Current trends in resuscitation strategy for the multiply injured patient

Fluid Therapy in Trauma

Advances in shock resuscitation have occurred as a result of various military conflicts. Primary objective of trauma care is to minimize or reverse shock, avoiding the lethal triad of hypothermia, acidosis, and coagulopathy. The concept of Damage Control Resuscitation has evolved along with "damage control surgery" which includes hypotensive and haemostatic resuscitation, where small aliquots of fluid are infused, with hypovolaemia and hypotension tolerated as a necessary evil until definitive haemorrhage control can be achieved. In the initial stages of trauma resuscitation the precise fluid, crystalloid or colloid, used is probably not important as long as an appropriate volume is given. Haemostatic resuscitation includes early use of fresh frozen plasma in a 1:1 ratio with packed red cells with emphasis on whole blood, frequent cryo precipitates and platelets and the use of recombinant Factor VII for control of bleeding.

Fluid resuscitation in multiple trauma patients

PURPOSE OF REVIEW

Fluid resuscitation in trauma patients with hemorrhagic shock is controversially discussed in the literature. The coincidence of brain injury complicates management of these patients. This article summarizes the current knowledge on nonblood component fluid resuscitation and choice of fluids in patients with multiple trauma.

RECENT FINDINGS

Whereas current evidence suggests the efficacy of fluid therapy in hemorrhagic shock without active bleeding, experimental and clinical data demonstrate that aggressive volume challenge may be futile or even deleterious in the setting of uncontrolled hemorrhage. Large amounts of isotonic crystalloids may be associated with hypothermia, acidosis and inflammation. In patients with traumatic brain injury hypertonic solutions may positively influence inflammation and intracranial pressure without affecting neurologic outcome or mortality.

SUMMARY

To date no large-scale clinical studies exist to either support or refute the use of nonblood component fluid resuscitation of hemorrhagic shock in trauma patients. The optimal choice of fluid remains to be determined, but existing evidence suggests avoiding crystalloids in favor of hypertonic solutions. The role of modern, iso-oncotic colloids in the treatment of hemorrhagic shock has not yet been sufficiently defined. In patients with concomitant brain injury, arterial hypotension must be avoided and infusion of hypotonic solutions is obsolete, whereas administration of hypertonic solutions may exert beneficial effects beyond hemodynamic stabilization.

Fixed volume or fixed pressure: a murine model of hemorrhagic shock

It is common knowledge that severe blood loss and traumatic injury can lead to a cascade of detrimental signaling events often resulting in mortality. ^{1, 2, 3, 4, 5} These signaling events can also lead to sepsis and/or multiple organ dysfunction (MOD). ^{6, 7, 8, 9} It is critical then to investigate the causes of suppressed immune function and detrimental signaling cascades in order to develop more effective ways to help patients who suffer from traumatic injuries. ¹⁰ This fixed pressure Hemorrhagic Shock (HS) procedure, although technically challenging, is an excellent resource for investigation of these pathophysiologic conditions. ^{11, 12, 13} Advances in the assessment of biological systems, i.e. Systems Biology have enabled the scientific community to further understand complex physiologic networks and cellular communication patterns. ¹⁴ Hemorrhagic Shock has proven to be a vital tool for unveiling these cellular communication patterns as they relate to immune function. ^{15, 16, 17, 18} This procedure can be mastered! This procedure can also be used as either a fixed volume or fixed pressure approach. We adapted this technique in the murine model to enhance research in innate and adaptive immune function. ^{19, 20, 21} Due to their small size HS in mice presents unique challenges. However due to the many available mouse strains, this species represents an unparalleled resource for the study of the biologic responses. The HS model is an important model for studying cellular communication patterns and the responses of systems such as hormonal and inflammatory mediator systems, and danger signals, i.e. DAMP and PAMP upregulation as it elicits distinct responses that differ from other forms of shock. ^{22, 23, 24, 25} The development of transgenic murine strains and the induction of biologic agents to inhibit specific signaling have presented valuable opportunities to further elucidate our understanding of the up and down regulation of signal transduction after severe blood loss, i.e. HS and trauma ^{26, 27, 28, 29, 30}.

