Venkatakrishna Rajajee

Comparison of accuracy of optic nerve ultrasound for the detection of intracranial hypertension in the setting of acutely fluctuating vs stable intracranial pressure: post-hoc analysis of data from a prospective, blinded single center study

IntroductionOptic nerve sheath diameter (ONSD) measurement with bedside ultrasound has been shown in many studies to accurately detect high intracranial pressure (ICP). The accuracy of point-in-time ONSD measurement in the presence of ongoing fluctuation of ICP between high and normal is not known. Recent laboratory investigation suggests that reversal of optic nerve sheath distension may be impaired following bouts of intracranial hypertension. Our objective was to compare the accuracy of ONSD measurement in the setting of fluctuating versus stable ICP.MethodsThis was a retrospective analysis of data from prospective study comparing ONSD to invasive ICP. Patients with invasive ICP monitors in the ICU underwent ONSD measurement with simultaneous blinded recording of ICP from the invasive monitor. Three measurements were made in each eye. Significant acute ICP fluctuation (SAIF) was defined in two different ways; as the presence of ICP both above and below 20 mmHg within a cluster of six measurements (Definition 1) and as a magnitude of fluctuation >10 mmHg within the cluster (Definition 2). The accuracy of point-in-time ONSD measurements for the detection of concurrent ICP >20 mmHg within clusters fulfilling a specific definition of SAIF was compared to the accuracy of ONSD measurements within clusters not fulfilling the particular definition by comparison of independent receiver operating characteristic (ROC) curves.ResultsA total of 613 concurrent ONSD-ICP measurements in 109 clusters were made in 73 patients. Twenty-three (21%) clusters fulfilled SAIF Definition 1 and 17 (16%) SAIF Definition 2. For Definition 1, the difference in the area under the curve (AUC) of ROC curves for groups with and without fluctuation was 0.10 (P = 0.0001). There was a fall in the specificity from 98% (95% CI 96 to 99%) to 74% (63 to 83%) and in the positive predictive value from 89% (80 to 95%) to 76% (66 to 84%) with fluctuation. For Definition 2, also, there was a significant difference between the AUC of ROC curves of groups with fluctuation-magnitude >10 mmHg and those with fluctuation-magnitude 5 to 10 mmHg (0.06, P = 0.04) as well as <5 mmHg (0.07, P = 0.01).ConclusionsSpecificity and PPV of ONSD for ICP >20 mmHg are substantially decreased in patients demonstrating acute fluctuation of ICP between high and normal. This may be because of delayed reversal of nerve sheath distension.

Individual patient data systematic review and meta-analysis of optic nerve sheath diameter ultrasonography for detecting raised intracranial pressure: protocol of the ONSD research group

BackgroundThe purpose of the optic nerve sheath diameter (ONSD) research group project is to establish an individual patient-level database from high quality studies of ONSD ultrasonography for the detection of raised intracranial pressure (ICP), and to perform a systematic review and an individual patient data meta-analysis (IPDMA), which will provide a cutoff value to help physicians making decisions and encourage further research. Previous meta-analyses were able to assess the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP but failed to determine a precise cutoff value. Thus, the ONSD research group was founded to synthesize data from several recent studies on the subject and to provide evidence on the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP.MethodsThis IPDMA will be conducted in different phases. First, we will systematically search for eligible studies. To be eligible, studies must have compared ONSD ultrasonography to invasive intracranial devices, the current reference standard for diagnosing raised ICP. Subsequently, we will assess the quality of studies included based on the QUADAS-2 tool, and then collect and validate individual patient data. The objectives of the primary analyses will be to assess the diagnostic accuracy of ONSD ultrasonography and to determine a precise cutoff value for detecting raised ICP. Secondly, we will construct a logistic regression model to assess whether patient and study characteristics influence diagnostic accuracy.DiscussionWe believe that this IPD MA will provide the most reliable basis for the assessment of diagnostic accuracy of ONSD ultrasonography for detecting raised ICP and to provide a cutoff value. We also hope that the creation of the ONSD research group will encourage further study.Systematic review registrationPROSPERO registration number: CRD42012003072

Impact of real-time ultrasound guidance on complications of percutaneous dilatational tracheostomy: a propensity score analysis

