Dexmedetomidine for deep brain stimulator placement in a child with primary generalized dystonia: case report and literature review.

Dexmedetomidine, which is a relatively selective alpha2-adrenoceptor agonist, is used for sedation and analgesia in intensive care unit patients, during awake craniotomies in pediatric and adult patients, and during magnetic resonance imaging, with minimal depression of respiratory function. The successful use of dexmedetomidine in a pediatric patient undergoing bilateral deep brain stimulator placement for the treatment of generalized dystonia, is presented.

Dosing of remifentanil to prevent movement during craniotomy in the absence of neuromuscular blockade.

BACKGROUND: In neuroanesthesia practice, muscle relaxants may at times need to be avoided to facilitate intraoperative motor pathway monitoring. Our study's objective was to determine the optimal dose of remifentanil required to prevent movement after neurosurgical stimulation. METHODS: After Institutional Review Board approval and written informed consent, 132 patients undergoing elective craniotomy randomly received one of 12 remifentanil dose regimens (0.10 to 0.21 microg/kg/min). Remifentanil was started before induction with propofol and succinylcholine. Anesthesia was maintained with isoflurane (0.6% end-tidal) in air/oxygen. During the study, movement was assessed on predetermined criteria by the anesthesiology, nursing, and neurosurgical teams. Heart rate and blood pressure were recorded every 5 minutes. We assessed the relationship between movement, hypotension, bradycardia, and dose using probit analysis and logistic regression. RESULTS: Sixty-five percent of the patients moved in response to surgical stimuli [95% confidence interval (CI): 49%-79%] at a remifentanil infusion rate of 0.10 microg/kg/min, and movement decreased to 21% (95% CI: 11-35) at 0.21 microg/kg/min. The probability of movement was 50% at an infusion rate (95% CI) of 0.13 (0.10 to 0.15) microg/kg/min remifentanil and decreased to 25% at an infusion rate of 0.19 (0.17 to 0.29) microg/kg/min. The probability of hypotension and bradycardia was 50% at 0.13 (0.10 to 0.15) microg/kg/min and 0.17 (0.15 to 0.21) microg/kg/min, respectively. CONCLUSIONS: Higher doses of remifentanil lessen the risk of movement in the absence of muscle relaxants with surgical stimulation for elective craniotomy. Hypotension and bradycardia were common at higher doses. Even at the maximum dose (0.21 mcg/kg/min) there was a 20% chance of movement. Adjunctive therapy is needed to ablate movement reliably, and to counteract the hypotensive effect of remifentanil. These findings may be helpful for clinicians administering remifentanil and isoflurane during procedures, where muscle relaxants may not be desirable.

Perioperative complications of blood brain barrier disruption under general anesthesia: a retrospective review.

Blood brain barrier disruption enhances drug delivery in primary central nervous system lymphoma. In this study, we report adverse events that were encountered intraoperatively and in the postoperative period in these patients. A retrospective analysis of 17 patients documenting demographic data, preprocedure medical history, intraoperative, and postoperative anesthetic complications was conducted between January 2002 and December 2004. Seventeen patients underwent 210 treatments under general anesthesia with a mean of 12.4+/-7.2 treatments per patient. Focal seizures occurred in 13% of patients. Generalized motor seizures occurred in 4 treatment sessions in 2 different patients. The incidence of seizures was significantly higher when the internal carotid artery was used for injection, as opposed to the vertebral artery (20.8% and 6.02%, respectively, P=0.0034). Tachycardia associated with ST segment depression occurred 9 times (4.3%) in 3 patients. One patient had significant ST segment elevation (more than 1.5 mm). Transient cerebral vasospasm after methotrexate injection occurred in 9% of patients. Postoperative nausea and vomiting were observed in 11.9% of patients. After emergence, lethargy and obtundation occurred in 7.6% of the cases. The incidence of postoperative headache and reversible motor deficits was 6% and 3.8%, respectively. Our review highlights the problems that were encountered during blood brain barrier disruption under anesthesia and in the postoperative period. Further prospective studies are required for comprehensive evaluation of intraprocedure and postprocedure complications that will allow development of an optimal anesthetic plan and will improve patient outcome by preventing potential complications.

