The effects of residual pain on oxygenation and breathing pattern during morphine analgesia.
To determine the influence of pain on opioid-induced respiratory depression, we studied oxygenation and breathing patterns in 40 patients scheduled for knee surgery during postoperative patient-controlled analgesia (PCA). After 1 h of morphine PCA, patients were randomized to receive either 20 mL of placebo or bupivacaine 0.25% through a crural nerve catheter and allowed to use PCA for one more hour. Abnormal breathing events were identified and characterized by using the Edentrace II device (Nellcor, Jouy-en-Josas, France). The Spo2 below which the patient spent 25% and 50% of a studied period was calculated (Spo2(25), Spo2(50)). Pain relief with regional analgesia increased the incidence of abnormal respiratory events associated with oxygen desaturation: during the second period, the pain score was lower in the bupivacaine group (0.7+/-1 vs 4.1+/-1.2), morphine consumption was larger in the placebo group (4.2+/-1.3 vs 0.7+/-1.4 mg), and there were more abnormal obstructive breathing events in the bupivacaine group (11+/-16 vs 3.7+/-4.3). Spo2(25) and Spo2(50) were lower in the bupivacaine than in placebo group (91.5%+/-2.8% vs 93.1%+/-2.1%, 92.9%+/-2.4% vs 94.2%+/-1.8%).


CONCLUSIONS
Pain relief with regional analgesia in patients previously treated with opioids increases the incidence of abnormal respiratory events associated with oxygen desaturation.
Combes
X
X
Department of Anesthesia, Hôpital Henri Mondor, Créteil, France.
Cerf
C
C
Bouleau
D
D
Duvaldestin
P
P
Dhonneur
G
G
D016058:Analgesia, Patient-Controlled; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D000765:Anesthesia, Conduction / Q000009:adverse effects; D000779:Anesthetics, Local / Q000009:adverse effects; D002045:Bupivacaine / Q000009:adverse effects; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007717:Knee / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000627:therapeutic use*; D010100:Oxygen / Q000097:blood*; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy; D011446:Prospective Studies; D015656:Respiratory Mechanics / Q000187:drug effects* / Q000502:physiology*
D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D009020:Morphine; D010100:Oxygen; D002045:Bupivacaine