Hierarchical Cluster Analysis Identifies Distinct Physiological States After Acute Brain Injury.

BACKGROUND: Analysis of intracranial multimodality monitoring data is challenging, and quantitative methods may help identify unique physiological signatures that inform therapeutic strategies and outcome prediction. The aim of this study was to test the hypothesis that data-driven approaches can identify distinct physiological states from intracranial multimodality monitoring data. METHODS: This was a single-center retrospective observational study of patients with either severe traumatic brain injury or high-grade subarachnoid hemorrhage who underwent invasive multimodality neuromonitoring. We used hierarchical cluster analysis to group hourly values for heart rate, mean arterial pressure, intracranial pressure, brain tissue oxygen, and cerebral microdialysis across all included patients into distinct groups. Average values for measured physiological variables were compared across the identified clusters, and physiological profiles from identified clusters were mapped onto physiological states known to occur after acute brain injury. The distribution of clusters was compared between patients with favorable outcome (discharged to home or acute rehab) and unfavorable outcome (in-hospital death or discharged to chronic nursing facility). RESULTS: A total of 1704 observations from 20 patients were included. Even though the difference in mean values for measured variables between patients with favorable and unfavorable outcome were small, we identified four distinct clusters within our data: (1) events with low brain tissue oxygen and high lactate-to-pyruvate ratio-values (consistent with cerebral ischemia), (2) events with higher intracranial pressure values without evidence for ischemia (3) events which appeared to be physiologically "normal," and (4) events with high cerebral lactate without brain hypoxia (consistent with cerebral hyperglycolysis). Patients with a favorable outcome had a greater proportion of cluster 3 (normal) events, whereas patients with an unfavorable outcome had a greater proportion of cluster 1 (ischemia) and cluster 4 (hyperglycolysis) events (p < 0.0001, Fisher-Freeman-Halton test). CONCLUSIONS: A data-driven approach can identify distinct groupings from invasive multimodality neuromonitoring data that may have implications for therapeutic strategies and outcome predictions. These groupings could be used as classifiers to train machine learning models that can aid in the treatment of patients with acute brain injury. Further work is needed to replicate the findings of this exploratory study in larger data sets.

Medical management of compromised brain oxygen in patients with severe traumatic brain injury.

BACKGROUND: Brain tissue oxygen (PbtO(2)) monitoring is used in severe traumatic brain injury (TBI) patients. How brain reduced PbtO(2) should be treated and its response to treatment is not clearly defined. We examined which medical therapies restore normal PbtO(2) in TBI patients. METHODS: Forty-nine (mean age 40 ± 19 years) patients with severe TBI (Glasgow Coma Scale [GCS] ≤ 8) admitted to a University-affiliated, Level I trauma center who had at least one episode of compromised brain oxygen (PbtO(2) <25 mmHg for >10 min), were retrospectively identified from a prospective observational cohort study. Intracranial pressure (ICP), cerebral perfusion pressure (CPP), and PbtO(2) were monitored continuously. Episodes of compromised PbtO(2) and brain hypoxia (PbtO(2) <15 mmHg for >10 min) and the medical interventions that improved PbtO(2) were identified. RESULTS: Five hundred and sixty-four episodes of compromised PbtO2 were identified from 260 days of PbtO2 monitoring. Medical management used in a "cause-directed" manner successfully reversed 72% of the episodes of compromised PbtO(2), defined as restoration of a "normal" PbtO(2) (i.e. ≥ 25 mmHg). Ventilator manipulation, CPP augmentation, and sedation were the most frequent interventions. Increasing FiO(2) restored PbtO(2) 80% of the time. CPP augmentation and sedation were effective in 73 and 66% of episodes of compromised brain oxygen, respectively. ICP reduction using mannitol was effective in 73% of treated episodes, though was used only when PbtO(2) was compromised in the setting of elevated ICP. Successful medical treatment of brain hypoxia was associated with decreased mortality. Survivors (n = 38) had a 71% rate of response to treatment and non-survivors (n = 11) had a 44% rate of response (P = 0.01). CONCLUSION: Reduced PbtO(2) may occur in TBI patients despite efforts to maintain CPP. Medical interventions other than those to treat ICP and CPP can improve PbtO(2). This may increase the number of therapies for severe TBI in the ICU.

The use of a portable head CT scanner in the intensive care unit.

Transport of critically ill intensive care unit (ICU) patients may be hazardous. In this study, we examined the use of a portable head CT scanner (CereTom) in the ICU to assess its feasibility, safety, and radiological quality. Two hundred and twenty-five portable head CT scans were obtained from 114 patients (mean age = 57 +/- 18 years) treated in a neurosurgical intensive care unit at a university-based Level I trauma center. Patient radiological and ICU records were retrospectively reviewed. The vast majority of portable CT scans were performed after an intracranial procedure (24%) due to neurological deterioration (16%) or in routine follow-up (16%). Diagnostic quality was judged to be adequate, and no scans needed to be repeated because of poor quality. No scans were complicated by accidental disconnection of an intravenous line. In ventilated patients, there were no interruptions in mechanical ventilation and no inadvertent extubations. In addition, continuous intracranial monitoring, when in use, remained connected. The average total time to perform a portable head CT scan was 19.5 +/- 3.5 min. The actual scan time was 2.5 +/- 0.7 min. These results suggest that the portable CT scanner (CereTom) is feasible, easy to use, and safe and provides adequate radiological quality for diagnostic decisions.

