Effective doses of cisatracurium in the adult and the elderly / 대한마취과학회지

BACKGROUND: There are few information about the differences of the effective dose (ED) of cisatracurium between the adult and the elderly. We investigated the ED and the onset time of cisatracurium in the adults and the elderly. METHODS: We studied two hundred patients of the adults aged 20 through 64 years and the elderly aged ≥ 65 years, with American Society of Anesthesiologists physical status I or II. Each 100 patients with 20 patients of each dose group, randomly selected from 30, 40, 50, 60 or 70 µg/kg of cisatracurium, were randomly allocated to the adults and the elderly groups. We recorded the 0.1 Hz single twitch responses of the adductor pollicis and the onset times to maximal blockade. The magnitude of muscle relaxation was recorded by using an acceleromyography. The effect of cisatracurium on single twitch was calculated as percent reduction. After converting each drug dose into logarithm and percent reduction of the muscle reduction into probit, the EDs representing the muscle relaxation effects of 5%, 25%, 50%, 75% and 95% were estimated using the linear regression analysis. RESULTS: No significant differences were found in age, weight, height, or body mass index within or between the groups. The ED₅₀ and ED₉₅ of the adult group were 35.39 and 59.58 µg/kg. The ED₅₀ and ED₉₅ of the elderly group were 34.89 and 55.50 µg/kg, respectively. The onset times were 375.4 ± 76.9 seconds in the adult group and 369.1 ± 70.0 seconds in the elderly group. CONCLUSIONS: The ED and the onset time were not significantly different between the adult and the elderly.

Effects of magnesium sulfate on remifentanil requirements for achieving hemodynamic stability during laparoscopy assisted distal gastrectomy

BACKGROUND: Magnesium is known to reduce the requirement of analgesic agents by blocking calcium channels that exist at the neuronal and neuromuscular junctions. However, former studies have shown inconsistent results regarding this concept. Therefore, we investigated the effects of magnesium on remifentanil requirements for achieving hemodynamic stabilization in patients undergoing laparoscopic gastrectomy. METHODS: Laparoscopic gastrectomy patients (n = 30) were randomly divided into two groups. Group M received 50 mg/kg of magnesium sulfate for 15 minutes prior to the induction of anesthesia. Then, 20 mg/kg/h of magnesium was administered during the operation time. Group N was administered the same amount of saline. Anesthesia was maintained with intravenous propofol and remifentanil injection. Vecuronium (0.1 mg/kg) was administered before intubation, and an additional 0.02 mg/kg was administered if a T1 twitch response was observed during surgery. Anesthetic time was standardized to provide an appropriate comparison of all patients. During 100 minutes, total anesthetic requirements and anesthetic requirements at every 10 minutes were analyzed. Postoperative pain was controlled with a patient controlled analgesia device. RESULTS: The remifentanil and vecuronium requirements during 100 minutes were significantly lower in Group M. There was no significant difference in propofol requirements between the two groups. No significant difference was observed in mean arterial pressure and heart rate. Postoperative VAS, PONV, or shivering also did not show any difference between the two groups. CONCLUSIONS: Magnesium reduced remifentanil and vecuronium requirements but not propofol requirements. Magnesium seems to have antinociceptic properties and reduces remifentanil requirements.

The effect of high concentration of magnesium with ropivacaine, gentamicin, rocuronium, and their combination on neuromuscular blockade / 대한마취과학회지

