The Negative Effects of Patient Controlled Sedation Using Midazolam for Cataract Surgery under Retrobulbar Block / 대한마취과학회지

BACKGROUND: Careful sedation is needed for cataract operation that requires absolute cooperation of elderly patients. Patient-controlled sedation (PCS) allows patients themselves change the dose of sedatives along with their need. The goal of this study was to find out midazolam PCS could achieve an adequate sedation without complications during cataract surgery and the differences of patients who needed PCS or not. METHODS: PCS with midazolam was applied to 33 patients undergoing cataract surgery using retrobulbar block (midazolam, bolus 0.5 mg, lock out interval 3 minutes, 1 hour limit 4.5 mg). PCS pump was given to patients 30 min before retrobular block. And patients themselves decided to use or not to use PCS after full explanation on PCS. Sedation score, visual analogue scale of anxiety, cognitive function, side effects and satisfaction of PCS were measured. RESULTS: PCS users were 22 (67%). Mean midazolam dosage of PCS users was 2.03 mg. Preoperative and intraoperative anxiety score were 40.2 mm and 13.0 mm in PCS users and 15.5 mm and 21.8 mm in non-users. The difference between PCS users and non-users was only preoperative anxiety levels. Age, sex, weight, education levels, previous cataract surgery, preoperative desired sedation levels did not influence on the PCS using. There was positive correlation of midazolam doses with only preoperative anxiety levels. 76% of surgeons and 85% of patients were satisfied with PCS but 7 patients showed involuntary movement. Cognitive functions and discharge time were not influenced by PCS. CONCLUSIONS: Although patients and surgeons were satisfied with the midazolam PCS, 33% of patients did not need PCS and deep sedation with involuntary movement that could bring surgical complications was resulted in some PCS users. We conclude that PCS for cataract surgery would be safer when it is administered under careful supervision of anesthesiologist.

Changes in Bispectral Index during Coinduction with Intravenous Anesthetics Using Synergistic Interaction / 대한마취과학회지

BACKGROUND: Coinduction according to a hypnotic synergistic effect of intravenous anesthetics has an advantage of reducing hemodynamic change, induction dose and side effects of each drug. Meanwhile, the bispectral index has been used to monitor objective measurement of the hypnotic effect of intravenous anesthetics. The aim of this study was to evaluate the changes in the bispectral index during coinduction with two intravenous anesthetics that were known to have synergistic interactions. METHODS: Sixty ASA I or II adult patients undergoing elective surgery were assigned to one of three groups according to induction methods: group 1, thiopental + propofol; group 2, thiopental + midazolam; group 3, midazolam propofol. Anesthesia induction was performed by injecting half of a hypnotic ED50 dose of both drug according to the known time to peak effect. For example, in group 1, propofol was injected first, and then thiopental 1 min. later. The Bispectral index, vital signs, and SpO2 were checked every minute for 5 minutes after injection of a drug. RESULTS: Each group showed the lowest point of the BIS at time to peak effect, but the reduction of the BIS for each group showed no regular pattern between time and amount of degree compared to the lowest BIS of the two drugs when they were used alone. CONCLUSIONS: The BIS has limitations in expressing a synergistic interaction phenomenon when anesthesia induction with two intravenous anesthetics that have a synergistic interaction.

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.

The Effects of Midazolam and Droperidol Pretreatment on the Cardiac Toxicity of Bupivacaine in Rabbits / 대한마취과학회지

BACKGROUND: Unintended intravenous injection of bupivacaine causes severe cardiovascular complication, which is known for its difficulty in resuscitation. This study was performed to evaluate the effects of pretreatment with midazolam and droperidol in the cardiac toxicity caused by intravenous infusion of bupivacaine. METHODS: Thirty rabbits were divided into three groups; saline- as a control, midazolam, and droperidol pretreated group. We observed the time intervals for the arrhythmia, 25% and 50% reduction in baseline mean arterial blood pressure, and arrest. We also checked the dose of infused bupivacaine to be required for arrest during continuous intravenous infusion of bupivacaine at the rate of 1 mg/kg/min. RESULTS: The onset of dysrhythmia and the time to 50% reduction in baseline mean arterial blood pressure and arrest were significantly more delayed in the midazolam group than the control group (P < 0.05). With respect to the time to 25%, 50% reduction in baseline mean arterial blood pressure and arrest, the data of the droperidol group was significantly shorter than that of the control group (P < 0.05). CONCLUSIONS: Droperidol pretreatment hastened bupivacaine induced cardiac arrest in rabbits. Midazolam pretreatment exerted protective effects on arrhythmia and cardiac arrest. Thus midazolam would be a preferable agent as a supplement for regional anesthesia using bupivacaine.

