Nefopam does not influence onset and recovery profiles of rocuronium-induced neuromuscular block: a prospective, double-blinded, randomized, controlled study

BACKGROUND: We investigated the hypothesis that pretreatment with nefopam 20 mg would influence the onset and recovery profiles of rocuronium-induced neuromuscular block. METHODS: After Institutional Review Board approval, 134 patients, aged between 20–65 years, belonging to the American Society of Anesthesiologists physical status classification I or II, were randomly allocated to receive either 0.9% normal saline (control group) or nefopam 20 mg (nefopam group), infused over one hour before induction of anesthesia. Anesthesia was induced with remifentanil and propofol, followed by endotracheal intubation with rocuronium 0.6 mg/kg. We recorded the lag time, onset time, clinical duration, recovery index, recovery time, and total recovery time. RESULTS: We included 111 patients in the final analysis. The lag time, onset time, clinical duration, recovery index, recovery time, and total recovery time of the nefopam group (n = 57) were not significantly different compared with that of the control group (n = 54). CONCLUSIONS: Pretreatment with nefopam 20 mg one hour before induction of anesthesia does not have a significant influence on the onset and recovery profiles of rocuronium-induced neuromuscular block.

Mega Acer Kit® is more effective for warming the intravenous fluid than Ranger™ and ThermoSens® at 440 ml/h of infusion rate: an experimental performance study / 대한마취과학회지

BACKGROUND: Few studies have investigated the effectiveness of intravenous fluid warmers at low and moderate flow rates below 1,000 ml/h. In this study, we compared the effectiveness of three different fluid warmers at a low flow rate (440 ml/h). METHODS: We experimentally investigated the fluid warming performances of Mega Acer Kit® (Group M, n = 10), Ranger™ (Group R, n = 10), and ThermoSens® (Group T, n = 10) at 440 ml/h for 60 min. All devices were set at a warming temperature of 41℃ with preheating for 10 min. Intravenous fluids were then delivered through them. The fluid temperature (primary endpoint) was measured at 76 cm from the device after infusion for 60 min. The expected decrease in mean body temperature (secondary endpoint) after 5 h infusion for a 70 kg patient (ΔMBT5) was also calculated. RESULTS: The fluid temperature (mean [95% CI]) at 76 cm from the device, 60 minutes after the infusion was higher in group M (36.01 [35.73–36.29]℃), compared to groups T (29.81 [29.38–30.24]℃) and R (29.12 [28.52–29.72]℃) (P < 0.001). The ΔMBT5 (mean [95% CI]) was significantly smaller in group M (−0.04 [−0.04 to −0.03]℃) than that in groups T (−0.27 [−0.28 to −0.29]℃; P < 0.001) and R (−0.30 [−0.32 to −0.27]℃; P < 0.001). However, none of the fluid warmers provided a constant normothermic temperature above 36.5℃. CONCLUSIONS: Mega Acer Kit® was more effective in warming the intravenous fluid with the smallest expected change in the mean body temperature, compared to Ranger™ and ThermoSens®, at a flow rate of 440 ml/h.

Effect of dexamethasone on the onset time and recovery profiles of cisatracurium / 대한마취과학회지

