The Cardiac Physiology Underpinning Exsanguination Cardiac Arrest: Targets for Endovascular Resuscitation.

ABSTRACT: Exsanguination leading to cardiac arrest is the terminal phase of uncontrolled hemorrhage. Resuscitative interventions have focused on preload and afterload support. Outcomes remain poor due to several factors but poor coronary perfusion undoubtedly plays a role. The aim of this study is to characterize the relationship between arterial pressure and flow during hemorrhage in an effort to better describe the terminal phases of exsanguination.Male swine weighing 60 kg to 80 kg underwent splenectomy and instrumentation followed by a logarithmic exsanguination until asystole. Changes in hemodynamic parameters over time were compared using one-way, repeated measures analysis of variance.Nine animals weighing 69 ±â€Š15 kg were studied. Asystole occurred at 53 ±â€Š13 min when 52 ±â€Š11% of total blood volume has been shed. The greatest fall in mean hemodynamic indices were noted in the first 15 min: SBP (80-42 mm Hg, P = 0.02), left ventricular end-diastolic volume (94-52 mL, P = 0.04), cardiac output (4.8-2.4 L/min, P = 0.03), coronary perfusion pressure (57-30 mm Hg, P = 0.01), and stroke volume (60-25 mL, P = 0.02). This corresponds to the greatest rate of exsanguination. Organized cardiac activity was observed until asystole without arrythmias. Coronary flow was relatively preserved throughout the study, with a precipitous decline once mean arterial pressure was less than 20 mm Hg, leading to asystole.In this model, initial hemodynamic instability was due to preload failure, with asystole occurring relatively late, secondary to failure of coronary perfusion. Future resuscitative therapies need to directly address coronary perfusion failure if effective attempts are to be made to salvage these patients.

Outcomes following resuscitative thoracotomy for abdominal exsanguination, a systematic review.

BACKGROUND: Resuscitative thoracotomy is a damage control procedure with an established role in the immediate treatment of patients in extremis or cardiac arrest secondary to cardiac tamponade however Its role in resuscitation of patients with abdominal exsanguination is uncertain. OBJECTIVE: The primary objective of this systematic review was to estimate mortality based on survival to discharge in patients with exsanguinating haemorrhage from abdominal trauma in cardiac arrest or a peri arrest clinical condition following a resuscitative thoracotomy. METHODS: A systematic literature search was performed to identify original research that reported outcomes in resuscitative thoracotomy either in the emergency department or pre-hospital environment in patients suffering or suspected of suffering from intra-abdominal injuries. The primary outcome was to assess survival to discharge. The secondary outcomes assessed were neurological function post procedure and the role of timing of intervention on survival. RESULTS: Seventeen retrospective case series were reviewed by a single author which described 584 patients with isolated abdominal trauma and an additional 1745 suffering from polytrauma including abdominal injuries. Isolated abdominal trauma survival to discharge ranged from 0 to 18% with polytrauma survival of 0-9.7% with the majority below 1%. Survival following a thoracotomy for abdominal trauma varied between studies and with no comparison non-intervention group no definitive conclusions could be drawn. Timing of thoracotomy was important with improved mortality in patients not in cardiac arrest or having the procedure performed just after a loss of signs of life. Normal neurological function at discharge ranged from 100 to 28.5% with the presence of a head injury having a negative impact on both survival and long-term morbidity. CONCLUSIONS: Pre-theatre thoracotomy may have a role in peri-arrest or arrested patient with abdominal trauma. The best outcomes are achieved with patients not in cardiac arrest or who have recently arrested and with no head injury present. The earlier the intervention can be performed, the better the outcome for patients, with survival figures of up to 18% following a resuscitative thoracotomy. More high-quality evidence is required to demonstrate a definitive mortality benefit for patients.

Physiological comparison of hemorrhagic shock and V˙ O2max: A conceptual framework for defining the limitation of oxygen delivery.

