Laparoscopic-induced pneumoperitoneum does not impair oxygenation in large-breed dogs but worsens hypercapnia, which is improved by low positive end-expiratory pressure ventilation.

OBJECTIVE

To evaluate whether laparoscopic-induced pneumoperitoneum (8 to 10 mm Hg) in reverse Trendelenburg (RT) impairs ventilation and oxygenation, and whether pressure-controlled ventilation (PCV) with low positive end-expiratory pressure (PEEP; 3 cm H2O [PEEP-3] or 5 cm H2O [PEEP-5]) improves these variables in sevoflurane-anesthetized large-breed dogs.

METHODS

Cardiopulmonary variables were recorded before (T0) and 15 minutes after insufflation in RT (T1) during spontaneous ventilation (SV) and again 45 minutes after initiating PCV (T2) using 20 breaths/min, an inspiratory-to-expiratory ratio of 1:2, PEEP-3 or PEEP-5, and peak inspiratory pressure (PIP) starting at 10 or 12 cm H2O, respectively, with 2-cm H2O increments every 5 minutes until end-tidal CO2 reached 35 to 40 mm Hg or PIP reached 20 cm H2O. The final dataset was collected 5 minutes after desufflation on PCV (T3).

RESULTS

During SV, pneumoperitoneum worsened Paco2 (median [range]; PEEP-3, 70.0 mm Hg [62.0 to 86.1 mm Hg]; PEEP-5, 72.0 mm Hg [61.0 to 81.9 mm Hg]) and plasma pH (mean ± SD; PEEP-3, 7.18 ± 0.04; PEEP-5, 7.18 ± 0.02). During PCV, after titrating PIP (median, 16 and 18 cm H2O, respectively), these variables improved, but in PEEP-5, pH remained lower (mean ± SD; 7.36 ± 0.03 vs 7.32 ± 0.04), and dead space-to-tidal volume higher (median [range]; 9.4% [2.2% to 16.1%] vs 16.2% [7.0% to 34.0%]). Oxygenation was unaffected, and cardiovascular changes and interventions were similar between groups.

CONCLUSIONS

During SV, pneumoperitoneum in RT worsened hypercapnia and acidemia without impairing oxygenation. During PCV, PEEP-3 provided the best respiratory outcome.

CLINICAL RELEVANCE: Low PEEP-3 PCV improves pneumoperitoneum-induced hypoventilation in large-breed dogs without oxygenation impairment, whereas PEEP-5 may be limited by PIP.