Sex difference in strength and size ratios between reciprocal muscle groups in the lower leg.

This study compared strength and size of reciprocal muscle groups in the lower leg between sexes. 20 young men and 14 young women volunteered as subjects. Joint torques developed during isometric maximal voluntary plantar flexion (TQPF) and dorsiflexion (TQDF) were measured using a dynamometer. Muscle volumes of plantar flexors (MVPF) and dorsiflexors (MVDF) were determined by magnetic resonance imaging. In each of the muscle groups, joint torque was significantly correlated with muscle volume in young men and women (r=0.610-0.848) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength ratio on muscle size ratio between the plantar flexors and dorsiflexors were investigated using joint torque and muscle volume. The correlations between the MVPF per MVDF and the TQPF per TQDF were significant both in young men (r=0.608) and women (r=0.773), suggesting that strength ratio is strongly affected by size ratio between the plantar flexors and dorsiflexors in young men and women.

Muscle strength and size balances between reciprocal muscle groups in the thigh and lower leg for young men.

The present study investigated whether the muscle size balance affects the muscle strength balance between reciprocal muscle groups in the thigh and lower leg. 18 young men volunteered as subjects. The joint torques developed during isometric maximal voluntary knee extension and flexion, plantar flexion and dorsiflexion were measured using a dynamometer. The muscle volumes of knee extensors and flexors, plantar flexors and dorsiflexors were determined by magnetic resonance imaging. For each of the muscle groups, the joint torque was significantly correlated with the muscle volume (r=0.644-0.847) and the y-intercept of the regression line between them was not significantly different from zero. Based on these observations, the dependencies of muscle strength balance on muscle size balance between the knee extensors and flexors and between the plantar flexors and dorsiflexors were investigated using the joint torque and muscle volume. The correlation between muscle volume ratio and joint torque ratio was significant between the plantar flexors and dorsiflexors (r=0.622) but not between the knee extensors and flexors (r=0.128). Thus, it is suggested that the strength balance is strongly affected by the size balance between the reciprocal muscle groups in the lower leg but not in the thigh.

Acute respiratory and metabolic acidosis induced by excessive muscle contraction during spinal evoked stimulation.

Spinal somatosensory evoked potentials (SSEPs) have been used to monitor spinal cord function during corrective scoliosis surgery. We report three cases in which direct epidural stimulation for measurement of SSEPs produced paraspinal muscle contraction, resulting in respiratory and metabolic acidosis. In two of the cases, SSEP-induced acidosis was observed even when only the first twitch of the train-of-four response was detectable after a second dose of muscle relaxant. In one of these two cases, the acidosis was abolished after a sufficient dose of vecuronium to ablate the twitch response. To prevent SSEP-induced respiratory and metabolic acidosis, we recommend that SSEPs should be measured only when profound neuromuscular blockade has been obtained.

[A case of pulmonary edema after electroconvulsive therapy under propofol anesthesia].

Electroconvulsive therapy (ECT) was scheduled for a 61-yr-old woman with major depression who had been taking a beta-blocker for hypertension. She underwent the first ECT under thiamylal anesthesia uneventfully. The second ECT was performed under propofol anesthesia on the next day. Immediately after ECT, the heart rate dropped from 56 to 19 beats.min-1, which was remedied by intravenous atropine. Then, the blood pressure increased to 204/108 mmHg but it was controlled by nicardipine. However, the SpO2 decreased to 84-88% under oxygen administration by mask at a rate of 3 l.min-1. The patient complained of chest discomfort and had a bloody secretion from the trachea. A chest X-ray showed a butterfly shadow. The patient was diagnosed as having neurogenic pulmonary edema and was treated in the ICU by artificial ventilation and administration of diuretics and catecholamines. These treatments proved to be successful, and the patient was discharged from the ICU 4 days later uneventfully. This case indicates that hemodynamics should be carefully monitored following ECT and that care should be taken to prevent the occurrence of complications after ECT.

