Jonas Gintautas

Neuromuscular blocking action of verapamil in cats

The effects of the calcium (slow) channel blocker verapamil, on non-cardiac excitable membranes were examined in vivo. In barbiturate anaesthetized cats, the effect of intravenously administered verapamil (0.1, 0.2, and 0.4 mg*kg-1) on isometric twitch amplitude of the flexor carpi radialis muscle, elicited by indirect and direct electrical stimulation, was determined. At all doses tested, verapamil significantly reduced muscle twitch amplitude from control values. The effect of dosage on twitch reduction was far more pronounced for indirect than direct stimulation. Full recovery to control was observed by 90 minutes only with the lowest dose (0.1 mg*kg-1IV). Reduction of twitch amplitude (direct and indirect) lasted the duration of the experiment (180 minutes) for the two higher doses of verapamil. No significant changes in blood pressure, cardiac rate or rhythm were observed. The specific site and mechanism of verapamil’s neuromuscular blocking action remains unclear. In clinical situations where potent inhalation agents, adjuncts or neuromuscular blocking agents may be used, therapeutic doses of verapamil may interact to promote muscle weakness.RésuméOn a observé les effets du vérapamil, un agent bloquant de calcium (voie lente) sur des membranes non cardiaques in vivo, Chez des chats anesthésiés avec du barbiturate, on a vérifié les effets du vérapamil administré par voie intraveineuse (0.1, 0.2 et 0.4 mg*kg-1) sur la phase isométrique de la contraction du muscle grand palmaire provoqué par stimulation électrique directe et indirecte. A toutes les doses vérifiées, le vérapamil réduisit significativement l’amplitude des contractions musculaires par rapport aux valeurs de contrôle. L’effet du dosage sur la réduction de contractions était beaucoup plus prononcé avec la stimulation indirecte que directe. La récupération au niveau du contrôle a été observée après 90 minutes seulement avec la dose la plus basse (0.1 mg*kg-1 I.V.). La réduction de contractions (directe ou indirecte) dura tout le temps de l’expérience (180 minutes) pour les deux doses plus élevées de vérapamil. On n’observa pas de changements significatifs de pression artérielle, de rhythme ni de débit cardiaque. L’endroit spécifique et le mécanisme d’action du vérapamil comme agent bloquant neuromusculaire ne sont pas éclaircis. En situation clinique où des agents actifs d’inhalation, des traitements d’appoint et des agents bloquants neuromusculaires sont administrés, des doses thérapeutiques de vérapamil peuvent interagir afin d’activer la faiblesse des muscles.

Neuromuscular and electrocardiographic responses to verapamil in dogs.

Because severe muscular weakness was noted in animals receiving verapamil in doses exceeding those used in humans, we studied the effects of verapamil on neuromuscular function and its correlation with myocardial conduction. The flexor carpi radialis and its nerves were surgically exposed in mechanically ventilated dogs during pentobarbital anesthesia. Indirect and direct electrical stimulation was applied and twitch height recorded following the intravenous administration of verapamil. Twenty animals received one of four dose schedules. The results showed a significant dose-related depression of twitch height to indirect stimulation. Twitch height to direct stimulation was reduced only zuith the highest dose. The onset of depression of indirect stimulation was temporally associated with onset of A-V conduction delay. However, recovery following indirect stimulation lagged behind recovery of the ECG by 30 min. Recovery times of twitch height following indirect stimulation ranged from 60–208 min and also were dose-related. The qualitative similarity of pancuronium and verapamil on indirect twitch height suggests a similar site of action, i.e., the neuromuscular junction. A presynaptic or postsynaptic effect of verapamil could not be discerned in this study. Verapamil may produce an unrecognized source of weakness in the anesthetized patient either alone or through interaction With anesthetic agents or adjuncts.

EFFECTS OF ISOFLURANE AND OXYTOCIN ON GRAVID HUMAN UTERUS IN VITRO

Introduction. Isoflurane (1-chloro-2,2,2triflurroethyl ether) is a well accepted inhalation anesthetic agent used in everyday clinical practice. The agent is relatively insoluble in blood, usually produces minimal hemodynamic.changes, facilitates neuromuscular blockade, and depresses cerebral activity. There are a limited number of publications reporting the depression of contractibility of human uterine muscle by isoflurane in vitro and in vivo (1,2). Blood loss during dilation and evacuation or during delivery was related to isoflurane effect (3). Oxytocin, a synthetic polypeptide, is used to elicit uterine contractions or to control uterine bleeding. The information regarding the isoflurane and oxytocin combined effect on human uterus is limited. In this study we examined the effect of isoflurane on isolated gravid human myometrium and demonstrated the reversibility of this effect.

Effects of Verapamil on Indirect Muscle Twitch Responses

The effects on indirectly elicited muscle twitch amplitude associated with the calcium (slow) channel blocker, verapamil, with or without pancuronium were investigated using isolated bullfrog sciatic nerve-sartorius muscle preparations. Verapamil (2–8 mM) produced a dose-related depression of indirect muscle twitch height (P < 0.05). Twitch response was depressed 11% below control by the lowest concentration employed and 86% by the highest concentration. Pancuronium (0.07 mM) depressed neuromus- cular function 35% below control (P < 0.05). The combination of 5 mM or 8 mM verapamil with 0.07 mM pancuronium caused significantly greater degrees of depression than either drug alone. Verapamil produced significant depression of twitch height in vitro in relatively high concentrations. The mechanism of action remains unknown. Verapamil possesses pharmacologic properties that may be unrelated to slow (calcium) channel inhibition. The reduction of muscle twitch height caused by verapamil alone (5 mM) could not be antagonized by neostigmine, calcium, or frequent washings.

Disfluent speech associated with brain damage

Abstract The frequency and type of disfluencies in the spontaneous speech of 15 people with Brocas aphasia and right hemiplegia was studied. Two aged-matched control groups (15 nonaphasic stroke patients with left hemiplegia and 15 normals) were also studied. The frequency of disfluencies in the speech of aphasics was three times greater than that in the speech of either control group. However, most of the disfluencies uttered by aphasics were of the types commonly found in speech of normals.

Epidural blood patch after thoracotomy for treatment of headache caused by surgical tear of dura

IMPLICATIONS During a right lobectomy operation, a patient with carcinoma of the lung developed postoperative headache caused by a leak of cerebrospinal fluid from an area of dura injured during the procedure. Conservative treatment was unsuccessful. Injection of 10 mL of the patients own blood into the epidural space relieved the headache.