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Triage, Stabilization, Fluid Therapy

Triage, Initial Stabilization and Fluid Therapy
Adam R. Lancaster, DVM, DACVECC

Part 1: Triage

The word triage is derived from the French word “trier”, a word related to the process of sorting. The original use of triage was for mass casualty situations (including war) and would identify patients as immediate, urgent or non-urgent. Triage, in the medical sense, is the process of classifying (or sorting) patients into categories based on their level of illness. Importantly, triage is a dynamic system, and patients may change levels based on changes in their status.

There are numerous triage systems that have been developed in human medicine. These include the Emergency and Severity Index, Australian Triage Scale, Canadian Triage and Acuity Scale, and Manchester Triage System. These triage systems are generally based on vital signs such as heart rate or respiratory rate and may include up to five levels.

The first veterinary triage scoring system was published in the “Journal of Veterinary Emergency and Critical Care” in 1994. This scoring system, called the Animal Trauma Triage (ATT) scoring system was devised mainly to help stratify patients based on severity of injury for research purposes. However, it may have some usefulness in identifying patients in a clinical setting who may require immediate intervention. The ATT scoring system looked at six categories including perfusion, cardiac, respiratory, eye/muscle/integument, skeletal and neurological and assigned a value from 0 (no injury) to 3 (severe injury) based on predetermined criteria. The animals therefore could have an overall score of 0-18. This study found that animals with higher ATT scores had a decreased risk of survival. In fact, for each one point increase in ATT there was a 2.3 times lower chance of surviving the trauma. As with any scoring system, application of this system to an individual patient to predict survival or to influence decisions regarding euthanasia should be done very cautiously.

Patients should be triaged as soon as possible after arriving to the clinic for an emergency. The initial evaluation includes the conduction of a primary survey. This primary survey is a brief examination of the animal focused on assessing vital life functions and the degree of the animal’s stability. The primary survey can be performed using the ABCDE approach. The A is for airway and arterial bleeding. Any arterial bleeding should be rapidly identified, and measures taken to control arterial bleeding should be performed very quickly. Likewise, assessment of a patent airway should be made quickly, and animals that do not have an airway will need to be intubated or a tracheostomy may need to be performed. The B is for breathing and should assess not only IF the patient is breathing but also whether the patient is breathing normally or is showing signs of respiratory dysfunction. Oxygen supplementation may need to be provided if respiratory distress or dysfunction is found. The C stands for circulation and is an assessment of tissue perfusion. Patients with identified tissue perfusion problems should be assessed for fluid status and adequately fluid resuscitated if deficiencies are noted. D is for disability and is a measure of the patient’s mentation and ability to feel pain. Finally, the E stands for external assessment and is quick overview of any wounds or other external abnormalities.

Once the primary survey has been completed and initial treatments performed (such as intubation, fluid boluses, etc.) a secondary survey can be performed. This includes a more complete physical examination plus any ancillary diagnostics that may need to be performed. This may include emergency bloodwork (PCV/TS, lactate, electrolytes, blood glucose) or a focused assessment with sonography for trauma (FAST) exam.

Triage ClassificationDescription Example
First PriorityPatient Critical
Treatment must be initiated within seconds to minutes – Bring immediately to treatment room
Major bleeding, breathing problems, altered mentation, shock, history of toxin ingestion, etc.
Second PriorityPatient Urgent
Currently stable, but may become first priority patient, need to be reassessed, or have treatment initiated, within minutes to hours
History of major trauma, history of unsuccessful urination, repeated vomiting or diarrhea, etc.
Third PriorityPatient Stable
Pressing problem that is non-critical
Treatment initiated within hours
Fever, lacerations, vomiting, diarrhea, etc.
Fourth PriorityPatient Completely Stable
Needs evaluation, but not urgently
Skin/coat/ear/anal gland complaints, etc.

Part 2: Stabilization

Once a patient has been identified as requiring treatment (first and second priority patients), initial stabilization and resuscitation may begin. This is often performed concurrently with the primary and secondary survey. Shock may be simply defined as inadequate oxygen delivery or tissue perfusion. Building off this simple definition then resuscitation may be defined as restoration of oxygen delivery and/or perfusion back to normal levels. One way to further classify shock is to categorize it based on the underlying cause. In this classification scheme shock, may be further categorized as hypovolemic, distributive, hypoxemic, metabolic and cardiogenic. Of these categories only cardiogenic typically does not benefit from IV fluid therapy. In all other cases of shock, fluid therapy should be instituted as soon as possible.

Basics of Fluid Therapy

The largest size of IV catheter that you can place in a patient should be used. An 18 or 20 gauge catheter can be placed on most animals (even cats) although patients with hypotension or hypovolemia may have small veins and a smaller catheter may need to be used until there is adequate filling of the veins to place a larger IV catheter.

