Limiting initial resuscitation of uncontrolled hemorrhage reduces internal bleeding and subsequent volume requirements

NanoGraphene Clot: A New Fibrinogen-Mimic Hemostatic Material

Trauma is the leading cause of death for adults under the age of 44. Internal bleeding remains a significant challenge in medical emergencies, necessitating the development of effective hemostatic materials that could be administered by paramedics before a patient is in the hospital and treated by surgeons. In this study, we introduce a graphene oxide (GO)-based PEGylated synthetic hemostatic nanomaterial with an average size of 211 ± 83 nm designed to target internal bleeding by mimicking the role of fibrinogen. Functionalization of GO-g-PEG with peptides derived from the α-chain of fibrinogen, such as GRGDS, or the γ-chain of fibrinogen, such as HHLGGAKQAGDV:H12, was achieved with peptide loadings of 72 ± 6 and 68 ± 15 μM, respectively. In vitro studies with platelet-rich plasma (PRP) under confinement demonstrated aggregation enhancement of 39 and 24% for GO-g-PEG-GRGDS and GO-g-PEG-H12, respectively, compared to buffer, while adenosine diphosphate (ADP) alone induced a 5% aggregation. Compared to the same materials in the absence of ADP, GO-g-PEG-GRGDS achieved a 47% aggregation enhancement, while GO-g-PEG-H12 a 25% enhancement. This is particularly important for injectable hemostats and highlights the fact that our nanographene-based materials can only act as hemostats in the presence of agonists, reducing the possibility of unwanted clotting during circulation. Further studies on collagen-coated wells under dynamic flow revealed statistically significant augmentation of PRP fluorescence signal using GRGDS- or H12-coated GO-g-PEG compared to controls. Hemolysis studies showed <1% lysis of red blood cells (RBCs) at the highest PEGylated nanographene concentration. Finally, whole human blood coagulation studies reveal faster and more pronounced clotting using our nanohemostats vs PBS control from 3 min and below (blood is clotted with 10% CaCl2 within 4-5 min), with the biggest differences to be shown at 2 and 1 min. At 1 min, the clot weight was found to be ∼45% of that between 4 and 5 min, while no clot was formed in PBS-treated blood. Reduction of CaCl2 to 5 and 3%, or utilization of prostaglandin E1, an anticoagulant, still leads to clots but of smaller weight. The findings highlight the potential of our fibrinogen-mimic PEGylated nanographene as a promising non-hemolytic injectable scaffold for targeting internal bleeding, offering insights into its platelet aggregation capabilities under confinement and under dynamic flow as well as its pronounced coagulation abilities.

A Guide to the Use of Vasopressors and Inotropes for Patients in Shock

Shock is a life-threatening circulatory failure that results in inadequate tissue perfusion and oxygenation. Vasopressors and inotropes are vasoactive medications that are vital in increasing systemic vascular resistance and cardiac contractility, respectively, in patients presenting with shock. To be well versed in using these agents is an important skill to have in the critical care setting where patients can frequently exhibit symptoms of shock. In this review, we will discuss the pathophysiological mechanisms of shock and evaluate the current evidence behind the management of shock with an emphasis on vasopressors and inotropes.

Hypertension during transfer is associated with poor outcomes in unstable patients with ruptured abdominal aortic aneurysm

OBJECTIVE

Limited data exist for optimal blood pressure (BP) management during transfer of patients with ruptured abdominal aortic aneurysm (rAAA). This study evaluates the effects of hypertension and severe hypotension during interhospital transfers in a cohort of patients with rAAA in hemorrhagic shock.

METHODS

We performed a retrospective, single-institution review of patients with rAAA transferred via air ambulance to a quaternary referral center for repair (2003-2019). Vitals were recorded every 5 minutes in transit. Hypertension was defined as a systolic BP of ≥140 mm Hg. The primary cohort included patients with rAAA with hemorrhagic shock (≥1 episode of a systolic BP of <90 mm Hg) during transfer. The primary analysis compared those who experienced any hypertensive episode to those who did not. A secondary analysis evaluated those with either hypertension or severe hypotension <70 mm Hg. The primary outcome was 30-day mortality.

RESULTS

Detailed BP data were available for 271 patients, of which 125 (46.1%) had evidence of hemorrhagic shock. The mean age was 74.2 ± 9.1 years, 93 (74.4%) were male, and the median total transport time from helicopter dispatch to arrival at the treatment facility was 65 minutes (interquartile range, 46-79 minutes). Among the cohort with shock, 26.4% (n = 33) had at least one episode of hypertension. There were no significant differences in age, sex, comorbidities, AAA repair type, AAA anatomic location, fluid resuscitation volume, blood transfusion volume, or vasopressor administration between the hypertensive and nonhypertensive groups. Patients with hypertension more frequently received prehospital antihypertensives (15% vs 2%; P = .01) and pain medication (64% vs 24%; P < .001), and had longer transit times (36.3 minutes vs 26.0 minutes; P = .006). Episodes of hypertension were associated with significantly increased 30-day mortality on multivariable logistic regression (adjusted odds ratio [aOR], 4.71; 95% confidence interval [CI], 1.54-14.39; P = .007; 59.4% [n = 19] vs 40.2% [n = 37]; P = .01). Severe hypotension (46%; n = 57) was also associated with higher 30-day mortality (aOR, 2.82; 95% CI, 1.27-6.28; P = .01; 60% [n = 34] vs 32% [n = 22]; P = .01). Those with either hypertension or severe hypotension (54%; n = 66) also had an increased odds of mortality (aOR, 2.95; 95% CI, 1.08-8.11; P = .04; 58% [n = 38] vs 31% [n = 18]; P < .01). Level of hypertension, BP fluctuation, and timing of hypertension were not significantly associated with mortality.

CONCLUSIONS

Hypertensive and severely hypotensive episodes during interhospital transfer were independently associated with increased 30-day mortality in patients with rAAA with shock. Hypertension should be avoided in these patients, but permissive hypotension approaches should also maintain systolic BPs above 70 mm Hg whenever possible.

C1 Inhibitor Limits Organ Injury and Prolongs Survival in Swine Subjected to Battlefield Simulated Injury

Complement system activation is recognized as a deleterious component of the mammalian physiological response to traumatic injury with severe hemorrhage (TH). Female Yorkshire swine were subjected to a simulated austere prehospital battlefield scenario. Each animal underwent controlled hemorrhage of 22 mL/kg at 100 mL/min rate for approximately 10 min followed by soft tissue injury, femur fracture, and spleen injury. Subsequent blood loss was uncontrolled. Twenty-eight minutes postinjury the animals were randomized into treatment or no treatment with recombinant human C1 esterase inhibitor (C1INH) (500 IU/kg, n = 11) and into receiving or not permissive hypotensive resuscitation (n = 14) with infusion of 45 mL/kg lactated Ringer's solution (2× blood lost). Observation and animal maintenance continued for 6 h at which time the animals had either expired or were euthanized. Heart, lung, and small intestine tissue samples were collected. Pharmacokinetic, hemodynamic, and metabolic parameters as well as survival time, plasma complement activity and tissue deposition, cytokine levels, and tissue injury were determined. We found that administration of C1INH protected tissues from damage, reduced the levels of inflammatory cytokines, and improved blood chemistry. Immunohistochemical analyses revealed that C1INH administration following TH markedly reduced complement activation and deposition in tissues. Importantly, C1INH administration prolonged survival of animals particularly in those which received resuscitation fluid infusion. Our data urge early administration of C1INH to limit organ damage and prolong survival of those injured in the battlefield.

The effect of scene time on survival

A review of the literature was carried out to determine the importance of pre-hospital scene times and how it can be affected. In the UK, and certain centres in North America, mortality and morbidity in critically injured patients appears to be related to scene times. The majority of these patients only require basic life support at the scene. Consequently the possible benefits of more advanced procedure need to be compared with the transportation period, the time needed to mobilize a medical team and skill proficiency. Cardiovascular resuscitation procedures in particular require reappraisal. Though haemostasis is essential, there is little evidence to support the use of fluid resuscitation in nontrapped urban patients with a significant haemorrhage problem. In contrast patients who are not bleeding do appear to benefit from advanced life support procedures even though this increases scene time. There is therefore a need for pre-hospital paramedic workers to triage patients so that appropriate resuscitation can be carried out.

