Cerebrovascular resuscitation after polytrauma and fluid restriction

Insights from Rodent Models for Improving Bench-to-Bedside Translation in Traumatic Brain Injury

Road accidents, domestic falls, and persons associated with sports and military services exhibited the concussion or contusion type of traumatic brain injury (TBI) that resulted in chronic traumatic encephalopathy. In some instances, these complex neurological aberrations pose severe brain damage and devastating long-term neurological sequelae. Several preclinical (rat and mouse) TBI models simulate the clinical TBI endophenotypes. Moreover, many investigational neuroprotective candidates showed promising effects in these models; however, the therapeutic success of these screening candidates has been discouraging at various stages of clinical trials. Thus, a correct selection of screening model that recapitulates the clinical neurobiology and endophenotypes of concussion or contusion is essential. Herein, we summarize the advantages and caveats of different preclinical models adopted for TBI research. We suggest that an accurate selection of experimental TBI models may improve the translational viability of the investigational entity.

Animal models of traumatic brain injury: a review of pathophysiology to biomarkers and treatments

Traumatic brain injury (TBI) is one of the main causes of death and disability in both civilian and military population. TBI may occur via a variety of etiologies, all of which involve trauma to the head. However, the neuroprotective drugs which were found to be very effective in animal TBI models failed in phase II or phase III clinical trials, emphasizing a compelling need to review the current status of animal TBI models and therapeutic strategies. No single animal model can adequately mimic all aspects of human TBI owing to the heterogeneity of clinical TBI. However, due to the ethical limitations, it is difficult to precisely emulate the TBI mechanisms that occur in humans. Therefore, many animal models with varying severity and mechanisms of brain injury have been developed, and each model has its own pros and cons in its implementation for TBI research. These challenges pose a need for study of continued TBI mechanisms, brain injury severity, duration, treatment strategies, and optimization of animal models across the neurotrauma research community. The aim of this review is to discuss (1) causes of TBI, (2) its prevalence in military and civilian population, (3) classification and pathophysiology of TBI, (4) biomarkers and detection methods, (5) animal models of TBI, and (6) the advantages and disadvantages of each model and the species used, as well as possible treatments.

Vasopressor Use during Emergency Trauma Surgery

Most evidence suggests early vasopressor use is associated with death after trauma, but no previous study has focused on patients requiring emergency operative intervention (OR). We test the hypothesis that vasopressors are harmful in this population. Records from 746 patients requiring OR from July 2009 to March 2013 were retrospectively reviewed and stratified based on vasopressor use (epinephrine [EPI], phenylephrine, ephedrine, norepinephrine, dobutamine, vasopressin) or no vasopressor use. Vasopressors were administered to 225 patients (30%) during OR; 59 patients (8%) received multiple vasopressors. Patients who received vasopressors were older, more severely injured, had worse vital signs, and increased mortality rate (all P < 0.001). EPI was independently associated with mortality (odds ratio, 6.88; P = 0.001). If patients who received EPI were excluded, there was no difference in mortality between those who received vasopressors alone or in combination and those that did not (5 vs 6%, P = 0.523), although multiple markers of injury severity were worse. We conclude that vasopressor use is relatively common in the most severely injured patients requiring OR and is associated with mortality. EPI is most often used for cardiac arrest, whereas other vasopressors are used for their vasoconstrictive properties. This suggests that, except for EPI, vasopressors during OR are not independently associated with mortality.

Cerebral Blood Flow in Polytrauma: Transcranial Doppler Analysis in a Nonhuman Primate Shock Model

BACKGROUND

In combat-related trauma, resuscitation goals are to attenuate tissue hypoxia and maintain circulation. During hemorrhagic shock, compensatory and autoregulatory mechanisms are activated to preserve cerebral blood flow. Transcranial Doppler (TCD) ultrasonography may be an ideal noninvasive modality to monitor cerebral hemodynamics. Using a nonhuman primate (NHP) model, we attempted to characterize cerebral hemodynamics during polytraumatic hemorrhagic shock using TCD ultrasonography.

MATERIALS AND METHODS

The ophthalmic artery was insonated at multiple time points during varying stages of shock. Hemorrhage was controlled and pressure targeted to 20 mmHg to initiate and maintain the shock period. Mean flow velocity (MFV), peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI), and resistance index (RI) were recorded. Results represent mean ± standard deviation; statistical significance is P < 0.05; n = 12.

