Author: Brad Kinney MD, Emergency Medicine Physician. April 21, 2019.
- Hypotensive Resuscitation (HR), a foundational principle of Damage Control Resuscitation (DCR), is the practice of avoiding over-resuscitation in the hypotensive traumatically injured patient until definitive hemorrhage control is achieved.
- The true art of HR is swiftly identifying and targeting the balance between perfusion and exsanguination. This target can vary widely depending on the mechanism and pattern of injury, age and comorbidities of the patient, and remainder of the clinical scenario.
- Target a systolic BP of 90-100mmHg, but, this recommendation is based on expert opinion, is controversial, and truthfully there is no obvious, magical evidence-based blood pressure target. The only definitive evidence-based conclusion is that over- and under-resuscitation are BOTH bad. Using blood pressure alone to guide resuscitation is simplistic and dangerous.
- In the ER, where we own only a small part of DCR and HR, our duty is to RAPIDLY triage, RAPIDLY gain IV access, RAPIDLY apply external hemorrhage control, RAPIDLY diagnose and treat immediate life threatening reversible causes of shock (tension pneumothorax, cardiac tamponade, severe hemorrhagic shock), RAPIDLY initiate resuscitation with blood products, and RAPIDLY disposition the hypotensive bleeding trauma patient TO THE OR for definitive internal hemorrhage control. And do all of that in less than ten minutes in the hypotensive trauma patient.
- If the OR is not immediately available, apply DCR and HR principles judiciously to temporize the patient until surgical capabilities are accessible.
- DO NOT APPLY HR to patients with concomitant Traumatic Brain Injury (TBI)!!! Hypotension kills these patients. One systolic blood pressure less than 90mmHg in this population doubles their mortality.
“Defining hypovolemic shock based on the blood pressure value is very liberal and unsuitable, which may misdirect the treating trauma physicians and lead to further compromise of the patient’s condition.”Albreiki et al.
“Hypotensive Resuscitation,” “Permissive Hypotension,” “Permissive Hypotensive Resuscitation,” “Normotensive Resuscitation” all refer to the same concept of avoiding over-resuscitation in the severely traumatically injured until definitive hemorrhage control is established. Colloquially, the mantra warns “don’t pop the clot,” or “over-resuscitating causes rebleeding,” but the art of HR is finding the “temporary balance between exsanguination and perfusion.” Unfortunately, this perfect balance has eluded researchers for decades and is much more complicated than a single blood pressure value due to the plethora of clinical variables in each traumatic scenario. Currently, the nuances of the principle are still hotly debated but the general concept is supported by decades of clinician experience, animal studies, and some human data.
“Injection of a fluid that will increase blood pressure has dangers in itself. Hemorrhage in a case of shock may not have occurred to a marked degree because blood pressure has been too low and the flow too scant to overcome the obstacle offered by the clot.”Walter B. Cannon, Physiologist, World War One.
Immediate versus delayed fluid resuscitation for hypotensive patients with penetrating torso injuries published in the New England Journal of Medicine in 1994 is the landmark study hailed frequently as the strongest human evidence supporting “hypotensive resuscitation,” and review of the data uncovers compelling nuances while invoking additional clinical questions worth exploring. Performed during the “crystalloid resuscitation era,” this was a single center (Houston), prospective, randomized trial comprising a relatively homogeneous (~90% male), young (mean age 31) population who displayed prehospital hypotension (defined as <90 mm Hg systolic, but a mean of 59 mm Hg systolic) after sustaining penetrating trauma (~70% GSW, ~30% stabbing) to the torso. Randomized by odd and even days, an “immediate-resuscitation” group received the standard prehospital intravenous fluid resuscitation while a “delayed resuscitation” group received minimal intravenous resuscitation before reaching the operating room – as displayed clearly in the study data below. The difference in pre-operative resuscitation was vast, and was the only variation in treatment protocol between the two groups.
Interestingly, the systolic blood pressures of the immediate and delayed resuscitation groups only varied upon arrival at the trauma center (79 versus 72mmHg systolic respectively, P = 0.02). While these values were statistically significant, the clinical significance is questionable. There was no difference in the prehospital blood pressures (58 and 59mmHg systolic), and curiously, despite vastly different resuscitation strategies, both groups arrived at the OR with the same blood pressures (112 and 113mmHg systolic, P = 0.98), nearly normotensive.
“Fluids given before surgical control of bleeding lead to either accentuation of ongoing hemorrhage or hydraulic disruption of an effective thrombus, followed by a fatal secondary hemorrhage.”Bickell et al.
The final data revealed a survival benefit in the “delayed resuscitation” group versus the “immediate resuscitation” group (70% versus 62% survival, P = 0.04). Also, in the “immediate resuscitation” group, the hospital stays were longer (14 versus 11 days, P = 0.006) and there was a non-significant trend toward more postoperative complications. While this study shows that “less is more” with regard to pre-operative fluid resuscitation in the hypotensive penetrating torso trauma patient, it seemingly raises many more questions as well.
