General anesthetic effects on compound muscle action potentials elicited by single or dual spinal cord stimulation.

The aim of this study was to determine the optimal conditions, during general anesthesia, to obtain reproducible monitoring of compound muscle action potentials (CMAPs) as a means to evaluate motor tract integrity. The CMAPs were recorded in the soleus muscle of cats and were elicited by either single or double pulse stimulations (with various amplitudes and interpulse durations) of the spinal cord via an epidural electrode. The effects of various depths of general anesthesia with halothane, enflurane, isoflurane, or propofol on such recordings were also determined.

Clinical effects of intravenously administered dantrolene.

Objective: To compare side effects after intravenous administration of dantrolene sodium in subjects susceptible to and those nonsusceptible to malignant hyperthermia (MHS and MHN, respectively).

Design: We studied two groups, six patients thought to be MHS and six assumed MHN subjects, and analyzed their responses to intravenously administered dantrolene.

Material And Methods: Dantrolene (3 mg/kg) was administered slowly into an antecubital vein, and blood samples were withdrawn from the other arm at 5 and 25 minutes after infusion.

Characterization of the high-conductance Ca(2+)-activated K+ channel in adult human skeletal muscle.

Ca(2+)-activated K+ channels of a large conductance (BKCa) in human skeletal muscle were studied by patch clamping membrane blebs and by using the three microelectrode voltage-clamp recording technique on resealed fibre segments. Single-channel recordings in bleb-attached and inside-out modes revealed BKCa conductances of 230 pS for symmetrical and 130 pS for physiological K+ distributions. Open probability increased with membrane depolarization and increasing internal [Ca2+].

Differential diagnosis of periodic paralysis aided by in vitro myography.

In vitro twitch tests were performed on excised muscle bundles from 30 periodic paralysis (PP) patients in an attempt to verify the somatic origin of PP, and to differentiate between the hypokalemic (HypoPP) and the hyperkalemic forms (HyperPP). Seventeen PP patients with a definite diagnosis of familial HypoPP, familial HyperPP (subsequently confirmed by SCN4A mutations), or thyrotoxic PP entered the study, as well as 13 patients with a history of attacks of weakness but with negative clinical provocation tests and therefore ambiguous diagnosis; 15 normal subjects served as controls. In contrast to control, bundles from patients with clear diagnosis went into sustained paralysis on exposure to Cl-free solution.

Response to succinylcholine in porcine malignant hyperthermia.

The purpose of this study was to gain new insights in the role of succinylcholine in the initiation of malignant hyperthermia (MH). The intravenous (i.v.

The effects of volatile anesthetics on the relative amplitudes and latencies of spinal and muscle potentials evoked by transcranial magnetic stimulation.

Study Design: The effects of halothane, enflurane, or isoflurane on motor-evoked potentials via transcranial magnetic stimulation were investigated in cats. Time and dose effects on muscle potentials and spinal potentials were determined by measuring relative changes in amplitudes and latencies.

Methods: In 16 cats, muscle potentials and spinal potentials were evoked transcranially using magnetic stimulation.

The cerebral and systemic effects of movement in response to a noxious stimulus in lightly anesthetized dogs. Possible modulation of cerebral function by muscle afferents.

Background: Afferentation theory predicts that agents or maneuvers that stimulate muscle stretch receptors (i.e., muscle afferents) will produce cerebral stimulation.

Lower extremity hypothermia is beneficial during infra-renal aortic cross-clamping in pigs.

The effects of lower extremity hypothermia during aortic cross-clamping are unknown. To compare the effects of lower extremity hypothermia with normothermia during aortic cross-clamping, two groups of six (25-40 kg) anesthetized pigs had their aortas cross-clamped below the renal arteries for 2 h. The cold group had their lower extremities cooled during cross-clamping to a quadriceps muscle temperature of 28 degrees C by using convective cooling.

Delayed onset of malignant hyperthermia induced by isoflurane and desflurane compared with halothane in susceptible swine.

Background: Desflurane (difluoromethyl 1-fluoro 2,2,2-trifluoroethyl ether) is a new inhalational anesthetic currently under investigation for use in humans. Recently, the authors showed that desflurane is a trigger of malignant hyperthermia (MH) in susceptible swine. To date, there has been no in vivo comparison of the relative ability of inhalational anesthetics to trigger MH.

Effects of meat quality and storage on the breakdown of adenosine triphosphate in muscle from swine.

The quality of pork is dependent on animal genotype, pre-slaughter handling, processing, maturation, and storage. We investigated the pattern of adenosine triphosphate (ATP) breakdown as it related to these factors. Samples of the thoracis portion of the longissimus dorsi muscle were obtained from 19 randomly selected German Landrace-Pietrain crossbreed swine.

The effects of sevoflurane on intracellular Ca2+ regulation in rat hepatocytes.

The effects of sevoflurane, a new volatile anesthetic agent undergoing clinical trial, on the mobilization of intracellular Ca2+ in isolated rat hepatocytes was studied. This agent produced a dose-dependent release of 45Ca2+ from internal, non-mitochondrial stores of permeabilized hepatocytes (saponin treated). However, the administration of sevoflurane to aequorin-loaded intact hepatocytes had little or no effect on intracellular [Ca2+] (i.

