Under the Helmet: Perioperative Concussion-Review of Current Literature and Targets for Research.

Patients with recent concussion experience disruption in neurocellular and neurometabolic function that may persist beyond symptom resolution. Patients may require anesthesia to facilitate diagnostic or surgical procedures following concussion; these procedures may or may not be related to the injury that caused the patient to sustain a concussion. As our knowledge about concussion continues to advance, it is imperative that anesthesiologists remain up to date with current principles. This Focused Review will update readers on the latest concussion literature, discuss the potential impact of concussion on perianesthetic care, and identify knowledge gaps in our understanding of concussion.

Neuroanesthesiology Update.

This review summarizes the literature published in 2020 that is relevant to the perioperative care of neurosurgical patients and patients with neurological diseases as well as critically ill patients with neurological diseases. Broad topics include general perioperative neuroscientific considerations, stroke, traumatic brain injury, monitoring, anesthetic neurotoxicity, and perioperative disorders of cognitive function.

Anesthesia During Positive-pressure Myelogram: A New Role for Cerebral Oximetry.

BACKGROUND: Positive-pressure myelogram (PPM) is an emerging radiologic study used to localize spinal dural defects. During PPM, cerebrospinal fluid pressure (CSFp) is increased by injecting saline with contrast into the cerebrospinal fluid. This has the potential to increase intracranial pressure and compromise cerebral perfusion. METHODS: We performed a retrospective chart review and analysis of 11 patients. The aim was to describe the periprocedural anesthetic management of patients undergoing PPM. RESULTS: All patients underwent PPM with general anesthesia and intra-arterial blood pressure and near-infrared spectroscopy monitoring of regional cerebral tissue oxygen saturation. Mean±SD maximum lumbar CSFp was 58±12 mm Hg. Upon intrathecal injection, mean systolic blood pressure increased from 115±21 to 142±32 mm Hg (P<0.001), diastolic blood pressure from 68±12 to 80±20 mm Hg (P≤0.001), and mean blood pressure from 87±10 to 98±14 mm Hg (P=0.02). Ten of 11 patients received blood pressure augmentation with phenylephrine to minimize the risk of reduced cerebral perfusion secondary to increased CSFp after intrathecal injection. The mean heart rate before and following injection was similar (68±15 vs. 70±15 bpm, respectively; P=0.16). There was a decrease in regional cerebral oxygen saturation after positioning from supine to prone position (79±10% to 74±9%, P=0.02) and a further decrease upon intrathecal injection (75±10% to 69±9%, P≤0.01). CONCLUSIONS: Systemic blood pressure increased following intrathecal injection during PPM, possibly due to a physiologic response to intracranial hypertension/reduced cerebral perfusion or administration of phenylephrine. Regional cerebral oxygen saturation decreased with the change to prone position and further decreased upon intrathecal injection. Cerebral near-infrared spectroscopy has a potential role to monitor the adequacy of cerebral perfusion and guide adjustment of systemic blood pressure during PPM.

Recent Preoperative Concussion and Postoperative Complications: A Retrospective Matched-cohort Study.

BACKGROUND: Physiological alterations during the perianesthetic period may contribute to secondary neurocognitive injury after a concussion. METHODS: Patients exposed to concussion and who received an anesthetic within 90 days were matched to unexposed patients without concussion. Intraoperative and postoperative events were compared. Subgroup analyses assessed relationships among patients with a concussion in the prior 30, 31 to 60, and 61 to 90 days and their respective unexposed matches. To facilitate identification of potential targets for further investigation, statistical comparisons are reported before, as well as after, correction for multiple comparisons. RESULTS: Sixty concussion patients were matched to 176 unexposed patients. Before correction, 28.3% postconcussion versus 14.8% unexposed patients reported postanesthesia care unit pain score≥7 (P=0.02); 16.7% concussion versus 6.5% unexposed patients reported headache within 90 days of anesthesia (P=0.02) and 23.5% of patients who received surgery and anesthesia within 30 days of concussion experienced headache within 90 days of anesthesia compared with 7.1% in the unexposed group (P=0.01). Patients who experienced concussion and had anesthesia between 31 and 60 days after injury had a postanesthesia care unit Richmond Agitation and Sedation Scale score of -1.61±1.29 versus a score of -0.2±0.45 in unexposed patients (P=0.002). After adjusting the P-value threshold for multiple comparisons, the P-value for significance was instead 0.0016 for the overall cohort. Our study revealed no significant associations with application of adjusted significance thresholds. CONCLUSIONS: There were no differences in intraoperative and postoperative outcomes in patients with recent concussion compared with unexposed patients. Before correction for multiple comparisons, several potential targets for further investigation are identified. Well-powered studies are warranted.