IntroductionRecent studies have demonstrated the feasibility of real-time ultrasound guidance during percutaneous dilatational tracheostomy, including in patients with risk factors such as coagulopathy, cervical spine immobilization and morbid obesity. Use of real-time ultrasound guidance has been shown to improve the technical accuracy of percutaneous dilatational tracheostomy; however, it is unclear if there is an associated reduction in complications. Our objective was to determine whether the peri-procedural use of real-time ultrasound guidance is associated with a reduction in complications of percutaneous dilatational tracheostomy using a propensity score analysis.MethodsThis study reviewed all percutaneous dilatational tracheostomies performed in an 8-year period in a neurocritical care unit. Percutaneous dilatational tracheostomies were typically performed by trainees under guidance of the attending intensivist. Bronchoscopic guidance was used for all procedures with addition of real-time ultrasound guidance at the discretion of the attending physician. Real-time ultrasound guidance was used to guide endotracheal tube withdrawal, guide tracheal puncture, identify guidewire entry level and confirm bilateral lung sliding. The primary outcome was a composite of previously defined complications including (among others) bleeding, infection, loss of airway, inability to complete procedure, need for revision, granuloma and early dislodgement. Propensity score analysis was used to ensure that the relationship of not using real-time ultrasound guidance with the probability of an adverse outcome was examined within groups of patients having similar covariate profiles. Covariates included were age, gender, body mass index, diagnosis, Acute Physiology and Chronic Health Evaluation II score, timing of tracheostomy, positive end-expiratory pressure and presence of risk factors including coagulopathy, cervical spine immobilization and prior tracheostomy.ResultsA total of 200 patients underwent percutaneous dilatational tracheostomy during the specified period, and 107 received real-time ultrasound guidance. Risk factors for percutaneous dilatational tracheostomy were present in 63 (32%). There were nine complications in the group without real-time ultrasound guidance: bleeding (n = 4), need for revision related to inability to ventilate or dislodgement (n = 3) and symptomatic granuloma (n = 2). There was one complication in the real-time ultrasound guidance group (early dislodgement). The odds of having an adverse outcome for patients receiving real-time ultrasound guidance were significantly lower (odds ratio = 0.08; 95% confidence interval, 0.009 to 0.811; P = 0.032) than for those receiving a standard technique while holding the propensity score quartile fixed.ConclusionsThe use of real-time ultrasound guidance during percutaneous dilatational tracheostomy was associated with a significant reduction in procedure-related complications.

Low pulsatility index on transcranial Doppler predicts symptomatic large-vessel vasospasm after aneurysmal subarachnoid hemorrhage.

BACKGROUND Elevated mean cerebral blood flow velocity (mCBFV) on transcranial Doppler predicts vasospasm of the large intracranial arteries after aneurysmal subarachnoid hemorrhage (aSAH). The pulsatility index (PI) is a measure of distal vascular resistance, which may be low when there is compensatory distal vasodilatation following hypoperfusion caused by large-vessel vasospasm. OBJECTIVE To study the predictive value of low PI for symptomatic large-vessel vasospasm (SLVVS) after aSAH. METHODS Medical records of patients admitted with aSAH between January 2007 and April 2009 were reviewed. Transcranial color-coded duplex (TCCD) sonography was performed daily between days 2 and 14. Patients with unexplained acute neurological decline underwent catheter- or computed tomography-angiography. The lowest recorded PI and the highest mCBFV on TCCD were correlated to the occurrence of SLVVS, angiographic vasospasm, and delayed cerebral infraction in multivariate analysis by use of logistic regression. Functional outcome was assessed at first follow-up. RESULTS Eighty-one patients met inclusion criteria. Mean lowest PI was 0.71 + 0.19. Median highest mCBFV was 135 cm/s (interquartile range 99-194 cm/s). SLVVS was seen in 21 of 81 (26%) patients, whereas 27 of 55 (49%) patients with repeat angiography had moderate or severe angiographic vasospasm. Following multivariate analysis, only the lowest PI was an independent predictor of SLVVS (P = .03, odds ratio 0.04, 95% confidence interval 0.001-0.54), whereas only the highest mCBFV was an independent predictor of angiographic vasospasm (P = .02, odds ratio 1.01, 95% confidence interval 1.002-1.02). SLVVS was independently associated with functional outcome at follow-up. CONCLUSION Low PI on TCCD is an independent predictor of SLVVS after aSAH, whereas mCBFV is a better predictor of angiographic vasospasm.

