Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2006
Randomized Controlled Trial Comparative StudyMiddle ear pressure changes during anesthesia with or without nitrous oxide are similar among airway devices.
We tested the hypothesis that middle ear pressure (MEP) is influenced by the choice of airway device during anesthesia with or without nitrous oxide (N2O) in the gas mixture. Eighty consecutive anesthetized, paralyzed ventilated patients (ASA physical status I-II, 18-65 yr) were randomly allocated for airway management with the orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, or laryngeal tube suction with or without N2O 66% in the gas mixture. MEP was measured from both ears in random order by a blinded observer before induction of anesthesia and every 10 min for 70 min. ⋯ MEP was unchanged in the air groups but increased in the N2O groups with N2O (P < 0.0001) and decreased with air (P < 0.02). Baseline values for MEP were similar, but MEP was always higher for the N2O groups (P < 0.001). We conclude that the choice of airway device does not influence MEP among orally inserted tracheal tube, classic laryngeal mask airway, ProSeal laryngeal mask airway, and laryngeal tube suction during anesthesia with or without N2O in the gas mixture.
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Anesthesia and analgesia · Jan 2006
Comparative StudyTotal knee arthroplasty as an overnight-stay procedure using continuous femoral nerve blocks at home: a prospective feasibility study.
The average duration of hospitalization after total knee arthroplasty (TKA) in the United States is 4-5 days. In this two-phase study we investigated the feasibility of converting TKA into an overnight-stay procedure using a continuous femoral nerve block provided at home through postoperative day 4. ⋯ Pain was well controlled, opioid requirements and sleep disturbances were minimal, and patient satisfaction was high. Additional research is required to replicate these results in a controlled trial, define the appropriate subset of patients, and assess the incidence of complications associated with this practice before its mainstream use.
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Anesthesia and analgesia · Jan 2006
Comparative StudyA comparison of state and response entropy versus bispectral index values during the perioperative period.
Cerebral monitoring indices are associated with a large degree of inter-patient variability and electrical signal interference during surgery. We designed this clinical study to test the hypothesis that use of the spectral entropy (Entropy) module is associated with less frequent intraoperative interference with the displayed indices than the bispectral index (BIS) monitor when used during general anesthesia with propofol and desflurane. Thirty consenting patients scheduled for major laparoscopic surgery procedures were enrolled in this prospective study. ⋯ During the maintenance period, the responses to changes in propofol and desflurane concentrations were consistent with all three indices. Finally, the entropy indices were less interfered with by the electrocautery unit during the operation (12% versus 62% for the BIS monitor). Because the average selling prices of the Entropy and BIS disposable electrode strips (14.25 dollars versus 14.95 dollars USD, respectively) are comparable, we conclude that the Entropy module is a cost-equivalent alternative to the BIS monitor.
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Anesthesia and analgesia · Jan 2006
Comparative StudyThe effects of sevoflurane and propofol on QT interval and heterologously expressed human ether-a-go-go related gene currents in Xenopus oocytes.
Sevoflurane can induce prolongation of the cardiac QT interval by inhibiting the repolarization phase of the action potential. This may occur as a result of inhibition of the human ether-a-go-go related gene (HERG) channel. To clarify the mechanisms of anesthetics on HERG channels, we monitored the electrocardiogram and measured QT intervals in the guinea pig in the presence of sevoflurane and propofol. ⋯ The time constant of the converging current was decreased in the presence of sevoflurane, but the inactivation and activation curves were not shifted. Propofol did not affect these currents within the clinically relevant concentration. In conclusion, compared with steady-state currents, sevoflurane was more potent in inhibiting the outward tail currents, suggesting that sevoflurane may modulate the HERG channel kinetics in its inactivated state.
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Anesthesia and analgesia · Jan 2006
Randomized Controlled Trial Comparative StudyThe analgesic effect of tramadol after intravenous injection in healthy volunteers in relation to CYP2D6.
Tramadol analgesia results from a monoaminergic effect by tramadol itself and an opioid effect of its metabolite (+)-M1 formed by O-demethylation of tramadol by CYP2D6. In this study we sought to determine the impact of (+)-M1 on the analgesic effect of tramadol evaluated by experimental pain models. The effect of an IV injection of 100 mg tramadol on experimental pain was studied 15-90 min after dosing in volunteers, 10 extensive metabolizers with CYP2D6 and 10 poor metabolizers without CYP2D6 in 2 placebo-controlled trials. ⋯ In extensive metabolizers, tramadol reduced discomfort experienced during the cold pressor test (P = 0.002). In poor metabolizers, the pain tolerance thresholds to sural nerve stimulation were increased (P = 0.04). (+)-M1 could be detected in the serum samples from all extensive metabolizers except one, but (+)-M1 was below the limit of determination in all poor metabolizers. The opioid effect of (+)-M1 appears to contribute to the analgesic effect of tramadol, but the monoaminergic effect of tramadol itself seems to create an analgesic effect.