Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialNegative pressure rewarming vs. forced air warming in hypothermic postanesthetic volunteers.
We compared changes in core temperature and systemic heat balance with a new negative pressure/warming device (Vital Heat(R) ) that uses negative pressure combined with heat to facilitate warming in vasoconstricted postoperative patients to those resulting from passive insulation or forced air. Seven healthy volunteers were anesthetized and cooled to a tympanic membrane temperature near 34 degrees C. Anesthesia was discontinued and shivering was prevented by using meperidine. ⋯ Core temperature increased no faster with Vital Heat warming (1.3 +/- 0.4 degrees C) than with a cotton blanket (1.2 +/- 0.4 degrees C). In contrast, core temperature increased more rapidly with forced air warming (2.6 +/- 0.6 degrees C). In this study we show that calories from a negative pressure rewarming device are largely constrained to the forearm and that heat does not flow to the core thermal compartment.
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Anesthesia and analgesia · Jan 2001
Comparative StudyLow preoperative antithrombin activity causes reduced response to heparin in adult but not in infant cardiac-surgical patients.
We evaluated the interaction of preoperative antithrombin (AT) activity and intraoperative response to heparin in cardiac surgery. Heparin anticoagulation is essential during cardiopulmonary bypass (CPB). Heparin itself has no anticoagulant properties, however it causes a conformational change of the physiologic plasma inhibitor AT that converts this slow-acting serine protease inhibitor into a fast acting one. Thus, adequate AT activity is a prerequisite for sufficient heparin anticoagulation. AT activity is reduced by long-term heparin therapy. This prospective, observational study investigated 1516 consecutive cardiac-surgical patients (1304 patients >1 yr (Group A) and 212 patients < or = 1 yr (Group I)). AT activity was measured the day before surgery by a chromogenic substrate assay. The celite-activated activated clotting time (ACT) was used to guide intraoperative heparin administration. Heparin sensitivity was calculated and the postoperative blood loss and perioperative blood requirement was recorded. Infant patients had significantly less preoperative AT activity compared with older patients: 84 (33)% vs 97 (17)%, median (interquartile range) (P < 0. 05). The subgroup of patients aged <1 mo (n = 64) demonstrated a preoperative AT activity of 56 (27)% as compared with 90 (23)% in infant patients between one month and one year (n = 148). In adult patients, preoperative AT activity depended predominantly on preoperative heparin treatment: 62% of the patients with an AT activity <80% were pretreated with heparin. Five minutes after heparin but before CPB the ACT was 587 (334) s in Group A patients with AT activity > or = 80%, and 516 (232) in patients with AT activity < or = 80% (P < 0.05). The target ACT of 480 s was achieved in 70% of patients with normal AT activity in Group A compared with only 54% of patients with AT activity <80% (P < 0.05). In Group A patients with decreased AT activity, 18% demonstrated an inadequate ACT response-defined as ACT <400 s-to the first bolus injection of heparin. In Group I, preoperative AT activity did not influence the ACT response (ACT 5 min after heparin: 846 [447] s in patients with AT activity > or = 80% vs 1000 [364] s in patients with decreased AT activity). The heparin sensitivity was 2.4 (1.1) s/unit heparin/kg compared with 1.5 (0.8) s/unit heparin/KG in group A (P < 0.05). These results suggest that preoperative diminished AT activity causes reduced response to heparin in adult but not in infant patients. Infant patients demonstrate a higher heparin sensitivity despite lower preoperative AT activity. Measurement of preoperative AT activity identifies adult patients at risk of reduced sensitivity to heparin. ⋯ In patients less than one year of age, low antithrombin (AT) activity is caused by the immature coagulation system. Despite low AT activity, these young patients demonstrate a normal or increased response to heparin anticoagulation before cardiopulmonary bypass (CPB). In contrast, in patients older than one year of age and adult patients decreased preoperative AT activity is mainly caused by preoperative heparin therapy and causes insufficient response to heparin anticoagulation with a standard heparin dosage. Measurement of preoperative AT activity identifies patients at risk of inadequate anticoagulation during CPB.
