Anesthesia for the patient with a recently diagnosed concussion: think about the brain!

Some patients require emergent, urgent, or elective surgery in the time period immediately following diagnosis of concussion. However, changes in brain homeostatic mechanisms following a concussion and concern for secondary brain injury can complicate the decision as to whether or not a surgery should proceed or be postponed. Given the paucity of available evidence, further evaluation of the use of anesthesia in a patient with concussion is warranted. This article summarizes what is currently known about the relevant pathophysiology of concussion, intraoperative anesthesia considerations, and effects of anesthesia on concussion outcomes in an attempt to help providers understand the risks that may accompany surgery and anesthesia in this patient population. While most contraindications to the use of anesthesia in concussed patients are relative, there are nonetheless pathophysiologic changes associated with a concussion that can increase risk of its use. Understanding these changes and anesthetic implications can help providers optimize outcomes in this patient population.

Society for Neuroscience in Anesthesiology & Critical Care (SNACC) Neuroanesthesiology Education Milestones for Resident Education.

BACKGROUND: The Accreditation Council for Graduate Medical Education (ACGME) has introduced competency-based assessments (milestones) for resident education. However, the existing milestones for Anesthesiology are not specific to Neuroanesthesiology. The Society for Neuroscience in Anesthesiology & Critical Care (SNACC) commissioned a task force to adapt the ACGME anesthesiology milestones for use in Neuroanesthesiology training, and to provide recommendations for implementing milestones. METHODS: A 7-member expert task force supported by an advisory committee developed the initial milestones by consensus. Written permission was given by the ACGME. The milestones were refined following 3-month pilot use in 14 departments across the United States and inputs from SNACC members. Final milestones were approved by the SNACC Board of Directors. RESULTS: Twelve Neuroanesthesiology-specific milestones in 5 major ACGME domains are recommended; these were identified as most pertinent to this subspecialty rotation. These pertain to patient care (7 milestones), medical knowledge (2 milestones), practice-based learning and improvement (1 milestone), and interpersonal and communication skills (2 milestones). Each milestone was described in detail, with clear outline of expectations at various levels of training. CONCLUSIONS: The SNACC Neuroanesthesiology milestones provide a framework for reviewing resident performance and are expected to facilitate improved use of ACGME milestones during Neuroanesthesiology subspecialty training. The task force recommends that the target should be to accomplish level 4 or higher milestones by the end of residency training. Individual programs should decide the implications of a resident not meeting the expected milestones.

Chronic Skull Base Erosion from Temporomandibular Joint Disease Causes Generalized Seizure and Profound Lactic Acidosis.

This report displays a rare presentation of lactic acidosis in the setting of status epilepticus (SE). The differential diagnosis of lactic acidosis is broad and typically originates from states of shock; however, this report highlights an alternative and rare etiology, SE, due to chronic skull base erosion from temporomandibular joint (TMJ) disease. Lactic acidosis is defined by a pH below 7.35 in the setting of lactate values greater than 5 mmol/L. Two broad classifications of lactic acidosis exist: a type A lactic acidosis which stems from global or localized tissue hypoxia or a type B lactic acidosis which occurs once mitochondrial oxidative capacity is unable to match glucose metabolism. SE is an example of a type A lactic acidosis in which oxygen delivery is unable to meet increased cellular energy requirements. This report is consistent with a prior case series that consists of five patients experiencing generalized tonic-clonic (GTC) seizures and lactic acidosis. These patients presented with a pH range of 6.8-7.41 and lactate range of 3.8-22.4 mmol/L. Although severe lactic acidosis following GTC has been described, this is the first report in the literature of chronic skull base erosion from TMJ disease causing SE.

Prevalence of discordant elevations of state entropy and bispectral index in patients at amnestic sevoflurane concentrations: a historical cohort study.

BACKGROUND: Processed electroencephalogram (EEG) monitors help assess the hypnotic state during general anesthesia or sedation. Maintaining the bispectral index (BIS) or state entropy (SE) between 40 and 60 has been recommended to mitigate anesthesia awareness. Nonetheless, SEs > 70 were frequently observed at end-tidal sevoflurane concentrations unlikely to allow awareness. We sought to determine the prevalence of elevated discordant measurements during BIS and SE monitoring. METHODS: Electronic data collected over 11 months at two academic hospitals were retrospectively reviewed. At the hospital using SE, all cases were included with patients ≥ 18 yr and sevoflurane administered for at least 30 min during surgery. A cohort of cases propensity matched by age and American Society of Anesthesiologist Physical Status were selected from the hospital using BIS. Elevated discordant EEG indices were defined as values > 70 occurring during stable end-tidal sevoflurane concentrations > 1.5%. The odds ratio (OR) based on the probability of a case having at least one elevated discordant SE or BIS lasting ≥ two minutes (primary endpoint) was calculated. RESULTS: At each hospital, 3,690 cases were studied. The mean (95% confidence interval [CI]) incidence of cases with at least one interval of an elevated discordant EEG index lasting at least two minutes was 3.6% (2.8% to 4.4%) for SE compared with 0.24% (0.17% to 0.27%) for BIS (pooled OR, 17.0; 95% CI, 8.3 to 34.7; P < 0.001). CONCLUSIONS: The prevalence of an elevated discordant EEG index is much greater with SE than with BIS. Elevated index values occurring at anesthetic concentrations well above the awareness threshold need to be assessed to determine if they indicate an inadequate depth of anesthesia requiring treatment or if they simply reflect the underlying monitoring algorithm.