On the Usefulness of Intravenous Anesthesia for Patients Undergoing Postoperative Radiologic Examination / 대한마취과학회지

BACKGROUND: In most brain operations, the endotracheal tube is kept in postoperatively for airway maintenance during radiologic examinations. But the endotracheal tube causes tracheal irritation and hemodynamic changes. Inhalation anesthetics can not be administered during transport, and minimal concentration is exhaled for several hours after the end of inhalation. The present study was designed : (1) to determine the end tidal isoflurane concentration after the end of administration ; (2) to investigate the effects of intravenous anesthetics in patients with tracheal intubation during radiologic examination postoperatively. METHODS: We selected forty adult patients who were scheduled for elective neurosurgical operation with postoperative brain CT (computerized tomography). The study was performed in 2 steps; in the step 1 (n = 10), end tidal isoflurane concentration was checked after ending inhalation. In the step 2 (n = 30), patients were divided into one of three groups according to anesthesia method; group I (using isoflurane), group P (change from isoflurane to propofol about an hour before operation end), group M (using midazolam instead of propofol, compared to group P). In each group, the frequency of bucking and incidence of hypertension were checked during postoperative radiologic examinations. RESULTS: Minimal concentrations of isoflurane were detected in exhaled gas for about 2 hours after the end of isoflurane inhalation. The frequency of bucking was significantly lower in the group P and M than in group I (P = 0.002). In group P, the incidence of hypertension was significantly reduced compared to group M and I (P = 0.031). CONCLUSIONS: These results suggest that the change of anesthetic technique (from inhalation to intravenous) in the late period of operation, provides postoperative hemodynamic stability, a more comfortable state and minimal environmental pollution in comparison to inhalation anesthesia only.

On the Usefulness of Intravenous Anesthesia for Patients Undergoing Postoperative Radiologic Examination / 대한마취과학회지

BACKGROUND: In most brain operations, the endotracheal tube is kept in postoperatively for airway maintenance during radiologic examinations. But the endotracheal tube causes tracheal irritation and hemodynamic changes. Inhalation anesthetics can not be administered during transport, and minimal concentration is exhaled for several hours after the end of inhalation. The present study was designed : (1) to determine the end tidal isoflurane concentration after the end of administration ; (2) to investigate the effects of intravenous anesthetics in patients with tracheal intubation during radiologic examination postoperatively. METHODS: We selected forty adult patients who were scheduled for elective neurosurgical operation with postoperative brain CT (computerized tomography). The study was performed in 2 steps; in the step 1 (n = 10), end tidal isoflurane concentration was checked after ending inhalation. In the step 2 (n = 30), patients were divided into one of three groups according to anesthesia method; group I (using isoflurane), group P (change from isoflurane to propofol about an hour before operation end), group M (using midazolam instead of propofol, compared to group P). In each group, the frequency of bucking and incidence of hypertension were checked during postoperative radiologic examinations. RESULTS: Minimal concentrations of isoflurane were detected in exhaled gas for about 2 hours after the end of isoflurane inhalation. The frequency of bucking was significantly lower in the group P and M than in group I (P = 0.002). In group P, the incidence of hypertension was significantly reduced compared to group M and I (P = 0.031). CONCLUSIONS: These results suggest that the change of anesthetic technique (from inhalation to intravenous) in the late period of operation, provides postoperative hemodynamic stability, a more comfortable state and minimal environmental pollution in comparison to inhalation anesthesia only.

