Review of Fluid Therapy in Acute Blood Loss
Michele L. Frazer, DVM, Diplomate ACVIM, ACVECC
Permissive hypotension and increased use of plasma and fresh, warm, whole blood instead of
crystalloid fluids may benefit equine patients with acute blood loss. Author’s address: Hagyard Equine
Medical Institute, 4250 Iron Works Pike, Lexington, KY 40511; e-mail: mfrazer@hagyard.com. © 2013
AAEP.
1. Introduction
Acute blood loss in the veterinary patient is an
emergency that many practitioners must manage in
the field or hospital setting. Diagnosis may be ob-
vious in cases of external blood loss, whereas inter-
nal blood loss may be more difficult to determine.
Acute hemorrhage can occur into the peritoneal,
pleural, or pericardial cavities; reproductive tract;
gastrointestinal tract; guttural pouches; joints; and
muscle tissue. In the equine patient, common
causes include trauma, rupture of a vessel in the
reproductive tract in pre- or post-foaling mares, frac-
tured ribs in foals, and inadequate hemostasis
during surgery. History, physical examination, ul-
trasound examination, and blood work aid in diag-
nosing acute hemorrhage as well as assessing the
severity and determining the cause.In hemorrhage, the number of circulating red
blood cells decreases, and the oxygen-carrying ca-
pacity of the blood is compromised. Initially, phys-
iological responses are able to compensate and
maintain blood pressure with transcapillary refill,
tachycardia, tachypnea, and systemic vasoconstric-
tion. When significant volume is lost, the body can no
longer compensate for the blood loss, and hemorrhagic
shock occurs. In this situation, adequate tissue
perfusion and oxygenation cannot be maintained. This eventually leads to organ dysfunction and car-
diovascular collapse. Patients with blood loss can be placed into one of
four categories as defined by the American College of
Surgeons.
1 Category 1 is loss of fi
15% of blood
volume. Transcapillary refill typically compen-
sates for this loss and maintains blood volume and
blood pressure. Category 2 is loss of 15% to 30% of
blood volume. Compensatory mechanisms such as
tachycardia and tachypnea occur, and sympathetic
vasoconstriction can typically maintain blood pres-
sure. Category 3 is loss of 30% to 40% of blood
volume. Compensatory mechanisms can no longer
maintain blood pressure, and decompensated hypo-
volemic shock occurs. Organ dysfunction, such as
acute renal failure, may occur from decreased tissue
oxygenation. Decreased urine production and hy-
potension occur. Category 4 is loss of \7
40% of
blood volume. Patients in this category require im-
mediate emergency treatment, and changes in blood
pressure and perfusion may not be reversible. The goal of treatment in patients with acute blood
loss is preventing hemorrhagic shock while also
preventing further loss of blood. Two areas of
controversy have occurred as to how best to accom-
plish this goal: fluid type and volume to be
administered.
458 2013 fiVol. 59fiAAEP PROCEEDINGS
HOW-TO SESSION: FIELD ANESTHESIA AND PAIN MANAGEMENT
NOTES