Perceived Benefits and Barriers to a Career in Neuroanesthesiology: A Pilot Survey of Anesthesiology Clinicians.

BACKGROUND: Despite advances in perioperative neuroscience, there is low interest among anesthesiology trainees to pursue subspecialty training in neuroanesthesiology. We conducted a pilot survey to assess attitudes about neuroanesthesiology fellowship training. MATERIALS AND METHODS: A confidential survey was distributed to an international cohort of anesthesiology attendings and trainees between January 15, 2017 and February 26, 2017. RESULTS: A total of 463 responses were received. Overall, 309 (67%), 30 (6%), 116 (25%), and 8 (2%) of respondents identified themselves as attendings, fellows, residents, and "other," respectively. In total, 390 (84%) of respondents were from the United States. Individuals typically pursue anesthesiology fellowship training because of interest in the subspecialty, acquisition of a special skill set, and the role of fellowship training in career planning and advancement. Overall, 64% of attendings, 56% of fellows, and 55% of residents favored accreditation of neuroanesthesiology fellowships, although opinion was divided regarding the role of accreditation in increasing interest in the specialty. Respondents believe that increased opportunities for research and greater exposure to neurocritical care and neurological monitoring methods would increase interest in neuroanesthesiology fellowship training. Perceived barriers to neuroanesthesiology fellowship training were perceptions that residency provides adequate training in neuroanesthesiology, that a unique skill set is not acquired, and that there are limited job opportunities available to those with neuroanesthesiology fellowship training. CONCLUSIONS: In this pilot survey, we identified several factors that trainees consider when deciding to undertake subspecialty training and barriers that might limit interest in pursuing neuroanesthesiology subspecialty training. Our findings may be used to guide curricular development and identify factors that might increase interest among trainees in pursuing neuroanesthesiology fellowship training.

Anesthesia and the brain after concussion.

PURPOSE OF REVIEW: To provide an overview of acute and chronic repeated concussion. We address epidemiology, pathophysiology, anesthetic utilization, and provide some broad-based care recommendations. RECENT FINDINGS: Acute concussion is associated with altered cerebral hemodynamics. These aberrations can persist despite resolution of signs and symptoms. Multiple repeated concussions can cause chronic traumatic encephalopathy, a disorder associated with pathologic findings similar to some organic dementias. Anesthetic utilization is common following concussion, especially soon after injury, a time when the brain may be most vulnerable to secondary injury. SUMMARY: Brain physiology may be abnormal following concussion and these abnormalities may persist despite resolutions of clinical manifestations. Those with recent concussion or chronic repeated concussion may be susceptible to secondary injury in the perioperative period. Clinicians should suspect concussion in any patient with recent trauma and strive to maintain cerebral homeostasis in the perianesthetic period.

Safety and Efficacy of Retrograde Pyeloperfusion for Ureteral Protection during Renal Tumor Cryoablation.

