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ROC trials update on prehospital hypertonic saline resuscitation in the aftermath of the US-Canadian trials

Abstract

The objectives of this review are to assess the current state of hypertonic saline as a prehospital resuscitation fluid in hypotensive trauma patients, particularly after the 3 major Resuscitation Outcomes Consortium trauma trials in the US and Canada were halted due to futility. Hemorrhage and traumatic brain injury are the leading causes of death in both military and civilian populations. Prehospital fluid resuscitation remains controversial in civilian trauma, but small-volume resuscitation with hypertonic fluids is of utility in military scenarios with prolonged or delayed evacuation times. A large body of pre-clinical and clinical literature has accumulated over the past 30 years on the hemodynamic and, most recently, the anti-inflammatory properties of hypertonic saline, alone or with dextran-70. This review assesses the current state of hypertonic fluid resuscitation in the aftermath of the failed Resuscitation Outcomes Consortium trials.

HSD; Hemorrhagic Shock; Inflammation; Volume Expander; Small Volume


INTRODUCTION

Traumatic injury is the leading cause of death in adults <44 years old, and its incidence is increasing worldwide (11. Kauvar DS, Wade CE. The epidemiology and modern management of traumatic hemorrhage: US and international perspectives. Crit Care. 2005;9 Suppl 5:S1-9, http://dx.doi.org/10.1186/cc3779.
http://dx.doi.org/10.1186/cc3779...
). Among traumatic injuries, hemorrhage and traumatic brain injury are leading causes of death in both the military and civilian populations, with hemorrhage-related deaths occurring early (22. Bellamy RF. The causes of death in conventional land warfare: implications for combat casualty care research. Mil Med. 1984;149(2):55-62.

3. Sauaia A, Moore FA, Moore EE, Moser KS, Brennan R, Read RA, Pons PT. Epidemiology of trauma deaths: a reassessment. J Trauma. 1995;38(2):185-93.
-44. Champion HR, Bellamy RF, Roberts CP, Leppaniemi A. A profile of combat injury. J Trauma. 2003;54(5 Suppl):S13-9.). Both the early control of bleeding and resuscitation, which restores blood volume and re-establishes tissue perfusion to vital organs, are paramount. However, the use of fluid for prehospital resuscitation of trauma patients in the civilian sector remains controversial, based on short transport times, the likelihood of infusing only small volumes of fluid and the concern of causing more bleeding in cases of uncontrolled or non-compressible hemorrhage. In the military, well-recognized limitations make far-forward resuscitation difficult (55. Dubick MA, Atkins JL. Small-volume fluid resuscitation for the far-forward combat environment: current concepts. J Trauma. 2003;54(5 Suppl):S43-5.

6. Dubick MA, Kramer GC. Hypertonic saline dextran (HSD) and intraosseous vascular access for the treatment of haemorrhagic hypotension in the far-forward combat arena. Ann Acad Med Singapore. 1997;26(1):64-9.
-77. Mabry RL, Holcomb JB, Baker AM, Cloonan CC, Uhorchak JM, Perkins DE, Canfield AJ, Hagmann JH. United States Army Rangers in Somalia: an analysis of combat casualties on an urban battlefield. J Trauma. 2000;49(3):515-28;discussion 28-9.). Nevertheless, the challenges of prehospital fluid resuscitation are further highlighted by evidence from experimental animals, which suggests that interventions to re-establish homeostasis may need to be initiated within 30 minutes after injury to assure survival (88. Nelson AW, Swan H. Hemorrhage - Responses Determining Survival. Circulatory Shock. 1974;1(4):273-85.).

