W. W. Choi

Continuous infusion epidural analgesia during labor: a randomized, double-blind comparison of 0.0625% bupivacaine/0.0002% fentanyl versus 0.125% bupivacaine.

The analgesic efficacy of the continuous epidural infusion of 0.0625% bupivacaine/0.0002% fentanyl was compared with the infusion of 0.125% bupivacaine alone in a randomized, double-blind study of nulliparous women. Each patient received, in sequence: 1)3 ml of 0.5% bupivacaine with 1:200,000 epinep

Continuous Epidural Infusion of 0.0625% Bupivacaine-0.0002% Fentanyl during the Second Stage of Labor

A randomized, double-blind, placebo-controlled study was performed to evaluate the analgesic efficacy and influence of continuing an epidural infusion of 0.0625% bupivacaine-0.0002% fentanyl during the second stage of labor in nulliparous women. When the cervix was fully dilated, coded study solution was substituted for the known bupivacaine-fentanyl solution. The study solution for 29 patients was 0.0625% bupivacaine-0.0002% fentanyl; 34 patients received saline placebo. The two groups had similar pain scores during the first stage of labor. During the second stage, pain scores were significantly higher in the saline-placebo group at each 30-min interval between 60 and 150 min after the diagnosis of full cervical dilation. Similarly, there was a significant difference between the two groups in global assessment of analgesia quality during the second stage, but the difference occurred in those patients with a second-stage duration of greater than or equal to 60 min. Among the women who delivered vaginally, eleven of 28 (39%) women in the bupivacaine-fentanyl group, versus five of 34 (15%) in the saline-placebo group, had surgical perineal anesthesia for vaginal delivery (P less than .05). Six of 28 (21%) women in the bupivacaine-fentanyl group, and five of 34 (15%) in the saline-placebo group, underwent instrumental vaginal delivery (P = NS). The median duration of the second stage of labor was 53 min (range = 5-283) in the bupivacaine-fentanyl group, and 63 min (range = 16-181) in the saline-placebo group (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

An Evaluation of the Effect of Anesthetic Technique on Reproductive Success After Laparoscopic Pronuclear Stage Transfer - Propofol Nitrous-Oxide Versus Isoflurane Nitrous-Oxide

Background Laparoscopic pronuclear stage transfer (PROST) is the preferred method of embryo transfer after in vitro fertilization in many infertility programs. There are scant data to recommend the use or avoidance of any particular anesthetic agent for use in women undergoing this procedure. The authors hypothesized that propofol would be an ideal anesthetic for laparoscopic PROST because of its characteristic favorable recovery profile that includes minimal sedation and a low incidence of postoperative nausea and vomiting. The purpose of the study was to compare propofol and isoflurane with respect to postanesthetic recovery and pregnancy outcomes after laparoscopic PROST. Methods One hundred twelve women scheduled for laparoscopic PROST were randomized to receive either propofol/nitrous oxide or isoflurane/nitrous oxide for maintenance of anesthesia. Results Visual analog scale scores for sedation were lower in the propofol group than in the isoflurane group at all measurements between 30 min and 3 h after surgery. More women experienced emesis and were given an antiemetic during recovery in the isoflurane group than in the propofol group. However, the percentage of pregnancies with evidence of fetal cardiac activity was 54% in the isoflurane group compared with only 30% in the propofol group (P = 0.023). Also, the ongoing pregnancy rate was greater in the isoflurane group than in the propofol group (54% vs. 29%, P = 0.014). Conclusions Propofol/nitrous oxide anesthesia was associated with lower clinical and ongoing pregnancy rates compared with isoflurane/nitrous oxide anesthesia.

