Mypinder S. Sekhon

Association of hemoglobin concentration and mortality in critically ill patients with severe traumatic brain injury

IntroductionThe critical care management of traumatic brain injury focuses on preventing secondary ischemic injury. Cerebral oxygen delivery is dependent upon the cerebral perfusion pressure and the oxygen content of blood, which is principally determined by hemoglobin. Despite its importance to the cerebral oxygen delivery, the precise hemoglobin concentration to provide adequate oxygen delivery to injured neuronal tissue in TBI patients is controversial with limited evidence to provide transfusion thresholds.MethodsWe conducted a retrospective cohort study of severe TBI patients, investigating the association between mean 7-day hemoglobin concentration and hospital mortality. Demographic, physiologic, intensive care interventions, clinical outcomes and daily hemoglobin concentrations were recorded for all patients. Patients were all cared for at a tertiary, level 1 trauma center in a mixed medical and surgical intensive unit. Patients were divided into quartiles based on their mean 7-day hemoglobin concentration: < 90 g/L, 90 - 99 g/L, 100 - 109 g/L and > 110 g/L. Multivariable log-binomial regression was used to model the association between mean daily hemoglobin concentration and hospital mortality.ResultsTwo hundred seventy-three patients with traumatic brain injury were identified and 169 were included in the analysis based on inclusion/exclusion criteria. Of these, 77% of the patients were male, with a mean age of 38 (SD 17) years and a median best GCS of 6 (IQR 5 - 7). One hundred fifteen patients (68%) received a red blood cell (RBC) transfusion. In RBCs administered in the ICU, the median pre-transfusion hemoglobin was 79 g/L (IQR 73 - 85). Thirty-seven patients (22%) died in hospital. Multivariable analysis revealed that mean 7-day hemoglobin concentration < 90 g/L was independently associated with an increased risk of hospital mortality (RR 3.1, 95% CI 1.5 - 6.3, p = 0.03). Other variables associated with increased mortality on multivariable regression were insertion of external ventricular drain, age and decreased GCS. Red blood cell transfusion was not associated with mortality following multivariable adjustment.ConclusionsA mean 7-day hemoglobin concentration of < 90g/L is associated with increased hospital mortality in patients with severe traumatic brain injury.

Sixty-four-slice computed tomographic scanner to clear traumatic cervical spine injury: systematic review of the literature.

PURPOSE Cervical spine (CS) injury in blunt trauma is a prevalent and devastating complication. Clearing CS injuries in obtunded patients is fraught with challenges, and no single imaging modality or algorithm is both safe and effective. Increased time in c-spine precautions is associated with greater patient morbidity including increased ventilator associated pneumonia, delirium and ulceration. We systemically reviewed the literature to assess the effectiveness of 64-slice computed tomographic (CT) scanners in clearing traumatic CS injuries. MATERIALS AND METHODS Studies were identified using MEDLINE and Embase, the references of identified studies, international experts on CS clearance and authors of primary studies. Three reviewers independently selected and extracted data from studies that reported on both CT and MRI in traumatic CS injury. RESULTS We included five studies involving a total of 3443 patients; however, heterogeneity and lack of sample size precluded quantitative summation of the results. Qualitative assessment showed that 64-Slice CT scan, when applied within a set protocol, performed favourably in clearing injury. CONCLUSIONS Data suggests that using 64-slice CT scans on obtunded trauma patients with grossly intact motor function, in the context of a defined clearance protocol with interpretation by an experienced radiologist, may be sufficient to safely clear significant CS injury. A prospective study comparing MRI and 64-slice CT scan clearance in this population is necessary to corroborate these conclusions.

Association between blood pressure and outcomes in patients after cardiac arrest: A systematic review

OBJECTIVE Hypoxic ischaemic brain injury (HIBI) is a major cause of disability after cardiac arrest. HIBI leads to impaired cerebral autoregulation such that adequate cerebral perfusion becomes critically dependent on blood pressure. However, the optimal blood pressure after cardiac arrest remains unclear. Therefore, we conducted a systematic review to investigate the association between blood pressure and neurologic outcome patients after cardiac arrest. METHODS We systematically searched MEDLINE, EMBASE, conference abstracts and article references to identify randomized and observational studies investigating the relationship between blood pressure and neurologic outcome. We included studies that reported adjusted point estimates for the relationship between blood pressure and neurologic status in adult patients after cardiac arrest. RESULTS We included 9 studies with a total of 13,150 patients. Three studies included only patients with an out-of-hospital cardiac arrest. There was marked between-study heterogeneity with respect to blood pressure definition (MAP vs. systolic), exposure duration and modelling (dichotomous vs. continuous). All studies examined either mortality or neurological status as an outcome. Seven of nine studies demonstrated that higher blood pressure was associated with improved outcomes either by an association between higher MAP and good neurologic outcome or the presence of hypotension and increased odds of mortality. CONCLUSIONS The included studies suggest improved neurologic outcomes are associated with higher blood pressures in patients after cardiac arrest. This study highlights a need for further research to define the optimal management of blood pressure in this population.

