Effects of dexmedetomidine on oxygenation during one-lung ventilation for thoracic surgery in adults

To evaluate the effects of dexmedetomidine on hypoxic pulmonary vasoconstriction (HPV) and oxygenation during one-lung ventilation (OLV) in adults undergoing thoracic surgery.

Prospective, randomized, double-blinded trial.

Tertiary care, University-based hospital.

Nineteen adult patients undergoing thoracic surgery requiring OLV.

During inhalational anesthesia with desflurane, patients were randomized to receive either dexmedetomidine (bolus dose of 0.3 μg/kg followed by an infusion of 0.3 μg/kg/hr) or saline placebo.

Three arterial blood gas samples (ABG) were obtained to evaluate the effects of dexmedetomidine on oxygenation. Secondary outcomes included differences in hemodynamic parameters (heart rate and mean arterial pressure), end-tidal desflurane concentration required to maintain the bispectral index (BIS) at 40-60, supplemental fentanyl to maintain hemodynamic stability, and phenylephrine to keep the mean arterial pressure (MAP) within 10% of baseline values.

Oxygenation during OLV did not change following the administration of dexmedetomidine (PaO2/FiO2 ratio of 188 ± 115 in dexmedetomidine patients versus 135 ± 70 mmHg in placebo patients). There were no differences in hemodynamic variables or depth of anaesthesia between the two groups. With the administration of dexmedetomidine, there was a decrease in the expired concentration of desflurane required to maintain the BIS at 40-60 when compared with the control group (4.5 ± 0.8% versus 5.1 ± 0.8%). In patients receiving dexmedetomidine, fentanyl requirements were decreased when compared to placebo (2.7 μg/kg/patient versus 3.1 μg/kg/patient). However, more patients receiving dexmedetomidine required phenylephrine to maintain hemodynamic stability (6 of 9 patients versus 3 of 10 patients) and the total dose of phenylephrine was greater in patients receiving dexmedetomidine when compared with placebo 10.3 μg/kg/patient versus 1.1 μg/kg/patient).

Dexmedetomidine does not adversely affect oxygenation during OLV in adults undergoing thoracic surgical procedures. The improvement in oxygenation in the dexmedetomidine patients may be related to a decrease in the requirements for inhalational anaesthetic agents thereby limiting its effects on HPV.