BACKGROUND: Magnesium, ropivacaine, gentamicin, and rocuronium block neuromuscular (NM) transmission by different mechanisms. Therefore, concurrent administration of these agents may induce prolonged muscle paralysis via synergistic interaction. This study investigated the efficacy and safety of NM block caused by the administration of high concentrations of magnesium in combination with ropivacaine, gentamicin, and rocuronium. METHODS: Eighty-three left phrenic nerve-hemidiaphragms from male SD rats (150-250 g) were hung in Krebs solution. Three consecutive single twitch tension (ST, 0.1 Hz) and one tetanic tension (TT, 50 Hz for 1.9 s) were obtained before drug application and at each new drug concentration. The concentration of MgCl2 and MgSO4 in Krebs solution was increased until an 80 to 90% reduction in ST was reached. To test the effects of combinations of NM agents, a Krebs solution was premixed with MgCl2 alone, MgCl2 and ropivacaine, or MgCl2, ropivacaine, and gentamicin. The concentration of ropivacaine, gentamicin, or rocuronium was then progressively increased until an 80 to 90% reduction in ST was reached. The effective concentrations were estimated with a probit model. RESULTS: The potency of MgCl2 was greater than that of MgSO4, and pretreatment with MgCl2 increased the potency of gentamicin and rocuronium. Unexpectedly, MgCl2 did not potentiate ropivacaine, and the potency of gentamicin and rocuronium failed to show an increase when premixed with 0.5 microM ropivacaine. CONCLUSIONS: The concomitant administration of high concentrations of magnesium and ropivacaine together with clinically relevant concentrations of gentamicin or rocuronium potentiated NM blockade but not with clinically relevant concentrations of ropivacaine.

The synergistic effect of gentamicin and clindamycin on rocuronium-induced neuromuscular blockade / 대한마취과학회지

BACKGROUND: Gentamicin reduces acetylcholine release and clindamycin causes end-plate ion channel blockade. Because of these reasons, two drugs show muscular relaxant effect and potentiate the action of nondepolarizing neuromuscular agents. This study was intended to evaluate the effect of gentamicin and clindamycin on rocuronium-induced neuromuscular blockade and the interaction between these drugs. METHODS: Male Sprague-Dawley rats' phrenic nerves and diaphragms were installed in a bath containing Krebs solution. They were divided into three study groups. The first group was pre-treated with 0.1 (n = 3), 0.2 (n = 4) or 0.5 (n = 3) mM gentamicin and the tension was measured as the concentration of rocuronium was increased. The second group was experimented by increasing gentamicin on 0.25 (n = 5), 0.5 (n = 6) or 1.0 (n = 6) mM clindamycin. The final group was pre-treated with various combinations of gentamicin and clindamycin. The drug concentration was gradually increased until single twitch tension decreased by around 80%. Effective concentration was calculated using a probit model and interaction indices derived the Loewe additivity. RESULTS: The administration of gentamicin and the combination of gentamicin and clindamycin enhanced rocuronium-induced neuromuscular blockade. At 0.2 and 0.5 mM gentamicin, synergistic interactions with rocuronium were observed. Likewise, at 0.5 and 1.0 mM clindamycin, synergistic interactions with gentamicin appeared. When all three drugs were combined, in the tetanic fade, all the groups except for those administered with 0.01 mM gentamicin and 0.25 mM clindamycin showed synergistic interactions. CONCLUSIONS: This study demonstrate that gentamicin and clindamycin potentiated rocuronium induced neuromuscular blockade. Moreover, it was found that these drugs interacted synergistically.

Do bupivacaine, clindamycin, and gentamicin at their clinical concentrations enhance rocuronium-induced neuromuscular block? / 대한마취과학회지

