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At least 127 records · Page 7Linked to original sources
PubMed1991

Assessment of residual curarization using low-current stimulation.

The present study employed train-of-four (TOF) stimulation at a current of 20 mA to assess the incidence and degree of residual neuromuscular blockade in 64 randomly selected Post Anesthesia Care Unit (PACU) patients. Group C (Control, n = 10) had received anaesthesia without nondepolarizing muscle relaxant; Group V (n = 25) had received vecuronium; and Group P (n = 29) had received pancuronium. At the end of surgery, each patient had been considered by his anaesthetist to have adequate neuromuscular function on the basis of clinical signs and tactile or visual evaluation of responses to TOF stimulation. However, upon testing in the PACU 15 min later, 45% (13 of 29) of Group P patients and 8% (2 of 25) of Group V patients had a TOF ration less than 0.70. This study indicates that residual curarization may be commonly encountered following long-acting relaxants despite qualitative intraoperative TOF monitoring. The present incidence, detected at a current of 20 mA, is consistent with previous reports which employed supramaximal TOF stimulation. We conclude that despite intraoperative monitoring, residual curarization following long-acting nondepolarizing agents is common and that it may be detected with TOF at a low stimulating current (20 mA).

Adult↗
PubMed1990

South American Strychnos species. Ethnobotany (except curare) and alkaloid screening.

The ethnobotanical uses of South American species of Strychnos L. (Loganiaceae) are reviewed, with the exception of their major rôle in the preparation of curare, which will be dealt with in detail elsewhere. Medicinal uses are less common than is the case with the African and Asian species of the genus. About 140 samples, mostly of leaves, belonging to 53 species, have been screened for alkaloids. As with species from other parts of the world, the stem bark and root bark tend to be a richer source than leaves. Nor-harman is present in extracts from S. barnhartiana leaves. Pyridino-indolo-quinolizidinone (angustine-type) bases are also found in several species. The occurrence and pharmacology of the (non-curarizing) alkaloids known to be present in South American Strychnos species is reviewed.

Alkaloids↗
PubMed2002

Postoperative residual curarization with cisatracurium and rocuronium infusions.

BACKGROUND AND OBJECTIVE: Monitoring of neuromuscular blockade still often relies on clinical judgement. Moreover, there are substantial national differences in the use of agents to 'reverse' their effects. We investigated the recovery characteristics and incidence of postoperative residual curarization after cisatracurium and rocuronium infusions for long duration interventions without systematic antagonism. METHODS: In 30 patients undergoing major surgery, we measured infusion dose requirements for rocuronium and cisatracurium during propofol anaesthesia. Infusions were discontinued at the beginning of surgical closure; spontaneous recovery of neuromuscular function was awaited in both groups. Neostigmine (50 microg kg(-1)) was administered only when a patient started to wake without a train-of-four ratio (TOF) of 0.9. RESULTS: In the cisatracurium and rocuronium groups, four (27%) and one (7%) patients, respectively, had a TOF ratio > or = 0.9 at the end of surgery. The TOF ratio in each group at that time was 51 +/- 32% for cisatracurium and 47 +/- 31% for rocuronium (P = 0.78). Six patients (40%) in the cisatracurium group and seven (47%) in the rocuronium group required neostigmine. The TOF ratio at the time of reversal was 63 +/- 7% for cisatracurium and 40 +/- 19% for rocuronium (P = 0.01). The time interval between the end of surgery and a TOF ratio of 0.9 was 10 +/- 9 min for cisatracurium and 18 +/- 13 min for rocuronium (P = n.s.). CONCLUSIONS: Patients receiving a cisatracurium or rocuronium infusion have a high incidence of postoperative residual curarization when the block is not antagonized. When 'reversal' is not attempted, cisatracurium seems to be safer than rocuronium.

Androstanols↗
PubMed1977

Audiogenic seizures in curarized mice.