The Neuromuscular Blocking and Cardiovascular Effects of Doxacurium Chloride in Patients Receiving Nitrous Oxide Narcotic Anesthesia

The purpose of this study was to evaluate neuromuscular and cardiovascular effects of doxacurium chloride, a new long-acting neuromuscular blocking agent, during a stable state of nitrous oxide and narcotic anesthesia. Ninety-three ASA physical status I or II patients were studied after informed written consent had been obtained. Eighty-one patients (group A) received doxacurium. The 81 patients were divided into nine subgroups according to the dose of doxacurium administered (0.01–0.06 mg·kg-1). Patients in a control group (group B) (n=12) received pancuronium. To assess neuromuscular responses, a force displacement transducer recorded the twitch response of the adductor pollicis muscle following ulnar nerve stimulation. The ED50 and ED95 for doxacurium were estimated to be 0.013 mg·kg-1 and 0.023 mg·kg-1, respectively. The time to maximum twitch suppression following a dose of 1.0 (ED95) and 1.7 (ED95) was 10.3 ± 1.3 min and 7.6 ± 0.8 min, respectively. After an ED95 dose of doxacurium the time to spontaneous recovery to 95% of control twitch height was 73.7 ± 8.7 min. With larger doses of doxacurium, 0.04 mg·kg-1 (1.7 × ED95) and 0.05 mg·kg-1 (2.2 × ED95), the time to spontaneous recovery to 95% of control twitch height was 125.8 ± 24.8 and 204.0 ± 21.2 minutes, respectively. When 25% twitch height recovery or more was present the reversal of doxacurium induced neuromuscular blockade was prompt. After administration of 0.04 mg · kg-1 of doxacurium or 0.08 mg · kg-1 of pancuronium, the time for spontaneous recovery to 25% of control twitch height recovery was 77.4 ± 7.5 min (n = 23) and 71.4 ± 6.7 min (n = 10), respectively. When identical multiple maintenance doses of doxacurium were administered, the subsequent neuromuscular block following each maintenance dose was of similar magnitude and duration. At 1,2, and 5 min following pancuronium, heart rate and mean blood pressure increased. Following doxacurium small decreases in mean blood pressure occurred at 2 and 5 min, while heart rate decreased 5 min following drug injection. Doxacurium is a new, long-acting, nondepolarizing relaxant. Further study is warranted to assess the cardiovascular effects of this neuromuscular blocking drug in patients with cardiovascular disease.

Neuromuscular and cardiovascular effects of mivacurium chloride in surgical patients receiving nitrous oxide-narcotic or nitrous oxide-isoflurane anaesthesia

