A rat model of unilateral hindpaw burn injury: slowly developing rightwards shift of the morphine dose-response curve

Management of pain after burn injury is an unresolved clinical issue. In a rat model of hindpaw burn injury, we examined the effects of systemic morphine on nociceptive behaviors following injury. Injury was induced by immersing the dorsal part of one hindpaw into a hot water bath (85 degrees C) for 4, 7, or 12 s under pentobarbital anesthesia. Mechanical allodynia to von Frey filament stimulation and thermal hyperalgesia to radiant heat were assessed. Burn injury induced by the 12-s (but not 4-, or 7-s) hot water immersion resulted in reliable and lasting mechanical allodynia and thermal hyperalgesia evident by day 1. In addition, there was an upregulation of protein kinase Cgamma and a progressive downregulation of mu-opioid receptors within the spinal cord dorsal horn ipsilateral to injury as revealed by immunohistochemistry and Western blot. In both injured and sham rats, the anti-nociceptive effects of subcutaneous morphine were examined on post-injury days 7 and 14. While the morphine AD50 dose was comparable on day 7 between burn (1.61 mg/kg) and control (1.7 mg/kg) rats, the morphine dose-response curve was shifted to the right in burn-injured rats (4.6 mg/kg) on post-injury day 14 as compared with both the injured rats on post-injury day 7 and sham rats on day 14 (1.72 mg/kg). These data indicate that hindpaw burn injury reliably produces persistent mechanical allodynia and thermal hyperalgesia and that the reduced efficacy of morphine anti-nociception in chronic burn injury may be in part due to a downregulation of spinal mu-opioid receptors.     

Massive postpartum haemorrhage after uterus-conserving surgery in placenta percreta: the danger of the partial placenta percreta

Placenta percreta is a rare but potentially life-threatening condition associated with high maternal mortality and morbidity rates, usually arising from severe obstetric haemorrhage. Due to rising caesarean section rates, an increase in the incidence of morbidly adherent placentas (accreta, increta and percreta) has been observed. Various treatment strategies have been employed in different centres, ranging from performing a caesarean hysterectomy at the time of delivery to leaving the placenta in situ , with or without adjuvant internal iliac and uterine arterial embolisation and/or methotrexate therapy. In the case of placenta percreta, irrespective of the treatment method employed, women are still at high risk of life-threatening haemorrhage and morbidity secondary to placental invasion beyond the confines of the uterine serosa into surrounding organs, most commonly the bladder. We describe an unusual case of a partially adherent placenta percreta in which partial separation of the normally implanted placenta led to torrential haemorrhage on the third postoperative day after the placenta was left in situ at the time of delivery. We therefore advise caution in following a conservative approach in the treatment of cases of placenta percreta in which the percreta feature is only partial and will discuss the merits and disadvantages of alternative options.     

Long-term effects of botulinum toxin on neuromuscular function

BACKGROUND: Recent reports indicate increased incidence of Clostridium botulinum infections, particularly among drug abusers and tissue allograft recipients. Botulinum toxin also has potential application in biochemical warfare. The neurotoxin-induced paralysis often requires mechanical ventilation with and without muscle relaxants. The authors investigated the long-term effects of botulinum toxin on muscle function, expression of nicotinic acetylcholine receptors (nAChRs), and their interaction with muscle relaxant, atracurium. METHODS: Rats (n=30) were injected with varying doses (0.625, 2.5, and 10 U) of botulinum toxin into the tibialis muscle. Control animals (n=9) received an equivalent volume of saline. At 128 days after injection, neuromuscular function, pharmacodynamics of atracurium, and nAChRs were evaluated. RESULTS: Nerve-evoked tensions, including tetanic tension and muscle mass, were decreased on the toxin-injected side in a dose-dependent manner relative to saline-injected controls as well as the contralateral side. Specific muscle tension and specific tetanic muscle tension (tensions/muscle mass) were not reduced. The ED10 of atracurium was reduced, the ED50 was unchanged, and the ED90 was increased in the highest (10-U) dose of toxin group. The atracurium plasma concentration to maintain a steady state 50% paralysis was significantly reduced in the 10-U toxin group. The nAChR concentrations in the tibialis muscle were significantly increased in a dose-dependent manner in all experimental groups. CONCLUSION: Botulinum toxin causes dose-dependent long-term neuromuscular changes. The loss of tension generating capacity is almost exclusively related to muscle atrophy, because the specific tension did not change. The decreased ED10, unaltered ED50, and increased ED90 to atracurium suggest its interactions with different isoforms of receptors having varying sensitivity to atracurium. The absence of fade, despite the persistent botulinum toxin-induced denervation (increased nAChRs), suggests that the up-regulated nAChRs may have compensated for the prejunctional effects of botulinum toxin.     

Cerebral venous sinus stenting for pseudotumor cerebri: A review

Pseudotumor cerebri is characterized by headaches, visual field changes, papilledema and an elevated cerebrospinal fluid opening pressure without evidence of an intracranial mass. In the setting of failed medical therapy, surgical options such as ventriculoperitoneal shunts and optic nerve sheath fenestrations are considered. Recently, venous sinus stenting has emerged as a new treatment option for patients with pseudotumor cerebri. We review the role of cerebral venous sinus stenting in the management of patients with medically refractory pseudotumor cerebri. Although long- term studies are needed in this field, the current reports indicate a favorable outcome for preventing vision loss and symptom control.     

Psychiatric issues in pain of burn injury

This paper presents psychiatric issues in the management of acute pain in burned children and adults. We discuss the importance of psychiatric assessment, neurobiologic and psychologic considerations, and methods of pain assessment. Pharmacologic and psychologic treatments of pain following burn injuries are presented. Other topics covered are managed care monitors, staff responses, and ethical issues.