IMPACT STATEMENT: Disturbance of normal homeostasis occurs when oxygen delivery and energy stores to the body's tissues fail to meet the energy requirement of cells. The work submitted in this review is important because it advances the understanding of inadequate oxygen delivery as it relates to early diagnosis and treatment of circulatory shock and its relationship to disturbance of normal functioning of cellular metabolism in life-threatening conditions of hemorrhage. We explored data from the clinical and exercise literature to construct for the first time a conceptual framework for defining the limitation of inadequate delivery of oxygen by comparing the physiology of hemorrhagic shock caused by severe blood loss to maximal oxygen uptake induced by intense physical exercise. We also provide a translational framework in which understanding the fundamental relationship between the body's reserve to compensate for conditions of inadequate oxygen delivery as a limiting factor to V˙ O2max helps to re-evaluate paradigms of triage for improved monitoring of accurate resuscitation in patients suffering from hemorrhagic shock.

Current trends in the management of hemodynamically unstable pelvic ring injuries.

PURPOSE OF REVIEW: Complex traumatic pelvic ring disruptions are associated with a high mortality rate due to associated retroperitoneal hemorrhage, traumatic-hemorrhagic shock, and postinjury coagulopathy. The present review provides an update on current management strategies to improve survival rates form hemodynamically unstable pelvic ring injuries. RECENT FINDINGS: Recently published international consensus guidelines have attempted to standardize the classification of hemodynamically unstable pelvic ring injuries and provided classification-based management algorithms for acute resuscitation and pelvic ring stabilization. SUMMARY: Acute management strategies for pelvic ring disruptions with associated hemorrhagic shock include resuscitative endovascular balloon occlusion of the aorta for patients 'in extremis' in conjunction with point-of-care guided resuscitation for postinjury coagulopathy. Recent data indicate that a protocol of early pelvic external fixation in conjunction with direct preperitoneal pelvic packing and subsequent angioembolization in patients with ongoing hemorrhage results in significantly improved survival from retroperitoneal exsanguinating hemorrhage in at-risk patients with historic mortality rates as high as 50-60%.

Extending the golden hour: Partial resuscitative endovascular balloon occlusion of the aorta in a highly lethal swine liver injury model.

BACKGROUND: Combat-injured patients may require rapid and sustained support during transport; however, the prolonged aortic occlusion produced by conventional resuscitative endovascular balloon occlusion of the aorta (REBOA) may lead to substantial morbidity. Partial REBOA (P-REBOA) may permit longer periods of occlusion by allowing some degree of distal perfusion. However, the ability of this procedure to limit exsanguination is unclear. We evaluated the impact of P-REBOA on immediate survival and ongoing hemorrhage in a highly lethal swine liver injury model. METHODS: Fifteen Yorkshire-cross swine were anesthetized, instrumented, splenectomized, and subjected to rapid 10% total blood loss followed by 30% liver amputation. Coagulopathy was created through colloid hemodilution. Randomized swine received no intervention (control), P-REBOA, or complete REBOA (C-REBOA). Central mean arterial pressure (cMAP), carotid blood flow, and blood loss were recorded. Balloons remained inflated in the P-REBOA and C-REBOA groups for 90 minutes followed by graded deflation. The study ended at 180 minutes from onset of hemorrhage or death of the animal. Survival analysis was performed, and data were analyzed using repeated-measures analysis of variance with post hoc pairwise comparisons. RESULTS: Mean survival times in the control, P-REBOA, and C-REBOA groups were, 25 ± 21, 86 ± 40, and 163 ± 20 minutes, respectively (p < 0.001). Blood loss was greater in the P-REBOA group than the C-REBOA or control groups, but this difference was not significant (4,722 ± 224, 3,834 ± 319, 3,818 ± 37 mL, respectively, p = 0.10). P-REBOA resulted in maintenance of near-baseline carotid blood flow and cMAP, while C-REBOA generated extreme cMAP and prolonged supraphysiologic carotid blood flow. Both experimental groups experienced profound decreases in cMAP following balloon deflation. CONCLUSION: In the setting of severe ongoing hemorrhage, P-REBOA increased survival time beyond the golden hour while maintaining cMAP and carotid flow at physiologic levels.

Diet-induced obesity prevents the development of acute traumatic coagulopathy.

