The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Guidelines for cerebral perfusion pressure

Asian Pacific Association for the Study of the Liver clinical practice guidelines on liver transplantation

Liver transplantation is a highly complex and challenging field of clinical practice. Although it was originally developed in western countries, it has been further advanced in Asian countries through the use of living donor liver transplantation. This method of transplantation is the only available option in many countries in the Asia-Pacific region due to the lack of deceased organ donation. As a result of this clinical situation, there is a growing need for guidelines that are specific to the Asia-Pacific region. These guidelines provide comprehensive recommendations for evidence-based management throughout the entire process of liver transplantation, covering both deceased and living donor liver transplantation. In addition, the development of these guidelines has been a collaborative effort between medical professionals from various countries in the region. This has allowed for the inclusion of diverse perspectives and experiences, leading to a more comprehensive and effective set of guidelines.

Failure of an effective physiologic threshold compliance tool to demonstrate benefit in a clinical trial of traumatic brain injury patients

BACKGROUND

Better physiologic threshold compliance holds promise for improving outcomes in neurocritical care patients.

METHODS

Our group developed a threshold compliance tool. This software computes and displays the proportion of values out of range in real time. We captured intracranial pressure (ICP) measures in our patients before and after implementation of this technology. Ten months after the threshold compliance tool was introduced we initiated a randomized controlled trial involving acute traumatic brain injury (TBI) patients to assess whether the tool was effective at reducing out-of-range ICP values.

RESULTS

A total of 54 patients with ICP monitors were included in our analysis, 42 of whom sustained a TBI. Implementation of the threshold compliance tool was associated with an 85.3% reduction in ICP values exceeding 22 mmHg in neurocritical care patients (p = 0.004) and a 76.8% reduction in patients with TBI (p = 0.043). Out-of-range values in an area-under-the-curve analysis were reduced by 78.8% in all patients (p = 0.009) and in TBI patients by 77.9% (p = 0.051). Out-of-range values were not further reduced during our randomized controlled trial examining the threshold compliance tool, and a difference between treatment groups was not suggested.

CONCLUSIONS

Implementation of a threshold compliance tool was associated with a marked and significant reduction in out-of-range ICP values. Benefit was, however, not evident in a randomized controlled trial. Our analysis provides a unique perspective on our failure to detect an apparent true difference and may provide insights into other neurotrauma trial failures.

Intracranial Hypertension and Cerebral Perfusion Pressure Insults in Adult Hypertensive Intraventricular Hemorrhage: Occurrence and Associations With Outcome

OBJECTIVES

Elevated intracranial pressure and inadequate cerebral perfusion pressure may contribute to poor outcomes in hypertensive intraventricular hemorrhage. We characterized the occurrence of elevated intracranial pressure and low cerebral perfusion pressure in obstructive intraventricular hemorrhage requiring extraventricular drainage.

DESIGN

Prospective observational cohort.

SETTING

ICUs of 73 academic hospitals.

PATIENTS

Four hundred ninety-nine patients enrolled in the CLEAR III trial, a multicenter, randomized study to determine if extraventricular drainage plus intraventricular alteplase improved outcome versus extraventricular drainage plus saline.

INTERVENTIONS

Intracranial pressure and cerebral perfusion pressure were recorded every 4 hours, analyzed over a range of thresholds, as single readings or spans (≥ 2) of readings after adjustment for intracerebral hemorrhage severity. Impact on 30- and 180-days modified Rankin Scale scores was assessed, and receiver operating curves were analyzed to identify optimal thresholds.

MEASUREMENTS AND MAIN RESULTS

Of 21,954 intracranial pressure readings, median interquartile range 12 mm Hg (8-16), 9.7% were greater than 20 mm Hg and 1.8% were greater than 30 mm Hg. Proportion of intracranial pressure readings from greater than 18 to greater than 30 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 70 mm Hg were associated with day-30 mortality and partially mitigated by intraventricular alteplase. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and intracranial pressure greater than 20 mm Hg in spans were associated with both 30-day mortality and 180-day mortality. Proportion of cerebral perfusion pressure readings from less than 65 to less than 90 mm Hg and combined intracranial pressure greater than 20 plus cerebral perfusion pressure less than 60 mm Hg were associated with poor day-30 modified Rankin Scale, whereas cerebral perfusion pressure less than 65 and less than 75 mm Hg were associated with poor day-180 modified Rankin Scale.

CONCLUSIONS

Elevated intracranial pressure and inadequate cerebral perfusion pressure are not infrequent during extraventricular drainage for severe intraventricular hemorrhage, and level and duration predict higher short-term mortality and long-term mortality. Burden of low cerebral perfusion pressure was also associated with poor short- and long-term outcomes and may be more significant than intracranial pressure. Adverse consequences of intracranial pressure-time burden and cerebral perfusion pressure-time burden should be tested prospectively as potential thresholds for therapeutic intervention.

Optimal Cerebral Perfusion Pressure in Centers With Different Treatment Protocols

OBJECTIVES

The three centers in this study have different policies regarding cerebral perfusion pressure targets and use of vasopressors in traumatic brain injury patients. The aim was to determine if the different policies affected the estimation of cerebral perfusion pressure which optimizes the strength of cerebral autoregulation, termed "optimal cerebral perfusion pressure."

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Three neurocritical care units at university hospitals in Cambridge, United Kingdom, Groningen, the Netherlands, and Uppsala, Sweden.

PATIENTS

A total of 104 traumatic brain injury patients were included: 35 each from Cambridge and Groningen, and 34 from Uppsala.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In Groningen, the cerebral perfusion pressure target was greater than or equal to 50 and less than 70 mm Hg, in Uppsala greater than or equal to 60, and in Cambridge greater than or equal to 60 or preferably greater than or equal to 70. Despite protocol differences, median cerebral perfusion pressure for each center was above 70 mm Hg. Optimal cerebral perfusion pressure was calculated as previously published and implemented in the Intensive Care Monitoring+ software by the Cambridge group, now replicated in the Odin software in Uppsala. Periods with cerebral perfusion pressure above and below optimal cerebral perfusion pressure were analyzed, as were absolute difference between cerebral perfusion pressure and optimal cerebral perfusion pressure and percentage of monitoring time with a valid optimal cerebral perfusion pressure. Uppsala had the highest cerebral perfusion pressure/optimal cerebral perfusion pressure difference. Uppsala patients were older than the other centers, and age is positively correlated with cerebral perfusion pressure/optimal cerebral perfusion pressure difference. Optimal cerebral perfusion pressure was significantly lower in Groningen than in Cambridge. There were no significant differences in percentage of monitoring time with valid optimal cerebral perfusion pressure. Summary optimal cerebral perfusion pressure curves were generated for the combined patient data for each center. These summary curves could be generated for Groningen and Cambridge, but not Uppsala. The older age of the Uppsala patient cohort may explain the absence of a summary curve.

CONCLUSIONS

Differences in optimal cerebral perfusion pressure calculation were found between centers due to demographics (age) and treatment (cerebral perfusion pressure targets). These factors should be considered in the design of trials to determine the efficacy of autoregulation-guided treatment.