Comparison of Propofol and Midazolam for Sedation of Mechanically Ventilated Patients / 대한마취과학회지

BACKGROUND: Mechanical ventilation is frequently used in the intensive care unit. Sedation is usually required to tolerate the presence of a tracheal tube and other unpleasant stimulus during mechanical ventilation. The ideal regimen for sedation has not yet been determined. This study was designed to compare the characteristics of safety and effectiveness of propofol to those of midazolam for sedation in patients undergoing mechanical ventilation in surgical intensive care unit. METHODS: 44 mechanically ventilated patients were randomized to receive either propofol (loading dose 20~40 mg, followed by 10~50 microgram/kg/min) or midazolam (loading dose 1~2 mg, followed by 0.2~0.8 microgram/kg/min). Infusion rates were titrated to 3~5 points of Ramsay scale. All patients also received morphine 0.5 microgram/kg/24 h without any muscle relaxants. Hemo-dynamic changes (SBP, DBP, HR), ventilatory parameters and recovery time were evaluated. Hepatic and renal functions were measured before start of infusion and after discontinuation of both drugs. RESULTS: The mean initial loading and maintenance dose were 0.35 mg/kg and 1.5 mg/kg/hr for the propofol, 29.2 microgram/kg and 29.1 microgram/kg/h for midazolam group, respectively. There was no difference between the two groups regarding the sedation score evaluated by Ramsay scale. Patients receiving propofol recovered more rapidly than those receiving midazolam (40.5+/-20.1 min vs. 88.2+/-29.5 min respectively; P30% of pre-injection value) or hepatic or renal function changes. CONCLUSIONS: Propofol is a sedative agent with shorter awakening time than midazolam but with the same safety and clinical effectiveness for the continuous sedation of mechanically ventilated patients.

Comparison of Propofol and Midazolam for Sedation of Mechanically Ventilated Patients / 대한마취과학회지

BACKGROUND: Mechanical ventilation is frequently used in the intensive care unit. Sedation is usually required to tolerate the presence of a tracheal tube and other unpleasant stimulus during mechanical ventilation. The ideal regimen for sedation has not yet been determined. This study was designed to compare the characteristics of safety and effectiveness of propofol to those of midazolam for sedation in patients undergoing mechanical ventilation in surgical intensive care unit. METHODS: 44 mechanically ventilated patients were randomized to receive either propofol (loading dose 20~40 mg, followed by 10~50 microgram/kg/min) or midazolam (loading dose 1~2 mg, followed by 0.2~0.8 microgram/kg/min). Infusion rates were titrated to 3~5 points of Ramsay scale. All patients also received morphine 0.5 microgram/kg/24 h without any muscle relaxants. Hemo-dynamic changes (SBP, DBP, HR), ventilatory parameters and recovery time were evaluated. Hepatic and renal functions were measured before start of infusion and after discontinuation of both drugs. RESULTS: The mean initial loading and maintenance dose were 0.35 mg/kg and 1.5 mg/kg/hr for the propofol, 29.2 microgram/kg and 29.1 microgram/kg/h for midazolam group, respectively. There was no difference between the two groups regarding the sedation score evaluated by Ramsay scale. Patients receiving propofol recovered more rapidly than those receiving midazolam (40.5+/-20.1 min vs. 88.2+/-29.5 min respectively; P30% of pre-injection value) or hepatic or renal function changes. CONCLUSIONS: Propofol is a sedative agent with shorter awakening time than midazolam but with the same safety and clinical effectiveness for the continuous sedation of mechanically ventilated patients.

The Effects of Midazolam on Propofol-Induced Involuntary Movement, Pain on Injection and Maintenance Dose / 대한마취과학회지

BACKGROUND: This study examined the effects of midazolam on the propofol-induced involuntary movements, pain on injection, the maintenance dose of propofol, and recovery characteristics. METHODS: In a double-blind, randomized study, 30 children (2 8 yr of age, ASA physical status I or II) undergoing short duration of ENT procedures received midazolam 0.06 mg/kg (Group M) or an equal volume of placebo (Group P) intravenously 3 min before the injection of propofol. At induction of anesthesia an independent anesthesiologist graded the incidence, severity of involuntary movements, and pain on injection. RESULTS: Both groups were similar in age, sex, weight, propofol dose, duration of surgery and anesthesia. Incidence of involuntary movements showed no significant difference between two groups. But, there were significant difference in severity between two groups (P < 0.05). There was significant decrease in pain on injection in group M than group P and no significant differences in open eyes on command, time to extubation and time to discharge. CONCLUSION: Our result demonstrated that midazolam 60 microgram/kg compared with placebo did not reduce the incidence of involuntary movement, but reduced the severity of involuntary movement without delayed recovery. And there was significant reduction of pain on injection in midazolam 60 microgram/kg administration.

