Anesthesia and analgesia
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Anesthesia and analgesia · Jan 1998
The inhibitory effects of thiopental, midazolam, and ketamine on human neutrophil functions.
We investigated the effect of thiopental, midazolam, and ketamine (at clinically relevant concentrations and at 0.1 and 10 times these concentrations) on several aspects of human neutrophil functions. The three intravenous (i.v.) anesthetics significantly decreased chemotaxis, phagocytosis, and reactive oxygen species (ROS) (O2-, H2O2, OH) production of neutrophils in a dose-dependent manner. At clinically relevant concentrations, thiopental and midazolam significantly depressed these neutrophil functions. However, ketamine at the clinical plasma concentration did not impair chemotaxis or ROS production, except phagocytosis. In contrast, the three anesthetics had no effect on the levels of ROS production by a cell-free ROS generating system. In addition, intracellular calcium concentrations in neutrophils stimulated by N-formyl-L-methionyl-L-leucil-L-phenylalanine were dose-dependently decreased in the presence of each of the three anesthetics. The suppression of an increase in intracellular calcium concentrations may be responsible for the inhibition of neutrophil functions by the i.v. anesthetics. ⋯ Neutrophils play an important role in the antibacterial host defense system and autotissue injury. We found that thiopental and midazolam (but not ketamine), at clinically relevant concentrations, impaired the neutrophil functions.
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Anesthesia and analgesia · Jan 1998
Meta AnalysisDoes acute normovolemic hemodilution reduce perioperative allogeneic transfusion? A meta-analysis. The International Study of Perioperative Transfusion.
The objective of this study was to systematically review the literature and to statistically summarize the evidence evaluating acute normovolemic hemodilution (ANH). Prospective, randomized, controlled trials of ANH that reported either the proportion of patients exposed to allogeneic blood or the units of allogeneic blood transfused were included. All types and languages of publication were eligible. Of 1573 identified publications, 24 trials (containing a total of 1218 patients) were included in the meta-analysis. When all trials were pooled, ANH reduced the likelihood of exposure to allogeneic blood (odds ratio [OR] 0.31, 95% confidence interval [CI] 0.15, 0.62) and the total units of allogeneic blood transfused (weighted mean difference [WMD] -2.22 U, 95% CI -3.57, -0.86). However, there was marked heterogeneity of the results. In trials using a protocol to guide perioperative transfusion, ANH failed to reduce either the likelihood of transfusion (OR 0.64, 95% CI 0.31, 1.31) or the units administered (WMD -0.25 U, 95% CI -0.60, 0.10). Adverse events were incompletely reported. It is possible that biased experimental design is, in part, responsible for the reported efficacy of this technique. ⋯ after a systematic literature review, 24 randomized trials examining the role of acute normovolemic hemodilution were identified, pooled, and summarized using statistical techniques. Many studies reported an impressive reduction in blood transfused. Closer examination suggests that these reductions in blood exposure may be due to flawed study design.
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Anesthesia and analgesia · Jan 1998
Randomized Controlled Trial Clinical TrialThe efficacy and safety of a clonidine/bupivacaine combination in caudal blockade for pediatric hernia repair.
We evaluated the analgesic efficacy and hemodynamic and respiratory safety of clonidine when added to bupivacaine for caudal blocks in 58 children aged 38 +/- 2 mo (mean +/- SEM). Patients scheduled for ambulatory hernia repair were randomly given a caudal injection (0.75 mL/kg) of either saline placebo (P group), bupivacaine, 0.25% (B group), bupivacaine plus epinephrine 1:200,000 (BE group), bupivacaine plus clonidine 1 microgram/kg (BC1 group), or bupivacaine plus clonidine 2 micrograms/kg (BC2 group). Postoperative measurements included duration of analgesia, hemodynamics, and respiratory monitoring for 6 h. Thereafter, parents assessed their child's analgesic requirements at home every 3 h for 18 h. The duration of analgesia (median [range]) was significantly longer (P < 0.05) in the BC1 and BC2 groups (360 [270-360] min and 360 [355-360] min, respectively) compared with the P (77[45-190]), B (346[105-360]), or BE group (300[75-360]). Similarly, the BC1 and BC2 groups required less additional analgesic within the first 24 h. All groups showed a significant decrease in mean arterial pressure compared with baseline values, but the differences among the groups were not significant. Bradycardia and respiratory depression were not observed. Clonidine 1 and 2 micrograms/kg can be safely added to bupivacaine caudal blockade in small children for ambulatory hernia repair to achieve an increased duration of analgesia compared with bupivacaine alone or bupivacaine plus epinephrine. ⋯ The addition of clonidine, an antihypertensive drug with analgesic properties, to local anesthetics in caudal blocks prolongs postoperative pain relief and reduces the need for additional pain treatment in children after hernia operation.