In general, the ideal resuscitation fluid to treat the severely injured, hypotensive trauma patient should be safe, should expand blood volume, should improve oxygen delivery and possibly reduce oxygen demand, should not increase bleeding and should be easy to administer as well as be able to achieve these goals with a small volume. Research into the possibility of such a fluid was stimulated more than 30 years ago by encouraging results observed in an early study in hemorrhaging dogs (99. Velasco IT, Pontieri V, Rocha e Silva M, Jr., Lopes OU. Hyperosmotic NaCl and severe hemorrhagic shock. Am J Physiol. 1980;239(5):H664-73.), which were treated with a 4 ml/kg bolus of 7.5% hypertonic saline (HS). This bolus volume was equivalent to 10% of the shed blood volume, and the dogs experienced rapid improvements in blood pressure, cardiac output and, most importantly, survival. Later experiments performed in sheep (1010. Smith GJ, Kramer GC, Perron P, Nakayama S, Gunther RA, Holcroft JW. A comparison of several hypertonic solutions for resuscitation of bled sheep. J Surg Res. 1985;39(6):517-28, http://dx.doi.org/10.1016/0022-4804(85)90120-9.
http://dx.doi.org/10.1016/0022-4804(85)9...
) and swine (1111. Maningas PA, DeGuzman LR, Tillman FJ, Hinson CS, Priegnitz KJ, Volk KA, et al. Small-volume infusion of 7.5% NaCl in 6% Dextran 70 for the treatment of severe hemorrhagic shock in swine. Ann Emerg Med. 1986;15(10):1131-7, http://dx.doi.org/10.1016/S0196-0644(86)80852-6.
http://dx.doi.org/10.1016/S0196-0644(86)...
) added 6% dextran-70 to sustain these improved hemodynamics, and this solution, HSD, attracted great interest from the military. Subsequent preclinical studies in different controlled hemorrhage models and animal species have shown similar benefits in outcomes with doses as low as 4 ml/kg (1212. Dubick MA, Wade CE. A review of the efficacy and safety of 7.5% NaCl/6% dextran 70 in experimental animals and in humans. J Trauma. 1994;36(3):323-30.). No potential resuscitation fluid has undergone as extensive a pre-clinical evaluation and safety schedule as HSD.

The initial interest in HS and HSD focused on their physical and chemical abilities to rapidly expand plasma volume (1313. Kramer GC, English TP, Gunther RA, Holcroft JW. Physiological mechanisms of fluid resuscitation with hyperosmotic/hyperoncotic solutions. Prog Clin Biol Res. 1989;299:311-20.). This volume expansion was greater in hypotensive subjects than in normotensive subjects (1212. Dubick MA, Wade CE. A review of the efficacy and safety of 7.5% NaCl/6% dextran 70 in experimental animals and in humans. J Trauma. 1994;36(3):323-30.,1414. Wade CE, Kramer GC, Grady JJ, Fabian TC, Younes RN. Efficacy of hypertonic 7.5% saline and 6% dextran-70 in treating trauma: a meta-analysis of controlled clinical studies. Surgery. 1997;122(3):609-16, http://dx.doi.org/10.1016/S0039-6060(97)90135-5.
http://dx.doi.org/10.1016/S0039-6060(97)...
), and these effects were more pronounced when compared with current standard of care fluids, such as normal saline (NS) or lactated Ringer's (LR) (1515. Walsh JC, Kramer GC. Resuscitation of hypovolemic sheep with hypertonic saline/Dextran: the role of Dextran. Circ Shock. 1991;34(3):336-43.). In addition, these products did not require refrigeration and were stable for more than 2 yr at a wide range of temperatures.

Other studies have found that HS and HSD reduce peripheral vascular resistance and improve microcirculatory flow, leading to improved tissue perfusion and oxygen delivery (1616. Steinbauer M, Harris AG, Messmer K. Effects of dextran on microvascular ischemia-reperfusion injury in striated muscle. Am J Physiol. 1997;272(4 Pt 2):H1710-6.). Further studies in experimental animals concluded that HSD should be the first resuscitation fluid administered (1717. Varicoda EY, Poli de Figueiredo LF, Cruz RJ, Jr., Silva LE, Rocha e Silva M. Blood loss after fluid resuscitation with isotonic or hypertonic saline for the initial treatment of uncontrolled hemorrhage induced by spleen rupture. J Trauma. 2003;55(1):112-7.) and that doses could be adjusted to sustain animals, even in uncontrolled hemorrhage models (1818. Bruttig SP, O'Benar JD, Wade CE, Dubick MA. Benefit of slow infusion of hypertonic saline/dextran in swine with uncontrolled aortotomy hemorrhage. Shock. 2005;24(1):92-6, http://dx.doi.org/10.1097/01.shk.0000168872.37660.d2.
http://dx.doi.org/10.1097/01.shk.0000168...

