Anesthesia for Veterinary Technicians (Bryant) – Chapter 12: Fluid Therapy and Blood Products

Water weight
Roughly 60% of the patien’s body weight is water. Of the 60%, 66.6% is intracellular and 33.3% is extracellular.

Intracellular compartment
The space within a cell membrane. Contains 66.6% of the patient’s water weight (~40% of the patient’s body weight).

Extracellular compartment
Contains 33.3% of the patient’s water weight (~20% of the patient’s body weight. Composed of 25% intravascular water and 75% interstitial water.

Intravascular fluid
Contained within the arteries, veins, and capillaries.

Interstitial fluid
Found in the extravascular space between vasculature and cells.

Capillaries
The sites of fluid exchange between the intravascular and interstitial spaces. The size of the solute will determine how freely it can move across membranes,

Transcellular fluid
Includes cerebrospinal fluid, gastrointestinal fluid, lymph, bile, glandular and respiratory secretions, and synovial fluid. Not a transudate from plasma (should have a higher protein and cell count). Produced through specific cell actions. Not taken into account when assessing extracellular fluid volume.

Interstitium
Comprises less than 1% of free fluid in normal tissues. Uses kinetic motion to diffuse solutes.

Interstitial edema
Occurs when the lymphatic system is overwhelmed. A result of a decrease in oncotic pressure and an increase in hydrostatic pressure. Can occur due to shock, illness, or trauma. The capillary endothelial junctions can become separated when previously hypoxic tissues become reperfused. Albumin and fluids then leak out of the intravascular space. This leads to hypovolemia and can then lead to a decrease in oxygen transport and therefore a decrease in oxygen diffusion to cells.

Crystalloids
Any solutions that contain electrolyte and non-electrolyte solutes. Enter all body fluid compartments but have heir main effect on the interstitial and intracellular spaces. Can be further broken down into isotonic, hypertonic, or hypotonic preparations. Can also be classified as balanced or unbalanced solutions. Used to expand the plasma compartment, rapidly redistributes to the intracellular and interstitial spaces, so 2.5-3 times as much must be given (compared to colloid).

Isotonic fluids
Normosol-R and Plasmalyte 148, 0.9% NaCl, LRS. Have a similar sodium and chloride concentration and a higher potassium concentration to that of extracellular fluid, as well as a similar osmality. Rapidly equilibrate across the intravascular and interstitial spaces, therefore only 25% of the total volume administered stays within the intravascular space.

hypotonic solutions
0.45% NaCl, 5% Dextrose, Normosol-M, and Plasma-Lyte 56. Have a lower sodium and chloride content and a higher potassium content.

hypertonic solutions
3% NaCl, 7.2% NaCl, or 23.7% NaCl. Have a much higher sodium and chloride content than extracellular fluid.

Balanced crystalloids
Have a fluid composition that closely resembles extracellular fluid. LRS, Normosol-R, and Plasma-lyte 148.

Unbalanced crystalloids
Do not have a fluid composition that resembles the patient’s extracellular fluid. Normal/physiologic saline (0.9% NaCl)

Colloids
Contain large molecular weight substances that will stay within the plasma compartment. Predominantly used as expander of the intravascular space. Can be natural or synthetic.

Natural colloids
Plasma, whole blood, and concentrated albumin

Synthetic colloids
Dextrans, hetastarch, vetstarch, pentastarchm and HBOC fluids.

Albumin
The predominant plasma protein, pooled from human donors. Available in both a 4% and a 25% preparation. 25% is most widely used in clinical settings. Vascular expansion depends on the amount given, not on solution concentration. Main drawback is cost. Can cause fluid-overload.

Hetastarch
Hydroxyethyl starch. A plasma volume expander and will give equivalent plasma volume expansion to that of 4% albumin. Lower cost, can induce coagulopathies when the recommended dosages have been exceeded. In dogs, dosed at 10-40mL/kg/day IV to effect. In cats, the dose is 5mL/kg IV to effect, with a maximum dose I’d 40mL/kg/day. 20mL/kg/day maximum is usually sufficient. Take care to avoid fluid overload.