BACKGROUND: The effect of dexamethasone injection on cisatracurium-induced neuromuscular block was compared according to different injection time points. METHODS: One hundred seventeen patients were randomly assigned to three groups: 8 mg of dexamethasone injected intravenously 2–3 h before anesthesia (group A), just before anesthesia induction (group B), and at the end of surgery (control group). Three minutes after anesthesia induction, intubation was performed without neuromuscular blockers, and acceleromyography was initiated. All patients received 0.05 mg/kg cisatracurium; the onset time and recovery profiles were recorded. RESULTS: Eighty patients were finally enrolled. The onset time (median [interquartile range], seconds) was significantly hastened in group A (520.0 [500.0–560.0], n = 30) compared to that in group B (562.5 [514.0–589.0], n = 22) (P = 0.008) and control group (586.5 [575.0–642.5], n = 28) (P < 0.001). The onset time in group B was faster than the control group (P = 0.015). The recovery time [mean (95% CI) minutes] was significantly hastened in group A [28.5 (27.3–29.6)] compared to that in group B [32.3 (31.0–33.6)] (P < 0.001) and control group [30.9 (29.9–31.8)] (P = 0.015). The total recovery time was significantly hastened more in group A [47.1 (45.5–48.6)] than group B [52.8 (51.6–54.0) minutes] (P < 0.001) and control group [50.5 (48.7–52.3) minutes] (P = 0.008). CONCLUSIONS: A single dose of 8 mg of dexamethasone hastened the onset and total recovery times of cisatracurium-induced block by approximately 15 and 9%, respectively if administered 2–3 h prior to surgery.

The volatile anesthetic sevoflurane attenuates ventilator-induced lung injury through inhibition of ERK1/2 and Akt signal transduction / 대한마취과학회지

BACKGROUND: Ventilator-induced lung injury (VILI) sustained during mechanical ventilator support is still a cause of a high rate of morbidity and mortality in intensive care units and in operating rooms. VILI is characterized by pulmonary inflammation that appears to be mediated by proinflammatory cytokines. This study investigates whether the volatile anesthetic sevoflurane has an anti-inflammatory effect that attenuates VILI. METHODS: Twenty one male rabbits were anesthetized and were mechanically ventilated with 50% oxygen at a peak inspiratory pressure (PIP) of 10 cmH2O, I : E ratio of 1 : 4, and positive end expiratory pressure of 5 cmH2O. All animals were randomly assigned to one of three groups that were ventilated for 5 h with 10 cmH2O of PIP (Sham group, n = 7); 30 cmH2O of PIP (Control group, n = 7); or 30 cmH2O of PIP and 0.8 vol% sevoflurane (Sevoflurane group, n = 7). The wet/dry weight (W/D) ratio and histopathology of the lung; concentration of interleukin-8 (IL-8) in the bronchoalveolar lavage fluid; and activation of extracellular signal-regulated kinases (ERK) 1/2, p38 mitogen-activated protein kinase, and Akt were measured in the lung tissue after completing the protocol. RESULTS: Histopathology indicated that the sevoflurane group showed fewer inflammatory cells and architectural changes than the control group did. The W/D ratio [(5.36 +/- 0.13) versus (6.61 +/- 0.20)], expression of IL-8 [(144.08 +/- 14.61) versus (228.56 +/- 15.13) pg/ml] and phosphorylation of ERK1/2 and Akt decreased significantly in the sevoflurane group relative to the control group. CONCLUSIONS: Sevoflurane attenuates VILI in rabbits mainly by inhibiting expression of IL-8, and Sevoflurane-induced inhibition of phosphorylated ERK1/2 and Akt might be a possible pathway for protection.

Clinical evaluation of a newly designed fluid warming kit on fluid warming and hypothermia during spinal surgery / 대한마취과학회지

BACKGROUND: The Mega Acer Kit(R) (MAK) is a newly designed heated and humidified breathing circuit that warms fluid passing through the circuit lumen. In this study, we investigated the system's efficacy for the perioperative prevention of hypothermia and fluid warming. METHODS: Ninety patients undergoing spinal surgery were enrolled in this study and randomly assigned to 3 groups based on the fluid warming device used: no fluid warming system (Group C, n = 30), via a Standard Ranger (Group R, n = 30), or via the MAK (Group M, n = 30). Distal esophageal temperatures (Teso) and infusion fluid temperature (TF) were recorded at 15 min intervals for duration of 180 min during surgery. If Teso was < 35.0degrees C, a forced-air convective warming device was used. RESULTS: Final Teso values were 34.8 +/- 0.3degrees C, 35.1 +/- 0.1degrees C, and 35.8 +/- 0.3degrees C in groups C, R, and M, respectively (P < 0.01). Teso was significantly higher in group M when compared with that in groups C and R throughout the study period (P < 0.05). The number of patients requiring a forced-air convective warming device was significantly lower in group M (n = 0) when compared with that in groups R (n = 17) and C (n = 30) (P < 0.05). The final infusion fluid temperature was higher in group M when compared with that in groups C and R throughout the study period (35.4 +/- 1.0 vs. 23.0 +/- 0.3 and 32.8 +/- 0.6degrees C; P < 0.01). CONCLUSIONS: The MAK is more effective for preventing hypothermia and for warming fluid than the Standard Ranger.

