Anesthesiology
-
The current study investigates the effects of sufentanil on cerebral blood flow velocity and intracranial pressure (ICP) in 30 patients with intracranial hypertension after severe brain trauma (Glasgow coma scale < 6). ⋯ The current data show that sufentanil (3 micrograms/kg intravenous) has no significant effect on middle cerebral artery blood flow velocity and ICP in patients with brain injury, intracranial hypertension, and controlled MAP. However, transient increases in ICP without changes in middle cerebral artery blood flow velocity may occur concomitant with decreases in MAP. This suggests that increases in ICP seen with sufentanil may be due to autoregulatory decreases in cerebral vascular resistance secondary to systemic hypotension.
-
alpha 2 Adrenoceptors are coupled to G-proteins sensitive to pertussis toxin (PTX) in the locus coeruleus. At this site, the hypnotic response to dexmedetomidine, an alpha 2 agonist, can be blocked by pretreatment with PTX. G-proteins sensitive to PTX may also be involved in the transduction of anesthetic and analgesic responses to alpha 2 agonists at supraspinal or spinal sites. To address this question the effects of pretreatment with PTX administered intracerebroventricularly, intrathecally, or a combination of the two were examined on the MAC for halothane, and the anesthetic-sparing and analgesic effects of a systemically administered alpha 2 agonist, dexmedetomidine. ⋯ Taken together with the authors' previous report, these data suggest that the hypnotic and the analgesic responses to dexmedetomidine are transduced via PTX-sensitive G-protein-coupled alpha 2 adrenoceptors but at separate sites (analgesic-spinal; hypnotic-locus coeruleus). Further studies are needed to localize the precise site(s) for the MAC-sparing effect of dexmedetomidine and to establish whether PTX-sensitive G-proteins are involved in this response.
-
The application of phase-modulated near-infrared techniques for measurement of the oxygen saturation of cerebral tissue requires both validation by conventional measures of cerebral oxygenation and determination of normal and abnormal values. This study was undertaken to validate phase-modulated near-infrared measurements of cerebral oxygen saturation by comparing them with electroencephalographic evidence of cerebral ischemia during implantation of cardioverting defibrillators. This comparison also yields an estimate of the ischemic threshold as measured with near-infrared techniques. ⋯ Near-infrared measurements reflect changes in cerebral oxygenation as indicated by electroencephalographic evidence of cerebral ischemia.
-
Although the intensity of neurostimulation (i.e., charge) is a product of current intensity and pulse duration, the effects of the latter on the amplitude of evoked response and subjective discomfort are unknown. Therefore, the authors investigated the effects of current intensity and pulse width, and their interaction with electrode placement and polarity, on force translation (FTR), accelerography (ACG), and electromyography (EMG) at the adductor pollics muscle. ⋯ The total current charge required for evoking a supramaximal neuromuscular response is much higher than previously appreciated, and electrode polarity is important in attaining a supramaximal plateau. Failure to attain (and maintain) a supramaximal stimulus allows changes in the effectiveness of neurostimulation, thus influencing the magnitude of the evoked neuromuscular response and confounding measurements of neuromuscular block.
-
Intrathecal carbachol produces consistent analgesia in animals without appreciable adverse effects. Little is known about the ability of this drug to provide analgesia as stimulus intensity is increased. Likewise, there are few data regarding interactions between carbachol and other intrathecal analgesics. ⋯ Intrathecal carbachol provides analgesia to noxious thermal stimulation of the hind paw in rats. It is relatively less effective at providing analgesia than intrathecal morphine or clonidine when stimulus intensity is raised. Intrathecal carbachol is synergistic when combined with intrathecal morphine or clonidine.