Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialThe effects on resting ventilation of intravenous infusions of morphine or sameridine, a novel molecule with both local anesthetic and opioid properties.
Sameridine has both local anesthetic and partial mu-opioid receptor agonistic properties. The aim of this single-blinded, randomized, three-way cross-over study of 12 subjects was to investigate the effects on resting ventilation of two doses of sameridine: 0.15 mg/kg (S-Small) and 0.73 mg/kg (S-Large) compared with 0.10 mg/kg morphine. Each drug was infused IV over 20 min. Ventilation was measured by pneumotachography and in-line capnography, and sedation was rated by the subjects using a visual analog scale (VAS). Plasma was collected and analyzed for sameridine and morphine. At the end of drug infusion, minute ventilation (VE) and tidal volume (VT) were reduced in the S-Large group, and VE was reduced in the morphine group. End-tidal CO2 increased in both groups (P < 0.05), but respiratory rates remained unchanged. In the S-Small group, no ventilatory changes were recorded. In the S-Large group, the median sedation score was 6.8 cm with corresponding values in the morphine and S-Small groups of 3.3 and 2.5 cm, respectively. There was a relationship between the plasma concentration of sameridine and the depression of ventilation. We conclude that sameridine influences resting ventilation and that this effect is directly related to plasma concentrations of sameridine. From a ventilatory aspect, a clinical dose of sameridine with both local anesthetic and opioid properties seems safe. ⋯ Sameridine, a molecule with both local anesthetic and analgesic properties, impaired resting ventilation after a large IV dose (0.73 mg/kg), more so than 0.10 mg/kg IV morphine. A clinical dose of sameridine (0.15 mg/kg) did not have any effects on ventilation.
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Anesthesia and analgesia · Jan 1999
Randomized Controlled Trial Clinical TrialConcentration of lidocaine affects intensity of sensory block during lumbar epidural anesthesia.
We investigated the effects of a twofold difference in concentration and volume of lidocaine on lumbar epidural block using a cutaneous current perception threshold (CPT) quantitative sensory testing device. Twenty ASA I patients scheduled for elective gynecological surgery were randomly divided into two equal groups to receive either 20 mL of 1% lidocaine or 10 mL of 2% lidocaine through an epidural catheter inserted at the L1-2 interspace. CPTs at 2000-, 250-, and 5-Hz stimulation and sensation to light touch, temperature, and pinprick at ipsilateral dermatomes V, T9, and L2 were measured before and every 5 min until 60 min after the epidural lidocaine. Epidural anesthesia with both solutions produced a significant increase in all CPTs at dermatomes T9 and L2. Alterations in CPTs were similar for both groups at T9 but were significantly greater in patients given 2% lidocaine than in those given 1% lidocaine at L2. There were no differences in the upper level of sensory block to cold, pinprick, and touch between the two groups. We conclude that lumbar epidural anesthesia with 10 mL of 2% lidocaine produces more intense blockade of both large- and small-diameter sensory nerve fibers than that with 20 mL of 1% lidocaine. ⋯ The effects of local anesthetic concentration and volume on the quality of epidural anesthesia have not been adequately investigated. The results of the present study suggest that the concentration affects the intensity of sensory block during epidural anesthesia with lidocaine.
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Anesthesia and analgesia · Jan 1999
Clinical TrialCapnography monitoring during neurosurgery: reliability in relation to various intraoperative positions.
In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment. ⋯ This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.
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Anesthesia and analgesia · Jan 1999
Comparative StudyA comparison of the effects of propofol and sevoflurane on the systemic toxicity of intravenous bupivacaine in rats.
We compared the effects of propofol and sevoflurane on bupivacaine-induced central nervous system and cardiovascular toxicity in rats. Thirty-four male Sprague-Dawley rats were anesthetized with 70% N2O/30% O2 plus the 50% effective dose (ED50) of propofol (propofol group, n = 12); 70% N2O/30% O2 plus ED50 of sevoflurane (sevoflurane group, n = 11); or 70% N2O/30% O2 (control group, n = 11). Bupivacaine was infused at a constant rate of 2 mg x kg(-1) x min(-1) while electrocardiogram, electroencephalogram, and invasive arterial pressure were continuously monitored. The cumulative doses of bupivacaine that induced dysrhythmias, seizures, and 50% reduction of heart rate were larger in the propofol and sevoflurane groups than in the control group. The cumulative dose of bupivacaine that induced a 50% reduction in the mean arterial blood pressure was larger in the propofol group than in the sevoflurane and control groups. The margin of safety, assessed by the time between the onset of dysrhythmias and 50% reduction of mean arterial blood pressure, was wider in the propofol group than in the sevoflurane group. We conclude that propofol and sevoflurane attenuate bupivacaine-induced dysrhythmias and seizures and that propofol has a wider margin of safety than sevoflurane. ⋯ In anesthetized patients, dysrhythmias may be the only warning sign of intravascular injection of bupivacaine. Because propofol has a wider margin of safety than sevoflurane, life-threatening cardiovascular depression may be prevented by stopping the injection of bupivacaine at the onset of dysrhythmias during propofol anesthesia.
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Anesthesia and analgesia · Jan 1999
Clinical TrialCommon peroneal nerve stimulation for neuromuscular monitoring: evaluation in awake volunteers and anesthetized patients.
The study was conducted in two parts. First, evoked responses to common peroneal nerve stimulation at four electrode positions were tested in 25 awake volunteers. The initial threshold stimulus current (ITS) (minimal current producing dorsiflexion or eversion of the ankle joint and great toe) and the supramaximal stimulus current (SMS) (the point at which further increases in current did not produce increases in twitch tension) were defined. SMS was not reliably achieved using electrodes at each side of the fibular head. However, an exploratory electrode accurately located the nerve and enabled SMS in all volunteers (SMS/ITS = 3.4). Second, 16 anesthetized, paralyzed patients were studied. The common peroneal and ulnar nerves were stimulated simultaneously. Evoked tension was recorded at the adductor pollicis using a force transducer and at the great toe by a blinded observer. Reversal was given when the train-of-four count at the great toe reached four. Onset times were longer, and median posttetanic counts were greater, at the great toe compared with the adductor pollicis. Time from reversal to train-of-four ratio = 0.7 at the adductor pollicis was 207+/-160 s. We conclude that neuromuscular monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve. ⋯ Accurate neuromuscular monitoring is important for patient safety. We studied the accuracy of monitoring at the common peroneal nerve in volunteers and patients. An exploratory electrode accurately located the common peroneal nerve. Monitoring at the common peroneal nerve was not equivalent to monitoring at the ulnar nerve in patients.