Anatomical relationship of the internal jugular vein and the common carotid artery in Korean : A computed tomographic evaluation

BACKGROUND: It is important to understand the anatomical relationship of the internal jugular vein (IJV) to the common carotid arteries (CCAs) to avoid inadvertent arterial injury. This study used computed tomography (CT) to evaluate this relationship and the changes associated with simulated 30o body rotation (SR30) in Korean subjects. METHODS: A retrospective analysis of 81 healthy adult subjects was performed using CT during physical checkups between November 2012 and September 2013. Data on both the left and right side IJV and CCA were recorded at the level of the cricoid cartilage and analyzed. The CCA was used as a reference for estimating the IJV location; this was recorded as lateral, anterior, medial, or posterior, using a segmented grid. The degree of overlap was calculated as a percentage, and changes to the anatomic relationship and overlap percentage caused by SR30 were derived. RESULTS: Prior to simulating rotation, the IJV was lateral (54.3%), posterolateral (27.2%), anterolateral (17.9%), or anterior (0.6%) to the CCA. After SR30, their position moved significantly in the anterolateral direction (P = 0.000). The degree of overlap significantly increased from 42.0 to 91.4% after SR30 (P = 0.000). No significant difference was observed between results obtained on the right and left sides before or after SR30. CONCLUSIONS: Special attention should be paid to possible CCA puncture during IJV catheterization because head or body rotation may induce anterior shifting of the IJV location relative to the CCA as well as an increased degree of overlap.

Effects of lidocaine, ketamine, and remifentanil on withdrawal response of rocuronium / 대한마취과학회지

BACKGROUND: Rocuronium has been well known to produce withdrawal response in 50-80% patients when administered intravenously. Several drugs are administered prior injection of rocuronium to prevent the withdrawal response. We compared the preventive effect of lidocaine, ketamine, and remifentanil on the withdrawal response of rocuronium. METHODS: A total of 120 patients undergoing various elective surgeries were enrolled. Patients were allocated into 4 groups according to the pretreatment drugs (Group N, normal saline; Groups L, lidocaine 40 mg; Group K, ketamine 0.5 mg/kg; Group R, remifentanil 1 microg/kg). Patients received drugs prepared by dilution to 3 ml volume before injection of rocuronium. Withdrawal responses after injection of rocuronium were graded on a 4-point scale. Hemodynamic changes were observed before and after administration of pretreatment drugs and after endotracheal intubation. RESULTS: Incidence of withdrawal response was significantly lower in group L (20%), group K (30%), and group R (0%), than group N (87%). Severe withdrawal response was observed in 5 of the 30 patients (17%) in group L, and in 9 of the 30 patients (30%) in group K. There was no severe withdrawal response in group R. Mean blood pressure and heart rate were significantly decreased in group R compared to other groups. CONCLUSIONS: It seems that remifentanil (1 microg/kg intravenously) was the strongest and most effective in prevention of withdrawal response after rocuronium injection among the 3 drugs.