There are a variety of fluids that may be used for initial resuscitation including isotonic crystalloids, hypertonic saline and colloids. In most instances, the type of fluid is of less importance than early identification and institution of IV fluid therapy. Isotonic crystalloids are made of water and electrolytes in various compositions. Some also contain a buffer to make them less acidic. Types of fluids that would be classified as isotonic crystalloids include 0.9% NaCl, lactated ringers (LRS), Normosol®-R (Norm-R) and plasmalyte. For most patients, the type of crystalloid administered does not really matter.

The administration of isotonic fluids leads to good volume expansion (~80% of the volume infused). Unfortunately this expansion is for a limited time. Isotonic fluids pass out of the extracellular fluid into the interstitium relatively quickly. Within 30 minutes volume expansion is down to 35% and within 4 hrs only 18% volume expansion remains. Additionally, large volumes of isotonic crystalloids may lead to interstitial edema. Shock doses of crystalloids are 90 mls/kg in the dog and 60 mls/kg in the cat. Importantly, the entire “shock” dose should not be administered at once. Rather a 20-30 ml/kg bolus should be administered in aliquots until the desired endpoints of resuscitation have been achieved or the total “shock” dose has been administered.

Hypertonic saline (HTS) is a fluid that contains water, Na+ and Cl- similar to physiologic saline but in higher concentrations (either 7% or 23%). This makes the solution hypertonic to the plasma. Administration of a hypertonic fluid draws fluid from the intracellular space and therefore expands the extracellular space to a degree greater than the volume administered (~3.5x the volume infused). Similar to isotonic crystalloids, redistribution occurs rapidly. When 4 mls/kg of 7% HTS is administered over 5 minutes there is a 17% increase in IV volume which decreases to 12% at 30 minutes and 3% after 4 hrs. Due to its hypertonic nature, HTS also decreases intracranial pressure and therefore may be especially helpful in conditions such as traumatic brain injury. The dose of hypertonic saline is 4 mls/kg and this may be repeated once.

There are two major categories of colloids, natural and artificial. Natural colloids including albumin (both human albumin and canine albumin) and plasma. Artificial colloids include the hydroxyethyl starches (HES). Hydroxyethyl starches are categorized based on their molecular weight, molar substitution and C2:C6 ratio. Products with a higher molecular weight, increased substitutions and higher C2:C6 ratio have a longer half-life and therefore may have an increased risk of side effects. Currently there are two main products on the market, hetastarch and voluven/vetstarch. Of these, hetastarch has a higher molecular weight, increased substitutions and lower C2:C6 ratio when compared to voluven. As such, lower total daily doses are recommended. No benefit for colloids over crystalloids has ever been established for resuscitation of shock. Of note, hydroxyethyl starches have come under increased scrutiny the past few years due to the development of severe adverse effects in people, namely acute kidney injury (AKI). These products are no longer recommended for use in people and have been pulled off the market in some countries. Evidence for development of AKI in dogs and cats is lacking, however. Therefore, these products may still be used with caution in individual patients.

Fluid comparison:

FluidElectrolytesBufferIndications/usefulnessCautions
0.9% (physiologic) NaClNa+, Cl-NoUseful when other electrolytes not wanted (such as hyperkalemia)

 

May be used with blood products

 

Hypercalcemia

May worsen acidosis

 

Caution in hypernatremia and hyponatremia

LRSNa+, Cl-, K+, CalciumYes, lactateBasic resuscitation

Hypocalcemia

Won’t worsen acidosis

 

Do not use with blood products

Caution in patients with lymphoma

May cause elevations in blood lactate

PlasmalyteNa+, Cl-, K+, Mg+Yes, acetate and gluconateWon’t worsen acidosis

 

Do not use with blood products
Norm-RNa+, Cl-, K+, Mg+Yes, acetate and gluconateWon’t worsen acidosis

 

Do not use with blood products
Hypertonic 7% saline (HTS)Na+, Cl-NoExpands IV space 3.5x volume infused

Decreases intracranial pressure

Arteriolar vasodilation may further increase perfusion

Caution in patients with hyponatremia

Relatively contraindicated with hypernatremia

Maximum dose 8 mls/kg/day

Hetastarch (HES)Na+. Cl-Sodium hydroxide added for pH adjustmentProvides oncotic support

May be useful in hypoalbuminemia

Coagulation disturbances

Acute kidney injury

VetstarchNa+, Cl-Sodium hydroxide added for pH adjustmentMay be able to give larger volumes when compared to HESCoagulation disturbances

Acute kidney injury

While fluid therapy is the main component for many animals in need of stabilization, other treatments, beyond the scope of this article, may need to be performed. Hemorrhage should be controlled with bandages or tourniquets as appropriate. Oxygen supplementation may need to be administered. Hypoglycemia or other electrolyte disorders need to be corrected if present. And finally, pain medications should be administered to patients with identified pain or who have been diagnosed with a condition that is known to be painful.