Evaluation of postoperative respiratory function by serial blood gas analysis in dogs treated with transdermal fentanyl

Abstract

Objective: To perform blood gas analysis of the respiratory response to transdermal fentanyl in dogs which have experienced an open-chest surgical procedure. Design: Prospective trial. Setting: Veterinary Teaching Hospital Surgical Research and Student Laboratory. Intervention: Dogs were purchased for a surgical laboratory. Students performed a cranial abdominal exploratory and diaphragmatic hernia repair. Sixteen dogs were divided into 2 groups. Dogs received transdermal fentanyl (group F), using an average dose of 4.8 mg/kg/hr, applied to the caudal-lateral abdomen 22 hours before surgery, or intravenous buprenorphine (group B; 0.02 mg/kg) given 1 hour prior to anesthetic induction and every 6 hours postoperatively. All dogs received intravenous acepromazine (0.05 mg/kg) preoperatively and every 6 hours postoperatively. Dogs were instrumented with carotid artery catheters. Measurements and main results: Arterial blood gas values were analyzed every 2 hours postoperatively. Plasma fentanyl levels were analyzed every 4 hours postoperatively. The mean carbon dioxide tension (PCO 2 ) did not exceed 45 mmHg in either group. The range in mean PCO 2 levels was 32.9 (+ 3.4)À38.1 (+ 3.9) in group B and 34.7 (+ 3.25)À43.6 (+ 5.5) in group F. At 2 time points, the mean PCO 2 was significantly lower in group B compared with normal levels in group F. Hypoxemia occurred in both the groups. The range in mean oxygen tension (PO 2 ) was 76.5 (+ 18.3)À91.1 (+ 16.3) in group B and 76.0 (+ 10.8)À96.6 (+ 7.6) in group F. There was no significant difference in PO 2 between groups. Levels of fentanyl considered to be analgesic were maintained for the postoperative period. Conclusions: The use of a relatively high dose of transdermal fentanyl did not induce postoperative hypoventilation as evidenced by serial arterial blood gas analysis in this model. (J Vet Emerg Crit Care 2002; 12(2): 81±87)

The post-operative analgesic effects of epidurally administered morphine and transdermal fentanyl patch after ovariohysterectomy in dogs

“…In contrast, other researchers evaluated arterial blood gases and reported that neither fentanyl patches nor epidural morphine induced hypoventilation (Welch et al 2002;Acosta et al 2005). In our study, although respiratory function was not thoroughly investigated, f R never decreased below the reference range of 18-34 breaths minute )1 in either group during the study period.…”

Naloxone reversal of an overdose of a novel, long‐acting transdermal fentanyl solution in laboratory Beagles

“…Respiratory rate, oxygen consumption, and blood gases (pCO2, pO2, and pH) do not change further as concentrations increase above 100 ng/mL. Another study of fentanyl in dogs using a transdermal patch confirmed by blood gas analysis that sustained steady‐state plasma fentanyl concentrations of approximately 2 ng/mL do not cause hypoventilation (Welch et al. , 2002).…”

Preoperative assessment

“…The dose range is 2-5 g/kg/h. Increasing the patch size did not increase the plasma fentanyl concentration in one study but did in a second (Egger et al, 1998;Welch et al, 2002a). The analgesic effect provided by fentanyl in dogs is equivalent to that provided by intramuscular oxymorphone and is often superior to epidural morphine; in cats it is superior to butorphanol Robinson et al, 1999;Franks et al, 2000).…”

“…Respiratory depression can be a serious side-effect in humans but was not seen in dogs at high doses (5 g/kg/h) following thoracotomy (Welch et al, 2002a). Caution should be used in dogs that are hypoventilating due to head or spinal cord injury (see Chapter 15).…”