Fluid balance, complications, and brain tissue oxygen tension monitoring following severe traumatic brain injury

Delphi Process for Validation of Fluid Treatment Algorithm for Critically Ill Pediatric Trauma Patients

INTRODUCTION

While intravenous fluid therapy is essential to re-establishing volume status in children who have experienced trauma, aggressive resuscitation can lead to various complications. There remains a lack of consensus on whether pediatric trauma patients will benefit from a liberal or restrictive crystalloid resuscitation approach and how to optimally identify and transition between fluid phases.

METHODS

A panel was comprised of physicians with expertise in pediatric trauma, critical care, and emergency medicine. A three-round Delphi process was conducted via an online survey, with each round being followed by a live video conference. Experts agreed or disagreed with each aspect of the proposed fluid management algorithm on a five-level Likert scale. The group opinion level defined an algorithm parameter's acceptance or rejection with greater than 75% agreement resulting in acceptance and greater than 50% disagreement resulting in rejection. The remaining were discussed and re-presented in the next round.

RESULTS

Fourteen experts from five Level 1 pediatric trauma centers representing three subspecialties were included. Responses were received from 13/14 participants (93%). In round 1, 64% of the parameters were accepted, while the remaining 36% were discussed and re-presented. In round 2, 90% of the parameters were accepted. Following round 3, there was 100% acceptance by all the experts on the revised and final version of the algorithm.

CONCLUSIONS

We present a validated algorithm for intavenous fluid management in pediatric trauma patients that focuses on the de-escalation of fluids. Focusing on this time point of fluid therapy will help minimize iatrogenic complications of crystalloid fluids within this patient population.

The Impact of Invasive Brain Oxygen Pressure Guided Therapy on the Outcome of Patients with Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Traumatic brain injury (TBI) is a major public health burden, causing death and disability worldwide. Intracranial hypertension and brain hypoxia are the main mechanisms of secondary brain injury. As such, management strategies guided by intracranial pressure (ICP) and brain oxygen (PbtO₂) monitoring could improve the prognosis of these patients. Our objective was to summarize the current evidence regarding the impact of PbtO₂-guided therapy on the outcome of patients with TBI. We performed a systematic search of PubMed, Scopus, and the Cochrane library databases, following the protocol registered in PROSPERO. Only studies comparing PbtO₂/ICP-guided therapy with ICP-guided therapy were selected. Primary outcome was neurological outcome at 3 and 6 months assessed by using the Glasgow Outcome Scale; secondary outcomes included hospital and long-term mortality, burden of intracranial hypertension, and brain tissue hypoxia. Out of 6254 retrieved studies, 15 studies (n = 37,245 patients, of who 2184 received PbtO₂-guided therapy) were included in the final analysis. When compared with ICP-guided therapy, the use of combined PbO₂/ICP-guided therapy was associated with a higher probability of favorable neurological outcome (odds ratio 2.21 [95% confidence interval 1.72-2.84]) and of hospital survival (odds ratio 1.15 [95% confidence interval 1.04-1.28]). The heterogeneity (I²) of the studies in each analysis was below 40%. However, the quality of evidence was overall low to moderate. In this meta-analysis, PbtO₂-guided therapy was associated with reduced mortality and more favorable neurological outcome in patients with TBI. The low-quality evidence underlines the need for the results from ongoing phase III randomized trials.

Brain-Lung Crosstalk: Management of Concomitant Severe Acute Brain Injury and Acute Respiratory Distress Syndrome

Purpose of Review

To summarize pathophysiology, key conflicts, and therapeutic approaches in managing concomitant severe acute brain injury (SABI) and acute respiratory distress syndrome (ARDS).

Recent Findings

ARDS is common in SABI and independently associated with worse outcomes in all SABI subtypes. Most landmark ARDS trials excluded patients with SABI, and evidence to guide decisions is limited in this population. Potential areas of conflict in the management of patients with both SABI and ARDS are (1) risk of intracranial pressure (ICP) elevation with high levels of positive end-expiratory pressure (PEEP), permissive hypercapnia due to lung protective ventilation (LPV), or prone ventilation; (2) balancing a conservative fluid management strategy with ensuring adequate cerebral perfusion, particularly in patients with symptomatic vasospasm or impaired cerebrovascular blood flow; and (3) uncertainty about the benefit and harm of corticosteroids in this population, with a mortality benefit in ARDS, increased mortality shown in TBI, and conflicting data in other SABI subtypes. Also, the widely adapted partial pressure of oxygen (P_aO₂) target of > 55 mmHg for ARDS may exacerbate secondary brain injury, and recent guidelines recommend higher goals of 80–120 mmHg in SABI. Distinct pathophysiology and trajectories among different SABI subtypes need to be considered.

