No abstract available.
Muscle, Smooth* ; Relaxation*

BACKGROUND: A question was whether it was preferable to give the reversal agent when profound block was present or wait for some spontaneous recovery before antagonizing the block. This study has been conducted to evaluate the reversal effects of neostigmine with divided doses in the rabbits after pancuronium when profound relaxation(PTC=O) or the first twitch of TOF stimulation was appeared (TOF,T1) was confirmed. METHODS: Rabbits(n=60) were randomly allocated to 5 groups. After pancuronium 0.2 mg/kg intravenously, spontaneous recovery was evaluated in group 1. When the profound relaxation(PTC=O) was confirmed at 5 min. after pancuronium, neostigmine 50 ug/kg with atropine 20 ug/kg were injected in group 2. At that time, neostigmine 10 ug/kg with atropine 4 ug/kg were injected and after 3 min. neostigmine 40 ug/kg with atropine 16 ug/kg were injected in group 3. When TOF, Tl was confirmed, neostigmine 50 ug/kg with atropine 20 ug/kg were injected in group 4. At that time, neostigmine and atropine were injected in group 5 as the same way of group 3. RESULTS: The mean time from injection of pancuronium to 95% recovery was 98.9 min. in group 1, 60.3 min. in group 2, 50.9 min. in group 3, 71.0 min. in group 4 and 67.1 min. in group 5. The recovery index was significantly reduced when neostigmine was injected at TOF,T1(p<0.05). The recovery time after neostigmine with divided doses was reduced, but there was no significant difference. CONCLUSIONS: The results of present study suggested that total recovery time was reduced when neostigmine was injected earlier with divided doses than single dose unrelated to profound relaxation.
Atropine ; Muscle Relaxation* ; Neostigmine* ; Pancuronium ; Rabbits* ; Relaxation

BACKGROUND: Atracurium, a nondepolarizing muscle relaxant, is eliminated by Hofmann elimination and not affected by pseudocholinesterase(pChe). Many reports show fall in pChe activity during pregnancy and our measurement failed to prove it. However, the authors found previously the infusion rate of mivacurium, which is metabolized by pChe, to achieve surgical relaxation is decreased. So, we compared the difference in the infusion rate of atracurium between full-term pregnant and nonpregnant women. METHODS: Muscle relaxation of full-term pregnant women(C group, n=10) and nonpregnant women (Non-C group, n=10) was maintained by continuous infusion of atracurium to keep 1st response of TOF at 5 1%. After discontinuance of infusion, recovery index was measured without reversals using the accelerograph. RESULTS: There was no significant difference in infusion rate of atracurium to maintain 1st twitch response of TOF at 5 1% and recovery index between two groups. There was little correlation between the total infusion time and infusion rate, or between the total infusion time and recovery index. CONCLUSION: The atracurium infusion rate in parturients to maintain muscle relaxation was not different from that in non-parturients. For Cesarean section, the usual infusion rate of atracurium is recommended to achieve the adequate surgical relaxation.
Atracurium* ; Cesarean Section* ; Female ; Humans ; Muscle Relaxation ; Obstetrics ; Pregnancy ; Relaxation

BACKGROUND: The reversal of neuromuscular blocker might be accelerated if the anticholinesterase was administered in divided doses. This study has been conducted to evaluate the correct ratio of divided doses of neostigmine for the rapid recovery in the rabbits after pancuronium when the profound relaxation(PTC=0) was confirmed. METHODS: Rabbits(n=60) were randomly allocated to 6 groups. After pancuronium 0.2 mg/kg intravenously, spontaneous recovery was evaluated in group 1. When the profound relaxation(PTC=O) was confirmed at 5 min. after pancuronium, neostigmine 50 ug/kg was injected as a bolus in group 2. At that time, neostigmine was given at 10 ug/kg followed by 40 ug/kg 3 min. later in group 3. At that time, neostigmine was given at 20 ug/kg followed by 30 ug/kg 3 min. later in group 4. At that time, neostigmine was given at 30 ug/kg followed by 20 ug/kg 3 min. later in group 5. At that time, neostigmine was given at 40 ug/kg followed by 10 ug/kg 3 min. later in group 6. RESULTS: The mean time from injection of pancuronium to 95% recovery was 99.3 min. in group 1, 59.8 min. in group 2, 53.2 min. in group 3, 51.5 min. in group 4, 50.8 min. in group 5 and 41.1 min. in group 6. The recovery index was significantly reduced in group 6(p<0.05). CONCLUSIONS: We conclude that the recovery time is reduced when neostigmine is administered in divided doses: a larger priming dose followed by a smaller bolus at profound relaxation.
Muscle Relaxation* ; Neostigmine* ; Neuromuscular Blockade ; Pancuronium* ; Pharmacokinetics ; Rabbits* ; Relaxation

