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Abstract
Background Tactical Combat Casualty Care guidelines for hemorrhage recommend resuscitation to systolic blood pressure (SBP) of 85±5 mm Hg during prehospital care. Success depends on transport to definitive care within the ‘golden hour’. As future conflicts may demand longer prehospital/transport times, we sought to determine safety of prolonged permissive hypotension (PH).
Methods Adult male swine were randomized into three experimental groups. Non-shock (NS)/normotensive underwent anesthesia only. NS/PH was bled to SBP of 85±5 mm Hg for 6 hours of prolonged field care (PFC) with SBP maintained via crystalloid, then recovered. Experimental group underwent controlled hemorrhage to mean arterial pressure 30 mm Hg until decompensation (Decomp/PH), followed by 6 hours of PFC. Hemorrhaged animals were then resuscitated with whole blood and observed for 24 hours. Physiologic variables, blood, tissue samples, and neurologic scores were collected.
Results Survival of all groups was 100%. Fluid volumes to maintain targeted SBP in PFC were significantly higher in the hemorrhage group than sham groups. After 24 hours’ recovery, no significant differences were observed in neurologic scores or cerebrospinal fluid markers of brain injury. No significant changes in organ function related to treatment were observed during PFC through recovery, as assessed by serum chemistry and histological analysis.
Conclusions After 6 hours, a prolonged PH strategy showed no detrimental effect on survival or neurologic outcome despite the increased ischemic burden of hemorrhage. Significant fluid volume was required to maintain SBP—a potential logistic burden for prehospital care. Further work to define maximum allowable time of PH is needed.
Study type Translational animal model.
Level of evidence N/A.
- hypotension
- hemorrhagic shock
- prolonged field care
- full resuscitation
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Footnotes
Presented at Portions of this work were presented at the 14th Annual Academic Surgical Congress, February 7, 2019, Houston, TX.
Contributors CGM: study design and implementation, data acquisition and interpretation, article drafting and revisions. LEN: study implementation, data analysis and interpretation, article drafting and revisions. ENH: data interpretation and analysis, article revisions. GJR and LJS: study implementation, data acquisition and analysis, article revisions. SC: data interpretation, article revisions. JJG: study design and implementation, data acquisition and analysis, article revisions.
Funding This work was supported by the Assistant Secretary of Defense for Health Affairs, through the Fiscal Year 2016 Defense Medical Research and Development Program Prolonged Field Care Research Award–Intramural; LOG number: DM167139.
Disclaimer The views expressed in this article reflect the results of research conducted by the author and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, nor the US Government. In conducting research using animals, the investigators adhered to the laws of the USA and the regulations of the Department of Agriculture. The experiments reported herein were conducted in compliance with the Animal Welfare Act and in accordance with the principles set forth in the 'Guide for the Care and Use of Laboratory Animals', Institute of Laboratory Animals Resources, National Research Council, National Academy Press, 2011.
Competing interests SC, CGM, and LEN are civilian employees of the US Government. GJR and LJS are contract employees of the US Government. JJG and ENH are military service members and this work was prepared as part of their official duties. Title 17 USC §105 provides that ‘copyright protection under this title is not available for any work of the US Government.’ Title 17 USC §101 defines a US Government work as a work prepared by a military service member or employee of the US Government as part of that person’s official duties.
Patient consent for publication Not required.
Ethics approval The study protocol was reviewed and approved by the 711th HPW/RHD JBSA-Fort Sam Houston Institutional Animal Care and Use Committee (IACUC) in compliance with all applicable federal regulations governing the protection of animals in research. All procedures were performed in AAALAC International accredited facilities.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article.