Summary

The management of SABI with ARDS is highly complex, and conventional ARDS management strategies may result in increased ICP and decreased cerebral perfusion. A crucial aspect of concurrent management is to recognize the risk of secondary brain injury in the individual patient, monitor with vigilance, and adjust management during critical time windows. The care of these patients requires meticulous attention to oxygenation and ventilation, hemodynamics, temperature management, and the neurological exam. LPV and prone ventilation should be utilized, and supplemented with invasive ICP monitoring if there is concern for cerebral edema and increased ICP. PEEP titration should be deliberate, involving measures of hemodynamic, pulmonary, and brain physiology. Serial volume status assessments should be performed in SABI and ARDS, and fluid management should be individualized based on measures of brain perfusion, the neurological exam, and cardiopulmonary status. More research is needed to define risks and benefits in corticosteroids in this population.

Early positive fluid balance is predictive for venous thromboembolism in critically ill surgical patients

BACKGROUND

Positive fluid balance (FB) in the intensive care unit (ICU) may be a marker for increased venous thromboembolism (VTE) risk. We hypothesized that an early positive fluid balance (FB) would be associated with increased VTE occurrence.

METHODS

A single-center retrospective review of surgical ICU patients was conducted from May 2011 to December 2014. Patients with a VTE were compared to those who did not develop a VTE (NVTE).

RESULTS

There were 619 patients analyzed with 77 (12.4%) diagnosed with a VTE; these patients had longer ventilator days (12.3 vs. 5.0 days, p < 0.01) and ICU stays (10.3 vs. 6.4 days, p < 0.01), and were more likely to have a net FB ≥ 4L over the first three days (62% vs. 44%, p < 0.01). A FB ≥ 4L over the first three ICU days was an independent predictor of VTE (AOR 1.74, p = 0.04).

CONCLUSION

Patients with an early positive FB are more likely to develop a VTE.

The Impact of IV Electrolyte Replacement on the Fluid Balance of Critically Ill Surgical Patients

Avoiding excess fluid administration is necessary when managing critically ill surgical patients. The aim of this study was to delineate the current practices of IVelectrolyte (IVE) replacement in a surgical ICU and quantify their contribution to the fluid balance (FB) status. Patients admitted to the surgical ICU over a six-month period were reviewed. Patients undergoing dialysis and those with ICU stay <72 hours were excluded. A total of 248 patients were included. The median age was 60 years, and 57 per cent were male. Overall, 1131 patient ICU days were analyzed. The median daily FB was 672 mL. IVEs were administered in 62 per cent of ICU days. In days that IVEs were used, negative FB was significantly less likely to be achieved (62% vs 69%, P = 0.02). The most commonly administered IVE was calcium (32% of ICU days); however, the largest volume of IVE was administered in the form of phosphorus (median 225 mL). Diuretics were administered in 17 per cent of ICU days. Patients who received diuretics were significantly more likely to receive IVE (70% vs 61%, P = 0.02). Administration of IVE may contribute to the daily positive FB of surgical ICU patients. Implementation of practices that can ameliorate this effect is encouraged.

Hyperchloremia, not Concomitant Hypernatremia, Independently Predicts Early Mortality in Critically Ill Moderate-Severe Traumatic Brain Injury Patients

BACKGROUND

Hypernatremia has been associated with mortality in neurocritically ill patients, with and without traumatic brain injury (TBI). These studies, however, lack concomitant adjustment for hyperchloremia as a physiologically co-occurring finding despite the associations with hyperchloremia and worse outcomes after trauma, sepsis, and intracerebral hemorrhage. The objective of our study was to examine the association of concomitant hypernatremia and hyperchloremia with in-hospital mortality in moderate-severe TBI (msTBI) patients.

METHODS

We retrospectively analyzed prospectively collected data from the OPTIMISM-study and included all msTBI patients consecutively enrolled between 11/2009 and 1/2017. Time-weighted average (TWA) sodium and chloride values were calculated for all patients to examine the unadjusted mortality rates associated with the burden of hypernatremia and hyperchloremia over the entire duration of the intensive care unit stay. Multivariable logistic regression modeling predicting in-hospital mortality adjusted for validated confounders of msTBI mortality was applied to evaluate the concomitant effects of hypernatremia and hyperchloremia. Internal bootstrap validation was performed.