Resuscitation Strategies for Traumatic Brain Injury

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality; however, little definitive evidence exists about most clinical management strategies. Here, we highlight important differences between two major guidelines, the 2016 Brain Trauma Foundation guidelines and the Lund Concept, along with recent pre-clinical and clinical data.

RECENT FINDINGS

While intracranial pressure (ICP) monitoring has been questioned, the majority of literature demonstrates benefit in severe TBI. The optimal cerebral perfusion pressure (CPP) and ICP are yet unknown, but likely as important is the concept of ICP burden. The evidence for anti-hypertensive therapy is strengthening. Decompressive craniectomy improves mortality, but at the cost of increased morbidity. Plasma-based resuscitation has demonstrated benefit in multiple pre-clinical TBI studies.

SUMMARY

The management of hemodynamics and intravascular volume are crucial in TBI. Based on recent evidence, ICP monitoring, anti-hypertensive therapy, minimal use of vasopressors/inotropes, and plasma resuscitation may improve outcomes.

Serum Procalcitonin and C-reactive Protein as Markers of Sepsis and Outcome in Patients with Neurotrauma and Subarachnoid Haemorrhage

This prospective study evaluated serum procalcitonin (PCT) and C-reactive protein (CRP) as markers for systemic inflammatory response syndrome (SIRS)/sepsis and mortality in patients with traumatic brain injury and subarachnoid haemorrhage. Sixty-two patients were followed for 7 days. Serum PCT and CRP were measured on days 0, 1, 4, 5, 6 and 7.

Seventy-seven per cent of patients with traumatic brain injury and 83% with subarachnoid haemorrhage developed SIRS or sepsis (P=0.75). Baseline PCT and CRP were elevated in 35% and 55% of patients respectively (P=0.03). There was a statistically non-significant step-wise increase in serum PCT levels from no SIRS (0.4±0.6 ng/ml) to SIRS (3.05±9.3 ng/ml) to sepsis (5.5±12.5 ng/ml). A similar trend was noted in baseline PCT in patients with mild (0.06±0.9 ng/ml), moderate (0.8±0.7 ng/ml) and severe head injury (1.2±1.9 ng/ml). Such a gradation was not observed with serum CRP. There was a non-significant trend towards baseline PCT being a better marker of hospital mortality compared with baseline CRP (ROC-AUC 0.56 vs 0.31 respectively). This is the first prospective study to document the high incidence of SIRS in neurosurgical patients. In our study, serum PCT appeared to correlate with severity of traumatic brain injury and mortality. However, it could not reliably distinguish between SIRS and sepsis in this cohort. This is in part because baseline PCT elevation seemed to correlate with severity of injury. Only a small proportion of patients developed sepsis, thus necessitating a larger sample size to demonstrate the diagnostic usefulness of serum PCT as a marker of sepsis. Further clinical trials with larger sample sizes are required to confirm any potential role of PCT as a sepsis and outcome indicator in patients with head injuries or subarachnoid haemorrhage.

What Do We Mean by Cerebral Perfusion Pressure?

INTRODUCTION

No consensus exists on the exact method for measuring mean arterial blood pressure (MAP) in the definition of cerebral perfusion pressure (CPP). The aim of the current study is to investigate how different MAP measurement methods have influenced the CPP recommendations in the Brain Trauma Foundation (BTF) guidelines.

METHODS

All papers on which the chapter on CPP thresholds in the 2007 version of the BTF guidelines is based, were reviewed. If accurate descriptions of head of bed elevation and arterial pressure transducer height were lacking, the authors were emailed for clarification. Additionally, the effect of choosing the radial artery for MAP measurement and the potential effect of gravity were studied in the literature.

RESULTS

Thresholds of CPP in the BTF guidelines are based on 11 studies. Head of bed elevation at 30° was part of the protocol in 5 studies, patients were nursed flat in 1 study, and this variable remained unknown for 5 studies. The arterial pressure transducer was at heart level in 5 studies, at ear level in 3 studies, and height was unknown in 3 studies. Measuring MAP in the radial artery underestimates carotid artery MAP by approximately 10 mmHg in the flat position, and in a nonflat position gravity influences MAP of the internal carotid artery.

CONCLUSION

There is no uniform definition for CPP, which may affect conclusions on proposed CPP targets in severe traumatic brain injury by ±10 mmHg.

Point-of-care transcranial Doppler by intensivists

In the unconscious patient, there is a diagnostic void between the neurologic physical exam, and more invasive, costly and potentially harmful investigations. Transcranial color-coded sonography and two-dimensional transcranial Doppler imaging of the brain have the potential to be a middle ground to bridge this gap for certain diagnoses. With the increasing availability of point-of-care ultrasound devices, coupled with the need for rapid diagnosis of deteriorating neurologic patients, intensivists may be trained to perform point-of-care transcranial Doppler at the bedside. The feasibility and value of this technique in the intensive care unit to help rule-in specific intra-cranial pathologies will form the focus of this article. The proposed scope for point-of-care transcranial Doppler for the intensivist will be put forth and illustrated using four representative cases: presence of midline shift, vasospasm, raised intra-cranial pressure, and progression of cerebral circulatory arrest. We will review the technical details, including methods of image acquisition and interpretation. Common pitfalls and limitations of point-of-care transcranial Doppler will also be reviewed, as they must be understood for accurate diagnoses during interpretation, as well as the drawbacks and inadequacies of the modality in general.

Early decompressing craniectomy in patients with traumatic brain injury and cerebral edema

Background: Decompressing craniectomy (DC) is an important method for the management of severe traumatic brain injury (TBI).

Objective: To analyze the effect of prophylactic DC within 24 hours after head trauma TBI.

Methods: Seventy-two patients undergoing prophylactic DC for severe TBI were included in this retrospective study. Both of the early and late outcomes were studied and the prognostic factors were analyzed.

Results: In this series, cumulative death in the first 30 days after DC was 26%, and 28 (53%) of 53 survivors in the first month had a good outcomes. The factors including Glasgow Coma Score (GCS) score at admission, whether the patient had an abnormal pupil response and whether the midline shift was greater than 5 mm were most important prognostic factors for the prediction of death in the first 30 days and the final outcome at 6 months after DC.

Conclusion: Prophylactic DC plays an important role in the management of highly elevated ICP, especially when other methods of reduction of ICP are unavailable.

Considerations in Fluids and Electrolytes After Traumatic Brain Injury

Appropriate fluid management of patients with traumatic brain injury (TBI) presents a challenge for many clinicians. Many of these patients may receive osmotic diuretics for the treatment of increased intracranial pressure or develop sodium disturbances, which act to alter fluid balance. However, establishment of fluid balance is extremely important for improving patient outcomes after neurologic injury. The use of hyperosmolar fluids, such as hypertonic saline, has gained significant interest because they are devoid of dehydrating properties and may have other beneficial properties for patients with TBI. Electrolyte derangements are also common after neurologic injury, with many having neurologic manifestations. In addition, the role of electrolyte abnormalities in the secondary neurologic injury cascade is being delineated and may offer a potential future therapeutic intervention.

