Anesthesiology
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Certain opioids release histamine from cutaneous mast cells to produce local wheal and flare responses and adverse hemodynamic effects. In vivo responses to opioids suggest that cutaneous responses result from the interaction of opioids with opioid receptors on human mast cells. There are no data evaluating or comparing the opioids currently used in anesthesia. ⋯ Electron micrographs of biopsies from fentanyl-induced wheals demonstrated normal mast cell architecture with no evidence of mast cell degranulation. Opioid effects on wheal and flare responses and mast cell degranulation appear independent of opioid analgesic potency. Opioids produce cutaneous vascular responses dependent on both histamine release from mast cells and direct effects on the vasculature.(ABSTRACT TRUNCATED AT 250 WORDS)
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Cerebral blood flow (CBF) responsiveness to alterations in arterial CO2 tensions (PaCO2) during 1.4% and 2.8% isoflurane anesthesia was assessed. Dogs were initially anesthetized with thiopental (12 mg/kg, iv bolus), their tracheae intubated, after which anesthesia was maintained with 1.4% isoflurane. In eight animals three levels of PaCO2 (25, 40, and 60 mmHg) were studied during 1.4% and 2.8% isoflurane. ⋯ In a second group of animals (n = 8), the effects of changes in CPP during hypercapnia with 1.4% and 2.8% isoflurane were assessed. Increasing CPP approximately 25 mmHg with both 1.4% and 2.8% isoflurane increased CBF but did not change CVR from control. With 1.4% isoflurane, the cerebral vasculature constricts with hypocapnia and dilates with hypercapnia, whereas with 2.8% isoflurane, vasoconstriction to hypocapnia is retained but vasodilation to hypercapnia is absent.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study Clinical Trial Controlled Clinical Trial
Intrathecal methadone and morphine for postoperative analgesia: a comparison of the efficacy, duration, and side effects.
A double-blind study of patients selected at random compared the analgesic and adverse effects of intrathecal methadone (1 mg) with those of intrathecal morphine (0.5 and 1 mg). The study was conducted on 30 patients who underwent major orthopedic or urologic surgery. The intrathecal opioid was administered at the end of surgery, and assessments began 1 h thereafter and continued for 20 h. ⋯ Nausea and vomiting were common to all groups. Intrathecal morphine (0.5 and 1 mg) provides superior postoperative analgesia to 1 mg methadone. Various explanations for the observed differences between the drugs are discussed, including the possibility that the dose of methadone used in the subarachnoid space was inadequate and that a larger dose might have produced an effect equal to that of morphine.
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Randomized Controlled Trial Comparative Study Clinical Trial
Needle bevel direction and headache after inadvertent dural puncture.
To study the effect of needle bevel direction on the incidence and severity of headache following inadvertent dural puncture occurring during the identification of the epidural space, the authors randomly assigned obstetric anesthesia residents to identify epidural space with the bevel of the epidural needle oriented either parallel or perpendicular to the longitudinal dural fibers. If dural puncture occurred, an observer unaware of the needle bevel direction, daily assessed the presence and severity of any subsequent headache. ⋯ Similarly, we administered a therapeutic blood patch to ten of 20 women in the perpendicular group but to only four of 21 in the parallel group (P less than 0.05). Thus, identifying the epidural space with the needle bevel oriented parallel to the longitudinal dural fibers limits the size of the subsequent dural tear and, therefore, lowers the incidence of headache should dural perforation occur.