RESULTS

Of the 458 patients included for analysis, 202 (44%) died during the index hospitalization. Fifty-five patients (12%) were excluded due to missing data. Unadjusted mortality rates were nearly linearly increasing for both TWA sodium and TWA chloride, and were highest for patients with a TWA sodium > 160 mmol/L (100% mortality) and TWA chloride > 125 mmol/L (94% mortality). When evaluated separately in the multivariable analysis, TWA sodium (per 10 mmol/L change: adjusted OR 4.0 [95% CI 2.1-7.5]) and TWA chloride (per 10 mmol/L change: adjusted OR 3.9 [95% CI 2.2-7.1]) independently predicted in-hospital mortality. When evaluated in combination, TWA chloride remained independently associated with in-hospital mortality (per 10 mmol/L change: adjusted OR 2.9 [95% CI 1.1-7.8]), while this association was no longer observed with TWA sodium values (per 10 mmol/L change: adjusted OR 1.5 [95% CI 0.51-4.4]).

CONCLUSIONS

When concomitantly adjusting for the burden of hyperchloremia and hypernatremia, only hyperchloremia was independently associated with in-hospital mortality in our msTBI cohort. Pending validation, our findings may provide the rationale for future studies with targeted interventions to reduce hyperchloremia and improve outcomes in msTBI patients.

Use of Hematocrit for Short-Term Prognosis of Patients with Traumatic Brain Injury After Decompressive Craniectomy

OBJECTIVE

To discuss the effects of the hematocrit (Hct) in patients with traumatic brain injury after decompressive craniectomy (DC).

METHODS

Demographic data, inspection and treatment procedures, and 30-day prognosis were obtained for 158 patients with head injury who underwent unilateral DC in our hospital between January 2013 and June 2018. Uni- and multivariate logistic regression was applied to analyze independent risk factors for 30-day outcome. The quantitative analysis of postoperative Hct, ΔHct (postoperative Hct minus initial Hct), and their combination for the prognosis of patients with TBI was displayed graphically using receiver operating characteristic (ROC) curves. Multiple linear regression was used to explore factors influencing postoperative Hct and ΔHct.

RESULTS

Short-term mortality was 29.7%. Uni- and multivariate logistic regression analysis showed that age (odds ratio [OR], 1.064; P = 0.024), Glasgow Coma Scale score (OR, 0.711; P = 0.027), Injury Severity Score (ISS) (OR, 1.156; P = 0.047), midline shift in millimeters (OR, 1.809; P <0.001), postoperative Hct (OR, 0.743; P = 0.001), and ΔHct (OR, 1.242; P =0.048) were independent risk factors for short-term death. In ROC curves, a combination of postoperative Hct and ΔHct showed the highest sensitivity (77.5%) and highest specificity (89.4%). When using this combination to predict prognosis, we could achieve an accuracy of 94.5%. ISS (β = -0.172, P = 0.022), initial Hct (β = 0.243, P = 0.001), principal hematoma location (β = -2.628, P < 0.001), hours of operation (β = -0.884, P = 0.048), and colloid quantity (β = -0.002, P = 0.001) were independent contributing factors for ΔHct, which was similar to postoperative Hct.

CONCLUSIONS

A combination of postoperative Hct and ΔHct could better predict short-term survival of patients with TBI. Developing an appropriate treatment strategy to increase postoperative Hct and reduce the ΔHct may be good for the short-term prognosis of patients with TBI after DC.

Positive fluid balance is associated with increased in-hospital mortality in patients with intracerebral hemorrhage

Objective: This study aimed to investigate the association between fluid balance (FB) and in-hospital mortality in patients with intracerebral hemorrhage (ICH).Methods: Data were extracted from the online database Multi-parameter Intelligent Monitoring in Intensive Care III. Patients were divided into two groups according to the FB status at 48 hours after intensive care unit (ICU) admission: negative and positive 48-hour FB groups. The primary outcome was in-hospital mortality.Results: Data of 1407 patients were analyzed. Linear spline function in logistic models showed significant association between the volume of positive FB and in-hospital mortality (odds ratio (OR) 1.006; 95% CI: 1.002-1.010), while the association between the volume of negative FB and in-hospital mortality was non-significant. For interpretation, FB was further divided into four quartiles. Referred to Q1, the OR of in-hospital mortality stepwise increased from Q2 (OR, 1.11; 95% CI: 0.72-1.68) to Q4 (OR, 1.68; 95% CI: 1.13-2.48). A similar association was also found between FB and Glasgow coma scale at ICU discharge.Conclusions: In patients with ICH, increased volume of positive FB was associated with higher in-hospital mortality while the volume of negative FB was not. Whether maintaining a zero FB status is a beneficial strategy needs further investigation.

