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

The halothane-diethyl ether azeotrope was evaluated in dogs as the anesthetic agent for deep surface hypothermia with total circulatory arrest for open-heart operation. All 10 animals given azeotrope in 100% oxygen (O2) experienced atrial arrhythmias during cooling, and 1 had ventricular fibrillation prior to the completion of cooling at 18 degrees to 20 degrees C. After only 30 minutes' arrest, 8 of the 10 dogs had postoperative motor disturbances. Administering the azeotrope in 95% O2 and 5% carbon dioxide (CO2) yielded markedly improved results characterized by a rapid, smooth cooling course, easy resuscitation following circulatory arrest, and rapid rewarming, and 3 out of 10 dogs experienced mild motor disturbance after 60 minutes of circulatory arrest. This method, when compared with our standard method of ether in 100% O2, resulted in reduced blood lactates and a striking improvement in clinical status on the first postoperative morning. In limited clinical trials, infants undergoing repair of congenital cardiac defects have done well and responded as expected based on the laboratory experience. Since the results with the azeotrope in 95% O2 and 5% CO2 were at least as good as, and in several instances better than, those with the standard method employing either, the nonexplosive characteristic of the azeotrope warrants continued evaluation of this agent.
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PMID:Improved anesthesia for deep surface-induced hypothermia: the halothane-diethyl ether azeotrope. 735 62

Hypothermia is a common postsurgical problem, yet information documenting the impact of laparoscopy on perioperative heat balance is scarce. This paper quantifies the changes in core temperature over a 3-h period of high-flow CO2 insufflation in a randomized, controlled trial of six pigs. Each animal was anesthetized and studied on three occasions under standardized conditions, acting as its own control via insufflation with no gas compared with insufflation by cold gas and warmed gas. Insufflation of CO2 gas at high-flow rates over a prolonged period of time results in a significant fall in core temperature. The provision of warmed rather than cold insufflated gas confers no protection against changes in core temperature during laparoscopic surgery due to the small amount of heat required to warm the gas to body temperature. A much greater effect is the latent heat required to saturate the insufflated gas. Most of the hypothermic effect is due to this, and could be minimized by humidifying the flow.
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PMID:Hypothermia induced by laparoscopic insufflation. A randomized study in a pig model. 748 86

1. This paper reviews current knowledge regarding interactions between body temperature and the respiratory responses to hypoxia and/or hypercapnia, with special emphasis on how these interactions might predispose towards sudden infant death syndrome (SIDS). 2. Use has been made of an adult rat model in which body core temperature is fixed by means of an intra-abdominal heat exchanger. Initial studies indicated that hyperthermia (Tb approximately 41 degrees C) enhanced the ventilatory response to hypercapnia, whereas hypothermia (Tb approximately 35 degrees C) interacted with hypoxia to depress respiration. 3. Studies involving hypothalamic lesions in urethane-anaesthetized rats have implicated the posterior hypothalamic area in the hypoxia/hypothermia interaction. Further studies are directed towards examining the role played by more caudal areas, including the raphe nuclei. 4. It has been shown that not only does the hypoxia/hypothermia interaction depress breathing but it also reduces, or sometimes eliminates, the ventilatory response to hypercapnia, which under normal circumstances provides one of the most powerful excitatory inputs to the respiratory centres. This implies that an expected reversal of the respiratory depression by build up of CO2 levels may not occur, which in turn has important implications for SIDS. 5. The literature dealing with the effects of hyperthermia on hypoxic and hypercapnic responses is also reviewed. It is concluded that environmental heat stress may only become a significant problem when it accompanies a febrile infection, under which circumstances it may seriously compromise thermoregulatory ability and alter breathing responses to chemical stimuli.
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PMID:Influence of body temperature on responses to hypoxia and hypercapnia: implications for SIDS. 758 8

