Nitrous Oxide for the Treatment of Chronic Low Back Pain.

BACKGROUND: Neuropathic back pain is mediated, at least partially, by N-methyl-D-aspartate (NMDA) receptors. Nitrous oxide (N2O) is an NMDA receptor antagonist. We therefore tested the primary hypothesis that patients receiving N2O have lower pain scores after epidural steroid injection than patients not receiving N2O. METHODS: Patients with recurrent low back pain scheduled for epidural steroid blocks were randomly assigned to receive either oxygen (O2, n = 39) or the combination of 50% O2 and 50% N2O during and after each block (N2O, n = 39). Before each injection and at a 3-month follow-up visit, patients completed questionnaires: Oswestry survey, 12-Item Short Form Health Survey questionnaire, Leeds Assessment of Neuropathic Symptoms and Signs pain scale, and Visual Analog Scale. Total opioid use per 24 hours was recorded. The serum samples for tumor necrosis factor-α, interleukin (IL)-6, interferon-γ, IL-10, IL-17A, and IL-1ß assays were collected at every visit and evaluated. Standard descriptive statistics were used to compare the randomized groups on baseline variables. Any imbalanced covariates with an absolute standardized difference >0.44 were adjusted for in both primary and secondary analyses. Both modified intention-to-treat and per-protocol analyses were conducted for our outcomes. Our secondary analyses were per protocol. RESULTS: in patients given N2O (mean [SD], -1.6 [3.0] cm) and O2 (-1.2 [2.6] cm), with difference -0.13 (95% confidence interval: -1.43, 1.17), N2O - O2; P = 0.84. No difference was found between the 2 randomized groups on changes in Leeds Assessment of Neuropathic Symptoms and Signs pain score, Oswestry score, or 12-Item Short Form Health Survey from baseline, or in satisfaction with the procedure, satisfaction with pain treatment, or use of opioid overtime. Overall, no significant differences on any cytokine were found between the 2 groups. The estimated odds ratios of taking opioid was 0.46 (0.12, 1.84) (N2O versus O2; P = 0.12). CONCLUSIONS: N2O administration did not improve pain or psychological or physical aspects of health-related quality of life. N2O does not appear to be an effective treatment for chronic neuropathic back pain.

Intraoperative tight glucose control using hyperinsulinemic normoglycemia increases delirium after cardiac surgery.

BACKGROUND: Postoperative delirium is common in patients recovering from cardiac surgery. Tight glucose control has been shown to reduce mortality and morbidity. Therefore, the authors sought to determine the effect of tight intraoperative glucose control using a hyperinsulinemic-normoglycemic clamp approach on postoperative delirium in patients undergoing cardiac surgery. METHODS: The authors enrolled 198 adult patients having cardiac surgery in this randomized, double-blind, single-center trial. Patients were randomly assigned to either tight intraoperative glucose control with a hyperinsulinemic-normoglycemic clamp (target blood glucose, 80 to 110 mg/dl) or standard therapy (conventional insulin administration with blood glucose target, <150 mg/dl). Delirium was assessed using a comprehensive delirium battery. The authors considered patients to have experienced postoperative delirium when Confusion Assessment Method testing was positive at any assessment. A positive Confusion Assessment Method was defined by the presence of features 1 (acute onset and fluctuating course) and 2 (inattention) and either 3 (disorganized thinking) or 4 (altered consciousness). RESULTS: Patients randomized to tight glucose control were more likely to be diagnosed as being delirious than those assigned to routine glucose control (26 of 93 vs. 15 of 105; relative risk, 1.89; 95% CI, 1.06 to 3.37; P = 0.03), after adjusting for preoperative usage of calcium channel blocker and American Society of Anesthesiologist physical status. Delirium severity, among patients with delirium, was comparable with each glucose management strategy. CONCLUSION: Intraoperative hyperinsulinemic-normoglycemia augments the risk of delirium after cardiac surgery, but not its severity.

The clinical quandary of counseling the moribund critical care patient-a registry analysis of postsurgical outcomes.