BACKGROUND: Bupivacaine, clindamycin, and gentamicin inhibit neuromuscular (NM) conduction. When they are combined, they may synergistically reduce the effective concentration of each to the therapeutic concentration in augmenting rocuronium-induced NM block. Thus, the aim of this study was to investigate whether combinations of the three drugs, at around their therapeutic concentrations, potentiate rocuronium-induced NM block. METHODS: Fifty-seven left-phrenic nerve hemidiaphragms (Male S-D rats, 150-250 g) were hung in a 20-ml organ bath filled with Krebs solution. Three consecutive single-twitch tensions (0.1 Hz) and one tetanic tension (50 Hz for 1.9 s) were obtained. A Krebs solution was premixed with concentration sets of bupivacaine and clindamycin, bupivacaine and gentamicin, or bupivacaine, clindamycin and gentamicin. Then, the concentration of rocuronium was cumulatively increased in the Krebs solution (1, 3, 5, 7, 9, 12, 14, 16, 18, and 20 microM) until an 80% to 90% reduction in single twitch was attained. The effective concentrations for each experiment were determined with the probit model. RESULTS: The combinations of bupivacaine, clindamycin, and gentamicin enhanced rocuronium-induced NM block. When the three drugs were applied simultaneously, their concentrations were reduced to near-therapeutic levels in potentiating the action of rocuronium. CONCLUSIONS: Bupivacaine, clindamycin, and gentamicin blocked NM conduction, and when all three drugs were applied together, they augmented rocuronium-induced NM block at their near-therapeutic concentrations. Clinicians should be aware of the cooperability in NM block between drugs that interrupt NM conduction.

At therapeutic concentration bupivacaine causes neuromuscular blockade and enhances rocuronium-induced blockade / 대한마취과학회지

BACKGROUND: Partially paralyzed patients may be placed in the risk of pharyngeal dysfunction. Bupivacaine acts as acetylcholine receptor ion channel blocker and may synergistically interact with rocuronium to augment NM blockade. Thus, this study aims to elucidate whether or not, at a therapeutic concentration, bupivacaine by itself may cause NM blockade and reduce an effective concentration of rocuronium. METHODS: Twenty-two left phrenic nerve-hemidiaphragms (Male SD rats, 150-250 g) were hung in Krebs solution. Three consecutive ST, 0.1 Hz and one TT, 50 Hz for 1.9 s were obtained before drug application and at each new drug concentration. A concentration of bupivacaine in Krebs solution (n = 5) was cumulatively increased by way of 0.01, 0.1, 1, (1, 2, 3, 4, 5, 6, 7) x 10 microM. In a Krebs solution, pre-treated with bupivacaine 0 (n = 5), 0.1 (n = 5), 1.0 (n = 5), 10 (n = 2) microM, and then concentrations of rocuronium were cumulatively increased by way of 1, 3, 5, 7, 9, 12, 14, 16, 18, 20 microM. EC for each experiment were determined by a probit. The EC50's of rocuronium were compared using a Student's t-test with Bonferroni's correction. Differences were considered significant when P < 0.05. RESULTS: The potency of bupivacaine for normalized TF was 11.4 (+/- 1.1) microM. Below 30 microM of bupivacaine, the single twitch potentiation sustained despite the development of tetanic fade and partial inhibition of PTT. Bupivacaine significantly facilitated the NM blockade induced by rocuronium. CONCLUSIONS: Clinicians should be aware that bupivacaine by itself at its therapeutic concentration inhibit NM conduction and enhances rocuronium-induced muscle relaxation.

Estimation and simulation of kinetic-pharmacodynamic parameters of rocuronium by Bragg's dose-response-time model

BACKGROUND: The effect-time data involves some pharmacokinetic (PK) information. Bragg model could derive the information from pharmacodynamic (PD) data alone. After administering rocuronium, we collected tension data without these plasma concentration values. We determined kinetic-pharmacodynamic (K-PD) parameters, simulated the predictions of effect-time relation at different amount of dose, and validated the calculated infusion rates (IR) by comparing with IR directly measured. METHODS: Thirteen dexterous male patients were given rocuronium 300microg/kg during propofol-fentanyl anesthesia. Twitch tensions of the right adductor pollicis in response to supramaximal single twitch stimulation every 10 seconds were measured until muscle paralysis recovered by 70 +/- 10% of control. The above data were fitted to Bragg equation, using Tablecurve3D(R). The parameters, k1, k2, IR50, and gamma, were derived with either individual regression or population regression. The correlations between individual parameter and time, the simulation, and validation by infusing rocuronium 3.66microg/kg/min were examined. RESULTS: Based on population regression, IR50 was 3.70microg/kg/min, gamma was 4.51, k1 (keo) was 0.71/min, and k2 (k10) was 0.022/min. The longer the duration of rocuronium action was, the smaller the values of IR50 and k2 were (correlation coefficient: -0.92, -0.61, respectively). ED50 calculated (= IR50/k2) was 168microg/kg. The effects of rocuronium 3.66microg/kg/min were estimated (45% by direct measurement, 49% by population parameters, and 21% by individual parameters). CONCLUSIONS: The results of infusion rate validation suggests that population parameters may better be applicable than individual post hoc parameters to predicting the clinically relevant effect-time relations.

