The Effects of Small Intravenous Doses of Midazolam on Explicit Recall and the Bispectral Index after Fetal Expulsion in a Cesarean Section under General Anesthesia / 대한마취과학회지

BACKGROUND: Explicit recall in a cesarean section under general anaesthesia can be a terrifying experience and may cause psychological sequelae. Administering low doses of midazolam, we investigated the changes of the bispectral index (BIS) and the occurrence of explicit recall of specific events after fetal expulsion in a cesarean section under general anesthesia. METHODS: The investigation was carried out on 30 ASA 1 or 2 parturients who underwent a cesarean section under general anesthesia. Anesthesia was maintained with 50% N2O in oxygen and 0.75% of isflurane. We randomly allocated parturients into a control group (n = 10), group A (n = 10), and B (n = 10). Neither midazolam nor any other drugs except oxytocin were administered in the control group. In the group A and B, midazolam 0.02 and 0.03 mg/kg respectively, were injected immediately after umbilical cord clamping. An isolated forearm test were done to all the parturients at 5, 10, and 20 minutes after fetal expulsion. We assessed the changes of the BIS at 1, 2, 3, 4, 5, 10, 15, and 20 minutes after fetal expulsion, at discontinuance of isoflurane administration and extubation. The wav file, "clench your left or right hand" was binaurally played, simultaneously with the isolated forearm test. The wav file, "one, two, three, four, five" was also binaurally played 15 minutes after fetal expulsion. We interviewed all the parturients the next day and assessed the occurrence of explicit recall. RESULTS: The BIS values after fetal expulsion in the control group and group A was maintanied above 60 and group B, below 60 (P < 0.05). The lowest median BIS value was 54.5 in the group A, 36.4 in the group B (P < 0.05). There were two parturients in the control group and in the group A, respectively, who showed explicit recall. The results of the isolated forearm test were negative for all groups. The extubation times and PAR scores failed to show significant differences among the three groups. CONCLUSIONS: The authors confirmed the occurrence of explicit recall for specific events after fetal expulsion. The BIS values after fetal expulsion could be maintained below 60 until the end of surgery,and explicit recall could be prevented when we injected midazolam 0.03 mg/kg immediately after fetal expulsion.

Effect of Administration of Vecuronium or Rocuronium on Recovery from Pancuronium and Vice Versa in Isolated Forearm / 대한마취과학회지

BACKGROUND: It is important to consider the sequential administration of long- and short-acting non-depolarizing muscle relaxants. The purpose of this study is to evaluate the interaction between non-depolarizing muscle relaxants under isolated forearm test. METHODS: Ethics committee approval for all the volunteers (n=12) experiments was obtained. Pancuronium, 0.3 mg in 20 mL saline, was injected into one forearm; and vecuronium, 0.3 mg in 20 mL saline, was injected simultaneously into the other forearm in 6 volunteers. Three minutes later both tourniquets were released. Following spontaneous recovery in each forearm to 50% of the control twitch, the tourniquet was reinflated and the dose of drug of the same dilution used in the contralateral forearm was then injected (i. e., vecuronium following pancuronium in one forearm and pancuronium following vecuronium in the other forearm). Tourniquet was again released after 3 minutes and spontaneous recovery was allowed to occur. Interactions between pancuronium (0.3 mg) and rocuronium (2.0 mg) in 6 volunteers were also evaluated in a same method. RESULTS: Prior administration of pancuronium significantly prolonged the recovery rate from subsequent rocuronium (23.9 vs. 32.1 min, p<0.05), and rocuronium significantly shortened the recovery rate of pancuronium (32.4 vs. 25.9 min, p<0.05). There was simple additive interaction between pancuronium and vecuronium. CONCLUSION: The possible mechanism of these phenomena may be due to interaction of drug with acetylcholine receptors in the neuromuscular junction rather than due to residual plasma drug concentration.

Comparison of Pharmacokinetic Affinity of Various Non-depolarizing Neuromuscular Blocking Agents in the Isolated Foream / 대한마취과학회지

It is well known that the plasma concentration is important in determining the rate of recovery from neuromuscular block. However, nondepolarizing neuromuscular blockade are retained at the neuromuscular junction and are not readily displaced in response of changes in plasma drug concentration, for instance, the neuromuscular block induced by mivacurium appears to considerably outlast the theoretical plasma half-life of the drug and is continued long after the plasma level has fallen to subparalytic levels due to rapid metabolism by pseudocholinesterase. It has been suggested that although plasma concentration may be the key determinant of recovery from neuromuscular block, recovery will depend upon the dissociation from the affinity of drug in the effect compartrnent and not upon its plasma concentration. In an attempt to confirm these evidences, we have investigated the response of changes in neuromuscular block after releasing tourniquet at 50% twitch depression using the isolated forearm experiment with various neuromuscular blocking agents. The results of this study demonstrated the further increase of block after early toumiquet release in the isolated forarm in all agents; 66+/-14% in vecuronium, 90+/-9% in atracurium, 92+/-7% in pancuronium, and 73+/-18% in mivacurium Conclusively, the further block continued to increase in spite of the negligible plasma drug concentration after early tourniquet release may be caused by more in affinity of drugs in binding sites than plasma drug concentration. Therfore, it is evident that both the affinity of drug to the receptor and the plasma drug concentration have influenced on the recovery from the neuromuscular block.