Effect on thermoregulatory responses in patients undergoing a tympanoplasty in accordance to the anesthetic techniques during PEEP: a comparison between inhalation anesthesia with desflurane and TIVA / 대한마취과학회지

BACKGROUND: It has been known that positive end-expiratory pressure (PEEP) increases the vasoconstriction threshold by baroreceptor unloading. We compared the effect on the thermoregulatory responses according to anesthetic techniques between an inhalation anesthesia with desflurane and a total intravenous anesthesia (TIVA) with propofol and reminfentanil when PEEP was applied in patients undergoing tympanoplasty. METHODS: Forty-six patients with a scheduled tympanoplasty were enrolled and the patients were divided in two study groups. Desflurane was used as an inhalation anesthetic in group 1 (n = 22), while TIVA with propofol and remifentanil was used in group 2 (n = 24). PEEP was applied by 5 cmH2O in both groups and an ambient temperature was maintained at 22-24degrees C during surgery. The core temperature and the difference of skin temperature between forearm and fingertip were monitored for about 180 minutes before and after the induction of general anesthesia. RESULTS: The final core temperature was significantly higher in group 2 (35.4 +/- 0.7degrees C) than in group 1 (34.9 +/- 0.5degrees C). Peripheral thermoregulatory vasoconstriction was found in 5 subjects (23%) in group 1 and in 21 subjects (88%) in group 2. The time taken for reaching the thermoregulatory vasoconstriction threshold was 151.4 +/- 19.7 minutes in group 1 and 88.9 +/- 14.4 minutes in group 2. CONCLUSIONS: When PEEP will be applied, anesthesia with TIVA may have more advantages in core temperature preservation than an inhalation anesthesia with desflurane.

Bradycardia during laparoscopic surgery due to high flow rate of CO2 insufflation / 대한마취과학회지

No abstract available.

An experience of increased pain in patient with postherpetic neuralgia who had skin excision: A case report

Surgical excision or undermining of the affected skin in patients with postherpetic neuralgia (PHN) has been introduced as an optional treatment when other treatment failed to reduce the pain. Such peripheral operation is rarely performed due to its limited effects and invasiveness. There were few reports about long-term outcome regarding surgical excision of PHN skin. We had experienced a case of PHN patient, who underwent surgical excision 10 years ago and suffered with returned pain and severe allodynia. The pain subsided markedly after a treatment with intercostal nerve block and topical lidocaine patch.

Seizure and delayed emergence from anesthesia resulting from remote cerebellar hemorrhage after lumbar spine surgery: A case report / 대한마취과학회지

A patient with remote cerebellar hemorrhage (RCH) who was presented at the authors' hospital with seizure and delayed emergence from anesthesia after loss of cerebrospinal fluid (CSF) through a dural tear during lumbar spine surgery is described. RCH is a rare and unpredictable complication after spinal surgery. Its most common clinical features are diminished consciousness, headache, and seizure. Its mechanism is still disputed, but is probably venous bleeding secondary to significant intra- or post-operative loss of CSF. Therefore, RCH must be considered in patients with unexplained mental deterioration or disturbance upon emergence and seizure from general anesthesia after spine surgery.

Effect of magnesium sulfate pretreatment on onset and recovery characteristics of cisatracurium / 대한마취과학회지

BACKGROUND: To determine how pretreatment with magnesium sulfate (MgSO4) potentiates neuromuscular blocking agents. We investigated how the onset and recovery characteristics of cisatracurium are changed by pretreatment with MgSO4. METHODS: After Institutional Review Board approval, a total of 48 ASA I and II patients were devided into 2 groups. Patients in each group received either the MgSO4 30 mg/kg (group M) in 0.9% normal saline (total volume 100 ml) or 0.9% normal saline (control group C) alone intravenously for 15 min before induction of anesthesia with propofol, remifentanil and cisatracurium 0.15 mg/kg. Anesthesia was maintained with propofol and remifentanil. Electromyographical responses were measured by train-of-four. Lag time, onset time, total recovery time, clinical duration, recovery index, and recovery time were measured. The mean arterial blood pressure, heart rate, and ionized magnesium were also measured. RESULTS: The lag time and onset time were significantly shorter in the MgSO4 group than the control group (P 0.05). Mean arterial pressure was more significantly increased in the MgSO4 group than in the control group at the time point immediately after the administration of MgSO4. Heart rate showed no significant changes in both groups. The concentrations of ionized magnesium were significantly more increased at the all time point (P < 0.05). CONCLUSIONS: MgSO4 results in about 29% shortening of onset time of cisatracurium (0.15 mg/kg) without prolongation on the recovery of neuromuscular block.