Elevated plasma levels of TIMP-3 are associated with a higher risk of acute respiratory distress syndrome and death following severe isolated traumatic brain injury

Background:

Complications after injury, such as acute respiratory distress syndrome (ARDS), are common after traumatic brain injury (TBI) and associated with poor clinical outcomes. The mechanisms driving non-neurologic organ dysfunction after TBI are not well understood. Tissue inhibitor of matrix metalloproteinase-3 (TIMP-3) is a regulator of matrix metalloproteinase activity, inflammation, and vascular permeability, and hence has plausibility as a biomarker for the systemic response to TBI.

Methods:

In a retrospective study of 182 patients with severe isolated TBI, we measured TIMP-3 in plasma obtained on emergency department arrival. We used non-parametric tests and logistic regression analyses to test the association of TIMP-3 with the incidence of ARDS within 8 days of admission and in-hospital mortality.

Results:

TIMP-3 was significantly higher among subjects who developed ARDS compared with those who did not (median 2810 pg/mL vs. 2260 pg/mL, p=0.008), and significantly higher among subjects who died than among those who survived to discharge (median 2960 pg/mL vs. 2080 pg/mL, p<0.001). In an unadjusted logistic regression model, for each SD increase in plasma TIMP-3, the odds of ARDS increased significantly, OR 1.5 (95% CI 1.1 to 2.1). This association was only attenuated in multivariate models, OR 1.4 (95% CI 1.0 to 2.0). In an unadjusted logistic regression model, for each SD increase in plasma TIMP-3, the odds of death increased significantly, OR 1.7 (95% CI 1.2 to 2.3). The magnitude of this association was greater in a multivariate model adjusted for markers of injury severity, OR 1.9 (95% CI 1.2 to 2.8).

Discussion:

TIMP-3 may play an important role in the biology of the systemic response to brain injury in humans. Along with clinical and demographic data, early measurements of plasma biomarkers such as TIMP-3 may help identify patients at higher risk of ARDS and death after severe isolated TBI.

Level of evidence

III.

Aspects on the Physiological and Biochemical Foundations of Neurocritical Care

Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood-brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the information from all monitoring techniques should be presented bedside online. Accordingly, in the future, the chemical variables obtained from microdialysis will probably be analyzed by biochemical sensors.

Improving the quantitative accuracy of cerebral oxygen saturation in monitoring the injured brain using atlas based Near Infrared Spectroscopy models

The application of Near Infrared Spectroscopy (NIRS) for the monitoring of the cerebral oxygen saturation within the brain is well established, albeit using temporal data that can only measure relative changes of oxygenation state of the brain from a baseline. The focus of this investigation is to demonstrate that hybridisation of existing near infrared probe designs and reconstruction techniques can pave the way to produce a system and methods that can be used to monitor the absolute oxygen saturation in the injured brain. Using registered Atlas models in simulation, a novel method is outlined by which the quantitative accuracy and practicality of NIRS for specific use in monitoring the injured brain, can be improved, with cerebral saturation being recovered to within 10.1 ± 1.8% of the expected values.

Fluid management of the neurological patient: a concise review

Maintenance fluids in critically ill brain-injured patients are part of routine critical care. Both the amounts of fluid volumes infused and the type and tonicity of maintenance fluids are relevant in understanding the impact of fluids on the pathophysiology of secondary brain injuries in these patients. In this narrative review, current evidence on routine fluid management of critically ill brain-injured patients and use of haemodynamic monitoring is summarized. Pertinent guidelines and consensus statements on fluid management for brain-injured patients are highlighted. In general, existing guidelines indicate that fluid management in these neurocritical care patients should be targeted at euvolemia using isotonic fluids. A critical appraisal is made of the available literature regarding the appropriate amount of fluids, haemodynamic monitoring and which types of fluids should be administered or avoided and a practical approach to fluid management is elaborated. Although hypovolemia is bound to contribute to secondary brain injury, some more recent data have emerged indicating the potential risks of fluid overload. However, it is acknowledged that many factors govern the relationship between fluid management and cerebral blood flow and oxygenation and more research seems warranted to optimise fluid management and improve outcomes.