Damage Control Resuscitation

Resuscitation of the hemorrhaging patient has undergone significant changes in the last decade resulting in the concept of damage control resuscitation (DCR). Hemostatic resuscitation aims to address the physiologic derangements found in the hemorrhaging patient, namely coagulopathy, acidosis, and hypothermia. Strategies to achieve this are permissive hypotension, high ratio of plasma and platelet transfusion to packed red blood cell transfusion, and limitation of crystalloid administration. Damage control surgery aims for early hemorrhage control and minimizing operative time by delaying definitive repair until the patient's physiologic status has normalized. Together these strategies constitute DCR and have led to improved outcomes for hemorrhaging patients over the last 2 decades. Recently, DCR has been augmented by both pharmacologic and laboratory adjuncts to improve the care of the hemorrhaging patient. These include thrombelastography as a detailed measure of the clotting cascade, tranexamic acid as an antifibrinolytic, and the procoagulant activated factor VII. In this review, we discuss the strategies that makeup DCR, their adjuncts, and how they fit into the care of the hemorrhaging patient.

Liberal versus restricted fluid resuscitation strategies in trauma patients: a systematic review and meta-analysis of randomized controlled trials and observational studies*

OBJECTIVE

Hemorrhage is responsible for most deaths that occur during the first few hours after trauma. Animal models of trauma have shown that restricting fluid administration can reduce the risk of death; however, studies in patients are difficult to conduct due to logistical and ethical problems. To maximize the value of the existing evidence, we performed a meta-analysis to compare liberal versus restricted fluid resuscitation strategies in trauma patients.

DATA SOURCES

Medline and Embase were systemically searched from inception to February 2013.

STUDY SELECTION

We selected randomized controlled trials and observational studies that compared different fluid administration strategies in trauma patients. There were no restrictions for language, population, or publication year.

DATA EXTRACTION

Four randomized controlled trials and seven observational studies were identified from 1,106 references. One of the randomized controlled trials suffered from a high protocol violation rate and was excluded from the final analysis.

DATA SYNTHESIS

The quantitative synthesis indicated that liberal fluid resuscitation strategies might be associated with higher mortality than restricted fluid strategies, both in randomized controlled trials (risk ratio, 1.25; 95% CI, 1.01-1.55; three trials; I(2), 0) and observational studies (odds ratio, 1.14; 95% CI, 1.01-1.28; seven studies; I(2), 21.4%). When only adjusted odds ratios were pooled for observational studies, odds for mortality with liberal fluid resuscitation strategies increased (odds ratio, 1.19; 95% CI, 1.02-1.38; six studies; I(2), 26.3%).

CONCLUSIONS

Current evidence indicates that initial liberal fluid resuscitation strategies may be associated with higher mortality in injured patients. However, available studies are subject to a high risk of selection bias and clinical heterogeneity. This result should be interpreted with great caution.

Hypotensive Resuscitation

Hypotensive resuscitation is a component of damage control resuscitation, the evolving approach to resuscitation in severely injured trauma patients. Resuscitation strategies used in treating severely injured trauma patients have changed dramatically over the last 20 years. The purpose of this review is to examine the current literature pertaining to hypotensive resuscitation, explore its use in damage control resuscitation, and examine blood pressure management in the setting of severe trauma.

A pilot comparison of limited versus large fluid volume resuscitation in canine spontaneous hemoperitoneum

Treatment for hemorrhagic shock secondary to a spontaneous hemoperitoneum includes restoration of IV volume and surgical control of hemorrhage. This study was designed to determine if limited fluid volume resuscitation (LFVR) with hypertonic saline (HS) and hyperoncotic fluids (hydroxyethylstarch [HES]) results in more rapid cardiovascular stabilization in dogs with spontaneous hemoperitoneum versus conventional resuscitation (CR) with large volume resuscitation. Eighteen client-owned dogs presenting in hemorrhagic shock with a spontaneous hemoperitoneum were enrolled. Dogs were randomized to be fluid resuscitated with up to 90 mL/kg of an isotonic crystalloid (CR group) or up to 8 mL/kg of 7.2% Na chloride (i.e., HS) combined with up to 10 mL/kg of 6% HES. Measurements of vital signs, lactate, packed cell volume (PCV), total solids (TS), and blood pressure were made at standard time points. The primary end point was time to stabilization of hemodynamic parameters (measured in min). Dogs in the LFVR group achieved hemodynamic stabilization significantly faster (20 min; range, 10-25 min) than those in the CR group (35 min; range, 15-50 min; P = .027). Future studies are warranted to further investigate potential benefits associated with LFVR in dogs with spontaneous hemoperitoneum.

p-Hydroxyphenylpyruvate, an intermediate of the Phe/Tyr catabolism, improves mitochondrial oxidative metabolism under stressing conditions and prolongs survival in rats subjected to profound hemorrhagic shock

The aim of this study was to test the effect of a small volume administration of p-hydroxyphenylpyruvate (pHPP) in a rat model of profound hemorrhagic shock and to assess a possible metabolic mechanism of action of the compound. The results obtained show that hemorrhaged rats treated with 2–4% of the estimated blood volume of pHPP survived significantly longer (p<0.001) than rats treated with vehicle. In vitro analysis on cultured EA.hy 926 cells demonstrated that pHPP improved cell growth rate and promoted cell survival under stressing conditions. Moreover, pHPP stimulated mitochondria-related respiration under ATP-synthesizing conditions and exhibited antioxidant activity toward mitochondria-generated reactive oxygen species. The compound effects reported in the in vitro and in vivo analyses were obtained in the same millimolar concentration range. These data disclose pHPP as an efficient energetic substrates-supplier to the mitochondrial respiratory chain as well as an antioxidant supporting the view that the compound warrants further evaluation as a therapeutic agent.

Traumatic coagulopathy--part 2: Resuscitative strategies

OBJECTIVE

To discuss the current resuscitative strategies for trauma-induced hemorrhagic shock and acute traumatic coagulopathy (ATC).

ETIOLOGY

Hemorrhagic shock can be acutely fatal if not immediately and appropriately treated. The primary tenets of hemorrhagic shock resuscitation are to arrest hemorrhage and restore the effective circulating volume. Large volumes of isotonic crystalloids have been the resuscitative strategy of choice; however, data from experimental animal models and retrospective human analyses now recognize that large-volume fluid resuscitation in uncontrolled hemorrhage may be deleterious. The optimal resuscitative strategy has yet to be defined. In human trauma, implementing damage control resuscitation with damage control surgery for controlling ongoing hemorrhage, acidosis, and hypothermia; managing ATC; and restoring effective circulating volume is emerging as a more optimal resuscitative strategy. With hyperfibrinolysis playing an integral role in the manifestation of ATC, the use of antifibrinolytics (eg, tranexamic acid and aminocaproic acid) may also serve a beneficial role in the early posttraumatic period. Considering the sparse information regarding these resuscitative techniques in veterinary medicine, veterinarians are left with extrapolating information from human trials and experimental animal models.

DIAGNOSIS

Viscoelastic tests integrated with predictive scoring systems may prove to be the most reliable methods for early detection of ATC as well as for guiding transfusion requirements.

SUMMARY

Hemorrhage accounts for up to 40% of human trauma-related deaths and remains the leading cause of preventable death in human trauma. The exact proportion of trauma-related deaths due to exsanguinations in veterinary patients remains uncertain. Survivability depends upon achieving rapid definitive hemostasis, early attenuation of posttraumatic coagulopathy, and timely restoration of effective circulating volume. Early institution of damage control resuscitation in severely injured patients with uncontrolled hemorrhage has the ability to curtail posttraumatic coagulopathy and the exacerbation of metabolic acidosis and hypothermia and improve survival until definitive hemostasis is achieved.