Red blood cell transfusion is associated with infection and extracerebral complications after subarachnoid hemorrhage.

OBJECTIVE: Red blood cell transfusion (RBCT) is associated with medical complications in general medical and surgical patients. We examined the hypothesis that RBCT during intensive care unit (ICU) care is associated with medical complications after subarachnoid hemorrhage (SAH). METHODS: We retrospectively analyzed a prospective observational database containing 421 patients with SAH (mean age, 51.5 years; standard deviation, 14.6 years). Logistic regression models were used to adjust for age, admission hemoglobin (Hgb), clinical grade, average ICU Hgb, and symptomatic vasospasm. RESULTS: Two hundred fourteen patients received an RBCT during their ICU stay. Medical complications were identified in 156 patients and were more common in those who received blood (46%) than in those who did not (29.8%) (P < .001). Major medical complications (cardiac, pulmonary, renal, or hepatic) occurred in 111 patients, and minor complications (eg, skin rash, deep vein thrombosis) occurred in 45 patients. Any non-central nervous system infection (n = 183; P < .001), including pneumonia (n = 103; P < .001) or septicemia (n = 36; P = .02), was more common with RBCT. Central nervous system infections (meningitis, cranial wound, n = 15) also were associated with RBCT (P = .03). Mechanically ventilated patients (n = 259) were more likely to have received an RBCT than those who did not (P < .001). When logistic regression was used to control for age, admission clinical grade and Hgb, average ICU Hgb, symptomatic vasospasm, and other admission variables associated with outcome, the following factors (odds ratio; 95% confidence interval) were associated with RBCT: any medical complication (1.8; 1.1-3.0), major medical complications (2.1; 1.2-3.7), any infection (2.8; 1.7-4.5), pneumonia (2.6; 1.5-4.7), septicemia (2.9; 1.2-6.8), and need for mechanical ventilation (2.8; 1.5-5.1). CONCLUSION: These data suggest that RBCTs are associated with medical complications after SAH. However, the data do not infer causation, and further study is necessary to better define the indications for transfusion after SAH.

Accreditation and standardization of neuroanesthesia fellowship programs: results of a specialty-wide survey.

The question of accreditation and standardization of neuroanesthesia fellowship training programs in the U.S. has been discussed extensively within the field. Although numerous opinion pieces have been published, there are no data indicating the level of support or opposition for accreditation of subspecialty training among specialists in the field of neuroanesthesia. To address this gap in knowledge, a web-based survey was designed and electronically distributed to members of the Society of Neurosurgical Anesthesia and Critical Care (SNACC) that were practicing in the United States (n=339). The primary question assessed support for subspecialty accreditation. In addition, the participants were asked to rate the importance of various curricular elements for a neuroanesthesia fellowship training program. Over a 1-month period, there were 134 responses in total (40% of the sample). Ninety percent of the respondents identified themselves as having a university affiliation. Of the respondents, 64% indicated support for accreditation, 20% indicated opposition, and the remainder was equivocal. Career development, neurocritical care, and intraoperative neuromonitoring were the top 3 subjects thought to be essential to a neuroanesthesia fellowship. The majority supported a 1-year fellowship training program. These data indicate measurable support among members of SNACC for a process toward the accreditation of neuroanesthesia fellowship training programs.

Decompressive craniectomy for elevated intracranial pressure and its effect on the cumulative ischemic burden and therapeutic intensity levels after severe traumatic brain injury.

BACKGROUND: Increased intracranial pressure (ICP) can cause brain ischemia and compromised brain oxygen (PbtO2 < or = 20 mm Hg) after severe traumatic brain injury (TBI). OBJECTIVE: We examined whether decompressive craniectomy (DC) to treat elevated ICP reduces the cumulative ischemic burden (CIB) of the brain and therapeutic intensity level (TIL). METHODS: Ten severe TBI patients (mean age, 31.4 +/- 14.2 years) who had continuous PbtO2 monitoring before and after delayed DC were retrospectively identified. Patients were managed according to the guidelines for the management of severe TBI. The CIB was measured as the total time spent between a PbtO2 of 15 to 20, 10 to 15, and 0 to 10 mm Hg. The TIL was calculated every 12 hours. Mixed-effects models were used to estimate changes associated with DC. RESULTS: DC was performed on average 2.8 days after admission. DC was found to immediately reduce ICP (mean [SEM] decrease was 7.86 mm Hg [2.4 mm Hg]; P = .005). TIL, which was positively correlated with ICP (r = 0.46, P < or = .001), was reduced within 12 hours after surgery and continued to improve within the postsurgical monitoring period (P