Michael F. Stiefel

Packed red blood cell transfusion increases local cerebral oxygenation.

Objective:To determine a) whether packed red blood cell transfusion (RBCT) increases local brain tissue oxygen partial pressure (Pbto2) in a neurocritical care population; and b) what (if any) demographic, clinical, or physiologic variables mediate the assumed change. Design:Prospective observational study. Setting:A neurosurgical intensive care unit at a university-based level I trauma center and tertiary care hospital. Patients:Thirty-five consecutive volume-resuscitated patients with subarachnoid hemorrhage or traumatic brain injury, without cardiac disease, requiring Pbto2 monitoring and receiving RBCT were studied between October 2001 and December 2003. Interventions:None. Measurements and Main Results:The following physiologic variables were measured and compared 1 hr before and after RBCT: Pbto2, intracranial pressure, cerebral perfusion pressure, hemoglobin oxygen saturation (Sao2), Fio2, hemoglobin, and hematocrit. An increase in Pbto2 was observed in 26 of the 35 patients (74%). In nine patients, Pbto2 decreased after RBCT. The mean (±sd) increase in Pbto2 for all patients was 3.2 ± 8.8 mm Hg (p = .02), a 15% change from baseline (1 hr before RCBT). This Pbto2 increase was associated with a significant mean increase in hemoglobin and hematocrit after RBCT (1.4 ± 1.1 g/dL and 4.2% ± 3.3%, respectively; both p < .001). Cerebral perfusion pressure, Sao2, and Fio2 were similar before and after RBCT. Among the 26 patients whose Pbto2 increased, the mean increase in Pbto2 was 5.1 ± 9.4 mm Hg or a 49% mean increase (p < .01). Conclusions:RBCT is associated with an increase in Pbto2 in most patients with subarachnoid hemorrhage or traumatic brain injury. This mean increase appears to be independent of cerebral perfusion pressure, Sao2, and Fio2. Further study is required to determine why Pbto2 decreases in some patients after RBCT.

Brain tissue oxygen–directed management and outcome in patients with severe traumatic brain injury

OBJECT The object of this study was to determine whether brain tissue oxygen (PbtO(2))-based therapy or intracranial pressure (ICP)/cerebral perfusion pressure (CPP)-based therapy is associated with improved patient outcome after severe traumatic brain injury (TBI). METHODS Seventy patients with severe TBI (postresuscitation GCS score < or = 8), admitted to a neurosurgical intensive care unit at a university-based Level I trauma center and tertiary care hospital and managed with an ICP and PbtO(2) monitor (mean age 40 +/- 19 years [SD]) were compared with 53 historical controls who received only an ICP monitor (mean age 43 +/- 18 years). Therapy for both patient groups was aimed to maintain ICP < 20 mm Hg and CPP > 60 mm Hg. Patients with PbtO(2) monitors also had therapy to maintain PbtO(2) > 20 mm Hg. RESULTS Data were obtained from 12,148 hours of continuous ICP monitoring and 6,816 hours of continuous PbtO(2) monitoring. The mean daily ICP and CPP and the frequency of elevated ICP (> 20 mm Hg) or suboptimal CPP (< 60 mm Hg) episodes were similar in each group. The mortality rate was significantly lower in patients who received PbtO(2)-directed care (25.7%) than in those who received conventional ICP and CPP-based therapy (45.3%, p < 0.05). Overall, 40% of patients receiving ICP/CPP-guided management and 64.3% of those receiving PbtO(2)-guided management had a favorable short-term outcome (p = 0.01). Among patients who received PbtO(2)-directed therapy, mortality was associated with lower mean daily PbtO(2) (p < 0.05), longer durations of compromised brain oxygen (PbtO(2) < 20 mm Hg, p = 0.013) and brain hypoxia (PbtO(2) < 15 mm Hg, p = 0.001), more episodes and a longer cumulative duration of compromised PbtO(2) (p < 0.001), and less successful treatment of compromised PbtO(2) (p = 0.03). CONCLUSIONS These results suggest that PbtO(2)-based therapy, particularly when compromised PbtO(2) can be corrected, may be associated with reduced patient mortality and improved patient outcome after severe TBI.

Guideline for Reversal of Antithrombotics in Intracranial Hemorrhage : A Statement for Healthcare Professionals from the Neurocritical Care Society and Society of Critical Care Medicine.

