Objective—To determine the cardiovascular and respiratory
effects of water immersion in horses recovering
from general anesthesia.
Animals—6 healthy adult horses.
Procedure—Horses were anesthetized 3 times with
halothane and recovered from anesthesia while positioned
in lateral or sternal recumbency in a padded
recovery stall or while immersed in a hydropool.
Cardiovascular and pulmonary functions were monitored
before and during anesthesia and during recovery
until horses were standing. Measurements and
calculated variables included carotid and pulmonary
arterial blood pressures (ABP and PAP, respectively),
cardiac output, heart and respiratory rates, arterial
and mixed venous blood gases, minute ventilation,
end expiratory transpulmonary pressure (PendXes),
maximal change in transpulmonary pressure
(ΔPtpmax), total pulmonary resistance (RL), dynamic
compliance (Cdyn), and work of breathing ().
Results—Immersion in water during recovery from
general anesthesia resulted in values of ABP, PAP, PendXes, ΔPtpmax, RL, and that were significantly greater and values of Cdyn that were significantly less,
compared with values obtained during recovery in a padded stall. Mode of recovery had no significant
effect on any other measured or calculated variable.
Conclusions and Clinical Relevance—Differences in
pulmonary and cardiovascular function between horses
during recovery from anesthesia while immersed
in water and in a padded recovery stall were attributed
to the increased effort needed to overcome the
extrathoracic hydrostatic effects of immersion. The
combined effect of increased extrathoracic pressure
and PAP may contribute to an increased incidence of
pulmonary edema in horses during anesthetic recovery
in a hydropool. (Am J Vet Res 2001;62:1903–1910)