Elevated Diastolic Closing Margin Is Associated with Intraventricular Hemorrhage in Premature Infants

OBJECTIVE

To determine whether the diastolic closing margin (DCM), defined as diastolic blood pressure minus critical closing pressure, is associated with the development of early severe intraventricular hemorrhage (IVH).

STUDY DESIGN

A reanalysis of prospectively collected data was conducted. Premature infants (gestational age 23-31 weeks) receiving mechanical ventilation (n = 185) had ∼1-hour continuous recordings of umbilical arterial blood pressure, middle cerebral artery cerebral blood flow velocity, and PaCO2 during the first week of life. Models using multivariate generalized linear regression and purposeful selection were used to determine associations with severe IVH.

RESULTS

Severe IVH (grades 3-4) was observed in 14.6% of the infants. Irrespective of the model used, Apgar score at 5 minutes and DCM were significantly associated with severe IVH. A clinically relevant 5-mm Hg increase in DCM was associated with a 1.83- to 1.89-fold increased odds of developing severe IVH.

CONCLUSION

Elevated DCM was associated with severe IVH, consistent with previous animal data showing that IVH is associated with hyperperfusion. Measurement of DCM may be more useful than blood pressure in defining cerebral perfusion in premature infants.

The physiologic effects of indomethacin test on CPP and ICP in severe traumatic brain injury (sTBI)

BACKGROUND

Refractory intracranial hypertension (RICH) is associated with high mortality in severe traumatic brain injury (sTBI). Indomethacin (INDO) can decrease intracranial cerebral pressure (ICP) improving cerebral pressure perfusion (CPP). Our aim was to determine modifications in ICP and CPP following INDO in RICH secondary to sTBI.

METHODS

INDO was administered in a loading dose (0.8 mg/kg/15 min), followed by continuous 2-h infusion period (0.5 mg/kg/h). Clinical outcome was assessed at 30 days according to Glasgow Outcome Scale (GOS). Differences in ICP and CPP values were assessed using repeated-measures ANOVA. Receiver operating characteristic curve (AUC) was used for discrimination in predicting 30-day survival and good functional outcome (GOS 4 or 5). Analysis of INDO safety profile was also conducted.

RESULTS

Thirty-two patients were included. Median GCS score was 6 (interquartile range: 4-7). The most frequent CT finding was the evacuated mass lesion (EML) according to Marshall classification (28.1 %). Mortality rate was 34.4 %. Within 15 min of INDO infusion, ICP decreased (Δ%: -54.6 %; P < 0.0001), CPP increased (Δ%: +44.0 %; P < 0.0001), and the remaining was stable during the entire infusion period. Patients with good outcome (n = 12) showed a greater increase of CPP during INDO test (P = 0.028). CPP response to INDO test discriminated moderately well surviving patients (AUC = 0.751; P = 0.0098) and those with good functional recovery (AUC = 0.763; P = 0.0035) from those who died and from those with worse functional outcome, respectively. No adverse events were observed.

CONCLUSIONS

INDO appears effective in reducing ICP and improving CPP in RICH. INDO test could be a useful tool in identifying RICH patients with favorable outcome. Future studies are needed.

No exacerbation of perihematomal edema with intraventricular tissue plasminogen activator in patients with spontaneous intraventricular hemorrhage

INTRODUCTION

In severe spontaneous intraventricular hemorrhage (IVH), intraventricular (IVR) administration of tissue plasminogen activator (rtPA) clears blood from the ventricles more rapidly than with external ventricular drainage (EVD) alone. However, experimental studies suggest tPA may be neurotoxic in compromised brain tissue and may exacerbate perihematomal edema.

METHODS

We used computerized volumetrics to assess change in intracerebral hemorrhage (ICH), IVH, ventricular, and perihematomal edema (PHE) volumes at 2-4 (T1) and 5-9 (T2) days following diagnostic CT scans (T0) of 24 patients (12 tPA-treated; 12 controls) with IVH requiring EVD. Controls from a hospital registry were matched by IVH and ICH volume to tPA-treated patients who came from a multicenter trial involving 52 patients with IVH.

RESULTS

There were no significant differences between matched pairs in admission ICH and IVH volumes. IVR tPA resulted in more rapid clearance of IVH as determined by T2-T0 decrease in median IVH volume (tPA: -18.7 cc, iqr 14.9; control:-6.9 cc, iqr 6.4; P = 0.002). Median ratios of PHE to ICH volume were not significantly different in control versus tPA-treated patients at T1 and T2 [control:tPA = 0.55:0.56 (T1); P = 0.84 and 0.81:0.71 (T2); P = 1.00]. Total ventricular volume was significantly larger in the control group at T2 (mean: 57.57 ± 10.32 vs. tPA: 24.80 ± 2.67 cc; P = 0.01). Bacterial ventriculitis was more frequent in the control group (5 vs. 1 episodes; P = 0.06) as was shunt dependence (4 vs. 0 cases; P = 0.03).

CONCLUSIONS

For case matched large IVH with small ICH volume, IVR tPA enhances lysis of intraventricular blood clots and has no significant impact on PHE.

Effect of mannitol on cerebrovascular pressure reactivity in patients with intracranial hypertension

BACKGROUND/PURPOSE

Mannitol is commonly used in patients with increased intracranial pressure (ICP), but its effect on cerebrovascular pressure reactivity (CVPR) is uncertain. We analyzed the changes of pressure reactivity index (PRx) during the course of mannitol treatment.

METHODS

Twenty-one patients who received mannitol treatment for increased ICP were recruited prospectively. Continuous waveforms of arterial blood pressure (ABP) and ICP were collected simultaneously for 60 minutes (10 minutes at baseline and 50 minutes since mannitol administration) during 37 events of mannitol treatment. The correlation coefficients between the mean ABP and ICP were averaged every 10 minutes and labeled as the PRx. The linear correlation of six time points of PRx in each event was calculated to represent the trend of CVPR changes. The negative slope of correlation was defined as improvement in CVPR under mannitol treatment and vice versa.

RESULTS

At baseline, the average of ICP was 26.0 ± 9.1 mmHg and the values of PRx were significantly correlated with ICP (p = 0.0044, r = 0.46). After mannitol administration, the average of ICP decreased significantly to 21.2 ± 11.1 mmHg (p = 0.036), and CVPR improved in 59.4 % of all events. Further analysis showed that low baseline cerebral perfusion pressure was the only hemodynamic parameter significant association with the improvement of CVPR after mannitol treatment (p = 0.039).

CONCLUSION

Despite lowering ICP, mannitol may have diverse effects on CVPR in patients with intracranial hypertension. Our study suggests that mannitol infusion may have a beneficial effect on CVPR, particularly in those with a low cerebral perfusion pressure at baseline.