19. Riddez L, Drobin D, Sjostrand F, Svensen C, Hahn RG. Lower dose of hypertonic saline dextran reduces the risk of lethal rebleeding in uncontrolled hemorrhage. Shock. 2002;17(5):377-82, http://dx.doi.org/10.1097/00024382-200205000-00006.
http://dx.doi.org/10.1097/00024382-20020...
-2020. Sallum EA, Sinozaki S, Calil AM, Coimbra R, Silva MR, de Figueiredo LF, et al. Blood loss and transcapillary refill in uncontrolled treated hemorrhage in dogs. Clinics. 2010;65(1):67-78, http://dx.doi.org/10.1590/S1807-59322010000100011.
http://dx.doi.org/10.1590/S1807-59322010...
).

Most recently, attention has focused on other pharmacologic actions of hypertonic fluids, particularly their effects on immune function. In part, this work arose from studies on the improved microcirculation associated with hypertonic fluids (1616. Steinbauer M, Harris AG, Messmer K. Effects of dextran on microvascular ischemia-reperfusion injury in striated muscle. Am J Physiol. 1997;272(4 Pt 2):H1710-6.,2121. Mazzoni MC, Borgstrom P, Arfors KE, Intaglietta M. The efficacy of iso- and hyperosmotic fluids as volume expanders in fixed-volume and uncontrolled hemorrhage. Ann Emerg Med. 1990;19(4):350-8, http://dx.doi.org/10.1016/S0196-0644(05)82332-7.
http://dx.doi.org/10.1016/S0196-0644(05)...
-2222. Rocha-e-Silva M, Poli de Figueiredo LF. Small volume hypertonic resuscitation of circulatory shock. Clinics. 2005;60(2):159-72.) because these fluids reduce neutrophil rolling and sticking to endothelial cells in blood vessels (2323. Junger WG, Coimbra R, Liu FC, Herdon-Remelius C, Junger W, Junger H, et al. Hypertonic saline resuscitation: a tool to modulate immune function in trauma patients? Shock. 1997;8(4):235-41, http://dx.doi.org/10.1097/00024382-199710000-00001.
http://dx.doi.org/10.1097/00024382-19971...
-2424. Rizoli SB, Kapus A, Fan J, Li YH, Marshall JC, Rotstein OD. Immunomodulatory effects of hypertonic resuscitation on the development of lung inflammation following hemorrhagic shock. J Immunol. 1998;161(11):6288-96.). Taken together, the body of literature suggests that HS, if provided early, could inhibit the immune suppression that is associated with hemorrhagic shock, and based on several in vitro studies, may have direct protective effects on immune cells (2323. Junger WG, Coimbra R, Liu FC, Herdon-Remelius C, Junger W, Junger H, et al. Hypertonic saline resuscitation: a tool to modulate immune function in trauma patients? Shock. 1997;8(4):235-41, http://dx.doi.org/10.1097/00024382-199710000-00001.
http://dx.doi.org/10.1097/00024382-19971...
). Overall, these data on immune function further support that initial, early HS resuscitation would be of greater benefit than infusion after the administration of conventional fluids and that the modulation of immune function by HS may reduce secondary medical complications (2525. Rizoli SB, Rhind SG, Shek PN, Inaba K, Filips D, Tien H, et al. The immunomodulatory effects of hypertonic saline resuscitation in patients sustaining traumatic hemorrhagic shock: a randomized, controlled, double-blinded trial. Ann Surg. 2006;243(1):47-57, http://dx.doi.org/10.1097/01.sla.0000193608.93127.b1.
http://dx.doi.org/10.1097/01.sla.0000193...