RESULTS

Compared to baseline, MFV, PSV, EDV, and RI show significant changes after 60 min of hemorrhagic shock, (9.81 ± 3.60 cm/s; P < 0.01), (21.15 ± 8.59 cm/s; P < 0.01), (5.15 ± 0.21 cm/s; P < 0.01), (0.70 ± 0.11; P < 0.05), respectively. PI did not change during hemorrhagic shock. At end of prehospital care (T30), cerebral flow recovers for MFV, PSV, and RI while EDV remained decreased at T30 (6.15 ± 1.13 cm/s; P < 0.01) and 1 h of simulated transport (T90) (5.87 ± 0.62 cm/s; P < 0.01). Changes in PI at T30 and T90 were not significant. MFV diminished (16.45 ± 3.85 cm/s; P < 0.05) at T90.

CONCLUSIONS

This study establishes baseline and hemorrhagic shock values for NHP cerebral blood flow velocities and cerebrovascular indices. TCD ultrasonography may represent an important area of research for targeted resuscitation investigations using a hemorrhagic shock model in NHPs.

Does Vasopressin Exacerbate Cerebral Edema in Patients with Severe Traumatic Brain Injury?

Arginine vasopressin (AVP) is often used as an alternative pressor to catecholamines (CATs). However, unlike CATs, AVP is a powerful antidiuretic that could promote edema. We tested the hypothesis that AVP promoted cerebral edema and/or increased requirements for osmotherapy, relative to those who received CATs, for cerebral perfusion pressure (CPP) management after traumatic brain injury (TBI). This is a retrospective review of 286 consecutive TBI patients with intracranial pressure monitoring at a single institution from September 2008 to January 2015. Cerebral edema was quantitated using CT attenuation in prespecified areas of gray and white matter. Results: To maintain CPP >60 mm Hg, 205 patients required no vasopressors, 41 received a single CAT, 12 received AVP, and 28 required both. Those who required no pressors were generally less injured; required less hyperosmolar therapy and less total fluid; and had lower plasma Na, lower intracranial pressure, less edema, and lower mortality (all P < 0.05). Edema; daily mean, minimum, and maximum Na levels; and mortality were similar with AVP versus CATs, but the daily requirement of mannitol and 3 per cent NaCl were reduced by 45 and 35 per cent (both P < 0.05). In patients with TBI who required CPP therapy, AVP reduced the requirements for hyperosmolar therapy and did not delay resolution or increase cerebral edema compared with CATs.

Blast Injuries

BACKGROUND

Blast injuries in the United States and worldwide are not uncommon. Partially due to the increasing frequency of both domestic and international terrorist bombing attacks, it is prudent for all emergency physicians to be knowledgeable about blasts and the spectrum of associated injuries.

OBJECTIVE

Our aim was to describe blast physiology, types of blast injuries associated with each body system, and manifestations and management of each injury.

DISCUSSION

Blast injuries are generally categorized as primary to quaternary injuries. Primary injuries result from the effect of transmitted blast waves on gas-containing structures, secondary injuries result from the impact of airborne debris, tertiary injury results from transposition of the entire body due to blast wind or structural collapse, and quaternary injuries include almost everything else. Different body systems are affected and managed differently. Despite previous dogma, multiple studies now show that tympanic membrane perforation is a poor predictor of other blast injury.

CONCLUSIONS

Blast events can produce a myriad of injuries affecting any and every body system. All emergency physicians should be familiar with the presentation and management of these injuries. This knowledge may also be incorporated into triage and discharge protocols guiding management of mass casualty events.

Intravenous fluids in traumatic brain injury: what's the solution?

PURPOSE OF REVIEW

Intravenous fluid is a fundamental component of trauma care and fluid management influences patient outcomes. This narrative review appraises recent clinical studies of fluid therapy in patients with traumatic brain injury (TBI), with respect to its use in volume resuscitation and prevention of secondary injury.

RECENT FINDINGS

Despite the development of level 1 evidence in fluid resuscitation, in patients with TBI key questions concerning optimal composition and volume remain unanswered. In the absence of randomized trials demonstrating patient outcome differences, clinical practice is often based on physiological principles and surrogate endpoints. There is a physiological rationale why excessive fluid administration and positive fluid balance may increase brain swelling and intracranial pressure (ICP); in some patients, a lower cumulative fluid balance may improve outcomes, but limited human data exist. Resuscitation with 4% albumin in TBI patients in ICU worsens mortality, which may be mediated by increased ICP during the first week after injury. Hypertonic saline and mannitol decrease ICP, but may not improve survival or neurological outcomes. Sodium lactate may be a future therapy for treatment and prevention of secondary brain injury.