Online correlation of spontaneous arterial and intracranial pressure fluctuations in patients with diffuse severe head injury

Determination of relevant clinical monitoring parameters for helping guide the intensive care therapy in patients with severe head injury, is one of the most demanding issues in neurotrauma research. New insights into cerebral autoregulation and metabolism have revealed that a rigid cerebral perfusion pressure (CPP) regimen might not be suitable for all severe head injured patients. We thus developed an online analysis technique to monitor the correlation (AI rho) between the spontaneous fluctuations of the mean arterial blood pressure (MABP) and the intracranial pressure (ICP). In addition, brain tissue oxygen (PtiO2) and metabolic microdialysate measures including glucose and lactate were registered. We found that in patients with good outcome, the AI rho values were significantly lower as compared with patients with poor outcome. Accordingly, microdialysate glucose and lactate were significantly higher in the good outcome group. We conclude that online determination of AI rho offers a valuable additional and technically easily performable tool for guidance of therapy in patients with severe head injury.

Activation of P2X7 promotes cerebral edema and neurological injury after traumatic brain injury in mice

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Cerebral edema, the abnormal accumulation of fluid within the brain parenchyma, contributes to elevated intracranial pressure (ICP) and is a common life-threatening neurological complication following TBI. Unfortunately, neurosurgical approaches to alleviate increased ICP remain controversial and medical therapies are lacking due in part to the absence of viable drug targets. In the present study, genetic inhibition (P2X7-/- mice) of the purinergic P2x7 receptor attenuated the expression of the pro-inflammatory cytokine, interleukin-1β (IL-1β) and reduced cerebral edema following controlled cortical impact, as compared to wild-type mice. Similarly, brilliant blue G (BBG), a clinically non-toxic P2X7 inhibitor, inhibited IL-1β expression, limited edemic development, and improved neurobehavioral outcomes after TBI. The beneficial effects of BBG followed either prophylactic administration via the drinking water for one week prior to injury or via an intravenous bolus administration up to four hours after TBI, suggesting a clinically-implementable therapeutic window. Notably, P2X7 localized within astrocytic end feet and administration of BBG decreased the expression of glial fibrillary acidic protein (GFAP), a reactive astrocyte marker, and attenuated the expression of aquaporin-4 (AQP4), an astrocytic water channel that promotes cellular edema. Together, these data implicate P2X7 as a novel therapeutic target to prevent secondary neurological injury after TBI, a finding that warrants further investigation.

Occurrence and impact of intracranial pressure elevation during treatment of severe intraventricular hemorrhage

OBJECTIVES

Elevated intracranial pressure is one of the proposed mechanisms leading to poor outcomes in patients with intraventricular hemorrhage. We sought to characterize the occurrence and significance of intracranial hypertension in severe intraventricular hemorrhage requiring extraventricular drainage.

DESIGN

Prospective analysis from two randomized, multicenter, clinical trials.

SETTING

Intensive care units of 23 academic hospitals.

PATIENTS

One hundred patients with obstructive intraventricular hemorrhage and intracerebral hemorrhage volume <30 mL requiring emergency extraventricular drainage from two randomized multicenter studies comparing intraventricular recombinant tissue plasminogen activator (n=78) to placebo (n=22).

INTERVENTIONS

Intracranial pressure was recorded every 4 hrs in all patients and before and after a 1-hr extraventricular drainage closure period after injection. Intracranial pressure readings were analyzed at predefined thresholds and compared between treatment groups, before and after injection of study agent, and before and after opening of third and fourth ventricles on computed tomography. Impact on 30-day outcomes was assessed.

MEASUREMENTS AND MAIN RESULTS

Initial intracranial pressure ranged from -2 to 60 mm Hg (median; interquartile range, 11;10). Of 2576 intracranial pressure readings, 91.5% (2359) were ≤20 mm Hg, 1.6% were >30, 0.5% were >40, and 0.2% were >50 mm Hg. In a multivariate analysis, threshold events>20 mm Hg and >30 mm Hg were more frequent in placebo vs. recombinant tissue plasminogen activator-treated groups (p=.03 and p=.08, respectively). Intracranial pressure elevation>20 mm Hg occurred during a required 1-hr extraventricular drainage closure interval in 207 of 868 (23.8%) injections of study agent, although early reopening of the extraventricular drainage only occurred in 7.9%. After radiographic opening of the lower ventricular system, intracranial pressure events>20 mm Hg remained significantly associated with initial intraventricular hemorrhage volume (p=.002) and extraventricular drainage placement ipsilateral to the largest intraventricular hemorrhage volume (p=.001), but not with thrombolytic treatment (p=.05) or intracerebral hemorrhage volume (p=.14). Ventriculoperitoneal shunts were required in 13.6% of placebo and 6.4% of recombinant tissue plasminogen activator-treated patients (p=.37). Percentage of intracranial pressure readings per patient>30 mm Hg and initial intracerebral hemorrhage and intraventricular hemorrhage volumes were independent predictors of 30-day mortality after adjustment for other outcome predictors (p=.003, p=.03, and p<.001, respectively). Independent predictors of poor modified Rankin Scale score at 30 days were percent of intracranial pressure events>30 mm Hg per patient (p=.01; but not >20 mm Hg), both intracerebral hemorrhage and intraventricular hemorrhage volume, and pulse pressure.

CONCLUSIONS

Intracranial pressure is not frequently elevated during monitoring and drainage with an extraventricular drainage in patients with severe intraventricular hemorrhage, although intracranial pressure >30 mm Hg predicts higher short-term mortality. Thrombolytic therapy may reduce the frequency of high intracranial pressure events. Intracranial pressure elevation appears to be significantly correlated with extraventricular drainage placement in the ventricle with greatest clot volume.

Cerebral perfusion pressure, microdialysis biochemistry and clinical outcome in patients with traumatic brain injury

BACKGROUND

Traumatic Brain Injury (TBI) is a major cause of death and disability. It has been postulated that brain metabolic status, intracranial pressure (ICP) and cerebral perfusion pressure (CPP) are related to patients' outcome. The aim of this study was to investigate the relationship between CPP, ICP and microdialysis parameters and clinical outcome in TBIs.

RESULTS

Thirty four individuals with severe brain injury hospitalized in an intensive care unit participated in this study. Microdialysis data were collected, along with ICP and CPP values. Glasgow Outcome Scale (GOS) was used to evaluate patient outcome at 6 months after injury. Fifteen patients with a CPP greater than 75 mmHg, L/P ratio lower than 37 and Glycerol concentration lower than 72 mmol/l had an excellent outcome (GOS 4 or 5), as opposed to the remaining 19 patients. No patient with a favorable outcome had a CPP lower than 75 mmHg or Glycerol concentration and L/P ratio greater than 72 mmol/l and 37 respectively. Data regarding L/P ratio and Glycerol concentration were statistically significant at p = 0.05 when patients with favorable and unfavorable outcome were compared. In a logistic regression model adjusted for age, sex and Glasgow Coma Scale on admission, a CPP greater than 75 mmHg was marginally statistically significantly related to outcome at 6 months after injury.

CONCLUSIONS

Patients with favorable outcome had certain common features in terms of microdialysis parameters and CPP values. An individualized approach regarding CPP levels and cut -off points for Glycerol concentration and L/P ratio are proposed.

