Anesthesia and analgesia
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Anesthesia and analgesia · May 1999
Blood pressure is maintained despite profound myocardial depression during acute bupivacaine overdose in pigs.
Bupivacaine-induced cardiovascular collapse is a feared complication because of the difficulty in restoring stable circulation (1). Early recognition is important so that the injection of bupivacaine can be discontinued. We used an animal model of near-cardiac arrest from bupivacaine infusion to identify the sequence of hemodynamic events that precedes bupivacaine-induced cardiovascular collapse. Twelve pigs (23-25 kg) were sedated with ketamine and anesthetized with halothane. Arterial blood pressure and cardiac output were measured. Bupivacaine (3.75 mg/mL) was administered at a rate of 5.73 mL/min (approximately 1 mg x kg(-1) x min(-1)) through a central venous catheter until severe ventricular arrhythmia occurred. Blood pressure and heart rate were unchanged, but cardiac output decreased by 40% with increasing doses of bupivacaine. Calculated peripheral resistance increased by 54%. The QRS complex of the surface electrocardiogram widened, and the R-wave amplitude decreased 80%, together with the decrease in cardiac output. T-wave amplitude increased initially but returned toward baseline at the largest bupivacaine doses. The plasma concentration of bupivacaine after the infusion was 16+/-6.8 microg/mL. ⋯ The increase in vascular resistance that accompanies acute bupivacaine overdose maintains blood pressure but masks severe myocardial depression.
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Anesthesia and analgesia · May 1999
Randomized Controlled Trial Multicenter Study Clinical TrialHextend, a physiologically balanced plasma expander for large volume use in major surgery: a randomized phase III clinical trial. Hextend Study Group.
Hextend (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and physiological levels of glucose. In preclinical studies, its use in shock models was associated with an improvement in outcome compared with alternatives, such as albumin or 6% hetastarch in saline. In a prospective, randomized, two-center study (n = 120), we compared the efficacy and safety of Hextend versus 6% hetastarch in saline (HES) for the treatment of hypovolemia during major surgery. Patients at one center had a blood sample drawn at the beginning and the end of surgery for thromboelastographic (TEG) analysis. Hextend was as effective as HES for the treatment of hypovolemia. Patients received an average of 1596 mL of Hextend: 42% received >20 mL/kg up to a total of 5000 mL. No patient received albumin. Hextend-treated patients required less intraoperative calcium (4 vs 220 mg; P < 0.05). In a subset analysis of patients receiving red blood cell transfusions (n = 56; 47%), Hextend-treated patients had a lower mean estimated blood loss (956 mL less; P = 0.02) and were less likely to receive calcium supplementation (P = 0.04). Patients receiving HES demonstrated significant prolongation of time to onset of clot formation (based on TEG) not seen in the Hextend patients (P < 0.05). No Hextend patient experienced a related serious adverse event, and there was no difference in the total number of adverse events between the two groups. The results of this study demonstrate that Hextend, with its novel buffered, balanced electrolyte formulation, is as effective as 6% hetastarch in saline for the treatment of hypovolemia and may be a safe alternative even when used in volumes up to 5 L. ⋯ Hextend (BioTime, Inc., Berkeley, CA) is a new plasma volume expander containing 6% hetastarch, balanced electrolytes, a lactate buffer, and a physiological level of glucose. It is as effective as 6% hetastarch in saline for the treatment of hypovolemia but has a more favorable side effects profile in volumes of up to 5 L compared with 6% hetastarch in saline.
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Anesthesia and analgesia · May 1999
Randomized Controlled Trial Clinical TrialIntraperitoneal lidocaine decreases intraoperative pain during postpartum tubal ligation.