PURPOSE: To determine safety and efficacy of retrograde pyeloperfusion for ureteral protection during cryoablation of adjacent renal tumors. MATERIALS AND METHODS: Retrospective review of 155 patients treated with renal cryoablation, including adjunctive retrograde pyeloperfusion, from 2005 to 2019 was performed. Ice contacted the ureter in 67 of the 155 patients who represented the study cohort. Median patient age was 68 years old (interquartile range [61, 74]), 52 patients (78%) were male, and 37 tumors (55%) were clear cell histology. Mean tumor size was 3.4 ± 1.3 cm, and 42 tumors (63%) were located at the lower pole. Treatment-related complication and oncologic outcomes were recorded based on a review of post-procedural images and chart review. RESULTS: Technical success of cryoablation was attained in 67 cases (100%), and technical success of pyeloperfusion was attained in 66 cases (99%). A total of 13 patients (19.4%) experienced SIR major C or D complications related to the procedure, including hemorrhage (n = 4), urine leak (n = 3), transient urinary obstruction (n = 2), pulmonary embolism (n = 1), hypertensive urgency (n = 1), acute respiratory failure (n = 1), and ureteropelvic junction (UPJ) stricture (n = 1). No complications were attributable to pyeloperfusion. Three of 45 patients with biopsy-proven renal cell carcinoma experienced local recurrence resulting in local recurrence-free survival of 92% (95% confidence interval, 81.5%-100%) 3 years after ablation. CONCLUSIONS: Retrograde pyeloperfusion of the renal collecting system is a relatively safe and efficacious option for ureteral protection during renal tumor cryoablation. This adjunctive procedure should be considered for patients in whom cryoablation of a renal mass could potentially involve the ureter.

Neuroanesthesiology Update.

This review is intended to provide a summary of the literature pertaining to the perioperative care of neurosurgical patients and patients with neurological diseases. General topics addressed in this review include general neurosurgical considerations, stroke, neurological monitoring, and perioperative disorders of cognitive function.

Anesthesia With and Without Nitrous Oxide and Long-term Cognitive Trajectories in Older Adults.

BACKGROUND: We evaluated the hypothesis that the rate of postoperative decline in global cognition is greater in older adults exposed to general anesthesia with nitrous oxide (N2O) compared to general anesthesia without N2O. METHODS: Longitudinal measures of cognitive function were analyzed in nondemented adults, 70-91 years of age, enrolled in the Mayo Clinic Study of Aging. Linear mixed-effects models with time-varying covariates assessed the relationship between exposure to surgery with general anesthesia (surgery/GA) with or without N2O and the rate of long-term cognitive changes. Global cognition and domain-specific cognitive outcomes were defined using z scores, which measure how far an observation is, in standard deviations, from the unimpaired population mean. RESULTS: The analysis included 1819 participants: 280 exposed to GA without N2O following enrollment and before censoring during follow-up (median [interquartile range {IQR}] follow-up of 5.4 [3.9-7.9] years); 256 exposed to GA with N2O (follow-up 5.6 [4.0-7.9] years); and 1283 not exposed to surgery/GA (follow-up 4.1 [2.5-6.4] years). The slope of the global cognitive z score was significantly more negative following exposure to surgery/GA after enrollment (change in slope of -0.062 [95% confidence interval {CI}, -0.085 to -0.039] for GA without N2O, and -0.058 [95% CI, -0.080 to -0.035] for GA with N2O, both P < .001). The change in slope following exposure to surgery/GA did not differ between those exposed to anesthesia without versus with N2O (estimated difference -0.004 [95% CI, -0.035 to 0.026], P = .783). CONCLUSIONS: Exposure to surgery/GA is associated with a small, but statistically significant decline in cognitive z scores. Cognitive decline did not differ between anesthetics with and without N2O. This finding provides evidence that the use of N2O in older adults does not need to be avoided because of concerns related to decline in cognition.

Neuroanesthesiology Update.

This review provides a summary of the literature pertaining to the perioperative care of neurosurgical patients and patients with neurological diseases. General topics addressed in this review include general neurosurgical considerations, stroke, traumatic brain injury, neuromonitoring, neurotoxicity, and perioperative disorders of cognitive function.

Urgent Repositioning After Venous Air Embolism During Intracranial Surgery in the Seated Position: A Case Series.