Decompressive craniectomy for elderly patients with traumatic brain injury: it's probably not worth the while

Decompressive craniectomy (DC) has been regarded as an ultima ratio measure in the treatment of refractory intracranial hypertension after brain injury. Most discussion about its benefits is based on studies performed in patients who are <65 years of age. The aim of this study was to identify patients aged ≥66 years who underwent DC after traumatic brain injury (TBI), in order to assess patient outcome and to correlate the values of potential predictors of survival on prognosis. From January 2002 to December 2009, 44 patients aged ≥66 underwent DC (follow-up, 12-102 months). Potential predictors of outcome were analyzed, including age, post-resuscitation Glasgow Coma Scale (GCS) score, presence of mass lesion, Simplified Acute Physiology Score (SAPS) II, Injury Severity Score (ISS), and timing of surgical decompression. Mortality was 48% at discharge from the intensive care unit (ICU), 57% at hospital discharge, and 77% at 1-year follow-up and at last follow-up. A bad outcome Glasgow Outcome Scale Dead-Vegetative State-Severely Disabled (GOS D-VS-SD) was observed in 36/44 patients both at hospital discharge and at 1-year follow-up. Mean SAPS II was 45.2 for patients who survived and 57.3 for patients who had died (p=0.0022). Patients who survived had a higher mean post-resuscitation GCS score (p=0.02). Logistical regression analysis indicated post-resuscitation GCS score as the only independent predictive factor for outcome. None of the 22 patients with a post-resuscitation GCS score of 3-5 had a good outcome, 2/10 (20%) patients with a post-resuscitation GCS score of 6-8 and 6/12 patients (50%) with a post-resuscitation GCS score ≥9 had a good outcome.

Simultaneous bedside assessment of global cerebral blood flow and effective cerebral perfusion pressure in patients with intracranial hypertension

BACKGROUND

We examined a bedside technique transcerebral double-indicator dilution (TCID) for global cerebral blood flow (CBF) as well as the concept of effective cerebral perfusion pressure (CPP(eff)) during different treatment options for intracranial hypertension, and compared global CBF and CPP(eff) with simultaneously obtained conventional parameters.

METHODS

Twenty-six patients developing intracranial hypertension in the course of traumatic brain injury or subarachnoid hemorrhage were prospectively analyzed using a combined assessment during elevated ventilation (n = 15) or osmotherapy (hypertonic saline or mannitol). For calculation of global CBF, injections of ice-cold indocyanine green boluses were performed and temperature and dye concentration changes were monitored in the thoracic aorta and the jugular bulb. CBF was then calculated according to the mean transit time principle. Estimation of CCP, the arterial pressure at which cerebral blood flow becomes zero, was performed by synchronized registration of corresponding values of blood flow velocity in the middle cerebral artery and arterial pressure and extrapolation to zero-flow velocity. CPP(eff) was calculated as mean arterial pressure minus critical closing pressure (CPP(eff) = MAP(c) - CCP).

RESULTS

Elevated ventilation causes a decrease in both ICP (P < 0.001) and CBF (P < 0.001). While CPP(conv) increased (P < 0.001), CPP(eff) decreased during this observation (P = 0.002). Administration of osmotherapeutic agents resulted in a decrease of ICP (P < 0.001) and a temporary increase of CBF (P = 0.052). CPP(conv) and CPP(eff) showed no striking difference under osmotherapy.

CONCLUSION

TCID allows repeated measurements of global CBF at the bedside. Elevated ventilation lowered and osmotherapy temporarily raised global CBF. In situations of increased vasotonus, CPP(eff) is a better indicator of blood flow changes than conventional CPP.

Frequency of sustained intracranial pressure elevation during treatment of severe intraventricular hemorrhage

BACKGROUND

Elevated intracranial pressure (ICP) is an important marker of neurological deterioration. The occurrence and significance of elevated ICP and low cerebral perfusion pressure (CPP) in aggressively treated spontaneous intraventricular hemorrhage (IVH) are not defined.

METHODS

We performed a secondary longitudinal exploratory data analysis of a randomized multicenter trial of urokinase (UK) versus placebo (Pcb) as a treatment for IVH. Eleven IVH patients who required an external ventricular drain (EVD) were randomized to receive either intraventricular UK or Pcb every 12 h until clinical response permitted EVD removal. ICP and CPP were recorded every 4 or 6 h, as well as before and 1 h after EVD closure for administration of study agent. ICP, CPP and the proportion of ICP readings above 20, 30, 40 and 50 mm Hg were analyzed.

RESULTS

Six UK and 5 Pcb patients aged 39-74 years (mean +/- standard deviation; 53 +/- 11 years) were enrolled. Initial ICP ranged from 0 to 38 mm Hg (10.9 +/- 11.0), initial CPP from 65 to 133 mm Hg (100.5 +/- 17.7). We recorded 472 ICP readings over the entire monitoring period. Of these 65 (14%) were >20 mm Hg, 23 (5%) >30 mm Hg, 9 (2%) >40 mm Hg and 3 (<1%) >50 mm Hg. Only 2 of 141 intraventricular injections of study agent with EVD closure were not tolerated and required reopening of the EVD.

CONCLUSIONS

In the intensive care unit, initial ICP measured with an EVD was uncommonly elevated (1/11 patients) in this group of severe IVH patients despite acute obstructive hydrocephalus. Frequent monitoring reveals ICP elevation >20 mm Hg in 14% of observations during use of EVD. ICP elevation, though it can occur, is not routinely associated with EVD closure for thrombolytic treatment with UK.

Surgical complications secondary to decompressive craniectomy in patients with a head injury: a series of 108 consecutive cases

BACKGROUND

Decompressive craniectomy is an important method for managing refractory intracranial hypertension in patients with head injury. We reviewed a large series of patients who underwent this surgical procedure to establish the incidence and type of postoperative complications.

METHODS

From 1998 to 2005, decompressive craniectomy was performed in 108 patients who suffered from a closed head injury. The incidence rates of complications secondary to decompressive craniectomy and risk factors for developing these complications were analysed. In addition, the relationship between outcome and clinical factors was analysed.

FINDINGS

Twenty-five of the 108 patients died within the first month after surgical decompression. A lower GCS at admission seemed to be associated with a poorer outcome. Complications related to surgical decompression occurred in 54 of the 108 (50%) patients; of these, 28 (25.9%) patients developed more than one type of complication. Herniation through the cranial defect was the most frequent complication within 1 week and 1 month, and subdural effusion was another frequent complication during this period. After 1 month, the "syndrome of the trephined" and hydrocephalus were the most frequent complications. Older patients and/or those with more severe head trauma had a higher occurrence rate of complications.

CONCLUSIONS

The potential benefits of decompressive craniectomy can be adversely affected by the occurrence of complications. Each complication secondary to surgical decompression had its own typical time window for occurrence. In addition, the severity of head injury was related to the development of a complication.

The impact of a highly visible display of cerebral perfusion pressure on outcome in individuals with cerebral aneurysms

BACKGROUND

Nurses' ability to rapidly detect decreases in cerebral perfusion pressure (CPP), which may contribute to secondary brain injury, may be limited by poor visibility of CPP displays.

OBJECTIVE

To evaluate the impact of a highly visible CPP display on the functional outcome in individuals with cerebral aneurysms.

METHODS

Patients with cerebral aneurysms (n = 100) who underwent continuous CPP monitoring were enrolled and randomized to beds with or without the additional CPP display. Six-month outcome was assessed.

