approximately 24% in the same period. Heat loss from the trunk and head decreased only 14%; in contrast, loss from the hands and feet decreased approximately 57%. There were no clinically important changes in blood pressure or heart rate during vasoconstriction, but oxyhemoglobin saturation (measured by pulse oximetry) increased slightly. These data suggest that thermoregulatory vasoconstriction only minimally decreases cutaneous heat loss.
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PMID:Thermoregulatory vasoconstriction during isoflurane anesthesia minimally decreases cutaneous heat loss. 157 32

Effects of pH and PaCO2 on cerebral as well as systemic hemodynamics and oxygen consumption were investigated during moderate hypothermia under 0.5% halothane anesthesia. Twenty-seven adult mongrel dogs were cooled to 28 degrees C (brain temperature) with a surface cooling method. They were divided into 3 groups, pH-stat (pH 7.35 n = 9), alpha-stat (pH 7.48 n = 9), and alkalosis (pH 7.70 n = 9). During hypothermia cardiac index fell to 74%, 56%, and 45%, and cerebral blood flow to 54%, 42%, and 36% in pH-stat, alpha-stat and alkalosis groups, respectively. Cerebral and systemic oxygen consumptions decreased to approximately 54% and 47%, respectively in all groups. Cerebrospinal fluid pH rose from 7.36 precooling to 7.49 (pH-stat), 7.53 (alpha-stat), and 7.72 (alkalosis). We concluded from these results that pH-stat and alpha-stat management have no significant effect on either hemodynamics or metabolism during moderate hypothermia but alkalosis management has deleterious effects because of the alkalinity itself and of the hyperventilation by which the alkalosis is induced.
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PMID:[Optimal pH and PaCO2 during moderate hypothermia]. 157 16

Intraoperative hypothermia is a major problem in anesthetic management. We compared the heat conserving effect of a forced air warming system (Bair Hugger, Augustine Medical Inc.) with that of a warming blanket. Sixteen patients undergoing abdominal surgery were studied. Patients were anesthetized with nitrous oxide and oxygen combined with epidural anesthesia. Patients received tympanic, rectal, bladder and core temperature monitorings. Patients were divided randomly to Bair Hugger group (BH, n = 8) or warming blanket group (WB, n = 8). Temperature were measured every one hour over three hours. The BH group showed significantly higher temperatures than WB group. Bair Hugger system is an efficient way to maintain intraoperative body temperature.
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PMID:[Heat conservation during abdominal surgery]. 157 25


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