Previous experiments have indicated that interference with somatosensory feedback from convulsive movements may lessen the severity of audiogenic seizures in susceptible rodents. For further investigation of this phenomenon, mice were partially immobilized with tubocurarine chloride to attenuate convulsive movements and somatosensory input associated with such movements. In Experiment 1, seizures of mice injected with .15 mg/kg were evaluated behaviorally and compared with seizures of saline-injected litter-mates. The likelihood of clonic-tonic seizures in curarized mice was as high as that of control mice, although convulsive movements were somewhat less violent and seizure fatalities were markedly reduced. In Experiment 2, seizures of mice given .25 mg/kg were evaluated with electroencephalography, and records were compared with those of controls. Despite the near absence of behavioral signs of convulsions, electroencephalograms of curarized mice showed that audiogenic seizures readily occurred. The findings suggest that audiogenic seizures are centrally "programmed" and do not require feedback from convulsive movements. However, it may be possible to disrupt the central "program" by introducing appropriate somatosensory input not normally encountered during audiogenic seizures.

Acoustic Stimulation↗
PubMed1984

Partial curarization in the postoperative period.

Forty-eight patients subjected to elective surgery were randomly selected for evaluation of neuromuscular transmission in the postoperative period. All patients were anaesthetized with thiopentone, nitrous oxide, fentanyl and pancuronium. On arrival in the postoperative ward, alertness, ability to sustain head lift and the train-of-four (TOF) ratio were estimated. Twenty-five percent of the patients had a markedly impaired neuromuscular transmission which was not acceptable from a clinical standpoint. The given dose of pancuronium was not excessively high and a fairly long time had elapsed between reversal and TOF-ratio measurement. There was a poor correlation between TOF ratio and ability to sustain head lift. The study indicates that residual curarization is a not uncommon fact which clinically is hard to assess. The only wat to avoid residual curarization seems to be to monitor the neuromuscular transmission during anaesthesia.

Adult↗
PubMed1989

Residual curarization in the recovery room: atracurium versus gallamine.

Residual curarization in the recovery room was evaluated in 19 patients randomly allocated to two groups with nine and ten patients in each group, respectively. In one group atracurium was used for relaxation, and gallamine was used in the other. Anaesthesia was achieved with thiopental, diazepam, fentanyl and nitrous oxide in oxygen. Mean train-of-four (TOF) ratio in the gallamine and atracurium group was 0.63 and 0.91, respectively. Fifty per cent of the patients in the gallamine group had TOF ratios below 0.70, and none of these patients were able to sustain a head lift for 5 s. All patients in the atracurium group had TOF ratios above 0.70, and all of them were able to lift their head for 5 s. All patients were fully awake when they were evaluated, and no patient had any sign of respiratory difficulty. We conclude that residual curarization in the recovery room remains a problem and that this problem seems to be reduced when muscle relaxants of intermediate duration of action are used for relaxation during operation.

Adult↗
PubMed1992

Studies on curare-like action of 2,2',2''-tripyridine in the mouse phrenic nerve-diaphragm.

1. The curare-like action of 2,2',2''-tripyridine (a synthetic by-product of the herbicide, paraquat) was studied in mouse phrenic nerve-diaphragm preparation. The inhibition by 2,2',2''-tripyridine of nerve-evoked twitches was dependent on the concentration, ranging from 1 to 100 microM, which had no significant effect on the twitch amplitudes evoked by direct muscle stimulation. 2. The twitch inhibition by 2,2',2''-tripyridine was reversible and could be antagonized by anticholinesterase agents such as neostigmine, physostigmine as well as ecothiophate. 3. Pretreatment with either 0.7 microM (+)-tubocurarine or 2.2 microM succinylcholine shifted the concentration-inhibition curve of 2,2',2''-tripyridine to the left. 4. 2,2'2''-Tripyridine inhibited not only acetylcholine-induced contracture of the denervated mouse diaphragm but also that of the chick biventer cervicis muscle. Like (+)-tubocurarine, 2,2',2''-tripyridine protected the twitches from the inhibition by alpha-bungarotoxin and also specifically inhibited the binding of [125I]-alpha-bungarotoxin to the mouse diaphragm. All of these findings indicate that 2,2',2''-tripyridine possesses curare-like action and inhibits the muscle contractions through binding to postsynaptic acetylcholine receptors. 5. The postsynaptic inhibition exhibited by 2,2',2''-tripyridine was also implicated in the tetanic fade, a decrease in the amplitude of miniature endplate potential (m.e.p.p.) and endplate potential (e.p.p.). 6. The clinical implication of these findings is that 2,2',2''-tripyridine may be involved in the cause of respiratory failure in paraquat-intoxicated workers since 2,2',2''-tripyridine is a by-product of paraquat synthesis.

