Stellate ganglion block used to treat reversible cerebral vasoconstriction syndrome.

BACKGROUND: We present a case report of a patient who developed severe reversible cerebral vasoconstriction syndrome, which was worsening despite typical interventional and supportive care. We administered a stellate ganglion block (SGB) and monitored the vasospasm with transcranial Doppler measurements. CASE REPORT: A 25-year-old woman was admitted with recurrent headaches and neurological symptoms, which angiography showed to be caused by diffuse, multifocal, segmental narrowing of the cerebral arteries leading to severe ischemia in multiple regions. Typical treatment was initiated with arterial verapamil followed by supportive critical care, including nimodipine, intravenous fluids, permissive hypertension, and analgesia. Vasospasm was monitored daily via transcranial Doppler ultrasound (TCD). After symptoms and monitoring suggested worsening vasospasm, an SGB was administered under ultrasound guidance. Block success was confirmed via pupillometry, and repeat TCD showed improved flow through the cerebral vasculature. Improvement in vascular flow was accompanied by a gradual reduction in acute neurological symptoms, with the patient reporting no headaches the following morning. CONCLUSIONS: For patients with reversible cerebral vasoconstriction syndrome who develop severe signs or symptoms despite typical treatment, sympathetic blockade may be a possible rescue therapy. This may extend to other causes of severe vasospasm as well, and further study is needed to determine if the SGB should be included in routine or rescue therapy.

Population Dynamics and Long-Term Trajectory of Dendritic Spines.

Structural plasticity, characterized by the formation and elimination of synapses, plays a big role in learning and long-term memory formation in the brain. The majority of the synapses in the neocortex occur between the axonal boutons and dendritic spines. Therefore, understanding the dynamics of the dendritic spine growth and elimination can provide key insights to the mechanisms of structural plasticity. In addition to learning and memory formation, the connectivity of neural networks affects cognition, perception, and behavior. Unsurprisingly, psychiatric and neurological disorders such as schizophrenia and autism are accompanied by pathological alterations in spine morphology and synapse numbers. Hence, it is vital to develop a model to understand the mechanisms governing dendritic spine dynamics throughout the lifetime. Here, we applied the density dependent Ricker population model to investigate the feasibility of ecological population concepts and mathematical foundations in spine dynamics. The model includes "immigration," which is based on the filopodia type transient spines, and we show how this effect can potentially stabilize the spine population theoretically. For the long-term dynamics we employed a time dependent carrying capacity based on the brain's metabolic energy allocation. The results show that the mathematical model can explain the spine density fluctuations in the short-term and also account for the long term trends in the developing brain during synaptogenesis and pruning.

Intravenous lipid emulsion for the treatment of drug toxicity.

Intravenous lipid emulsion (ILE) has emerged as a powerful antidote for the treatment of drug toxicity in the past decade. Initial efficacy of ILE was shown in the setting of local anesthetic systemic toxicity (LAST), but recent case reports suggest its consideration in a variety of other drug toxicities. In this review, we will summarize the experimental evidence as well as the clinical experience in using ILE as an antidote. Specifically, we will look at the evidence for using ILE in LAST as well as toxicity due to beta-blockers, calcium-channel blockers, and tricyclic antidepressants. We will also review the current dosing recommendations as well as potential side effects of ILE as an antidote.

Signal persistence of bispectral index and state entropy during surgical procedure under sedation.

INTRODUCTION: Bispectral index (BIS) and state entropy (SE) are prone to artifacts, especially due to electrocautery (EC). We compared the incidence of artifacts in BIS and SE during surgery under local anesthesia and sedation. METHODS: 28 females undergoing breast surgery under local anesthesia and sedation were studied. Simultaneous BIS and SE measurements were recorded every 10 seconds. Artifact was defined as a failure of the device to display a numerical value while the electrodes remained appropriately attached to the patient's forehead. Ratio of artifact to good signal was compared between BIS and SE in the presence or absence of EC use. RESULTS: 7679 data points were collected from 28 patients. Overall, artifact incidence was similar in BIS and SE (6.2% and 6.3%, resp.). In the presence of EC (1370 data points), BIS had significantly more artifact compared to SE (18.6% versus 6.4%, P < 0.0001). Without EC (6309 data points), BIS had significantly less artifact compared to SE (4.1% versus 7.3%, P < 0.0001). DISCUSSION: BIS and SE were comparable for incidence of artifacts in patients under sedation. Use of EC lead to more artifact in BIS than SE. Conversely, BIS had fewer artifacts than SE when there was no EC use.

Does nitrous oxide affect bispectral index and state entropy when added to a propofol versus sevoflurane anesthetic?