PURPOSE: To provide outcomes data to intensivists and surgeons for counseling patients and family members when considering a surgical intervention in a moribund patient. MATERIALS AND METHODS: Retrospective analysis of prospectively collected data from the American College of Surgeons National Surgical Quality Improvement Program database in moribund patients undergoing general surgical procedures. RESULTS: Out of 633,262 patients available in the national registry, 2063 (0.3%) were of moribund status. Post-operative mortality was 52.8% for moribund patients. Those who died had higher rates of compromised respiratory, renal and cognitive dysfunction, were older, less independent prior to surgery and had generally longer surgeries. 83% of patients experienced a major complication including mortality and 17 % of patients experienced minor complications. CONCLUSION: The moribund patient is not as grave as once thought and surgery on these patients may not be futile given the 47% survival rate at 30 days. Postoperative complication rates are high. The data presented provide a meaningful tool for the clinicians in counseling patients and families on the expectations when considering a surgical intervention for moribund patients.

Gender rather than choice of intermediate duration opioids affects emergence after craniotomy for large intracranial tumors.

BACKGROUND: Opioid-based anesthetic techniques are commonly used during neurosurgical procedures. In the present randomized prospective study, we studied emergence after 4 anesthetic regimens combining intermediate duration opioids with isoflurane and nitrous oxide (N(2)O), in patients undergoing craniotomy for large (> 30 mm diameter with intracranial mass effect) intracranial tumors. METHODS: One hundred seven patients were randomized into 4 groups: Group A: fentanyl (≤ 5 µg/kg) + isoflurane (≤ 1 minimum alveolar concentration [MAC]), Group B: sufentanil (1-2 µg/kg plus infusion) + isoflurane (≤ 0.5 MAC), Group C: sufentanil (2 µg/kg bolus only) + isoflurane (≤ 1 MAC), and Group D: alfentanil (100 µg/kg plus infusion) + isoflurane (≤ 0.5 MAC). Boluses were administered as divided doses during induction, laryngoscopy, head pinning, and incision. Blood pressure was controlled at ±25% of baseline levels. All infusions were discontinued at the start of dural closure. Emergence was assessed using a mini-neurologic examination consisting of 7 questions. Groups were compared on time to emergence using survival analysis methods. RESULTS: The groups did not differ regarding extubation time, which occurred at a median of 4 to 6 minutes across groups after discontinuing N(2)O. The median emergence time ranged from 15 to 22.5 minutes and did not differ among groups. However, across all groups more women had emerged by 30 minutes compared with men (83% vs 57%, P â€Š=  .002). The median emergence time in women was found to be significantly shorter (0-15 minutes) than in men (15-30 minutes) (P â€Š=  .012). CONCLUSIONS: No between-group differences in emergence time were observed; the study was stopped early because of evidence that no differences were likely to be found if the study were continued. However, in a post hoc analysis, female gender was associated with faster emergence.

Pre-existing do-not-resuscitate orders are not associated with increased postoperative morbidity at 30 days in surgical patients.

