Pharmacological Treatment of Hypoxemia during One-lung Ventilation.

To the Editor: We read with great interest the Case Scenario on hypoxemia during one-lung ventilation (OLV) reported by Rozé et al., and we would like to add some comments on pharmacological treatment. First, the title of the section, “Pharmacological treatment to limit hypoxic pulmonary vasoconstriction,” could, in our opinion, lead to confusion. Almitrine does not limit hypoxic pulmonary vasoconstriction but enhances this mechanism in nonventilated areas. Inhaled nitric oxide can inhibit hypoxic pulmonary vasoconstriction in patients with chronic obstructive pulmonary disease breathing room air; however, during OLV this gas vasodilates ventilated lung areas, shifting the pulmonary blood flow toward these zones without modifying hypoxic pulmonary vasoconstriction. Regarding the use of inhaled nitric oxide, a European board of experts on this topic concluded that there is no evidence to support the routine use of inhaled nitric oxide for the prevention or reversal of hypoxemia during OLV, although some patients with severe hypoxemia may benefit from this drug. On the other hand, the text suggests that inhaled nitric oxide improves hypoxemia only when it is used with positive end-expiratory pressure, but it has also been useful when administered without positive end-expiratory pressure in patients with severe hypoxemia. Concerning almitrine, the hemodynamic effects on pulmonary circulation are dose-related, and pulmonary hypertension is not expected if a low-dose combined with inhaled nitric oxide is used during OLV. Peripheral neuropathy related to almitrine has been observed in patients who received this drug for several months, usually with complete recovery, and is related to high plasma concentrations of almitrine (400 ng/ml). However, when low-dose almitrine is administered for a short time its plasma concentration is less than the concentration seen with long-term therapy and returns to values close to zero within 12 h after cessation of the infusion. Almitrine and inhaled nitric should not be used routinely. Nevertheless, they can dramatically improve oxygenation and thus might be considered as alternative treatments when other strategies fail to improve hypoxemia during OLV.