BACKGROUND: Obesity and hemorrhagic shock following trauma are predictors of mortality but have conflicting effects on coagulation. Following hemorrhage, tissue injury and hypoperfusion lead to acute traumatic coagulopathy (ATC), producing a hypocoagulable state. Inversely, obesity promotes clotting and impairs fibrinolysis to yield a hypercoagulable state. High rates of venous thromboembolism, organ failure, and early mortality may be caused by hypercoagulability in obese patients. We hypothesize that obesity prevents the development of ATC following injury-induced hemorrhagic shock. METHODS: Male Sprague-Dawley rats (250-275 g) were fed a high-fat diet (32%kcal from fat) for 4 weeks to 6 weeks and diverged into obesity-resistant (OR, n = 9) and obesity-prone (OP, n = 9) groups. Age-matched control (CON) rats were fed normal diet (10% kcal from fat, n = 9). Anesthetized rats were subjected to an uncontrolled hemorrhage by a Grade V splenic injury to a mean arterial pressure (MAP) of 40 mm Hg. Hypotension (MAP, 30-40 mm Hg) was maintained for 30 minutes to induce shock. MAP, heart rate, lactate, base excess, cytokines, blood loss, and thrombelastography (TEG) parameters were measured before and after hemorrhagic shock. RESULTS: At baseline, OP rats exhibited a shorter time to 20-mm clot (K), and higher rate of clot formation (α angle), clot strength (maximal amplitude), and coagulation index, compared with the CON rats (p < 0.05), indicating enhanced coagulation. Physiologic parameters following shock were similar between groups. In the CON and OR rats, shock prolonged the time to clot initiation (R) and K and decreased α angle and coagulation index (all p < 0.05 vs. baseline). In contrast, shock had no effect on these TEG parameters in the OP rats. Maximal amplitude was the only TEG parameter affected by shock in the OP rats, which was decreased in all groups. CONCLUSION: Obesity prevents the development of ATC following hemorrhage shock. Complications associated with obesity following hemorrhagic shock may be attributed to the preserved hypercoagulable state.

Spontaneous swallowing occurs during autoresuscitation in the in situ brainstem preparation of rat.

Previous studies report that upper airway reflexes are operational during autoresuscitation from respiratory arrest. We investigated swallowing/breathing interactions, measured by recording of vagal (VNA) and phrenic nerve activities (PNA), during autoresuscitation in the in situ perfused brainstem preparation of juvenile rats. During the initial surgery, respiratory arrest was induced by exsanguination and cooling. Reperfusion (i.e. re-oxygenation and re-warming) of the brainstem circuits was associated with frequent spontaneous swallowing before resumption of respiration (n=6, 'stage 1 autoresuscitation'). When recovered, the respiratory pattern was transiently apneustic-like ('stage 2 autoresuscitation'). Spontaneous swallowing often occurred at the end of the prolonged PNA (n=9/12). Successful autoresuscitation was characterised by re-establishment of the 3 phase respiratory motor pattern and no spontaneous swallowing. Pharmacological inhibition (isoguvacine, 10 mM, 50-75 nl; n=10) of the Kölliker-Fuse nucleus (KF) mimicked stage 2 autoresuscitation. However, the frequency of spontaneous swallowing after KF inhibition did not correlate with subsequent recovery of the eupneic respiratory motor pattern.

Effects of intraosseous and intravenous administration of Hextend® on time of administration and hemodynamics in a Swine model.

INTRODUCTION: The military recommends that a 500 mL bolus of Hextend® be administered via an intravenous (IV) 18-gauge needle or via an intraosseous (IO) needle for patients in hypovolemic shock. PURPOSES: The purposes of this study were to compare the time of administration of Hextend and the hemodynamics of IV and IO routes in a Class II hemorrhage swine model. METHODS: This was an experimental study using 27 swine. After 30% of their blood volume was exsanguinated, 500 mL of Hextend was administered IV or IO, but not to the control group. Hemodynamic data were collected every 2 minutes until administration was complete. RESULTS: Time for administration was not significant (p=.78). No significant differences existed between the IO and IV groups relative to hemodynamics (p>.05), but both were significantly different than the control group (p<.05). CONCLUSIONS: The IO route is an effective method of administering Hextend.

Examining prehospital intubation for penetrating trauma in a swine hemorrhagic shock model.