The involvement of adenosine neuromodulation in pentobarbital-induced field excitatory postsynaptic potentials depression in rat hippocampal slices.

We investigated the contribution of adenosine neuromodulation to mechanisms of pentobarbital-induced depression of excitatory synaptic transmission in vitro. Transverse hippocampal slices were prepared from brains removed from isoflurane-anesthetized male Wistar rats. Field excitatory postsynaptic potentials (fEPSPs), elicited by orthodromic electrical stimulation of Schaffer collateral at 0.05 Hz, were recorded from the CA1 region in oxygenated artificial cerebrospinal fluid. Amplitude of fEPSP was analyzed for assessing drug effects. Pentobarbital (100 microM) transiently depressed fEPSPs (P<0.01); i.e., fEPSP was initially depressed to approximately 60% of control and then recovered to approximately 80% of control. The fEPSP depression was partially suppressed by pretreatment with 50 microM aminophylline, a nonselective adenosine receptor antagonist, and 0.2 microM 3, 7-Dimethyl-1-propagylxanthine, an adenosine A(1) receptor antagonist (P<0.01 each). However, the fEPSP depression was not affected by pretreatment with 10 microM 8-cyclopentyl-1, 3-dipropylxanthine, an A(2) receptor antagonist, or 10 microM bicuculline, a gamma-aminobutyric acid (GABA) A receptor antagonist. The results indicate that adenosine neuromodulation through A(1) receptors and other undefined mechanisms, which are independent from GABAergic mechanisms, are involved in pentobarbital-induced depression of excitatory synaptic transmission.

[Cardiovascular responses during laryngeal mask airway insertion in normotensive, hypertensive and chronic renal failure patients].

The hemodynamic response to the insertion of the laryngeal mask airway (LM) following induction with propofol 2 mg.kg-1 was assessed and compared in normotensive (Normal), hypertensive (HT) and chronic renal failure (CRF) patients (n = 23 in each group). Before induction, in HT and CRF groups blood pressure and rate pressure products (RPP) were higher than in Normal group (P < 0.05). Although blood pressure and RPP were decreased in every patient by induction with propofol, no patients needed vasopressor drugs. The decreases of blood pressure and RPP were larger in HT and CRF groups than in Normal group (P < 0.05). There were no differences between groups in heart rate and rate of successful LM insertion. We concluded that LM insertion with propofol 2 mg.kg-1 was an effective induction method preventing the adverse circulatory responses in normotensive, hypertensive and chronic renal failure patients.

[Intra-aortic balloon occlusion of the descending thoracic aorta for intra-abdominal hemorrhage].

Intra-aortic balloon occlusion (IABO) of the descending aorta is beneficial to rescue patients in shock following traumatic intra-abdominal hemorrhage. The authors experienced four such patients who had received IABO of the descending thoracic aorta to maintain hemodynamics prior to operation. After hemostasis, the balloon was deflated gradually. Releasing the balloon in the operating room was, however, abandoned in two patients because of severe deoxygenation and life threatening arrhythmia. In the other two patients, the balloon was successfully deflated during the operations; one of them died a week later from multiple organ failure. We conclude that shortening the aortic occlusion time as well as the treatments for adverse effects of balloon release are important in the anesthetic management of patients receiving IABO.

[Two cases of severe metabolic acidosis after monitoring of evoked spinal cord potential].

Evoked spinal cord potential (ESCP) elicited by direct spinal cord stimulation has been applied to monitor the spinal cord function during spinal surgery. We report here two patients who showed excessive muscle contraction and developed severe metabolic acidosis as a result of the stimulation of spinal cord to measure ESCP. These changes were prevented by vecuronium administration prior to ESCP monitoring. These results suggest that excessive muscle contraction by direct spinal cord stimulation may lead to metabolic acidosis. In conclusion, the use of a non-depolarizing muscle relaxant is recommended to prevent the adverse effects of ESCP monitoring.