Low- Vs High-dose Almitrine Combined with Nitric Oxide to Prevent Hypoxia During Open-chest One-lung Ventilation

Background: Almitrine combined with inhaled nitric oxide (NO) can prevent hypoxia during one-lung ventilation (OLV). The optimal dose of almitrine that would provide therapeutic advantage with few side-effects during open-chest OLV has not been established.

Methods: Forty-two patients undergoing thoracotomy were randomly allocated to three groups: placebo, almitrine 4 microg kg(-1) min(-1) and inhaled NO 10 p.p.m. (ALM4+NO), and almitrine 16 microg kg(-1) min(-1) and inhaled NO 10 p.p.m. (ALM16+NO). Gas exchange, haemodynamic and respiratory variables and plasma concentrations of almitrine and lactate were monitored. Measurements were obtained with the patient awake (baseline), after induction of anaesthesia with two-lung ventilation (control 2LV), 20 min after treatment (2LV+T), and then at 10, 20 and 30 min of OLV (OLV10', OLV20' and OLV30') with FI(O2)1.

Results: In the placebo group, OLV impaired Pa(O2) and increased pulmonary shunt [16 (SD 7) kPa and 42 (10)% respectively]. These improved with ALM4+NO [26 (10) kPa and 31 (7)%; P<0.001]. ALM16+NO further improved PaO2) to 36 (13) kPa (P<0.0001) but gave no improvement in the shunt. Mean pulmonary artery pressure was similar in the placebo and ALM4+NO groups [20 (4) vs 23 (5) mm Hg], whereas it was increased in the ALM16+NO group to 28 (8) mm Hg (P<0.01). Plasma concentrations of almitrine and lactate were unaltered by the treatments.

Conclusions: Low-dose almitrine (4 microg kg(-1) min(-1)) together with inhaled NO significantly improves oxygenation during open-chest OLV, without modifying pulmonary haemodynamics. An increased dose of almitrine (16 microg kg(-1) min(-1)) with inhaled NO further improves arterial oxygenation, but also increases mean pulmonary artery pressure.