Hypoxia‐induced Vasoconstriction in Isolated Perfused Lungs exposed to Injectable or Inhalation Anesthetics

Abstract

Investigations during the last two decades have revealed a tendency to inpaired pulmonary gas exchange in patients during general anesthesia. In the awake state, arterial hypoxemia is counteracted by a mechanism which tends to normalize the ventilation/perfusion ratio of the lungs by way of a hypoxia-induced vasoconstriction in poorly ventilated areas. This results in a redistribution of perfusion to more adequately ventilated lung regions. Recent observations suggest, however, that this beneficial mechanism is blunted by some commonly used inhalation anesthetics. In the present study the effect of inhalation anesthetics and injectable anesthetics on the vasoconstrictor response to acute alveolar hypoxia have been compared in isolated blood-perfused rat lungs. The experiments showed that the response was unaffected by N2O and injectable anesthetics, while a reversible, dose-dependent damping effect was demonstrated for the volatile inhalation anesthetics, ether, halothane and methoxyflurance. The effect could be demonstrated at blood concentrations comparable to those used in clinical anesthesia, and it was not due to a general paralysis of the vascular smooth muscle. The findings might, at least in part, explain the occurrence of arterial hypoxemia during general inhalation anesthesia.

Changes inPetCO2 and pulmonary blood flow after bronchial occlusion in dogs

“…However, following bronchial, balloon deflation, the atelectatic lung failed to re-expand and therefore the left pulmonary artery blood flow and PaO 2 did not return to baseline values.14 Finally, our primary anaesthetic agent, pentobarbital, was infused in similar amounts through the experiment and has not been found to independently alter hypoxic pulmonary vasoconstriction. 16 …”

General Pharmacology and Neuropharmacology of Benzodiazepine Derivatives

“…The vasoconstrictor response induced by hypoxia in isolated blood-perfused rat lungs was unaffected by diazepam ('" 2 X 10-6 mol· 1-., BJERTNAES, 1977). Using the perfused rat mesenteric artery preparation, ALLY et aI.…”

Chloralose Alters Both Basal Hemodynamics and Cardiovascular Responses to Alveolar Hypoxia in Chronically Instrumented, Spontaneously Breathing Lambs'

“…Previous studies regarding the effects of anesthesia on hypoxic pulmonary vasoconstriction have concentrated on evaluating the effects of inhalational anesthetic agents (29)(30)(31)(32). The influence of intravascular anesthetic agents on hypoxic pulmonary vasoconstriction has been infrequently studied (32)(33)(34). With rare exception (35), these studies are complicated by premedication using other anesthetic or analgesic agents and, therefore, have no conscious control state.…”

“…No study has investigated the influence of chloralose on the pulmonary circulation. Previous studies regarding the effects of anesthesia on hypoxic pulmonary vasoconstriction have concentrated on evaluating the effects of inhalational anesthetic agents (29)(30)(31)(32). The influence of intravascular anesthetic agents on hypoxic pulmonary vasoconstriction has been infrequently studied (32)(33)(34).…”