RESULTS

Functional outcome was not significantly different between control and intervention groups after controlling for initial neurologic condition (odds ratio .904, 95% confidence interval 0.317 to 2.573). However, greater time below CPP thresholds (55 to 70 mm Hg) was significantly associated with poorer outcome (P = .005 to .010).

CONCLUSIONS

Although the enhanced CPP display was not associated with significantly better outcome, longer periods of CPP below set levels were associated with poorer outcome.

Effect of hyperoxia on regional oxygenation and metabolism after severe traumatic brain injury: preliminary findings

OBJECTIVE

To determine the effect of normobaric hyperoxia on cerebral metabolism in patients with severe traumatic brain injury.

DESIGN

Prospective clinical investigation.

SETTING

Neurosciences critical care unit of a university hospital.

PATIENTS

Eleven patients with severe traumatic brain injury.

INTERVENTIONS

Cerebral microdialysis, brain tissue oximetry (PbO2), and oxygen-15 positron emission tomography (15O-PET) were undertaken at normoxia and repeated at hyperoxia (FiO2 increase of between 0.35 and 0.50).

MEASUREMENTS AND MAIN RESULTS

Established models were used to image cerebral blood flow, blood volume, oxygen metabolism, and oxygen extraction fraction. Physiology was characterized in a focal region of interest (surrounding the microdialysis catheter) and correlated with microdialysis and oximetry. Physiology was also characterized in a global region of interest (including the whole brain), and a physiologic region of interest (defined using a critical cerebral metabolic rate of oxygen threshold). Hyperoxia increased mean +/- sd PbO2 from 28 +/- 21 mm Hg to 57 +/- 47 mm Hg (p = .015). Microdialysate lactate and pyruvate were unchanged, but the lactate/pyruvate ratio showed a statistically significant reduction across the study population (34.1 +/- 9.5 vs. 32.5 +/- 9.0, p = .018). However, the magnitude of reduction was small, and its clinical significance doubtful. The focal region of interest and global 15O-PET variables were unchanged. "At-risk" tissue defined by the physiologic region of interest, however, showed a universal increase in cerebral metabolic rate of oxygen from a median (interquartile range) of 23 (22-25) micromol x 100 mL(-1) x min(-1) to 30 (28-36) micromol x 100 mL(-1) x min(-1) (p < .01).

CONCLUSIONS

In severe traumatic brain injury, hyperoxia increases PbO2 with a variable effect on lactate and lactate/pyruvate ratio. Microdialysis does not, however, predict the universal increases in cerebral metabolic rate of oxygen in at-risk tissue, which imply preferential metabolic benefit with hyperoxia.

Medical management of cerebral edema

✓Cerebral edema is frequently encountered in clinical practice in critically ill patients with acute brain injury from diverse origins and is a major cause of increased morbidity and death in this subset of patients. The consequences of cerebral edema can be lethal and include cerebral ischemia from compromised regional or global cerebral blood flow (CBF) and intracranial compartmental shifts due to intracranial pressure gradients that result in compression of vital brain structures. The overall goal of medical management of cerebral edema is to maintain regional and global CBF to meet the metabolic requirements of the brain and prevent secondary neuronal injury from cerebral ischemia. Medical management of cerebral edema involves using a systematic and algorithmic approach, from general measures (optimal head and neck positioning for facilitating intracranial venous outflow, avoidance of dehydration and systemic hypotension, and maintenance of normothermia) to specific therapeutic interventions (controlled hyperventilation, administration of corticosteroids and diuretics, osmotherapy, and pharmacological cerebral metabolic suppression). This article reviews and highlights the medical management of cerebral edema based on pathophysiological principles in acute brain injury.

Hiérarchisation des traitements de l'hypertension intracrânienne chez le traumatisé crânien grave

The objective of the treatment of intracranial hypertension is to decrease intracranial pressure (ICP) while maintaining cerebral blood flow (CBF). Despite numerous treatments, none of them associates total efficiency and security. Systemic secondary cerebral injuries, which are responsible for cerebral ischemia, lead us to administer non specific treatments in order to optimize CBF and cerebral oxygenation. Thus, the goals are: 1) to maintain cerebral perfusion pressure> or =70 mmHg; 2) to control metabolic status by preventing hyperglycaemia, anaemia and hyperthermia; 3) to maintain normoxia and normocapnia (hypercapnia increases ICP and hypocapnia decreases CBF). Beside the neurosurgical evacuation of extra- and intraparenchymatous haematomas, osmotherapy and cerebrospinal fluid (CSF) evacuation are the two specific treatments of intracranial hypertension. Osmotherapy consists in an administration of a hypertonic solution which induces a decrease in cerebral water and finally in ICP. Mannitol (20%), which is the reference, associates osmotic and rheologic effects, and decreases CSF production too. Recent data conduct us to administer larger doses, between 0.7 and 1 g/kg in 15 minutes. Hypertonic saline solution associates osmotic effects and plasma volume loading. Thus, this solution is particularly appropriate in severe head injury with arterial hypotension. CBF evacuation decreases rapidly ICP without any major side-effect. Until now, there is no proof of a superior efficiency of a treatment for intracranial hypertension compared to another. Considering their mechanism of action, all of them are efficient but potentially dangerous too. Indeed, the choice between treatments depends on data which are issued from the multimodal monitoring. General non specific treatments are always necessary. Specific treatments are indicated if ICP is above 20-25 mmHg. Maintaining cerebral perfusion pressure represents the first therapeutic goal. If intracranial hypertension persists, evacuation of CBF or osmotherapy may be advocated. In case of refractory intracranial hypertension, it may be useful to deepen neurosedation. Controlled hypocapnia and barbiturates remain a third line therapy providing to monitor and maintain an appropriate CBF and cerebral oxygenation. Controlled hypothermia and decompressive craniectomy must be individually discussed.

Neurogenic pulmonary edema

Neurogenic pulmonary edema (NPE) is usually defined as an acute pulmonary edema occurring shortly after a central neurologic insult. It has been reported regularly for a long time in numerous and various injuries of the central nervous system in both adults and children, but remains poorly understood because of the complexity of its pathophysiologic mechanisms involving hemodynamic and inflammatory aspects. NPE seems to be under-diagnosed in acute neurologic injuries, partly because the prevention and detection of non-neurologic complications of acute cerebral insults are not at the forefront of the strategy of physicians. The presence of NPE should be high on the list of diagnoses when patients with central neurologic injury suddenly become dyspneic or present with a decreased P(a)o(2)/F(i)o(2) ratio. The associated mortality rate is high, but recovery is usually rapid with early and appropriate management. The treatment of NPE should aim to meet the oxygenation needs without impairing cerebral hemodynamics, to avoid pulmonary worsening and to treat possible associated myocardial dysfunction. During brain death, NPE may worsen myocardial dysfunction, preventing heart harvesting.

Cerebral blood flow in traumatic contusions is predominantly reduced after an induced acute elevation of cerebral perfusion pressure

OBJECTIVE

To evaluate the response to an acute elevation of cerebral perfusion pressure (CPP) of the regional cerebral blood flow (rCBF) measured in the edematous area of traumatic contusions.