Animals↗
PubMed1989

Autonomic blockade and cardiovascular responses to static exercise in partially curarized man.

1. The cardiovascular responses, heart rate and mean arterial pressure, were followed in seventeen human subjects who performed static handgrip contractions for 2 min at the same absolute force (15% of the initial maximal voluntary contraction strength) before and during partial curarization. In control contractions the rate of perceived exertion was 10 exertion units, 16 units in contractions with tubocurarine which could be maintained and 20 units in contractions that could not be maintained. Control contractions increased mean arterial pressure by 6 mmHg from 89 mmHg while heart rate was unchanged from the resting value of 68 beats min-1. With tubocurarine, larger increases in mean arterial pressure of 11 mmHg and for heart rate of 8 beats min-1 were obtained during maintained contractions, and 15 mmHg and 16 beats min-1, respectively, during non-maintained contractions. 2. Atropine increased resting heart rate and blood pressure with tubocurarine to 107 beats min-1 and 98 mmHg, respectively, in seven subjects. The blood pressure response to exercise with tubocurarine was unaffected by atropine, but the heart rate increase was reduced from 15 to 4 beats min-1. 3. Propranolol reduced resting heart rate with tubocurarine to 56 beats min-1 with no effect on blood pressure in seven subjects. The cardiovascular responses to exercise with tubocurarine were unaffected by propranolol. In contrast, phentolamine reduced resting blood pressure with tubocurarine to 80 mmHg without affecting heart rate in seven subjects. Exercise responses with tubocurarine were unaffected by phentolamine. Combinations of atropine and propranolol in fourteen subjects or atropine and phentolamine in five subjects showed similar results during exercise with tubocurarine as with the sole use of the agents used to block autonomic receptors. 4. The results suggest that when partial curarization induces a disproportion between the signal from central command and that from exercising muscles, the larger signal arising from central command determines the magnitude of the cardiovascular responses. The centrally generated heart rate response is in part caused by vagal withdrawal. However, the blood pressure response cannot be attenuated by the sole use of alpha- or beta-receptor adrenergic blockade or combinations of these with atropine. This suggests that there may be greater redundancy in the autonomic control of blood pressure than in the vagal control of heart rate associated with central command during static exercise in man.

Adult↗
PubMed1975

Regional curare for the reduction of the safety factor in human motor end-plates studied with single fibre electromyography.

A method employing six minutes of regional curarization with 0.5 mg D-tubocurarine and single fibre electromyographic measurements (SFEMG) was used in order to study the effect of an additional small dose of D-tubocurarine. The effect of the additional dose was most pronounced in terms of increased jitter, on motor end-plates with the initially highest jitter. The combination of regional curarization and SFEMG jitter recordings offers a sensitive technique for detecting mild effects of various drugs on neuromuscular transmission not detectable with decrement investigations.

Action Potentials↗
PubMed1980

Diaphragmatic function in healthy subjects during partial curarization.