SUMMARY

In patients with TBI, intravenous fluids are integral to management; they may be both a source of harm and a potential therapy to limit secondary brain injury. They should be prescribed in accordance with other pharmaceutical or therapeutic interventions. Refined usage may improve patient outcomes.

Traumatic brain injury and hemorrhagic shock: evaluation of different resuscitation strategies in a large animal model of combined insults

Traumatic brain injury (TBI) and hemorrhagic shock (HS) are the leading causes of trauma-related mortality and morbidity. Combination of TBI and HS (TBI + HS) is highly lethal, and the optimal resuscitation strategy for this combined insult remains unclear. A critical limitation is the lack of suitable large animal models to test different treatment strategies. We have developed a clinically relevant large animal model of TBI + HS, which was used to evaluate the impact of different treatments on brain lesion size and associated edema. Yorkshire swine (42-50 kg) were instrumented to measure hemodynamic parameters and intracranial pressure. A computer-controlled cortical impact device was used to create a TBI through a 20-mm craniotomy: 15-mm cylindrical tip impactor at 4 m/s velocity, 100-ms dwell time, and 12-mm penetration depth. Volume-controlled hemorrhage was started (40% blood volume) concurrent with the TBI. After 2 h of shock, animals were randomized to one of three resuscitation groups (n = 5/group): (a) normal saline (NS); (b) 6% hetastarch, Hextend (Hex); and (c) fresh frozen plasma (FFP). Volumes of Hex and FFP matched the shed blood, whereas NS was three times the volume. After 6 h of postresuscitation monitoring, brains were sectioned into 5-mm slices and stained with TTC (2,3,5-triphenyltetrazolium chloride) to quantify the lesion size and brain swelling. Combination of 40% blood loss with cortical impact and a period of shock (2 h) resulted in a highly reproducible brain injury. Total fluid requirements were lower in the Hex and FFP groups. Lesion size and brain swelling in the FFP group (2,160 ± 202.63 mm and 22% ± 1.0%, respectively) were significantly smaller than those in the NS group (3,285 ± 130.8 mm3 and 37% ± 1.6%, respectively) (P < 0.05). Hex treatment decreased the swelling (29% ± 1.6%) without reducing the lesion size. Early administration of FFP reduces the size of brain lesion and associated swelling in a large animal model of TBI + HS. In contrast, artificial colloid (Hex) decreases swelling without reducing the actual size of the brain lesion.

Low-Volume Resuscitation for Severe Intraoperative Hemorrhage: A Step in the Right Direction

The impact on outcomes resulting from crystalloids used with hemostatic close ratio resuscitation (HCRR) in intraoperative hemorrhage (IOH) has not been analyzed. We hypothesize a survival advantage in patients with IOH managed with a low-volume resuscitation (LVR) protocol during HCRR. A 4-year case-control study was conducted to determine the impact on mortality of LVR versus conventional resuscitation efforts (CRE) during HCRR. A total of 45 patients managed with a HCRR + LVR protocol (combination Hextend® and 3% hypertonic saline) and 55 historical cohorts managed with HCRR + CRE (lactated Ringer's) were included. Patient demographics, number of intraoperative units of packed red blood cells (PRBCs) and fresh-frozen plasma (FFP) received, and FFP:PRBC ratio were similar between groups. The mean intraoperative fluid volume was 0.76 L in the HCRR + LVR group versus 4.7 L in the HCRR + CRE group ( P = 0.003). In a linear regression model HCRR + LVR versus HCRR + CRE, mean trauma intensive care unit length of stay was ± versus 11 days ( P = 0.009); 30-day overall mortality was 11.1 versus 32.7 per cent ( P = 0.009); perioperative mortality was 2.2 to 10.9 per cent ( P = 0.13); and intensive care unit mortality 8.8 to 21.8 per cent ( P = 0.07). LVR protocol conveyed a survival benefit to patients undergoing HCRR (odds ratio for mortality, 0.07 [95% confidence interval 0.07–0.54]). This is the first civilian study to analyze the impact of LVR in patients managed with HCRR during IOH. Patients with IOH managed with HCRR and a predefined LVR protocol with Hextend® and 3 per cent hypertonic saline had an overall survival advantage and shorter trauma intensive care unit length of stay. LVR can be an effective alternative to CRE when used in combination with HCRR in patients with IOH.

