Evaluation of gastric and bladder tonometry as indicators of tissue perfusion in induced hypotension in dogs.

OBJECTIVE: To evaluate the use of gastric (PgCO2 ) and bladder (PbCO2 ) tonometry for assessing tissue hypoperfusion in dogs during sevoflurane-induced hypotension, and to compare these measurements with delivery of oxygen, arterial oxygen content, and plasma lactate concentration.

DESIGN: Prospective experimental trial.

SETTING: University veterinary teaching hospital.

ANIMALS: Fourteen adult Beagle dogs.

INTERVENTIONS: Anesthetic induction was performed by mask with sevoflurane and oxygen. Heart rate, direct arterial pressures, respiratory rate, and end-tidal carbon dioxide were recorded; arterial blood samples were taken to measure blood gases, and venous samples were sampled to measure plasma lactate. A tonometric catheter was introduced into the stomach to measure PgCO2 . Samples of saline from the balloon of a Foley catheter placed in the bladder were collected every 10 minutes and used to measure PbCO2 by gas analysis. Tonometry measurements, plasma lactate, and oxygen delivery and consumption were compared at 3 time points: at baseline, during hypotension, and during treatment periods. A hypotensive period (mean arterial pressure (MAP) < 60 mm Hg) of 15 minutes was induced by an overdose of sevoflurane, whereas during the treatment period, a constant-rate infusion of dopamine (10 μg/kg/min) was administered intravenously for 40 minutes.

MEASUREMENTS AND MAIN RESULTS: Values for PgCO2 and PbCO2 increased significantly during the hypotensive period, and correlations were found between these values and the delivery of oxygen. Gastric tonometry values had stronger correlations compared with bladder tonometry values.

CONCLUSIONS: Gastric and bladder tonometry can be used to detect hypoperfusion. Further studies are warranted to determine the potential use of gastric and bladder tonometry in assessing dogs in clinical situations.