Alex Bekker

Awake craniotomy with dexmedetomidine in pediatric patients.

&NA; We present our experience with the use of dexmedetomidine, an &agr;2 agonist, in two children undergoing awake craniotomy. General anesthesia with the laryngeal mask airway was used for parts of the procedure not requiring patient cooperation to reduce the duration of wakefulness and abolish the discomfort of surgical stimulation. Dexmedetomidine was used as a primary anesthetic for brain mapping of the cortical speech area. The asleep‐awake‐sleep technique provided adequate sedation and analgesia throughout the surgery and allowed the patient to complete the necessary neuropsychological tests. To our knowledge, ours is the first description of the use of dexmedetomidine in pediatric neurosurgery.

Dexmedetomidine for awake carotid endarterectomy: efficacy, hemodynamic profile, and side effects.

Abstract: A randomized, double-masked, placebo-controlled study was designed to compare dexmedetomidine as a primary sedative agent with a commonly used drug combination in patients undergoing awake carotid endarterectomy (CEA). Sixty-six patients undergoing CEA (ASA II–IV) were randomly assigned to receive either dexmedetomidine (total dose of 97.5 ± 54.7 mcg) or normal saline (control). Supplemental doses of midazolam, fentanyl, and/or propofol were administered as deemed necessary by the anesthesiologist. An observer blinded to the study drug assessed sedation level (Observer’s Assessment of Alertness-Sedation [OAA/S] scale). The primary outcomes were defined as the number of patients with an OAA/S score of 4 intraoperatively and an OAA/S score of 5 postoperatively. The authors also compared cardiorespiratory parameters, intra- and postoperative side effects, and complications. Chi-square tests were used to analyze the primary endpoints. All secondary parameters were analyzed using the Wilcoxon rank sum test. Three patients in the dexmedetomidine group (10%) had an OAA/S score of 4 at all four time points assessed intraoperatively, while no patient in the control group had a score of 4 at all the time points considered. Thirteen patients in the dexmedetomidine group had a score of 4 at three or more time points (42%) compared with six patients (19%) in the control group. Four patients in the control group (13%) and one patient in the dexmedetomidine group (3%) did not achieve a score of 4 at any of the four critical intraoperative time points (χ2 for association = 9.9, P < 0.05; χ2 for a trend = 8.6, P < 0.004, with the trend favoring dexmedetomidine). More patients in the control group required treatment with metoprolol (26% vs. 6%, P = 0.04) and labetalol (48% vs/ 6%, P < 0.01). Plasma levels of norepinephrine were significantly lower in the dexmedetomidine group during and after surgery compared with the control group. Six patients (19%) in the dexmedetomidine group required intra-arterial shunts, while only two patients (6%) required shunts in the control group (P = 0.16). These data show that the use of dexmedetomidine in patients undergoing awake CEA resulted in fewer fluctuations from the desired sedation level. Patients receiving dexmedetomidine required less antihypertensive therapy compared with the midazolam/fentanyl/propofol combination. The effect of dexmedetomidine on cerebrovascular circulation in the study population needs further investigation.

The Effect of Dexmedetomidine on Perioperative Hemodynamics in Patients Undergoing Craniotomy

BACKGROUND: The perioperative course of patients undergoing intracranial surgery is frequently complicated by hypertensive episodes. Dexmedetomidine (DEX), an &agr;-2 adrenoreceptor agonist, is gaining popularity in neuroanesthesia, because its sympatholytic and antinociceptive properties may improve hemodynamic stability at critical moments of surgery. We designed this study to assess the efficacy of DEX in controlling hypertensive responses in patients undergoing intracranial surgery. METHODS: Patients scheduled for elective craniotomy were randomly assigned to receive either sevoflurane–opioid or sevoflurane–opioid–DEX anesthesia. Bispectral index was used to maintain a similar level of hypnosis in both groups (40–50). Opioids, sevoflurane, and vasoactive medications were titrated in a routine manner, at the discretion of the blinded anesthesiologist managing the case, to maintain systolic blood pressure (SBP) targeted within 90–130 mm Hg and heart rate (HR) between 50 and 90 bpm. Hemodynamic variables were continuously recorded and stored on a computer for analysis. Efficacy of the anesthetic technique in controlling SBP or HR is inversely proportional to the area under the curve (AUC) outside the targeted range. Areas under the curves above and below targeted ranges for SBP-time (AUCsbp mm Hg * min/h) and HR-time (bpm * min/h) were compared. Coefficient of variation was used to assess hemodynamic stability. RESULTS: Seventy-two patients were recruited for the study. Computerized records of 56 patients only were analyzed because of technical problems with data collection in 14 cases. AUCsbp for above the targeted range was significantly lower for patients in the DEX group (P = 0.044). The coefficient of variation for SBP or HR did not differ between groups. A significantly smaller proportion of patients in the DEX group required treatment with antihypertensive medications (12 of 28, 42% vs 24 of 28, 86%, P = 0.0008). The DEX group required fewer opioids in the intraoperative period, but there were no differences in the use of sevoflurane. In the postanesthesia care unit, patients in the DEX group had fewer hypertensive episodes (1.25 ± 1.55 vs 2.50 ± 2.00, P = 0.0114) and were discharged earlier (91 ± 17 vs 130 ± 27 min, P < 0.0001). There were no differences in the requirement for postoperative opioids or antiemetics. CONCLUSIONS: By using indices, which assess a global hemodynamic stability of the anesthetic, we determined that intraoperative DEX infusion was effective for blunting the increases in SBP perioperatively. The use of DEX did not increase the incidence of hypotension or bradycardia, common side effects of the drug.