Neurological effects of blast injury

Over the last few years, thousands of soldiers and an even greater number of civilians have suffered traumatic injuries due to blast exposure, largely attributed to improvised explosive devices in terrorist and insurgent activities. The use of body armor is allowing soldiers to survive blasts that would otherwise be fatal due to systemic damage. Emerging evidence suggests that exposure to a blast can produce neurologic consequences in the brain but much remains unknown. To elucidate the current scientific basis for understanding blast-induced traumatic brain injury (bTBI), the NIH convened a workshop in April 2008. A multidisciplinary group of neuroscientists, engineers, and clinicians were invited to share insights on bTBI, specifically pertaining to: physics of blast explosions, acute clinical observations and treatments, preclinical and computational models, and lessons from the international community on civilian exposures. This report provides an overview of the state of scientific knowledge of bTBI, drawing from the published literature, as well as presentations, discussions, and recommendations from the workshop. One of the major recommendations from the workshop was the need to characterize the effects of blast exposure on clinical neuropathology. Clearer understanding of the human neuropathology would enable validation of preclinical and computational models, which are attempting to simulate blast wave interactions with the central nervous system. Furthermore, the civilian experience with bTBI suggests that polytrauma models incorporating both brain and lung injuries may be more relevant to the study of civilian countermeasures than considering models with a neurologic focus alone.

First report on safety and efficacy of hetastarch solution for initial fluid resuscitation at a level 1 trauma center

BACKGROUND

For logistics, the US Army recommends Hextend (Hospira; 6% hetastarch in buffered electrolyte, HET) for battlefield resuscitation. To support this practice, there are laboratory data, but none in humans. To test the hypothesis that HET is safe and effective in trauma, we reviewed our first 6 months of use at a civilian level 1 trauma center.

STUDY DESIGN

From June 2008 to December 2008, trauma patients received standard of care (SOC) +/- 500 to 1,000 mL of HET within 2 hours of admission at surgeon discretion. Each case was reviewed, with waiver of consent.

RESULTS

There were 1,714 admissions; 805 received HET and 909 did not. With HET versus SOC, overall mortality was 5.2% versus 8.9% (p = 0.0035) by univariate analysis. Results were similar after penetrating injury only (p = 0.0016) and in those with severe injury, defined by Glasgow Coma Scale <9 (p = 0.0013) or Injury Severity Score >26 (p = 0.0142). After HET, more patients required ICU admission (40.9% vs. 34.5%; p = 0.0334) and transfusions of blood (34.4% vs. 20.2%; p = 0.0014) or plasma (20.7% vs. 12.2%; p = 0.0251), but there were no treatment-related differences in prothrombin time or partial thromboplastin time. The 24-hour urine outputs and requirements for blood, plasma, and other fluids were similar. However, increased early deaths with SOC implicate possible selection bias. If that factor was controlled for with multivariate analysis, the same trends were present, but the apparent treatment effects of HET were no longer statistically significant.

CONCLUSIONS

In the first trial to date in hemodynamically unstable trauma patients, and the largest trial to date in any population of surgical patients, initial resuscitation with HET was associated with reduced mortality and no obvious coagulopathy. A randomized blinded trial is necessary before these results can be accepted with confidence.

Resuscitation of traumatic brain injury and hemorrhagic shock with polynitroxylated albumin, hextend, hypertonic saline, and lactated Ringer's: Effects on acute hemodynamics, survival, and neuronal death in mice