We conducted a randomized, double-blinded, placebo-controlled trial to evaluate the effectiveness of intraperitoneal lidocaine, IM morphine, or both drugs together for pain relief in postpartum tubal ligation. Eighty postpartum patients scheduled to have tubal sterilization were randomly divided into four groups to receive IM isotonic sodium chloride solution (1 mL) and intraperitoneal instillation of 80 mL of isotonic sodium chloride solution (Group P); IM morphine (10 mg in 1 mL) and intraperitoneal instillation of 80 mL of isotonic sodium chloride solution (Group M); IM injection of isotonic sodium chloride solution and intraperitoneal instillation of 0.5% lidocaine in 80 mL (Group L); and both IM morphine and intraperitoneal lidocaine instillation (Group ML). The minilaparotomy was performed after local infiltration with 15 mL of 1% lidocaine. A numerical rating score was used to rate pain on a 0-10 scale during the surgical procedures. The mean pain scores were 1.2 in Group L and 0.8 in Group ML. These pain scores were significantly lower than those in Groups P and M, which were 5.5 and 6.0, respectively (P < 0.001). ⋯ Pain relief was inadequate in patients undergoing postpartum tubal ligation under local anesthesia, even after the administration of IM morphine. Instilling lidocaine into the abdominal cavity, however, effectively decreased intraoperative pain in these patients.
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Anesthesia and analgesia · May 1999
Randomized Controlled Trial Clinical TrialThe effects of subanesthetic concentrations of sevoflurane and nitrous oxide, alone and in combination, on analgesia, mood, and psychomotor performance in healthy volunteers.
We studied the effects of subanesthetic concentrations of sevoflurane and nitrous oxide, alone and in combination, on analgesia, mood, and psychomotor performance in human volunteers. We hypothesized that nitrous oxide and sevoflurane would produce both opposing and potentiating effects within the same study. Over the course of three sessions, 20 subjects inhaled 0%, 0.2%, or 0.4% end-tidal sevoflurane for a 68-min period that was divided into four 17-min blocks. During either the second or fourth block, 30% end-tidal nitrous oxide was added to the concentration of sevoflurane being inhaled. Pain response, psychomotor performance, and mood were evaluated during the second and fourth blocks. Pain ratings were higher when sevoflurane and nitrous oxide were administered together than when nitrous oxide was administered alone, which indicates that sevoflurane attenuated the analgesic effects of nitrous oxide. Sevoflurane increased self-reported ratings of sleepiness, and the addition of nitrous oxide decreased these ratings. Nitrous oxide potentiated psychomotor impairment that was induced by sevoflurane. The combination of sevoflurane and nitrous oxide produced both opposing and potentiating effects within the same study. The results suggest that nitrous oxide and sevoflurane may act through different neurochemical mechanisms on some end points, such as analgesia and sleepiness. ⋯ Healthy volunteers inhaled subanesthetic concentrations of sevoflurane and nitrous oxide. Sevoflurane made nitrous oxide less effective as an analgesic, and nitrous oxide made sevoflurane less effective as a sedative. The two drugs may work at cross purposes on different end points of anesthesia.
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Anesthesia and analgesia · May 1999
Distress during the induction of anesthesia and postoperative behavioral outcomes.
We determined whether children who are extremely anxious during the induction of anesthesia are more at risk of developing postoperative negative behavioral changes compared with children who appear calm during the induction process. Children (n = 91) aged 1-7 yr scheduled for general anesthesia and elective outpatient surgery were recruited. Using validated measures of preoperative anxiety and postoperative behaviors, children were evaluated during the induction of general anesthesia and on Postoperative Days 1, 2, 3, 7, and 14. Using a multivariate logistic regression model, in which the dependent variable was the presence or absence of postoperative negative behavioral changes and the independent variables included several potential predictors, we demonstrated that anxiety of the child, time after surgery, and type of surgical procedure were predictors for postoperative maladaptive behavior. The frequency of negative postoperative behavioral changes decreased with time after surgery, and the frequency of negative postoperative behavioral changes increased when the child exhibited increased anxiety during the induction of anesthesia. Finally, we found a significant correlation (r) of 0.42 (P = 0.004) between the anxiety of the child during induction and the excitement score on arrival to the postanesthesia care unit. We conclude that children who are anxious during the induction of anesthesia have an increased likelihood of developing postoperative negative behavioral changes. We recommend that anesthesiologists advise parents of children who are anxious during the induction of anesthesia of the increased likelihood that their children will develop postoperative negative behavioral changes such as nightmares, separation anxiety, and aggression toward authority. ⋯ Anesthesiologists who care for children who are anxious during the induction of anesthesia should inform parents that these children have an increased likelihood of developing postoperative negative behavioral changes.