The neuromuscular and cardiovascular effects of mivacurium chloride were studied during nitrous oxide-oxygen narcotic (fentanyl) (n = 90) and nitrous oxide-oxygen isoflurane (ISO) anaesthesia (n = 45). In addition, a separate group (n = 9) received succinylcholine during fentanyl anaesthesia to compare its neuromuscular effects with mivacurium. Mivacurium was initially administered as a single bolus in doses from 0.03 mg · kg−1 to 0.25 mg · kg−1 to study the dose-response relationships, as well as the cardiovascular effects of mivacurium. Neuromuscular block (NMB) was measured by recording the twitch response of the adductor pollicis muscle following ulnar nerve stimulation (0.15 Hz, 0.2 ms supramaximal voltage). The ED95 values for mivacurium were estimated to be 0.073 mg · kg−1 and 0.053 mg · kg−1 in the fentanyl and ISO groups respectively. The duration of block (time from injection to 95 per cent recovery) for a dose of 0.05 mg · kg− 1 mivacurium was 15.3 ± 1.0 min and 21.5 ± 1.3 min for fentanyl and ISO anaesthesia, respectively. The recovery index (25–75 per cent) between initial bolus dose (6.1 ± 0.5 min), repeat bolus doses (7.6 ± 0.6 min), mivacurium infusion (6.7 ± 0.7 min) and succinylcholine infusion (6.8 ± 1.8 min) were not significantly different. There was minimal change in mean arterial pressure (MAP) or heart rate (HR) following bolus doses of mivacurium up to 0.15 mg · kg−1. Bolus administration of 0.20 mg · kg−1 or 0.25 mg · kg−1 of mivacurium decreased MAP from 78.2 ± 2.5 to 64.0 ± 3.2 mmHg (range 12–59 per cent of control) (P < 0.05). The same doses when administered slowly over 30 sec produced minimal change in MAP or HR.RésuméLes effets cardiovasculaires et neuromusculaires du chlorure de mivacurium ont été étudiés lors d’une anesthésie au narcotique (fentanyl) protoxyde d’azote-oxygène (n = 90) et isoflurane (ISO) protoxyde d’azote-oxygéne (n = 45). En plus, un groupe séparé (n = 9) a reçu du succinylcholine lors d’une anesthésie au fentanvl afin de comparer ces effets neuromusculaires avec le mivacurium. Le mivacurium a été initialement administré comme un bolus unique les doses de 0,03 mg · kg−1 et 0,25 mg · kg−1 afin d’étudier la courbe dose-réponse et les effets cardiovasculaires du mivacurium. Le bloc neuromusculaire (NMB) a été mesuré en enregistrant la réponse au twitch de l’adducteur du pouce après stimulation du nerf cubital (0.15 Hz, 0.2 ms voltage supramaximal). Les valeurs de ED95 du mivacurium ont été estimées à 0,073 mg ·kg−1 et 0,053 mg · kg−1 respectivement pour le groupe fentanyl et ISO. La durée du bloc (temps à partir de l’injection à la recouvrance à 95 pour cent) pour une dose de 0,05 mg · kg−1’ de mivacurium était de 15,3 ± 1,0 min. et 21,5 ± 1,3 min. respectivement pour le groupe fentanyl et le groupe ISO. L’index de recouvrance (25–75 pour cent) entre le bolus initial (6,1 ± 0,7 min) la dose de rajout (7,6 ± 0,6 min) et la perfusion de mivacurium (6,7 ± 0,7 min) et la perfusion de succinycholine (6,8 ± 1,8 min) n’était pas significativement différent. On a observé des changements minimes dans la pression artérielle moyenne (MAP) ou la fréquence cardiaque (HR) après le bolus de mivacurium jusqu’à 0,15 mg · kg−1. Une administration en bolus de 0,20 mg · kg−1 ou 0,25 mg · kg−1 de mivacurium a diminué la pression artérielle moyenne de 78,2 ± 2,5 à 64.0 1 3,2 mmHg (écart de 12–59 pour cent du contrôle) (P < 0.05). Les mêmes doses lorsque administrées lentement au-dessus de 30 secondes ont produit des changements minimes de la pression artérielle moyenne et de la fréquence cardiaque.

The effects of plasma and brain magnesium concentrations on lidocaine-induced seizures in the rat.

Lidocaine and MgSO4 are often coadministered to patients with pregnancy-induced hypertension. This study examined whether MgSO4 alters the lidocaineseizure threshold in the rat and, if so, whether systemic MgSO4 administration is as effective as intracerebroventricular MgSO4 infusion. In Experiment 1, rats were administered 50% MgSO4 or 0.9% NaCl intravenously (IV) (20 micro L/h) for 5 days. In Experiment 2, rats were administered 0.9% NaCl, 0.8% MgSO4, or 2.0% MgSO4 (10 micro L/h) via intracerebroventricular infusion for 24 h. All rats then underwent continuous IV lidocaine infusion until onset of electroencephalographic seizures. In Experiment 1, plasma [Mg2+] was greater in the MgSO4 group (5.1 +/- 1.5 mg/dL vs 1.8 +/- 0.3 mg/dL) but neither the dose of lidocaine required to induce seizures (MgSO4 = 19 +/- 2 mg/kg; saline = 23 +/- 5 mg/kg) nor brain [Mg2+] (MgSO4 = 794 +/- 17 micro g/g; saline = 788 +/- 33 micro g/g) were changed. In Experiment 2, intracerebroventricular MgSO4 increased both brain [Mg2+] (2% MgSO4 = 923 +/- 79 micro g/g; saline = 788 +/- 35 micro g/g) and the lidocaine seizure dose (2% MgSO4 = 39 +/- 7 mg/kg; saline = 26 +/- 3 mg/kg). Although intracerebroventricular administration of MgSO4 produces an anticonvulsant effect, chronic hypermagnesemia does not alter whole brain [Mg2+] and therefore offers no protection from lidocaine-induced seizures in this model. (Anesth Analg 1996;83:1223-8)

Does epidural fentanyl decrease the efficacy of epidural morphine after cesarean delivery