Evaluation of Aromatherapy in Treating Postoperative Pain: Pilot Study

Abstract:u2003 This study compared the analgesic efficacy of postoperative lavender oil aromatherapy in 50 patients undergoing breast biopsy surgery. Twenty‐five patients received supplemental oxygen through a face mask with two drops of 2% lavender oil postoperatively. The remainder of the patients received supplemental oxygen through a face mask with no lavender oil. Outcome variables included pain scores (a numeric rating scale from 0 to 10) at 5, 30, and 60u2003minutes postoperatively, narcotic requirements in the postanesthesia care unit (PACU), patient satisfaction with pain control, as well as time to discharge from the PACU. There were no significant differences in narcotic requirements and recovery room discharge times between the two groups. Postoperative lavender oil aromatherapy did not significantly affect pain scores. However, patients in the lavender group reported a higher satisfaction rate with pain control than patients in the control group (Pu2003=u20030.0001).

The effect of intraoperative infusion of dexmedetomidine on the quality of recovery after major spinal surgery.

Background: Surgery induces a variety of metabolic, endocrine, and immune changes collectively known as the “stress response,” which may often lead to prolonged postoperative convalescence. Anesthetic management may modulate this physiological response, thus affecting the postoperative course. We hypothesized that the intraoperative administration of dexmedetomidine (DEX), a sympatholytic agent, would reduce the stress response and improve the quality of recovery in patients undergoing major surgery. Methods: We conducted a prospective randomized double-blinded study of 54 patients undergoing multilevel spinal fusion. Anesthesia was maintained using either propofol/fentanyl/dexmedetomidine (PFD) or propofol/fentanyl/placebo-saline (PFS). The quality of recovery (a primary endpoint) was assessed using a 40-item quality of recovery questionnaire and a 9-question Fatigue Severity Scores. The tests were carried out preoperatively on postoperative days (POD) 1, 2, 3, and 30. Blood samples were collected at baseline, in the postanesthesia care unit, and at POD 1 and were analyzed for levels of cortisol, C-reactive proteins (CRP), and cytokines interleukin (IL)-1&agr;, IL-1&bgr;, IL-1ra, IL-2, IL-6, IL-8, IL-10, and tumor necrosis factor-&agr;. Data were analyzed using SPSS software (version 18) using a multivariate and mixed model approach to test for the effect of surgery and drug group. Pairwise comparisons were assessed by means of the t test or rank tests after correcting for multiple comparisons. Results: The global 40-item quality of recovery questionnaire scores showed a significant effect of time (F4,114=22.63, P<0.001) and drug (F1,51=4.368, P=0.042), with average scores decreasing to lower values on POD 1 (163.63±2.47) and POD 2 (170.94±2.38) compared with baseline (180.56±1.588, mean±SE, 2-tailed t tests, P<0.001). By POD 3, scores were significantly lower (−13.74 point difference, P=0.005) in the PFS group (169.3±3.87) than in the PFD group (183.04±2.76). All patients reported significantly higher levels of fatigue postoperatively, but intergroup difference in Fatigue Severity Scores was detected on POD 3 only, with scores in the PFS group higher than in the PFD group (50.0±4.0 vs. 36.3±4.9, P=0.035). In both groups, plasma cortisol levels were highest in the postanesthesia care unit, whereas CRP levels were elevated on POD 1. DEX significantly reduced the levels of cortisol, but not those of CRP. Levels of cytokines IL-6, IL-8, and IL-10 were significantly higher immediately after surgery and at POD 1. Plasma levels of other cytokines were not affected by surgery. DEX delayed postoperative rise in IL-10 but not in IL-6 or IL-8. Conclusions: DEX infusion during multilevel spinal fusions moderately improved the quality of recovery and possibly reduced fatigue in the early postoperative period. Moreover, it reduced plasma levels of cortisol and IL-10 in comparison with the control group. Our sample size was not sufficient to detect differences either in the incidence of complications or in clinically relevant outcomes.

