Anesthesiology Pharmacokinetic aspects of epidural morphine analgesia

latency changes could be reversed by the kappa-specific antagonist M, 2256 (20 Er_g/kg), but not by the classic opiate antagonist naloxone (20 pg/kg). The authors suggest that kappa receptor sites distinct from those interacting with common opioids (mu) are responsible for the observed changes associated with bremazocine. Pharmacokinetic aspects of epidural morphine analgesia. - G. Nordberg, T. Hedner, T. Mellstrand and B. Dahlstrom, Anesthesiology, 58 (1983) 545-551. Patients undergoing thoracotomy were given 2, 4, or 6 mg morphine epidurally at T12-Ll or Ll-L2 for postoperative analgesia in a double-blind, randomized study. Mean duration of anaJgesia (& S.E.M.) was respectively 514 & 118 min fn = 7). 778 + 207 min (n = 7) and 938 f 155 min (n = 6). The peak concentrations of morphine in plasma ranged from 19 to 34 ng/ml and were reached within 15 min. The morphine concentrations in the CSF were 45-250 times higher than in the plasma but the elimination half-life of morphine in the cerebrospinal fluid (CSF) was similar to that in plasma (173 + 24, 200 _t 60 and 213 i 57 min for the respective dosage groups). Nearly half the patients required catheterization of the bladder but itching and delayed respiratory depression were not encountered. The authors conclude that epidural morphine administration results in a dose-dependent duration of analgesia. For safety purposes, one may use the lumbar approach to the epidural space even for thoracic pain without reducing the analgesic efficacy of epidural morphine.

NEUROLOGY The psychophysiological etiology of muscle contraction headache. - S.N. Haynes, J. Cuevas and L.R. Gannon, Headache, 22 (1982) 122-132. This paper is a review of the laboratory studies on the vascular factors and muscle tension factors and on the psychophysiological aetiology of muscle tension headache. Synaptic complexes formed by functionally defined primary afferent units with fine myelinat~ fibres. - M. Rethelyi, A.R. Light and E.R. Persl, J. camp. Neurol., 207 (1982) 381-393. This paper not only contains new contributions but reviews the correlation between histological type and function of receptors and primary afferent fibres. The original contributions concern the high-threshold mechanoreceptors, which are activated by strong or noxious mechanical stimulation of the skin, and the D-hair fibres, activated by very light displacement of body hair or skin, in cats and monkeys. Effects of sympathetic nerve stimulation on in&a-oral mechanoreceptor activity in the cat. - R.M. Cash and R.W.A. Linden, J. Physiol. (Lond.), 329 (1982) 451-463. Stimulation of the cervical sympathetic nerve in the cat affected half of the periodontal mechanoreceptors examined: when the receptors were showing spontaneous activity, this was stopped; the discharge frequency to mechanical stimulation