Earlier studies have suggested that epidural fentanyl improves intraoperative analgesia during cesarean section, but others have suggested that it worsens postoperative analgesia from epidural morphine. The purpose of this study was to determine whether epidural fentanyl given before epidural morphine improves the quality of intraoperative epidural anesthesia without worsening postoperative analgesia provided by epidural morphine. Sixty patients having epidural anesthesia for cesarean delivery were studied. Epidural anesthesia was established using 2% lidocaine with epinephrine 5 micrograms/mL. After delivery, either fentanyl 100 micrograms/10 mL or normal saline-control 10 mL was injected through the epidural catheter in a randomized, double-blind manner. All patients received 3.5 mg of morphine epidurally after uterine repair. After administration of the epidural study drug, there were no significant differences in the pain responses during surgery between the two groups. Patients in the fentanyl group experienced significantly less nausea and vomiting between delivery and the end of surgery than did patients in the normal saline-control group (P = 0.013). Postoperatively, visual analogue scale scores for pain, pruritus, nausea, and sedation were similar at 1, 2, 4, and 8 h in the two groups. We conclude that fentanyl 100 micrograms administered epidurally during cesarean delivery did not improve intraoperative analgesia, but significantly reduced intraoperative nausea and vomiting without diminishing the efficacy of postoperative analgesia provided by epidural morphine.

Effects of acute hypermagnesemia on the threshold for lidocaine-induced seizures in the rat

The effects of acute changes in plasma magnesium concentration on the threshold for lidocaine-induced seizures were evaluated in mechanically ventilated rats receiving 70% nitrous oxide and 30% oxygen. In experiment 1, male rats were intravenously administered either 0.9% sodium chloride (group I) or 5.0% magnesium sulfate to elevate plasma magnesium levels to 5.8 ± 0.1 (group II) or 10.5 ± 1.0 mg/dl (group III). In experiment 2, pregnant rats were intravenously administered either 0.9% sodium chloride (normomagnesemia) or magnesium sulfate, resulting in a plasma magnesium concentration of 7.8 ± 1.4 mg/dl. Thirty minutes later, a continuous intravenous infusion of lidocaine (2.3 mg/kg per minute) was begun in both experiments. Biparietal electroencephalographic activity was monitored continuously. At the onset of electroencephalographic seizure activity, arterial plasma magnesium and lidocaine concentrations were measured. In groups I and III (experiment 1), brain parenchymal magnesium was also assayed. There were no differences in plasma lidocaine concentrations (in experiments 1 or 2) between saline solution and hypermagnesemic groups at onset of seizures. Brain magnesium level was unaltered by magnesium sulfate infusion. We conclude that acute administration of magnesium sulfate alters neither brain magnesium level nor the plasma lidocaine concentration associated with onset of electroencephalographic seizures.

Low frequency jet ventilation for tracheal resection

Low frequency jet ventilation was used successfully for maintaining normal ventilation during tracheal resection for stenosis. Following resection of the stenosis around the endotrocheal tube, the tube was withdrawn and the proximal end of a sterile double lumen nasogastric tube with the distal end removed passed over the ether screen. The larger lumen was connected to a Saunders jet apparatus and the smaller to a CO2 analyzer. With the distal end held in the lumen of the distal tracheal stump, jet ventilation was initiated at a rate of 20/min at a pressure sufficient to obtain adequate chest rise and fall. Adequate CO2 removal was verified by monitoring the expired level and blood gases. We obtained normal arterial and end tidal gas tensions by this method which allowed the surgeon complete freedom to anastomose the posterior and lateral tracheal walls.

Conscious sedation for procedures under local or topical anesthesia.

For many surgical procedures in otolaryngology general anesthesia is not required, but it is difficult to block completely all noxious sensations with local or topical anesthesia. Intravenously administered antianxiety and analgesic drugs can make the procedure more tolerable for the patient. A technique of conscious sedation based upon titrating diazepam to specific eye signs and fentanyl to specific end points is described. Safety is maintained by ensuring that the patient is always in verbal contact with the surgeon. The rationale for administering the sedative before the narcotic is presented along with the treatment of side effects and untoward responses to the drugs.