Multisystem Trauma

Balanced Resuscitation

Historically, early trauma resuscitation involved large volumes of crystalloid and the last decade has welcomed a new concept in early trauma resuscitation. This change in approach to the resuscitation of the injured patient stresses a balanced resuscitation, using high ratios of red blood cells (RBCs), plasma, and platelets that come close to that of whole blood as early as possible in the care of trauma patients. Whole blood itself has increasingly become available and applied in both the prehospital and hospital setting. The Pragmatic Randomized Optimal Platelet and Plasma Ratios (PROPPR) Trial demonstrated that a 1:1:1 ratio of units of plasma to platelets to RBCs is not only safe but effective. Although not resulting in a mortality benefit at 24 hours and 30 days, a 1:1:1 ratio compared with a 1:1:2 ratio resulted in more patients achieving hemostasis and fewer deaths resulting from exsanguination in the first 24 hours.

Overaggressive crystalloid resuscitation accentuates coagulopathy through dilution of blood components, adds to acidosis through pH alteration, and exacerbates hypothermia via installation of large volumes of cold solution. In order to combat this, balanced resuscitation limits the use of crystalloid in the early resuscitation of the critically injured patient. In fact, the American College of Surgeons Committee on Trauma has recently changed the ATLS approach to limit initial crystalloid infusion from 2 L down to 1 L before adding blood products.

Another mainstay of balanced resuscitation is the concept of permissive hypotension. This allows an adequate but not normal blood pressure in order to preserve vital organ function as well as prevent further hemodilution and disruption of established clot in the patient with ongoing hemorrhage. The literature is mixed but a recent meta-analysis shows that permissive hypotension may not only show a reduction in blood loss and blood product utilization but also a survival advantage.

Many centers have established massive transfusion protocols that permit hospital blood banks to release rapidly standard quantities of uncrossmatched type O-negative red blood cells, plasma, platelets and, increasingly, low titer O-negative whole blood at regular intervals until hemorrhage is controlled. Despite being a strain on hospital blood banks, such protocols appear to be justified by studies showing decreased mortality as low as 15%, decreased overall component usage, and avoidance of overuse. Scoring systems, such as the Assessment of Blood Consumption (ABC) score, designed to predict need for massive transfusion, may help guide activation of such protocols. Trade-offs include risks of transfusion reaction, transmission of blood-borne diseases, and infectious and immune complications.

Hyperfibrinolysis has been recognized as a contributor to ongoing coagulopathy. Although normally striking a balance with thrombosis, increased fibrinolysis in some trauma patients leads to clot breakdown while hemorrhage is still ongoing. Tranexamic acid (TXA) has long been used to stem bleeding in elective surgery. Within the last decade, the use of TXA has been increasingly studied in trauma patients. Although it remains controversial, there is evidence to support its early use in the bleeding trauma patient. The Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage-2 (CRASH-2) trial showed a small but significant reduction in mortality and death secondary to bleeding with TXA. Thrombotic events were not different between the treatment and placebo groups. Late administration (> 3 hours after injury) of TXA showed an increase in mortality.

Choice of ICU Resuscitation Fluid

The fluid of choice for resuscitation after hemorrhage control in critically ill and injured patients is still controversial. Crystalloid solutions are less expensive but are theoretically less effective for maintaining intravascular volume. Although colloid solutions are more expensive, they theoretically remain longer in the intravascular space relative to crystalloid, and thus smaller volumes are required for infusion. Studies have not consistently shown one to be superior to the other for ICU resuscitation. The largest prospective randomized trial to address this issue is the Saline versus Albumin Fluid Evaluation (SAFE) trial, which compared normal saline with 4% albumin for resuscitation in ICU patients. This trial showed no mortality benefit of albumin over saline in a large cohort of ICU patients at 28 days. However, there was a lower amount of total fluid utilized in the albumin group in the first 4 days, a decrease in heart rate, and an increase in central venous pressure, although no change in mean arterial pressure. Post hoc subgroup analysis suggested that trauma patients in the albumin group may have fared worse than those in the saline resuscitation group; nonetheless this was inconclusive because this group also had a higher rate of death from traumatic brain injury.

Although the issue of crystalloid versus colloid has not been settled definitively, it is clear that overresuscitation can occur with any fluid and lead to a variety of complications, both immediate and delayed. Thus the choice of resuscitation fluid is probably less important than the timing and volume of resuscitation.

Transfusion Triggers

Anemia is common in the postinjury period, especially in those injured patients admitted to the ICU. Transfusion of blood products solely based on laboratory values should be approached cautiously. When other factors are controlled for, blood transfusion correlates with organ dysfunction, mortality, and ICU length of stay. Studies in trauma patients have suggested that blood transfusion is an independent predictor of worsened outcomes in patients with solid organ injuries. Large controlled trials in critically ill patients have suggested that restrictive blood transfusion practices (e.g., a hemoglobin transfusion trigger of 7 g/dL) are equal or superior in mortality to more liberal transfusion practices (e.g., a transfusion trigger of 10 g/dL). A smaller body of literature suggests the same is true in the injured population. Post hoc analysis of the Transfusion Requirements in Critical Care (TRICC) trial confirmed the safety of restrictive transfusion practices in trauma patients. Both protocols are similar in terms of mortality and incidence of multiple organ dysfunction. A postinjury practice management guideline is safe and cost effective. Although the transfusion trigger for patients with active cardiac ischemia and patients with head injury is not known, it is likely that most other injured patients with hemorrhage control will not benefit from liberal transfusion strategies. The concept of transfusion threshold should be applied very carefully in the trauma population: any threshold for transfusion presupposes control of hemorrhage. Stated more bluntly, transfusion thresholds do not apply to patients who are still bleeding.

