Healthy nonobese bitches maintain acceptable spontaneous ventilation during laparoscopic ovariectomies

To determine whether end-tidal CO2 (Petco2), tidal volume (Vt), inspiratory minute volume (V.i), and respiratory rate (RR) remain within reference limits for spontaneously breathing dogs undergoing laparoscopic ovariectomy; characterize changes in these variables over time; and record the proportion of dogs requiring mechanical ventilation on the basis of predetermined criteria.

22 client-owned dogs.

Between January and June 2019, dogs were anesthetized for abdominal insufflation (CO2; 10 mm Hg) and laparoscopic ovariectomy. Respiratory variables (Petco2, Vt, V.i, and RR) were recorded at 5 time points: preinsufflation (T2), immediately after insufflation (T3), immediately after first ovary extraction (T4), immediately after second ovary extraction (T5), and after abdominal deflation (T6). Results for variables were assessed to identify differences with reference limits and between time points.

At all time points (T2 to T6), Petco2 was within or above the reference limit, Vt was below or within reference limits, and V.i was either within or above reference limits. Significant temporal changes were detected in all recorded parameters. One dog had to be ventilated prior to abdominal insufflation due to inappropriately low Vt (< 6 mL/kg) and was excluded from further analysis. One of the 21 remaining dogs required rescue ventilation.

Following insufflation, there was a tendency toward inadequate ventilation over time characterized by increased Petco2. Twenty of 21 dogs maintained Petco2 within tolerance via a mild increase in RR and did not require assisted ventilation. Dogs undergoing short surgeries may not require assisted ventilation. Clinicians are advised to monitor for hypercapnia and be prepared to assist ventilation if required.