The antagonistic effect of neostigmine on rocuronium-, clindamycin-, or both-induced neuromuscular blocking in the rat phrenic nerve-hemidiaphragm / 대한마취과학회지

BACKGROUND: Neostigmine augments clindamycin-induced neuromuscular block and antagonizes rocuronium-induced neuromuscular block; however, it remains unclear whether neostigmine enhances the neuromuscular blocking (NMB) that is caused by combinations of rocuronium and clindamycin. The intent of this study was to determine whether neostigmine potentiates the muscle relaxation that is induced by combinations of rocuronium and clindamycin and to estimate whether both clindamycin and rocuronium have synergistic actions on NMB. METHODS: Forty-one left phrenic nerve-hemidiaphragms (from male Sprague-Dawley rats, 150-250 g) were mounted in Krebs solution. Three consecutive single twitches (ST, 0.1 Hz) and one tetanic tension (50 Hz for 1.9 s) were obtained for each increase in concentration of rocuronium or clindamycin. The concentrations of rocuronium were cumulatively increased until an 80% to 90% reduction in ST was attained in the Krebs solutions pre-treated with 0 (n = 5), 0.1 (n = 1), 0.25 (n = 1), 0.5 (n = 4), or 1.0 (n = 1) mM clindamycin or with 0 (n = 4), 0.1 (n = 1), 0.5 (n = 5), 1.0 (n = 5), or 2.0 (n = 4) mM clindamycin in combination with 250 nM neostigmine, and so were the concentrations of clindamycin in the Krebs solutions pre-treated with 0 (n = 6) or 250 nM (n = 6) neostigmine. RESULTS: Clindamycin increased the potency of rocuronium for ST and tetanic fade, irrespective of the presence of neostigmine. Neostigmine shifted the concentration-response curve of rocuronium to the right in the presence or absence of clindamycin. The interaction between rocuronium and clindamycin was synergistic when clindamycin concentrations were in excess of 0.5 mM, irrespective of the presence of neostigmine. CONCLUSIONS: Neostigmine may partially antagonize the neuromuscular block that is induced by a combination of clindamycin and rocuronium. Clinicians are advised to be aware that clindamycin synergistically increases the degree of rocuronium-induced neuromuscular block, even when neostigmine is present.

Drug interaction: focusing on response surface models / 대한마취과학회지

Anesthesiologists have been aware of the importance of optimal drug combination long ago and performed many investigations about the combined use of anesthetic agents. There are 3 classes of drug interaction: additive, synergistic, and antagonistic. These definitions of drug interaction suggest that a zero interaction model should exist to be used as a reference in classifying the interaction of drug combinations. The Loewe additivity has been used as a universal reference model for classifying drug interaction. Most anesthetic drugs follow the sigmoid E(max) model (Hill equation); this model will be used for modeling response surface. Among lots of models for drug interaction in the anesthetic area, the Greco model, Machado model, Plummer model, Carter model, Minto model, Fidler model, and Kong model are adequate to be applied to the data of anesthetic drug interaction. A model with a single interaction parameter does not accept an inconsistency in the classes of drug interactions. To solve this problem, some researchers proposed parametric models which have a polynomial interaction function to capture synergy, additivity, and antagonism scattered all over the surface of drug combinations. Inference about truth must be based on an optimal approximating model. Akaike information criterion (AIC) is the most popular approach to choosing the best model among the aforementioned models. Whatever the good qualities of a chosen model, it is uncertain whether the chosen model is the best model. A more robust inference can be extracted from averaging several models that are considered relevant.

