Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1997
Randomized Controlled Trial Clinical TrialIntrathecal fentanyl with small-dose dilute bupivacaine: better anesthesia without prolonging recovery.
Recent concern regarding lidocaine neurotoxicity has prompted efforts to find alternatives to lidocaine spinal anesthesia. Small-dose dilute bupivacaine spinal anesthesia yields a comparably rapid recovery profile but may provide insufficient anesthesia. By exploiting the synergism between intrathecal opioids and local anesthetics, it may be possible to augment the spinal anesthesia without prolonging recovery. Fifty patients undergoing ambulatory surgical arthroscopy were randomized into two groups receiving spinal anesthesia with 3 ml 0.17% bupivacaine in 2.66% dextrose without (Group I) or with (Group II) the addition of 10 microg fentanyl. Median block levels reached T7 and T8, respectively (P = not significant [NS]). Mean times to two-segment regression, S2 regression, time out of bed, time to urination, and time to discharge were 53 vs 67 min (P < 0.01), 120 vs 146 min (P < 0.05), 146 vs 163 min (P = NS), 169 vs 177 min (P = NS), and 187 vs 195 min (P = NS) respectively. Motor blockade was similar between groups, but sensory blockade was significantly more intense in Group II (P < 0.01). Six of 25 blocks failed in Group I, whereas none failed in Group II. The addition of 10 microg fentanyl to spinal anesthesia with dilute small-dose bupivacaine intensifies and increases the duration of sensory blockade without increasing the intensity of motor blockade or prolonging recovery to micturition or street fitness. ⋯ Concerns about the neurotoxicity of lidocaine have prompted efforts to find alternatives to lidocaine spinal anesthesia. We studied 50 patients undergoing ambulatory surgical arthroscopy and found that although small-dose bupivacaine alone is inadequate for this procedure, the addition of fentanyl makes it reliable.
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Anesthesia and analgesia · Sep 1997
Randomized Controlled Trial Clinical TrialSimulation of an epidural test dose with intravenous isoproterenol in isoflurane-anesthetized adults.
Although a simulated intravenous (I.V.) test dose containing 3 microg isoproterenol results in a reliable heart rate (HR) increase in anesthetized patients, hypotension may limit its clinical utility. The present study was designed to determine the incidence of hypotension and the reliability of smaller doses of isoproterenol. Forty-five healthy adult patients were anesthetized with 1% end-tidal isoflurane and nitrous oxide after endotracheal intubation and were randomized to one of three groups according to the dose of isoproterenol. Isoproterenol 1-, 2-, and 3-microg groups (n = 15 each) received 3 mL of 1.5% lidocaine with 1, 2, and 3 microg isoproterenol I.V., respectively, to simulate an intravascularly administered test dose. HR and systolic blood pressure were measured at 20-s intervals for 4 min after injection. Mean maximal HR increases were 15 +/- 6, 23 +/- 10, and 32 +/- 7 bpm (mean +/- SD) in the isoproterenol 1-, 2-, and 3-microg groups, respectively. However, the incidence and degree of systolic hypotension were similar among groups. Isoproterenol 3 microg produced 100% sensitivity in both the conventional (> or = 20 bpm increase) and the modified (> or = 10 bpm increase) HR criteria, but 2 microg resulted in 100% sensitivity on the modified criterion alone. Isoproterenol 1 microg did not elicit reliable HR changes. Significant correlation was demonstrated between the isoproterenol dose (microg/kg) and the maximal HR increase. Ninety-five percent confidence intervals to increase HR by 10 and 20 bpm were 0.015-0.02 microg/kg and 0.03-0.04 microg/kg, respectively. The application of isoproterenol as a test dose component seems promising, pending detailed studies of neural toxicity. The appropriate dose needs to be tailored according to the patient's weight. ⋯ To determine whether an epidural catheter may be in a blood vessel, various vasoactive drugs are often administered. The author found that isoproterenol might be a useful drug in place of epinephrine.
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Anesthesia and analgesia · Sep 1997
Antithrombin III during cardiac surgery: effect on response of activated clotting time to heparin and relationship to markers of hemostatic activation.