Dextran
Come as either 40 (a 10% solution) or 70 (a 6% solution). Made from a glucose polymer that is produced by bacteria grown on sucrose media. Produce an initial but temporary intravascular volume expansion. 50% of the expansion is lost within 3 hours, and 60% is lost within 6 hours. Dosed at 10-40mL/kg/day in dogs. In cats the dose is 5mL/kg IV over 5-10 minutes, and it can be reposed as needed, not to exceed 40mL/kg/day. Must be used cautiously. Can cause renal issues and have a dramatic affect on coagulopathies.

Fluid therapy
Meant to be supportive. Occurs in three phases: resuscitation, rehydration, or maintenance.

Maintenance fluid therapy
Administered at a rate of 40-60mL/kg/day. Designed to meet water and electrolyte requirements for patients not taking in enough fluids to meet their daily losses. Should be isotonic. Can use hypotonic solutions for renal patients, patients with CHF or hypernatremia, and patients on potassium bromide therapy.

Insensible losses
Occur through the skin, fecal waste, and the respiratory tract.

Sensible losses
Should occur as urine output

KCl
Potassium chloride. Long-term Therapy of any kind may cause a hypokalemia by evoking diuresis. Therefore, fluids should be supplemented with potassium chloride at 20mEq/L. Don’t bolus. Maximum rate of administration should not exceed 0.5mEq/kg/hr.

Isotonic saline
Used for rapid expansion of the extracellular fluid volume and is quickly redistributed through the extracellular space. Can be used as a replacement fluid but does not meet the patient’s daily electrolyte requirements when used as a maintenance fluid. Can have an acidifying effect because of its high chloride content and should be used cautiously in acidemic patients.

Replacement fluid therapy
Should be isotonic and contain a balanced electrolyte solution. They can be given as a bolus without causing electrolyte abnormalities. Only 25% of the total volume administered of crystalloids will stay in the intravascular spaceIf replacing blood loss with crystalloids alone, three times the volume of blood lost must be given. If replacing losses due to dehydration, the percent of dehydration should be calculated first.

<5% Dehydration
Not detectable

5-6% Dehydration
Subtle loss of skin elasticity

6-8% Dehydration
Definite delay in return of skin to normal position, slight prolongation of CRT, eyes possibly sunken in orbits, possibly dry mucous membranes

10-12% Dehydration
Tented skin stands in place, definite prolongation of CRT, eyes sunken in orbits, dry mucous membranes, possible signs of shock (tachycardia, cool extremities, rapid and weak pulses)

12-15% Dehydration
Definite signs of shock, death imminent

Hydration deficit (replacement requirement)
a. Body weight (lbs) x % dehydration as a decimal x 500* = deficit in mL
b. Body weight (kg) x % dehydration as a decimal = deficit in L
(*500mL = 1lb)

Resucutation fluid therapy
Determined by a patients clinical history and physical exam findings. Used to treat shock.

Signs of shock
Pale mucous membranes, a prolonged to absent CRT, tachycardia or severe bradycardia, cool extremities, weak to absent peripheral pulses, and hypotension.

Hypochloremia
Can result due to a lope of blood sample, vomiting of stomach contents, chronic respiratory acidosis, hyoeradrenocorticism, exercise, or sodium bicarbonate therapy. Can be caused by loop diuretics (furosemide).

Hyperchloremia
Can be the result of a life if blood sample, potassium bromide therapy (analyzer reads bromide as chloride), high chloride-containing fluids, diarrhea, or an overall gain of chloride due to potassium supplementation or salt poisoning. Renal chloride retention can occur as a result of renal failure, hypoadrenocortisism, diabetes mellitus, chronic respiratory alkalosis, or spiromolactone drug therapy.

Sodium
Na+. A major extracellular cation. Serum concentration tells the amount of Na+ compared to water in the extracellular fluid.