- Can this approach be extrapolated to blunt trauma? Or outside of this single center? To the elderly or pediatric patients? To females? To the pregnant?
- Can this approach be extrapolated to today’s practice of limited crystalloid and initial blood product resuscitation? Or was it actually the nature and not volume of the crystalloid that decreased survival?
- Where is the balance between over- and under-resuscitation? What specific blood pressure value should we target? Should we use MAP or systolic pressures? Or should we utilize the entire clinical picture and use the blood pressure only as a general guide?
- Have we been resuscitating trauma patients to death? Maybe the body has an incredible way of compensating? Were these findings skewed due to the young population and their ability to compensate?
Finally, maybe all that we know from this study is what the authors eloquently and concisely summarized below. DON’T RESUSCITATE TOO MUCH OR TOO EARLY.
“For hypotensive patients with penetrating torso injuries, delay of aggressive fluid resuscitation until operative intervention improves the outcome.”Bickell et al.
Blood Pressure at which Rebleeding Occurs after Resuscitation in Swine with Aortic Injury was a fascinating study published in The Journal of TRAUMA in 2003. After scores of animal studies validated the concept that “over-resuscitation causes rebleeding,” this was the first study that attempted to define a specific blood pressure target. Aortotomies were performed in 62 anesthetized pigs. After initial bleeding and eventual hemostasis, the hypotensive pigs were resuscitated with intravenous crystalloid at different rates and at different times. Rebleeding occurred reproducibly at a MAP (perfusion pressure) of 64(+/-2) and a systolic of 94(+/-3) regardless of resuscitation rate or time. The authors concluded that “the optimal endpoint of resuscitation in patients without definitive hemorrhage control would then be below this rebleeding pressure.” While this is not human data and is derived from a very controlled laboratory environment with few variables, swine are the closest physiologic approximation of humans, so this data at least offers some insight into a general blood pressure goal.
Permissive hypotensive resuscitation in adult patients with traumatic haemorrhagic shock: a systematic review published in 2018 summarizes the best evidence to date regarding hypotensive resuscitation. Ten RCTs and cohort studies included in the final analysis showed a survival benefit in the “low volume” resuscitation groups versus the “large volume” resuscitation groups. The authors do warn though that drawing definitive conclusions from this small, heterogenous, and sometimes biased body of evidence is erroneous, and that much more research is needed before HR is unreservedly embraced.
“Current knowledge on the optimal fluid strategy still lacks rigorous evidence from clinical trials on humans; thus huge debate exists among trauma healthcare providers about the safety of current practice regarding fluid therapy.”Albreiki et al.
In the last twenty years, the treatment paradigm in the severely injured hypotensive patient has swung wildly from immediate aggressive resuscitation to minimal delayed resuscitation. We no longer attempt to achieve normal physiologic parameters initially, but we permissively allow some hypotension to avoid “popping the clot.” But have we gone from “feast to famine” when the truth actually lies somewhere in the middle? We must not forget that hemorrhagic shock kills, and kills quickly. We must err on the side of resuscitation, but we must resuscitate wisely and carefully. We have not yet discovered a magical blood pressure number to target – and we may never, but we must enlist our clinical skills and experience to find the right way forward for each individual patient with regard to hypotensive resuscitation.
“The labelling of patients with low blood pressure with a diagnosis of haemorrhagic shock, may diminish the quality of care delivery; thus fluid therapy should be tailored for each individual based on their current state of shock. Critical clinical judgment of diagnosing a patient with profound shock should rely on assessing various vital signs and the patient’s clinical condition.”Albreiki et al.
- Albreiki M, Voegeli D. Permissive hypotensive resuscitation in adult patients with traumatic haemorrhagic shock: a systematic review. Eur J Trauma Emerg Surg (2018) 44:191–202. PMID: 29079917.
- Bickell WH, et al. Immediate versus delayed fluid resuscitation for hypotensive patients with penetrating torso injuries. N Engl J Med. 1994 Oct 27;331(17): 1105-9. PMID: 7935634. Free Copy.
- Sondeen JL, Coppes VG, Holcomb JB. Blood pressure at which rebleeding occurs after resuscitation in swine with aortic injury. J Trauma. 2003 May; 54 (5 Suppl): S110-7. PMID: 12768112.
- Wiles MD. Blood pressure management in trauma: from feast to famine? Anesthesia 2013, 68, 445-452. PMID: 23550831.
- Damage Control Resuscitation. Joint Trauma System Clinical Practice Guideline. 03 February 2017. Accessed 15DEC2018, DCR JTS CPG.