Anesthesia and analgesia
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Anesthesia and analgesia · Sep 2002
Case ReportsUnsolicited paresthesias with nerve stimulator: case reports of four patients.
Unsolicited paresthesias may occur when a nerve stimulator is used and may indicate valid proximity to the nerve. This phenomenon suggests that nerve stimulator use does not protect against unplanned direct contact with peripheral nerves during performance of a nerve block on an obtunded patient.
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Anesthesia and analgesia · Sep 2002
The pharmacokinetics and tolerability of an intravenous infusion of the new hydroxyethyl starch 130/0.4 (6%, 500 mL) in mild-to-severe renal impairment.
Hydroxyethyl starches (HES) are almost exclusively excreted glomerularly, in part after hydrolysis by amylase. HES 130/0.4 (Voluven; Fresenius Kabi Deutschland GmbH, Bad Homburg, Germany) was developed to improve pharmacokinetics whereas preserving the efficacy of volume effect. We studied the dependency of pharmacokinetics of HES 130/0.4 on renal function. Nineteen volunteers with stable, non-anuric renal dysfunction, ranging from almost normal creatinine clearance (CL(cr)) to severe renal impairment (mean CL(cr): 50.6 mL. min(-1). 1.73 m(-2)), were given a single infusion of 500 mL 6% HES 130/0.4 over 30 min. HES plasma concentrations were determined until 72 h, urinary excretion until 72-96 h. CL(cr) had been obtained at least twice before and twice after dosing. Standard pharmacokinetic calculations and regression analysis were performed. Area under the time concentration curve (AUC(0-inf)) clearly depended on renal function comparing subjects with CL(cr) < 50 with those with CL(cr) > or =50 (ratio 1.73). Peak concentration (C(max), 4.34 mg/mL) as well as terminal half-life (16.1 h, model independent) were not affected by renal impairment. At CL(cr) > or =30, 59% of the drug could be retrieved in urine, versus 51% at CL(cr) 15-<30. The mean molecular weight of HES in plasma was 62,704 d at 30 min, showing lower values with increased renal impairment (P = 0.04). Pre-dose amylase concentrations inversely correlated with baseline CL(cr). Residual HES plasma concentrations after 24 h were small in all subjects (< or =0.6 mg/mL). We conclude that HES 130/0.4 (500 mL 6%) can be safely administered to patients even with severe renal impairment, as long as urine flow is preserved, without plasma accumulation. ⋯ Dependency of the pharmacokinetics of hydroxyethyl starch 130/0.4 on renal function was studied. The area under the time concentration curve increased moderately with more severe renal dysfunction; however, small plasma concentrations were observed after 24 h. Terminal half-life and peak concentration remained unaffected by renal impairment.
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Anesthesia and analgesia · Sep 2002
The prediction of defibrillation outcome using a new combination of mean frequency and amplitude in porcine models of cardiac arrest.
We estimated the predictive power with respect to defibrillation outcome of ventricular fibrillation (VF) mean frequency (FREQ), mean peak-to-trough amplitude (AMPL), and their combination. We examined VF electrocardiogram signals of 64 pigs from 4 different cardiac arrest models with different durations of untreated VF, different durations of cardiopulmonary resuscitation, and use of different drugs (epinephrine, vasopressin, N-nitro-L-arginine methyl ester, or saline placebo). The frequency domain was restricted to the range from 4.33 to 30 Hz. In the 10-s epoch between 20 and 10 s before the first defibrillation shock, FREQ and AMPL were estimated. We introduced the survival index (SI; 0.68 Hz(-1). FREQ + 12.69 mV(-1). AMPL) by use of multiple logistic regression. Kruskal-Wallis nonparametric one-way analysis was used to analyze the different porcine models for significant difference. The variables FREQ, AMPL, and SI were compared with defibrillation outcome by means of univariate logistic regression and receiver operating characteristic curves. SI increased predictive power compared with AMPL or FREQ alone, resulting in 89% sensitivity and 86% specificity. The probabilities of predicting defibrillation outcome for FREQ, AMPL, and SI were 0.85, 0.89 and 0.90, respectively. FREQ, AMPL, and SI values were not sensitive in regard to the four different cardiac arrest models but were significantly different for vasopressin and epinephrine animals. ⋯ We present a retrospective data analysis to evaluate the predictive power of different ventricular fibrillation electrocardiogram variables in pigs with respect to defibrillation outcome. We showed that our combination of variables leads to an improved forecast, which may help to reduce harmful unsuccessful defibrillation attempts.
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Anesthesia and analgesia · Sep 2002
Randomized Controlled Trial Clinical TrialThe effect of clonidine on the minimum local analgesic concentration of epidural ropivacaine during labor.
On the basis of the determination of minimum local analgesic concentration (MLAC), ropivacaine has been demonstrated to be less potent than bupivacaine during the first stage of labor. In this study we assessed the effect of clonidine on the MLAC of ropivacaine. Seventy-seven parturients of mixed parity requesting epidural analgesia for labor (cervical dilation, 3-7 cm) were included in the study. They received an epidural bolus of either ropivacaine (n = 30), ropivacaine plus clonidine 30 microg (n = 28), or ropivacaine plus clonidine 60 microg (n = 19) in the second part of the study. The concentration of the ropivacaine solution was determined by the response of the previous parturient in that group by using an up-down sequential allocation. A visual analog pain score of < or =10 mm within 30 min after the epidural bolus (20 mL) was considered an effective response. An effective result directed a 0.01% wt/vol decrement for the next patient. An ineffective result directed a 0.01% wt/vol increment. The MLAC of ropivacaine was 0.097% wt/vol (95% confidence interval, 0.085%-0.108%). It was unaffected by a 30-microg dose of epidural clonidine (0.081% [0.045%-0.117%]) but was significantly decreased by a 60-microg clonidine dose (0.035% [0.024%-0.046%]) (P < 0.001). This study documents a decrease in the MLAC of ropivacaine by clonidine, significant for a 60- microg dose. ⋯ Epidural ropivacaine potency in labor can be increased by the addition of epidural clonidine. This study demonstrates that 60 microg of epidural clonidine significantly decreases the minimum local analgesic concentration of ropivacaine during the first stage of labor but is associated with sedation.