Fluid Therapy

Fluid therapy

it is often essential for various medical conditions in animals

The mammalian body is approximately

60% water across intracellular and extracellular spaces

When an electrolyte solution is administered

approximately 25-35% remains in the vascular space

2 types of intravenous fluids

crystalloids and colloids

Crystalloids

these are electrolytes dissolved in water and their categorized based on their differences in osmolality compared to that of blood

Hypotonic crystalloids

they have an osmolality less than that of blood

Hypotonic crystalloid solutions

• 5% dextrose in water

• 0.45 NaCl (1/2 the strength of normal saline)

• Normosol M

• Plasmalyte 56

Some uses of hypotonic crystalloid solutions

used to replace free water loss, treat hypernatremia, and for maintenance fluid therapy

Isotonic crystalloids

they have an osmolality equal to blood and are primarily distributed to the extracellular space

Isotonic crystalloids use

for rehydration and shock resuscitation

Isotonic crystalloid solutions

• Normal saline (.9% sodium chloride in water)

• Lactated Ringers

• Balanced electrolyte solutions such as Normosol-R

Hypertonic crystalloids

they have an osmolality greater than that of blood

Hypertonic crystalloids use

used in traumatic injuries to move fluid out of the interstitial spaces of the brain, causing a decrease in intracranial pressure

Colloids

larger molecules suspended in isotonic crystalloid solution, remain in the vascular space, and are ideal for use in resuscitation

If the blood pH is less than 7.1

sodium bicarbonate may be used to help restore the acid base balance

For patients with hypoglycemia

dextrose can be added to balanced electrolytes for a final concentration of 2.5 to 10%

Why should subcutaneous administration of dextrose solutions of more than 2.5% be avoided?

because it can cause tissue deterioration/sloughing

The 3 fluid therapy phases

resuscitation, replacement, and maintenance

Resuscitation phase purpose

restores volume loss in hypovolemia and shock, and a fraction of the shock dose is given over a short period and then the patient is monitored for the response

Best intravenous fluids for the resuscitation phase

hypertonic crystalloids and colloids

What's the purpose of replacement fluid therapy?

used to correct dehydration, replace ongoing losses that may occur due to vomiting and diarrhea, and provide maintenance fluids

Mild dehydration

5%, there’s mild mucus membrane dryness

Moderate dehydration

7%, mild loss of skin turgor, dry mucus membranes, and possible mild tachycardia

Severe dehydration

10%, significant loss of skin turgor, dry mucus membranes, tachycardia, weak pulses, and sunken eyes

Fluid deficit calculation

body weight (in kg) x percent dehydrated + volume (L)

Signs of fluid overload

• panting

• coughing

• harsh lung sounds

• chemosis

Chemosis

swelling of conjunctiva around the eyes

Maintenance phase

this happens once hydration is restored and there are no ongoing fluid losses, the patient can be provided with these fluids

Allometric scaling

best predicts fluid requirements in very small and large patients

Perform cross-matching and antibody screening

prior to implementing blood transfusions

Agglutination

cell clumping by antibodies reacting to components of surface antigens

Cross-matching

a diagnostic procedure that tests the compatibility of recipient and donor blood cells

Oncotic pressure

a portion of total osmotic pressure contributed by colloids

How to monitor a blood transfusion

by interpreting results of physical examination, PCV, blood lactate, and oxygen extraction ratio

Oxygen extraction ratio

the ration of oxygen consumption to oxygen delivery