Recovery of Ventilation After Anesthesia for Laparoscopic Nephrectomy

The purpose of this study is characterize pharmacologically induced ventilatory depression after anesthesia and examine how is affected by the amount of supplemental oxygen patients are receiving in the immediate postoperative period, since hyperoxemia (ie., higher than necessary partial pressure of oxygen in the arterial blood) has been associated with ventilatory depression via suppression of the hypoxic ventilatory drive.

In this feasibility randomized controlled trial, the investigators plan to estimate and compare the cumulative segment of time during which the transcutaneous partial pressure of carbon dioxide will exceed an upper limit of 45 mmHg (i.e., TcPCO2 > 45 mmHg) for the 90-min-long post-anesthesia period, between the conventional (titrated to an oxygen saturation > 96%) and the conservative (titrated to O2 saturation 90 -94%) O2 supplementation interventions.

Hypothesis: Conservative use of O2 (titrated to an SpO2: 90 - 94%), will be associated with less hypoventilation (i.e., less time spent with an TcPCO2 > 45 mmHg) during recovery from general anesthesia, compared to liberal O2 supplementation (SpO2 > 96%).

Inclusion criteria

• American Society of Anesthesiologists (ASA) physical status I-III
• Body mass index (BMI) less than 40 kg/m2
• Scheduled to undergo robotic-assisted radical laparoscopic nephrectomy.

Exclusion criteria

• Patients with a diagnosis of chronic obstructive pulmonary disorder (COPD), severe neurological, cardiopulmonary, psychiatric, or untreated thyroid disorder
• Chronic pain condition that is being treated with opioids
• Patients with a hematocrit lower than 30% at the end of surgery, or those with an excessive blood loss, requiring transfusion of blood products during their surgery, will be also excluded from the study.