26. Bulger EM, Cuschieri J, Warner K, Maier RV. Hypertonic resuscitation modulates the inflammatory response in patients with traumatic hemorrhagic shock. Ann Surg. 2007;245(4):635-41, http://dx.doi.org/10.1097/01.sla.0000251367.44890.ae.
http://dx.doi.org/10.1097/01.sla.0000251...

27. Rhind SG, Crnko NT, Baker AJ, Morrison LJ, Shek PN, Scarpelini S, et al. Prehospital resuscitation with hypertonic saline-dextran modulates inflammatory, coagulation and endothelial activation marker profiles in severe traumatic brain injured patients. J Neuroinflammation. 2010;7:5, http://dx.doi.org/10.1186/1742-2094-7-5.
http://dx.doi.org/10.1186/1742-2094-7-5...
-2828. Junger WG, Rhind SG, Rizoli SB, Cuschieri J, Shiu MY, Baker AJ, et al. Resuscitation of Traumatic Hemorrhagic Shock Patients With Hypertonic Saline-Without Dextran-Inhibits Neutrophil and Endothelial Cell Activation. Shock. 2012;38(4):341-50, http://dx.doi.org/10.1097/SHK.0b013e3182635aca.
http://dx.doi.org/10.1097/SHK.0b013e3182...
).

Clinical studies

A series of clinical studies were conducted in trauma patients in the late 1980s and early 1990s. In general, the trials were designed so subjects received a 250 ml bolus of HSD or standard of care crystalloid, followed by as much crystalloid as deemed medically appropriate. In most of the available studies, hypertonic solutions were administered within 2 hr following injury. To summarize, in 9 prospective trials with more than 900 patients who were treated with HSD, a mean survival benefit of 3.6% was observed. While 1 study reported improved survival at 24 hr (2929. Younes RN, Aun F, Accioly CQ, Casale LP, Szajnbok I, Birolini D. Hypertonic solutions in the treatment of hypovolemic shock: a prospective, randomized study in patients admitted to the emergency room. Surgery. 1992;111(4):380-5.), the others were inconclusive. In general, prehospital studies, rather than emergency department studies, suggested a greater benefit if the hypertonic fluids were the first resuscitation fluid used before the patient went into profound shock. Numerous retrospective reviews concluded that HSD had a favorable effect on survival, but statistical significance could not be demonstrated. Interestingly, HSD showed significance for efficacy in subpopulations of more severely injured patients (e.g., patients with head injuries (TBI) and patients requiring blood transfusions or surgery) (1414. Wade CE, Kramer GC, Grady JJ, Fabian TC, Younes RN. Efficacy of hypertonic 7.5% saline and 6% dextran-70 in treating trauma: a meta-analysis of controlled clinical studies. Surgery. 1997;122(3):609-16, http://dx.doi.org/10.1016/S0039-6060(97)90135-5.
http://dx.doi.org/10.1016/S0039-6060(97)...
,3030. Vassar MJ, Perry CA, Holcroft JW. Analysis of potential risks associated with 7.5% sodium chloride resuscitation of traumatic shock. Arch Surg. 1990;125(10):1309-15, http://dx.doi.org/10.1001/archsurg.1990.01410220093013.
http://dx.doi.org/10.1001/archsurg.1990....

31. Mattox KL, Maningas PA, Moore EE, Mateer JR, Marx JA, Aprahamian C, et al. Prehospital hypertonic saline/dextran infusion for post-traumatic hypotension. The U.S.A. Multicenter Trial. Ann Surg. 1991;213(5):482-91.

32. Wade CE, Dubick MA, Grady JJ. Optimal dose of hypertonic saline/dextran in hemorrhaged swine. J Trauma. 2003;55(3):413-6.