Effects of fibrinogen concentrate after shock/resuscitation: a comparison between in vivo microvascular clot formation and thromboelastometry*

OBJECTIVES

Dilutional coagulopathy after resuscitation with crystalloids/colloids clinically often appears as diffuse microvascular bleeding. Administration of fibrinogen reduces bleeding and increases maximum clot firmness, measured by thromboelastometry. Study objective was to implement a model where microvascular bleeding can be directly assessed by visualizing clot formation in microvessels, and correlations can be made to thromboelastometry.

DESIGN

Randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Male Syrian Golden hamsters.

INTERVENTIONS

Microvessels of Syrian Golden hamsters fitted with a dorsal window chamber were studied using videomicroscopy. After 50% hemorrhage followed by 1 hour of hypovolemia resuscitation with 35% of blood volume using a high-molecular-weight hydroxyethyl starch solution (Hextend, Hospira, MW 670 kD) occurred. Animals were then treated with 250 mg/kg fibrinogen IV (Laboratoire français du Fractionnement et des Biotechnologies, Paris, France) or an equal volume of saline before venular vessel wall injuries was made by directed laser irradiation, and the ability of microthrombus formation was assessed.

MEASUREMENTS AND MAIN RESULTS

Thromboelastometric measurements of maximum clot firmness were performed at the beginning and at the end of the experiment. Resuscitation with hydroxyethyl starch and sham treatment significantly decreased FIBTEM maximum clot firmness from 32 ± 9 mm at baseline versus 13 ± 5 mm after sham treatment (p < 0.001). Infusion of fibrinogen concentrate significantly increased maximum clot firmness, restoring baseline levels (baseline 32 ± 9 mm; after fibrinogen administration 29 ± 2 mm). In vivo microthrombus formation in laser-injured vessels significantly increased in fibrinogen-treated animals compared with sham (77% vs 18%).

CONCLUSIONS

Fibrinogen treatment leads to increased clot firmness in dilutional coagulopathy as measured with thromboelastometry. At the microvascular level, this increased clot strength corresponds to an increased prevalence of thrombus formation in vessels injured by focused laser irradiation.

The clinical effectiveness of permissive hypotension in blunt abdominal trauma with hemorrhagic shock but without head or spine injuries or burns: a systematic review

Background

Trauma is a major cause of death and disability. The current trend in trauma management is the rapid administration of fluid as per the Advanced Trauma Life Support guidelines, although there is no evidence to support this and even some to suggest it might be harmful. Some guidelines, protocols, and recommendations have been established for the use of permissive hypotension although there is reluctance concerning its application in blunt injuries.

Objectives

The aim of this review is to determine whether there is evidence of the use of permissive hypotension in the management of hemorrhagic shock in blunt trauma patients. This review also aims to search for any reason for the reluctance to apply permissive hypotension in blunt injuries.

Methods

This systematic review has followed the steps recommended in the Cochrane Handbook for Systematic Reviews of Interventions. It is also being reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement and checklist. Database searches of MEDLINE, EMBASE, the Centre for Reviews and Dissemination databases and the Cochrane Library were made for eligible studies as well as journal searches. Inclusion criteria included systematic reviews that have similar primary questions to this review and randomized controlled trials where patients with blunt torso injuries and hemorrhagic shock were not excluded. Rapid or early fluid administration was compared with controlled or delayed fluid resuscitation and a significant outcome was obtained.

Results

No systematic reviews attempting to answer similar questions were found. Two randomized controlled trials with mixed types of injuries in the included patients found no significant difference between the groups used in each study. Data concerning the question of this review was sought after these papers were appraised.

Conclusion

The limited available data are not conclusive. However, the supportive theoretical concept and laboratory evidence do not show any reason for treating blunt injuries differently from other traumatic injuries. Moreover, permissive hypotension is being used for some nontraumatic causes of hemorrhagic shock and in theater. Therefore, this should encourage interested researchers to continue clinical work in this important field.

Intravenous fluid resuscitation for the trauma patient

PURPOSE OF REVIEW

Although longstanding practice in trauma care has been to provide immediate, aggressive intravenous fluid resuscitation to injured patients with presumed internal hemorrhage, recent experimental and clinical data suggest a more discriminating approach that first considers concurrent head injury, hemodynamic stability, and the presence of potentially uncontrollable hemorrhage (e.g., deep truncal injury) versus a controllable source (e.g., distal extremity wound).

RECENT FINDINGS

The data suggest that rapid intravenous fluid infusions could be used for patients with isolated extremity, thermal or head injury. However, intravenous fluids should be limited in conditions with potentially uncontrollable internal hemorrhage, and particularly in patients with penetrating truncal injury being transported immediately to a trauma center. Likewise, positive pressure ventilatory support should be limited with severe hemorrhage due to the secondary reductions in venous return off-setting the effects of the fluids. For trauma patients with severe bleeding, there is growing evidence for the increased use of plasma and factor VIIa, as well as tourniquets, intra-osseus devices, and evolving monitoring techniques.

SUMMARY

Future research efforts in trauma should focus on the timing and rate of infusions as well as the concept of infusing alternative intravenous resuscitative fluids such as hemoglobin-based oxygen carriers (HBOCs) and the use of hemostatic agents and special blood products.

Study of placing a second intravenous line in trauma

OBJECTIVE

We evaluated the benefit of emergency medical services providers' placing a second intravenous (IV) line in the prehospital trauma setting. Our hypothesis was that the placement of a second IV catheter in trauma does not result in an improvement in heart rate, blood pressure, rehospitalizaton rate, or 30-day mortality.

METHODS

A retrospective chart review of 320 trauma patients in a one-year period was conducted at our level I trauma center. All trauma patients who had vascular access obtained prehospitally were included.

RESULTS

Patients with two IV lines received an average of 348.4 mL more fluid (95% confidence interval [CI]: 235.6, 461.1; p < 0.0001). No change in heart rate, pulse oximetry, Glasgow Coma Scale score, systolic blood pressure, rehospitalization rate, or 30-day mortality was noted. These effects persisted for patients who were initially tachycardic (heart rate 3.92 bpm; 95% CI ?3.01, 10.82; p = 0.27) or hypotensive (blood pressure 22.00 mmHg; 95% CI ?4.17, 48.16; p = 0.10).

CONCLUSIONS

Redundant prehospital IV lines provided no noticeable benefit in physiologic support for trauma patients. When controlling for confounding variables, no significant outcome difference was noted, even in the hypotensive patients. The traditional approach for establishment of a secondary IV line in prehospital trauma patients should not be followed in a dogmatic fashion.

Current concepts in resuscitation

Early recognition and differentiation of shock, as well as goal-directed resuscitation, are fundamental principles in the care of the critically ill or injured patient. Substantial progress has been made over the last decade in the understanding of both shock and resuscitation. Specific areas of advancement, particularly pertaining to hemorrhagic shock, include a heightened appreciation of dynamic measurements of preload responsiveness (e.g., respiratory-induced pulse pressure and venous diameter variability), an improved awareness of the detrimental effects of blood product transfusion, and better recognition of the complications of overzealous volume expansion. However, several areas of controversy remain regarding the optimal resuscitation strategy. These include the optimal targets for perfusion pressure and oxygen delivery, endpoints of resuscitation, resuscitative fluid, and transfusion strategies for packed red blood cells and blood products. This article reviews the diagnosis and differentiation of shock, measurements of tissue perfusion, current evidence regarding various resuscitative techniques, and complications of resuscitation.

A small dose of arginine vasopressin in combination with norepinephrine is a good early treatment for uncontrolled hemorrhagic shock after hemostasis

BACKGROUND

Limited fluid resuscitation has been proven to have a good effect on uncontrolled hemorrhagic shock. Arginine vasopressin (AVP) and norepinephrine (NE) were used to treat vasodilatory or septic shock, and were used to reduce the fluid requirement for uncontrolled hemorrhagic shock. Based on their pressor and hemodynamic stabilization effects, it is speculated that AVP and NE may be a good treatment for uncontrolled hemorrhagic shock at early stage after hemostasis.