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Anesthesia and analgesia · Jan 1998
Randomized Controlled Trial Clinical TrialTracheal intubation in ambulatory surgery patients: using remifentanil and propofol without muscle relaxants.
Using alfentanil followed by an anesthetic induction dose of propofol provides adequate conditions for tracheal intubation without neuromuscular relaxants. Remifentanil, which has a clinical onset similar to that of alfentanil, has not been investigated for this indication. Accordingly, 80 ASA physical status I and II premedicated outpatients were randomly assigned to one of four groups (n = 20/group). Remifentanil 1, 2, 3, or 4 micrograms/kg (Groups I-IV, respectively) was infused intravenously over 90 s. Sixty seconds after beginning the remifentanil infusion, propofol 2 mg/kg was infused over 5 s. Ninety seconds after the administration of propofol, laryngoscopy and tracheal intubation were attempted and graded. Clinically acceptable intubating conditions (i.e., jaw relaxed, vocal cords open, and fewer than two coughs in response to intubation) were observed in 35%, 75%, 100%, and 95% of patients in Groups I-IV, respectively. Clinically acceptable intubating conditions were significantly (P < 0.05) less likely to occur in Group I compared with all other groups. Excellent intubating conditions (i.e., vocal cords open, no movement in response to intubation) were observed in 30%, 50%, 80%, 80% of patients in Groups I-IV, respectively. Overall conditions at intubation were significantly (P < 0.05) better in Groups III and IV compared with Groups I and II. The mean time to resumption of spontaneous ventilation after induction was < 5 min in all groups. No patient manifested clinically significant muscle rigidity. The mean arterial pressure decreased 16%, 20%, 28%, 26% immediately before tracheal intubation in Groups I-IV, respectively. No patient was treated for hypotension or bradycardia. In conclusion, healthy, premedicated patients with favorable airway anatomy can be reliably intubated with good or excellent conditions 90 s after the administration of remifentanil 3-4 micrograms/kg and propofol 2 mg/kg. ⋯ Remifentanil 3 micrograms/kg and propofol 2 mg/kg co-administered intravenously may reliably provide adequate conditions for tracheal intubation in healthy patients without neuromuscular relaxants. This combination of drugs may allow the rapid return of spontaneous ventilation.
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Anesthesia and analgesia · Jan 1998
Randomized Controlled Trial Clinical TrialRecovery from opioid anesthesia: the clinical implication of context-sensitive half-times.
The context-sensitive half-time, the time required for a 50% decrease in drug concentration, has been proposed to predict the speed of recovery after infusions of i.v. anesthetics. We studied 40 patients to compare the clinical recovery characteristics of alfentanil and sufentanil. Patients were randomly allocated to receive either sufentanil/propofol (Group 1) or alfentanil/propofol (Group 2) total i.v. anesthesia by target-controlled infusions (TCI), assuming an equipotency ratio of 500:1. After discontinuation, times to tracheal extubation and to discharge from the postanesthesia care unit were measured, as were drug concentrations up to 24 h. The TCI bias was -17.1% for sufentanil and -16.9% for alfentanil. We found no difference in mean extubation times between the groups (48.7 min in Group 1 versus 46.4 min in Group 2), whereas discharge criteria were fulfilled significantly (P = 0.039) earlier after alfentanil (99.5 min) compared with sufentanil (131.3 min). The relative decrement values to tracheal extubation were 62.1% for sufentanil and 48.0% for alfentanil, compared with 75.7% and 65.0% for discharge, respectively. Based on a difference in propofol requirements, we suggest an actual sufentanil to alfentanil equipotency ratio of 1:300. We conclude that the decay in pharmacodynamic effect is not only the result of pharmacokinetics. ⋯ Computer simulations may help to anticipate the clinical behavior of anesthetic drugs. In a clinical setting, we tested whether the recovery characteristics after i.v. anesthesia could be explained by a pharmaco-kinetic value, which describes the decline of drug concentrations in the body. This was not fully achieved.