Hypernatremia in patients with severe traumatic brain injury: a systematic review.

BackgroundHypernatremia is common following traumatic brain injury (TBI) and occurs from a variety of mechanisms, including hyperosmotic fluids, limitation of free water, or diabetes insipidus. The purpose of this systematic review was to assess the relationship between hypernatremia and mortality in patients with TBI.MethodsWe searched the following databases up to November 2012: MEDLINE, EMBASE, and CENTRAL. Using a combination of MeSH and text terms, we developed search filters for the concepts of hypernatremia and TBI and included studies that met the following criteria: (1) compared hypernatremia to normonatremia, (2) adult patients with TBI, (3) presented adjusted outcomes for mortality or complications.ResultsBibliographic and conference search yielded 1,152 citations and 11 abstracts, respectively. Sixty-five articles were selected for full-text review with 5 being included in our study. All were retrospective cohort studies totaling 5,594 (range 100–4,296) patients. There was marked between-study heterogeneity. The incidence of hypernatremia ranged between 16% and 40%. Use of hyperosmolar therapy was presented in three studies (range 14-85% of patients). Hypernatremia was associated with increased mortality across all four studies that presented this outcome. Only one study considered diabetes insipidus (DI) in their analysis where hypernatremia was associated with increased mortality in patients who did not receive DDAVP.ConclusionsAlthough hypernatremia was associated with increased mortality in the included studies, there was marked between-study heterogeneity. DI was a potential confounder in several studies. Considering these limitations, the clinical significance of hypernatremia in TBI is difficult to establish at this stage.

Adherence to guidelines for management of cerebral perfusion pressure and outcome in patients who have severe traumatic brain injury

PURPOSE The aims of this study are to assess adherence to the Brain Trauma Foundation (BTF) cerebral perfusion pressure (CPP) guidelines and to determine if adherence is associated with mortality in patients who have a severe traumatic brain injury. MATERIALS AND METHODS Retrospective cohort study of 127 patients admitted to one intensive care unit between 2006 and 2012. Adherence to BTF guidelines was measured as the time that the CPP was within 50 to 70 mm Hg divided by the total time of CPP monitoring (CPP time index). RESULTS The percentage of time that the CPP was within the recommended range was 31.6% (SD, 22.2); CPP was greater than 70 mm Hg for 63.9% (SD, 26.2) of the time and less than 50 mm Hg for 4.5% of the time (SD, 16.3). After adjustment for covariates, CPP time index (between 50 and 70 mm Hg) was not associated with hospital mortality (odds ratio [OR], 1.2; 95% confidence interval [CI], 0.98-1.6; P= .079). The time indices for CPP ≥70 and <50 mm Hg were associated with decreased (OR, 0.66; 95%CI, 0.52-0.82; P< .0001) and increased (OR, 9.9; 95% CI, 1.4-69.6; P= .021) mortality, respectively. CONCLUSION Cerebral perfusion pressure was greater than 70 mm Hg for most of the time. This level of CPP was associated with decreased hospital mortality.

Multimodal neuromonitoring for traumatic brain injury: A shift towards individualized therapy.

Multimodal neuromonitoring in the management of traumatic brain injury (TBI) enables clinicians to make individualized management decisions to prevent secondary ischemic brain injury. Traditionally, neuromonitoring in TBI patients has consisted of a combination of clinical examination, neuroimaging and intracranial pressure monitoring. Unfortunately, each of these modalities has its limitations and although pragmatic, this simplistic approach has failed to demonstrate improved outcomes, likely owing to an inability to consider the underlying heterogeneity of various injury patterns. As neurocritical care has evolved, so has our understanding of underlying disease pathophysiology and patient specific considerations. Recent additions to the multimodal neuromonitoring platform include measures of cerebrovascular autoregulation, brain tissue oxygenation, microdialysis and continuous electroencephalography. The implementation of neurocritical care teams to manage patients with advanced brain injury has led to improved outcomes. Herein, we present a narrative review of the recent advances in multimodal neuromonitoring and highlight the utility of dedicated neurocritical care.

