Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2002
Meta AnalysisA quantitative, systematic review of randomized controlled trials of ephedrine versus phenylephrine for the management of hypotension during spinal anesthesia for cesarean delivery.
This quantitative systematic review compared the efficacy and safety of ephedrine with phenylephrine for the prevention and treatment of hypotension during spinal anesthesia for cesarean delivery. Seven randomized controlled trials (n = 292) were identified after a systematic search of electronic databases (MEDLINE, EMBASE, The Cochrane Controlled Trials Registry), published articles, and contact with authors. Outcomes assessed were maternal hypotension, hypertension and bradycardia, and neonatal umbilical cord blood pH values and Apgar scores. For the management (prevention and treatment) of maternal hypotension, there was no difference between phenylephrine and ephedrine (relative risk [RR] of 1.00; 95% confidence interval [CI], 0.96-1.06). Maternal bradycardia was more likely to occur with phenylephrine than with ephedrine (RR of 4.79; 95% CI, 1.47-15.60). Women given phenylephrine had neonates with higher umbilical arterial pH values than those given ephedrine (weighted mean difference of 0.03; 95% CI, 0.02-0.04). There was no difference between the two vasopressors in the incidence of true fetal acidosis (umbilical arterial pH value of <7.2; RR of 0.78; 95% CI, 0.16-3.92) or Apgar score of <7 at 1 and 5 min. This systematic review does not support the traditional idea that ephedrine is the preferred choice for the management of maternal hypotension during spinal anesthesia for elective cesarean delivery in healthy, nonlaboring women. ⋯ Phenylephrine and ephedrine to manage hypotension during spinal anesthesia for elective cesarean delivery were compared in this systematic review. Women given ephedrine had neonates with lower umbilical cord blood pH values compared with those given phenylephrine. However, no differences in the incidence of fetal acidosis (pH value of <7.2) or neonatal Apgar scores were found.
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Anesthesia and analgesia · Apr 2002
Randomized Controlled Trial Clinical TrialPerioperative small-dose S(+)-ketamine has no incremental beneficial effects on postoperative pain when standard-practice opioid infusions are used.
Several studies report that when small-dose racemic ketamine, an N-methyl-D-aspartate receptor antagonist, is administered perioperatively, opioid consumption is reduced postoperatively. S(+)-ketamine has a higher affinity for the N-methyl-D-aspartate receptor and less-serious side effects than racemic ketamine. Thirty patients scheduled for elective arthroscopic anterior cruciate ligament repair were enrolled in this randomized, double-blinded clinical trial designed to determine the preemptive effect of S(+)-ketamine on postoperative analgesia requirements in a setting of clinically relevant perioperative analgesia. Total IV anesthesia was induced and maintained with remifentanil (0.125-1.0 microg x kg(-1) x min(-1)) and a propofol target-controlled infusion (target 2-4 microg/mL). The Ketamine group received a bolus of 0.5 mg/kg S(+)-ketamine before incision, followed by a continuing infusion of 2 microg x kg(-1) x min(-1) until 2 h after emergence from anesthesia. The Control group received NaCl in the same sequence. After IV morphine provided pain relief down to < or =3 on a visual analog scale scored from 0 to 10, patients were connected to a patient-controlled analgesia device. There were no significant differences between the two groups in terms of total morphine consumption or VAS scores, either at rest or with movement. In our study, S(+)-ketamine did not contribute to postoperative pain reduction, possibly because of the clinically routine perioperative opioid analgesia. ⋯ Small-dose S(+)-ketamine had no positive effect on postoperative analgesia when administered perioperatively for elective arthroscopic anterior cruciate ligament repair. Unlike investigations of the racemic mixture of ketamine, our study methods included timely standard-practice perioperative opioid analgesia, which seems to make supplemental analgesia unnecessary.
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Anesthesia and analgesia · Apr 2002
The differential effect of halothane and 1,2-dichlorohexafluorocyclobutane on in vitro muscle contractures of patients susceptible to malignant hyperthermia.
