Different Effects of Halothane and Enflurane on Diaphragmatic Contractility In Vivo

Abstract

We examined the effects of halothane and enflurane on diaphragmatic contractility in 12 anesthetized, mechanically ventilated dogs. The diaphragmatic force was assessed from transdiaphragmatic pressure (Pdi) developed at functional residual capacity against an occluded airway during cervical phrenic nerve stimulation. Animals were randomly assigned to two groups, a halothane group (n = 6) and an enflurane group (n = 6). The Pdi stimulus-frequency relationship was compared at anesthetic levels of 1, 1.5, and 2 MAC (minimum alveolar concentration) in each group. The sequence of changing anesthetic concentration was randomized. In addition, the Pdi-frequency relationship was also compared between 1 MAC of halothane and enflurane in 8 of 12 dogs. In animals anesthetized with enflurane, Pdi significantly decreased with 50- and 100-Hz stimulation in the presence of increasing MAC values, whereas Pdi at 10-Hz stimulation was not affected by the depth of anesthesia. Pdi with 20-Hz stimulation during 2 MAC enflurane also decreased significantly below Pdi levels seen at 1 and 1.5 MAC. By contrast, with halothane there was no difference in Pdi at any of the stimulation frequencies during any of the three levels of anesthesia. There was no statistical difference, however, between Pdi-frequency relationships during 1 MAC of halothane and enflurane in eight animals. From these results, we conclude that halothane does not impair diaphragmatic contractility any more than enflurane does, but enflurane decreases force generation of the diaphragm at high stimulation frequencies in a dose-related fashion. This depressant effect of enflurane occurs mainly through the impairment of neuromuscular transmission and/or membrane excitability.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of propofol on airway pressures generated by magnetic stimulation of the phrenic nerves

“…A study in dogs during propofol anaesthesia [17] detected a fall in TwPdi of 10% to 20%. Volatile anaesthetic agents have also been found to reduce diaphragm contractility in some animal studies [18,19,20], but not all [21].…”

The Effect of Four Anaesthetic Protocols for Maintenance of Anaesthesia on Trans-Diaphragmatic Pressure in Dogs

“…The diaphragm is the main inspiratory muscle and contributes to the 2/3 of the actual tidal volume [3], [4]. The effects of many inhalation (enflurane, halothane, isoflurane, sevoflurane) and injectable (propofol, thiopentone) anaesthetics on the respiratory function and more specifically on diaphragmatic contractility have already been studied in animals and humans [5], [6], [7], [8], whereas few data exist on the influence of opioids and methylxanthines [9], [10]. In all these studies, the diaphragmatic contractility was evaluated experimentally by measuring the trans-diaphragmatic pressure (P di ) after electrical stimulation of the phrenic nerves.…”

“…While enflurane depresses diaphragmatic function in a dose-dependent manner, halothane and isoflurane show little effect on it [7], [8], [11], [12] and sevoflurane has an intermediate effect [13], [14]. It has also been shown that halothane depresses P di and the electrical activity of the diaphragm in spontaneously breathing dogs [5].…”

The Recovery Profile of Reduced Diaphragmatic Contractility Induced by Propofol in Dogs

“…The favorable recovery profile associated with propofol offers advantages over traditional anesthetic and sedative medications in clinical situations (1). Like volatile anesthetics (halothane, enflurane, isoflurane, and sevoflurane) (2)(3)(4)(5), propofol decreases contractility in nonfatigued and fatigued diaphragm (6,7). No studies have been reported evaluating the recovery from reduced diaphragmatic contractility caused by propofol.…”