Using the relationship between brain tissue regional saturation of oxygen and mean arterial pressure to determine the optimal mean arterial pressure in patients following cardiac arrest: A pilot proof-of-concept study☆

INTRODUCTION Prospectively assess cerebral autoregulation and optimal mean arterial pressure (MAPOPT) using the dynamic relationship between MAP and regional saturation of oxygen (rSO2) using near-infrared spectroscopy. METHODS Feasibility study of twenty patients admitted to the intensive care unit following a cardiac arrest. All patients underwent continuous rSO2 monitoring using the INVOS(®) cerebral oximeter. ICM+(®) brain monitoring software calculates the cerebral oximetry index (COx) in real-time which is a moving Pearson correlation coefficient between 30 consecutive, 10-s averaged values of MAP and correspond rSO2 signals. When rSO2 increases with increasing MAP (COx ≥0.3), cerebral autoregulation is dysfunctional. Conversely, when rSO2 remains constant or decreases with increasing MAP (COx <0.3), autoregulation is preserved. ICM+(®) fits a U-shaped curve through the COx values plotted vs. MAP. The MAPOPT is nadir of this curve. RESULTS The median age was 59 years (IQR 54-67) and 7 of 20 were female. The cardiac arrest was caused by myocardial infarction in 12 (60%) patients. Nineteen arrests were witnessed and return of spontaneous circulation occurred in a median of 15.5min (IQR 8-33). Patients underwent a median of 30h (IQR 23-46) of monitoring. COx curves and MAPOPT were generated in all patients. The mean overall MAP and MAPOPT were 76mmHg (SD 10) and 76mmHg (SD 7), respectively. MAP was outside of 5mmHg from MAPOPT in 50% (SD 15) of the time. Out of the 7672 5-min averaged COx measurements, 1182 (15%) were at 0.3 or above, indicating absence of autoregulation. Multivariable polynomial fractional regression demonstrated an increase in COx with increasing temperature (P=0.008). CONCLUSIONS We demonstrated the feasibility to determine a MAPOPT using cerebral oximetry in patients after cardiac arrest.

Extracorporeal membrane oxygenation for adult respiratory distress syndrome in trauma patients: A case series and systematic literature review.

BACKGROUND Venovenous extracorporeal membrane oxygenation (vv-ECMO) is an established salvage therapy for severe respiratory failure, and may provide an alternative form of treatment for trauma-induced adult respiratory distress syndrome (ARDS) when conventional treatments have failed. The need for systemic anticoagulation is a relative contraindication for patients with bleeding risks, especially in multitraumatic injury. METHODS We describe a case series of four trauma patients with ARDS who were managed with ECMO admitted to the neuro critical care unit at Addenbrooke’s Hospital, Cambridge (UK), from January 2000 to January 2016. We performed a systematic review of the available literature to investigate the safety and efficacy of vv-ECMO in posttraumatic ARDS, focusing on the use of different anticoagulation strategies and risk of bleeding on patients with multiple injuries. RESULTS Thirty-one patients were included. A heparin bolus was given in 16 cases. Eleven patients developed complications during treatment with ECMO with three cases of major bleeding. In all documented cases of bleeding a bolus and infusion of heparin was administered, aiming for an activated clotting time (ACT) target longer than 150 seconds. Two patients treated with heparin-free ECMO developed thromboembolic complications. Four patients died, and death was never directly or indirectly related to use of ECMO. CONCLUSION vv-ECMO can be lifesaving in respiratory failure. Our experience and our literature review suggest that vv-ECMO should be considered as a rescue treatment for the management of severe hypoxemic respiratory failure secondary to ARDS in trauma patients. For patients with a high risk of bleeding, the use of ECMO with no initial anticoagulation could be considered a valid option. For patients with a moderate risk of bleeding, use of a heparin infusion keeping an ACT target shorter than 150 seconds can be appropriate. LEVEL OF EVIDENCE Therapeutic study, level V.

Exercise‐induced quadriceps muscle fatigue in men and women: effects of arterial oxygen content and respiratory muscle work

High work of breathing and exercise‐induced arterial hypoxaemia (EIAH) can decrease O2 delivery and exacerbate exercise‐induced quadriceps fatigue in healthy men. Women have a higher work of breathing during exercise, dedicate a greater fraction of whole‐body V̇O2 towards their respiratory muscles and develop EIAH. Despite a greater reduction in mens work of breathing, the attenuation of quadriceps fatigue was similar between the sexes. The degree of EIAH was similar between sexes, and regardless of sex, those who developed the greatest hypoxaemia during exercise demonstrated the most attenuation of quadriceps fatigue. Based on our previous finding that women have a greater relative oxygen cost of breathing, women appear to be especially susceptible to work of breathing‐related changes in quadriceps muscle fatigue.

Passive heat stress reduces circulating endothelial and platelet microparticles

What is the central question of this study? Does passive heat stress of +2°C oesophageal temperature change concentrations of circulating arterial endothelial‐ and platelet‐derived microparticles in healthy adults? What is the main finding and its importance? Concentrations of circulating endothelial‐ and platelet‐derived microparticles were markedly decreased in heat stress. Reductions in circulating microparticles might indicate favourable vascular changes associated with non‐pathological hyperthermia.