33. Bulger EM, Jurkovich GJ, Nathens AB, Copass MK, Hanson S, Cooper C, et al. Hypertonic resuscitation of hypovolemic shock after blunt trauma: a randomized controlled trial. Arch Surg. 2008;143(2):139-48; discussion 49, http://dx.doi.org/10.1001/archsurg.2007.41.
http://dx.doi.org/10.1001/archsurg.2007....
-3434. Baker AJ, Rhind SG, Morrison LJ, Black S, Crnko NT, Shek PN, et al. Resuscitation with Hypertonic Saline-Dextran Reduces Serum Biomarker Levels and Correlates with Outcome in Severe Traumatic Brain Injury Patients. Journal of Neurotrauma. 2009;26(8):1227-40, http://dx.doi.org/10.1089/neu.2008.0868.
http://dx.doi.org/10.1089/neu.2008.0868...
). In addition, in a trial by Vassar et al, (3535. Vassar MJ, Fischer RP, O'Brien PE, Bachulis BL, Chambers JA, Hoyt DB, et al. A multicenter trial for resuscitation of injured patients with 7.5% sodium chloride. The effect of added dextran 70. The Multicenter Group for the Study of Hypertonic Saline in Trauma Patients. Arch Surg. 1993;128(9):1003-11;discussion 11-3, http://dx.doi.org/10.1001/archsurg.1993.01420210067009.
http://dx.doi.org/10.1001/archsurg.1993....
), no differences were observed between patients who received HS vs. patients who received HSD, so the authors concluded that in the civilian population, with relatively short evacuation times, HS was sufficient. Importantly, all of these clinical trials confirmed that the use of HSD in trauma patients was safe (3636. Dubick MA, Bruttig SP, Wade CE. Issues of concern regarding the use of hypertonic/hyperoncotic fluid resuscitation of hemorrhagic hypotension. Shock. 2006;25(4):321-8.).

As mentioned above, an early clinical study indicated that in patients with severe TBI, those patients who received HSD were twice as likely to survive to hospital discharge compared with those patients who received standard crystalloid (3737. Vassar MJ, Perry CA, Gannaway WL, Holcroft JW. 7.5% sodium chloride/dextran for resuscitation of trauma patients undergoing helicopter transport. Arch Surg. 1991;126(9):1065-72, http://dx.doi.org/10.1001/archsurg.1991.01410330019002.
http://dx.doi.org/10.1001/archsurg.1991....
). General clinical interest in the potential benefits of hypertonic fluids for the treatment of TBI has centered on these fluids' ability to support blood pressure and improve cerebral perfusion pressure without raising intracranial pressure and causing cerebral edema, which are common side effects with standard crystalloids. In addition, studies have suggested that HS is a viable alternative to mannitol for treating refractory intracranial hypertension in TBI patients (3838. Banks CJ, Furyk JS. Review article: hypertonic saline use in the emergency department. Emerg Med Australas. 2008;20(4):294-305, http://dx.doi.org/10.1111/j.1742-6723.2008.01086.x.
http://dx.doi.org/10.1111/j.1742-6723.20...

