Studies on the halothane-diethyl-ether azeotrope
1994 (English)Doctoral thesis, comprehensive summary (Other academic)
Requirements for a safe standard for anaesthesia under primitiveconditions differ from those under peaceful circumstances. It is important not to blunt the reflexes that guard vital functions. Safety requirements concerning breathing, circulation, and drug interaction must be sharpened because professional surveillance of the patient may be restricted. The halothane-diethyl-ether azeotrope (HE azeotrope) has properties that could make it suitable for anaesthesia under adverse circumstances. We have re-evaluated the HE azeotrope with special reference to safety in studies on 102 patients and 19 pigs.
The vaporizers were calibrated to guarantee their performance. Guidelines for the use of Auotec® Mark Ill and Servo® vaporizer for halothane combined with the HE azeotrope are set out. Minimum alveolar concentration (MAC) for the HE azeotrope has not previously been published. The MAC for the HE azeotrope was determined in man (0.71 vol.%± 0.03, ± SEM) and pig (0.99 vol.%± 0.07) to allow comparison with other inhalation anaesthetics. The safety ratio defined as the ratio between fatal alveolar concentration and minimum alveolar concentration was found to be 3.1 in pig, which is about twice as high as previously reported data for halothane anaesthesia alone.
Ventilation during surgical anaesthesia (1.1-1.2 MAC), both when resting and during challenge with raised inspiratory levels of carbon dioxide and decreased inspiratory concentration of oxygen, was measured. Ventilation was maintained during resting. Response to hypercarbia was preserved, in contrast to what was seen under isoflurane anaesthesia. Response to hypoxia was abolished.
The central circulation was well preserved under normovolaemia in pigs during HE azeotrope anaesthesia. Haemorrhage. with a loss of30% of the blood volume was well tolerated, no matter whether the pig had received HE azeotrope or isoflurane. Isoflurane is considered in the literature to be an anaesthetic well tolerated by pigs.
Most inhalation anaesthetics potentiate neuromuscular blockade, which is an important and sometimes dangerous component of anaesthesia. We therefore thought it important to investigate whether interaction takes place between vecuronium induced neuromuscular blockade and the HE azeotrope. Potentiation similar to that occurring during halothane anaesthesia was found.
Early postoperative liver function was studied by tests of cellular metabolic capacity, cell integrity, cholestasis, and synthesizing capacity. No major impact on hepatic function after HE azeotrope anaesthesia was seen.
Thus, the halothane-diethyl-ether azeotrope has properties that could make it interesting as an alternative anaesthetic drug under difficult circumstances.
Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 1994. , 37 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 417
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-27504Local ID: 12159ISBN: 91-7871-260-2OAI: oai:DiVA.org:liu-27504DiVA: diva2:248056
1994-04-29, Berzeliussalen, Universitetssjukhuset, Linköping, 09:00 (Swedish)
Papers, included in the Ph.D. thesis, are not registered and included in the posts from 1999 and backwards.2009-10-082009-10-082012-07-25Bibliographically approved