Marked hemodilution increases neurologic injury after focal cerebral ischemia in rabbits

Iatrogenic air embolism: pathoanatomy, thromboinflammation, endotheliopathy, and therapies

Iatrogenic vascular air embolism is a relatively infrequent event but is associated with significant morbidity and mortality. These emboli can arise in many clinical settings such as neurosurgery, cardiac surgery, and liver transplantation, but more recently, endoscopy, hemodialysis, thoracentesis, tissue biopsy, angiography, and central and peripheral venous access and removal have overtaken surgery and trauma as significant causes of vascular air embolism. The true incidence may be greater since many of these air emboli are asymptomatic and frequently go undiagnosed or unreported. Due to the rarity of vascular air embolism and because of the many manifestations, diagnoses can be difficult and require immediate therapeutic intervention. An iatrogenic air embolism can result in both venous and arterial emboli whose anatomic locations dictate the clinical course. Most clinically significant iatrogenic air emboli are caused by arterial obstruction of small vessels because the pulmonary gas exchange filters the more frequent, smaller volume bubbles that gain access to the venous circulation. However, there is a subset of patients with venous air emboli caused by larger volumes of air who present with more protean manifestations. There have been significant gains in the understanding of the interactions of fluid dynamics, hemostasis, and inflammation caused by air emboli due to in vitro and in vivo studies on flow dynamics of bubbles in small vessels. Intensive research regarding the thromboinflammatory changes at the level of the endothelium has been described recently. The obstruction of vessels by air emboli causes immediate pathoanatomic and immunologic and thromboinflammatory responses at the level of the endothelium. In this review, we describe those immunologic and thromboinflammatory responses at the level of the endothelium as well as evaluate traditional and novel forms of therapy for this rare and often unrecognized clinical condition.

Gas embolism during endoscopic retrograde cholangiopancreatography: diagnosis and management

Air embolism is rarely diagnosed and is often fatal. The diagnosis is often not made in a timely manner given the rapid and severe clinical deterioration that often develops, frequently leading to cardiac arrest. Many patients are only diagnosed post-mortem. With the increasing use of endoscopic retrograde cholangiopancreatography, air embolism should be considered in the differential diagnosis in patients who experience sudden clinical deterioration during or immediately after the procedure. Clinical suspicion is key in the diagnosis and management of air embolism. Use of precordial Doppler ultrasound and transesophageal echocardiogram can aid in the diagnosis of air embolism. Once the diagnosis is made, supportive management of airway, breathing and circulation is pivotal. Advanced cardiac life support should be initiated when necessary. Fluid resuscitation and vasopressors can improve cardiac output. Hyperbaric oxygen therapy should be considered when possible in cases of suspected cerebral air embolism cases to improve neurological outcome. A multidisciplinary team approach and effective communication with experts, potentially including an anesthesiologist, cardiologist, intensivist, radiologist and surgeon, can improve the outcome in air embolism.

Red blood cell transfusion in acute brain injury subtypes: An observational cohort study

PURPOSE

Optimal red blood cell (RBC) transfusion thresholds in acute brain injury (ABI) are poorly defined.

MATERIALS AND METHODS

We conducted a retrospective cohort study of adult patients with ABI and moderate anemia (Hb 7-10 g/dL) in a neurological intensive care unit (ICU) at an academic medical center between 2008 and 2015. Transfused and non-transfused patients were matched based on age, ABI subtype, pre-transfusion hemoglobin, and ICU length of stay (LOS) at the time of RBC transfusion. Multivariable regression analyses were performed to assess the relationship between RBC transfusion and hospital LOS, hospital mortality, ICU LOS, ICU mortality, and 24 h change in sequential organ failure assessment (SOFA) scores.

RESULTS

2638 patients met inclusion criteria, with 225 (8.5%) receiving RBC transfusion. Acute ischemic stroke was the most prevalent ABI diagnosis (43.3%) then intracranial hemorrhage (25.6%), subarachnoid hemorrhage (16.5%), and traumatic brain injury (TBI) (14.6%). In multivariable analyses, RBC transfusion was associated with longer hospital and ICU LOS, and higher SOFA scores. Each ABI subtype had similar results, except for TBI which showed no difference in hospital LOS. Mortality was not significantly different.

CONCLUSIONS

In moderately anemic patients with ABI, RBC transfusion was associated with longer hospital and ICU LOS. Prospective investigations are necessary to further assess these relationships.

Association of anemia and hemoglobin decrease during acute stroke treatment with infarct growth and clinical outcome

Background and purpose

Anemia is associated with worse outcome in stroke, but the impact of anemia with intravenous thrombolysis or endovascular therapy has hardly been delineated. The aim of this study was to analyze the role of anemia on infarct evolution and outcome after acute stroke treatment.

