Endotracheal tubes versus laryngeal mask airways in rabbit inhalation anesthesia: ease of use and waste gas emissions

Abstract

In this study, we compared two endotracheal tubes (cuffed [Murphy Eye type] and uncuffed [Cole type]) and a pediatric laryngeal mask airway (LMA) with respect to their ease of use in rabbits and their capacities to limit waste isoflurane emissions. Animals (New Zealand White, 3.3 to 5.0 kg, n = 8) were sedated with intramuscular ketamine (50 mg/kg) and xylazine (10 mg/kg). After 5 min, the larynx was numbed with cetocaine, an intubation device was positioned, and anesthesia was maintained with isoflurane (2%) in oxygen (1 liter/min). Real-time atmospheric isoflurane emissions were assessed at the rabbit's oral commissure and in the operator's breathing zone (45 cm from the rabbit's nose) by using a portable infrared spectrophotometer. The LMA was placed more easily than was either endotracheal tube, especially by novices. The cuffed tube was positioned more readily than was the uncuffed variant. All three devices emitted isoflurane. The concentrations measured at the oral commissure for the LMA (mean +/- standard error, 8.4 +/- 0.6 ppm) were modestly higher than those acquired for the cuffed (6.7 +/- 0.5 ppm) and uncuffed (6.3 +/- 0.4 ppm) endotracheal tubes; the difference between the LMA and uncuffed tube was significant (P = 0.012). Isoflurane was not detected in the operator's breathing zone. These data show that the uncuffed endotracheal tube (usually used to anesthetize birds and reptiles) and the pediatric LMA can be used in rabbits as readily as a cuffed tube. In addition, our findings indicate that tradeoffs will be required in selecting a delivery system for this species, as the easiest apparatus (the LMA) also emits the most isoflurane waste.