Articles: reflex-drug-effects.
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Randomized Controlled Trial Clinical Trial
Comparison of the effects of venlafaxine, paroxetine and desipramine on the pupillary light reflex in man.
The time-course of the pupillary light reflex response is determined by the successive activation of the parasympathetic and sympathetic innervations of the iris, the latency and the amplitude reflecting parasympathetic and the recovery time mainly sympathetic activity. ⋯ The increase in resting pupil diameter could be indicative of parasympathetic inhibition and/or sympathetic activation. The shortening of the recovery time of the light reflex response is consistent with sympathetic potentiation resulting from noradrenaline uptake blockade in the iris. The prolongation of the latency and decrease of the amplitude of the light reflex response are indicative of a parasympatholytic effect of venlafaxine. However, as venlafaxine has negligible affinity for muscarinic cholinoceptors, this effect cannot be attributed to the blockade of cholinoceptors in the iris. A possible explanation for this finding is that it reflects a central rather than a peripheral effect of the drug: the blockade of noradrenaline uptake in the brain could lead to the potentiation of the noradrenergic inhibition of central parasympathetic (Edinger-Westphal) neurones. These results demonstrate the ability of therapeutically relevant single doses of venlafaxine to potentiate noradrenergic responses in man, consistent with the blockade of noradrenaline uptake.
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Randomized Controlled Trial Clinical Trial
The site of airway irritation during induction of anaesthesia.
The aim of this investigation was to study the role of the nasal airway in mediating upper airway reflexes during induction of anaesthesia when the commonly used irritant inhalational anaesthetic agent enflurane is used. In a prospective randomised study, 40 ASA 1 & 2 day-case patients undergoing body surface surgery were recruited. Following intravenous induction using propofol, 20 patients received enflurane administered via a laryngeal mask airway (LMA), the anaesthetic vapour therefore bypassing the nasal airway. ⋯ We were unable to demonstrate any significant (p < 0.05) differences between the two groups in relation to upper airway complications (cough, breath holding, laryngeal spasm, bronchospasm and excitement). Previous work has identified the nose as a possible important reflexogenic site for upper airway reflexes in humans during anaesthesia. We have been unable to demonstrate any difference in upper airway complications when the nasal airway was included or excluded from exposure to irritant anaesthetic vapours, when administered in a clinical setting.
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Randomized Controlled Trial Clinical Trial
Alfentanil blocks reflex pupillary dilation in response to noxious stimulation but does not diminish the light reflex.
Estimation of the mu-agonist opioid effect in anesthetized and paralyzed patients is often imprecise and can be obscured by concomitant administration of drugs that affect the sympathetic nervous system, such as beta-adrenergic blocking agents. As an alternative to hemodynamic measures of opioid effect, the authors tested the hypothesis that the pupillary light reflex or pupillary reflex dilation correlated with alfentanil concentrations during isoflurane anesthesia. ⋯ Dilation of the pupil in response to a noxious stimulus is a measure of opioid effect in isoflurane-anesthetized volunteers. In contrast, the pupillary light reflex is unaffected by alfentanil during isoflurane anesthesia. These data suggest that stimulus-induced pupillary dilation may be used to evaluate the analgesic component of a combined volatile and opioid anesthetic.
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Randomized Controlled Trial Clinical Trial
Attenuation of the oculocardiac reflex after topically applied lignocaine during surgery for strabismus in children.
The effect of topical lignocaine applied to the eye muscles, on the incidence of the oculocardiac reflex during squint surgery of the medial rectus was investigated in 56 healthy children aged between 3-14 years. Three groups were studied. ⋯ Severe bradycardiac rhythm disturbances, in particular cardiac stand-still, were not observed after lignocaine had been applied. Systemic side effects of lignocaine were not seen.
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Randomized Controlled Trial Comparative Study Clinical Trial
The effects of propofol on laryngeal reactivity and the haemodynamic response to laryngeal mask insertion.
The ease of the insertion of laryngeal mask and the haemodynamic response were assessed 2 min after induction of anaesthesia with either propofol 2.5 mg kg-1 or thiopentone 4.0 mg kg-1 in 38 ASA I premedicated patients. The inserting conditions scored as excellent, good, poor and unable to insert were significantly better with propofol than with thiopentone (P < 0.001). Insertion of the laryngeal mask was followed by a transient but significant increase in both systolic (P < 0.05) and diastolic (P < 0.01) arterial pressure in the thiopentone group; there was no comparable response in the propofol group. The heart rate varied little from baseline in both groups.