The Care of a Jehovah's Witness with Life-threatening Anemia Refusing Ventilator Care: A Case Report / 대한구급학회지

Jehovah's Witnesses refuse the transfusion of blood and blood products, even when it can be lifesaving. Their religious conviction against receiving blood can create a difficult clinical dilemma, particularly in the life threatening situations. We report a case of a 42-year-old female Jehovah's Witness patient who had life-threatening anemia after postpartum hemorrhage. Despite severe anemia, she had a good postoperative recovery without complications.

Stress-induced cardiomyopathy during ophthalmologic surgery: A case report / 대한마취과학회지

Stress-induced cardiomyopathy or Takotsubo cardiomyopathy is a recently described clinical entity which is associated with a chest pain occurring during a stress, an abnormal ECG and/or an increase in the troponin blood level and a transient left ventricular dysfunction. Transient left ventricular dysfunction generally involves the midsection and the apex of the heart with an akinesis. We reported a case of a 55-year-old female patient who developed a stress-induced cardiomyopathy after local epinephrine use during ophthalmologic surgery.

Neuromuscular blockade and pharmacokinetic-pharmacodynamic modeling

A major goal in pharmacokinetic-pharmacodynamic (PK/PD) modeling of neuromuscular blockade (NMB) is to quantitatively estimate the dose-response relationship.Our PK/PD model consists of three submodels:PK, link kinetics, and PD.A virtual effect compartment in which the drug concentration is in equilibrium with the observed concentration is used to extract the kinetic component (keo) from the pharmacodynamic data alone.Parameters of this model are keo, Ce(50), and gamma.The underlying structural pharmacokinetics and pharmacodynamics for NMB have been well understood, and new novel PK/PD models have been substituted for the gold standard PK/PD model for NMB.The purpose of this review was to describe progress in the field of PK/PD modeling of NMB from the first model, a simultaneous PK/PD model developed by Sheiner et al in the 1970s, to some of the more complicated models.Specific PK/PD models, which accurately described the behaviors of rocuronium, mivacurium, atracurium, and cisatracurium, include the recirculatory model, the peripheral link model, the peripheral elimination model, and a nonparametric model for link kinetics.

A comparison of bispectral index and spectral entropy during sevoflurane anesthesia in children

BACKGROUND: Bispectral index (BIS) is a useful tool to assess depth of anesthesia. Recently, spectral entropy has been promoted as a monitor of anesthetic depth in adult, but its characteristics in children remains poorly defined. This study was to compare BIS and entropy indices during sevoflurane anesthesia in children. METHODS: Forty children (aged 1-12 yr) scheduled for ENT surgery, were included. Anesthesia was induced with 5.0% sevoflurane in O2 6 L/min. Tracheal intubation was performed with rocuronium 0.6 mg/kg. Heart rate, blood pressure, end-tidal sevoflurane concentration (Etsev), BIS, response entropy (RE) and state entropy (SE) were measured every 5 minutes. The correlation between BIS and entropy index and Etsev was calculated, RESULTS: The BIS, SE and RE values decreased with induction and increased with recovery. The BIS, RE, and SE values were inversely proportionally related to the Etsev. The RE and SE values were closely correlated with the BIS values (respectively r = 0.948 and r = 0.946, P< 0.001). CONCLUSIONS: We demonstrated a close correlation of SE and RE with Etsev and with BIS during sevoflurane anesthesia in children. State entropy and RE seem to be useful electroencephalographic measures of sevoflurane drug effect in children.

