Anesthesia and analgesia
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Anesthesia and analgesia · Apr 2002
Randomized Controlled Trial Clinical TrialPostoperative analgesia with continuous sciatic nerve block after foot surgery: a prospective, randomized comparison between the popliteal and subgluteal approaches.
To compare the posterior popliteal and subgluteal continuous sciatic nerve block for anesthesia and acute postoperative pain management after foot surgery, 60 ASA physical status I and II patients undergoing elective orthopedic foot surgery were randomly assigned to either a Subgluteal group (n = 30) or Popliteal group (n = 30). Before surgery and after performing a femoral nerve block with 15 mL of 2% mepivacaine, we performed the sciatic nerve block with 20 mL of 0.75% ropivacaine using either a subgluteal or posterior popliteal approach, and the placement of a catheter came afterward. In the recovery room, the catheter was connected to a patient-controlled analgesia pump to infuse 0.2% ropivacaine (basal infusion rate of 5 mL/h, incremental bolus of 10 mL, and a lockout time of 60 min). There were no technical problems in catheter placement. Intraoperative efficacy of nerve block was similar in the two groups. Postoperative catheter displacement and occlusion were recorded in four patients in the Popliteal group and two patients in the Subgluteal group (P = 0.67). Both approaches provided similar postoperative analgesia. We conclude that the subgluteal approach is as effective and safe as the previously described posterior popliteal approach for continuous sciatic block and can be considered a useful alternative to anesthesia and acute postoperative analgesia after foot procedures. ⋯ Comparing two different approaches for continuous sciatic nerve block after orthopedic foot surgery, this prospective, randomized study demonstrated that the subgluteal approach is as effective and safe as the previously described posterior popliteal approach, and can be considered a useful alternative to anesthesia and acute postoperative analgesia after foot procedures.
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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
Intrathecal lidocaine prevents cardiovascular collapse and neurogenic pulmonary edema in a rat model of acute intracranial hypertension.
Sympathetic hyperactivity during sudden intracranial hypertension leads to cardiovascular instability, myocardial dysfunction, and neurogenic pulmonary edema. Because spinal anesthesia is associated with sympatholysis, we investigated the protective effects of intrathecal lidocaine in a rodent model. Halothane-anesthetized rats were given a 10-microL intrathecal injection of saline (n = 10) or lidocaine 1% (n = 6). A subdural balloon catheter was inflated for 60 s to produce intracranial hypertension. Hemodynamics were monitored, and hearts and lungs were harvested for histological examination. In Saline versus Lidocaine-Treated rats, peak mean arterial blood pressure during balloon inflation was 115 +/- 4 mm Hg versus 78 +/- 8 mm Hg (P < 0.05), mean arterial blood pressure 30 min after balloon deflation was 47 +/- 2 mm Hg versus 67 +/- 3 mm Hg (P < 0.05), and lung weight was 1.54 +/- 0.03 g versus 1.41 +/- 0.04 g (P < 0.05), respectively. Cardiac dysrhythmias and electrocardiographic changes were more frequent in the Saline-Treated group (P < 0.05). Saline-Treated rats had extensive, hemorrhagic pulmonary edema, whereas the Lidocaine-Treated rats had only patchy areas of lung abnormality. Histological changes in the myocardium were rare, and no difference was found between the two groups. We conclude that intrathecal lidocaine prevents cardiovascular collapse and neurogenic pulmonary edema in a rat model of acute intracranial hypertension. ⋯ In a rat model of intracranial balloon inflation, intrathecal lidocaine prevented cardiovascular collapse and neurogenic pulmonary edema. Descending neural pathways are involved in the development of cardiopulmonary complications associated with acute intracranial hypertension.
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Anesthesia and analgesia · Apr 2002
How to schedule elective surgical cases into specific operating rooms to maximize the efficiency of use of operating room time.
We considered elective case scheduling at hospitals and surgical centers at which surgeons and patients choose the day of surgery, cases are not turned away, and anesthesia and nursing staffing are adjusted to maximize the efficiency of use of operating room (OR) time. We investigated scheduling a new case into an OR by using two patient-scheduling rules: Earliest Start Time or Latest Start Time. By using several scenarios, we showed that the use of Earliest Start Time is rational economically at such facilities. Specifically, it maximizes OR efficiency when a service has nearly filled its regularly scheduled hours of OR time. However, Latest Start Time will perform better at balancing workload among services' OR time. We then used historical case duration data from two facilities in computer simulations to investigate the effect of errors in predicting case durations on the performance of these two heuristics. The achievable incremental reduction in overtime by having perfect information on case duration versus using historical case durations was only a few minutes per OR. The differences between Earliest Start Time and Latest Start Time were also only a few minutes per OR. We conclude that for facilities at which the goals are, in order of importance, safety, patient and surgeon access to OR time, and then efficiency, few restrictions need to be placed on patient scheduling to achieve an efficient use of OR time. ⋯ We showed how elective cases should be scheduled to maximize the efficiency of use of operating room time. The analysis applies to surgical suites at which surgeons and patients have access to operating room time every workday.
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Anesthesia and analgesia · Apr 2002
Clinical TrialRemifentanil in obstetric analgesia: a dose-finding study.
IV patient-controlled analgesia (PCA) with remifentanil is a new approach in systemic opioid analgesia during labor. We determined the minimum effective dose of IV remifentanil by increasing the PCA bolus from 0.2 microg/kg with 0.2 microg/kg increments during a 60-min study period until the analgesia was considered adequate by the parturient. Twenty healthy parturients with singleton pregnancies participated in the study during the first stage of labor. Remifentanil hydrochloride was given IV via PCA over 1 min with a lockout time of 1 min. The parturient started the PCA bolus at the first subjective sign of uterine contraction. All 17 patients who completed the study reached adequate pain relief. The median effective PCA bolus was 0.4 microg/kg and consumption was 0.066 microg x kg(-1) x min(-1), with wide individual variation (0.2-0.8 microg/kg and 0.027-0.207 microg x kg(-1) x min(-1), respectively). The pain scores were reduced by a median of 4.2 (25th-75th percentiles, 3.1-5.2; P < 0.001) on an 11-point numeric scale. Although there was a wide individual variation in the dose required, remifentanil seems effective for labor analgesia. However, maternal oxygen desaturation, sedation, and reduced fetal heart rate beat-to-beat variability were observed frequently. There was wide individual variation in the dose required for effective labor analgesia. Potentially serious side effects, which were observed frequently during remifentanil analgesia, may limit remifentanil's use in obstetrics. ⋯ We determined the minimum effective dose of patient-controlled IV remifentanil for labor analgesia. There was wide individual variation in the dose required for effective labor analgesia. Potentially serious side effects, which were observed frequently during remifentanil analgesia, may limit its use in obstetrics.