Effect of magnesium sulfate pretreatment on onset and recovery characteristics of cisatracurium / 대한마취과학회지

BACKGROUND: To determine how pretreatment with magnesium sulfate (MgSO4) potentiates neuromuscular blocking agents. We investigated how the onset and recovery characteristics of cisatracurium are changed by pretreatment with MgSO4. METHODS: After Institutional Review Board approval, a total of 48 ASA I and II patients were devided into 2 groups. Patients in each group received either the MgSO4 30 mg/kg (group M) in 0.9% normal saline (total volume 100 ml) or 0.9% normal saline (control group C) alone intravenously for 15 min before induction of anesthesia with propofol, remifentanil and cisatracurium 0.15 mg/kg. Anesthesia was maintained with propofol and remifentanil. Electromyographical responses were measured by train-of-four. Lag time, onset time, total recovery time, clinical duration, recovery index, and recovery time were measured. The mean arterial blood pressure, heart rate, and ionized magnesium were also measured. RESULTS: The lag time and onset time were significantly shorter in the MgSO4 group than the control group (P 0.05). Mean arterial pressure was more significantly increased in the MgSO4 group than in the control group at the time point immediately after the administration of MgSO4. Heart rate showed no significant changes in both groups. The concentrations of ionized magnesium were significantly more increased at the all time point (P < 0.05). CONCLUSIONS: MgSO4 results in about 29% shortening of onset time of cisatracurium (0.15 mg/kg) without prolongation on the recovery of neuromuscular block.

The effect of gender on EC50 of remifentanil to prevent pain during injection of microemulsion propofol / 대한마취과학회지

BACKGROUND: Propofol injection pain is an unpleasant experience to patients and its prevalence can be influenced by age and gender. We determined the half maximal effective concentration (EC50) of remifentanil for preventing the microemulsion propofol injection pain in the male and female adult groups. METHODS: After institutional review board approval, a total of 60 patients were assigned into 2 groups depending on their gender: group M (male, 20-65 yr) and group F (female, 20-65 yr). Anesthesia was induced with propofol and remifentanil, by a target-controlled infusion. Target effect-site concentration (Ce) of propofol and remifentanil for the first patient started at 4.0 ug/ml and 4.0 ng/ml. Ce of remifentanil for each subsequent patient was determined by the response of the previous patient by the Dixon's up-and-down method (DUDM) with an interval of 0.2 ng/ml. After equilibration of plasma and effect site remifentanil concentration, propofol was administered, and the pain responses were observed. RESULTS: The remifentanil EC50 was 3.8 +/- 0.2 and 2.7 +/- 0.2 ng/ml in groups M and F, respectively, by DUDM. From Probit regression model, the remifentanil EC50 was 3.7 (3.0-4.3) and 2.7 (1.8-2.9) ng/ml in groups M and F, respectively. CONCLUSIONS: The remifentanil EC50 for preventing the moderate to severe injection pain of propofol was higher in males than in females.