Methods

1158 patients from Bern and 321 from Los Angeles were included. Baseline data and 3 months outcome assessed with the modified Rankin Scale were recorded prospectively. Baseline DWI lesion volumes were measured in 345 patients and both baseline and final infarct volumes in 180 patients using CT or MRI. Multivariable and linear regression analysis were used to determine predictors of outcome and infarct growth.

Results

712 patients underwent endovascular treatment and 446 intravenous thrombolysis. Lower hemoglobin at baseline, at 24h, and nadir until day 5 predicted poor outcome (OR 1.150–1.279) and higher mortality (OR 1.131–1.237) independently of treatment. Decrease of hemoglobin after hospital arrival, mainly induced by hemodilution, predicted poor outcome and had a linear association with final infarct volumes and the amount and velocity of infarct growth. Infarcts of patients with newly observed anemia were twice as large as infarcts with normal hemoglobin levels.

Conclusion

Anemia at hospital admission and any hemoglobin decrease during acute stroke treatment affect outcome negatively, probably by enlarging and accelerating infarct growth. Our results indicate that hemodilution has an adverse effect on penumbral evolution. Whether hemoglobin decrease in acute stroke could be avoided and whether this would improve outcome would need to be studied prospectively.

Evaluation of neuronal apoptosis precursors in an experimental model of acute normovolemic hemodilution

Background

The effects of acute anemia on neuronal cells and the safe limits of hematocrit are not well established. The objective of this study was to evaluate neuronal pro- and anti-apoptotic Bax and Bcl-x proteins, caspase-3 and -9 activity, and DNA fragmentation after acute normovolemic hemodilution (ANH).

Methods

Twenty-four pigs were anesthetized and randomized into 4 groups: Sham, ANH to 15% hematocrit (ANH15%), ANH to 10% hematocrit (ANH10%) and hypoxia (Hx). ANH was achieved by simultaneous blood withdrawal and hydroxyethyl starch infusion. Hx consisted of ventilation with a 6% inspired oxygen fraction for 60 minutes. Bax and Bcl-x proteins as well as DNA fragmentation were evaluated in cortical nuclear and mitochondrial fractions. Caspase-3 and -9 activity was evaluated in the cortical mitochondrial and hippocampal cytosolic fractions. The data were compared using analysis of variance followed by Tukey’s test (P<0.05).

Results

No changes were observed in Bax protein expression after hemodilution in the ANH15% and ANH10% groups compared to the Sham group. Bax expression in the Hx group was increased in the nuclear and mitochondrial fractions compared to all other groups. No significant difference was observed in Bcl-x expression. Caspase-3 and -9 activity in the cytosolic and mitochondrial fractions was different in the Hx group compared to all other groups. No statistical significance in DNA fragmentation was found among the Sham, ANH15% or ANH10% groups.

Conclusion

ANH to 10 and 15% hematocrit did not induce alterations in apoptosis precursors, suggesting that cerebral oxygenation was preserved during these anemic states.

Loss of Penumbra by Impaired Oxygen Supply? Decreasing Hemoglobin Levels Predict Infarct Growth after Acute Ischemic Stroke: Stroke: Relevant Impact of Hemoglobin, Hematocrit and Transfusion (STRAIGHT) - An Observational Study

Background

The association of mortality and poor outcome with reduced levels of hemoglobin (Hb) and hematocrit (Hct) in patients admitted for ischemic stroke was recently demonstrated. The mechanisms behind this have remained unclear.

Aims

Here, we aimed to investigate a putative association between low Hb and Hct levels and infarct growth.

Methods

All consecutive patients who received intravenous thrombolysis based on multimodal magnetic resonance imaging during the years 1998–2009 were screened. Laboratory data as well as admission magnetic resonance images and follow-up computed tomography scans of 257 patients were assessed. Overall, data of 100 patients were of sufficient quality and further analyzed.

Results

Decrease in Hb and Hct as well as perfusion-weighted imaging volume, mismatch volume, and final infarct size on follow-up computed tomography were associated with infarct growth. A linear regression model revealed Hb decrease (β = 0.23, p = 0.02) to be a predictor of infarct growth, independent of mismatch volume (β = 0.27, p = 0.004) and minimum sodium (β = -0.21, p = 0.03), and adjusted to the non-predicting variables age, National Institute of Health Stroke Scale score, maximum leucocytes and C-reactive protein, blood glucose, and Hct decrease.

Conclusion

Hb levels that decrease after admission independently predict infarct growth in thrombolyzed stroke patients. The clinical implications of this relationship remain to be investigated.

