HOW-TO SESSION: FIELD ANESTHESIA AND PAIN MANAGEMENT Historically, hemoglobin and hematocrit levels


have been utilized to determine when blood trans- fusions should be administered. However, these clinical parameters are not reliable transfusion trig- gers because they are unreliable indicators of blood loss severity. In acute blood loss, red blood cells and plasma are both lost; therefore hematocrit and hemoglobin do not change until transcapillary refill and other compensatory mechanisms occur. In ad- dition, treatment with intravenous fluids will dilute but not alter the total number of circulating red blood cells. Therefore, the hematocrit decreases even if the number of red blood cells remains un- changed. In species that have a large reservoir of red blood cells in the spleen (such as the horse), the hematocrit alters rapidly with splenic contraction and may initially increase even in patients with severe blood loss. Application of DCR strategy will also aid in deter-


mining the volume of fluid to administer in hemor- rhagic shock. The goal of DCR is permissive hypotension. A volume of fluid is administered that maintains the mean arterial blood pressure at 50 mm Hg or the systolic blood pressure at 80 mm Hg. Measuring blood pressure in the equine pa- tient to obtain the ideal pressure readings is diffi- cult. Many field or hospital practitioners will not have equipment to accurately measure blood pres- sure. If a practitioner rarely encounters a case of hemorrhagic shock, justifying the cost of the equip- ment may be challenging. Even when equipment is available, obtaining frequent, reliable blood pres- sure readings may be impossible and potentially dangerous to the veterinarian or techni- cian. Horses with blood loss may exhibit colic signs, ataxia, or change in mentation. Therefore, the blood pressure cuff may not be maintained in the correct position, and readings may be unreliable. Even if blood pressure readings are not obtained, other parameters may be utilized to determine if fluid resuscitation is adequate to maintain organ perfusion. DCR strategy advocates fluid therapy until the radial pulse can be palpated. In the equine patient, lack of peripheral pulses and cold extremities suggest hypoperfusion. Abnormalities in creatinine, blood urea nitrogen, and electrolytes are indicators of potential renal dysfunction. When these parameters are altered from the reference range, renal damage from hypoperfusion should be considered and fluid therapy must be adjusted. Applying the DCR strategy of permissive hypoten- sion and administration of plasma and fresh, warm


blood to equine patients with acute hemorrhage may assist the veterinary practitioner in successful treat- ment of these cases. Limiting factors with this strategy are having the appropriate equipment to monitor blood pressure and having access to plasma or whole blood. However, physical examination and blood work parameters may compensate for lack of equipment. The DCR strategy needs further evaluation in equine medicine, but it may become the standard of care in resuscitation of equine pa- tients with hemorrhagic shock.


References


1. Marino PL. The ICU Book. 3rd edition. Philadelphia: Lippincott William & Wilkins; 2007:213–214.


2. Halcomb JB. Damage control resuscitation. J Trauma 2007;62:S36–S37.


3. Moore EE, Thomas G. Stated laparotomy for the hypother- mia, acidosis, and coagulopathy syndrome. AmJ Surg 1996; 172:405–410.


4. Brohi K, Cohen MI, Ganter MT, et al. Acute traumatic coagulopathy: initiated by hypoperfusion: modulated through the protein C pathway? Ann Surg 2007;245:812– 818.


5. Brohi K, Cohen MI, Ganter MT, et al. Acute coagulopathy of trauma: hypoperfusion induces anticoagulation and hyper- fibrinolysis. J Trauma 2008;64:1211–1217.


6. Hess JR, Brohi K, Dutton RP, et al. The coagulopathy of trauma: a review of mechanisms. J Trauma 2008;65:748– 754.


7. Gerhardt RT, Strandenes G, Cap AP, et al. Remote damage control resuscitation and the Solstrand Conference: defin- ing the need, the language , and a way forward. Transfusion 2013;53(Suppl 1):9S–16S.


8. Holcomb JB, Jenkins D, Rhee P, et al. Damage control re- suscitation: directly addressing the early coagulopathy of trauma. J Trauma 2007;62:307–310.


9. Shaz BH, Dente CJ, Nicholas J, et al. Increased number of coagulation products in relationship to red blood cell products transfused improves mortality in trauma patients. Trans- fusion 2010;50:493–500.


10. Hodgetts TJ, Mahoney PF, Kirkman E. Damage control resuscitation. J R Army Med Corps 2007;153:299–300.


11. Brohi K, Singh J, Heron M, et al. Acute traumatic coagu- lopathy. J Trauma 2003;54:1127–1130.


12. MacLeod JB, Lynn M, McKenney MG, et al. Early coagu- lopathy predicts mortality in trauma. J Trauma 2003;55: 39–44.


13. Maegele M, Lefering R, Yucel N, et al. Early coagulopathy in multiple injury: an analysis from the German Trauma Registry on 8724 patients. Injury 2007;38:298–304.


14. Borgman MA, Spinella PC, Perkins JG, et al. The ratio of blood products transfused affects mortality in patients receiv- ing massive transfusions at a combat support hospital. J Trauma 2007;63:805–813.


15. Kauvar DS, Holcomb JB, Norris GC, et al. Fresh whole blood transfusion: a controversial military practice. J Trauma 2006;61:181–184.


16. Repine TB, Perkins JG, Kauvar DS, et al. The use of fresh whole blood in massive transfusion. J Trauma 2006; 60(Suppl 6):S59–S69.


460 2013  Vol. 59  AAEP PROCEEDINGS


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