Intrathecal opioids for control of chronic low back pain during deep brain stimulation procedures.

Patients with chronic low back pain may not be able to endure the supine position required by the lengthy deep brain stimulation procedure. Many neurophysiologists severely restrict the use of opioids and sedative drugs during deep brain stimulation procedures due to the concern for depression of cellular firing frequencies used to map the brain for placement of the stimulator leads. We present two cases in which spinal opioids were used to achieve prolonged pain relief in patients with chronic back pain, without altering cellular firing critical for brain mapping.

Anesthesia for minimally invasive cranial and spinal surgery.

The field of minimally invasive neurosurgery has evolved rapidly in its indications and applications over the last few years. New, less invasive techniques with low morbidity and virtually no mortality are replacing conventional neurosurgical procedures. Providing anesthesia for these procedures differs in many ways from conventional neurosurgical operations. Anesthesiologists are faced with the perioperative requirements and risks of newly developed procedures. This review calls attention to the anesthetic issues in various minimally invasive neurosurgical procedures for cranial and spinal indications. Among the procedures specifically discussed are endoscopic third ventriculostomy, endoscopic transsphenoidal hypophysectomy, endoscopic strip craniectomy, deep brain stimulation, video-assisted thorascopic surgery, vertebroplasty and kyphoplasty, cervical discectomy and foraminectomy, and laparoscopically assisted lumbar spine surgery.

Dexmedetomidine and awake fiberoptic intubation for possible cervical spine myelopathy: a clinical series.

For many anesthesiologists, awake fiberoptic endotracheal intubation (AFOBI) is the preferred method of intubation when treating patients with symptoms or signs of cervical spinal cord compression. The advantage of this method is to minimize cervical spine movements that could contribute to neurologic impairment. In patients who are anxious or poorly cooperative, adequate sedation in addition to topicalization of the airway may be key to minimize patient discomfort and assist in successful intubation, but imposes the risk of respiratory depression. Dexmedetomidine has the advantage of producing sedation without a significant decrease in respiratory drive. We are now reporting our experience of a series of AFOBI using dexmedetomidine for sedation. A retrospective chart review was conducted on the anesthetic records of patients, who had undergone an awake fiberoptic endotracheal intubation (AFOBI) using dexmedetomidine for sedation. These were patients in whom AFOBI was indicated because of signs or symptoms of cervical spinal cord compression. Dexmedetomidine provided adequate sedation. We did not encounter any loss of airway or airway obstruction during the intubation. The patients had excellent cooperation for post-intubation neurologic examination. Thirteen patients developed transient hypotension after induction of general anesthesia that was managed with boluses of phenylephrine or ephedrine.

Effects of anesthetic agents and physiologic changes on intraoperative motor evoked potentials.

Motor evoked potentials (MEPs) have shown promise as a valuable tool for monitoring intraoperative motor tract function and reducing postoperative plegia. MEP monitoring has been reported to contribute to deficit prevention during resection of tumors adjacent to motor structures in the cerebral cortex and spine, and in detecting spinal ischemia during thoracic aortic reconstruction. Many commonly used anesthetic agents have long been known to depress MEP responses and reduce MEP specificity for motor injury detection. Although new stimulation techniques have broadened the spectrum of anesthetics that can be used during MEP monitoring, certain agents continue to have dose-dependent effects on MEP reliability. Understanding the effects of anesthetic agents and physiologic alterations on MEPs is imperative to increasing the acceptance and application of this technique in the prevention of intraoperative motor tract injury. This review is intended as an overview of the effects of anesthetics and physiology on the reproducibility of intraoperative myogenic MEP responses, rather than an analysis of the sensitivity and specificity of this monitoring method in the prevention of motor injury.