Diaphragmatic function estimated by transdiaphragmatic pressure (Pdi) was studied in eight normal subjects during progressive partial paralysis with d-tubocurarine (dTc). Dynamic Pdi was measured during quiet tidal breathing, maximum deep inspiration, and 12-s maximum voluntary ventilation (MVV). Maximum static transdiaphragmatic pressure (Pdimax) was also measured during maximum static inspiratory efforts at four lung volumes. The maximum effect of dTc at a cumulative dose of 0.2 mg/kg abolished head-lift and handgrip ability. Pdimax at functional residual capacity was decreased to 42% of its control value indicating significant diaphragmatic weakness at this level of curarization. The weakness had no inpact on quiet breathing and a moderate effect on maximum inspiration. In either case Pdi represented an increasing fraction of Pdimax. MVV fell significantly before the Pdi during the maneuver decreased. This decreased MVV in curarized subjects reflects upper airway obstruction caused by pharyngeal muscle weakness and the diminished contribution of the other respiratory muscles that are important at high levels of ventilatory effort but more sensitive to effects of dTc.

Adult↗
PubMed1980

Function of respiratory muscles during partial curarization in humans.

The effects of submaximal neuromuscular blockade (SMNB) on the recruitment (or derecruitment) of the respiratory muscles during different types of respiratory maneuvers were studied in four healthy males infused slowly with pancuronium. The effects on lung mechanics were similar to those observed previously in that lung recoil pressure during inspiration did not change while the chest wall pressure-volume (PV) curve was shifted to the right (Rahn diagram). In each subject, SMNB produced a large increase in abdominal (gastric) and transdiaphragmatic pressures at any given lung volume during inspiration, reflecting greater diaphragmatic contribution to respiratory pressure swings. In addition, using concentric needle electrodes, we observed a marked fall in electrical (tonic and phasic) activity in the abdominal and in the intercostal/accessory muscles during SMNB but a slight increase in diaphragmatic activity. This pattern of changes was accentuated as ventilation increased. These findings indicate that the diaphragm is more resistant to curare than the other respiratory muscles in humans and that the transposition of the chest wall PV curve during SMNB is related to a loss of tonic activity in the intercostal musculature. The difference in sensitivity toward curare between the diaphragm and the other respiratory muscles is probably related to a difference in the safety margin at the neuromuscular synapses.

Adult↗
PubMed1981

Cough dynamics during progressive expiratory muscle weakness in healthy curarized subjects.

The dynamics of voluntary cough were studied in healthy supine subjects during four successive infusions of d-tubocurarine (dTc) (0.05 mg/kg) to assess the effects of progressive expiratory muscle weakness on cough performance. Curarization produced a progressive decline in maximal static expiratory muscle strength (PEmax) measured at the mouth and in pleural pressures (Ppl) generated during coughing. Expiratory flow rates during coughing did not decrease except during the initial cough from total lung capacity with the last dTc dose (18% below control). This was associated with a decrease in end-inspiratory volume prior to coughing and with a marked decrease in Ppl to 30% of control. Although the decrease in flow rates was minimal compared with Ppl, flow patterns suggest that dynamic airway compression was reduced during these coughs. We conclude that the principal effect of the expiratory muscle weakness in curarized subjects is to reduce the cough-induced dynamic compression and linear velocity of airflow though the major intrathoracic airways.

Adult↗
PubMed1977

Critical assessment of the local curare test in myasthenia gravis.

In a group of 60 patients of which 30 were affected by myasthenia, we used the regional curare test. The results were evaluated from a critical point of view and were then compared with the results obtained by the repetitive stimulation of the circumflex nerve, deriving from deltoid muscle. We considered too the specificity of the regional curare test for the evaluation of ocular myasthenia.

Action Potentials↗
PubMedDate not supplied

Acoustic reflex response during curare-induced weakness.