METHODS

Experiments were conducted in two parts. Each part had control, lactated Ringer's solution (LR), whole blood, NE, arginine vasopressin (AVP), NE+AVP, and AVP+NE+whole blood. Rats (n = 8-10/group), respectively, received LR, whole blood, NE (1 μg/kg) and AVP (0.1 U/kg) infusion alone, or in combination after 60 min hypotensive resuscitation (50 mmHg). The volume in each group was two times the volume of shed blood.

RESULTS

Whole blood improved all observed parameters, particularly the tissue blood flow and mitochondrial function of liver and kidney, and the 12-h survival (50%). NE only increased the hemodynamics. 0.1 U/kg of AVP had a similar effect with whole blood on hemodynamics, tissue blood flow, mitochondrial function, and the 12-h survival. AVP+NE significantly improved all observed variables (P < 0.05 or 0.01), the 12-h survival was 70%. Whole blood further potentiated the beneficial effect of AVP+NE, and 12-h animal survival rate in this group was 80%.

CONCLUSION

AVP+NE is a good treatment for uncontrolled hemorrhagic shock at the early stage after hemostasis if blood is unavailable. Whole blood transfusion can potentiate this beneficial effect of AVP+NE.

Prehospital management of traumatic brain injury

The aim of this study was to review the current protocols of prehospital practice and their impact on outcome in the management of traumatic brain injury. A literature review of the National Library of Medicine encompassing the years 1980 to May 2008 was performed. The primary impact of a head injury sets in motion a cascade of secondary events that can worsen neurological injury and outcome. The goals of care during prehospital triage, stabilization, and transport are to recognize life-threatening raised intracranial pressure and to circumvent cerebral herniation. In that process, prevention of secondary injury and secondary insults is a major determinant of both short- and longterm outcome. Management of brain oxygenation, blood pressure, cerebral perfusion pressure, and raised intracranial pressure in the prehospital setting are discussed. Patient outcomes are dependent upon an organized trauma response system. Dispatch and transport timing, field stabilization, modes of transport, and destination levels of care are addressed. In addition, special considerations for mass casualty and disaster planning are outlined and recommendations are made regarding early response efforts and the ethical impact of aggressive prehospital resuscitation. The most sophisticated of emergency, operative, or intensive care units cannot reverse damage that has been set in motion by suboptimal protocols of triage and resuscitation, either at the injury scene or en route to the hospital. The quality of prehospital care is a major determinant of long-term outcome for patients with traumatic brain injury.

Preoperative resuscitation of the trauma patient

PURPOSE OF REVIEW

The traditional approach to trauma patients with presumed internal hemorrhage has been immediate, aggressive intravenous fluid resuscitation. Recent experimental and clinical data, however, suggest a more discriminating approach that first considers concurrent head injury, hemodynamic stability and the presence of potentially uncontrollable hemorrhage (e.g. deep truncal injury) versus a controllable source (e.g. distal extremity wound) as well as the use of new techniques to inhibit bleeding and better ways to monitor the patient's condition.

RECENT FINDINGS

Evolving data suggest that while aggressive fluid infusions could be used for patients with isolated extremity, thermal or head injury, they should be limited in conditions with potentially uncontrollable internal hemorrhage, and particularly in patients with penetrating truncal injury being transported immediately to a trauma center. Likewise, the minute volume of positive pressure ventilatory support should be limited with potential severe hemorrhage due to the secondary reductions in venous return. For trauma patients with severe bleeding there is growing evidence for the increased use of plasma and factor VIIa, as well as tourniquets, intraosseus devices and evolving monitoring techniques.

SUMMARY

Owing to the growing societal threat of trauma, further research, including studies already under way, will be critical to delineate the timing and technique of infusing advantageous resuscitative fluids such as hypertonic saline and hemoglobin-based oxygen carriers as well as the use of hemostatic agents and special blood products.

Secondary abdominal compartment syndrome after severe extremity injury: are early, aggressive fluid resuscitation strategies to blame?

INTRODUCTION

Secondary abdominal compartment syndrome (ACS) is the development of ACS in the absence of abdominal injury. The development of secondary ACS has been viewed by some authors as an unavoidable sequela of the aggressive crystalloid resuscitation often employed in the treatment of severe shock. We hypothesized that poor resuscitation techniques, including early and excessive crystalloid administration, places patients with extremity injuries at risk for developing secondary ACS.

METHODS

The Trauma Registry of the American College of Surgeons database was queried for all patients with an extremity Abbreviated Injury Scale (AIS) score of 3 or greater and abdominal AIS score of 0 treated at our institution between January 1, 2001 and December 31, 2005. The study group included those patients who developed secondary ACS, whereas the comparison cohort included those who did not develop secondary ACS.

RESULTS

Forty-eight patients developed secondary ACS and were compared with 48 randomly selected patients who had an extremity AIS score of 3 or greater and an abdomen AIS score of 0. There were no differences between the groups with respect to age, sex, race, or individual AIS scores. However, the secondary ACS group had a slightly higher Injury Severity Score (25.6 vs. 21.4, p = 0.02), significantly higher operating room crystalloid administration (9.9 L vs. 2.7 L, p < 0.001), and more frequent use of a rapid infuser (12.5% vs. 0.0%, p = 0.01). Multiple logistic regression identified prehospital and emergency department crystalloid as predictors of secondary ACS.

CONCLUSIONS

Aggressive resuscitation techniques, often begun in the prehospital setting, appear to increase the likelihood of patients with severe extremity injuries developing secondary ACS. Early, large volume crystalloid administration was the greatest predictor of secondary ACS.

Experimental study of controlled fluid resuscitation in the treatment of severe and uncontrolled hemorrhagic shock

BACKGROUND

Hemorrhagic shock is a common clinic emergency case. The fluid resuscitation method in the presurgical care of hypotensive trauma patients is open to debate. This study was conducted to evaluate the general and pathophysiologic effects of controlled fluid resuscitation in the treatment of severe and uncontrolled hemorrhagic shock.

METHODS

A model of rat with severe hemorrhagic shock and active bleeding was established in 32 Sprague-Dawley rats. The rats were randomly divided into the control group, no fluid resuscitation group (NF group), controlled fluid resuscitation group (NS40 group), and aggressive fluid resuscitation group (NS80 group). Each group contained eight rats. The changes of survival, blood loss, blood platelet, hemoglobin, hematocrit, and serum lactate level were dynamically monitored in the "prehospital phase". In addition, the apoptosis in the liver, kidney, lung, and small intestinal mucosa of survivors after hemorrhage and resuscitation was detected by light microscopy in hematoxylin-eosin stained tissue sections, flow cytometry, and terminal deoxynucleotidyl transferase dUTP nick end labeling. Via the above-mentioned indexes, the curative effects of three fluid resuscitation methods were compared.

RESULTS

Compared with the survival in the NF group (3 of 8), the higher survival rate of the NS40 and NS80 groups (14 of 16) showed significant difference (p < 0.05). After fluid resuscitation, serum lactate levels in the NS40 and NS80 groups obviously decreased (p < 0.01 compared with control and NF groups). The shed blood loss from bleeding tail in the NS80 group was obviously increased (p < 0.01 for the NS80 group compared with the control, NF, and NS40 groups). Compared with that of the control, NF, and NS40 groups, the hemoglobin, hematocrit, and blood platelet of the NS80 group quickly descended in the prehospital phase and showed statistical differences. At the same time, there was some apoptosis in the liver, kidney, lung, and small intestinal mucosa of all survivors. Compared with that of the NF and NS40 groups, the apoptosis of liver, kidney, and small intestinal mucosa of the NS80 group was obviously increased, and showed statistical differences.

