Intraventricular dexmedetomidine decreases cerebral blood flow during normoxia and hypoxia in dogs

Uni-hemispheric hyperperfusion in the early postictal state: case report

Background

In the emergency setting of acute ischemic stroke, seizures have been reported in up to 4% of patients. In the absence of arterial occlusion, seizures may also cause abnormalities in CT perfusion in 78% of cases when the time window from onset to imaging is short. Both hyperperfusion and hypoperfusion in the postictal state have been described. Also, though rarely reported, postictal perfusion changes can be uni-hemispheric. In these cases, perfusion maps should be analyzed thoroughly, since perfusion reconstruction software relies heavily on a “normal” contralateral perfusion status.

Case presentation

A 39-year-old man was found on the ground with a minor head injury. On admission, his reactions were generally slow, but there were no other neurological symptoms, and blood pressure was low. The patient had a history of primary generalized epilepsy and admitted to dropping off his anti-epileptic medication. He was transferred to the radiological department for imaging but shortly before began to experience generalized onset tonic-clonic seizures which were brought under control by intravenous therapy with 10 mg diazepam. After approximately 15 min, a multimodal CT scan was performed, revealing marked changes in the perfusion of the brain hemispheres and posterior fossa, with sharp delimitation at the midline. Blood gas analysis was congruent with respiratory acidosis. Clinically, the patient remained awake without developing any new symptoms. He gradually recovered over the following 3 h and, against our medical recommendation, discharged himself from the hospital.

Conclusions

To the authors’ knowledge, this is the first report of an early postictal state describing sharply delimited uni-hemispheric hyperperfusion and hemispheric alteration of the cerebellum with an equally split rhombencephalon. Surprisingly, these changes were not associated with any focal neurological signs. To prevent misdiagnosis of perfusion alterations in seizures, radiologists and neurologists should be aware of the limitations of CT perfusion maps and software reconstructions. Novel use of CT perfusion reconstruction using peak enhancement helped in identifying the cerebral pathology.

Effects of anesthesia on cerebral blood flow, metabolism, and neuroprotection

Administration of anesthetic agents fundamentally shifts the responsibility for maintenance of homeostasis from the patient and their intrinsic physiological regulatory mechanisms to the anesthesiologist. Continuous delivery of oxygen and nutrients to the brain is necessary to prevent irreversible injury and arises from a complex series of regulatory mechanisms that ensure uninterrupted cerebral blood flow. Our understanding of these regulatory mechanisms and the effects of anesthetics on them has been driven by the tireless work of pioneers in the field. It is of paramount importance that the anesthesiologist shares this understanding. Herein, we will review the physiological determinants of cerebral blood flow and how delivery of anesthesia impacts these processes.

Dexmedetomidine for the treatment of postanesthesia shivering in children

BACKGROUND

Shivering is a common postanesthesia adverse event with multiple etiologies and multiple suggested prophylactic and abortive treatment regimens. Dexmedetomidine, a centrally acting alpha(2)-adrenergic agonist, has been used as a sedative agent and is known to reduce the shivering threshold. We hypothesized that children with postanesthesia shivering would reduce shivering behavior following a single bolus dose of dexmedetomidine.

METHODS

Dexmedetomidine was administered in a prospective, open-label fashion. The anesthesia management was uniform consisting of maintenance inhaled anesthesia (sevoflurane) and the intraoperative administration of fentanyl (1-2 microg.kg(-1)) plus a regional anesthetic technique (either a neuraxial or peripheral block) for postoperative analgesia. Criteria for treatment included: (i) shivering, (ii) successful extubation, and (iii) no other complaint/indication of pain. All children who met the criteria were treated with a single intravenous bolus dose of dexmedetomidine (0.5 microg.kg(-1)) over 3-5 min. Following the completion of drug administration, shivering activity was recorded every minute (up to 10 min) with any adverse effects or complaints. The efficacy of shivering reduction at 5 min in this cohort is compared with previous reports from the literature of the efficacy of clonidine and meperidine.

RESULTS

Twenty-four children ranging in age from 7 to 16 years (11.5 +/- 2.5 years) were treated. All children had a cessation of shivering behavior within 5 min following the completion of dexmedetomidine administration. The onset of effect was 3.5 +/- 0.9 min. No adverse effects were observed. No shivering behavior recurred.

CONCLUSIONS

This study demonstrates the efficacy of dexmedetomidine in the treatment of postanesthesia shivering.