The acoustic stapedial reflex (AR) was measured in five healthy subjects during intravenous administration of d-tubocurarine in four equal doses totaling 0.2 mg/kg. The behavior of the reflex in the face of progressive muscle weakness was assessed. Amplitude changes in the AR elicited by pulsed tones were compared to measurements of maximum respiratory pressures reflecting respiratory muscle strength. Total curare dose averaged 16.1 mg and produced symptoms progressing from mild diplopia with the initial dose to absence of hand-grip and head-lifting ability with the final dose. Peak-to-peak amplitude of the AR decreased progressively with each dose of curare. Effects were not strictly additive but showed the largest change with the last dose. Decreases in expiratory muscle strength closely paralleled changes in the AR, whereas changes in inspiratory muscle strength were less marked than the AR, especially with mild weakness. Therefore we concluded that the AR is a valid and sensitive index of neuromuscular transmission which has an advantage over most tests of muscle strength since subject effort and cooperation do not influence test results.

Adult↗
PubMed1985

Equipotency of anti-curare activity of 4-aminopyridine and 3,4-diaminopyridine in anesthetized rats.

In the curarized preparation, 3,4-diaminopyridine (3,4-DAP) and 4-aminopyridine (4-AP) were equiactive in their ability to antagonize d-tubocurarine caused complete depression of the indirectly elicited twitches of the sciatic nerve-tibialis anterior muscle preparation in anesthetized rats. In the non-curarized preparation, 3,4-DAP showed 2.3 to 4.0 times stronger augmentation of the indirectly elicited twitches than 4-AP, but both the drugs increased equivalently and slightly the maximally elicited twitches of the chronically denervated muscle. The results suggest that the difference of their prejunctional effects is masked by the postjunctional effects of d-tubocurarine in the indirectly elicited twitches.

4-Aminopyridine↗
PubMed1975

[The effect of 1-adamantyl radicals on curare-like activity].

In the series of polymethylene bis-ammonium salts R(CH3)2N(CH2)NN(CH3)2R . 2I--(R=CH3 or Ad) a study was made of the significance of hydrophobic 1-adamantyle radicals (1--Ad) for curare-like activity. Administration of 1-ad radicals into the cation groups of depolarizing agents (n-9--11) altered their mechanism of action and diminished their activity. Attachmeni of 1-Ad radicals to the both quarternary nitrogen atoms of the antidepolarizing agents (n=5 and 6) sharply increased their curare-like activity. The data obtained pointed to the presence of hydrophobic zones in the cholinoreceptors of skeletal muscles.

Adamantane↗
PubMed1991

Fourier series analysis of the electrophysiological pattern of fatigue in healthy human beings, after curare administration.

Real time computer analysis of the electrophysiological development of muscular fatigue after small doses of d-tubocurarine (TC), has been examined in anesthetized human beings. As compared to a decrease of frequency in the control measurements, previous studies have shown an increase of the frequency of spikes after TC administration. The present experiments were carried out on the biceps brachii of 8 healthy human volunteers maintained in isometric contraction against a constant counter load until complete fatigue occurred. The Fourier spectrum analysis showed a statistically significant shift to lower frequencies before, and a milder statistically non significant shift after TC. These results may indicate that under mild curarization the early phase of muscular contraction requires a higher number of large motor units and thus, at a later stage of the contraction the pool of available large motor units becomes smaller. This conclusion supports the hypothesis that mild curarization causes a state of initial muscular fatigue.

Action Potentials↗
PubMedDate not supplied

[Use of a magnetic field for guided transport of curare-like substances].

Magnetically carried microspheres were used to investigate whether the curare-like drugs can be selectively transported to the muscles of one of the limbs of the cat. Pyrocurine and diadonium incorporated in such microspheres primarily suppressed neuromuscular transmission in the limb placed in magnetic field as compared with the control placed outside the field. The use of magnetic microspheres cointaining pyrocurine and diadonium produced no changes in systemic arterial blood pressure, local blood flow, EEG or ECG. The method also diminished the respiratory depression produced by the curare-like substances when they are routinely used for body muscle relaxation.

Adamantane↗