Anesthesiology
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Randomized Controlled Trial Clinical Trial
Dose-response pharmacology of intrathecal morphine in human volunteers.
Intrathecal morphine sulfate (ITMS) administration was introduced into clinical practice in 1979. Inadequate information exists delineating ITMS respiratory effects in the dosage range most frequently employed today. This study evaluated 0.2, 0.4, and 0.6 mg ITMS in male volunteers. ⋯ ITMS produced dose-related analgesia and respiratory depression in nonsurgical healthy, young, adult male volunteers. Respiratory depression was significant after 0.2 or 0.4 mg and profound and prolonged after 0.6 mg. No clinical signs or symptoms, including respiratory rate, reliably indicated hypoxemia. Pulse oximetry reliably detected hypoxemia after ITMS, and supplemental nasal oxygen (2 L/min) effectively corrected this hypoxemia.
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The LMA is a useful airway device for most adult and pediatric patients. It is easy and atraumatic to insert, with minimal somatic and autonomic responses from the patient. ⋯ In addition, the LMA facilitates blind and fiberoptic techniques of intubation, but its role in the emergency scenario has yet to be established. The preliminary experience gained with this device in Europe and Australasia suggests that it may also transform contemporary anesthetic practice in the United States.
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Clinical Trial
Pupillary assessment of sensory block level during combined epidural/general anesthesia.
Currently, no reliable method exists to determine the level of sensory block during combined epidural/general anesthesia. However, the pupil dilates markedly in response to noxious electrical stimulation during general anesthesia. Presumably, sensory block produced by epidural anesthesia decreases or obliterates this autonomic response. Accordingly, we tested the hypothesis that pupillary dilation in response to noxious stimulation would predict the level of sensory block achieved during combined epidural/general anesthesia. ⋯ We conclude that dilation of the pupil in response to electrical stimulation is an accurate test of the sensory block level during combined epidural/general anesthesia.
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The pupillary light reflex often is evaluated in the perianesthetic period to assess drug effects and brainstem function. Mild hypothermia alone or combined with isoflurane does not impair pupillary responses. Although perioperative hyperthermia is less common than hypothermia, abnormal increases in core temperature remain an important thermal disturbance. Accordingly, the pupillary effects of hyperthermia alone and hyperthermia combined with isoflurane and enflurane were evaluated. Additionally, the effects of nitrous oxide on pupillary responses were determined. ⋯ Anesthetic-induced inhibition of the pupillary response to light is reversed partially by core hyperthermia. In contrast to enflurane and isoflurane, 60% N2O has little effect on the pupil.