BackgroundThe use of antithrombotic agents, including anticoagulants, antiplatelet agents, and thrombolytics has increased over the last decade and is expected to continue to rise. Although antithrombotic-associated intracranial hemorrhage can be devastating, rapid reversal of coagulopathy may help limit hematoma expansion and improve outcomes.MethodsThe Neurocritical Care Society, in conjunction with the Society of Critical Care Medicine, organized an international, multi-institutional committee with expertise in neurocritical care, neurology, neurosurgery, stroke, hematology, hemato-pathology, emergency medicine, pharmacy, nursing, and guideline development to evaluate the literature and develop an evidence-based practice guideline. Formalized literature searches were conducted, and studies meeting the criteria established by the committee were evaluated.ResultsUtilizing the GRADE methodology, the committee developed recommendations for reversal of vitamin K antagonists, direct factor Xa antagonists, direct thrombin inhibitors, unfractionated heparin, low-molecular weight heparin, heparinoids, pentasaccharides, thrombolytics, and antiplatelet agents in the setting of intracranial hemorrhage.ConclusionsThis guideline provides timely, evidence-based reversal strategies to assist practitioners in the care of patients with antithrombotic-associated intracranial hemorrhage.

Brain Tissue Oxygen-Based Therapy and Outcome After Severe Traumatic Brain Injury: A Systematic Literature Review

Observational clinical studies demonstrate that brain hypoxia is associated with poor outcome after severe traumatic brain injury (TBI). In this study, available medical literature was reviewed to examine whether brain tissue oxygen (PbtO2)-based therapy is associated with improved patient outcome after severe TBI. Clinical studies published between 1993 and 2010 that compared PbtO2-based therapy combined with intracranial and cerebral perfusion pressure (ICP/CPP)-based therapy to ICP/CPP-based therapy alone were identified from electronic databases, Index Medicus, bibliographies of pertinent articles, and expert consultation. For analysis, each selected paper had to have adequate data to determine odds ratios (ORs) and confidence intervals (CIs) of outcome described by the Glasgow outcome score (GOS). Seven studies that compared ICP/CPP and PbtO2- to ICP/CPP-based therapy were identified. There were no randomized studies and no comparison studies in children. Four studies, published in 2003, 2009, and 2010 that included 491 evaluable patients were used in the final analysis. Among patients who received PbtO2-based therapy, 121(38.8%) had unfavorable and 191 (61.2%) had a favorable outcome. Among the patients who received ICP/CPP-based therapy 104 (58.1%) had unfavorable and 75 (41.9%) had a favorable outcome. Overall PbtO2-based therapy was associated with favorable outcome (OR 2.1; 95% CI 1.4–3.1). Summary results suggest that combined ICP/CPP- and PbtO2-based therapy is associated with better outcome after severe TBI than ICP/CPP-based therapy alone. Cross-organizational practice variances cannot be controlled for in this type of review and so we cannot answer whether PbtO2-based therapy improves outcome. However, the potentially large incremental value of PbtO2-based therapy provides justification for a randomized clinical trial.

Hemoglobin Concentration and Cerebral Metabolism in Patients With Aneurysmal Subarachnoid Hemorrhage

Background and Purpose— The optimal hemoglobin (Hgb) target after aneurysmal subarachnoid hemorrhage is not precisely known. We sought to examine the threshold of Hgb concentration associated with an increased risk of cerebral metabolic dysfunction in patients with poor-grade subarachnoid hemorrhage. Methods— Twenty consecutive patients with poor-grade subarachnoid hemorrhage who underwent multimodality neuromonitoring (intracranial pressure, brain tissue oxygen tension, cerebral microdialysis) were studied prospectively. Brain tissue oxygen tension and extracellular lactate/pyruvate ratio were used as markers of cerebral metabolic dysfunction and the relationship between Hgb concentrations and the incidence of brain hypoxia (defined by a brain tissue oxygen tension <20 mm Hg) and cell energy dysfunction (defined by a lactate/pyruvate ratio >40) was analyzed. Results— Compared with higher Hgb concentrations, a Hgb concentration <9 g/dL was associated with lower brain tissue oxygen tension (27.2 [interquartile range, 21.2 to 33.1] versus 19.9 [interquartile range, 7.1 to 33.1] mm Hg, P=0.02), higher lactate/pyruvate ratio (29 [interquartile range, 25 to 38] versus 36 [interquartile range, 26 to 59], P=0.16), and an increased incidence of brain hypoxia (21% versus 52%, P<0.01) and cell energy dysfunction (23% versus 43%, P=0.03). On multivariable analysis, a Hgb concentration <9 g/dL was associated with a higher risk of brain hypoxia (OR, 7.92; 95% CI, 2.32 to 27.09; P<0.01) and cell energy dysfunction (OR, 4.24; 95% CI, 1.33 to 13.55; P=0.02) after adjusting for cerebral perfusion pressure, central venous pressure, PaO2/FIO2 ratio, and symptomatic vasospasm. Conclusions— A Hgb concentration <9 g/dL is associated with an increased incidence of brain hypoxia and cell energy dysfunction in patients with poor-grade subarachnoid hemorrhage.