Endpoints of Resuscitation

Clinical judgment is an essential component of multisystem trauma resuscitation. Not all endpoints are applicable to all patients, and a global perspective of the patient’s status is tantamount to the attention to minute details. Endpoints can be classified as clinical, laboratory, or monitoring.

The initial assessment of the trauma patient begins with evaluating and treating the ABCs, and the ongoing care should ensure that the ABCs remain intact. Changes in hemodynamics or oxygenation should prompt reassessment of airway, breathing, and circulation, especially confirming proper position and function of endotracheal tube, chest tubes, catheters, monitors, and surgical drains. In the early postinjury period, hypotension should be assumed to be caused by hemorrhage until proven otherwise.

Traditional clinical indicators such as blood pressure, heart rate, urine output, distal perfusion, and mentation should be used as a starting point for assessing resuscitation. Abnormalities of these basic signs should prompt thorough physical examination and close monitoring of interventions (blood component therapy, fluid challenges, analgesia, sedation). Several caveats relevant to the injured patient should be mentioned: tachycardia is nonspecific and may represent hypovolemia, pain, agitation, presence of illicit substances, or myocardial injury. On the other hand, tachycardia may be absent or blunted in patients who were receiving beta-blocker therapy before the injury. Regarding blood pressure, essential hypertension is widely prevalent, and a “normal” blood pressure may in fact represent relative hypotension and hypovolemia. Finally, mental status may be altered by hypoperfusion, brain injury, the presence of illicit substances, or baseline chronic encephalopathic diseases such as dementia.

Laboratory studies are useful for assessing endpoints of resuscitation. Postinjury acidosis, as manifested by persistently elevated lactic acid or by base deficit (or persistently low serum bicarbonate), suggests occult hypoperfusion or devitalized tissue. Although the initial value (i.e., immediately on arrival to the trauma center) has correlation to outcome, the trend over hours is more useful for assessing treatments and predicting mortality. Persistent acidosis is a grave sign. Failure to normalize serum lactic acid level by 24 hours after injury is associated with worse outcome in injured patients. Similarly, persistent base deficit correlates with worse outcomes.

Viscoelastic tests such as thromboelastography (TEG) and rotational thromboelastometry (ROTEM) can also guide blood component therapy and may be superior to conventional coagulation tests such as PT/INR and PTT for guiding the correction of coagulopathy. ProTime (PT) and activated partial thromboplastin time (aPTT) are usually performed at 37°C. Thus in the normothermic patient, abnormalities of PT and aPTT indicate clotting factor deficiency. However, in the hypothermic patient, these studies fail to assess the qualitative deficiency of coagulation and thus underestimate coagulopathy. TEG may demonstrate coagulopathy with improved fidelity irrespective of body temperature. TEG measures the dynamics of clot development, stabilization/strength, and dissolution. A prolonged R-time may indicate the need for plasma transfusion. An increased K-time or decrease in alpha angle may denote hypofibrinogenemia. A low maximum amplitude reveals low platelet function. LY-30 or lysis of clot at 30 minutes is increased with hyperfibrinolysis and treatment with TXA may be indicated. Component therapy may be directed toward these coagulopathic findings as stated earlier.

Trauma patients who suffer deterioration of these indicators should be presumed to have ongoing or uncontrolled hemorrhage in the thorax, abdomen, retroperitoneum, and extremities. After physical examination, chest radiograph and focused abdominal sonography for trauma (FAST) may help triage the chest and abdominal cavities by diagnosing or excluding recurrent hemothorax or new hemoperitoneum. Hemorrhage in the thorax, abdomen, or extremities that is brisk enough to result in hypotension or acidosis often requires control in the operating room. However, hemorrhage from hepatic lacerations, pelvic fractures, or retroperitoneal injury may be difficult to control in the operating room and instead may require interventional radiology with angiography for diagnosis and embolization for treatment.

Despite the vast cumulative experience with central venous pressure (CVP) monitoring, the amount of objective data available to guide clinicians in deciding which injured patients to monitor are limited. CVP monitoring is probably indicated for patients who have hemorrhage control but have not responded appropriately to initial volume resuscitation or for patients with chronic cardiac and pulmonary disease and low physiologic reserve. The endpoints are similar to those of postsurgical patients. When CVP is unavailable, bedside ultrasonography may be used to assess inferior vena cava diameter, respiratory variability and collapsibility, which can be a surrogate for right atrial pressures and volume status.

The pulmonary artery (PA) catheter remains controversial in trauma patients. Although PA catheterization is theoretically attractive and commonly used, retrospective and prospective studies of critically ill patients have not consistently demonstrated that it has a mortality benefit compared with central venous monitoring. Furthermore, these studies typically have relatively small numbers of injured patients, making results more difficult to apply to the trauma patient. It is likely that the benefit of the PA catheter is not in its presence or absence, but in how the clinician uses the data that are available. Ultimately, the usefulness of the PA catheter may lie in optimizing ventricular preload and overall cardiac efficiency and in preventing over -resuscitation.

Many methods of assessing regional visceral perfusion have been proposed as adjuncts to clinical examination, laboratory studies, and central monitoring. Gastric tonometry demonstrates good correlation with other indices of global perfusion, but it has not found widespread clinical acceptance. Sublingual capnometry may also prove to be a useful, noninvasive marker of perfusion. Esophageal Doppler and surface ultrasound techniques have been investigated as noninvasive means of assessing cardiac output and preload, respectively. Further studies will clarify their roles in achieving adequate resuscitation of the injured patient.