There are numerous resuscitation methods (R) in association with HS and trauma. ^{31, 32, 33, 34} A fixed volume resuscitation method of solely lactated ringer solution (LR), equal to three times the shed blood volume, is used in this model to study endogenous mechanisms such as remote organ injury and systemic inflammation. ^{35, 36, 38} This method of resuscitation is proven to be effective in evaluating the effects of HS and trauma ^{38, 39}.

Clinical and cellular effects of hypothermia, acidosis and coagulopathy in major injury

BACKGROUND

Hypothermia, acidosis and coagulopathy have long been considered critical combinations after severe injury. The aim of this review was to give a clinical update on this triad in severely injured patients.

METHODS

A non-systematic literature search on hypothermia, acidosis and coagulopathy after major injury was undertaken, with a focus on clinical data from the past 5 years.

RESULTS

Hypothermia (less than 35 °C) is reported in 1·6-13·3 per cent of injured patients. The occurrence of acidosis is difficult to estimate, but usually follows other physiological disturbances. Trauma-induced coagulopathy (TIC) has both endogenous and exogenous components. Endogenous acute traumatic coagulopathy is associated with shock and hypoperfusion. Exogenous effects of dilution from fluid resuscitation and consumption through bleeding and loss of coagulation factors further add to TIC. TIC is present in 10-34 per cent of injured patients, depending on injury severity, acidosis, hypothermia and hypoperfusion. More expedient detection of coagulopathy is needed. Thromboelastography may be a useful point-of-care measurement. Management of TIC is controversial, with conflicting reports on blood component therapy in terms of both outcome and ratios of blood products to other fluids, particularly in the context of civilian trauma.

CONCLUSION

The triad of hypothermia, acidosis and coagulopathy after severe trauma appears to be fairly rare but does carry a poor prognosis. Future research should define modes of early detection and targeted therapy.

Recognition and management of major vessel injury during laparoscopy

Laparoscopy is one of the most commonly performed procedures in the United States. Injury to a major retroperitoneal vessel occurs in 0.3% to 1.0% of procedures, most commonly during laparoscopic entry while placing the Veress needle or primary trocar. Fatal outcome can be related to massive gas embolism or exsanguination. Recommended treatment for gas embolism can range from supportive measures to external chest compression and insertion of a central line to withdraw gas from the right side of the heart. Recommended treatment of major vessel injury with massive hemorrhage consists of rapid laparotomy and control of hemorrhage using direct pressure until a surgeon experienced in vascular procedures arrives. When a major vessel injury occurs in a surgical facility distant from a medical center and without an available surgeon with vascular experience, based on the trauma literature, we recommend temporary control of blood loss using abdominal packing and closure (i.e., "damage control surgery") and judicious resuscitation (i.e., "damage control resuscitation") before transportation to a medical center.

"Metabolic staging" after major trauma - a guide for clinical decision making?

Metabolic changes after major trauma have a complex underlying pathophysiology. The early posttraumatic stress response is associated with a state of hyperinflammation, with increased oxygen consumption and energy expenditure. This hypercatabolic state must be recognized early and mandates an early nutritional management strategy. A proactive concept of early enteral "immunonutrition" in severely injured patients, is aimed at counterbalancing the negative aspects of hyperinflammation and hypercatabolism in order to reduce the risk of late complications, including infections and posttraumatic organ failure. Recently, the concept of "metabolic staging" has been advocated, which takes into account the distinct inflammatory phases and metabolic phenotypes after major trauma, including the "ischemia/reperfusion phenotype", the "leukocytic phenotype", and the "angiogenic phenotype". The potential clinical impact of metabolic staging, and of an appropriately adapted "metabolic control" and nutritional support, remains to be determined.