Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2000
Randomized Controlled Trial Clinical TrialThe 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%). ⋯ Pain relief with regional analgesia in patients previously treated with opioids increases the incidence of abnormal respiratory events associated with oxygen desaturation.
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Anesthesia and analgesia · Jan 2000
The anticonvulsant effects of volatile anesthetics on lidocaine-induced seizures in cats.
Large concentrations of sevoflurane and isoflurane, but not halothane, induce spikes in the electroencephalogram. To elucidate whether these proconvulsant effects affect lidocaine-induced seizures, we compared the effects of sevoflurane, isoflurane, and halothane in cats. Fifty animals were allocated to 1 of 10 groups: 70% nitrous oxide (N2O), 0.6 minimum alveolar anesthetic concentration (MAC) + 70% N2O, 1.5 MAC + 70% N2O, and 1.5 MAC of each volatile agent in oxygen. Lidocaine 4 mg x kg(-1) x min(-1) was infused IV under mechanical ventilation with muscle relaxation. Electroencephalogram in the cortex, amygdala, and hippocampus and multiunit activities in the midbrain reticular formation (R-MUA) were recorded. Lidocaine induced spikes first from the amygdala or hippocampus in the 70% N2O and halothane groups and from the cortex in the sevoflurane and isoflurane groups. Lidocaine induced seizures in all cats in the 70% N2O and 0.6 MAC + N2O groups. Seizure occurrence was reduced in the 1.5 MAC + N2O group (P < 0.05 versus 70% N2O). The onset of seizure was delayed in the 0.6 MAC + N2O and 1.5 MAC groups for sevoflurane and isoflurane, but not for halothane, compared with the 70% N2O group (P < 0.05). Lidocaine increased R-MUA with seizure by 130%+/-56% in the 70% N2O group. The increase of R-MUA with seizure was more suppressed in the volatile anesthetic groups than in the 70% N2O group (P < 0.05). In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased. ⋯ Increasingly, epidural blockade is combined with general anesthesia to achieve stress-free anesthesia and continuous pain relief in the postoperative period. In the present study, sevoflurane and isoflurane attenuated seizure when the blood lidocaine concentration was accidentally increased.