Semi‐mechanistic models to relate noxious stimulation, movement and pupillary dilation responses in the presence of opioids

Pupillary Dilation in Response to Noxious Stimulation Predicts Sensory Block Level During Combined Epidural/General Anesthesia

Anesthesiology ◽

10.1097/00000542-199209001-00872 ◽

1992 ◽

Vol 77 (Supplement) ◽

pp. A872

Author(s):

M Larson ◽

D I Sessler ◽

M Osaki ◽

J McGuire ◽

D Blanchard ◽

...

Keyword(s):

General Anesthesia ◽

Sensory Block ◽

Noxious Stimulation ◽

Pupillary Dilation ◽

Block Level

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Alfentanil Blocks Reflex Pupillary Dilation in Response to Noxious Stimulation But Does Not Diminish the Light Reflex

Anesthesiology ◽

10.1097/00000542-199710000-00019 ◽

1997 ◽

Vol 87 (4) ◽

pp. 849-855 ◽

Cited By ~ 73

Author(s):

Merlin D. Larson ◽

Andrea Kurz ◽

Daniel I. Sessler ◽

Martha Dechert ◽

Andrew R. Bjorksten ◽

...

Keyword(s):

Plasma Concentrations ◽

Concomitant Administration ◽

Electrical Stimulus ◽

Pupillary Light Reflex ◽

Noxious Stimulation ◽

Pupillary Dilation ◽

Pupillary Reflex ◽

Light Reflex ◽

Isoflurane Anesthesia ◽

Pupillary Light

Background 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. Methods Six volunteers were anesthetized on 4 days with 0.8% isoflurane. Alfentanil was administered intravenously to target total plasma concentrations of 0, 25, 50, and 100 ng/ml. A 5-s tetanic electrical stimulus was applied to the skin. Pupil size and the pupillary light reflex were recorded before and after alfentanil administration, and before and for 8 min after the stimulus. Results Alfentanil exponentially impaired reflex pupillary dilation, decreasing the maximum response amplitude from 5 mm at 0 ng/ml, to 2.3 mm at 25 ng/ml, to 1.0 mm at 50 ng/ml, and finally to 0.2 mm at 100 ng/ml. In contrast, only the highest concentration of alfentanil depressed the dilation of the pupil in the first 2 s after the stimulus. Alfentanil administration had no effect on the pupillary light reflex. Conclusions 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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Sympathetic Nervous System Does Not Mediate Reflex Pupillary Dilation during Desflurane Anesthesia

Anesthesiology ◽

10.1097/00000542-199610000-00009 ◽

1996 ◽

Vol 85 (4) ◽

pp. 748-754 ◽

Cited By ~ 46

Author(s):

Merlin D. Larson ◽

Farzin Tayefeh ◽

Daniel I. Sessler ◽

Malcolm Daniel ◽

Mimi Noorani

Keyword(s):

Nervous System ◽

Sympathetic Nervous System ◽

Pupil Size ◽

Light Stimulus ◽

Noxious Stimulation ◽

Pupillary Dilation ◽

Light Reflex ◽

Infrared Pupillometry ◽

Sympathetic Nervous ◽

End Tidal

Background Pupil size is determined by an interaction between the sympathetic and parasympathetic divisions of the autonomic nervous system. Noxious stimulation dilates the pupil in both unanesthetized and anesthetized humans. In the absence of anesthesia, dilation is primarily mediated by the sympathetic nervous system. In contrast, pupillary dilation in cats given barbiturate or cloralose anesthesia is mediated solely by inhibition of the midbrain parasympathetic nucleus. The mechanism by which noxious stimuli dilate pupils during anesthesia in humans remains unknown. Accordingly, the authors tested the hypothesis that the pupillary dilation in response to noxious stimulation during desflurane anesthesia is primarily a parasympathetic reflex. Methods In six volunteers, the alpha-I adrenergic receptors of the iris musculature were blocked by unilateral administration of topical dapiprazole; six other volunteers were given unilateral topical tropicamide to block the muscarinic receptors in the iris. Desflurane anesthesia was subsequently induced in all volunteers. Sympathetic nervous system activation, with reflex dilation of the pupil, was produced by noxious electrical stimulation during 4% and 8% end-tidal desflurane, and by a rapid 4%-to-8% step-up in the desflurane concentration. Pupil diameter and the change in pupil size induced by a light stimulus (light reflex amplitude) were measured with infrared pupillometry. Results Dapiprazole drops produced a Horner's miosis, but pupils were equally small after induction of anesthesia. Pupillary dilation after noxious stimulation and desflurane step-up was identical in the unblocked and dapiprazole-blocked pupils. After tropicamide administration, the pupil was dilated and the light reflex was completely inhibited. Noxious stimulation nonetheless produced a slight additional dilation. Conclusions During desflurane anesthesia, pupillary dilation in response to noxious stimulation or desflurane step-up is not mediated by the sympathetic nervous system (as it is in unanesthetized persons). Although inhibition of the pupillo-constrictor nucleus may be the cause of this dilation, the mechanism remains unknown.

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