Lower hemoglobin correlates with larger stroke volumes in acute ischemic stroke

Background

Hemoglobin tetramers are the major oxygen-carrying molecules within the blood. We hypothesized that a lower hemoglobin level and its reduced oxygen-carrying capacity would associate with larger infarction in acute ischemic stroke patients.

Methods

We studied 135 consecutive patients with acute ischemic stroke and perfusion brain MRI. We explored the association of admission hemoglobin with initial infarct volumes on acute images and the volume of infarct expansion on follow-up images. Multivariable linear regression was performed to analyze the independent effect of hemoglobin on imaging outcomes.

Results

Bivariate analyses showed a significant inverse correlation between hemoglobin and initial volume in diffusion-weighted imaging (r = −0.20, p = 0.02) and absolute infarct growth (r = −0.20, p = 0.02). Multivariable linear regression modeling revealed that hemoglobin remained independently predictive of larger infarct volumes acutely (p < 0.005) and with greater infarct expansion (p < 0.01) after adjusting for known covariates.

Conclusions

Hemoglobin level at the time of acute ischemic stroke associates with larger infarcts and increased infarct growth. Clarification of the mechanism of this effect may yield novel insights for therapy.

Stroke location and brain function in an embolic rabbit stroke model

PURPOSE

Current rabbit stroke models often depend on symptoms as endpoints for embolization and produce wide variation in location, size, and severity of strokes. In a further refinement of an angiographic embolic stroke model, localized infarctions were correlated to neurologic deficits with the goal to create a rabbit model for long-term studies of therapies after stroke.

MATERIALS AND METHODS

New Zealand White rabbits (4-5 kg; N = 71) had selective internal carotid artery (ICA) angiography and a single clot was injected. At 24 hours, neurologic assessment score (NAS) was measured on an 11-point scale (0, normal; 10, dead). Brains were removed and stained to identify stroke areas. All animals with single strokes (n = 31) were analyzed by specific brain structure involvement, and NAS values were correlated.

RESULTS

Stroke incidence differed by location, with cortex, subcortical, and basal ganglia regions highest. The middle cerebral artery (MCA), at 52%, and anterior cerebral artery (ACA), at 29%, were most commonly involved, with the largest stroke volumes in the ACA distribution. Brainstem and cerebellum strokes had disproportionately severe neurologic deficits, scoring 2.25 +/- 1.0 on the NAS, which represented a significant (P < .02) difference versus cortex (0.5 +/- 0.2), subcortical (1.3 +/- 0.4), and basal ganglia (0.5 +/- 0.3), all in the frontal or parietal regions.

CONCLUSIONS

MCA and ACA distributions included 81% of strokes. These sites were relatively silent (potentially allowing longer-term survival studies) whereas others in the posterior circulation produced disproportionately severe symptoms. Symptoms were not reliable indicators of stroke occurrence, and other endpoints such as imaging may be required. These are important steps toward refinement of the rabbit stroke model.

Low hemoglobin is associated with poor functional outcome after non-traumatic, supratentorial intracerebral hemorrhage

Introduction

The impact of anemia on functional outcome and mortality in patients suffering from non-traumatic intracerebral hemorrhage (ICH) has not been investigated. Here, we assessed the relationship between hemoglobin (HB) levels and clinical outcome after ICH.

Methods

One hundred and ninety six patients suffering from supratentorial, non-traumatic ICH were extracted from our local stroke database (June 2004 to June 2006). Clinical and radiologic computed tomography data, HB levels on admission, mean HB values and nadir during hospital stay were recorded. Outcome was assessed at discharge and 3 months using the modified Rankin score (mRS).

Results

Forty six (23.5%) patients achieved a favorable functional outcome (mRS ≤ 3) and 150 (76.5%) had poor outcome (mRS 4 - 6) at discharge. Patients with poor functional outcome had a lower mean HB (12.3 versus 13.7 g/dl, P < 0.001) and nadir HB (11.5 versus 13.0 g/dl, P < 0.001). Ten patients (5.1%) received red blood cell (RBC) transfusions. In a multivariate logistic regression model, the mean HB was an independent predictor for poor functional outcome at three months (odds ratio (OR) 0.73, 95% confidence interval (CI) 0.58-0.92, P = 0.007), along with National Institute of Health Stroke Scale (NIHSS) at admission (OR 1.17, 95% CI 1.11 - 1.24, P < 0.001), and age (OR 1.08, 95% CI 1.04 - 1.12, P < 0.001).

Conclusions

We report an association between low HB and poor outcome in patients with non-traumatic, supratentorial ICH. While a causal relationship could not be proven, previous experimental studies and studies in brain injured patients provide evidence for detrimental effects of anemia on brain metabolism. However, the potential risk of anemia must be balanced against the risk of harm from red blood cell infusion.