This study was designed to determine if, and to what extent, antithrombin III (AT) levels affect the response of the activated clotting time (ACT) to heparin in concentrations used during cardiac surgery, and to characterize the relationship between AT levels and markers of activation of coagulation during cardiopulmonary bypass (CPB). After informed consent, blood specimens obtained from eight normal volunteers (Phase I) were used to measure the response of the kaolin and celite ACT to heparin after in vitro addition of AT (200 U/dL) and after dilution with AT-deficient plasma to yield AT concentrations of 20, 40, 60, 80, and 100 U/dL. In Phase II, blood specimens collected before the administration of heparin and prior to discontinuation of CPB, were used to measure the response of the kaolin ACT to heparin (preheparin only), AT concentration, and a battery of coagulation assays in 31 patients undergoing repeat or combined cardiac surgical procedures. In Phase I, strong linear relationships were observed between kaolin (slope = 1.04 AT - 2, r2 = 0.78) and celite (slope = 1.36 AT + 6, r2 = 0.77) ACT slopes and AT concentrations below 100 U/dL. In the pre-CPB period of Phase II, only factors V (partial r = -0.49) and VIII (partial r = -0.63) were independently associated with heparin-derived slope using multivariate analysis; an inverse relationship was observed between AT and fibrinopeptide A levels (r = -0.41) at the end of CPB. Our findings indicate that the responsiveness of whole blood (ACT) to heparin at the high concentrations used with CPB is progressively reduced when the AT concentration decreases below 80 U/dL. Because AT is variably, and sometimes extensively, reduced in many patients before and during CPB, AT supplementation in these patients might be useful in reducing excessive thrombin-mediated consumption of labile hemostatic blood components, excessive microvascular bleeding, and transfusion of blood products. ⋯ Heparin, a drug with anticoagulant properties, is routinely given to patients undergoing cardiac surgery to prevent clot formation within the cardiopulmonary bypass circuit. However, when levels are reduced, heparin is not as effective. Findings within this study indicate that administration of antithrombin III may help to preserve the hemostatic system during cardiopulmonary bypass.
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Anesthesia and analgesia · Sep 1997
Randomized Controlled Trial Multicenter Study Comparative Study Clinical TrialUse of the laryngeal mask airway as an alternative to the tracheal tube during ambulatory anesthesia.
We designed a prospective, randomized, multicenter study to compare anesthetic requirements, recovery times, and postoperative side effects when a laryngeal mask airway (LMA) was used as an alternative to the tracheal tube (TT) during ambulatory anesthesia. After induction of anesthesia with midazolam 2 mg, fentanyl 1 microg/kg, and propofol 2 mg/kg, 381 patients were randomly assigned to receive either an LMA (n = 207) or TT (n = 174) for airway management. In patients assigned to the TT group, succinylcholine 1 mg/kg or a nondepolarizing muscle relaxant was administered to facilitate tracheal intubation. Anesthesia was maintained with volatile anesthetics in combination with nitrous oxide 60% and oxygen. The average time to placement of the two airway devices (5 min) and the failure rates (1%) were similar in the two groups. Although there was a significant decrease in the intraoperative fentanyl requirement in the LMA group, the difference was of little clinical significance. Furthermore, there were no differences in the volatile anesthetic requirements. The time from end of surgery to removal of the airway device (5 min) was also similar in the two study groups. Although duration of the postanesthesia care unit stay and time to ambulation were significantly shorter in the LMA group, there were no differences in the times to "home readiness." The incidence of nausea and vomiting and the need for rescue antiemetic treatments in the postoperative period were similar in the two airway management groups. However, the incidence of postoperative sore throat was significantly greater in patients receiving the TT (versus the LMA). In conclusion, this study suggests that the LMA is a useful alternative to the TT for airway management during ambulatory anesthesia. ⋯ Use of the laryngeal mask airway can obviate the need for insertion of a tracheal tube for many ambulatory surgery procedures, and thereby decrease the incidence of postoperative sore throats.