OBJECTIVE: To assess the relationship between pre-existing do-not-resuscitate orders and the incidence of postoperative 30-day minor morbidity in surgical patients. DESIGN: Retrospective analysis of prospectively collected data from the American College of Surgeons National Surgical Quality Improvement Program database in patients undergoing general surgical procedures between 2005 and 2008. SETTING: All U.S. hospitals that participated in the American College of Surgeons National Surgical Quality Improvement Program, which is the nationally validated, risk-adjusted, outcomes-based program that uses a prospective, peer-controlled, validated database to quantify 30-day risk-adjusted surgical outcomes, allowing valid comparison of outcomes among all hospitals in the program. INTERVENTIONS: American College of Surgeons National Surgical Quality Improvement Program data included preoperative risk factors, intraoperative variables, and 30-day postoperative mortality and morbidity outcomes for patients undergoing major surgical procedures in both the inpatient and outpatient setting. The data were collected, validated, and submitted by a trained Surgical Clinical Reviewer at each site. Association between do-not-resuscitate status and minor and major morbidities was assessed using proportional hazards models adjusting for death as a competing risk. MEASUREMENTS AND MAIN RESULTS: Of 635,265 patients in the database, 576,745 patients were analyzed. Propensity-matched analysis successfully matched 2,199 (of 2,687 [81.8%]) patients having pre-existing do-not-resuscitate orders (DNR group) with 6,002 non-do-not-resuscitate control subjects (nonDNR group). At any time point within 30 days of surgery, DNR patients were 16% (95% confidence interval, 3-28%; p = .02) less likely to have a minor complication as compared with nonDNR patients after accounting for the competing risk of death. DNR patients were more likely to experience 30-day mortality compared with nonDNR patients (hazard ratio, 2.3; 95% confidence interval, 1.9-2.7; p < .001). However, there was no association between pre-existing do-not-resuscitate orders and occurrence of any major complication (p = .65) treating death as a competing risk event. When associations between do-not-resuscitate orders and individual minor complications were analyzed, a pre-existing do-not-resuscitate order remained independently associated only with decreased odds of superficial surgical site infection (p = .001). CONCLUSIONS: Undergoing surgery with a pre-existing do-not-resuscitate order did not increase the risk of having a postoperative minor or major morbidity at any time within the 30-day postoperative period. Results of health care in U.S. hospitals do not differ based on presence of do-not-resuscitate orders.

Delayed awakening in dystonia patients undergoing deep brain stimulation surgery.

We aimed to identify the incidence, duration and causes of delayed emergence from anesthesia in patients with dystonia undergoing surgery for deep brain stimulation (DBS) placement. A retrospective review of patients with dystonia who underwent DBS placement was conducted and the following characteristics were noted: age, gender, comorbid conditions, American Society of Anesthesiologists classification, anesthetic agents used, amount of initial dose, amount of infusion dose, duration of the infusion and the time needed for emergence. Twenty-four patients underwent 33 DBS procedures for dystonia. Propofol was administered to 21 patients, in 29 of the 33 procedures. Dexmedetomidine was administered to three patients, in four procedures. The average propofol loading dose was 0.7mg/kg, and the infusion rate was 80microg/kg per minute (min), for an average duration of 89min. The average time of emergence was 36min. Only 31% of patients emerged from propofol anesthesia during the expected time frame, 69% of patients had some degree of delayed emergence, and 24% had a significant delay in emergence. Delayed emergence was more common in younger patients due to the higher loading doses these patients received. This study shows a 69% incidence of delayed emergence in dystonia patients undergoing DBS surgery. It also suggests an association between delayed emergence and younger patients who receive higher loading doses. A possible cause of delayed emergence is excessive anesthetic potentiation of the low output pallidal state in dystonia which may depress the pallido-thalamo-cortical circuitry. Delayed emergence could also result from depression of the previously affected ventral pallidal inputs to the septo-hippocampal system that mediates general anesthesia and awareness. Complex neurotransmitter disturbances may also be involved.

A propensity-matched comparison of the incidence of new-onset postoperative atrial arrhythmias in cardiac and noncardiac thoracic surgery patients.

OBJECTIVE: The primary aim of this investigation was to compare the incidence of new-onset postoperative atrial arrhythmias (POAAs) in cardiac versus noncardiac thoracic surgery patients. A subgroup analysis also was performed in the cardiac surgery patients comparing POAAs in patients who underwent cardiac surgery on and off cardiopulmonary bypass (CPB). DESIGN: This was a retrospective study using the Department of Cardiothoracic Anesthesia patient registry. All patients (n = 33,500) undergoing cardiac (n = 29,057) and noncardiac thoracic (n = 4,443) surgeries between 1993 and 2004 were identified from the patient registry. Two propensity-matched comparisons for the incidence of POAAs were made: (1) in cardiac surgery patients versus noncardiac thoracic surgery patients and (2) in patients undergoing cardiac surgery with versus without CPB. SETTING: A large metropolitan multidisciplinary clinic. PARTICIPANTS: Patients. INTERVENTION: No interventions were done because this was a retrospective study. MEASUREMENTS AND MAIN RESULTS: The cardiac patients had a significantly higher incidence of POAAs when compared with noncardiac thoracic surgery patients (11.6% v 7.5%, p < 0.001). There was no significant difference in the incidence of POAAs between patients undergoing CPB versus off-pump CPB (13.3% v 12.3%, p = 0.3). CONCLUSION: The incidence of new-onset POAAs was higher in patients undergoing cardiac surgery than in patients undergoing noncardiac thoracic surgery in propensity-matched patient groups. CPB was not associated with new-onset POAAs.