Anemia and red blood cell transfusion in neurocritical care

INTRODUCTION

Anemia is one of the most common medical complications to be encountered in critically ill patients. Based on the results of clinical trials, transfusion practices across the world have generally become more restrictive. However, because reduced oxygen delivery contributes to 'secondary' cerebral injury, anemia may not be as well tolerated among neurocritical care patients.

METHODS

The first portion of this paper is a narrative review of the physiologic implications of anemia, hemodilution, and transfusion in the setting of brain-injury and stroke. The second portion is a systematic review to identify studies assessing the association between anemia or the use of red blood cell transfusions and relevant clinical outcomes in various neurocritical care populations.

RESULTS

There have been no randomized controlled trials that have adequately assessed optimal transfusion thresholds specifically among brain-injured patients. The importance of ischemia and the implications of anemia are not necessarily the same for all neurocritical care conditions. Nevertheless, there exists an extensive body of experimental work, as well as human observational and physiologic studies, which have advanced knowledge in this area and provide some guidance to clinicians. Lower hemoglobin concentrations are consistently associated with worse physiologic parameters and clinical outcomes; however, this relationship may not be altered by more aggressive use of red blood cell transfusions.

CONCLUSIONS

Although hemoglobin concentrations as low as 7 g/dl are well tolerated in most critical care patients, such a severe degree of anemia could be harmful in brain-injured patients. Randomized controlled trials of different transfusion thresholds, specifically in neurocritical care settings, are required. The impact of the duration of blood storage on the neurologic implications of transfusion also requires further investigation.

Transfusion practices for acute traumatic brain injury: a survey of physicians at US trauma centers

PURPOSE

To determine whether physician specialty influences transfusion threshold in patients with acute severe traumatic brain injury (TBI).

METHODS

We surveyed transfusion preferences of chiefs of trauma surgery, chairs of neurosurgery, and surgical and neurosurgical ICU directors at all 187 US Level I trauma centers using a scenario-based, multiple-choice instrument administered by mail. We evaluated the hemoglobin value used as a transfusion threshold for patients with severe acute TBI in several scenarios as well as opinions regarding the rationale for transfusion.

RESULTS

The response rate was 58% (312/534). Mean time in practice was 17 +/- 8 years and 65% were board certified in critical care. Neurosurgeons (NS) used a greater mean hemoglobin threshold for transfusion of TBI patients than trauma surgeons (TS) and non-surgeon intensivists (CC) whether the intracranial pressure was normal (8.3 +/- 1.2, 7.5 +/- 1.0, and 7.5 +/- 0.8 g/dL; NS, TS, and CC, respectively, P < 0.001) or elevated (8.9 +/- 1.1, 8.0 +/- 1.1, and 8.4 +/- 1.1 g/dL; NS, TS, and CC, respectively, P < 0.001). All three groups commonly believed that secondary ischemic injury is an important problem following TBI (74, 66, and 63%, P = 0.32), but fewer NS believed that transfusions have important immunodulatory effects (25, 91, and 83%, P < 0.001).

CONCLUSIONS

Neurosurgeons prefer more liberal transfusion of TBI patients than TS and CC, suggesting that actual practice may depend largely on which specialist is primarily managing care. The observed clinical equipoise would justify a randomized trial of liberal versus restrictive transfusion strategies in patients with TBI.

Clinical Features of Elderly Patients Submitted to Coronary Artery Bypass Graft

OBJECTIVE

To describe the clinical features as well as morbidity and mortality of elderly patients submitted to coronary artery bypass graft (CABG).

DESIGN

Randomized, single-center, observational study.

METHODS

A prospective study was carried out in a tertiary referral teaching hospital (Heart Institute-Brazil). A total of 220 inpatients submitted to elective CABG were evaluated and data collected from the pre-, intra- and postoperative periods.

INSTRUMENTS

The patients were assessed according to the Geriatric Depression Scale. A diagnosis of delirium was determined according to DSM-IV criteria.

RESULTS

Of these 220 patients 64.5% were males and 35.5% females. The mean age was 71 years. The most important preoperative findings were a higher incidence of comorbidities such as hypertension (73%), diabetes mellitus (35%), dyslipidemia (27%), and previous myocardial infarction (41%). The majority of patients were found to have three or more vessels obstructed at angiography (74%). The major intraoperative findings were that a high number of the patients received more than 3 grafts (74%). A large proportion (72%) of patients needed a blood transfusion and the overall incidence of clinical complications was 33%. The overall postoperative mortality rate for this observational study was 5%. A large number of patients presented complications (56%) such as hypotension (22%), atrial fibrillation (22%), and delirium (34%).

CONCLUSIONS

Although elderly patients have a somewhat increased, however acceptable, operative mortality rate, we believe that this patient group can benefit from CABG.