BACKGROUND: Venous air embolism (VAE) is a well-described complication of neurosurgical procedures performed in the seated position. Although most often clinically insignificant, VAE may result in hemodynamic or neurological compromise resulting in urgent change to a level position. The incidence, intraoperative course, and outcome in such patients are provided in this large retrospective study. METHODS: Patients undergoing a neurosurgical procedure in the seated position at a single institution between January 2000 and October 2013 were identified. Corresponding medical records, neurosurgical operative reports, and computerized anesthetic records were searched for intraoperative VAE diagnosis. Extreme VAE was defined as a case in which urgent seated to level position change was performed for patient safety. Detailed examples of extreme VAE cases are described, including their intraoperative course, VAE management, and postoperative outcomes. RESULTS: There were 8 extreme VAE (0.47% incidence), 6 during suboccipital craniotomy (1.5%) and 2 during deep brain stimulator implantation (0.6%). VAE-associated end-expired CO2 and mean arterial pressure reductions rapidly normalized following position change. No new neurological deficits or cardiac events associated with extreme VAE were observed. In 5 of 8, surgery was completed. Central venous catheter placement and aspiration during VAE played no demonstrable role in patient outcome. CONCLUSIONS: Extreme VAE during seated intracranial neurosurgical procedures is infrequent. Extreme VAE-associated CO2 exchange and hemodynamic consequences from VAE were transient, recovering quickly back to baseline without significant neurological or cardiopulmonary morbidity.

The relationship between end-expired carbon dioxide tension and severity of venous air embolism during sitting neurosurgical procedures - A contemporary analysis.

STUDY OBJECTIVE: Determine if changes in expired carbon dioxide tension correlate with the severity of venous air embolism (VAE) associated hemodynamic changes in humans. DESIGN: Retrospective case series. SETTING: A single academic medical center with high-volume neurosurgical practice. PATIENTS: One hundred forty seven adult patients having neurosurgical procedures performed with general anesthesia in the sitting position who experienced venous air embolism. INTERVENTIONS: Identification of documentation of venous air embolism by either precordial Doppler sonography or transesophageal echocardiography. MEASUREMENT: Retrospective determination of changes in end-expired carbon dioxide (EECO2) changes associated with venous air embolism. MAIN RESULTS: Greater absolute and relative decreases in end-expired carbon dioxide tension were associated with greater hemodynamic manifestations of venous air embolism. However, based on receiver operating characteristic curve analysis, the absolute and relative changes in EECO2 have moderate utility for predicting the severity of hemodynamic consequences of venous air embolism as area under the curve for absolute and relative carbon dioxide tensions were 0.7654 and 0.7263, respectively. CONCLUSIONS: Greater magnitude of decreases in EECO2 is associated with hemodynamically-significant VAE in mechanically-ventilated patients. However, the magnitude of changes may have limited utility to diagnose VAE or exclude the diagnosis of VAE in patients with unexplained intraoperative hypotension.

Neuroanesthesiology Update.

We provide a synopsis of innovative research, recurring themes, and novel experimental findings pertinent to the care of neurosurgical patients and critically ill patients with neurological diseases. We cover the following broad topics: general neurosurgery, spine surgery, stroke, traumatic brain injury, monitoring, and anesthetic neurotoxicity.

Comparison of Anesthetic Management and Outcomes in Patients Having Either Transnasal or Transoral Endoscopic Odontoid Process Surgery.

BACKGROUND: Endoscopic neurosurgical procedures involving the upper cervical vertebrae are challenging due to a narrow operating field and close proximity to vital anatomical structures. Historically, transoropharyngeal (transoral) endoscopy has been the preferred approach. More recently, however, an endoscopic transnasal approach was developed as an alternative method in hopes to reduce postoperative dysphagia, a common complication following transoral neurosurgery. METHODS: Twenty-two endoscopic neurosurgical cases involving the odontoid or C1 vertebra were reviewed between January 1, 2005 and December 31, 2015 (17 and 5 through transoral and transnasal approaches, respectively). Patient demographics, anesthetic technique, intraoperative course, and postoperative outcomes such as were recorded. RESULTS: Patients who underwent transnasal odontoidectomy had a shorter length of stay and lower rates of tracheostomy compared with those having similar surgery via the transoral route. In those having transoral surgery, no patient presented to the operating room with a preexisting tracheostomy. In 16 of 17 patients within the transoral group, a tracheostomy was performed. In those having transnasal surgery, 2 of 5 patients had a preexisting tracheostomy. In the remaining 3 of 5 patients, orotracheal intubation was performed and patients were extubated after the procedure. CONCLUSIONS: The transnasal odontoid resection technique may become a more popular surgical approach without increasing rates of complications compared with those having transoral surgery. Ultimately, a larger, study is needed to further clarify these relationships.

