Some cardiopulmonary effects of midazolam premedication in clenbuterol-treated bitches during surgical endoscopic examination of the uterus and ovariohysterectomy

Abstract

Midazolam was administered intravenously to 8 bitches in a randomised, placebo-controlled clinical trial before propofol induction of surgical anaesthesia. Anaesthesia was maintained with isoflurane-in-oxygen during surgical endoscopic examination of the uterus and ovariohysterectomy. Clenbuterol was administered at the start of surgery to improve uterine muscle relaxation, and to facilitate endoscopic examination of the uterus. Ventilation was controlled. Induction of anaesthesia with propofol to obtain loss of the pedal reflex resulted in a statistically significant (P < 0.05) decrease in minute volume and arterial oxygen partial pressure in the midazolam group. Apnoea also occurred in 50 % of dogs in the midazolam group. The dose for propofol in the midazolam group was 7.4 mg/kg compared to 9.5 mg/kg in the control. Minute volume was significantly (P < 0.05) higher in both groups during isoflurane maintenance, compared to the value after incremental propofol to obtain loss of the pedal reflex. Propofol induction resulted in a 25-26 % reduction in the mean arterial blood pressure in both groups, and the administration of clenbuterol at the start of surgery resulted in a transient, but statistically significant (P < 0.05), decrease in mean arterial blood pressure in the midazolam group during isoflurane anaesthesia. It is concluded that intravenous midazolam premedication did not adversely affect cardiovascular function during propofol induction, but intra-operative clenbuterol during isoflurane maintenance of anaesthesia may result in transient hypotension. Midazolam premedication may increase adverse respiratory effects when administered before propofol induction of anaesthesia

Some clinical effects of midazolam premedication in propofol-induced and isoflurane-maintained anaesthesia in dogs during ovariohysterectomy

“…In this investigation, a 37 % reduction in the anaesthetic dose (loss of pedal reflex) for propofol was obtained. Apnoea occurred only in the midazolam group 20 , and might indicate increased respiratory depression despite the reduction in the propofol dose. The effect on the dose for hypnosis was not evaluated.…”

“…This agent may significantly influence cardiopulmonary function 3,7 , and transient changes in arterial blood pressure were observed during this investigation. The effects of clenbuterol on cardiopulmonary function during this investigation have been reported elsewhere 20 . The purpose of this paper was to report on the influence of midazolam premedication on the dose required for propofol induction and isoflurane maintenance of anaesthesia in dogs during surgery.…”

Effects of altering the sequence of midazolam and propofol during co‐induction of anaesthesia

“…Since propofol was administered at low doses and to effect to allow intubation, it is possible that the lower doses used in the MP and PM groups were not sufficient to inhibit this sympathetic response. Conversely, propofol has been shown to increase heart rate within the first 5 min of induction in goats that were not intubated and in dogs before intubation (Stegmann & Bester ; Madan et al. ).…”

Preliminary investigation into the ventilatory effects of midazolam in isoflurane-anaesthetised goats

“…9 In dogs, apnoea occurs after premedication with MDZ and induction of anaesthesia with propofol. 10 The intravenous administration of MDZ to conscious goats results in a decrease in V E and arterial oxygen tension. 10 Therefore, the pre-anaesthetic use of MDZ possibly may result in increased ventilatory depression during maintenance of anaesthesia with isoflurane.…”

“…10 The intravenous administration of MDZ to conscious goats results in a decrease in V E and arterial oxygen tension. 10 Therefore, the pre-anaesthetic use of MDZ possibly may result in increased ventilatory depression during maintenance of anaesthesia with isoflurane. This investigation is a preliminary investigation into the ventilatory effects of MDZ in goats during isoflurane anaesthesia.…”