CONCLUSIONS

In severe and uncontrolled hemorrhagic shock, some fluid must be given in proper time to improve tissue perfusion and avoid early death. Among three fluid resuscitation methods, controlled fluid resuscitation can effectively decrease additional blood loss, avoid excessive hemodilution and coagulopathy, improve the early survival rate, and reduce the apoptosis of visceral organs in rats with severe and uncontrolled hemorrhagic shock. This model supports the concept that when surgical care is not readily available, controlled fluid resuscitation should be considered in the treatment of uncontrolled hemorrhagic shock.

Treatment with a novel hemigramicidin-TEMPO conjugate prolongs survival in a rat model of lethal hemorrhagic shock

OBJECTIVE

We sought to develop a therapeutic agent that would permit prolongation of survival in rats subjected to lethal hemorrhagic shock (HS), even in the absence of resuscitation with asanguinous fluids or blood.

METHODS AND RESULTS

We synthesized a series of compounds that consist of the electron scavenger and superoxide dismutase mimic, 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-NH2-TEMPO), conjugated to fragments and analogs of the membrane-active cyclopeptide antibiotic, gramicidin S. Using an in vivo assay, wherein isolated intestinal segments were loaded inside the lumen with various test compounds, we studied these compounds for their ability to prevent ileal mucosal barrier dysfunction induced by subjecting rats to profound HS for 2 hours. The most active compound in this assay, XJB-5-131, ameliorated peroxidation of the mitochondrial phospholipid, cardiolipin, in ileal mucosal samples from rats subjected to HS. XJB-5-131 also ameliorated HS-induced activation of the pro-apoptotic enzymes, caspases 3 and 7, in ileal mucosa. Intravenous treatment with XJB-5-131 (2 micromol/kg) significantly prolonged the survival of rats subjected to profound blood loss (33.5 mL/kg) despite administration of only a minimal volume of crystalloid solution (2.8 mL/kg) and the absence of blood transfusion.

CONCLUSION

These data support the view that mitochondrially targeted electron acceptors and SOD mimics are potentially valuable therapeutics for the treatment of serious acute conditions, such as HS, which are associated with marked tissue ischemia.

C5-blocking antibody reduces fluid requirements and improves responsiveness to fluid infusion in hemorrhagic shock managed with hypotensive resuscitation

Hypotensive resuscitation strategies and inhibition of complement may both be of benefit in hemorrhagic shock. We asked if C5-blocking antibody (anti-C5) could diminish the amount of fluid required and improve responsiveness to resuscitation from hemorrhage. Awake, male Sprague-Dawley rats underwent controlled hemorrhage followed by prolonged (3 h) hypotensive resuscitation with lactated Ringer’s or Hextend, with or without anti-C5. Anti-C5 treatment led to an estimated 62.3 and 58.5% reduction in the volume of Hextend and lactated Ringer’s, respectively. In the subgroup of animals with a positive mean arterial pressure (MAP) response to fluid infusion following prolonged hypotension, anti-C5 treatment led to an estimated 4.7- and 4.1-fold increase in mean arterial pressure response per unit Hextend and lactated Ringer’s infused, respectively. We observed no significant postresuscitation metabolic differences between the anti-C5 groups and controls. Whether anti-C5 could serve as a volume-sparing adjunct that improves responsiveness to fluid administration in humans deserves further study.

Fluid resuscitation: computer simulation and animal experiments

The purpose of this study was to investigate the hemodynamic system in hemorrhagic shock and to estimate the effects of different infusion fluids and rates on the recovery of the bleeding patient. A mathematical model of the hemodynamic system was developed including fluid transfer to and from the interstitium for different types of fluids. The model was used to test different hemorrhagic shock conditions and different infusion conditions. To validate the model, a series of animal experiments was performed. The computer simulation followed successfully experimental data collected in five different experiments. Thus, it may now serve as an advanced tool for evaluating and analyzing effects of different fluids and optimize fluid regimen.

The cellular, metabolic, and systemic consequences of aggressive fluid resuscitation strategies

Increasing evidence has demonstrated that aggressive crystalloid-based resuscitation strategies are associated with cardiac and pulmonary complications, gastrointestinal dysmotility, coagulation disturbances, and immunological and inflammatory mediator dysfunction. As large volumes of fluids are administered, imbalances in intracellular and extracellular osmolarity occur. Disturbances in cell volume disrupt numerous regulatory mechanisms responsible for keeping the inflammatory cascade under control. Several authors have demonstrated the detrimental effects of large, crystalloid-based resuscitation strategies on pulmonary complications in specific surgical populations. Additionally, fluid-restrictive strategies have been associated with a decreased frequency of and shorter time to recovery from acute respiratory distress syndrome and trends toward shorter lengths of stay and lower mortality. Early resuscitation of hemorrhagic shock with predominately saline-based regimens has been associated with cardiac dysfunction and lower cardiac output, as well as higher mortality. Numerous investigators have evaluated potential risk factors for developing abdominal compartment syndrome and have universally noted the excessive use of crystalloids as the primary determinant. Resuscitation regimens that cause early increases in blood flow and pressure may result in greater hemorrhage and mortality than those regimens that yield comparable flow and pressure increases late in resuscitation. Future resuscitation research is likely to focus on improvements in fluid composition and adjuncts to administration of large volume of fluid.

Controversies in Fluid Resuscitation

The optimal degree of resuscitation in the initial control and resuscitative phase of trauma care remains unclear. Many attempts have been made with animal studies to determine the optimal degree and method of resuscitation. Human studies were first conducted in 1994 and the results were inconclusive and have not been replicated. The question of the volume, rate, and type of fluid to be infused for initial control and adequate resuscitation of the trauma patient remains to be answered.

An intention-to-treat by endovascular repair policy may reduce overall mortality in ruptured abdominal aortic aneurysm

OBJECTIVE

The use of endovascular aneurysm repair (EVAR) for ruptured abdominal aortic aneurysm (AAA) has been restricted to a small number of specialized units on a selected group of patients. The aim of this study is to assess if the overall mortality in these patients with ruptured AAA may be reduced in a unit where all patients with ruptured AAA are considered first for EVAR.

METHODS

During a 24-month period beginning in July 2002, 51 patients admitted with ruptured AAA were considered for EVAR as the treatment of choice and comprised the study group. EVAR was performed in 17 patients. Open repair was performed in 34 patients: 13 patients had hemodynamic instability and 16 patients had an unsuitable aortic neck anatomy. The study group was compared with a historical control group of 41 patients with ruptured AAA who were treated by open repair from July 2000 to June 2002.

RESULTS

Mortality rate was 39% in the study group compared with 59% in the control group (P = .065). The duration of stay in the intensive care unit was significantly lower in the study group than in the control group (P = .01), although the total in-hospital stay was similar (17 days vs 14 days, P = .83). Within the study group, EVAR patients had a mortality rate of 24% compared with 47% in the open group (P = .14).

CONCLUSION

Although the number of patients was small, offering EVAR to as many patients as possible with ruptured AAA has resulted in a 20% reduction in mortality, albeit statistically insignificant. However, it is in the unstable patients that EVAR will need to improve survival before it may be hailed to supersede the conventional approach.

