Barbara McCrum

Initial bispectral index may identify patients who will awaken during therapeutic hypothermia after cardiac arrest: A retrospective pilot study ☆

AIM Patients sustain a range of neurologic injuries after cardiac arrest, and determining which patients should be treated with therapeutic hypothermia (TH) is complex, often confounded by sedation and neuromuscular blockade (NMB). We evaluated bispectral index (BIS) monitoring as a tool to identify adult patients that awakened during therapeutic hypothermia. METHODS Review of prospectively collected registry data, with retrospective chart review of patient descriptions during hypothermia. Data are presented as median (interquartile range). RESULTS 7 of 309 patients (2.2%) treated with TH over 6 years awoke (followed commands) prior to completing hypothermia. Median age was 58 (54-66) years; 71% were male, cardiac arrest was witnessed in 6 (86%) and out-of-hospital in 6 (86%), and 4 patients (57%) were transferred from another hospital. 5 patients (71%) had an initial rhythm of ventricular tachycardia or fibrillation, time to return of spontaneous circulation was 17 (12-23)min. The BIS value after first NMB dose during TH was 63, 45, 43, 52, 62, 54, and 42 (median 52, IQR 44-58, 95% confidence interval 46-58). The median BIS value in the remaining data set (n=302) was 18 (6-36), p<0.001, and only 6% of BIS1 values were >46. CONCLUSION Patients who awakened early had higher BIS values after the first dose of NMB. Processed EEG values after cardiac arrest may provide additional information that could assist with determining best treatment.

Association of the Bedside Shivering Assessment Scale and derived EMG power during therapeutic hypothermia in survivors of cardiac arrest

INTRODUCTION Shivering during therapeutic hypothermia (TH) after cardiac arrest (CA) is common, but the optimal means of detection and appropriate threshold for treatment are not established. In an effort to develop a quantitative, continuous tool to measure shivering, we hypothesized that continuous derived electromyography (dEMG) power detected by the Aspect A2000 or VISTA monitor would correlate with the intermittent Bedside Shivering Assessment Scale (BSAS) performed by nurses. METHODS Among 38 patients treated with TH after CA, 853 hourly BSAS measurements were compared to dEMG power measured every minute by a frontal surface electrode. Patients received intermittent vecuronium by protocol to treat clinically recognized shivering (BSAS>0). Mean dEMG power in decibels (dB) was determined for the hour preceding each BSAS measurement. dEMG and BSAS were compared using ANOVA. RESULTS The median dEMG power for a BSAS score of 0 (no shivering) was 27 dB (IQR 26-31 dB), BSAS 1 was 30.5 dB (IQR 28-35 dB), BSAS 2 was 34 dB (IQR 30-38 dB), and BSAS 3 was 34.5 dB (IQR 32-44.25). The dEMG for BSAS≥1 (shivering) was statistically different from BSAS 0 (p<0.0001). dEMG and BSAS correlated moderately (r=0.66, p<0.001). CONCLUSION dEMG power measured from the forehead with the Aspect A2000 or VISTA monitor during therapeutic hypothermia correlated with the Bedside Shivering Assessment Scale. Given its continuous trending of dEMG power, the A2000 or VISTA may be a useful research and clinical tool for objectively monitoring shivering.

Feasibility of bispectral index monitoring to guide early post-resuscitation cardiac arrest triage ☆ ☆☆