Analysis of the association of fluid balance and short-term outcome in traumatic brain injury

INTRODUCTION

A balance of fluid intake and output (fluid balance) influences outcomes of critical illness, but the level of such influence remains poorly understood for traumatic brain injury (TBI) and was quantitatively examined in this study.

METHODS

We conducted a retrospective cohort study of 351 moderate and severe TBI patients to associate the degree of fluid balance with clinical outcomes of TBI. Fluid balance and intracranial pressure (ICP) were continuously recorded for 7days on patients admitted to neurocritical care unit (NCCU). The short-term outcome was dichotomized into improvement and deterioration groups based on changes in Glasgow Coma Scale (GCS) measured between admission and 30days after admission. Fluid balance was calculated as: Fluid intake (mL) - fluid outputs (mL)/day×5 and used to group patients in tertiles to study its effect on TBI outcome.

RESULTS

Patients at the low (<637mL) and upper (>3673mL) tertiles of fluid balance were associated with poor outcomes. Those in the upper tertile also had a higher incidence of acute kidney injury (AKI) and refractory intracranial hypertension (RIH). There was a negative correlation between the cumulative fluid balance and the short-term outcome for patients in the low tertile and a positive correlation between the cumulative fluid balance and the short-term outcome in the upper fluid balance group. Levels of fluid balance were also associated with serum creatinine (Cr, r=0.451, P<0.0001) and days in NCCU (r=0.188, P=0.001). More patients in the upper tertile had ICP higher than 20mmHg (P=0.009). A fluid balance in the upper tertile is an independent predictor of poor 30-day clinical outcomes after the adjustment for confounding variables in a multivariable logistic regression model.

CONCLUSION

We found that fluid balance in low and upper tertiles were associated with poor short-term outcomes and ICP variations. Fluid balance in the upper tertile may be an independent predictor for poor 30-day outcome, primarily due to high AKI and RIH.

Normobaric hyperoxia is associated with increased cerebral excitotoxicity after severe traumatic brain injury

BACKGROUND

Normobaric oxygen therapy is frequently applied in neurocritical care, however, whether supplemental FiO2 has beneficial cerebral effects is still controversial. We examined in patients with severe traumatic brain injury (TBI) the effect of incremental FiO2 on cerebral excitotoxicity, quantified by cerebral microdialysis (CMD) glutamate.

METHODS

This was a retrospective analysis of a database of severe TBI patients monitored with CMD and brain tissue oxygen (PbtO2). The relationship of FiO2--categorized into four separate ranges (<40, 41-60, 61-80, and >80 %)--with CMD glutamate was examined using ANOVA with Tukey's post hoc test.

RESULTS

A total of 1,130 CMD samples from 36 patients--monitored for a median of 4 days--were examined. After adjusting for brain (PbtO2, intracranial pressure, cerebral perfusion pressure, lactate/pyruvate ratio, Marshall CT score) and systemic (PaCO2, PaO2, hemoglobin, APACHE score) covariates, high FiO2 was associated with a progressive increase in CMD glutamate [8.8 (95 % confidence interval 7.4-10.2) µmol/L at FiO2 < 40 % vs. 12.8 (10.9-14.7) µmol/L at 41-60 % FiO2, 19.3 (15.6-23) µmol/L at 61-80 % FiO2, and 22.6 (16.7-28.5) µmol/L at FiO2 > 80 %; multivariate-adjusted p < 0.05]. The threshold of FiO2-related increase in CMD glutamate was lower for samples with normal versus low PbtO2 < 20 mmHg (FiO2 > 40 % vs. FiO2 > 60 %). Hyperoxia (PaO2 > 150 mmHg) was also associated with increased CMD glutamate (adjusted p < 0.001).

CONCLUSIONS

Incremental normobaric FiO2 levels were associated with increased cerebral excitotoxicity in patients with severe TBI, independent from PbtO2 and other important cerebral and systemic determinants. These data suggest that supra-normal oxygen may aggravate secondary brain damage after severe TBI.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Options for managing raised intracranial pressure

This article reviews the current monitoring and management options for raised intracranial pressure (ICP), primarily in traumatic head injuries, in line with current literature and guidelines. The use of ICP monitoring is useful in managing, predicting outcomes, following the progression and guiding interventions of neurological disease states.