Predictors of fluid resuscitation in pediatric trauma patients

Advanced Trauma Life Support (ATLS) is accepted as the standard for the first hours of trauma care. However, ATLS is designed primarily for adults. In children, vascular access can be difficult and time-consuming. Due to the differences in the epidemiology of children suffering traumatic injury, they may not require aggressive fluid resuscitation. The objective of the study was to establish predictors of fluid resuscitation, and to determine whether all pediatric Level I Trauma victims require two intravenous catheters. Medical charts of all patients aged < 18 years meeting Level I Trauma criteria who presented to Childrens Hospital Los Angeles (CHLA) between January 1 and December 31, 1999 were retrospectively reviewed. There were 152 patients reviewed with a median age of 6 years (range 4 months to 17 years); 64% were boys. The mechanism of injury was motor vehicle crash 49%, fall 37%, crush 8%, gunshot 5%, and knife 1%. Injuries included closed head 88%, penetrating abdomen/chest 6%, and other 6%. Vital signs over time showed no change in 59%, got better in 34%, and got worse in 7%. Fluid resuscitation included no bolus in 70%, 1 bolus in 20%, 2 boluses in 7%, > 2 boluses in 3%. The ICU admitted 23%, 12% were intubated, survival was 95%, and 59% received a prehospital i.v. The i.v. #1 site: antecubital 51%, hand 41%, foot 5%, femoral 1%. The i.v. #2 site: hand 30%, antecubital 20%, foot 2%, none 48%. T test showed no statistically significant differences in fluid resuscitation or second i.v. placement based on the mechanism of injury. T test for unequal variances showed a statistically significant difference in means with p < 0.001 for second i.v. placement as compared with only i.v. fluid amount, age, and Injury Severity Score (ISS). Revised Trauma Score was the only predictor of worsening of vital signs (logistic regression [LR], p < 0.001). Age was the only predictor of second i.v. placement (LR, p < 0.03). ISS was the only predictor of a bolus being given (LR, p < 0.01). In our study, blunt trauma occurred in 90% of children, with 10% requiring > 1 fluid bolus. ISS was the only predictor of the need for fluid resuscitation and is not likely to be helpful in the clinical setting. In our population, nearly 50% had no second i.v. This preliminary review of the nature of pediatric trauma suggests that ATLS guidelines may not always be appropriate for the management of pediatric trauma.

Timing of Fluid Resuscitation Shapes the Hemodynamic Response to Uncontrolled Hemorrhage: Analysis Using Dynamic Modeling

BACKGROUND

Timing of fluid resuscitation with respect to intrinsic hemostasis is an unexplored aspect of uncontrolled hemorrhage, because most animal models do not allow direct monitoring of blood loss. The aim of this study was to define how timing of crystalloid administration affects the bleeding patient's hemodynamic response to fluids, using a computer model of blood volume changes during uncontrolled hemorrhage.

METHODS

A multi-compartment lumped-parameter deterministic model of intravascular volume changes in a bleeding adult patient was developed and implemented. The model incorporates empirical mathematical descriptions of intrinsic hemostasis and rebleeding.

RESULTS

The predicted hemodynamic response to uncontrolled hemorrhage closely corresponds to that seen in animal studies. A 2-L crystalloid bolus given during ongoing hemorrhage increases blood loss by 4 to 29%, an effect that is inversely related to the initial bleeding rate. A similar bolus given after intrinsic hemostasis may trigger rebleeding if given when the hemostatic clot is mechanically vulnerable. This period of clot vulnerability (ranging from 0-34 minutes) changes with both the initial bleeding rate and the rate of fluid administration.

CONCLUSIONS

The timing of crystalloid administration with respect to intrinsic hemostasis shapes the bleeding patient's hemodynamic response. An early bolus delays hemostasis and increases blood loss, while a late bolus may trigger rebleeding. These observations provide valuable insight into the hemodynamic response to fluid resuscitation.

Normotensive and hypotensive closed-loop resuscitation using 3.0% NaCl to treat multiple hemorrhages in sheep

OBJECTIVE

NaCl solutions (7.5%) have been reported to be effective for resuscitation in animals and trauma patients, but these solutions are not approved for use in the United States. We hypothesized that infusion of Food and Drug Administration-approved 3% NaCl provides superior cardiovascular and metabolic function while reducing the overall fluid requirement for resuscitation of hemorrhage. Our objective was to compare four groups, hypotensive and normotensive resuscitation of hemorrhage using 3% NaCl (HS) or lactated Ringer's (LR).

DESIGN

Sheep were hemorrhaged in three separate bleeds, 25 mL/kg at T0 mins and 5 mL/kg at both T50 and T70 mins.

SETTING

University laboratory.

SUBJECTS

Instrumented conscious sheep.

INTERVENTIONS

Resuscitation was started at T30 mins and continued until T180. Normotensive and hypotensive resuscitation to mean arterial pressures of 90 mm Hg and 65 mm Hg, respectively, was performed with LR or HS using a closed-loop resuscitation system.

MEASUREMENTS AND MAIN RESULTS

All four groups were successfully resuscitated to near target levels. Two animals in the hypotensive treatment protocols died during the second and third bleeding, one with the LR65 group and one with the HS65 group. Mean infused volumes were 59.9 +/- 7.0 and 18.0 +/- 5.9 in the LR90 and LR65 groups, respectively, and were 19.6 +/- 2.2 mL/kg and 13.3 +/- 5.7 mL/kg in the HS90 and HS65 treatments (p < .05; LR90 vs. each of the groups). Cardiac indexes were significantly higher with normotensive vs. hypotensive treatment. However, there was no hemodynamic advantage apparent with HS vs. LR when compared with the normotensive or hypotensive treatments. Some animals had high lactate levels (>10 mmol) with both of the hypotensive treatments and also with the HS90 treatment, while not one of the 11 LR90 treatment animals had lactate levels >8 mmol.

CONCLUSIONS

Volume sparing was apparent with HS, but no hemodynamic or metabolic advantage was apparent when used for either normotensive or hypotensive resuscitation. Trends toward lower base excess values and higher occurrences of deaths only in the hypotensive treatment protocols suggest that resuscitation to a target mean arterial pressure of 65 mm Hg may be too low.

Hypotensive Resuscitation in Patients with Ruptured Abdominal Aortic Aneurysm

BACKGROUND

The technique of hypotensive resuscitation in haemorrhagic shock involves resuscitation to below normotensive blood pressures achieving the minimum perfusion pressure that will adequately perfuse vital organs until definitive arrest of haemorrhage.

AIM

To summarise the evidence for the use of hypotensive resuscitation in patients with uncontrolled haemorrhagic shock and ruptured abdominal aortic aneurysm (AAA).

METHODS

A MEDLINE (1966-2004) and Cochrane library search for articles relating to hypotensive resuscitation was undertaken; see text for further details.

RESULTS

Several animal studies exist using an abdominal aortotomy model of ruptured AAA. These have demonstrated improved tissue perfusion, decreased blood loss and improved survival associated with hypotensive resuscitation compared with aggressive resuscitation. There are several human studies advocating delayed rather than immediate resuscitation in trauma patients but careful review of the literature reveals no prospective studies of hypotensive resuscitation in patients with ruptured AAA.

CONCLUSIONS

Animal studies demonstrate superiority of hypotensive resuscitation over aggressive resuscitation but further research is required to assess its efficacy in patients with ruptured AAA.

Titrated hypertonic/hyperoncotic solution for hypotensive fluid resuscitation during uncontrolled hemorrhagic shock in rats

BACKGROUND

In volume- or pressure-controlled hemorrhagic shock (HS) a bolus intravenous infusion of hypertonic/hyperoncotic solution (HHS) proved beneficial compared to isotonic crystalloid solutions. During uncontrolled HS in animals, however, HHS by bolus increased blood pressure unpredictably, and increased blood loss and mortality. We hypothesized that a titrated i.v. infusion of HHS, compared to titrated lactated Ringer's solution (LR), for hypotensive fluid resuscitation during uncontrolled HS reduces fluid requirement, does not increase blood loss, and improves survival.

METHODS

We used our three-phased uncontrolled HS outcome model in rats. HS phase I began with blood withdrawal of 3 ml/100g over 15 min, followed by tail amputation. Then, hydroxyethyl starch 10% in NaCl 7.2% was given i.v. to the HHS group (n=10) and LR to the control group (n=10), both titrated to prevent mean arterial pressure (MAP) from falling below 40 mmHg during HS time 20-90 min. At HS 90 min, resuscitation phase II of 180 min began with hemostasis, return of all the blood initially shed, plus fluids i.v. as needed to maintain normotension (MAP>or=70 mmHg). Liver dysoxia was monitored as increase in liver surface pCO2 during phases I and II. Observation phase III was to 72 h.