Induced Normothermia Attenuates Cerebral Metabolic Distress in Patients With Aneurysmal Subarachnoid Hemorrhage and Refractory Fever

BACKGROUND AND PURPOSE The purpose of this study was to analyze whether fever control attenuates cerebral metabolic distress after aneurysmal subarachnoid hemorrhage (SAH). METHODS Eighteen SAH patients, who underwent intracranial pressure (ICP) and cerebral microdialysis monitoring and were treated with induced normothermia for refractory fever (body temperature >or=38.3 degrees C, despite antipyretics), were studied. Levels of microdialysate lactate/pyruvate ratio (LPR) and episodes of cerebral metabolic crisis (LPR >40) were analyzed during fever and induced normothermia, at normal and high ICP (>20 mm Hg). RESULTS Compared to fever, induced normothermia resulted in lower LPR (40+/-24 versus 32+/-9, P<0.01) and a reduced incidence of cerebral metabolic crisis (13% versus 5%, P<0.05) at normal ICP. During episodes of high ICP, induced normothermia was associated with a similar reduction of LPR, fewer episodes of cerebral metabolic crisis (37% versus 8%, P<0.01), and lower ICP (32+/-11 versus 28+/-12 mm Hg, P<0.05). CONCLUSIONS Fever control is associated with reduced cerebral metabolic distress in patients with SAH, irrespective of ICP.

Detection of cerebral compromise with multimodality monitoring in patients with subarachnoid hemorrhage.

BACKGROUND:Studies in traumatic brain injury suggest that monitoring techniques such as brain tissue oxygen (Pbto2) and cerebral microdialysis may complement conventional intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements. OBJECTIVE:In this study of poor-grade (Hunt and Hess grade IV and V) subarachnoid hemorrhage (SAH) patients, we examined the prevalence of brain hypoxia and brain energy dysfunction in the presence of normal and abnormal ICP and CPP. METHODS:SAH patients who underwent multimodal neuromonitoring and cerebral microdialysis were studied. We examined the frequency of brain hypoxia and energy dysfunction in different ICP and CPP ranges and the relationship between Pbto2 and the lactate/pyruvate ratio (LPR). RESULTS:A total of 2394 samples from 19 patients were analyzed. There were 149 samples with severe brain hypoxia (Pbto2 ≤10 mm Hg) and 347 samples with brain energy dysfunction (LPR >40). The sensitivities of abnormal ICP or CPP for elevated LPR and reduced Pbto2 were poor (21.2% at best), and the LPR or Pbto2 was abnormal in many instances when ICP or CPP was normal. Severe brain hypoxia was often associated with an LPR greater than 40 (86% of samples). In contrast, mild brain hypoxia (≤20 mm Hg) and severe brain hypoxia were observed in only 53% and 36% of samples with brain energy dysfunction, respectively. CONCLUSION:Our data demonstrate that ICP and CPP monitoring may not always detect episodes of cerebral compromise in SAH patients. Our data suggest that several complementary monitors may be needed to optimize the care of poor-grade SAH patients.

Brain oxygen tension and outcome in patients with aneurysmal subarachnoid hemorrhage.

OBJECT Poor outcome is common after aneurysmal subarachnoid hemorrhage (SAH). Clinical studies suggest that cerebral hypoxia after traumatic brain injury is associated with poor outcome. In this study we examined the relationship between brain oxygen tension (PbtO(2)) and death after aneurysmal SAH. METHODS Forty-six patients, including 34 women and 12 men (Glasgow Coma Scale Score < or = 8 and median age 58.5 years) who underwent PbtO(2) monitoring were studied prospectively during a 2-year period in a neurosurgical intensive care unit at a University Level I Trauma Center. Brain oxygen tension, intracranial pressure (ICP), mean arterial pressure, cerebral perfusion pressure (CPP), and brain temperature were continuously monitored, and treatment was directed toward ICP, CPP, and PbtO(2) targets. The relationship between PbtO(2) and 1-month survival was examined. RESULTS Data were available from 5424 hours of PbtO(2) monitoring. For the entire cohort the mean ICP, CPP, and PbtO(2) were 13.85 +/- 2.40, 84.05 +/- 3.41, and 30.79 +/- 1.91 mm Hg, respectively. Twenty-five patients died (54%). The mean daily PbtO(2) was higher in survivors than nonsurvivors (33.94 +/- 2.74 vs 28.14 +/- 2.59 mm Hg; p = 0.05). In addition, survivors had significantly shorter episodes of compromised PbtO(2) (defined as 15-25 mm Hg) than nonsurvivors (125.85 +/- 15.44 vs 271.14 +/- 55.23 minutes; p < 0.01). Intracranial pressure was similar in survivors and nonsurvivors. In contrast, the average CPP was significantly lower in nonsurvivors than survivors (76.96 +/- 5.50 vs 92.49 +/- 2.75 mm Hg; p = 0.01). When PbtO(2) was stratified according to CPP level, survivors had higher PbtO(2) levels. Following logistic regression, the number of episodes of compromised PbtO(2) (odds ratio 1.1, 95% confidence interval 1.003-1.2) and number of episodes of cerebral hypoxia (< 15 mm Hg; odds ratio 1.3, 95% confidence interval 1.0-1.7) were more frequent in those who died. CONCLUSIONS Patient deaths after SAH may be associated with a lower mean PbtO(2) and longer periods of compromised cerebral oxygenation than in survivors. This knowledge may be used to help direct therapy.