The Effects of Flumazenil and Verapamil on the Relaxation of Midazolam in Isolated Guinea-pig Tracheal Smooth Muscle / 대한마취과학회지

BACKGROUND: Midazolam relaxes airway smooth muscle. The aim of this study is to evaluate the influence of flumazenil or verapamil on the relaxation effects of midazolam in tracheal smooth muscle of guinea pig. METHODS: After isolating guinea-pig tracheal preparations, the maximal tracheal tones were induced by 2 10(-7) M carbachol. When tracheal tones stabilized, midazolam was added cumulatively (10(-6), 3 10(-6), 10(-5), 3 10(-5), 10(-4) M, n=14) with or without flumazenil (10(-6) M, n=15) and verapamil (10(-5) M, n=13) to obtain the concentration-relaxation curves, and then the ED50 and ED95 calculated. RESULTS: Midazolam decreased maximal tracheal smooth muscle tones in concentration-dependent manners. Pretreatment with flumazenil had no effect on the midazolam-induced relaxation. Verapamil enhanced the relaxation effect of midazolam. CONCLUSIONS: Midazolam relaxes airway smooth muscle and has synergistic effect with calcium channel blocker, verapamil.

The Frequency of Apnea and Loss of Consciousness According to Propofol Dosage in Premedicated Patients with Midazolam / 대한마취과학회지

BACKGROUND: Respiratory depression with high dose of propofol during induction is one of the major complications. We studied the effects of midazolam as premedicant on frequency and duration of apnea and frequency of loss of consciousness in relation to single dose of propofol. METHODS: We selected 194 adult patients who had clear consciousness and no depression of respiration. We allocated patients randomly to control group and midazolam group. In midazolam group, we injected 0.06mg/kg of midazolam intravenously 10min before induction, and in control group, we did nothing. Under mask oxygenation with 100% oxygen, we administered a bolus of propofol (1, 1.5, 2 mg/kg to subgroup 1, 2, 3 respectively) intravenously. The change of respiration and loss of consciousness were observed. RESULTS: The frequency and duration of apnea increased with the dose of propofol in both control and midazolam group. But there were no difference between groups except frequency of apnea with 1.5 mg/kg of propofol. In control group, frequency of loss of consciousness increased with the increasing dose of propofol. But in midazolam group, nearly all the patients was slept without difference by the dose. CONCLUSIONS: Premedication with midazolam reduce the sleeping dose of propofol to induce anesthesia, so the frequency and duration of apnea which is caused by high dose of propofol can be decreased.

Midazolam Pharmacokinetics in Patients Undergoing Lung Surgery / 대한마취과학회지

BACKGROUND: The nature of operation alters the volume of distribution at steady state (Vdss) of drug. The hepatic extraction ratio of midazolam (0.3~0.7) could be influenced by hepatic blood flow (HBF), and hepatic enzyme activity. The pharmacokinetics of intravenous midazolam were determined in patients undergoing lung surgery. METHODS: Midazolam, 0.2 mg/kg, was administered to five patients undergoing lung surgery at 30 minutes after induction of anesthesia. Anesthesia was maintained with O2-enflurane for one lung ventilation. Blood samples from artery were drawn at increasing intervals for 12 h. Plasma midazolam concentrations were measured by gas chromatography. Computer simulations of the times required for 20%, 50%, and 80% decreases in midazolam concentrations were performed. RESULTS: A three compartment model best described the concentration versus time data. The volume of the central compartment (Vc) and volume of distribution at steady state (Vdss) were 4.3 2.8 l and 59.9 20.1 l, respectively. The elimination half-life was 3.4 2.2 h. Simulations indicate that under all the situations, the concentrations would decrease more rapidly in our patients in spite of similar Vdss and elimination half-life of patients undergoing minor gynecological surgery. CONCLUSION: The elimination half-life was in the range of previously reported values. The shorter recovery time is apparently due to relatively faster redistrubution, and relatively greater capacity for redistribution.