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

Three postoperative analgesic protocols were assigned randomly to 24 healthy dogs after thoracotomy at the left fourth intercostal space. Morphine was administered parenterally to eight dogs after tracheal extubation; selective intercostal nerve blocks with bupivacaine hydrochloride and epinephrine were administered to eight dogs before closure of the thorax; and bupivacaine hydrochloride and epinephrine were administered through an interpleural catheter to eight dogs after tracheal extubation. Heart rate, respiratory rate, rectal temperature, hematocrit, plasma protein, blood gas, and pain score evaluations were recorded before surgery and 30 minutes, 1 hour, 2 hours, and 3 hours after extubation. Morphine caused significant decreases in blood pH and blood oxygen tensions, and significant increases in carbon dioxide tensions. Dogs treated with intercostal nerve blocks had no significant changes in these parameters, and dogs treated with interpleural bupivacaine had significant decreases in blood oxygen tension. All dogs had significant decreases in rectal temperature, and hypothermia was prolonged after morphine. Analgesia was initially adequate in most dogs, but some dogs in each treatment group had recurrence of pain and were treated with interpleural bupivacaine. One dog developed pneumothorax. Interpleural administration of bupivacaine produced analgesia equal to that produced by systemic administration of morphine or selective intercostal nerve block with bupivacaine. Bupivacaine was easily readministered through an interpleural catheter. Respiratory compromise was less in dogs treated with bupivacaine than in dogs treated with morphine. After intercostal thoracotomy, interpleural bupivacaine provided prolonged analgesia with fewer blood gas alterations than morphine.
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PMID:Analgesia in dogs after intercostal thoracotomy. A comparison of morphine, selective intercostal nerve block, and interpleural regional analgesia with bupivacaine. 190 Nov 83

High concentrations of bupivacaine and profound hypothermia individually cause intraventricular conduction disturbances and reentrant arrhythmias. The effects of the combination of relatively low concentrations of bupivacaine and mild hypothermia are unknown and are the subject of this study. Three groups (n = 10-12) of dogs anesthetized with thiopental-chloralose were treated as follows: group 1, bupivacaine + hypothermia; group 2, bupivacaine alone; group 3, hypothermia alone. Bupivacaine was administered as a 4 mg/kg iv bolus followed by an iv infusion of 0.1 mg.kg-1.min-1. Hypothermia, i.e., a 4 degrees C reduction in core temperature, was produced by cooling the blood with an extracorporeal circuit. The peripheral ECG was recorded to determine the duration of QRS complexes and the QT interval. Conduction time and effective refractory period (ERP) of ventricular contractile tissue were measured with right ventricular endocavitary electrodes. Measurements were made with the heart paced at 180 beats/min and without pacing. In group 1 dogs, bupivacaine (plasma level, 2.8 +/- 0.3 microgram/ml) initially caused a prolongation of conduction time and QRS duration, which were further lengthened (approximately doubled) by a temperature decrease of 4 degrees C from baseline. The QT interval and ERP also were increased but to a lesser degree. In dogs in which the effects were most pronounced, rhythm disorders, such as wave burst arrhythmias (most common), premature systoles, ventricular tachycardia, and even ventricular fibrillation, occurred either spontaneously or during pacing. Bupivacaine alone (group 2) increased QRS duration and conduction time significantly, whereas hypothermia alone (Group 3) did not cause changes in any conduction variables. In neither group were dysrhythmias observed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Potentiation by mild hypothermia of ventricular conduction disturbances and reentrant arrhythmias induced by bupivacaine in dogs. 271 14

Cardiac disorders are observed when excessive plasma concentrations of local anaesthetics are reached, following for instance intravascular accidental injection for epidural anaesthesia or brachial plexus block. Bupivacaine particularly, which is one of the most used local anaesthetics, adversely affects intraventricular conduction and cardiac contractile strength from the 3.0-4.0 micrograms/ml blood levels. Depression of conduction is especially to be feared, for it can result in reentrant arrhythmias likely to degenerate into often fatal ventricular fibrillation. Such accidents may sometimes occur at far lower concentrations, subsequent to diffusion into systemic circulation from the injection site (0.4-1.2 micrograms/ml). These accidents were probably due to various factors which concomitantly intervene during the anaesthesia. We could identify a number of these factors by associating them to an intravenous infusion of bupivacaine (0.04 mg/kg/min after a loading dose of 1.00 mg/kg) in animals (dogs and pigs) under electrocardiographic monitoring, in which conduction time, monophasic action potential duration, effective refractory period and electrical fibrillation threshold were determined in the ventricular fibres. The electrophysiological changes due to bupivacaine may be enhanced by 1) dilution hyponatremia (115-110 mmol/l) induced by a short (5 min) intravenous 10 ml/kg/min infusion of hypotonic solution and/or hyperkalemia (7-8 mmol/l) induced by 0.05 mmol/kg/min infusion of potassium chloride; 2) the acceleration of cardiac contractions (180-210 beats/min) induced by ventricular pacing; 3) mild hypothermia (35-34 degrees C) induced by blood cooling in an extracorporeal circuit; 4) myocardial ischaemia induced by complete temporary occlusion of the left anterior descending coronary artery near its origin. The risk of cardiac accidents, possibly severe, is therefore enhanced by each of these factors capable of lowering the concentration required for their triggering and, of course, the combination of two or several of them. On the contrary, the knowledge of these factors should allow to prevent most of cardiac accidents of locoregional anaesthesia.
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PMID:[Cardiac accidents of locoregional anesthesia: experimental study of risk factors with bupivacaine]. 964 39