39. Himmelseher S. Hypertonic saline solutions for treatment of intracranial hypertension. Curr Opin Anaesthesiol. 2007;20(5):414-26, http://dx.doi.org/10.1097/ACO.0b013e3282eff9ea.
http://dx.doi.org/10.1097/ACO.0b013e3282...
-4040. Roquilly A, Mahe PJ, Latte DD, Loutrel O, Champin P, Di Falco C, et al. Continuous controlled-infusion of hypertonic saline solution in traumatic brain-injured patients: a 9-year retrospective study. Crit Care. 2011;15(5):R260, http://dx.doi.org/10.1186/cc10522.
http://dx.doi.org/10.1186/cc10522...
). However, in a clinical study of comatose TBI patients who were treated prehospital with a 250 ml bolus of HS vs. LR followed by additional standard crystalloid infusion, no significant differences were noted between groups to hospital discharge or in neurological function at 6 mo (4141. Cooper DJ, Myles PS, McDermott FT, Murray LJ, Laidlaw J, Cooper G, et al. Prehospital hypertonic saline resuscitation of patients with hypotension and severe traumatic brain injury: a randomized controlled trial. JAMA. 2004;291(11):1350-7, http://dx.doi.org/10.1001/jama.291.11.1350.
http://dx.doi.org/10.1001/jama.291.11.13...
). However, in a retrospective cohort analysis of the effects of HSD in TBI patients with hypotension, Wade et al. (4242. Wade CE, Grady JJ, Kramer GC, Younes RN, Gehlsen K, Holcroft JW. Individual patient cohort analysis of the efficacy of hypertonic saline/dextran in patients with traumatic brain injury and hypotension. J Trauma. 1997;42(5 Suppl):S61-5.) concluded that such patients who received HSD were twice as likely to survive as patients who received standard crystalloid resuscitation. In addition, Baker et al. (3434. Baker AJ, Rhind SG, Morrison LJ, Black S, Crnko NT, Shek PN, et al. Resuscitation with Hypertonic Saline-Dextran Reduces Serum Biomarker Levels and Correlates with Outcome in Severe Traumatic Brain Injury Patients. Journal of Neurotrauma. 2009;26(8):1227-40, http://dx.doi.org/10.1089/neu.2008.0868.
http://dx.doi.org/10.1089/neu.2008.0868...
) reported that HSD reduced several biomarkers of brain injury in TBI patients, suggesting that HSD could lessen brain damage.

The resuscitation outcomes consortium (ROC) trials

Based on the continuing controversy over hypertonic fluids and the inconclusive results of previous clinical studies, the ROC trials, which consisted of 2 separate randomized, double-blind control, multicenter protocols, were initiated for the study of 2 subpopulations of trauma patients: patients with hypovolemic shock and patients with severe TBI (4343. Brasel KJ, Bulger E, Cook AJ, Morrison LJ, Newgard CD, Tisherman SA, et al. Hypertonic resuscitation: design and implementation of a prehospital intervention trial. J Am Coll Surg. 2008;206(2):220-32, http://dx.doi.org/10.1016/j.jamcollsurg.2007.07.020.
http://dx.doi.org/10.1016/j.jamcollsurg....
). Each trial had 3 arms, and the patients were randomized within 4 hr of injury for treatment with a 250 ml bolus of HS, HSD or normal saline (NS), followed by additional crystalloid as determined by medical need. However, patients were excluded if they received > 2000 ml of any fluid prior to receiving the test product. The feasibility of performing these studies in TBI patients was confirmed (4444. Morrison LJ, Baker AJ, Rhind SG, Kiss A, MacDonald RD, Schwartz B, et al. The Toronto prehospital hypertonic resuscitation—head injury and multiorgan dysfunction trial: feasibility study of a randomized controlled trial. J Crit Care. 2011;26(4):363-72.-4545. Morrison LJ, Rizoli SB, Schwartz B, Rhind SG, Simitciu M, Perreira T, et al. The Toronto prehospital hypertonic resuscitation-head injury and multi organ dysfunction trial (TOPHR HIT)—methods and data collection tools. Trials. 2009;10:105, http://dx.doi.org/10.1186/1745-6215-10-105.
http://dx.doi.org/10.1186/1745-6215-10-1...
). The primary endpoints were 28 d survival in the hypovolemic shock patients and Extended Glasgow Outcome Scale (GOSE) score at 6 mo in the TBI study (4343. Brasel KJ, Bulger E, Cook AJ, Morrison LJ, Newgard CD, Tisherman SA, et al. Hypertonic resuscitation: design and implementation of a prehospital intervention trial. J Am Coll Surg. 2008;206(2):220-32, http://dx.doi.org/10.1016/j.jamcollsurg.2007.07.020.
http://dx.doi.org/10.1016/j.jamcollsurg....
). Secondary outcomes included incidence of acute respiratory distress syndrome (ARDS), multi-organ failure, infection, number of ventilator days and physiologic and functional outcomes in the first 28 d. In the hypovolemic shock study, 895 patients were randomized, and 220, 256 and 375 patients were included for analysis in the HSD, HS and NS groups, respectively (4646. Bulger EM, May S, Kerby JD, Emerson S, Stiell IG, Schreiber MA, et al. Out-of-hospital hypertonic resuscitation after traumatic hypovolemic shock: a randomized, placebo controlled trial. Ann Surg. 2011;253(3):431-41, http://dx.doi.org/10.1097/SLA.0b013e3181fcdb22.
http://dx.doi.org/10.1097/SLA.0b013e3181...
). The study was stopped early after obtaining only 23% of the proposed sample size, based on the Data Safety Monitoring Board for futility, due to the unlikelihood of obtaining a statistically significant improvement in 28-d survival in the hypertonic groups over NS and possible safety concerns. No differences in 28-d survival were noted among the groups. There were also no differences among the groups in 6 hr survival time or ARDS-free 28-d survival time. Of concern was a higher mortality rate in the 2 HS groups (HSD 10% and HS 12.2%), compared with NS (4.8%), in which patients did not receive a blood transfusion in the first 24 hr.

