Opioid-induced hyperalgesia : a pathological or physiological phenomenon ? Study development of an animal model of acute hyperalgesia to sufentanil under general anesthesia

Opioids are the most frequently used drugs to relieve moderate to severe pain. In addition to their analgesic effects, opioids induce dependence and tolerance. These phenomena are well-known in the setting of chronic pain therapy. Nevertheless, opioids can unexpectedly enhance pain and extend pain states even after a single administration. This condition, termed hyperalgesia, is defined as an increased sensitivity to noxious stimuli.Because, in daily clinical practice, opioids are frequently used for balanced anesthesia and postoperative pain management, the experimentally proved hyperalgesic effect of opioids leads clinicians and researchers to question how drugs recognized to alleviate pain, may have the opposite effect. In other words, in anesthetic setting, do the opioids enhance pain or promote postsurgical pain? The present work will focus on the intriguing concept of opioid-induced hyperalgesia (OIH). Its originality is the development of a new animal model where the paradoxical effect of opioids is expressed under general anesthesia, mimicking clinical practice. From the investigations, it appears that OIH may occur after the administration of a very low dose of sufentanil under volatile anesthesia. The mechanisms underlying this paradoxical effect in anesthetized animals are similar to those implicated in OIH after high doses of opioids in awake animals. Moreover, this pro-nociceptive effect disappears in co-existing chronic pain presuming common underlying mechanisms with injury-induced hyperalgesia. This work might be considered as a supplemental investigation of the paradoxical phenomenon of OIH in the perioperative context. Anesthesia is more than simply a loss of consciousness. Anesthetic management may have an impact on postoperative pain and perioperative management should be individualized to each patient.(SBIM 3) -- UCL, 201

Multimodal Brain Monitoring in Congenital Cardiac Surgery: The Importanceof Processed Electroencephalogram Monitor, NeuroSENSE, in Addition to Cerebral Near-Infrared Spectroscopy

THERE IS increasing concern about the neurologic outcome of children undergoing congenital cardiac surgery. In past years, numerous small studies have shown the importance of cerebral near-infrared spectroscopy (NIRS) in managing neonates and children during cardiac surgery. Few reports have been published questioning the validity of cerebral NIRS data. It can be speculated that negative results do not reach publication easily. Therefore, results of studies evaluating cerebral NIRS in congenital cardiac surgery are prone to publication bias, which certainly is not unique to this technology

Anesthésie d'une enfant presentant une dysplasie anhydrotique ectodermique associée à une myopathie multiminicore.

PURPOSE: To report the perioperative management of anesthesia and analgesia in a child presenting with the association of multiminicore myopathy (MMM) and anhydrotic ectodermic dysplasia (AED). CLINICAL FEATURES: An eight-year-old girl was admitted for elective orthopedic surgery of the lower limbs. AED is a congenital dermatosis characterized by the absence of sweating and subsequent problems with thermoregulation; in addition, maxillary hypoplasia and abnormal teeth can render intubation difficult. MMM is a rare congenital myopathy characterized by proximal muscle weakness, stable in time or with a slow and progressive evolution. It can involve respiratory muscles and be associated with severe cardiomyopathy. Moreover, MMM shares some characteristics with Central Core Disease which is known to be associated with malignant hyperthermia. Since depolarizing muscle relaxants and halogenated agents could not be used, a combined propofol-based intravenous anesthesia with lumbar epidural analgesia was chosen. This combination provided stable anesthesia, smooth recovery and excellent analgesia during and after the operation, without complications. Temperature was monitored closely during surgery and in the postoperative period. CONCLUSIONS: The association of MMM and AED requires rapid distinction between hyperthermia secondary to anhydrosis and malignant hyperthermia. The management should provide a "trigger-free" anesthetic and optimal postoperative analgesia without sedation. If appropriate for the surgical procedure, a combination of general with regional anesthesia is particularly attractive in achieving these objectives

Two cases of isolated unilateral paralysis of hypoglossal nerve after uncomplicated orotracheal intubation.

We report two cases of postoperative unilateral hypoglossal nerve palsy following uncomplicated orotracheal intubation for plastic surgery. Both patients underwent a long procedure and were installed in a non physiological position. These two factors might have played an important role in the mechanism of nerve damage. Furthermore, other etiologies of neurological injury like a difficult airway or anatomical anomalies were not present. The aim of these two case reports is to sensitize the anesthetists to hypoglossal nerve palsy and to highlight a potential clinical problem of positioning during plastic surgery

Spinal alpha(2)-adrenoceptors are involved in the MACbar-sparing effect of systemic clonidine in rats.

We evaluated the central or spinal mechanism involved in the MACbar-sparing effect of systemic clonidine by using intrathecal alpha-adrenergic antagonist administration. The minimum alveolar concentration of sevoflurane that blocks cardiovascular response to a noxious stimulus (MACbar(sevo)) was determined in rats after treatment with IV saline, IV clonidine 10 micro g/kg, intrathecal (IT) or IV phentolamine 50 micro g, IT or IV yohimbine 200 micro g, IT or IV prazosin 30 micro g, or the combination of IV clonidine and the different IT or IV alpha-adrenergic antagonists. In the studied model, the MACbar(sevo) of saline-treated controls was 2.10 +/- 0.8. After clonidine administration, it decreased to 1.07 +/- 0.4. The IT administration of phentolamine and yohimbine did not modify the MACbar(sevo) of naïve rats, whereas in IV clonidine-treated animals, it totally suppressed the MAC-sparing effect of this drug (phentolamine) or even significantly increased (yohimbine) the MACbar(sevo) (2.78 +/- 1) when compared with controls (P < 0.05). IT prazosin alone significantly reduced the MACbar(sevo) (0.35 +/- 0.3; P< 0.05) and suppressed any hemodynamic reaction when combined with IV clonidine. The IV administration of the different alpha-adrenergic antagonists had no significant effect on the MACbar(sevo) of controls or IV clonidine-treated animals. These results argue for a spinal mechanism of action involved in the MACbar-sparing effect of systemic clonidine. Moreover, the spinally administered alpha-antagonists displayed different effects in rats under sevoflurane anesthesia than those reported in awake animals. IMPLICATIONS: Using intrathecal alpha-adrenergic antagonist administration, we demonstrated that a spinal mechanism is involved in the MACbar-sparing effect of systemic clonidine in rats

Electroencephalogram Suppression Despite Extremely Low-Dose Anesthetic During Cardiac Surgery: A Case Report.

A prominent feature of electroencephalogram (EEG) under general anesthesia is anteriorization of α waves. We report the case of a 63-year-old man anesthetized for coronary artery bypass grafting in whom the NeuroSENSE-processed EEG monitor recorded only δ waves in the absence of α frequencies, along with high EEG suppression despite extremely low doses of anesthetics during the whole procedure. The patient fully recovered from anesthesia 2 hours after the procedure and showed neither awareness nor neurological complications. This atypical EEG pattern under low concentration of anesthetics may be an intraoperative marker of a specific brain phenotype