Convective warming therapy does not increase the risk of wound contamination in the operating room.

Although convective warming therapy is effective in preventing hypothermia in anesthetized patients, little is known concerning the potential risks of its use. Hence, this balanced cross-over study was designed to determine if the use of convective warming therapy increased the risk of wound contamination. For 4 h, eight healthy male volunteers (aged 20-25 yr) lay supine on an operating room table with their lower bodies and legs covered with a warming cover and sterile surgical drape.

A high omega 3 fatty acid diet alters fatty acid composition of heart, liver, kidney, adipose tissue and skeletal muscle in swine.

The fatty acid profiles and total lipid contents of two skeletal muscles, adipose tissue, heart, liver and kidney of swine fed a diet rich in omega 3 (n-3) fatty acids (i.e., 5% fish oil) was investigated.

The effects of halothane and isoflurane on intracellular Ca2+ regulation in cultured cells with characteristics of vascular smooth muscle.

The Ca(2+)-sensitive photoprotein aequorin was used to monitor changes in intracellular [Ca2+] within cultured cells with characteristics of vascular smooth muscle. Two cell lines were investigated: they were A10 cells, which are transformed cells originally derived from rat aorta, and BC3H1 cells obtained from mouse brain neoplasm. Transient increases in intracellular [Ca2+] were induced following exposure to two different volatile anaesthetics (halothane and isoflurane) and various vasoactive substances (acetylcholine, endothelin, histamine, serotonin and vasopressin).

Effects of topical anesthesia on essential tremor.

In a single-blinded study, the effects of skin desensitization by topical anesthesia (4% xylocaine) on six patients who had essential tremor were investigated. Resting hand tremor was monitored using an accelerometer and multiple surface electromyograms. The amplitude and frequency characteristics of the oscillations were determined using spectral analysis.

Analysis of multiple EMG and acceleration signals of various record lengths as a means to study pathological and physiological oscillations.

Quantitation of pathological and physiological oscillations are of interest to both the clinician and researcher. Power spectral analysis is a technique which allows for quantitation of both signal amplitude and frequency characteristics. For example, computer derived spectra of limb acceleration and demodulated electromyograms are used to define the properties of an oscillation.

The effects of convective cooling and rewarming on systemic and central nervous system physiology in isoflurane-anesthetized dogs.

Recent studies have demonstrated that small (i.e., 2-5 degrees C) reductions in temperature may protect the brain and spinal cord from ischemic injury.

Chronic myopathy in a patient suspected of carrying two malignant hyperthermia susceptibility (MHS) mutations.

Malignant hyperthermia (MH) is a pharmacogenetic myopathy triggered by a variety of anaesthetic agents and muscle relaxants. In humans, susceptibility to MH is inherited as an autosomal dominant trait, and susceptible patients do not show a clinically relevant myopathy unless having suffered from a MH crisis. Homozygosity for the MHS trait is thought to be an uncommon finding, and so far only a few cases of patients suggested to be homozygous for MH on the basis of pedigree information were reported and described as having a more severe form of this condition resulting in clinical symptoms also in the absence of triggering agents.

Shivering and pathological and physiological clonic oscillations of the human ankle.

Shivering and physiological and pathological clonus of the ankle were compared using power spectral and cross-correlation analysis of their respective electromyographic and acceleration waveforms. The major spectral peaks from each type of involuntary oscillation possessed similar frequencies (5-7 Hz). Soleus electromyographic activity was significantly correlated with the motion signal, whereas no correlation was observed between motion and tibialis anterior electromyographic signal.

In vitro contracture testing for determination of susceptibility to malignant hyperthermia: a methodologic update.

The in vitro contracture test determines the sensitivity of freshly obtained skeletal muscle specimens to caffeine or halothane applied to a bathing solution. Muscles from persons susceptible to malignant hyperthermia have lower contracture thresholds for these agents than do normal muscle. Thus, known concentrations of these agents must be accurately administered.

Altered Na+ channel activity and reduced Cl- conductance cause hyperexcitability in recessive generalized myotonia (Becker).

Intact muscle fibers or resealed fiber segments from 7 patients with recessive generalized myotonia were studied in vitro. All fibers had normal resting membrane potentials and normal resting [Ca2+]i several hours after removal. Contractions were characterized by slowed relaxation which was due to electrical after-activity.

Malignant hyperthermia: an altered phospholipid and fatty acid composition in muscle membranes.

There is thought to be a genetic defect within the calcium release channel of the sarcoplasmic reticulum in malignant hyperthermia (MH). This primary alteration is hypothesized to influence the function and/or structure of various muscle membrane systems; e.g.

Characterization of swine susceptible to malignant hyperthermia by in vivo, in vitro and post-mortem techniques.

We investigated German Landrace pigs from a special breeding program producing animals which were of three genotypes with respect to in vivo halothane inhalation (i.e., exposure to 3% halothane for up to 3 min): (1) Hal NN, i.