EC50 of remifentanil to prevent pain during injection of microemulsion propofol

BACKGROUND: Microemulsion propofol that is free from lipid has been recently developed. However, it produces injection pain which is even greater than that of lipid emulsion propofol. Remifentanil has been used to reduce injection pain of propfol. So we evaluated half maximal effective concentration (EC50) of remifentanil to prevent pain during an administration of microemulsion propofol. METHODS: Remifentanil was infused to reach target effect-site concentration (Ce) before microemulsion propofol administration of target plasma-site concentration 5.0 microg/ml. Ce of remifentanil for the first patient was 4 ng/ml. Ce of remifentanil for each subsequent patient was determined by the response of the previous patient by the Dixon's up-and-down method with an interval of 0.2 ng/ml. After remifentanil reached target concentration, microemulsion propofol was administered, and the pain response was observed. Estimated EC50 and EC95 of remifentanil were calculated by probit analysis. RESULTS: Predicted EC50 of remifentanil by using Dixon's up-and- down method was 5.18 +/- 0.19 ng/ml. EC50 of remifentanil was 5.16 ng/ml (95% confidence intervals, 4.98-5.41 ng/ml) and EC95 was 5.47 ng/ml (95% confidence intervals, 5.29-7.0 ng/ml) by probit analysis. CONCLUSIONS: The EC50 of remifentanil to prevent injection pain of microemulsion propofol was 5.16-5.18 ng/ml.

Prevention of microemulsion propofol injection pain: a comparison of a combination of lidocaine and ramosetron with lidocaine or ramosetron alone / 대한마취과학회지

BACKGROUND: A microemulsion propofol causes a high incidence of pain during intravenous injection. In this study, we investigated the effect of ramosetron on pain induced by microemulsion propofol injection. METHODS: After prospective power analysis and institutional review board approval, a total of 200 ASA I and II patients undergoing general anesthesia were divided into 4 groups. They received one of the following intravenously after tourniquet application on the forearm 1 min before induction of anesthesia using microemulsion propofol; normal saline (Group N, n = 50), lidocaine 20 mg (Group L, n = 50), ramosetron 0.3 mg (Group R, n = 50) and lidocaine 20 mg plus ramosetron 0.3 mg (Group LR, n = 50) diluted into a 5 ml solution. The occlusion was released after 30 seconds and microemulsion propofol was injected over 10-15 seconds. The patients were observed and asked immediately if they had pain in the arm, and their responses were assessed. RESULTS: The incidence of pain in groups N, L, R and LR was 96%, 76%, 60% and 38%, respectively (P < 0.008). Two patients in Group LR (4.0%) and nine in Group R (18.0%) had moderate to severe pain, which was significantly lower than pain in Groups N (84.0%), L (40.0%) and R (P < 0.008). CONCLUSIONS: Pretreatment with ramosetron 0.3 mg with or without lidocaine 20 mg with a tourniquet on the forearm 30 seconds before the injection of microemulsion propofol is more effective than lidocaine 20 mg or normal saline in preventing pain from a microemulsion propofol injection.

Foot Necrosis Following Percutaneous Cannulation of the Dorsalis Pedis Artery: A Case Report / 대한구급학회지

Arterial canuulation is generally used to monitor blood pressure and sample blood for gas analysis. Radial and dorsalis pedis arteries are commonly used for arterial cannulation. It is a simple, safe, and uncomplicated procedure, but some complications have been reported, including bleeding, hematoma, infection, pseudoaneurysm, and thromboembolism. Although thromboembolism is not common, it could be serious because it can lead to digital ischemia and necrosis. We present a case of foot necrosis following dorsalis pedis artery cannulation in a 65-year-old patient who underwent small bowel resection.

The hemodynamic changes during the infusion of remifentanil for patients under sevoflurane anesthesia during arthroscopic shoulder surgery / 대한마취과학회지