Surgery and Brain Atrophy In Cognitively Normal Elderly Subjects and Subjects Diagnosed with Mild Cognitive Impairment

Background: Structural magnetic resonance imaging is used to longitudinally monitor the progression of Alzheimer disease from its presymptomatic to symptomatic phases. Using magnetic resonance imaging data from the Alzheimers Disease Neuroimaging Initiative, we tested the hypothesis that surgery would impact brain parameters associated with progression of dementia. Methods: Brain images from the neuroimaging initiative database were used to study normal volunteer subjects and patients with mild cognitive impairment for the age group 55 to 90 inclusive. We compared changes in regional brain anatomy for three visits that defined two intervisit intervals for a surgical cohort (n = 41) and a propensity matched nonsurgical control cohort (n = 123). The first interval for the surgical cohort contained the surgical date. Regional brain volumes were determined with Freesurfer and quantitatively described with J-image software (University of California at San Francisco, San Francisco, California). Statistical analysis used Repeated Measures ANCOVA (SPSS, v.18.0; Chicago, IL). Results: We found that surgical patients, during the first follow-up interval (5–9 months), but not subsequently, had increased rates of atrophy for cortical gray matter and hippocampus, and lateral ventricle enlargement, as compared with nonsurgical controls. A composite score of five cognitive tests during this interval showed reduced performance for surgical patients with mild cognitive impairment. Conclusions: Elderly subjects after surgery experienced an increased rate of brain atrophy during the initial evaluation interval, a time associated with enhanced risk for postoperative cognitive dysfunction. Although there was no difference in atrophy rate by diagnosis, subjects with mild cognitive impairment suffered greater subsequent cognitive effects.

Analysis of microvascular permeability to macromolecules by video-image digital processing

The dynamics of macromolecular transport across microvascular walls were studied in the hamster cheek pouch by intravital fluorescence microscopy. A graded series of fluorescein isothiocyanate-labeled dextrans (FITC-Dx) of 20,000-70,000 MW was used as macromolecular tracers. The time-dependent extravasation of FITC-Dxs was videotaped for about 2.5 hr to allow for tracer equilibration in the interstitial space. Permeation of macromolecules from individual microvessels was quantified by digital video-image processing. Histograms of the light intensity distributions for selected fields at various times were measured and used to construct integral optical density-time profiles of the extravasated fluorochromes for particular leaky sites. A nonlinear regression algorithm was employed to determine the effective microvascular permeability (P) for the macromolecules studied using a one-dimensional two-compartmental diffusion model and a step change in macromolecular concentration at the boundary. The calculated Ps (X 10(-8) cm/sec) were 47.8 +/- 8.7 for FITC-Dx 20; 31.7 +/- 5.9 for FITC-Dx 40, and 17.5 +/- 4.1 for FITC-Dx 70. Our values are comparable to those obtained by whole organ techniques. The observed differences can be explained by explicit consideration of interstitial resistance in the calculations.

Noncoding RNAs New Players in Chronic Pain

Chronic pain, a common clinical symptom, is often treated inadequately or ineffectively in part due to the incomplete understanding of molecular mechanisms that initiate and maintain this disorder. Newly identified noncoding RNAs govern gene expression. Recent studies have shown that peripheral noxious stimuli drive expressional changes in noncoding RNAs and that these changes are associated with pain hypersensitivity under chronic pain conditions. This review first presents current evidence for the peripheral inflammation/nerve injury–induced change in the expression of two types of noncoding RNAs, microRNAs, and Kcna2 antisense RNA, in pain-related regions, particularly in the dorsal root ganglion. The authors then discuss how peripheral noxious stimuli induce such changes. The authors finally explore potential mechanisms of how expressional changes in dorsal root ganglion microRNAs and Kcna2 antisense RNA contribute to the development and maintenance of chronic pain. An understanding of these mechanisms may propose novel therapeutic strategies for preventing and/or treating chronic pain.

Epigenetic regulation of chronic pain

Chronic pain arising from peripheral inflammation and tissue or nerve injury is a common clinical symptom. Although intensive research on the neurobiological mechanisms of chronic pain has been carried out during previous decades, this disorder is still poorly managed by current drugs such as opioids and nonsteroidal anti-inflammatory drugs. Inflammation, tissue injury and/or nerve injury-induced changes in gene expression in sensory neurons of the dorsal root ganglion, spinal cord dorsal horn and pain-associated brain regions are thought to participate in chronic pain genesis; however, how these changes occur is still elusive. Epigenetic modifications including DNA methylation and covalent histone modifications control gene expression. Recent studies have shown that peripheral noxious stimulation changes DNA methylation and histone modifications and that these changes may be related to the induction of pain hypersensitivity under chronic pain conditions. This review summarizes the current knowledge and progress in epigenetic research in chronic pain and discusses the potential role of epigenetic modifications as therapeutic antinociceptive targets in this disorder.

Dexmedetomidine infusion and somatosensory evoked potentials.

Intraoperative neurophysiologic monitoring requires information on the effects of anesthetic drugs because these drugs can directly alter evoked potentials, thus interfering with monitoring. We report on our evaluation of the effect of the recently introduced alpha2-adrenergic agonist, dexmedetomidine, on the somatosensory evoked potentials in two patients undergoing cervico-occipital fusion. Our results suggest that, although dexmedetomidine can affect the later cortical peaks of somatosensory evoked potentials (SSEPs), consistent and reproducible potentials can be recorded.