BACKGROUND: In earlier studies, nitrous oxide (N2O) did not affect bispectral index (BIS) or state entropy (SE) when administered as the sole anesthetic agent. We investigated the effect of adding N2O to sevoflurane or propofol anesthesia on BIS and SE. METHODS: A total of 28 patients were randomized to receive general anesthesia using either 2% sevoflurane or 120 mcg/kg/min propofol during surgery. After 20 minutes of stable anesthetic and surgical conditions (baseline), 60% N2O was added for 20 minutes. Another 20 minutes was allowed for washout after N2O was discontinued. Sevoflurane concentration was closely monitored using the standard end-tidal gas analysis and vaporizer output was constantly adjusted to offset the second-gas effect caused by the addition and discontinuation of N2O. Mean values for BIS and SE were calculated for the last 5 minutes of the baseline, nitrous oxide, and washout periods. RESULTS: In the propofol group, BIS and SE values in baseline versus N2O periods were 40±10 versus 39±10 and 43±11 versus 43±12, respectively (mean±SD, P>0.05). In the sevoflurane group, addition of N2O decreased both BIS (36±7 to 32±7, P<0.001) and SE (37±10 to 31±11, P=0.001). The magnitude of change from the baseline in BIS and SE in the sevoflurane group was 3.6±3.8 (95% CI: 0.8-6.5) and 6.1±5.5 (95% CI: 3.7-8.6), respectively. Average baseline and washout values of BIS and SE were not different in both groups (P>0.05). CONCLUSIONS: N2O decreased both BIS and SE when added to sevoflurane, but not propofol. The observed changes in the sevoflurane group were not clinically significant. Decreases in BIS and SE in the sevoflurane group could result from a true additive effect and second-gas effect of N2O that was unaccounted for despite a meticulous titration of sevoflurane using end-tidal gas monitoring.

Same-patient reproducibility of state entropy: a comparison of simultaneous bilateral measurements during general anesthesia.

BACKGROUND: State Entropy (SE) is an index of anesthetic depth similar to Bispectral Index (BIS). Both indices use a single-channel electroencephalogram, recorded from a unilaterally applied electrode on the forehead, as their input. Intrapatient reproducibility of BIS was questioned in a recent study in which simultaneous measurements from two electrodes applied to the same patient showed conflicting anesthetic depths. Our purpose was to determine whether SE results are similarly reproducible, even though their computation uses a different algorithm than BIS. In this study, we investigated the reproducibility of SE measurements simultaneously obtained from bilaterally applied electrodes in the same patient. METHODS: Entropy electrodes were applied bilaterally on 21 patients under general inhaled anesthesia. Simultaneous SE measurements from both electrodes were recorded every 10 s from each patient. Data were analyzed with Bland-Altman statistics. RESULTS: We obtained 14,379 pairs of SE measurements. Four percent of the individual measurements suggested conflicting anesthetic depth along with a numeric difference more than 10 points. Bias was not clinically significant (-0.3). Ninety-five percent limits of agreement were -11.7 and +11.6. CONCLUSIONS: SE showed a clinically significant degree of disagreement when probes were applied on both sides of the forehead in the same patient. Bland-Altman statistics showed better same-patient reproducibility in SE than did a similar study on BIS. Nevertheless, 4% of the simultaneously measured pairs of SE suggested different anesthetic depths and differed by more than 10 points. Caution is advised when using SE as a clinical index of anesthetic depth.

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.

Neuroprotective action of halogenated derivatives of L-phenylalanine.

BACKGROUND AND PURPOSE: The aromatic amino acid L-Phenylalanine (L-Phe) significantly and reversibly depresses excitatory glutamatergic synaptic transmission (GST) via a unique set of presynaptic and postsynaptic mechanisms. Therefore, we hypothesized that endogenous derivatives of L-Phe, which display potent antiglutamatergic activity, may safely and efficaciously protect the brain during conditions characterized by overactivation of glutamate receptors. METHODS: We tested this hypothesis in vitro with a combination of patch-clamp and lactate dehydrogenase (LDH) analyses in rat cultured neurons exposed to simulated ischemia, and in vivo using a rat model of experimental stroke caused by transient middle cerebral artery occlusion (MCAO). RESULTS: 3,5-diiodo-L-tyrosine (DIT) and 3,5-dibromo-L-tyrosine (DBrT), endogenous halogenated derivatives of L-Phe, attenuated GST by similar mechanisms as L-Phe, but with greater potency. For example, the IC50s for DIT and DBrT to depress the frequency of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainate receptor-mediated mEPSCs were 104.6+/-14.1 micromol/L and 127.5+/-13.3 micromol/L, respectively. Depression of GST by DIT and DBrT persisted during energy deprivation. Furthermore, DBrT significantly reduced LDH release in neuronal cultures exposed to oxygen glucose deprivation. In rats subjected to transient MCAO, DBrT decreased the brain infarct volume and neurological deficit score to 52.7+/-14.1% and 57.1+/-12.0% of control values, respectively. DBrT neither altered atrioventricular nodal and intraventricular conduction in isolated heart, nor heart rate and blood pressure in vivo. CONCLUSIONS: DBrT, an endogenous halogenated derivative of L-Phe, shows promise as a representative of a novel class of neuroprotective agents by exerting significant neuroprotection in both in vitro and in vivo models of brain ischemia.

The presence of working memory without explicit recall in a critically ill patient.

UNLABELLED: We describe an intubated patient sedated with propofol who interacted with caregivers, demonstrating intact "working memory." When neuromuscular blockade and bispectral index (BIS) monitoring were instituted, a greatly reduced amount of sedative achieved BIS values less than 60. Neither the sedation that allowed working memory nor the lighter sedation that produced BIS values less than 60 resulted in recall. This experience suggests that working memory demonstrated when BIS values are less than 60 is unlikely to lead to recall. IMPLICATIONS: The presence of intact working memory during sedation is a poor predictor of explicit recall when bispectral index values are maintained less than 60.