Managing subarachnoid hemorrhage in the neurocritical care unit

Machine learning prediction of the adverse outcome for nontraumatic subarachnoid hemorrhage patients

Objective

Subarachnoid hemorrhage (SAH) is often devastating with increased early mortality, particularly in those with presumed delayed cerebral ischemia (DCI). The ability to accurately predict survival for SAH patients during the hospital course would provide valuable information for healthcare providers, patients, and families. This study aims to utilize electronic health record (EHR) data and machine learning approaches to predict the adverse outcome for nontraumatic SAH adult patients.

Methods

The cohort included nontraumatic SAH patients treated with vasopressors for presumed DCI from a large EHR database, the Cerner Health Facts^® EMR database (2000–2014). The outcome of interest was the adverse outcome, defined as death in hospital or discharged to hospice. Machine learning‐based models were developed and primarily assessed by area under the receiver operating characteristic curve (AUC).

Results

A total of 2467 nontraumatic SAH patients (64% female; median age [interquartile range]: 56 [47–66]) who were treated with vasopressors for presumed DCI were included in the study. 934 (38%) patients died or were discharged to hospice. The model achieved an AUC of 0.88 (95% CI, 0.84–0.92) with only the initial 24 h EHR data, and 0.94 (95% CI, 0.92–0.96) after the next 24 h.

Interpretation

EHR data and machine learning models can accurately predict the risk of the adverse outcome for critically ill nontraumatic SAH patients. It is possible to use EHR data and machine learning techniques to help with clinical decision‐making.

Role of Diffusion-weighted Imaging in Detecting Early Ischemic Brain Injury Following Aneurysmal Subarachnoid Hemorrhage

Background:

Aneurysmal SAH is the significant cause of morbidity and mortality in stroke patients. Early brain injury and delayed cerebral ischemia are the two main responsible pathophysiologic processes. Cerebral ischemia needs to be detected early so that early aggressive therapy could be started. Although Diffusion weighted imaging (DWI) has often been utilized for the measurement of acute ischemic strokes, its role in the detection of early cerebral ischemia due to aneurysmal subarachnoid hemorrhage has not been extensively investigated. This study is being carried out to describe the role of DWI in detecting early ischemic brain injury and outcome after aneurysmal SAH.

Aim:

Efficacy of DWI in detecting ischemic injury and predicting outcome after aneurysmal SAH.

Material and Methods:

In this prospective study 44 consecutive patients who had aneurysmal SAH; admitted within 7 days of their ictus were included. Hunt and Hess grade on admission and modified Fisher grade of SAH were noted. Plain CT brain and MR DWI was done on day before surgery. Diffusion restriction on DWI was correlated with postoperative neurological deficit, postoperative CT finding and outcome of the patient at 1 month follow-up.

Results:

DWI revealed restricted diffusion in 12 patients, out of which 1 patient was having infarction in preoperative CT scan, 6 patients were having postoperative deficit in the form of disorientation, hemiparesis and aphasia, and all patients were having infarction in postoperative CT scan. When DWI findings were compared on the basis of postoperative neurological deficit, postoperative CT finding and modified Rankin outcome score at 1month follow-up, results were statistically significant.

Conclusion:

DWI shows cerebral ischemia much earlier than CT scan in cases of aneurysmal SAH. It has significant correlation with postoperative neurological status and outcome of the patient.

Baroreflex sensitivity and heart rate variability are predictors of mortality in patients with aneurysmal subarachnoid haemorrhage

OBJECT

We aimed to investigate the link between the autonomic nervous system (ANS) impairment, assessed using baroreflex sensitivity (BRS) and heart rate variability (HRV) indices, and mortality after aneurysmal subarachnoid haemorrhage (aSAH).