Anesthesia-Related Outcomes for Endovascular Stroke Revascularization: A Systematic Review and Meta-Analysis.

BACKGROUND AND PURPOSE: There is currently controversy on the ideal anesthesia strategy during mechanical thrombectomy for acute ischemic stroke. We performed a systematic review and meta-analysis of studies comparing clinical and angiographic outcomes of patients undergoing general anesthesia (GA group) and those receiving either local anesthesia or conscious sedation (non-GA group). METHODS: A literature search on anesthesia and endovascular treatment of acute ischemic stroke was performed. Using random-effects meta-analysis, we evaluated the following outcomes: recanalization rate, good functional outcome at 90 days (modified Rankin Score≤2), symptomatic intracranial hemorrhage, death, vascular complications, respiratory complications, procedure time, and time to groin puncture. RESULTS: Twenty-two studies (3 randomized controlled trials and 19 observational studies), including 4716 patients (1819 GA and 2897 non-GA) were included. In the nonadjusted analysis, patients in the GA group had higher odds of death (odds ratio [OR], 2.02; 95% confidence interval [CI], 1.66-2.45) and respiratory complications (OR, 1.70; 95% CI, 1.22-2.37) and lower odds of good functional outcome (OR, 0.58; 95% CI, 0.48-0.64) compared with the non-GA group. There was no difference in procedure time between the 2 primary comparison groups. When adjusting for baseline National Institutes of Health Stroke Scale, GA was still associated with lower odds of good functional outcome (OR, 0.59; 95% CI, 0.29-0.94). When considering studies performed in the stent-retriever/aspiration era, there was no significant difference in good neurological outcome rates (OR, 0.84; 95% CI, 0.67-1.06). CONCLUSIONS: Acute ischemic stroke patients undergoing intra-arterial therapy may have worse outcomes when treated with GA as compared with conscious sedation/local anesthesia. However, major limitations of current evidence (ie, retrospective studies and selection bias) indicate a need for adequately powered, multicenter randomized controlled trials to answer this question.

Exposure to Surgery and Anesthesia After Concussion Due to Mild Traumatic Brain Injury.

OBJECTIVE: To describe the epidemiology of surgical and anesthetic procedures in patients recently diagnosed as having a concussion due to mild traumatic brain injury. PATIENTS AND METHODS: Study patients presented to a tertiary care center after a concussion due to mild traumatic brain injury from July 1, 2005, through June 30, 2015, and underwent a surgical procedure and anesthesia support under the direct or indirect care of a physician anesthesiologist. RESULTS: During the study period, 1038 patients met all the study inclusion criteria and subsequently received 1820 anesthetics. In this population of anesthetized patients, rates of diagnosed concussions due to sports injuries, falls, and assaults, but not motor vehicle accidents, increased during 2010-2011. Concussions were diagnosed in 965 patients (93%) within 1 week after injury. In the 552 patients who had surgery within 1 week after concussive injury, 29 (5%) had anesthesia and surgical procedures unrelated to their concussion-producing traumatic injury. The highest use of surgery occurred early after injury and most frequently required general anesthesia. Orthopedic and general surgical procedures accounted for 57% of procedures. Nine patients received 29 anesthetics before a concussion diagnosis, and all of these patients had been involved in motor vehicle accidents and received at least 1 anesthetic within 1 week of injury. CONCLUSION: Surgical and anesthesia use are common in patients after concussion. Clinicians should have increased awareness for concussion in patients who sustain a trauma and may need to take measures to avoid potentially injury-augmenting cerebral physiology in these patients.

Neuroanesthesiology Update.

We reviewed manuscripts published in 2016 that are related to the care of neurosurgical patients or the perioperative care of patients with neurological diseases. We address the broad categories of general neurosurgery and neuroanesthesiology, anesthetic neurotoxicity and neuroprotection, stroke, traumatic brain injury, and nervous system monitoring.