Patients with raised ICP should be monitored closely in a neurocritical care setting where appropriate interventions can be instituted based on available monitoring parameters. Various first- and second-tier methods should be considered, with the primary goal to decrease secondary insult to brain tissue for best outcomes.

Response of brain oxygen to therapy correlates with long-term outcome after subarachnoid hemorrhage

BACKGROUND

Brain oxygen (PbtO2) monitoring can help guide care of poor-grade aneurysmal subarachnoid hemorrhage (aSAH) patients. The relationship between PbtO2-directed therapy and long-term outcome is unclear. We hypothesized that responsiveness to PbtO2-directed interventions is associated with outcome.

METHODS

Seventy-six aSAH patients who underwent PbtO2 monitoring were included. Long-term outcome [Glasgow Outcome Score-Extended (GOS-E) and modified Rankin Scale (mRS)] was ascertained using the social security death database and structured telephone interviews. Univariate and multivariate regression were used to identify variables that correlated with outcome.

RESULTS

Data from 64 patients were analyzed (12 were lost to follow-up). There were 530 episodes of compromised PbtO2 (<20 mmHg) during a total of 7,174 h of monitor time treated with 1,052 interventions. Forty-two patients (66 %) survived to discharge. Median follow-up was 8.5 months (range 0.1-87). At most recent follow-up 35 (55 %) patients were alive, and 28 (44 %) had a favorable outcome (mRS ≤3). In multivariate ordinal regression analysis, only age and response to PbtO2-directed intervention correlated significantly with outcome. Increased age was associated with worse outcome (coeff. 0.8, 95 % CI 0.3-1.3, p = 0.003), and response to PbtO2-directed intervention was associated with improved outcome (coeff. -2.12, 95 % CI -4.0 to -0.26, p = 0.03). Patients with favorable outcomes had a 70 % mean rate of response to PbtO2-directed interventions whereas patients with poor outcomes had a 45 % response rate (p = 0.005).

CONCLUSIONS

Response to PbtO2-directed intervention is associated with improved long-term functional outcome in aSAH patients.

Brain Tissue Oxygen Monitoring in Neurocritical Care

Brain injury results from ischemia, tissue hypoxia, and a cascade of secondary events. The cornerstone of neurocritical care management is optimization and maintenance of cerebral blood flow (CBF) and oxygen and substrate delivery to prevent or attenuate this secondary damage. New techniques for monitoring brain tissue oxygen tension (PtiO2) are now available. Brain PtiO2 reflects both oxygen delivery and consumption. Brain hypoxia (low brain PtiO2) has been associated with poor outcomes in patients with brain injury. Strategies to improve brain PtiO2 have focused mainly on increasing oxygen delivery either by increasing CBF or by increasing arterial oxygen content. The results of nonrandomized studies comparing brain PtiO2-guided therapy with intracranial pressure/cerebral perfusion pressure-guided therapy, while promising, have been mixed. More studies are needed including prospective, randomized controlled trials to assess the true value of this approach. The following is a review of the physiology of brain tissue oxygenation, the effect of brain hypoxia on outcome, strategies to increase oxygen delivery, and outcome studies of brain PtiO2-guided therapy in neurocritical care.

Aggressive early crystalloid resuscitation adversely affects outcomes in adult blunt trauma patients: an analysis of the Glue Grant database

BACKGROUND

Evidence suggests that aggressive crystalloid resuscitation is associated with significant morbidity in various clinical settings. We wanted to assess whether aggressive early crystalloid resuscitation adversely affects outcomes in adult blunt trauma patients.

METHODS

Data were derived from the Glue Grant database. Our primary outcome measure was all-cause in-hospital mortality. Secondary outcomes included days on mechanical ventilation; intensive care unit (ICU) and hospital length of stay (LOS); inflammatory (acute lung injury and adult respiratory distress syndrome, or multiple-organ failure) and resuscitation-related morbidity (abdominal and extremity compartment syndromes or acute renal failure) and nosocomial infections (ventilator-associated pneumonia, bloodstream, urinary tract, and surgical site infections).