METHODS

A total of 57 patients (56 ± 18 years) diagnosed with aSAH were retrospectively enrolled in the study, where 25% of patients died in the hospital. BRS was calculated using a modified cross-correlation method. Time- and frequency-domain HRV indices were calculated from a time-series of systolic peak intervals of arterial blood pressure signals. Additionally, cerebral autoregulation (CA) was assessed using the mean velocity index (Mxa), where Mxa > 0 indicates impaired CA.

RESULTS

Both BRS and HRV indices were lower in non-survivors than in survivors. The patients with disturbed BRS and HRV had more extensive haemorrhage in the H-H scale (p = .040) and were more likely to die (p = .013) when compared to patients with the intact ANS. The logistic regression model for mortality included: the APACHE II score (p = .002; OR 0.794) and the normalised high frequency power of the HRV (p < <.001; OR 0.636). A positive relationship was found between the Mxa and BRS (R = 0.48, p = .003), which suggests that increasing BRS is moderately strongly associated with worsening CA.

CONCLUSION

Our results indicated that lower values of HRV indices and BRS correlate with mortality and that there is a link between cerebral dysautoregulation and the analysed estimates of the ANS in aSAH patients.

Parameter Optimization for Selected Correlation Analysis of Intracranial Pathophysiology

Recently we proposed a mathematical tool set, called selected correlation analysis, that reliably detects positive and negative correlations between arterial blood pressure (ABP) and intracranial pressure (ICP). Such correlations are associated with severe impairment of the cerebral autoregulation and intracranial compliance, as predicted by a mathematical model. The time resolved selected correlation analysis is based on a windowing technique combined with Fourier-based coherence calculations and therefore depends on several parameters. For real time application of this method at an ICU it is inevitable to adjust this mathematical tool for high sensitivity and distinct reliability. In this study, we will introduce a method to optimize the parameters of the selected correlation analysis by correlating an index, called selected correlation positive (SCP), with the outcome of the patients represented by the Glasgow Outcome Scale (GOS). For that purpose, the data of twenty-five patients were used to calculate the SCP value for each patient and multitude of feasible parameter sets of the selected correlation analysis. It could be shown that an optimized set of parameters is able to improve the sensitivity of the method by a factor greater than four in comparison to our first analyses.

The utility of serum procalcitonin in distinguishing systemic inflammatory response syndrome from infection after aneurysmal subarachnoid hemorrhage

BACKGROUND

Systemic inflammatory response syndrome (SIRS) occurs frequently after aneurysmal subarachnoid hemorrhage (aSAH). It is a clinical challenge to distinguish between SIRS and incipient infection. Procalcitonin (PCT) has been studied among general critical care patients as a biomarker for infection. We hypothesized that PCT could be useful to distinguish SIRS from sepsis in aSAH patients.

METHODS

Prospective, observational study conducted in the multidisciplinary intensive care unit at Mayo Clinic, Jacksonville, FL between August 2009 and September 2010. Main predictor was serum PCT obtained on admission and with subsequent episodes of SIRS. A level of 0.2 ng/mL or higher was considered as elevated PCT. Main outcome was clinical infection, which was subsequently subcategorized into major (systemic) and minor (localized) infections in the sensitivity analysis.

RESULTS

Forty consecutive patients were enrolled. Majority (88 %) developed SIRS during the hospitalization. Infection developed in 16 (40 %) patients, with 6 patients meeting criteria for major infection. Overall, PCT was found to be highly specific for all infections and the subcategory of major infections (97 and 93 %, respectively) with related high negative predictive values. Odds ratio for elevated PCT with clinical infections ranged from 25.2 (95 % CI 2.7-233) to 33.3 (95 % CI 4.3-261) for all and major infections, respectively. Related receiver operating characteristic curves for elevated PCT were 0.74 and 0.96 for all and major infections, respectively.

CONCLUSIONS

Procalcitonin of 0.2 ng/mL or greater was demonstrated to be very specific for sepsis among patients with aSAH. Further studies should validate this result and establish its clinical applicability.