BACKGROUND: Prehospital intubation does not result in a survival advantage in patients experiencing penetrating trauma, yet resistance to immediate transportation to facilitate access to definitive care remains. An animal model was developed to determine whether intubation provides a survival advantage during severe hemorrhagic shock. We hypothesized that intubation would not provide a survival advantage in potentially lethal hemorrhage. METHODS: After starting a propofol drip, Yorkshire pigs were intubated (n = 6) or given bag-valve mask ventilation (n = 7) using 100% oxygen. The carotid artery was cannulated with a 14-gauge catheter, and a Swan-Ganz catheter was placed under fluoroscopy using a central venous introducer. After obtaining baseline hemodynamic and laboratory data, the animals were exsanguinated through the carotid line until death. The primary end point was time until death, while secondary end points included volume of blood shed, temperature, cardiac index, mean arterial pressure, lactic acid, base excess, and creatinine levels measured in 10-minute intervals. RESULTS: There was no difference in time until death between the two groups (51.1 [2.5] minutes vs. 48.5 [2.4] minutes, p = 0.52). Intubated animals had greater volume of blood shed at 30 minutes (33.6 [4.4] mL/kg vs. 28.5 [4.3] mL/kg, p = 0.03), 40 minutes (41.7 [4.7] mL/kg vs. 34.9 [3.8] mL/kg, p = 0.04), and 50 minutes (49.2 [8.6] mL/kg vs. 40.2 [1.0] mL/kg, p = 0.001). In addition, the intubated animals were more hypothermic at 40 minutes (35.5°C [0.4°C] vs. 36.7°C [0.2°C], p = 0.01) and had higher lactate levels (2.4 [0.1] mmol/L vs. 1.8 [0.4] mmol/L, p = 0.04) at 10 minutes. Cardiac index (p = 0.66), mean arterial pressure (p = 0.69), base excess (p = 0.14), and creatinine levels (p = 0.37) were not different throughout the shock phase. CONCLUSION: Intubation does not convey a survival advantage in this model of severe hemorrhagic shock. Furthermore, intubation in the setting of severe hemorrhagic shock may result in a more profuse hemorrhage, worse hypothermia, and higher lactate when compared with bag-valve mask ventilation.

Therapeutic hypothermia after exsanguination.

Therapeutic hypothermia has been shown to be effective in out-of-hospital cardiac arrest, and use of this therapy has been expanded to involve in-hospital cardiac arrest. The utility of hypothermia in cardiac arrest after hemorrhage is not known. We describe a case of successful neurological and functional outcome after in-hospital pulseless electrical activity arrest secondary to exsanguination from an internal carotid artery rupture. Therapeutic hypothermia by surface cooling was initiated after acute control of the bleeding source, restoration of circulating blood volume, and hemodynamic stabilization. We believe therapeutic hypothermia use will continue to increase for in-hospital cardiac arrests.

A decade's experience with balloon catheter tamponade for the emergency control of hemorrhage.

BACKGROUND: Balloon catheter tamponade is a valuable technique for arresting exsanguinating hemorrhage. Indications include (1) inaccessible major vascular injuries, (2) large cardiac injuries, and (3) deep solid organ parenchymal bleeding. Published literature is limited to small case series. The primary goal was to review a recent experience with balloon catheter use for emergency tamponade in a civilian trauma population. METHODS: All patients requiring emergency use of a balloon catheter to tamponade exsanguinating hemorrhage (1998-2009) were included. Patient demographics, injury characteristics, technique, and outcomes were analyzed. RESULTS: Of the 44 severely injured patients (82% presented with hemodynamic instability; mean base deficit=-20.4) who required balloon catheter tamponade, 23 of the balloons (52%) remained indwelling for more than 6 hours. Overall mortality depended on the site of injury/catheter placement and indwelling time (81% if <6 hours; 52% if ≥6 hours; p<0.05). Physiologic exhaustion was responsible for 76% of deaths in patients with short-term balloons. Mortality among patients with prolonged balloon catheter placement was 11%, 50%, and 88% for liver, abdominal vascular, and facial/pharyngeal injuries, respectively. Mean indwelling times for iliac, liver, and carotid injuries were 31 hours, 53 hours, and 78 hours, respectively. Overall survival rates were 67% (liver), 67% (extremity vascular), 50% (abdominal vascular), 38% (cardiac), and 8% (face). Techniques included Foley, Fogarty, Blakemore, and/or Penrose drains with concurrent red rubber Robinson catheters. Initial tamponade of bleeding structures was successful in 93% of patients. CONCLUSIONS: Balloon catheter tamponade can be used in multiple anatomic regions and for variable patterns of injury to arrest ongoing hemorrhage. Placement for central hepatic gunshot wounds is particularly useful. This technique remains a valuable tool in a surgeon's armamentarium.