RESULTS

In our sample of 1,754 patients, in-hospital mortality was not affected, but ventilator days (p < 0.001) as well as ICU (p = 0.009) and hospital (p = 0.002) LOS correlated strongly with the amount of crystalloids infused in the first 24 hours after injury. Amount of crystalloid resuscitation was also associated with the development of adult respiratory distress syndrome (p < 0.001), multiple-organ failure (p < 0.001), bloodstream (p = 0.001) and surgical site infections (p < 0.001), as well as abdominal (p < 0.001) and extremity compartment syndromes (p = 0.028) in a dose-dependent fashion, when age, Glasgow Coma Scale (GCS), severity of injury and acute physiologic derangement, comorbidities, as well as colloid and blood product transfusions were controlled for.

CONCLUSION

Crystalloid resuscitation is associated with a substantial increase in morbidity, as well as ICU and hospital LOS in adult blunt trauma patients.

Parenchymal brain oxygen monitoring in the neurocritical care unit

Patients admitted to the neurocritical care unit (NCCU) often have serious conditions that can be associated with high morbidity and mortality. Pharmacologic agents or neuroprotectants have disappointed in the clinical environment. Current NCCU management therefore is directed toward identification, prevention, and treatment of secondary cerebral insults that evolve over time and are known to aggravate outcome. This strategy is based on a variety of monitoring techniques including use of intraparenchymal monitors. This article reviews parenchymal brain oxygen monitors, including the available technologies, practical aspects of use, the physiologic rationale behind their use, and patient management based on brain oxygen.

Management of intracerebral pressure in the neurosciences critical care unit

Management of intracranial pressure in neurocritical care remains a potentially valuable target for improvements in therapy and patient outcomes. Surrogate markers of increased intracranial pressure, invasive monitors, and standard therapy, as well as promising new approaches to improve cerebral compliance are discussed, and a current review of the literature addressing this metric in neuroscience critical care is provided.

Early cerebral metabolic crisis after TBI influences outcome despite adequate hemodynamic resuscitation

BACKGROUND

Optimal resuscitation after traumatic brain injury (TBI) remains uncertain. We hypothesize that cerebral metabolic crisis is frequent despite adequate resuscitation of the TBI patient and that metabolic crisis negatively influences outcome.

METHODS

We assessed the effectiveness of a standardized trauma resuscitation protocol in 89 patients with moderate to severe TBI, and determined the frequency of adequate resuscitation. Prospective hourly values of heart rate, blood pressure, pulse oximetry, intracranial pressure (ICP), respiratory rate, jugular venous oximetry, and brain extracellular values of glucose, lactate, pyruvate, glycerol, and glutamate were obtained. The incidence during the initial 72 h after injury of low brain glucose <0.8 mmol/L, elevated lactate/pyruvate ratio (LPR) >25, and metabolic crisis, defined as the simultaneous occurrence of both low glucose and high LPR, were determined for the group.

RESULTS

5 patients were inadequately resuscitated and eight patients had intractable ICP. In patients with successful resuscitation and controlled ICP (n = 76), within 72 h of trauma, 76% had low glucose, 93% had elevated LPR, and 74% were in metabolic crisis. The duration of metabolic crisis was longer in those patients with unfavorable (GOSe ≤ 6) versus favorable (GOSe ≥ 7) outcome at 6 months (P = 0.011). In four multivariate models the burden of metabolic crisis was a powerful independent predictor of poor outcome.

CONCLUSIONS

Metabolic crisis occurs frequently after TBI despite adequate resuscitation and controlled ICP, and is a strong independent predictor of poor outcome at 6 months.

Comparison between cerebral tissue oxygen tension and energy metabolism in experimental subdural hematoma

BACKGROUND

An experimental swine model (n = 7) simulating an acute subdural hematoma (ASDH) was employed (1) to explore the relation between the brain tissue oxygenation (PbtO(2)) and the regional cerebral energy metabolism as obtained by microdialysis, and (2) to define the lowest level of PbtO(2) compatible with intact energy metabolism.

METHODS

ASDH was produced by infusion of 7 ml of autologous blood (infusion rate 0.5 ml/min) by a catheter placed subdurally. PbtO(2) and microdialysis probes were placed symmetrically in the injured ("bad-side") and non-injured ("good-side") hemispheres. Intracranial pressure (ICP) was monitored in the "good-side."