Outcome after traumatic brain injury (TBI) is worsened by hemorrhagic shock (HS), but the optimal resuscitation approach is unclear. In particular, treatment of TBI patients with colloids remains controversial. We hypothesized that resuscitation with the colloids polynitroxylated albumin (PNA) or Hextend (HEX) is equal or superior to resuscitation with the crystalloids hypertonic (3%) saline (HTS) or lactated Ringer's solution (LR) after TBI plus HS in mice. C57/BL6 mice (n = 30) underwent controlled cortical impact (CCI) and 90 min of volume-controlled HS (2 mL/100 g). The mice were randomized to resuscitation with LR, HEX, HTS, or PNA, followed by 30 min of test fluid administration targeting a mean arterial pressure (MAP) of >50 mm Hg. Shed blood was re-infused to target a MAP >70 mm Hg. At 7 days post-insult, hippocampal neuron counts were assessed in hematoxylin and eosin-stained sections to quantify neuronal damage. Prehospital MAP was higher, and prehospital and total fluid requirements were lower in the PNA and HEX groups (p < 0.05 versus HTS or LR). Also, 7-day survival was highest in the PNA group, but was not significantly different than the other groups. Ipsilateral hippocampal CA1 and CA3 neuron loss did not differ between groups. We conclude that the colloids PNA and HEX exhibited more favorable effects on acute resuscitation parameters than HTS or LR, and did not increase hippocampal neuronal death in this model.

Hemoglobin-based oxygen carrying compound-201 as salvage therapy for severe neuro- and polytrauma (Injury Severity Score = 27-41)

OBJECTIVE

A prehospital trial in trauma patients has been proposed to evaluate Hemopure (hemoglobin glutamer-250 [bovine], hemoglobin-based oxygen carrying compound [HBOC]-201, Biopure). We tested the hypothesis that HBOC-201 would improve cerebrovascular resuscitation in a unique polytrauma model.

DESIGN

Prospective, randomized, blinded animal study.

SUBJECTS

Thirty-two anesthetized swine (42 +/- 1 kg).

INTERVENTIONS

Blunt trauma to the head, right chest, and bilateral femurs (Injury Severity Score = 27-41) with captive bolt guns was followed by hypoventilation. Resuscitation was divided into phases to simulate conventional treatment in the prehospital, emergency room, and early intensive care unit. For 30-60 mins postinjury, 500 mL of either normal saline (control, n = 14) or HBOC-201 (n = 14) was administered. All received similar care thereafter. For 60-120 mins, normal saline maintained systolic arterial pressure >100 mm Hg and heart rate <100 beats/min plus mannitol (250 mg/kg) for intracranial hypertension. For 120-480 mins, phenylephrine, normal saline, and dextrose were administered to maintain cerebral perfusion pressure >70 mm Hg, filling pressure >12 mm Hg, and plasma glucose >60 mg%, respectively. Two formulations of HBOC-201 (average MW = 250 kDa) were tested: one with <3% 65 kDa tetramers (n = 7) and the other with <0.3% 65 kDa tetramers (n = 7).

MEASUREMENTS AND MAIN RESULTS

Injury severity is reflected by the death of 2 of 32 swine within 30 mins. In survivors (n = 30), systolic arterial pressure was 83 +/- 6 mm Hg, heart rate was 115 +/- 5 beats/min, and lactate was 5.8 +/- 0.4 mM. Intracranial pressure rose from 8 +/- 1 to 18 +/- 1 mm Hg and brain tissue PO2 fell from 17 +/- 1 to 2 +/- 1 mm Hg. Without immediate resuscitation, death occurred within 60 mins (n = 2). With normal saline resuscitation (n = 14), systemic hemodynamics, mixed venous oxygen, renal oxygen, portal oxygen, and muscle oxygen corrected but there were four deaths (two at 45 mins, one at 100 mins, and one at 200 mins). Cerebral perfusion pressure was not restored until mannitol and pressor therapy were initiated at 120 mins. In contrast, with HBOC-201 at 30 mins (n = 14), systolic arterial pressure and cerebral perfusion pressure corrected immediately (both p < 0.05) and there were no deaths (p = 0.0978). After 8 hrs, in both groups, cerebral perfusion pressure, systolic arterial pressure, and heart rate were stable; peripheral oxygen saturations were near normal; lactate was cleared; urine output was adequate. However, with HBOC-201, pressor and fluid requirements were reduced by half, which improved intracranial pressure and brain tissue PO2 (all p < 0.05 vs. control). Reducing tetramer content had no significant effect on the actions of HBOC-201.

CONCLUSIONS

1) A single bolus of HBOC-201 at initial resuscitation rapidly restored cerebral perfusion pressure and stabilized hemodynamics with improved intracranial pressure and brain oxygen for the first 8 hrs; and 2) HBOC-201 could be an effective salvage therapy after severe neurotrauma or as a temporizing measure during prolonged transport of a polytrauma patient.