Influence of isoflurane, sevoflurane, desflurane and propofol on the neuromuscular blocking effect of rocuronium

BACKGROUND:Rocuronium is widely used because of rapid onset and intermediate duration of action.The volatile anesthetics potentiate the effect of nondepolarizing muscle relaxants. This study was designed to compare effects of inhalational agents with that of propofol on the muscle relaxation of rocuronium. METHODS:One hundred and thirty-six patients were divided four groups, which were given sevoflurane, isoflurane, desflurane and propofol.Anesthesia was induced with propofol 2 mg/kg and fentanyl 100microg.A ulnar nerve was stimulated with supramaximal stimuli.Anesthesia was maintained with 1.25 MAC inhalational agents or propofol of 7 mg/kg/hr for twenty minutes.Rocuronium 0.1, 0.15 or 0.2 mg/kg was administered.The degree and onset time of maximal depression was recorded.A supplementary dose of rocuronium was given so that all patients received a cumulative dose of rocuronium 0.6 mg/kg. We measured 10% recovery time. RESULTS:The ED50 of rocuronium were 0.157 in the sevoflurane, 0.167 in the isoflurane, 0.169 in the desflurane, and 0.187 mg/kg in the propofol. The ED95 were 0.296 in the sevoflurane, 0.313 in the isoflurane, 0.325 in the desflurane, and 0.407 mg/kg in the propofol.The onset time to maximal depression was prolonged in inhalational agent groups which were administered rocuronium 0.2 mg/kg. The 10% recovery time was delayed in inhalational agent groups than in propofol group. CONCLUSIONS:The inhalational anesthetics had more potent muscle relaxation effect than propofol.We suggest that the dose of rocuronium for adequate muscle relaxation be adjusted according to anesthetics used.

Influence of isoflurane, sevoflurane, desflurane and propofol on the neuromuscular blocking effect of rocuronium

BACKGROUND:Rocuronium is widely used because of rapid onset and intermediate duration of action.The volatile anesthetics potentiate the effect of nondepolarizing muscle relaxants. This study was designed to compare effects of inhalational agents with that of propofol on the muscle relaxation of rocuronium. METHODS:One hundred and thirty-six patients were divided four groups, which were given sevoflurane, isoflurane, desflurane and propofol.Anesthesia was induced with propofol 2 mg/kg and fentanyl 100microg.A ulnar nerve was stimulated with supramaximal stimuli.Anesthesia was maintained with 1.25 MAC inhalational agents or propofol of 7 mg/kg/hr for twenty minutes.Rocuronium 0.1, 0.15 or 0.2 mg/kg was administered.The degree and onset time of maximal depression was recorded.A supplementary dose of rocuronium was given so that all patients received a cumulative dose of rocuronium 0.6 mg/kg. We measured 10% recovery time. RESULTS:The ED50 of rocuronium were 0.157 in the sevoflurane, 0.167 in the isoflurane, 0.169 in the desflurane, and 0.187 mg/kg in the propofol. The ED95 were 0.296 in the sevoflurane, 0.313 in the isoflurane, 0.325 in the desflurane, and 0.407 mg/kg in the propofol.The onset time to maximal depression was prolonged in inhalational agent groups which were administered rocuronium 0.2 mg/kg. The 10% recovery time was delayed in inhalational agent groups than in propofol group. CONCLUSIONS:The inhalational anesthetics had more potent muscle relaxation effect than propofol.We suggest that the dose of rocuronium for adequate muscle relaxation be adjusted according to anesthetics used.

Analysis of the rocuronium-vecuronium interaction on tetanic fade based on a generalized response surface model with varying relative potencies / 대한마취과학회지

