Anesthesiology
-
Comparative Study
Comparison of twitch depression of the adductor pollicis and the respiratory muscles. Pharmacodynamic modeling without plasma concentrations.
Although the respiratory muscles (the diaphragm and the laryngeal adductors) recover from paralysis more rapidly than does the adductor pollicis, patients can develop complete paralysis of the respiratory muscles, but not of the adductor pollicis, after bolus administration of vecuronium. The authors used a pharmacodynamic model not requiring muscle relaxant plasma concentrations to reconcile these findings. ⋯ Vecuronium concentrations peak earlier at the respiratory muscles than at the adductor pollicis, possibly the result of greater perfusion to these organs, leading to earlier onset of paralysis. The observation that bolus injection of vecuronium produces greater paralysis of the respiratory muscles than of the adductor pollicis, despite greater resistance of the respiratory muscles, can be explained by differential rates of equilibration between plasma and various muscles.
-
Mivacurium's rapid onset and short duration of action in children suggests that intramuscular administration might treat laryngospasm and facilitate tracheal intubation without producing prolonged paralysis. Accordingly, the authors measured the neuromuscular effects of intramuscular mivacurium in anesthetized infants and children. ⋯ Although ventilatory depression preceded twitch depression, both occurred later with intramuscular mivacurium than would be expected after intravenous mivacurium or intramuscular succinylcholine. The authors speculate that the onset of intramuscular mivacurium is too slow to treat laryngospasm or to facilitate routine tracheal intubation in infants or children, despite administration of large doses.
-
There are no clinical data regarding the ratios and concentrations in which morphine and bupivacaine should be combined, when given intrathecally, to improve analgesia while decreasing adverse effects. This study was undertaken to test the clinical efficacy of a constant infusion of 0.5 mg/ml morphine plus 4.75 mg/ml bupivacaine (morphine: bupivacaine approximately 1:10), given through open intrathecal catheters. ⋯ A constant intrathecal infusion with a morphine:bupivacaine ratio of approximately 1:10 and concentrations of morphine of 0.5 mg/ml and bupivacaine of 4.75 mg/ml may significantly improve the relief of refractory cancer pain with a certain risk of adverse effects (which should be balanced against pain by the patient) from the relatively high intrathecal bupivacaine doses and concentration.
-
The hemodynamic effects of isoflurane have been studied extensively. However, most data are obtained from volunteers or patients in the absence of surgical stimulation. The hemodynamic responses to various stimulation patterns of different intensity have not been evaluated. ⋯ Isoflurane used as a sole agent is unable to suppress hemodynamic reactions (blood pressure and heart rate) to painful stimuli. A "normal" blood pressure following stimulation can be achieved only if prestimulation blood pressure is depressed to levels that may be clinically unacceptable. The lack of motor response is not an accurate predictor of the ability of an agent to depress hemodynamic reaction.
-
Opioids are thought to have equal analgesic effects when equivalent doses are used. However, sufentanil may achieve maximum effect while occupying fewer spinal opioid receptors (higher intrinsic efficacy). Therefore, sufentanil may be more effective than morphine when administered intraspinally in opioid-tolerant patients. ⋯ These results suggest that sufentanil can be used successfully in opioid-tolerant patients who do not experience adequate pain control in the early postoperative period despite a large dose of epidural morphine. Moreover, sufentanil should be considered an effective alternative therapy for postoperative pain control in chronic opioid users using high doses of oral opioids before surgical intervention.