METHODS

rCBF was measured in the intracontusional low-density area, in the pericontusional healthy-appearing brain tissue surrounding the contusion, in a healthy-appearing area in the contralateral hemisphere, in 16 head-injured patients with 16 traumatic contusions larger than 2 cm at baseline, and after 20 minutes of norepinephrine-induced 20-mmHg elevation of CPP levels.

RESULTS

After an induced acute elevation of CPP from baseline values of 65.8 ml/100 g/min (standard deviation, 8.6) to final values of 88.7 ml/100 g/min (standard deviation, 8.9; P < or = 0.0001), we found that rCBF mean levels decreased in the intracontusional low-density area (P = 0.0278), and change in rCBF was inversely associated to the baseline values. After grouping contusions according to the rCBF response to induced acute CPP elevation, rCBF mean values recorded at baseline were significantly lower in lesions with "rCBF improvement" than in those with "rCBF reduction" in the intracontusional low-density area (P = 0.0435).

CONCLUSION

Our findings suggest that CPP elevation induced by norepinephrine is effective in improving contusional rCBF only in selected cases, which are represented by a subset of contusions with critical perfusion, which can be identified by rCBF measurements. Conversely, in contusions with rCBF higher than critical low values, the CPP elevation could probably induce a temporary breakdown of the blood brain barrier, and the norepinephrine leads to a vasoconstriction with a worsening of regional perfusion.

Osmotherapy with hypertonic saline attenuates water content in brain and extracerebral organs

OBJECTIVE

Because of their beneficial effects in patients with hemorrhagic shock and multiple-system trauma, hypertonic saline solutions are increasingly being used perioperatively for volume resuscitation. Although the anti-edema effects of hypertonic saline on brain are well documented in a variety of brain injury paradigms, its effects on the water content on other organs has not been studied rigorously. In this study, we tested the hypothesis that a) hypertonic saline when given as an intravenous bolus and continuous infusion attenuates water content of small bowel, lung, and brain in rats without neuro-injury; and b) attenuation of stroke-associated increases in lung water is dependent on achieving a target serum osmolality.

DESIGN

Prospective laboratory animal study.

SETTING

Research laboratory in a teaching hospital.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

In the first series of experiments, under controlled conditions of normoxia, normocarbia, and normothermia, spontaneously breathing, halothane-anesthetized (1.0-1.5%) adult male Wistar rats (280-320 g) were treated in a blinded randomized fashion with 7.5% hypertonic saline or 0.9% normal saline in a 8-mL/kg intravenous infusion for 3 hrs followed by a continuous intravenous infusion (1 mL/kg/hr) of 5% hypertonic saline or normal saline, respectively (n=10 each), for 48 hrs. A second group of rats were treated with continuous infusion only for 48 hrs of either 7.5% hypertonic saline or normal saline (1 mL/kg/hr) (n=10 each) without an intravenous bolus. Naïve rats served as controls (n=10). Tissue water content of small bowel, lung, and brain was determined by comparing the wet-to-dry ratios at the end of the experiment. In a second series of experiments, rats (n=94) were subjected to 2 hrs of transient middle cerebral artery occlusion by the intraluminal occlusion technique. At 6 hrs following middle cerebral artery occlusion, rats were treated in a blinded randomized fashion with a continuous intravenous infusion of normal saline, 3% hypertonic saline, or 7.5% hypertonic saline for 24, 48, 72, and 96 hrs. Surgical shams served as controls (n=7). Hypertonic saline was instituted as chloride/acetate mixture (50:50) in all experiments. Serum osmolality was determined at the end of the experiment in all animals.

MEASUREMENTS AND MAIN RESULTS

In rats without neuro-injury that received intravenous bolus followed by a continuous infusion, lung water content was significantly reduced with hypertonic saline (73.9+/-1.1%; 359+/-10 mOsm/L) (mean+/-sd) compared with normal saline treatment (76.1+/-0.53%; 298+/-4 mOsm/L) as was water content of small bowel (hypertonic saline, 69.1+/-5.8%; normal saline, 74.7+/-0.71%) and brain (hypertonic saline, 78.1+/-0.87%; normal saline, 79.2+/-0.38%) at 48 hrs. Stroke-associated increases in lung water content were attenuated with 7.5% hypertonic saline at all time points. There was a strong correlation between serum osmolality and attenuation of stroke-associated increases in lung water content (r=-.647)

CONCLUSIONS

Bowel, lung, and brain water content is attenuated with hypertonic saline when serum osmolality is >350 mOsm/L without adverse effect on mortality in animals with and without neuro-injury. Attenuation of water content of extracerebral organs with hypertonic saline treatment may have therapeutic implications in perioperative fluid management in patients with and without brain injury.

Effect of Continuous Display of Cerebral Perfusion Pressure on Outcomes in Patients With Traumatic Brain Injury

• Background Clinical bedside monitoring systems do not provide prominent displays of data on cerebral perfusion pressure (CPP). Immediate visual feedback would allow more rapid intervention to prevent or minimize suboptimal pressures.

• Objective To evaluate the effect of a highly visible CPP display on immediate and long-term functional outcome in patients with traumatic brain injury.

• Methods A total of 157 patients with traumatic brain injury at a level 1 trauma center who had invasive arterial blood pressure and intracranial pressure monitoring were randomized to beds with or without an additional, prominent continuous CPP display. Primary end points were scores on the Extended Glasgow Outcome Scale (GOSE) and Functional Status Examination (FSE) 6 months after injury. Secondary end points were GOSE scores at discharge and 3 months after injury and FSE score 3 months after injury.

• Results Although GOSE and FSE scores at 6 months were better in the group with the highly visible CPP display, the differences were not significant. Slope of recovery for GOSE and FSE over all follow-up time points did not differ significantly between groups. However, the intervention’s positive effect on odds of survival at hospital discharge was strong and significant. Within a subgroup of more severely injured patients, the intervention group was much less likely than the control group to have CPP deviations.

• Conclusions The presence of a highly visible display of CPP was associated with significantly better odds of survival and overall condition at discharge.

Multimodal cerebral monitoring and decompressive surgery for the treatment of severe bacterial meningitis with increased intracranial pressure

Bacterial meningitis is still associated with a high mortality, mainly because of cerebral herniation as a result of increased intracranial pressure. Published data stress the necessity of an early diagnosis and immediate start of antibiotic therapy. Nevertheless, there are only few reports in which therapeutic strategy was based on the monitoring and the reduction of intracranial pressure (ICP). We report one case of bacterial meningitis caused by Neisseria meningitidis with an initial ICP value of 60 mmHg, which was treated by large hemicraniectomy and ventriculostomy, leading to a favorable neurological long-term result. The surgical decision was accelerated by an accurate ICP evaluation based on cerebral monitoring [transcranial Doppler ultrasonography (TCD) and intracranial ICP-device]. In selected patients with bacterial meningitis and clinical and radiological evidence of elevated ICP, cerebral monitoring and aggressive reduction of ICP may be crucial to improve survival and neurological outcome. When maximal medical ICP treatment fails to reduce severe intracranial hypertension, decompressive craniectomy should be rapidly proposed.