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Anesthesia and analgesia · Jan 2001
Comment Letter Comparative StudyCerebral hemodynamic response to the introduction of desflurane: a comparison with sevoflurane.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialThe analgesic effect of sufentanil combined with ropivacaine 0.2% for labor analgesia: a comparison of three sufentanil doses.
The combination of opioids with local anesthetics is commonly used for epidural labor analgesia. We examined whether increasing sufentanil in doses of 5, 10, and 15 microg prolonged the duration of labor analgesia produced by ropivacaine. One hundred healthy parturients in the first stage of labor who requested epidural analgesia were enrolled. Parturients were randomized to receive 12 mL ropivacaine 0.2% alone or with sufentanil 5 microg, sufentanil 10 microg, or sufentanil 15 microg. The duration of analgesia, pain score, degree of motor blockade (using a four-point Bromage scale), heart rate, blood pressure, respiratory rate, oxygen saturation, and incidence of nausea and pruritus were recorded. The mean duration of epidural analgesia was 96 +/- 32 min for patients without sufentanil, 134 +/- 27 min for Group 5 (p < 0.01 versus control), 135 +/- 33 min for Group 10 (p < 0.01 versus control), 130 +/- 33 min for Group 15 (p < 0.01 versus control) without differences among sufentanil groups. Between 30 and 90 min, the sufentanil groups (5 microg, 10 microg, and 15 microg) had lower pain scores than the control group (p < 0.01 versus control) but there were no differences among the sufentanil groups. No patient in any group had a Bromage score more than 1. No significant difference was found for opioid-related side effects. We conclude that 5-10 or 15 microg sufentanil induced a similar prolongation of analgesia when combined with ropivacaine 0.2% for initiation of labor analgesia. ⋯ We studied the effect of adding one of three possible sufentanil doses to epidural ropivacaine 0.2% for labor analgesia. Adding sufentanil increased the duration of analgesia but there was no advantage in adding more than 5 microg of sufentanil.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialA comparison of oral clonidine and oral midazolam as preanesthetic medications in the pediatric tonsillectomy patient.
We compared the effects of oral clonidine (4 microg/kg) and midazolam (0.5 mg/kg) on the preanesthetic sedation and postoperative recovery profile in children during tonsillectomy with or without adenoidectomy. In a double-blinded, double-dummy study design, 134 ASA physical status I-II children aged 4-12 yr were randomized to receive a combination of either clonidine and placebo (Group A), or placebo and midazolam (Group B) at 60-90 min and 30 min, respectively, before the induction of anesthesia. Children in the clonidine group exhibited more intense anxiety on separation and during induction of anesthesia via a mask as measured by the modified Yale Preoperative Anxiety Scores. They also had significantly lower mean intraoperative arterial blood pressures, shorter surgery, anesthesia, and emergence times, and a decreased need for supplemental oxygen during recovery compared with the midazolam group. However, the clonidine group had larger postoperative opioid requirements, maximum excitement and pain scores based on the Children's Hospital of Eastern Ontario scale in the Phase 1 postanesthetic care unit. There were no differences between the two groups in the times to discharge readiness, postoperative emesis, unanticipated hospital admission rates, postdischarge maximum pain scores, and 24 h analgesic requirements. The percentage of parents who were completely satisfied with the child's preoperative experience was significantly higher in the midazolam group. There were no differences in parental satisfaction with the recovery period. We conclude that under the conditions of this study, oral midazolam is superior to oral clonidine as a preanesthetic medication in this patient population. ⋯ We compared preanesthetic sedation and postoperative recovery after oral clonidine (4 microg/kg) and midazolam (0.5 mg/kg) in children during tonsillectomy. The clonidine group had greater preoperative anxiety and shorter surgery and anesthesia times, but required more postoperative analgesia. Delayed recovery and discharge times did not differ. Midazolam was superior to clonidine as oral preanesthetic medication for these patients.