Controversy: whether or not aggressive fluid resuscitation is beneficial in the setting of hypotensive trauma. Hypovolemic trauma patients do reliably respond to volume infusion, thus in the past ATLS recommended administration of 2L IVF as rapidly as possible. This recommendation has recently been questioned, as the downsides of dilutional anemia in the trauma setting (namely decreased O2 delivery, hypothermia, coagulopathies, and electrolyte abnormalities) and hypertension in the setting of hemorrhage (increased bleeding) the have come to light. Aggressive fluid administration often leads to a transient rise in BP which leads to increased bleeding and another episode of hypotension, producing a vicious cycle. For this reason, resuscitation has been divided into two phases: early (during active hemorrhage) and late (when hemorrhage has been controlled).
Data Supporting Routine Aggressive Fluid Resuscitation:
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Equivocal Data Regarding Routine Aggressive Fluid Resuscitation:
Dutton randomized 110 trauma patients with hypotension (defined as SBP < 90 mm Hg) to a systolic goal of 100 mm Hg versus 70 mm Hg until the completion of surgery. In contrast to Bickell, Dutton found no difference in mortality, although the study may have been confounded by a difference in injury severity scores in favor of the 100 mm Hg group (19.6 vs 23.4) as well as the profundity of shock at presentation. At 24 hours, lactate and base deficit normalized in both groups, and both fluid and blood product requirements were similar. Importantly, the low-pressure group had a significantly longer hospital and ICU length of stay [Dutton RP et al. J Trauma 52: 1141, 2002]
Data Refuting Routine Aggressive Fluid Resuscitation:
In 1965, an animal (dog) study comparing blood loss secondary arterial injury in the setting of multiple differing conditions (BP, vasoconstrictors/vasodilation, fluid status, transfusion) showed that blood loss was minimized in hypotensive animals, followed by controls (no volume or vasoconstrictors), those who received vasoconstrictors, and those who received volume infusions (i.e. those who received volume had the most blood loss) [Shaftan GW et al. Surgery 58: 851, 1965]. Sharftan’s study is supported by multiple other animal studies showing that large volumes of resuscitation fluid can be harmful [Owens TM et al. J Trauma 39: 200, 1995; Riddez L et al. J Trauma 44: 1, 1998; Sakles JC et al. Ann Emerg Med 29: 392, 1997; Capone A et al. Resuscitation 29: 143, 1995], the best of which show no difference in cardiac output and/or regional perfusion between moderate and large-volume resuscitation.
A 1994 consensus panel on resuscitation from hemorrhagic shock suggested that spontaneous hemostasis and long-term survival could be maximized by limiting resuscitation fluids during the period of active bleeding (early hemorrhage/resuscitation) while seeking to keep perfusion only above the threshold for ischemia [Shoemaker WC et al. Crit Care Med 24S: S12, 1996] – note that some mammalian species are capable of sustaining MAP as low as 40 mm Hg for periods as long as 2 hours without deleterious effects [Miller, Chapter 63] although the human cerebral autoregulatory curve is thought to have a lower inflection point at 50 mm Hg in non-hypertensive patients (higher in those with a history of hypertension).
Bickell et al randomized 100 penetrating torso trauma patients to standard of care (up to 2L of prehospital crystalloid, average was 870 cc infused) versus delayed resuscitation (no fluid until reaching the OR, averaged 92 cc prehospital). At the time of surgery, blood pressures were identical but the standard of care group had markedly lower hemoglobin (10.7 vs 11.5 g/dL). In the operating room, there were no differences in the amount of fluid administered, although the prehospital resuscitation group required more rapid fluid administration. The delayed-resuscitation group had improved survival to discharge (70% versus 62%, p = .04) as well as reduced length of stay (11 days vs. 14 days, p = 0.006) [Bickell WH et al. NEJM 331: 1105, 1994]
The notion that aggressive fluid resuscitation can be detrimental prior to controlling hemorrhage is supported by two retrospective studies. In the first, 4856 EMS patients were compared with 926 non-EMS patients, and linear model analysis controlling for age, gender, mechanism of injury, cause of injury, Injury Severity Score (ISS), and severe head injury showed a crude mortality rate of 9.3% in the EMS group versus 4.0% in the non-EMS group (RR 2.32, p < .001), after adjustment for ISS, the RR fell to 1.60 (p = .002). Subgroup analysis showed that patients with ISS > 15 were twice a likely to die if transported by EMS (RR 28.8% vs 14.1%) [Demetriades D et al. Arch Surg 131: 133, 1996]. In the second, 527 patients at Maryland’s Shock Trauma Center (which has had the RIS since 1990) were compared to the STC Trauma Registry as well as historical controls that did not have access to the RIS. For patients with access to the RIS, 9724 ml were infused, and overall survival was significantly less than expected (52.9% vs. 61.8%, p < 0.001). In penetrating trauma the survival rates were similar, thus the differences are likely due to blunt trauma (48.8% vs. 63.0% survival, p < 0.001). In patients who received less than 6000 ml via the RIS, there was no difference, whereas in those that did, there was a significant mortality difference (37.2% vs. 57.2%, p < 0.0001). Compared to matched controls, those who received fluids via the RIS had a 4.8 times RR of dying (95% CI 2.4-7.1) [Hambly PR et al. Resuscitation 31: 127, 1996]
Despite the accumulating evidence supporting fluid restriction in the ED/preoperative phase of trauma, one must also keep in mind the different physiology of the patient in hemorrhagic shock (maximal vasoconstriction secondary to endogenous epinephrine) and the patient sedated or under anesthesia (vasodilation due to exogenous pharmacologic agents). At the least, the use of anesthetic agents should be minimized. Furthermore, patients at-risk for ischemic complications (TBI, known ischemic heart disease, elderly) have been excluded from most of the above studies, and intentional hypotension may be advantageous in those groups, until it is shown, intentional hypotension should not be used in at-risk populations.