Effect of duration of osmotherapy on blood-brain barrier disruption and regional cerebral edema after experimental stroke

Osmotherapy is the cornerstone of medical management for cerebral edema associated with large ischemic strokes. We determined the effect of duration of graded increases in serum osmolality with mannitol and hypertonic saline (HS) on blood-brain barrier (BBB) disruption and regional cerebral edema in a well-characterized rat model of large ischemic stroke. Halothane-anesthetized adult male Wistar rats were subjected to transient (2-h) middle cerebral artery occlusion (MCAO) by the intraluminal occlusion technique. Beginning at 6 h after MCAO, rats were treated with either no intravenous fluids or a continuous intravenous infusion (0.3 mL/h) of 0.9% saline, 20% mannitol, 3% HS, or 7.5% HS for 24, 48, 72, and 96 h. In the first series of experiments, BBB permeability was quantified by the Evans blue (EB) extravasation method. In the second series of experiments, water content was assessed by comparing wet-to-dry weight ratios in six predetermined brain regions. Blood-brain barrier disruption was maximal in rats treated with 0.9% saline for 48 h, but did not correlate with increases in serum osmolality or treatment duration with osmotic agents. Treatment with 7.5% HS attenuated water content in the periinfarct regions and all subregions of the contralateral nonischemic hemisphere to a greater extent than mannitol did with no adverse effect on survival rates. These data show that (1) BBB integrity is not affected by the duration and degree of serum osmolality with osmotic agents, and (2) attenuation of increases in brain water content with HS to target levels >350 mOsm/L may have therapeutic implications in the treatment of cerebral edema associated with ischemic stroke.

Treatment of cerebral edema

BACKGROUND

Cerebral edema is a potentially devastating complication of various acute neurologic disorders. Its successful treatment may save lives and preserve neurologic function.

REVIEW SUMMARY

Different pathophysiological mechanisms are responsible for the formation of cytotoxic and vasogenic edema. Yet, these 2 types of edema often coexist and their treatment tends to overlap, with the exception of corticosteroids, which should be only used to ameliorate vasogenic edema. Currently available to control brain swelling include osmotic agents (with emphasis on mannitol and hypertonic saline solutions), corticosteroids, hyperventilation, sedation (propofol, barbiturates), neuromuscular paralysis, hypothermia, and surgical interventions. This article discusses the indications, advantages, and limitations of each treatment modality following an evidence-based approach.

CONCLUSIONS

The therapy for brain edema remains largely empirical. More research aimed at enhancing our understanding of the pathophysiology of cerebral edema is needed to identify new and more effective forms of treatment.

Applications of transcranial Doppler in the ICU: a review

OBJECTIVE

Transcranial Doppler (TCD) ultrasonography is a technique that uses a hand-held Doppler transducer (placed on the surface of the cranial skin) to measure the velocity and pulsatility of blood flow within the intracranial and the extracranial arteries. This review critically evaluates the evidence for the use of TCD in the critical care population.

DISCUSSION

TCD has been frequently employed for the clinical evaluation of cerebral vasospasm following subarachnoid haemorrhage (SAH). To a lesser degree, TCD has also been used to evaluate cerebral autoregulatory capacity, monitor cerebral circulation during cardiopulmonary bypass and carotid endarterectomies and to diagnose brain death. Technological advances such as M mode, colour Doppler and three-dimensional power Doppler ultrasonography have extended the scope of TCD to include other non-critical care applications including assessment of cerebral emboli, functional TCD and the management of sickle cell disease.

CONCLUSIONS

Despite publications suggesting concordance between TCD velocity measurements and cerebral blood flow there are few randomized controlled studies demonstrating an improved outcome with the use of TCD monitoring in neurocritical care. Newer developments in this technology include venous Doppler, functional Doppler and use of ultrasound contrast agents.

CURRENT CONTROVERSIES IN THE MANAGEMENT OF PATIENTS WITH SEVERE TRAUMATIC BRAIN INJURY

BACKGROUND

Traumatic brain injury is a major cause of mortality and morbidity, particularly among young men. The efficacy and safety of most of the interventions used in the management of patients with traumatic brain injury remain unproven. Examples include the 'cerebral perfusion pressure-targeted' and 'volume-targeted' management strategies for optimizing cerebrovascular haemodynamics and specific interventions, such as hyperventilation, osmotherapy, cerebrospinal fluid drainage, barbiturates, decompressive craniectomy, therapeutic hypothermia, normobaric hyperoxia and hyperbaric oxygen therapy.

METHODS

A review of the literature was performed to examine the evidence base behind each intervention.

RESULTS

There is no class I evidence to support the routine use of any of the therapies examined.

CONCLUSION

Well-designed, large, randomized controlled trials are needed to determine therapies that are safe and effective from those that are ineffective or harmful.

Effects of arginine vasopressin during resuscitation from hemorrhagic hypotension after traumatic brain injury

OBJECTIVE

Two series of experiments were designed to evaluate whether early arginine vasopressin improves acute outcome following resuscitation from traumatic brain injury and severe hemorrhagic hypotension.

DESIGN

Prospective randomized, blinded animal study.

SETTING

University laboratory.

SUBJECTS

Thirty-three swine.

INTERVENTIONS

In series 1 (n = 19), after traumatic brain injury with hemorrhage and 12 mins of shock (mean arterial pressure approximately 20 mm Hg), survivors (n = 16) were initially resuscitated with 10 mL/kg crystalloid. After 30 mins, crystalloid and blood with either 0.1 unit x kg(-1) x hr(-1) arginine vasopressin or placebo was titrated to a mean arterial pressure target >or=60 mm Hg. After 90 mins, all received mannitol and the target was cerebral perfusion pressure >or=60 mm Hg. To test cerebrovascular function, 7.5% inhaled CO2 was administered periodically. In series 2 (n = 14), the identical protocol was followed except the shock period was 20 mins and survivors (n = 10) received a bolus of either arginine vasopressin (0.2 units/kg) or placebo during the initial fluid resuscitation.

MEASUREMENTS AND MAIN RESULTS

In series 1, by 300 mins after traumatic brain injury with arginine vasopressin (n = 8) vs. placebo (n = 8), the fluid and transfusion requirements were reduced (both p < .01), intracranial pressure was improved (11 +/- 1 vs. 23 +/- 2 mmHg; p < .0001), and the CO2-evoked intracranial pressure elevation was reduced (7 +/- 2 vs. 26 +/- 3 mm Hg, p < .001), suggesting improved compliance. In series 2, with arginine vasopressin vs. placebo, cerebral perfusion pressure was more rapidly corrected (p < .05). With arginine vasopressin, five of five animals survived 300 mins, whereas three of five placebo animals died. The survival time with placebo was 54 +/- 4 mins (p < .05 vs. arginine vasopressin).

CONCLUSIONS

Early supplemental arginine vasopressin rapidly corrected cerebral perfusion pressure, improved cerebrovascular compliance, and prevented circulatory collapse during fluid resuscitation of hemorrhagic shock after traumatic brain injury.