Comparison between facemask and laryngeal mask airway in rabbits during isoflurane anesthesia.
OBJECTIVE
To determine whether a laryngeal mask airway (LMA) provides a better airway than a facemask in spontaneously breathing anesthetized rabbits, and to test if it can be used for mechanically controlled ventilation.


METHODS
Randomized prospective experimental trial.


METHODS
Sixteen young, healthy, specific pathogen-free Giant Flemish cross Chinchilla rabbits (10 females and 6 males) weighing 4.1 +/- 0.8 kg.


METHODS
Rabbits were assigned randomly to one of three treatment groups: facemask with spontaneous ventilation (FM-SV; n = 5), LMA with spontaneous ventilation (LMA-SV; n = 5), and LMA with controlled ventilation (LMA-CV; n = 6). In dorsal recumbency, and at 2.3% end-tidal isoflurane concentration, Fé isoflurane, Fi isoflurane, partial pressure of expired isoflurane (PECO(2)), partial pressure of inspired carbon dioxide (PiCO(2)), heart rate, respiratory rate, minute volume, arterial oxygen tensions (PaO(2)), arterial carbon dioxide tensions (PaCO(2)), arterial pH (pH(a)), arterial standard base excess (SBE(a)) values were measured for 120 minutes. Results Two individuals in the FM-SV group had PaCO(2) > 100 mm Hg. One rabbit in the FM-SV had PaO(2) < 80 mm Hg. All FM-SV rabbits showed signs of airway obstruction, and two were withdrawn from the study at 45 and 90 minutes, respectively, because cyanosis was observed. No signs of airway obstruction were observed in either LMA group. Four rabbits in the LMA-CV group developed gastric tympanism, one of which refluxed gastric contents after 110 minutes. There were no differences between FM-SV and LMA-SV in any variable tested. PaCO(2) and PECO(2) were decreased, while PaO(2) and minute volume were increased in the LMA-CV group compared to the LMA-SV group.


CONCLUSIONS
An LMA provided a better airway than a facemask during spontaneous breathing in rabbits, as the use of a facemask was associated with hypercapnia and low partial pressures of oxygen. Although an LMA can be used for intermittent positive pressure ventilation (IPPV), gastric tympanism may develop, especially at a peak inspiratory pressure of 14 cm H(2)O.


CONCLUSIONS
The LMA can be used in rabbits but further work is needed before it is applied routinely.
Bateman
Leigh
L
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY, USA.
Ludders
John W
JW
Gleed
Robin D
RD
Erb
Hollis N
HN
D000768:Anesthesia, General / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage; D000818:Animals; D000830:Animals, Laboratory / Q000502:physiology*; D005260:Female; D006439:Hemodynamics; D007530:Isoflurane / Q000008:administration & dosage; D017214:Laryngeal Masks / Q000662:veterinary; D008297:Male; D008397:Masks / Q000662:veterinary*; D011446:Prospective Studies; D011817:Rabbits / Q000502:physiology*; D013047:Specific Pathogen-Free Organisms; D016896:Treatment Outcome
D018685:Anesthetics, Inhalation; D007530:Isoflurane