Anesthesiology
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The effects of topical application of local anesthetics on peripheral nerve blood flow (NBF) were studied in the rat sciatic nerve. Sciatic NBF was measured by laser doppler in 45 adult female Sprague-Dawley rats (90 nerves) after topical application of 25 microliter lidocaine and epinephrine, alone and in combination (lidocaine plus epinephrine), as well as bupivacaine, tetracaine, and normal saline, and studied in a randomized, blinded experimental design. NBF changes produced by lidocaine were dose-dependent. ⋯ Epinephrine 5.0 micrograms/ml and epinephrine 10.0 micrograms/ml produced reductions of 20% and 35%, respectively (P less than 0.05), which lasted throughout the study. The effects of each of the three concentrations were significantly different from the others. The combination of lidocaine plus epinephrine resulted in synergistic reduction of NBF for all drug concentrations (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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Airway obstruction plays an important role in the pathogenesis of apnea in premature infants who have not previously undergone anesthesia. To determine the role of airway obstruction in postoperative apnea, we studied 74 former premature infants by integrated recordings of nasal airflow, pneumocardiography, and pulse oximetry during the initial 2 h of recovery from inhalational anesthesia. Apnea (greater than 6 s) was classified as central, obstructive, or mixed, wherein mixed apnea consisted of central and obstructive apnea within the same apneic episode. ⋯ Arterial hemoglobin desaturation was significantly more frequent at the end of mixed and obstructive apnea than after central apnea (P less than 0.01). In both groups, arterial hemoglobin O2 saturation (SpO2) decreased to less than 80% in approximately 35% of mixed and obstructive apneic episodes, compared to approximately 5% of central apneic episodes. SpO2 remained greater than or equal to 90% in over 80% of central apneic episodes, compared to 40% of mixed and obstructive apneic episodes.(ABSTRACT TRUNCATED AT 250 WORDS)
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Ropivacaine is a new amide local anesthetic structurally related to bupivacaine and mepivacaine. Its potency and duration of action are similar to those of bupivacaine but its therapeutic index may be greater. Since pregnancy enhances the cardiotoxicity of bupivacaine, the current study was devised to compare the toxicity of ropivacaine in chronically instrumented nonpregnant and pregnant ewes during continuous intravenous infusion of the drug at the rate of 0.5 mg.kg-1.min-1. ⋯ For example, circulatory collapse occurred at a mean dose of 11.3 +/- 1.1 mg.kg-1 in nonpregnant and 12.4 +/- 0.9 mg.kg-1 in pregnant animals, with corresponding plasma concentrations of 7.3 +/- 0.3 and 9.6 +/- 2.1 micrograms.ml-1 (P = not significant). Protein binding of ropivacaine in the concentration range associated with toxic manifestations was similar in sera obtained from nonpregnant and pregnant ewes. In conclusion, ovine pregnancy does not enhance the systemic toxicity of ropivacaine, possibly because of an absence of gestation-related increase in the availability of free drug.
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Randomized Controlled Trial Comparative Study Clinical Trial
A comparison of the analgesic and respiratory effects of epidural nalbuphine or morphine in postthoracotomy patients.
This randomized, double-blind study compared the analgesic and respiratory effects of lumbar epidural morphine 5 mg, nalbuphine 10 mg, and nalbuphine 20 mg in repeated doses in patients after thoracotomy; the first dose was administered intraoperatively. Pre-and postoperative monitoring included continuous pulse oximetry, respiratory inductance plethysmography, and repeated arterial blood gas analysis. Postoperatively, visual analogue pain scores, somnolence scores, respiratory rate, and arterial blood gases were determined for 16 h. ⋯ Two patients who received morphine had persistently increased PaCO2 postoperatively. Two patients who received morphine had episodes of apnea and slow respiratory rate, which were most frequent 6 h after arrival in the recovery room. We conclude that lumbar epidural nalbuphine does not provide adequate analgesia after thoracotomy.(ABSTRACT TRUNCATED AT 250 WORDS)