Blood acid-base changes were studied during acute hypothermia (4-6 h) induced by cold exposure in the unanesthetized rat. Stewart's quantitative analysis was applied as a complementary approach to determine the relative contributions of several non-respiratory components to the arterial acid-base response. Acute decrease in body temperature (TB) lowered PaCO2 (32.5 to 14.5 mmHg) and [HCO3-]a(24.20 mEq/L to 17.56 mEq/L), increased pHa (7.481 to 7.608) and diminished the [OH-]/[H+] ratio, but had no significant effect on [SID] or [Atot], although both total phosphorus [PT] and inorganic phosphate [Pi] increased. The acid-base changes found were intermediate between those predicted by alpha-stat and pH-stat hypotheses. Deviation from the regulative alpha-imidazole strategy was more apparent in the plasma than in the intraerythrocyte compartment. We conclude that blood pH changes observed were mainly caused by increased relative ventilation (lung ventilation per unit of CO2 removed) and by resulting changes in PCO2, with a minor metabolic component but without significant contribution from ionic shifts or changes in plasma protein concentration.
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PMID:Factors influencing acid-base status during acute severe hypothermia in unanesthetized rats. 762 15

We report the case of a 9-year-old girl with multiple problems due to hypothalamic dysfunction of obscure origin: apnoeic spells, behavioural problems, developmental delay, hypodipsia with bouts of hypernatraemia, episodes of spontaneous hypothermia, obesity, petit-mal seizures, non-progressive precocious puberty, absence of respiratory response to CO2 and probably insensitivity of hyposensitivity to pain. She also had hyperprolactinaemia and decreased human growth hormone secretion. Hypothyroidism of central origin and hyposecretion of cortisol were also present. Multiple brain CT-scans failed to reveal any tumour or other anatomical abnormality. Her clinical course was improved initially by treatment with clomipramine, but she died suddenly, and the autopsy failed to disclose any anatomical lesion. We compare this case with three similar previously reported cases.
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PMID:Hypothalamic dysfunction in a child: a distinct syndrome? Report of a case and review of the literature. 768 46

Because disordered autoregulation of cerebral blood flow may underlie neurologic injury associated with cardiopulmonary bypass (CPB), we studied the effects of normothermic (37 degrees C) and hypothermic (18 degrees C) CPB on cerebral vascular reactivity in 6 to 8-week-old piglets. Hypothermic CPB animals were subdivided into alpha-stat and pH-stat groups (n = 6 animals each group) according to acid-base management protocol. Cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), cerebral vascular resistance (CVR), and CBF response to hypercapnia were examined before, during, and 1 hour after CPB and used to calculate CVR per millimeter of mercury change in arterial partial pressure of CO2: (CVRnormocapnia - CVRhypercapnia)/(PaCO2 hypercapnia - PaCO2 normocapnia). Before CPB, CBF, CMRO2, and vascular reactivity to elevated CO2 were similar in the three groups; these parameters remained unchanged by normothermic CPB. However, during hypothermic CPB, CBF and CMRO2 decreased in both alpha-stat and pH-stat groups; in the alpha-stat group, CBF decreased from 27 +/- 5 mL.min-1.100 g-1 (normothermic CPB) to 5 +/- 1 mL.min-1.100 g-1 (hypothermic CPB) (p < 0.05) and CMRO2 decreased from 1.8 +/- 0.21 to 0.24 +/- 0.04 mL.min-1.100 g-1 (p < 0.05), whereas in the pH-stat group CBF decreased from 28 +/- 2 to 9 +/- 1 mL.min-1. 100 g-1 (p < 0.05) and CMRO2 decreased from 1.63 +/- 0.07 to 0.31 +/- 0.09 mL.min-1.100 g-1 (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cerebral blood flow during cardiopulmonary bypass: influence of temperature and pH management strategy. 769 12

Hypothermia and isoflurane alone increase the potencies of steroidal muscle relaxants (MRs). We studied the combined influence of isoflurane and hypothermia on MR potency. Phrenic nerve-hemidiaphragm preparations of rats were mounted in modified Krebs' solution and aerated with 5% CO2-95% O2 gas mixture at 37 degrees C and 4% CO2 at 27 degrees C to maintain the CO2 content constant. Phrenic nerves were stimulated with 0.1 Hz supramaximal impulses and elicited tension of the diaphragm was recorded. Isoflurane 1% was added after stabilization of twitch tension and MR was added 60 min later. Twitch tension was reduced by 20% +/- 2.5% at 37 degrees C and 3.5% +/- 0.7% at 27 degrees C from control with only isoflurane. The IC50 (inhibitory concentration, 50%) values of the MRs decreased significantly (P < 0.05) with isoflurane at both temperatures. The ratios of the IC50 values without and with isoflurane of the benzylisoquinolinium MRs were significantly more at both temperatures (P < 0.05) indicating the enhancement of potentiation of their action by isoflurane over steroidal MRs. When the soluble concentration of isoflurane at 27 degrees C was kept similar to that of at 37 degrees C, the ratios of all the MRs were reduced significantly from the ratios at 37 degrees C, indicating a reduction of potentiation. When the partial pressure of isoflurane was kept constant at 37 degrees C and 27 degrees C, the potentiating action of the MRs by isoflurane was similar. But when the partial pressure was decreased to keep the concentration of isoflurane constant, the potentiation was reduced.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The effect of isoflurane and temperature on the actions of muscle relaxants in rat in vitro. 776 49