Efficacy of antibiotic-impregnated external ventricular drains in reducing ventriculostomy-associated infections

Use of an external ventricular drain (EVD) is essential for managing patients with hydrocephalus or intracranial hypertension. While this procedure is safe and efficacious, ventriculostomy-associated infections (VAI) continue to cause significant morbidity. In this study, we evaluated the efficacy of antibiotic-coated EVD (AC-EVD) in reducing the occurrence of VAI. Between July 2007 and July 2009, 203 patients underwent placement of an EVD. A total of 145 of these patients met the inclusion criteria, with 76 patients (52.4%) receiving AC-EVD and 69 patients (47.6%) receiving uncoated EVD. Ten patients (6.9%) developed VAI, of whom three were in the AC-EVD group and seven were in the uncoated EVD group (p=0.19). The mean duration between catheter insertion and positive cerebrospinal fluid culture was significantly greater in the AC-EVD group versus the uncoated EVD group (15±4days versus 4±2days, respectively; p=0.001). In the uncoated EVD group, 17 of 69 patients (24.6%) were dead at 3years versus 12 of 76 (15.8%) patients in the AC-EVD group (p=0.21). The overall VAI rate was 6.9% with a trend toward lower infection rates in the AC-EVD group compared to the uncoated EVD group (3.9% versus 10.1%, respectively; p>0.05).

Incidence of delayed seizures, delayed cerebral ischemia and poor outcome with the use of levetiracetam versus phenytoin after aneurysmal subarachnoid hemorrhage

Current guidelines recommend against the use of phenytoin following aneurysmal subarachnoid hemorrhage (aSAH) but consider other anticonvulsants, such as levetiracetam, acceptable. Our objective was to evaluate the risk of poor functional outcomes, delayed cerebral ischemia (DCI) and delayed seizures in aSAH patients treated with levetiracetam versus phenytoin. Medical records of patients with aSAH admitted between 2005-2012 receiving anticonvulsant prophylaxis with phenytoin or levetiracetam for >72 hours were reviewed. The primary outcome measure was poor functional outcome, defined as modified Rankin Scale (mRS) score >3 at first recorded follow-up. Secondary outcomes measures included DCI and the incidence of delayed seizures. The association between the use of levetiracetam and phenytoin and the outcomes of interest was studied using logistic regression. Medical records of 564 aSAH patients were reviewed and 259 included in the analysis after application of inclusion/exclusion criteria. Phenytoin was used exclusively in 43 (17%), levetiracetam exclusively in 132 (51%) while 84 (32%) patients were switched from phenytoin to levetiracetam. Six (2%) patients had delayed seizures, 94 (36%) developed DCI and 63 (24%) had mRS score >3 at follow-up. On multivariate analysis, only modified Fisher grade and seizure before anticonvulsant administration were associated with DCI while age, Hunt-Hess grade and presence of intraparenchymal hematoma were associated with mRS score >3. Choice of anticonvulsant was not associated with any of the outcomes of interest. There was no difference in the rate of delayed seizures, DCI or poor functional outcome in patients receiving phenytoin versus levetiracetam after aSAH. The high rate of crossover from phenytoin suggests that levetiracetam may be better tolerated.

Prolonged retention of awareness during cardiopulmonary resuscitation for asystolic cardiac arrest.

ObjectiveTo describe high level of awareness in a patient undergoing cardiopulmonary resuscitation for an asystolic cardiac arrest and review the literature regarding this phenomenon.MethodsThis is a case report of a patient admitted to the Intensive Care Unit who suffered an asystolic cardiac arrest. We reviewed MEDLINE using the terms “awareness,” “consciousness,” “cerebral perfusion,” “sedation,” “analgesia,” “termination,” “cessation,” and “cardiopulmonary resuscitation.”ResultsA 57-year-old man with renal failure suffered asystolic cardiac arrest. He was awake and alert during cardiopulmonary resuscitation (CPR). Cardiac arrest was confirmed by echocardiogram and invasive arterial monitoring. He briskly localized and consistently followed simple commands while chest compressions were in progress before becoming unresponsive and dying after a 3-h resuscitative effort. No sedation/analgesia was used. There are few reports in the literature describing similar events.ConclusionIt is possible to retain a high level of awareness following cardiac arrest, particularly with effective CPR. Recognition of this situation when it occurs allows appropriate decisions to be made regarding the use of sedation and the length of resuscitative efforts.