BACKGROUND: In spite of its minimal invasiveness, hemodynamic instability frequently happens during arthroscopic procedures. This study was performed to investigate the clinical efficacy of remifentanil for controlling the intra-operative hemodynamics during the performance of arthroscopic shoulder surgery. METHODS: Sixty patients (ASA class 1 and 2) who were scheduled for arthroscopic shoulder surgery were recruited for this study. After the induction and maintenance of anesthesia with thiopental sodium, rocuronium bromide, sevoflurane and nitrous oxide, the patients were randomly allocated to receive either saline or three different doses of remifentanil (0.03, 0.05 or 0.07 microg/kg/min) to assess the hemodynamic changes such as the systolic blood pressure, the diastolic blood pressure and the heart rate. RESULTS: The hemodynamics in the remifentanil groups were more stable than those in the saline group (P < 0.05), but there were some cardiovascular side effects such as hypertension (remifentanil 0.03 microg/kg/min), hypotension and bradycardia (remifentanil 0.07 microg/kg/min) with using remifentanil. CONCLUSIONS: Remifentanil 0.05 microg/kg/min under anesthetic maintenance with sevoflurane showed better hemodynamic stability than the other two remifentanil groups during arthroscopic shoulder surgery.

Effect of tramadol on bispectral index during anesthesia with desflurane / 대한마취과학회지

BACKGROUND: This study is aimed to investigate the effect of tramadol on the bispectral index (BIS) during anesthesia with desflurane. METHODS: One hundred fifty adults, ASA class 1 and 2 patients, scheduled for general anesthesia for elective surgical procedures were included in this study. None of the patients were premedicated and anesthesia was induced with propofol 2 mg/kg and maintained with air-oxygen (FiO2 0.5) and desflurane, adjusted to keep the BIS between from 50 and 60. Forty minutes before completing surgery, the subjects were randomly allocated into 3 groups to receive saline (control group), tramadol 1.5 mg/kg (T1 group) or 3.0 mg/kg (T2 group) intravenously. Hemodynamics and BIS values were then recorded every 5 minutes until completion of the operation, during which time the concentrations of desflurane were not modified. RESULTS: The mean BIS values after tramadol administration weren't significantly different from the control group throughout the period of observation. No significant changes in the hemodynamics were noted, except systolic and diastolic arterial blood pressure in the T1 and T2 groups significantly increased in the first 5 minutes after the tramadol injection. CONCLUSIONS: The results indicate that the administration of tramadol while maintaining anesthesia with desflurane, adjusted to keep the BIS between 50 and 60, does not modified BIS values. So, we propose that tramadol can be safely administered as an immediate postoperative analgesia without concern about intra-operative awareness.

The comparison of the relaxant effects of propofol, thiopental, ketamine, and etomidate on isolated rat uterine smooth muscle / 대한마취과학회지

BACKGROUND: Intravenous hypnotics are used in pregnancy, labor and delivery. The aim of the present study was to investigate and compare the relaxant effects of propofol, thiopental, ketamine, and etomidate on isolated rat uterine smooth muscles. METHODS: Uterine smooth muscle preparations were obtained from non-pregnant female rats. The uterus of the rat was dissected and cut into 10 mm strips. The muscle strips were bathed in Krebs solution. After spontaneous uterine contractile activity had been accomplished, propofol, ketamine, thiopental, and etomidate in various concentrations were added cumulatively to the baths and resting tension, active tension, and frequency of contration were recorded at each concentration of agents. EC(5), EC(25), EC(50), EC(75), and EC(95) of each drug on active tension and frequency of contraction were calculated using a probit model. RESULTS: Propofol, thiopental, and etomidate reduced uterine contractions in a concentration-dependent manner. Ketamine concentrations of 10(-7) to 10(-5) M augmented uterine contractions but ketamine concentrations of 10(-4) to 10(-3) M attenuated uterine contractions. The EC(50)'s of propofol, thiopental, ketamine, and etomidate on active tension were 1.56 x 10(-5) M, 4.97 x 10(-5) M, 3.52 x 10(-4) M, and 2.73 x 10(-5) M, respectively. CONCLUSIONS: All four intravenous hypnotics relaxed the uterine smooth muscle of rats except for ketamine in low concentrations (10(-7) to 10(-5) M). Propofol had the greatest relaxant effects on isolated rat uterine smooth muscle among these hypnotics. It seems that ketamine is a suitable obstetric hypnotic agent for hypovolemic parturients and propofol is a useful hypnotic agent for uterine relaxation during pregnancy.