The success of accelerating the onset of neuromvacular blocking drugs by giving them in divided doses encouraged others to attempt the same "priming principle" using reversal agents. Naguib et al and Abdulatif et al demonstrated that the reversal time(time to reach a TOF of 0.75) was reduced when the reversal agent was administered in divided doses at T, 10% of control. But Donati et al and Szalados et al either could not detect any differences in the rate of reversal when anticholinestereses were administered in divided doses. This study hes been conducted to evaluate the reversal effects of neostigmine or pyridostigmine with priming principle in the rabbit after pancuronium injection when pro- found relaxation(PTC=0) was confirmed. Rabbits(n=60) were randomly allocated to 4 groups. After pancuranium 0.2mg/kg IV, the onset and recovery times were evalusted. When the profound relaxation(PTC=0) was confirmed at Smin. after pancuronium injection, neostigmine 50 ug/kg and atropine sulfate (atropine) 20 ug/kg were injected in group 1. At thst time, neostigmine 10/kg and atropine 4 ug/kg were injected and after 3min. neostigmine 40/kg and atropine 16 ug/kg were injected in group 2. At that time, pyridostigmine 250 ug/kg and atropine 20 ug/kg were injected in group 3. At that time, pyridostigmine 50 ug/kg and atropine 4 ug/kg were injected and after 3min. pyridostigmine 200 ug/kg and atropine 16 ug/kg were injected in group 4. The results were as follows :. 1) The time until 75% recovery of twitch amplitude was 53.1+/-12.4min. in group 1, 44.9+/-212.1min. in group 2, 54.9+/-9.7min. in group 3 and 48.2+/-7.1min. in group 4. The reversal times were tended to reduce when the reversal agents were administered with "priming principle" at the profound relaxation. 2) At the profound relaxation the reversal effects of neostigmine were greater than that of pyridostigmine.
Atropine ; Cholinesterase Inhibitors* ; Muscle Relaxation* ; Neostigmine ; Pancuronium ; Pyridostigmine Bromide ; Relaxation

The influence of voluntary muscle contraction and alteration of muscle length on compound muscle action potential (CMAP) was studied in 20 healthy volunteers. The CMAPs were evoked by a supramaximal stimulation and recorded by a surface electrode array. Onset latencies were not significantly changed regardless of the muscle length and contraction. On shortening of the muscle there was a decrease in an area and duration of CMAP with no significant changes in an amplitude. During muscle contractions, there was an increase in amplitude and a decrease in area and duration. On a lengthening of the muscle with relaxation, the amplitude of CMAP decreased with an increased area and duration. During a voluntary contraction, there was a decrease in amplitude, area, and duration. The results are considered due to a peripheral factor such as an alteration of temporal or spatial summation rather than a central mechanism. We conclude that in nerve conduction studies, it is important to monitor the finger position and muscle relaxation to differentiate the waveform changes from the muscle length or contraction and those from the nerve lesions.
Action Potentials* ; Electrodes ; Fingers ; Healthy Volunteers ; Muscle Contraction ; Muscle Relaxation ; Muscle, Skeletal* ; Neural Conduction ; Relaxation

Atracurium, one of the newly developed nondepolarizing muscle relaxants, is remarkable due to the intermediate duration of action from the other previously known nondepolarizing agents and the broad safety margin in patients with renal or liver disease. There have been many reports suggesting that the pharmacologic effects of the nondepolarizing muscle relaxants are influenced by dosage. In this study, we attempted to identify the specific mechanism of muscle relaxation of atracurium. Particular attention was paid to the actually delivered atracurium dose and to the degree of muscle relaxation in rabbits. The results were as follows; 1) In the atracurium 0.4 mg/kg group, the onset of action was shortened and in the atracurium 0.6 mg/kg group, it was shortened more significantly. 2) The duration of action was increased with the increase of dose: the mean duration was 895 seconds in the atracurium 0.1 mg/kg group, 1,113.7 seconds in the 0.2 mg/kg group, and 1,199.3 second is in the 0.4 mg/kg group. It was prolonged to 1,730 seconds in the atracurium 0.6mg/kg group. 3) The spontaneous recovery index showed no differences in the atracurium 0.1 mg/kg group, 0.2 mg/kg group and 0.4 mg/kg group (196.7 sec., 195.0 sec, 202.7 sec. each). But in the atracurium 0.6 mg/ kg group, it was markedly prolonged to 334 seconds. In conclusion, atracurium, like other nondepolarizing agents, produces a dose related duration of action in muscle relaxation.
Atracurium* ; Humans ; Liver Diseases ; Muscle Relaxation* ; Rabbits*

No abstract available.
Anti-Bacterial Agents ; Muscle Relaxation ; Muscles

BACKGROUND: This study was conducted to investigate the pharmacodynamic interaction between rocuronium and cisatracurium using the response surface model, which is not subject to the limitations of traditional isobolographic analysis. METHODS: One hundred and twenty patients were randomly allocated to receive one of the fifteen predefined combinations of rocuronium and cisatracurium. To study single drugs, cisatracurium 0.2, 0.15, or 0.1 mg/kg or rocuronium 0.8, 0.6 or 0.4 mg/kg doses were administered alone. To study the pharmacodynamic interaction, drugs were applied in three types of combination ratio, i.e., half dose of each drug alone, 75% of each single dose of rocuronium and 25% of each single dose of cisatracurium, and vice versa. Train-of-four (TOF) ratio and T1% (first twitch of the TOF presented as percentage compared to the initial T1) were used as pharmacodynamic endpoints, and the Greco and Minto models were used as surface interaction models. RESULTS: The interaction term α of the Greco model for TOF ratio and T1% measurements showed synergism with values of 0.977 and 1.12, respectively. Application of the Minto model resulted in U₅₀ (θ) values (normalized unit of concentration that produces 50% of the maximal effect in the 0 <θ< 1 region) less than 1 for both TOF ratio and T1% measurements, indicating that rocuronium and cisatracurium exhibit synergism. CONCLUSIONS: Response surface modeling of the interaction between rocuronium and cisatracurium, based on considerations of their effects on muscle relaxation as measured by TOF ratio and T1%, indicated that the two drugs show considerable synergism.
Drug Interactions ; Humans ; Muscle Relaxation ; Pharmacology

No abstract available.
Biofeedback, Psychology* ; Humans ; Hydrocortisone* ; Hypertension* ; Muscle Relaxation*