RESULTS

During HS, preventing a decrease in MAP below 40 mmHg required HHS 4.9+/-0.6 ml/kg (all data mean+/-S.E.M.), compared to LR 62.2+/-16.6 ml/kg (P<0.001), with no group difference in MAP. Uncontrolled blood loss during HS from the tail stump was 13.3+/-1.9 ml/kg with HHS infusion, versus 12.6+/-2.5 ml/kg with LR infusion (P=0.73). Serum sodium concentrations were moderately elevated at the end of HS in the HHS group (149+/-3 mmol/l) versus the LR group (139+/-1 mmol/l) (P=0.001), and remained elevated throughout. Liver pCO2 increased during HS in both groups equally (P<0.001 versus baseline), and tended to return to baseline levels at the end of HS. Blood gas and lactate values throughout did not differ between groups. During HS, 2 of 10 rats in the HHS group versus 0 of 10 in the LR group died (P=0.47). There was no difference between HHS and LR groups in survival rates to 72 h (3 of 10 in the HHS group versus 2 of 10 in the LR group) (P=1.0). Survival times, by life table analysis, were not different (P=0.75).

CONCLUSION

In prolonged uncontrolled HS, a titrated i.v. infusion of HHS can maintain controlled hypotension with only one-tenth of the volume of LR required, without increasing blood loss. This titrated HHS strategy may not increase the chance of long-term survival.

A Hemoglobin Based Oxygen Carrier, Bovine Polymerized Hemoglobin (HBOC-201) versus Hetastarch (HEX) in an Uncontrolled Liver Injury Hemorrhagic Shock Swine Model with Delayed Evacuation

BACKGROUND

As HBOC-201 improves outcome in animals with hemorrhagic shock (HS), we compared HBOC-201 and HEX (used by U.S. military special operations forces) in a swine model of delayed evacuation and uncontrolled HS.

METHODS

Twenty-four Yucatan pigs underwent a grade III liver injury and were resuscitated with HBOC-201, HEX, or no fluid (NON). Additional infusions were given for hypotension or tachycardia. After 4 hours, the liver was repaired; IV fluids and blood transfusions were administered. Pigs were monitored for 72 hours.

RESULTS

Survival was 7/8, 1/8, and 1/8 in HBOC-201-, HEX-, and NON-resuscitated pigs, respectively. Compared with HEX, HBOC-201 pigs had higher systemic and pulmonary artery pressures and had comparable cardiac outputs, but were less tachycardic. Transcutaneous tissue oxygenation was restored more rapidly in HBOC-201 pigs, there was a trend to lower lactic acid, and base deficit was less. HBOC-201 pigs had lower fluid requirements, higher urine output, and lower blood loss than HEX pigs.

CONCLUSIONS

Despite evidence of vasoactivity, HBOC-201 more effectively stabilized tissue oxygenation, reversed anaerobic metabolism, decreased bleeding, and increased survival in comparison with HEX. If confirmed in clinical trials, these data suggest that for the resuscitation of combat casualties with delayed evacuation and uncontrolled HS due to solid organ injury, HBOC-201 is a superior low-volume resuscitative fluid.

HYPOTENSIVE RESUSCITATION OF MULTIPLE HEMORRHAGES USING CRYSTALLOID AND COLLOIDS

Hypotensive resuscitation has been advocated as a better means to perform field resuscitation of penetrating trauma. Our hypothesis is that hypotensive resuscitation using either crystalloid or colloid provides equivalent or improved metabolic function while reducing the overall fluid requirement for resuscitation of hemorrhage. We compared hypotensive and normotensive resuscitation of hemorrhage using lactated Ringer's (LR) with hypotensive resuscitation using Hextend (Hex), 6% hetastarch in isotonic buffered saline. Instrumented conscious sheep were hemorrhaged in three separate bleeds, 25 mL/kg at T0 and 5 mL/kg at both T50 and T70. Resuscitation was started at T30 and continued until T180. Hypotensive resuscitation to a mean arterial pressure (MAP) of 65 mmHg was performed with LR or Hex using a closed-loop resuscitation (CLR) system for a LR-65 and Hex-65 treatment protocol. A control treatment protocol was resuscitation with LR to a MAP target of 90 mmHg, LR-90. All treatment protocols were successfully resuscitated to near target levels. Two animals in the hypotensive treatment protocols died during the second and third bleedings, one in the LR-65 and one in the Hex-65 treatment protocol. Mean infused volumes were 61.4 +/- 11.3, 18.0 +/- 5.9, and 11.6 +/- 1.9 mL/kg in the LR-90, LR-65, and Hex-65 treatments, respectively (*P < 0.05 versus LR-90). Mean minimum base excess (BE) values were +1.9 +/- 1.4, -5.8 +/- 4.3, and -5.9 +/- 4.0 mEq/L in the LR-90, LR-65, and Hex-65 treatments, respectively. Hypotensive resuscitation with LR greatly reduced volume requirements as compared with normotensive resuscitation, and Hex achieved additional volume sparing. However, trends toward lower BE values and the occurrence of deaths only in the hypotensive treatment protocols suggest that resuscitation to a target MAP of 65 mmHg may be too low for optimal outcomes.

SURVIVAL IN A RAT MODEL OF LETHAL HEMORRHAGIC SHOCK IS PROLONGED FOLLOWING RESUSCITATION WITH A SMALL VOLUME OF A SOLUTION CONTAINING A DRAG-REDUCING POLYMER DERIVED FROM ALOE VERA

Drag-reducing polymers (DRP) increase tissue perfusion at constant driving pressure. We sought to evaluate the effects of small-volume resuscitation with a solution containing a DRP in a rat model of hemorrhage. Anesthetized rats were hemorrhaged at a constant rate over 25 min. In protocol A, total blood loss was 2.45 mL/100 g, whereas in protocol B, total blood loss was 3.15 mL/100 g. Five minutes after hemorrhage, the animals were resuscitated with 7 mL/kg of either normal saline (NS) or NS containing 50 microg/mL of an aloe vera-derived DRP. In protocol B, a third group (CON) was not resuscitated. Whole-body O2 consumption (Vo2) and CO2 production (Vco2) were measured using indirect calorimetry. In protocol A, 5/10 rats in the NS group and 8/10 rats in the DRP group survived for 4 h (P = 0.14). Mean arterial pressure was higher in the DRP-treated group than in the NS-treated group 45 min after resuscitation (89 +/- 8 vs. 68 +/- 5 mmHg, respectively; P < 0.05). In protocol B, survival rates over 2 h in the DRP, NS, and CON groups were 5/15, 1/14, and 0/7, respectively (P < 0.05). Compared with NS-treated rats, those resuscitated with DRP achieved a higher peak Vo2 (9.0 +/- 1.0 vs. 6,3+/- 1.0 mL/kg/min) and Vco2 (9.0 +/- 1.1 vs. 6.0 +/- 1.0 mL/kg/min) after resuscitation. We conclude that resuscitation with a small volume of DRP prolongs survival in rats with lethal hemorrhagic shock.

A novel pain management strategy for combat casualty care

STUDY OBJECTIVE

Pain control in trauma patients should be an integral part of the continuum of care, beginning at the scene with out-of-hospital trauma management, sustained through the evacuation process, and optimized during hospitalization. This study evaluates the effectiveness of a novel application of a pain control medication, currently indicated for the management of chronic and breakthrough cancer pain, in the reduction of acute pain for wounded Special Operations soldiers in an austere combat environment.

METHODS

Doses (1,600 microg) of oral transmucosal fentanyl citrate were administered by medical personnel during missions executed in support of Operation Iraqi Freedom from March 3, 2003, to May 3, 2003. Hemodynamically stable casualties presenting with isolated, uncomplicated orthopedic injuries or extremity wounds who would not have otherwise required an intravenous catheter were eligible for treatment and evaluation. Pretreatment, 15-minute posttreatment, and 5-hour posttreatment pain intensities were quantified by the verbal 0-to-10 numeric rating scale.

