Hypotensive Trauma Patients
Hypotensive Trauma Patients
For the trauma patient in hemorrhagic shock, the choice and amount of resuscitative fluids are issues of continued debate. Current Advanced Trauma Life Support® guidelines recommend treating patients in hemorrhagic shock by infusing 2 L of isotonic or near-isotonic crystalloid solutions, followed by blood products. However, in the last decade, 2 major concepts have challenged this approach. The first is the concept of “hypotensive resuscitation” (ie, the premise that resuscitation to “normal” blood pressures may increase bleeding at a site of uncontrolled hemorrhage). The second is the use of HTS as an alternative resuscitative fluid. It is cheap, is portable, improves microcirculation, and has immunomodulatory properties. It allows “small volume” resuscitation (4 mL/kg) in austere environments and empowers a single medic to treat multiple combat casualties. The 1999 Institute of Medicine report on resuscitation of combat casualties recommended HTS with dextran as the optimal resuscitation fluid in that environment.36 HTS may also have practical advantages for civilian emergency medical services. Due to short transport times, restoration of mean arterial pressure (MAP) for patients with TBI is difficult with traditional crystalloid solutions. HTS with dextran administered by prehospital providers may restore MAP more quickly and reduce the potential for secondary neurologic injury in TBI patients.
In 1980, de Felippe et al reported astonishing results of survival in 11 of 12 patients with refractory hemorrhagic shock who were treated with HTS.37 That same year, researchers from the University of Sao Paulo published the first animal study on the use of HTS.38 They subjected dogs to hemorrhagic shock and reported that 7.5% sodium chloride (NaCl) infused in a volume equal to only 10% of shed blood volume rapidly restored blood pressure.38 These initial studies prompted several subsequent trials to evaluate the use of HTS for the treatment of hemorrhagic shock.
From 1987 to 2011, there were 10 randomized controlled trials comparing the use of HTS to isotonic crystalloid solutions in hypotensive trauma patients.34,39-47 Many of these trials had very low patient numbers and compared bolus therapy of 7.5% HTS with dextran to 7.5% HTS or normal saline, followed by standard resuscitation with crystalloids and blood products, if necessary. Most of the trials found that 7.5% HTS with dextran increased MAP more than a similar volume of isotonic crystalloid solution. No significant side effects were noticed. Unfortunately, no studies showed an overall mortality benefit. In post-hoc analysis, some studies showed mortality difference in certain subgroups, such as those requiring surgery40 or when MAP was < 70 mm Hg.39 Vassar et al remarked that, while there was no difference in overall mortality, patients who received HTS with dextran had better survival than predicted by trauma scores.41
Bunn and colleagues performed a Cochrane review to determine whether HTS decreases mortality in patients with hypovolemia from causes other than hemorrhage. Their search included randomized trials comparing isotonic and near-isotonic crystalloid solutions to HTS in patients with trauma, with burns, or who were undergoing surgery. Fourteen trials with a total of 956 participants were included in the meta-analysis. They concluded that the confidence intervals for relative risk were wide, and no conclusions could be drawn about a mortality benefit.30
In 2011, a multicenter double-blind randomized controlled trial sponsored by the National Institutes of Health examined whether the effect of 7.5% HTS (with and without 6% dextran 70) compared to normal saline improved mortality in hypotensive blunt and penetrating trauma patients.48 This study, which included 853 patients, is the largest study to date. Patients were randomized to receive a 250-mL prehospital bolus of 7.5% HTS with dextran 70, 7.5% HTS, or normal saline. Like the previously mentioned National Institutes of Health TBI study, it was terminated early by the Data and Safety Monitoring Board after they found that patients who received HTS and did not receive blood transfusions in the first 24 hours had a higher mortality (HTS with dextran: 10%; HTS: 12.2%; normal saline: 4.8%). The authors of this study offered 2 possible explanations for this early mortality. The first is that the patients treated with HTS had a higher rate of early hemorrhage (possibly precipitated by the HTS). However, if increased bleeding was the primary mechanism for earlier mortality, one would anticipate higher mortality among penetrating rather than blunt trauma patients; the opposite effect was seen in this study. Moreover, those patients requiring emergent hemorrhage control who received hypertonic fluids did not have an increase in mortality. The other, more likely, explanation is that the administration of HTS caused a change in physician behavior that delayed the recognition of shock and subsequent transfusion. It is unclear whether any of these early deaths were preventable, as there was no overall difference in the 28-day survival between the groups.48
Summary Of The Use Of Hypertonic Saline In Hypotensive Trauma Patients
HTS improves hemodynamics for trauma patients in hemorrhagic shock. Small-volume resuscitation may make HTS an ideal crystalloid solution for combat casualty situations. Most studies on the use of HTS in hypotensive trauma patients administered a 250-mL bolus of 7.5% HTS with dextran. While small trials suggest that there may be some subsets of patients who may benefit from the use of HTS (eg, those requiring surgery or patients with SBP < 70 mm Hg), there is currently no strong evidence to support its use in hypotensive trauma patients. Further, it may worsen mortality in patients who do not receive blood transfusions in the first 24 hours, as it may delay the recognition of shock and subsequent transfusion.
Jeffrey A. Holmes, MD
February 4, 2013