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.

Precordial Doppler probe placement for optimal detection of venous air embolism during craniotomy.

Verification of appropriate precordial Doppler probe position over the anterior chest wall is crucial for early detection of venous air embolism. We studied responses to normal saline (NS) and carbon dioxide (CO2) test injections at various probe locations during elective craniotomy. All patients received four IV injections (10 mL of NS and 1 mL of CO2 via central and peripheral venous catheters). Doppler sounds were simultaneously recorded with two separate probes. In Group A, probes were placed in left and right parasternal positions. In Group B, the left probe was intentionally malpositioned as far laterally over the left precordium as was compatible with an audible signal. In Group A (n = 23), a left parasternal Doppler signal was easily obtainable in 23 of 23 patients, versus 18 of 23 patients for the right parasternal probe (P < 0.05). In Group B (n = 17), central CO2 injection yielded a positive right parasternal response rate of 88% compared with 29% over the far left precordium (P < 0.015), where central NS injections yielded a 76% response rate (P < 0.015 versus central CO2 injection). Left parasternal placement is at least as sensitive to clinical venous air embolism events as right parasternal placement. Peripheral saline injection represents a viable alternative (83% response rate). Vigorous central injection of 10 mL of NS however, risks false positive verification of left lateral precordial probe placement.

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.

Fever is associated with third ventricular shift after intracerebral hemorrhage: pathophysiologic implications.

BACKGROUND: Studies have shown the detrimental effect of increased temperature on brain injury. Fever is common after intracerebral hemorrhage (ICH). The term 'central fever' is often used when no cause is identified. AIM: The aim of the study was to determine the correlation of fever with third ventricular shift in 61 patients with ICH and hypothesize about the mechanism of fever. SETTING: Neurointensive Care Unit. DESIGN: Prospective observational study. MATERIALS AND METHODS: From August 1999 to April 2000, data from 61 patients with ICH were prospectively collected including maximum temperature (Tmax) and fever (T> 37.5 degrees C) at 24, 48, 72 and 96 hours, ICH volume, and third ventricular shift. Outcome measures included discharge mortality, 3-month National Institute of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), and Barthel Index (BI). STATISTICAL ANALYSIS: Spearman correlation coefficient, Mann-Whitney test, and logistic regression were used to assess relationships. RESULTS: Fifty-six per cent of patients had fever in the first 24 hours and 53% for at least two consecutive days. There was a correlation between ICH volume and Tmax at 24 hours (P =0.04) and 72 hours (P =0.03) and fever at 24 hours (P =0.039) and 72 hours (P =0.036). Tmax at 72 hours correlated with third ventricular shift (P =0.01). Those with shift were more likely to have fever within the first 72 hours (P =0.049) and worse outcome. Fever at 72 hours was associated with a higher discharge mortality (P =0.046) and trend of a worse 3-month NIHSS score (P =0.06). CONCLUSION: Fever is common after ICH and correlates with ICH volume and third ventricular shift suggesting a role of hypothalamic compression in "central fever." There was a trend towards a worse outcome with fever.

Massive pulmonary thromboembolism during elective spine surgery.

Massive pulmonary thromboembolism (PTE) is a condition that can still be seen in the operating room despite the use of thromboprophylaxis. A high degree of suspicion of this condition is necessary to achieve an early diagnosis and a rapid treatment to improve patient outcome. We report on a 27-year-old patient who sustained a massive PTE while undergoing a second-stage anterior release and posterior fusion of his thoracolumbar spine for idiopathic scoliosis.