Malignant hyperthermia (MH) is an autosomal dominant, potentially fatal pharmacogenetic disorder of skeletal muscle. Approximately half of all known MH families show a linkage to the ryanodine receptor type 1 (RY1) gene. Although our knowledge of the diagnosis, genetics, and therapy of MH has improved, the exact pathogenesis and the role of volatile anesthetics as trigger substances for an MH crisis remain unknown. Compounds that do not obey the Meyer-Overton hypothesis (i.e., nonimmobilizers) are today an important part of research on anesthetic mechanisms. We designed this study to test the hypothesis that the nonimmobilizer 1,2-dichlorohexafluorocyclobutane (2N) compared with halothane has different effects on in vitro muscle contractures of muscle bundles from MH-susceptible (MHS) individuals. In vitro muscle contracture tests were performed with either halothane (approximately 660 microM, equivalent to approximately 4 minimum alveolar anesthetic concentration [MAC]) or 2N ( approximately 100 microM, equivalent to approximately 5 times predicted MAC). MAC is defined as the anesthetic concentration that prevents nocifensive movements after a surgical stimulus in 50% of subjects. In contrast to halothane, 2N caused only minimal muscle contractures in muscle bundles from six MHS patients (0.13 g [0.04-0.31 g] vs 1.95 g [1.60-4.70 g], median values and ranges; P = 0.004). Halothane and 2N differ in their effects on muscle contractures of MHS individuals, possibly because of a differing action on MH RY1. ⋯ Using in vitro contracture tests, we showed that halothane and the nonimmobilizer 1,2-dichlorohexafluorocyclobutane differ in their effects on contractures of muscle bundles from individuals susceptible to malignant hyperthermia (MH) as a result of their differing action on MH ryanodine receptors. These findings render this receptor a possible molecular target for volatile anesthetic action.
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Anesthesia and analgesia · Apr 2002
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of neuromuscular effects, tracheal intubating conditions, and reversibility of rapacuronium versus mivacurium in female patients.
Rapacuronium is a new, rapid-onset, short-duration, nondepolarizing neuromuscular blocking drug. We evaluated the intubating conditions at maximum block after the administration of rapacuronium or mivacurium in female patients undergoing laparoscopy. We also evaluated the neostigmine-induced reversibility of neuromuscular block after this single dose of rapacuronium or mivacurium.
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Anesthesia and analgesia · Apr 2002
Randomized Controlled Trial Clinical TrialIntubating laryngeal mask airway size selection: a randomized triple crossover study in paralyzed, anesthetized male and female adult patients.
We determined the optimal size of intubating laryngeal mask airway (ILM) for ventilation and blind tracheal intubation in men and women. We also determined the distance the tracheal tube needs to protrude beyond the distal aperture to ensure that the cuff is through the vocal cords. Fifty male and 50 female anesthetized, paralyzed patients (ASA physical status I or II, aged 18-80 yr) were studied. Three operators (A, B, and C) were involved for the purposes of blinding. The size 3, 4, or 5 ILM was inserted into each patient in random order by Operator A, and the quality of ventilation was scored (adequate, suboptimal, or failed) by Operator B. The fiberoptic position (correct, too shallow, or too deep) and the distance between the distal aperture and the vocal cords was determined by Operator B. A single attempt at blind intubation was made by Operator C. Operators B and C were blinded to the size of the ILM. Operator C was also blinded to the information recorded by Operator B. All ILMs were inserted into the laryngopharynx at the first attempt. For men and women, the ventilation score was smaller for the Size 3 than the Size 4 or 5 (all: P < 0.002). For men, correct positioning was less common with the Size 3 than the Size 4 or 5 (both: P < 0.02). For women, correct positioning was similar among sizes. For men, tracheal intubation was successful less frequently with the Size 3 (84%) than the Size 4 (100%) or 5 (98%) (both: P < or = 0.01). For women, tracheal intubation success was similar among sizes (Size 3, 4, and 5: 86%, 96%, and 92%, respectively). Intubation was always successful if the ILM was correctly positioned and always failed if it was too shallow or deep. In both male and female patients, the distance between the distal aperture and the vocal cords increased with increasing ILM size (all: P < 0.04) and patient height (P < 0.0001) and was always longer for men (all: P < 0.0001). The overall mean distance (95% confidence interval) that the tracheal tube needed to protrude was 10-12 cm (8-13 cm) in men and 8-11 cm (8-12 cm) in women. We conclude that for men, the Size 4 and 5 ILMs are better than the Size 3 for ventilation and blind intubation. For women, the Size 4 and 5 ILMs are better than the Size 3 for ventilation, but there is no difference among sizes for blind intubation. The length the tracheal tube must protrude from the distal aperture to ensure that the cuff is completely through the vocal cords is 8-13 cm, depending on ILM size, the tracheal tube size, and the sex and height of the patient. ⋯ For men, the Size 4 and 5 intubating laryngeal mask airways are better than the Size 3 for ventilation and blind tracheal intubation. For women, the Size 4 and 5 are better than the Size 3 for ventilation, but there is no difference among sizes for blind intubation. The length the tracheal tube must protrude from the distal aperture of the intubating laryngeal mask airway to ensure that the cuff is completely through the vocal cords is 8-13 cm, depending on the size of the mask and tracheal tube and on the sex and height of the patient.