Nalbuphine analgesia preserves ventilation after thoracotomy despite a reduction in inspiratory drive.
The respiratory effects of analgesia with nalbuphine were studied in 9 patients after thoracotomy. The pain score was measured by a visual analogue scale. Ventilatory pattern and occlusion pressure (P0.1) were studied during spontaneous breathing and during CO2 rebreathing, before and 0.5, 1, 2.5, 3.5 and 6 h after a 0.3-mg.kg-1 dose of intravenous nalbuphine. Compared to baseline values obtained before the injection, nalbuphine produced a decrease in the pain score (p < 0.001) during the 6-hour experiment period. In spontaneous breathing, P.01 was reduced by 15% in 1 h and remained decreased during 3.5 h (p < 0.05), whilst PaCO2 and ventilation (VE) remained unchanged. The P0.1 responsiveness to CO2 was decreased from 0.5 to 2.5 h after the nalbuphine injection (p < 0.05), but the VE responsiveness to CO2 was reduced only after 1 h (p < 0.01). This study shows that, while post-thoracotomy pain was reduced by analgesia, neuromuscular inspiratory drive and chemosensitivity to CO2 were weakened, without any change in spontaneous ventilation. A partial improvement in the thoracopulmonary mechanics induced by the reduction in chest pain could explain the maintenance of ventilatory level in spite of a decreased neuromuscular inspiratory drive.
Hannhart
B
B
Unité de Recherche de Physiopathologie respiratoire, INSERM U-14, Vandoeuvre-lès-Nancy, France.
Boulanger
G
G
Audibert
G
G
Laxenaire
M C
MC
D000704:Analysis of Variance; D002245:Carbon Dioxide / Q000097:blood; D006801:Humans; D008875:Middle Aged; D009266:Nalbuphine / Q000494:pharmacology* / Q000627:therapeutic use; D010100:Oxygen / Q000097:blood; D010149:Postoperative Pain / Q000188:drug therapy*; D011312:Pressure; D012119:Respiration / Q000187:drug effects*; D013908:Thoracotomy
D002245:Carbon Dioxide; D009266:Nalbuphine; D010100:Oxygen