Awake intubating laryngeal mask airway placement in a morbidly obese patient with ankylosing spondylitis and unstable thoracic spine.

Intubating laryngeal mask airways can be used to provide continuous ventilation throughout intubation. This is a case of a morbidly obese (body mass index = 58) 65-year-old woman with T10 and T11 compression fractures. Optimal positioning for airway management was hindered by her unstable spine, minimal neck range of motion, and extreme pain with any movement. An intubating laryngeal mask airway was placed in the awake, topically anesthetized patient, and the laryngeal mask airway and endotracheal tube combination was left in place throughout surgery.

Transient bilateral brainstem dysfunction caused by topical administration of papaverine.

Papaverine has been associated with transient cranial nerve dysfunction after topical application during craniotomy. The authors report similar dysfunction after the use of papaverine affected brainstem structures. Two patients undergoing craniotomy for clipping of an aneurysm experienced bilateral depression of cortical somatosensory evoked potentials to both median and tibial nerve stimulation after administration of papaverine. Arterial blood gas analysis, hemodynamic parameters, and anesthetic levels remained constant throughout these somatosensory evoked potential changes. In addition, intraoperative angiography and immediate postoperative CT imaging showed intact blood flow with complete exclusion of the aneurysm. Both patients recovered within 1-2 hours and had normal neurological examination findings after extubation. Topical papaverine use may be associated with direct effects on brainstem structures. The transient nature of those changes suggests that aggressive intervention may not be needed. Maneuvers to limit the spread of papaverine to basal cisterns should be considered.

The Stealth Station Image Guidance System may interfere with pulse oximetry.

PURPOSE: Interference on pulse oximetry can come from many sources. We found an additional source of interference from the Stealth Station. This article gives an overview of sources of pulse oximeter interference so that clinicians can better prevent them. Technical features: This article discusses the infrared disturbances caused by the Stealth Station. The Stealth Station is a frameless stereotactic positioning system that utilizes a three dimensional location system to measure the position of the patient and the surgical tools, and to relate those positions to previously recorded imaging. To understand the disturbance caused by the Stealth Station, we discuss its operation and that of pulse oximeter monitors. Pulse oximeter interference can come from volume artifacts, electrical and light noise, and can be caused by issues related to the patient. Because the passive Stealth Station contains a strong infrared light source, interference caused by light is a likely reason for the interference we noted. Pulse oximeters rely on the time-variant light signal modulated by arterial volume variations in the finger. Although relatively immune to static light sources, pulse oximeters are extremely sensitive to time-varying light sources. The light emitted by the passive Stealth Station is time-varying at 4 Hz and this is causing the pulse oximeter to provide invalid results. Shielding can generally be used to stop the light from the Stealth Station from being picked up by the pulse oximeter sensor. CONCLUSION: Infrared light interference can be very common, but is easily dealt with if one is aware of it.

The effect of body inclination during prone positioning on intraocular pressure in awake volunteers: a comparison of two operating tables.

Visual loss is a rare, but catastrophic, complication of surgery in the prone position. The prone position increases intraocular pressure (IOP), which may lead to visual loss by decreasing perfusion of the anterior optic nerve. We tested whether the reverse Trendelenburg position ameliorates the increase in IOP caused by prone positioning. Furthermore, we compared two prone positioning set ups. The IOP of 10 healthy awake volunteers was measured in the prone position at 3 different degrees of inclination (horizontal, 10 degrees reverse Trendelenburg, and 10 degrees Trendelenburg) and in the sitting and supine positions in a randomized crossover study comparing the Jackson table and the Wilson frame. In a given eye, all prone IOP values (median [25th-75th percentile] exceeded those of the sitting (15.0 mm Hg [12.8-16.3 mm Hg]) and supine (16.8mm Hg [14.0-18.3 mm Hg]) positions. IOPs in the reverse Trendelenburg, horizontal, and Trendelenburg positions were 20.3 mm Hg (16.3-22.5 mm Hg), 22.5 mm Hg (19.8-25.3 mm Hg), and 23.8 mm Hg (21.5-26.3 mm Hg), respectively (P < 0.001 versus reverse Trendelenburg; dagger P < 0.001 versus horizontal). The reverse Trendelenburg position ameliorated the increase in IOP caused by the prone position. Furthermore, the reverse Trendelenburg position decreased the number of grossly abnormal IOP values (>23 mm Hg) by 50% and 75% compared with the prone horizontal and Trendelenburg positions, respectively. The prone positioning setups did not differ in their effect on IOP. The increase in IOP caused by prone positioning was ameliorated by the reverse Trendelenburg position and was aggravated by the Trendelenburg position. The short time period between changes in position and changes in IOP suggests an important role for ocular venous pressures in determining IOP. Therefore, IOP can be beneficially manipulated by operating table inclination in the prone position.