INTRODUCTION Triage after resuscitation from cardiac arrest is hindered by reliable early estimation of brain injury. We evaluated the performance of a triage model based on early bispectral index (BIS) findings and cardiac risk classes. METHODS Retrospective evaluation of serial patients resuscitated from cardiac arrest, unable to follow commands, and undergoing hypothermia. Patients were assigned to a cardiac risk group: STEMI, VT/VF shock, VT/VF no shock, or PEA/asystole, and to a neurological dysfunction group, based on the BIS score following first neuromuscular blockade (BISi), and classified as BISi>20, BISi 10-20, or BISi<10. Cause of death was described as neurological or circulatory. RESULTS BISi in 171 patients was measured at 267(±177)min after resuscitation and 35(±1.7)°C. BISi<10 suffered 82% neurological-cause and 91% overall mortality, BISi 10-20 35% neurological and 55% overall mortality, and BISi>20 12% neurological and 36% overall mortality. 33 patients presented with STEMI, 15 VT/VF-shock, 41 VT/VF-no shock, and 80 PEA/asystole. Among BISi>20 patients, 75% with STEMI underwent urgent cardiac catheterization (cath) and 94% had good outcome. When BISi>20 with VT/VF and shock, urgent cath was infrequent (33%), and 4 deaths (44%) were uniformly of circulatory etiology. Of 56 VT/VF patients without STEMI, 24 were BISi>20 but did not undergo urgent cath - 5(20.8%) of these had circulatory-etiology death. Circulatory-etiology death also occurred in 26.5% BIS>20 patients with PEA/asystole. When BISi<10, a neurological etiology death dominated independent of cardiac risk group. CONCLUSIONS Neurocardiac triage based on very early processed EEG (BIS) is feasible, and may identify patients appropriate for individualized post-resuscitation care. This and other triage models warrant further study.

Inadequacy of Headache Management After Subarachnoid Hemorrhage

BACKGROUND Headache profoundly affects management of spontaneous subarachnoid hemorrhage but is poorly characterized. OBJECTIVE To characterize headache after spontaneous subarachnoid hemorrhage. METHODS Medical records of patients with Hunt and Hess grades I-III subarachnoid hemorrhage admitted from 2011 to 2013 were reviewed. Demographics, clinical and radiographic features, medications, and pain scores were recorded through day 14 after hemorrhage. Headache pain was characterized on the basis of a numeric rating scale and analgesic use. Severe headache was defined as 2 or more days with maximum pain scores of 8 or greater or need for 3 or more different analgesics for 2 or more days. Univariate and multivariable models were used to analyze factors associated with severe headache. RESULTS Of the 77 patients in the sample, 57% were women; median age was 57 years. Severe headache (73% overall) was associated nonlinearly with Hunt and Hess grade: grade I, 58%; grade II, 88%; and grade III, 56% (P = .01), and with Hijdra score: score 0-10, 56%; score 11-20, 86%; score 21-30, 76% (P = .03). By univariate analysis, patients with low Hijdra scores were less likely to have severe headache (27% vs 57%; P = .02). In a multivariable model, younger age and higher Hijdra score tended to be associated with severe headache. CONCLUSIONS Headache after spontaneous subarachnoid hemorrhage was often severe, necessitating multiple opioid and nonopioid analgesics. Many patients reported persistent headache and inadequate pain control.

Continuous surface EMG power reflects the metabolic cost of shivering during targeted temperature management after cardiac arrest

AIM Shivering may interfere with targeted temperature management (TTM) after cardiac arrest, contributing to secondary brain injury. Early identification of shivering is challenging with existing tools. We hypothesized that shivering detected by continuous surface sEMG monitoring would be validated with calorimetry and detected earlier than by intermittent clinical observation. METHODS This prospective observational study enrolled a convenience sample of comatose adult cardiac arrest patients treated with TTM at 33 °C. Clinical shivering was monitored hourly using the Bedside Shivering Assessment Scale (BSAS) by bedside nurses who administered intermittent neuromuscular blockade (NMB) when BSAS ≥ 1. The research team monitored independently for shivering with BSAS every 15 min during continuous blinded monitoring of oxygen consumption (VO2) via indirect calorimetry and sEMG power during the maintenance phase of TTM. A sustained 20% increase in the 5-min rolling average of VO2 above baseline identified the Gold Standard shivering threshold (VO2-20). RESULTS Among 18 patients, clinical shivering was detected 23 times in 14 patients. Hierarchical models to predict a shiver event determined by the VO2-20 for sEMG power and BSAS revealed an AUC for sEMG power of 0.92 (95%CI = 0.88-0.95), and 0.90 (CI = 0.87-0.94) for BSAS. The optimal threshold of sEMG to predict VO2-20 was 32 decibels (dB), and this was exceeded 38 (29-56) min before nurse-detected shivering. CONCLUSIONS Shivering was detected by sEMG power earlier than by clinical assessment with BSAS, with similar accuracy compared to the indirect calorimetry gold standard. Continuous sEMG monitoring appears useful for clinical assessment and research for shivering during TTM.