Venous air embolism during deep brain stimulation surgery in an awake supine patient.

Deep brain stimulation (DBS) of the subthalamic nucleus and globus pallidus is used to improve Parkinsonian symptoms and reduce levodopa-induced motor complications in Parkinson's disease (PD). This procedure is usually performed with minimal or no sedation to allow accurate feedback from patients during surgery. Venous air embolism (VAE) has been previously reported in patients undergoing awake neurosurgical procedures for brain tumors or pallidotomy for PD. We describe a case of intraoperative VAE in an awake, supine patient while undergoing DBS surgery for PD who presented with coughing, tachypnea and hypoxemia. The difference in clinical presentation between VAE in awake vs. anesthetized patients is discussed as are intraoperative monitoring techniques and management options.

Multimodal monitoring in the neurological intensive care unit.

BACKGROUND: Neurocritical care is a specialty that focuses on the critical care management of patients with catastrophic neurologic diseases. Brain ischemia and hypoxia are often central causes of brain damage in these patients. Until recently, the only methods widely accepted for monitoring in the neurological intensive care unit have been intracranial pressure and cerebral perfusion pressure monitoring. Recent developments in technology have resulted in several new monitoring techniques that can provide the neurointensivist with information, at the cellular level, that can help guide management. REVIEW SUMMARY: The brain requires a continuous blood-borne supply of oxygen and glucose for normal metabolism. Ischemia occurs when supply is insufficient to meet the metabolic demand. Cerebral blood flow can now be directly monitored using laser Doppler or thermal diffusion techniques. Transcranial cerebral oximetry can estimate regional cerebral oxygen saturation, although the reliability is questionable. Jugular bulb oximetry can provide a global assessment of oxygen delivery, and consumption and brain tissue oxygen tension monitoring can provide a focal measurement of cerebral oxygenation. Intracerebral microdialysis can provide information about glucose metabolism and the overall health of the neuron. CONCLUSIONS: New monitoring techniques can provide the neurointensivist with crucial information about brain physiology and metabolism. Combining these techniques ("multimodal monitoring") can produce a more accurate overall picture. This approach, along with new computer systems for integrating data at the bedside, may change the way patients with brain injury are monitored and treated in the future.

Bispectral Index monitoring correlates with sedation scales in brain-injured patients.

OBJECTIVE: Monitoring critically ill, brain-injured patients with a decreased level of consciousness is challenging. Our goal is to determine in this population the correlation between the Bispectral Index (BIS) and three commonly used sedation agitation scales: the Richmond Agitation-Sedation Scale (RASS), the Sedation-Agitation Scale (SAS) and the Glasgow Coma Scale (GCS) scores. DESIGN: Prospective, single-blinded observational study. SETTING: Eight-bed neurology-neurosurgery intensive care unit at the Cleveland Clinic Foundation. PATIENTS: Thirty critically ill patients admitted to the neurointensive care unit with primary brain injury and a decreased level of consciousness. MEASUREMENTS AND MAIN RESULTS: Patients were prospectively evaluated for level of consciousness using the RASS, SAS, and GCS every hour and simultaneously were monitored continuously with a BIS monitor for 6 hrs. A Spearman's correlation coefficient was used to correlate the BIS scores with clinical scales. In 15 patients monitored with the newer BIS XP version, the BIS values correlated significantly with the RASS (R2 = .810; p < .0001), SAS (R2 = .725; p < .0001), and GCS (R2 = .655; p < .0001). In 15 patients monitored with the older BIS 2.1.1 software, the correlation was as follows: for RASS, R2 = .30 (p < .008), for SAS: R2 = .376 (p < .001), and for GCS: R2 = .274 (p < .015). This correlation was maintained in patients who received sedative medications. CONCLUSIONS: A statistically significant correlation existed between BIS values and the RASS, SAS, and GCS scores in critically ill brain-injured patients, with and without sedation. The newer BIS XP software package may be a useful adjunctive tool in objective assessment of level of consciousness in brain-injured patients.