The TBI trial was designed to enroll 2122 patients, but it was also stopped for futility in showing benefit after randomization of 1331 patients and analysis of 1087 patients (4747. Bulger EM, May S, Brasel KJ, Schreiber M, Kerby JD, Tisherman SA, et al. Out-of-hospital hypertonic resuscitation following severe traumatic brain injury: a randomized controlled trial. JAMA. 2010;304(13):1455-64, http://dx.doi.org/10.1001/jama.2010.1405.
http://dx.doi.org/10.1001/jama.2010.1405...
). These patients had TBI and were not in hypovolemic shock. In this patient population, no significant differences among the groups were noted for 28-d survival or 6 mo neurological outcomes, as determined by distribution of GOSE category or Disability Rating Score.

Concluding remarks

Despite a huge body of literature showing that HSD and HS improve hemodynamic and metabolic responses, modulate immune function and reduce brain edema in a number of experimental injury models and several small and large animal species, translating these results into improved survival in clinical trials in hemorrhagic shock and TBI has been difficult. Considering the heterogeneity of injury, injury severity and age of the trauma patients, it is not surprising that all the clinical trials to date have had several limitations, such as being underpowered to show improved survival or not having been focused on the trauma population most likely to benefit. A clear difference between the preclinical studies and the clinical trials is the dose. In the majority of animal studies, HS or HSD was administered primarily as a single 4 ml/kg bolus dose, whereas in the clinical trials, a 250 ml bolus (approximately 3.6 ml/kg in a 70 kg person) was followed by additional crystalloid. It was shown previously that the benefit (e.g., volume sparing) of hypertonic infusion was lost if the infusion rate was too slow or if it was followed immediately by standard crystalloid (4848. Elgjo GI, Traber DL, Hawkins HK, Kramer GC. Burn resuscitation with two doses of 4 mL/kg hypertonic saline dextran provides sustained fluid sparing: a 48-hour prospective study in conscious sheep. J Trauma. 2000;49(2):251-63; discussion 63-5.). In addition, none of the clinical trials reported the body weights of the patients, so it is unknown whether the per kg body weight dose was similar to the doses administered in the pre-clinical animal studies. Previous data in swine hemorrhage models indicated that the survival benefit of hypertonic fluids could be lost at doses ≤2 ml/kg (1111. Maningas PA, DeGuzman LR, Tillman FJ, Hinson CS, Priegnitz KJ, Volk KA, et al. Small-volume infusion of 7.5% NaCl in 6% Dextran 70 for the treatment of severe hemorrhagic shock in swine. Ann Emerg Med. 1986;15(10):1131-7, http://dx.doi.org/10.1016/S0196-0644(86)80852-6.
http://dx.doi.org/10.1016/S0196-0644(86)...
). Because HS and HSD are efficient volume expanders and because they expand plasma volume better in hypovolemic than normovolemic conditions, concerns were raised regarding clinical trials in which the additional fluids in severely injured hypovolemic patients could worsen the hemodilution of blood clotting factors and lead to more bleeding. However, none of the clinical trials has demonstrated greater bleeding in any patient treated with hypertonic fluids. In fact, it is the bleeding patient who seems to benefit most from receiving HS or HSD as the initial resuscitation fluid.