RESULTS

ICP, cerebral perfusion pressure (CPP), PbtO(2), glucose, lactate, pyruvate, lactate-pyruvate ratio (LP ratio), glutamate, and glycerol were recorded at baseline (60 min) and post trauma (360 min). After the creation of the ASDH, PbtO(2) decreased significantly in both the hemispheres (P < 0.001). No significant difference was found between the sides post trauma. The LP ratio, glutamate, and glycerol in the "bad-side" increased significantly over the "good-side" where the values remained within the normal limits. A PbtO(2) value below approximately 25 mmHg was found to be associated with disturbed energy metabolism in the "bad-side" but not in the "good-side." No correlation was found between the LP ratio and PbtO(2) in either hemisphere.

CONCLUSIONS

PbtO(2) monitoring accurately describes tissue oxygenation but does not disclose whether the oxygen delivery is sufficient for maintaining cerebral energy metabolism. Accordingly, it may not be possible to define a threshold level for PbtO(2) below which energy failure and permanent tissue damage occurs.

Advanced hemodynamic monitoring: principles and practice in neurocritical care

Advanced hemodynamic monitoring is necessary for many patients with acute brain and/or spinal cord injury. Optimizing cerebral and systemic physiology requires multi-organ system function monitoring. Hemodynamic manipulations are cardinal among interventions to regulate cerebral perfusion pressure and cerebral blood flow. The pulmonary artery catheter is not any more the sole tool available; less invasive and potentially more accurate methodologies have been developed and employed in the operating room and among diverse critically ill populations. These include transpulmonary thermodilution, arterial pressure pulse contour, and waveform analysis and bedside critical care ultrasound. A thorough understanding of hemodynamics and of the available monitoring modalities is an essential skill for the neurointensivist.

Reduced brain tissue oxygen in traumatic brain injury: are most commonly used interventions successful?

BACKGROUND

Brain tissue oxygenation (PbtO2)-guided management facilitates treatment of reduced PbtO2 episodes potentially conferring survival and outcome advantages in severe traumatic brain injury (TBI). To date, the nature and effectiveness of commonly used interventions in correcting compromised PbtO2 in TBI remains unclear. We sought to identify the most common interventions used in episodes of compromised PbtO2 and to analyze which were effective.

METHODS

A retrospective 7-year review of consecutive severe TBI patients with a PbtO2 monitor was conducted in a Level I trauma center's intensive care unit or neurosurgical registry. Episodes of compromised PbtO2 (defined as <20 mm Hg for 0.25-4 hours) were identified, and clinical interventions conducted during these episodes were analyzed. Response to treatment was gauged on how rapidly (ΔT) PbtO2 normalized (>20 mm Hg) and how great the PbtO2 increase was (ΔPbtO2). Intracranial pressure (ΔICP) and cerebral perfusion pressure (ΔCPP) also were examined for these episodes.

RESULTS

Six hundred twenty-five episodes of reduced PbtO2 were identified in 92 patients. Patient characteristics were: age 41.2 years, 77.2% men, and Injury Severity Score and head or neck Abbreviated Injury Scale score of 34.0 ± 9.2 and 4.9 ± 0.4, respectively. Five interventions: narcotics or sedation, pressors, repositioning, FIO2/PEEP increases, and combined sedation or narcotics + pressors were the most commonly used strategies. Increasing the number of interventions resulted in worsening the time to PbtO2 correction. Triple combinations resulted in the lowest ΔICP and dual combinations in the highest ΔCPP (p < 0.05).

CONCLUSION

Clinicians use a limited number of interventions when correcting compromised PbtO2. Using strategies employing many interventions administered closely together may be less effective in correcting PbO2, ICP, and CPP deficits. Some PbtO2 deficits may be self-limited.

Intracranial monitoring in traumatic brain injury

PURPOSE OF REVIEW

This review focuses on the role of various intracranial monitoring technologies in the diagnosis and therapy of traumatic brain injury injury.

RECENT FINDINGS

There exist many controversial points as to the utility of different intracranial monitoring with regard to improvement of outcomes from severe traumatic brain injury. Most recent studies are confirming that the use of multiple modalities in the neurological ICU setting may offer promising results.

SUMMARY

Increased adherence to guideline-based and protocol-driven neurointensive care utilizing multimodality in monitoring technology for patients with severe traumatic brain injury is likely to give clinicians increased insight into the elusive mechanisms underlying the complex pathophysiology of this disease process and may further improve outcomes in this patient population.