BACKGROUND: Some studies have shown that rocuronium and vecuronium have additive, or synergistic effects on muscle relaxation based on the Loewe additivity. Therefore, we performed a fit of tetanic fade data to a generalized response surface model with varying relative potencies proposed by Kong and Lee (KLGRS) to evaluate the usefulness of KLGRS for capturing the interspersed drug interactions and to characterize the interaction between the two drugs. METHODS: Left phrenic nerve-hemidiaphragms (Male Sprague-Dawley rats, 150-250 g) were mounted in Krebs solution. Supramaximal electrical stimulation (0.2 ms, rectangular) of 50 Hz for 1.9 s to the phrenic nerve evoked tetanic contractions that were measured with a force transducer. Each preparation was exposed to one of 4 vecuronium concentrations (0.0, 1.5, 2.5, and 3.0 microM), or one of 4 rocuronium concentrations (0.0, 3.0, 4.5, and 5.5 microM). Subsequently the adequate amount of rocuronium was added to a vecuronium bath and that of vecuronium was added to a rocuronium until an 80-90% increase in tetanic fade was achieved. We then fitted the modified KLGRS models to the above data, after which we selected the best model, based on 5 methods for determining goodness of fit. Using this method, we obtained the response surface, as well as contour plots for the response surface (i.e. isoboles), the polynomial function and the interaction index. RESULTS: The model with the constant relative potency ratio and 8 parameters was found to best describe the results, and this model reflected well the characteristics of the raw data. In addition, the two drugs showed a synergistic interaction in almost every area and an antagonistic one in a very narrow area. CONCLUSIONS: KLGRS was found to be a useful method of analyzing data describing interspersed drug interactions. The interaction between rocuronium and vecuronium was found to be synergistic.

Potentiation by Propranolol of the Skeletal Neuromuscular Block Caused by Rocuronium / 대한마취과학회지

BACKGROUND: Propranolol potentiates the effect of neuromuscular blocking agents and induces myasthenic syndromes through curare-like and local anesthetic activities.The purpose of this study was to determine if propranolol potentiated the neuromuscular block caused by rocuronium during both single (0.1 Hz) and tetanic stimulation (50 Hz for 1.9 seconds). METHODS: Left phrenic nerve-hemidiaphragms (Male Sprague-Dawley rats, 150-250 g) were mounted in Krebs solution, and three consecutive single twitches and one tetanic tension were obtained prior to each treatment. Each preparation was exposed to one of 4 propranolol concentrations (0, 1.0, 2.5, 5micrometer), 5micrometer propranolol with 2micrometer norepinephrine or 2micrometer norepinephrine alone and the concentration of rocuronium was then increased cumulatively until a 80% reduction of single twitch occurred.The effects of the drugs used were allowed to reach a steady state by waiting for 20 minutes at each concentration before measuring the tension. Effective concentrations of rocuronium at each treatment were calculated using a probit model.Differences between treatments were tested with student's t-test and Bonferroni's correction with a P < 0.05 being regarded as significant. RESULTS: The neuromuscular block caused by rocuronium was augmented by propranolol, however the augmentation caused by propranolol was not reversed by norepinephrine. CONCLUSIONS: The results of this study indicate that the potentiation by propranolol of the neuromuscular block caused by rocuronium is independent of its adrenoceptor blocking action.

The effect of fentanyl pretreatment on myoclonus during induction of anesthesia with etomidate in elderly patients / 대한마취과학회지

BACKGROUND: Etomidate is frequently used as an induction agent in the elderly patients. This study was done to determine whether etomidate-based induction can provide hemodynamic stability and fentanyl decreases the incidence of myoclonus. METHODS: Eighty ASA II or III patients older than 65 years were randomly allocated to four groups. Group 1 (n = 20) received etomidate 0.2 mg/kg after normal saline 3 ml, Group 2 (n = 20) received etomidate 0.25 mg/kg after normal saline 3 ml, Group 3 (n = 20) received fentanyl 2 ug/kg before the administration of etomidate 0.2 mg/kg, Group 4 (n = 20) received fentanyl 2 ug/kg before the administration of etomidate 0.25 mg/kg. The time interval from etomidate infusion to loss of eyelash reflex, to decrease bispectral index (BIS) 50, to intubation were recorded. We measured hemodynamic change, the BIS index, the incidence, duration and grade of myoclonus. RESULTS: There were no significant differences in time interval, mean arterial pressure (MAP), BIS index between groups. MAP and HR were increased after intubation in all groups. The incidence of myoclonus were 25%, 30%, 0%, 15% respectively. There were no significant differences in incidence and duration of myoclonus between 4 groups, but group 3 had reduced incidence compared with group 1. CONCLUSIONS: Loss of consciousness and hemodynamic changes during induction with 0.2 mg/kg and 0.25 mg/kg of etomidate were appropriate. Pretreatment with fentanyl and small dose of etomidate decrease the incidence of myoclonus.