Endovascular and surgical treatment of ruptured cerebral aneurysms in pediatric patients.

OBJECTIVEPediatric cerebral aneurysms are rare. There are very few recent studies that focus on the multidisciplinary treatment of ruptured aneurysms. We reviewed our pediatric endovascular and surgical experience with ruptured cerebral aneurysms. METHODSPediatric patients aged 16 years and younger who were admitted with a diagnosis of aneurysmal subarachnoid hemorrhage and treated at the Childrens Hospital of Philadelphia were included in this analysis. RESULTSTwelve patients with 13 aneurysms (4 male patients and 8 female patients; age range, 4 months–16 years; mean age, 5.1 years), were admitted with subarachnoid hemorrhage during the past 12 years. The majority of patients were admitted in good clinical condition; 31% were in Hunt and Hess Grade II, and 31% were in Hunt and Hess Grade III. The remaining patients were in poor clinical condition and were in Hunt and Hess Grade IV (23%) or Grade V (15%). Computed tomography revealed that 15% of the patients were in Fisher Grade 2, 23% were in Fisher Grade 3, and 62% were in Fisher Grade 4. Endovascular techniques were used in the treatment of 5 aneurysms, and microsurgery was used in the treatment of 8 aneurysms. In the endovascular group, aneurysm sizes ranged from 2 to 35 mm (mean, 12.6 mm); 3 aneurysms were in the anterior circulation, and 2 were in the posterior circulation. In the microsurgery group, 6 aneurysms were in the anterior circulation, and 2 were in the posterior circulation; sizes ranged from 3 to 15 mm (mean, 6.8 mm). Sixty-nine percent of the patients were independent at follow-up. CONCLUSIONContemporary endovascular and microsurgical techniques can be used effectively to treat ruptured cerebral aneurysms in pediatric patients. In the time period studied, the techniques were equally effective when used in the appropriate patients.

Microthrombosis after experimental subarachnoid hemorrhage: time course and effect of red blood cell-bound thrombin-activated pro-urokinase and clazosentan.

Delayed cerebral ischemia (DCI) is a significant cause of morbidity and mortality for patients surviving the rupture of an intracranial aneurysm. Despite an association between vasospasm and DCI, thrombosis and thromboembolism may also contribute to DCI. In this study we investigate the time course of intravascular microclot formation after experimental subarachnoid hemorrhage (SAH) and assess the effects of the following two drugs on microclot burden: mutant thrombin-activated urokinase-type plasminogen activator (scFv/uPA-T), which is bound to red blood cells for use as a thromboprophylactic agent, and clazosentan, an endothelin antagonist. In the first study, adult male C57BL/6 mice were sacrificed at 24 (n=5), 48 (n=6), 72 (n=8), and 96 (n=3) hours after SAH induced by filament perforation of the anterior cerebral artery. Sham animals (n=5) underwent filament insertion without puncture. In the second study, animals received scFv/uPA-T (n=5) 3 hours after hemorrhage, clazosentan (n=5) by bolus and subcutaneous pump after SAH just prior to skin closure, or a combination of scFv/uPA-T and clazosentan (n=4). Control (n=6) and sham (n=5) animals received saline alone. All animals were sacrificed at 48 hours and underwent intra-cardiac perfusion with 4% paraformaldehyde. The brains were then extracted and sliced coronally on a cryostat and processed for immunohistochemistry. An antibody recognizing thrombin-anti-thrombin complexes was used to detect microclots on coronal slices. Microclot burden was calculated for each animal and compared among groups. Following SAH, positive anti-thrombin staining was detected bilaterally in the following brain regions, in order of decreasing frequency: cortex; hippocampus; hypothalamus; basal ganglia. Few microclots were found in the shams. Microclot burden peaked at 48 hours and then decreased gradually. Animals receiving scFv/uPA-T and scFv/uPA-T+clazosentan had a lower microclot burden than controls, whereas animals receiving clazosentan alone had a higher microclot burden (p<0.005). The overall mortality rate in the time course study was 40%; mortality was highest among control animals in the second study. Intravascular microclots form in a delayed fashion after experimental SAH. Microclots may be safely reduced using a novel form of thromboprophylaxis provided by RBC-targeted scFv/uPA-T and represent a potential target for therapeutic intervention in the treatment of DCI.