The observation in the trial by Bulger et al. (4646. Bulger EM, May S, Kerby JD, Emerson S, Stiell IG, Schreiber MA, et al. Out-of-hospital hypertonic resuscitation after traumatic hypovolemic shock: a randomized, placebo controlled trial. Ann Surg. 2011;253(3):431-41, http://dx.doi.org/10.1097/SLA.0b013e3181fcdb22.
http://dx.doi.org/10.1097/SLA.0b013e3181...
) of greater mortality after hypertonic fluid infusion in a subgroup of trauma patients who did not receive blood transfusions in the first 24 hr was most disturbing and was never predicted by the large body of preclinical data nor by any of the previous trauma trials. It is possible that based on volume expansion properties and the additional crystalloid fluid noted, certain trauma patients with pre-existing comorbidities could have developed heart failure due to fluid overload. Another very plausible explanation was offered by Holcroft (4949. Holcroft JW. The hypertonic saline trial: a possible downside to the gold standard of double blinding. Ann Surg. 2011;253(3):442-3, http://dx.doi.org/10.1097/SLA.0b013e31820d32d0.
http://dx.doi.org/10.1097/SLA.0b013e3182...
) with regard to the well-described properties of HS or HSD of dilating resistance vessels in the skin, resulting in intense flushing. Holcroft postulated that patients with occult abdominal bleeding who received HS or HSD prehospital would have presented to the emergency department with maintained blood pressure and the appearance of well-perfused skin, giving the care providers the impression that the patient did not need hemorrhage control or blood, thus resulting in the higher mortality observed. This argument reinforces the suggestion that when hypertonic fluids are infused as a bolus, the use of blood pressure to monitor the patient's status is meaningless.

Today, some civilian centers have used FDA-approved 3% or 5% HS as the initial treatment for patients with a head injury to reduce intracranial pressures and improve cerebral blood flow, with the suggestion that these solutions can be as beneficial as the 7.5% product, which is not FDA-approved (5050. Coimbra R. 3% and 5% hypertonic saline. J Trauma. 2011;70(5 Suppl):S25-6.-5151. DuBose JJ, Kobayashi L, Lozornio A, Teixeira P, Inaba K, Lam L, et al. Clinical experience using 5% hypertonic saline as a safe alternative fluid for use in trauma. J Trauma. 2010;68(5):1172-7.). Although the argument continues over the validity of using the 28-d survival endpoint to evaluate resuscitation fluid, it is clear that hypertonic fluids improve secondary endpoints in both hypovolemic trauma patients and in patients with TBI. In addition, none of the standard of care solutions used today have been required to demonstrate improvement in the primary outcomes of the hypertonic studies. If HS finds some utility in the treatment of civilian trauma, small-volume HSD remains the fluid of choice for the military, in which its longer duration of action is beneficial in the face of longer evacuation times in asymmetric battlefields. Over the past few years, the concept of fluid resuscitation has changed to the paradigm of damage control resuscitation (DCR), with more judicious use of early blood products and low-volume asanguinous fluids to maintain blood-clotting factors and to improve the metabolic consequences of and immune dysfunction caused by hemorrhagic shock. Current efforts to move DCR practices into the prehospital arena have begun with the development of modern dry plasma. Discussions have already begun with regard to pursuing a hypertonic plasma, which may contain 3% NaCl. Thus, as small-volume fluids, HS and HSD would be compatible with the concept of permissive hypotension in the prehospital setting and would fit in the overall scheme of DCR.

ACKNOWLEDGEMENTS

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense. Funded in part by the US Army Medical Research Materiel Command and by a Defense Medical Research and Development Program grant.

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Publication Dates

  • Publication in this collection
    June 2013

History

  • Received
    24 Jan 2013
  • Reviewed
    19 Feb 2013
  • Accepted
    19 Feb 2013
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