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%).
Pain relief with regional analgesia in patients previously treated with opioids increases the incidence of abnormal respiratory events associated with oxygen desaturation.
A specific technique for detection of pulmonary aspiration during the perioperative period is lacking. In this study, we developed a scintigraphic method for its diagnosis. Technetium 99m sulphur ...colloid was given orally 2 h before an i.v. infusion of propofol in patients undergoing elective colonoscopy. During the procedure, patients were spontaneously breathing 100% oxygen via a face mask. After recovery from anaesthesia, patients had a chest scinti-scan. As a control group, 10 healthy men were studied. The lung scan was considered positive if any tracer activity greater than background level was detected in the lung field. Among 96 patients studied, three patients had a positive chest scinti-scan. One of the three patients developed pneumonia while the other two remained asymptomatic. In none of the control asymptomatic group was tracer detected in the chest. We suggest that this technique is specific and can be used as a tool to assess the risk of pulmonary aspiration during different anaesthetic procedures.
Mivacurium is potentiated by pancuronium to a much greater extent than other relaxants. In a previous investigation we suggested that this potentiation could be due to the ability of pancuronium to ...inhibit plasma cholinesterase activity, but we did not measure plasma concentrations of mivacurium. In the current study we performed a pharmacokinetic analysis by measuring the plasma concentration of mivacurium when preceded by administration of a low dose of pancuronium.
After induction of general anesthesia with propofol and fentanyl and orotracheal intubation, 10 patients (pancuronium-mivacurium group) received 15 microg/kg pancuronium followed 3 min later by 0.1 mg/kg mivacurium, whereas 10 other patients (mivacurium group) received saline followed by 0.13 mg/kg mivacurium 3 min later. Plasma cholinesterase activity was measured before and 3 and 30 min after pancuronium dosing in the pancuronium-mivacurium group and was measured before and after administration of saline in the mivacurium group. Arterial plasma concentrations of mivacurium and its metabolites were measured at 0.5, 1, 1.5, 2, 4, 10, 20, and 30 min after injection. Neuromuscular blockade was assessed by mechanomyography.
Plasma cholinesterase activity decreased by 26% in the pancuronium-mivacurium group 3 min after injection of pancuronium (P < 0.01) and returned to baseline values 30 min later; however, no significant variation was observed in the mivacurium group. The clearances of the two most active isomers (Cis-Trans and Trans-Trans) were lower in the pancuronium-mivacurium group (17.6 +/- 5.1, 14.7 +/- 5.3 ml. min-1. kg-1, respectively) than in the mivacurium group (32.4 +/- 20.2, 24.8 +/- 13.5 ml. min-1. kg-1; P < 0.05).
A subparalyzing dose of pancuronium decreased plasma cholinesterase activity and the clearance of the two most active isomers of mivacurium. Pancuronium potentiates mivacurium more than other neuromuscular blocking agents because, in addition to its occupancy of postsynaptic acetylcholine receptors, it slows down the hydrolysis of mivacurium.
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