Performance of Spectrogram-Based Seizure Identification of Adult EEGs by Critical Care Nurses and Neurophysiologists

Purpose: Continuous EEG screening using spectrograms or compressed spectral arrays (CSAs) by neurophysiologists has shorter review times with minimal loss of sensitivity for seizure detection when compared with visual analysis of raw EEG. Limited data are available on the performance characteristics of CSA-based seizure detection by neurocritical care nurses. Methods: This is a prospective cross-sectional study that was conducted in two academic neurocritical care units and involved 33 neurointensive care unit nurses and four neurophysiologists. Results: All nurses underwent a brief training session before testing. Forty two-hour CSA segments of continuous EEG were reviewed and rated for the presence of seizures. Two experienced clinical neurophysiologists masked to the CSA data performed conventional visual analysis of the raw EEG and served as the gold standard. The overall accuracy was 55.7% among nurses and 67.5% among neurophysiologists. Nurse seizure detection sensitivity was 73.8%, and the false-positive rate was 1-per-3.2 hours. Sensitivity and false-alarm rate for the neurophysiologists was 66.3% and 1-per-6.4 hours, respectively. Interrater agreement for seizure screening was fair for nurses (Gwet AC1 statistic: 43.4%) and neurophysiologists (AC1: 46.3%). Conclusions: Training nurses to perform seizure screening utilizing continuous EEG CSA displays is feasible and associated with moderate sensitivity. Nurses and neurophysiologists had comparable sensitivities, but nurses had a higher false-positive rate. Further work is needed to improve sensitivity and reduce false-alarm rates.

The Role of Neuroimaging in the Latent Period of Blunt Traumatic Cerebrovascular Injury

Introduction: Blunt cerebrovascular injury (BCVI) is found in 1-2.7% of all blunt trauma when appropriate screening criteria are employed. A significant number of patients with BCVI have a latent, or asymptomatic period, in which therapeutic intervention based on the appropriate use of angiographic imaging may decrease the risk of an ischemic stroke. Methods: Case report and review of literature. Results: A 42 year old woman suffered a fall off a motorcycle and was neurologically intact in the emergency room. Fractures involving the transverse foramen of cervical vertebrae were found on non-contrast Computed Tomography (CT) but screening for BCVI with angiographic imaging not performed. She subsequently suffered an ischemic stroke resulting in significant disability. Published studies that address the use of screening criteria for BCVI and subsequent management are reviewed. Conclusion: BCVI results in significant morbidity and mortality attributable to ischemic stroke. There is often a latent period between BCVI and occurrence of ischemic stroke. Specific risk factors can be used to identify patients requiring screening with catheter or CT angiography. Treatment with antithrombotic agents is the mainstay of treatment of BCVI and may reduce the rate of ischemic stroke. Identification and treatment of asymptomatic BCVI in blunt trauma patients may prevent ischemic stroke in a predominantly young population.

A Propensity Score Analysis of the Impact of Dexamethasone Use on Delayed Cerebral Ischemia and Poor Functional Outcomes After Subarachnoid Hemorrhage

OBJECTIVE An inflammatory response occurs after aneurysmal subarachnoid hemorrhage (aSAH) and predicts poor outcomes. Glucocorticoids suppress inflammation and promote fluid retention. Dexamethasone is often administered after aSAH for postoperative cerebral edema and refractory headache. Our objective was to examine the impact of dexamethasone use on functional outcomes and delayed cerebral ischemia (DCI) after aSAH. METHODS Patients with aSAH admitted between 2010 and 2015 were included; the data source was a single-center subarachnoid hemorrhage registry. The intervention of interest was a dexamethasone taper used <7 days from ictus. The primary outcome was poor discharge functional outcome, with a modified Rankin Scale score >3. Other outcomes included DCI and infection. A propensity score for use of dexamethasone was calculated using a logistic regression model that included potential predictors of dexamethasone use and outcome. The impact of dexamethasone on outcomes of interest was calculated and the propensity score was controlled for. RESULTS A total of 440 patients with subarachnoid hemorrhage were admitted during the study period and 309 met eligibility criteria. Dexamethasone was administered in 101 patients (33%). A total of 127 patients (41%) had a discharge modified Rankin Scale score >3, 105 (34%) developed DCI, and 94 (30%) developed an infection. After propensity score analysis, dexamethasone use was associated with a significant reduction in poor functional outcomes (odds ratio [OR], 0.35; 95% confidence interval [CI], 0.19-0.66) but showed no significant association with DCI (OR, 0.93; 95% CI, 0.53-1.64) or infection (OR, 0.60; 95% CI, 0.34-1.06). CONCLUSIONS Dexamethasone use after aSAH was associated with a reduction in poor functional outcomes at discharge but not DCI, controlling for predictors of dexamethasone use.