Succinylcholine-induced phase II block and pharmacodynamics in rat diaphragm

BACKGROUND: Succinylcholine causes phase II block by a large dose or a prolonged exposure. There are rare data in a pharmacodynamics of phase II block. The purpose of this study was to investigate a concentration-response relationship, the occurrence and recovery of phase II block, and to clarify whether pretreatment of succinylcholine potentiates muscle relaxation caused by rocuronium. METHODS: Hemidiaphragm-phrenic nerve preparations were dissected from male Sprague-Dawley rats (150-250 g). Preparations were bathed in Krebs' solution, then maintained at 32oC, and saturated with a mixture of 95% O2 and 5% CO2. Isometric forces made with supramaximal stimulations (0.1 Hz, and 50 Hz for 1.9 s) to the phrenic nerve, were measured with a force transducer, before and after each treatment. Succinylcholine, 10, 20, 40, 60 and 80microM were cumulatively added to the bath. Succinylcholine 80microM (for 100 min) or succinylcholine 300microM (for 20 min) was washed out. After succinylcholine 300microM (for 20 min), or 0microM as pretreatment was washed out, rocuronium, 2, 4, 8, 12, 16, 20microM were cumulatively added to the bath. RESULTS: The potencies of single twitch, peak tetanic tension and tetanic fade for succinylcholine were 36.1, 26.0, 20.7microM. Irrespective of dose or exposure duration, the recovery of muscle relaxation caused by succinylcholine was almost complete around 20 min after succinylcholine was washed out. CONCLUSIONS: Tetanic fade occurred at a lower concentration of succinylcholine than single twitch. The recovery from phase II block was relatively rapid if the concentration of succinylcholine is sufficiently low.

The Effects of Anesthetic Agents on Emergence Delirium in Pediatric Strabismus Surgery / 대한마취과학회지

BACKGROUND: This study was designed to compare the effects of anesthetic methods used recently on emergence delirium in pediatric strabismus surgery. METHODS: Two hundred and thirty two children, aged 2-10 years, undergoing strabismus surgery, were randomly assigned to one of eight groups; ketamine-desflurane (n = 30), ketamine-sevoflurane (n = 30), ketamine-propofol (n = 30), ketamine-remifentanil (n = 27), midazolam-desflurane (n = 28), midazolam-sevoflurane (n = 30), midazolam-propofol (n = 27), and midazolam-remifentanil (n = 30). Anesthesia was induced with ketamine 1.0 mg/kg or midazolam 0.15 mg/kg. Laryngeal mask airway (LMA) was placed with rocuronium 0.5 mg/kg. Anesthesia was maintained with desflurane 5-6 vol%, sevoflurane 2-3 vol%, propofol 7-8 mg/kg/hr, and remifentanil 0.5microgram/kg/min under N2O 66% in O2. Ventilation was controlled to maintain normocapnia. The status of emergence delirium (ED) was evaluated by a blinded observer until discharge from postanesthetic care unit. RESULTS: There was no differences in age, sex, weight, height, anesthetic time, and recovery time among the eight groups. ED occurred in 54 children (23.3%), but severe ED needed treatment was not occurred. Compared with ketamine group, midazolam group showed less incidence of ED. Propofol and remifentanil groups showed less incidence of ED compared with desflurane and sevoflurane groups. ED group was more younger and more temperamental compared with nonED group. CONCLUSIONS: Propofol or remifentanil anesthesia provided less incidence of ED compared with desflurane and sevoflurane in pediatric strabismus surgery.