We measured continuously cerebral venous oxyhaemoglobin saturation (SjvO2) using a 4F fibreoptic catheter in 11 patients scheduled for elective myocardial revascularisation. The aims of this study were to assess the Oximetrix 3 computer and Opticath 40 cm catheter during moderate hypothermic cardiopulmonary bypass, and identify epochs of cerebral hypoperfusion (SjvO2 < 54%). Radial artery pressure, brain electrical activity, arterial and cerebral venous oximetry (dual oximetry), end-tidal CO2 and nasopharyngeal temperature were recorded continuously in each patient. Following in vivo calibration of 11 continuous SjvO2 catheters and monitor, 57 simultaneous, paired recordings were additionally taken. The mean difference between the catheter SjvO2 and the in vitro laboratory derived value was 0.34%, with a 95% confidence interval -3.2% to 2.4%. In 10 patients SjvO2 decreased below normal at rewarming and myocardial reperfusion: mean lowest value 37%, range 19%-55%. Reduced SjvO2 were associated with a decrease in perfusion pressure (r = 0.292, 80 DF, p = 7.7* 10(-3)), and with an increase in nasopharyngeal temperature (r = -0.46, 115 DF, p = 2.7* 10(-7)) after moderate hypothermia. The Oximetrix 3 computer and Opticath 40 cm catheter provided reliable and accurate continuous monitoring of SjvO2 during nonpulsatile cardiopulmonary bypass involving hypothermia with haemodilution and identified rewarming as the period of greatest risk of global cerebral hypoperfusion.
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PMID:Detection of cerebral hypoperfusion during cardiopulmonary bypass. Continuous measurement of cerebral venous oxyhaemoglobin saturation during myocardial revascularisation. 1143 76

Intraabdominal pain, shoulder pain and tachycardia are observed after pelviscopic interventions. Recent publications blame this on hypothermia caused by the CO2 gas used. The authors discuss in detail the physics of the problems connected with the heating of CO2 gas. The heating of carbon dioxide gas to 37 degrees C in the heating tube of the WISAP-Flow-Therme will not only reduce intra-operative hypothermia (down to 28 degrees C intra-abdominally and 34 degrees C in the rectum) but also the occurrence of tachycardia (reduced by 40% to 11%). Heating will also result in reduced CO2 consumption, which is also of ecological significance. As a result of the overall improvement of the female patients' perception of pain there is a significant reduction in postoperative palliative medication required by 31%. The physical laws and data permit fitting the WISAP Universal Flow Therme to all commercially available CO2 gas insufflators. The rinse water, as an additional factor causing hypothermia, should be preheated to 40 degrees C (WISAP water bath).
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PMID:[Pain reduction after pelvi/-laparoscopic interventions by insufflation of CO2 gas at body temperature (Flow-Therme)]. 760 73

1. Effects of moderate hypercapnia (10% CO2) on rectal temperature, oxygen consumption and body weight loss were examined during and after acute hypothermia induced by cold and helium-oxygen. 2. Hypothermia induction time was reduced significantly by hypercapnia. Rewarming tended to be faster in hypercapnic animals than in normocapnic animals. 3. Hypercapnia significantly reduced body weight loss when measured during hypothermia and during normothermia after rewarming. 4. Oxygen consumption during cooling was decreased by hypercapnia. 5. Exposure to 10% CO2 during cooling may spare energy substrate and favor survival in hypothermia.
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PMID:Effects of moderate hypercapnia on hypothermia induced by cold He-O2 in rats. 809 75


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