RESULTS

A total of 22 patients, aged 21 to 37 years, met the study criterion. The mean difference in verbal pain scores (5.77; 95% confidence interval [CI] 5.18 to 6.37) was found to be statistically significant between the mean pain rating at 0 minutes and the rating at 15 minutes. However, the mean difference (0.39; 95% CI -0.18 to 0.96) was not statistically significant between 15 minutes and 5 hours, indicating the sustained action of the intervention without the need for redosing. One patient experienced an episode of hypoventilation that resolved readily with administration of naloxone. Other documented adverse effects were minor and included pruritus (22.7%), nausea (13.6%), emesis (9.1%), and lightheadedness (9.1%).

CONCLUSION

Oral transmucosal fentanyl citrate can provide an alternative means of delivering effective, rapid-onset, and noninvasive pain management in an out-of-hospital, combat, or austere environment.

Splanchnic Perfusion During Delayed, Hypotensive, or Aggressive Fluid Resuscitation From Uncontrolled Hemorrhage

The purpose of this study was to determine the effect of three different fluid resuscitation strategies on splanchnic perfusion in a clinically relevant model of uncontrolled hemorrhage after liver trauma. Anesthetized swine were instrumented with a gastric near-infrared spectroscopy probe (GStO2), a jejunal tonometer (PrCO2), a portal vein catheter (SpvO2, lactate), and an ultrasonic blood flow probe on the superior mesenteric artery. The liver was lacerated to produce uncontrolled hemorrhage and a shock state characterized by a 40-60% decrease in cardiac output and a decrease in mean arterial pressure (MAP) to 42 +/- 1 mmHg. Animals were randomly assigned to either delayed resuscitation (n = 6); hypotensive resuscitation with lactated Ringer's infusion to MAP = 60 mmHg (n = 6); or aggressive resuscitation with LR to MAP >/= 75 mmHg (n = 6). For the remainder of the protocol, the treatment was identical. The data showed that blood loss (47 +/- 7 and 45 +/- 10 mL/kg) and total fluid requirements (118 +/- 73 and 171 +/- 85 mL/kg) were similar with either hypotensive or aggressive resuscitation. In contrast, with delayed resuscitation, both values were lower (27 +/- 2 mL/kg and 87 +/- 33 mL/kg, both P < 0.05). Despite aggressive resuscitation, SpvO2 and GstO2 were about 10% lower (both P < 0.05 within group) and PrCO2 was about 20 mmHg higher (P < 0.05 within group) than the corresponding values in the other two groups. Thus, delayed resuscitation minimized the blood loss but did not restore tissue oxygenation, whereas aggressive resuscitation was associated with maximal blood loss and splanchnic hypoperfusion. For this reason, it is reasonable to conclude that hypotensive resuscitation might be an effective strategy to maintain splanchnic perfusion after blunt abdominal trauma and uncontrolled hemorrhage.

Fluid Resuscitation Strategies: A Systematic Review of Animal Trials

OBJECTIVES

Our objective was to systematically review randomized, controlled trials of fluid resuscitation in animal models of uncontrolled hemorrhage and to explore potential sources of heterogeneity.

METHODS

We conducted an electronic bibliographic search of published research, reviewed reference lists of included trials, and contacted authors about unpublished studies. We included all unconfounded, randomized, controlled trials of fluid resuscitation (timing, volume, or resuscitation targets) in animal models of uncontrolled hemorrhage. The outcome measure was mortality at the end of the scheduled follow-up period of the trial. Two reviewers independently applied the selection criteria to the trial reports. A third reviewer resolved disagreements.

RESULTS

Forty-four trials compared fluid versus no fluid resuscitation. There was marked heterogeneity in the effect of fluid resuscitation on the risk of death, much of which was explained by the hemorrhage model used. In aortic injury models, the adjusted relative risk of death with fluid resuscitation was 0.48 (95% confidence interval [CI], 0.33-0.71). In organ incision models, the adjusted relative risk of death was 0.76 (95% CI, 0.49-1.18). In tail resection models, the adjusted relative risk of death was 0.69 (95% CI, 0.38-1.25) if 50% or more was removed and 1.86 (95% CI, 1.13-3.07) if less than 50% was removed. In other vascular injury models, the adjusted relative risk of death with fluid resuscitation was 1.70 (95% CI, 1.01-2.85), respectively. Nine trials compared hypotensive versus normotensive resuscitation. The relative risk of death with hypotensive resuscitation was 0.37 (95% CI, 0.27-0.50).

CONCLUSION

Fluid resuscitation appears to reduce the risk of death in animal models of severe hemorrhage but increases the risk of death in those with less severe hemorrhage. Excessive fluid resuscitation could therefore be harmful in some situations. Hypotensive resuscitation reduced the risk of death in all the trials investigating it. An evaluation of the potential impact of hypotensive resuscitation in humans could now be warranted.

Small-volume fluid resuscitation for the far-forward combat environment: current concepts

Hemorrhage remains the primary cause of death on the battlefield in conventional warfare. With modern combat operations leading to the likelihood of significant time delays in air evacuation of casualties and long transport times, the immediate goals of the Army's Science and Technology Objectives in Resuscitation are to develop limited- or small-volume fluid resuscitation strategies, including permissive hypotension, for the treatment of severe hemorrhage to improve battlefield survival and prevent early and late deleterious sequelae. As an example, the U.S. Army has invested much effort in the evaluation of hypertonic saline dextran (HSD) as a plasma volume expander, at one tenth to one twelfth the volume of conventional crystalloids, in numerous animal models of hemorrhage. These studies have identified HSD as a potentially useful field resuscitation fluid. In addition, preliminary studies have used HSD under hypotensive resuscitation conditions, and it has been administered through intraosseous infusion devices for vascular access. This research suggests that many of the difficulties and concerns associated with fluid resuscitation for treating significant hemorrhage in the field can be overcome. For the military, such observations have important implications toward the development of optimal fluid resuscitation strategies under austere battlefield conditions for stabilization of the combat casualty.

Endpoints for fluid resuscitation in hemorrhagic shock

Vigorous intravenous fluid resuscitation has become widely accepted as the optimum management of hemorrhagic shock in trauma. There is now, however, sufficient evidence for this position to be reviewed. Hypotensive or delayed resuscitation has been postulated as a means by which the mortality associated with treatment can be reduced. It has been suggested that overresuscitation with intravenous fluids may worsen hemorrhage. This article discusses the possible adverse effects of "conventional" resuscitation and examines the evidence to support alternative treatment modalities.

Near-infrared spectroscopy-guided closed-loop resuscitation of hemorrhage

BACKGROUND

Endpoint resuscitation has been suggested as a better means to resuscitate penetrating injury. We performed computer-controlled closed-loop resuscitation using invasive cardiac output (CO) or noninvasive skeletal muscle oxygen saturation (SkMusSO(2)) via near infrared spectroscopy (NIRS).

METHODS

Conscious sheep received a 4.0-mm aortotomy and uncontrolled hemorrhage at t = 0 min (T0) while resuscitation started at T20 using lactated Ringer's solution.

RESULTS

The aortotomy rapidly decreased the mean arterial pressure (MAP) to approximately 30 mm Hg and CO to 20% to 30% of baseline. The SkMusSO(2) endpoint group required only half as much fluid through 4 hours of resuscitation as the CO endpoint group (34.9 +/- 8.4 mL/kg vs. 63.1 +/- 9.4 mL/kg). CO and MAP were lower in the SkMusSO(2) group after T60. Mean infusion volumes were 180% and 100% of the bled volume collected at autopsy in the CO and SkMusSO(2) groups. Brain and muscle oxygenation and base excess were as high or higher in the CO endpoint group.

CONCLUSION

Closed-loop resuscitation with either CO or SkMusSO(2) endpoints effectively performs fluid resuscitation of severe uncontrolled hemorrhagic shock. Limited resuscitation may achieve favorable clinical results with volumes less than recommended by Advanced Trauma Life Support guidelines.