Hyponatremia
Sodium less than 140mEq/L in canines and 149mEq/L in felines. Will result when a patient is unable to excrete ingested water or when its urinary and insensible losses have a greater osmolality than that of the ingested or administered fluids. Neurological symptoms caused by cerebral edema. Acute onset can be treated with LRS, normal saline, or hypertonic fluid.

Hypernatremia
When sodium is greater than 155mEq/L in dogs and 162mEq/L in cats. Can result from an inadequate intake of water, an excessive amount of sodium ingested or administered, a pure water deficit, hypotonic loss, or hemorrhagic shock. In case of pure water deficit, treatment is 5% dextrose or 0.45% NaCl (hypotonic solutions). Neurological symptoms seen due to a rapid decrease in brain volume caused by rupture of cerebral vessels or focal hemorrhage.

Sodium imbalances
Clinical signs are the same for hyponatremia and hypernatremia. The severity of signs is related to the rapidity of onset, not to the magnitude of imbalances. Neurologic signs include weakness, behavioral changes, disorientation, ataxia, seizures, coma, and death. Other signs include anorexia, lethargy, and vomiting. Levels should not be changed any more rapidly than 10-12mEq/L in 24 hours (0.5mEq/L/hr) for fear of causing neurologic effects that are trying to be avoided.

Fluid calculation for sodium correction
Rate of Na+ Change = (Na+ of the fluid – Na+ of the patient) / (0.6 x BW in kg) + 1
For example:
Patient Na+ = 190mEq/L, wt. 20kg, LRS (Na+ 130mEq/L), fluid rate 100mL/hr
130 – 190 /(0.6 x 20) + 1 = 4.6mEq/L
Safe fluid choice and rate. A liter bag would last 10 hours and the Na+ can safely be adjusted by 5mEq.

Potassium
K+. A major intracellular cation.

Hypokalemia
Low potassium levels in the blood. Can be caused by an insulin administration or glucose-containing fluids, vomiting of stomach contents, or diarrhea. Urinary losses can occur in chronic renal failure patients, postobstructive diuresis, dialysis, hyperadrenocorticism, or primary hyperaldosteronism. Can be caused by certain medications (loop diuretics, penicillins, etc.). Signs vary from patient to patient and also depend on severity. Signs include PU/PD, a decrease in urine-concentrating capabilities, and even muscle weakness possibly leading to respiratory paralysis. Cardiovascular signs includedekayed ventricular repolarization, increased duration of action potential, and an increased automaticity. Supraventricular and ventricular dysrhythmias may be seen. A prolongation of the QT interval may be seen with levels less than 2.0mEq/L, and patients may become unresponsive to antiarrhythmic therapy. Can treat with KCl or potassium phosphates.

IV KCl supplementation guidelines
IV KCl supplementation guidelines

Hyperkalemia
Elevated levels of potassium in the blood. Uncommon in patients with normal renal function and urine output. Can be seen in diabetic patients due to insulin deficiency and hyperosmolality. Can be caused by decreased urine production from a urethral obstruction, ruptured bladder, or anuric/oliguric renal failure. Can be caused by hypoadrenocortisism. ECG will show shortening of the QT interval, tented T-waves, prolongation of the PR interval, widening of QRS complex, and disappearance of the P wave. These dysrhythmias can progress to atrial standstill and asystole. This is a life-threatening condition and needs to be treated immediately. A value greater than 6.5mEq/L needs immediate treatment. Can be treated with fluid therapy and other IV supplements.

Calcium gluconate 10% solution
Used to treat hyperkalemia. Administered at a dose of 2-10mL total to protect the heart against the effects of hyperkalemia on electrical conduction. Effects are short-lived, so further correction of potassium levels is required.

Sodium Bicarbonate
Treats hyperkalemia. Administered at a dose of 1-2mEq/kg IV to help move K+ ions into cells as H+ ions leave cells.

Insulin
Can be used to treat hyperkalemia by shifting potassium into the cells in exchange for sodium. The dose is 0.55-1.1mcg/kg IV for dogs and 1 unit per cat. There is a risk of hypoglycemia, so dextrose may be added to fluids.

Hypovolemic shock
Caused by a loss of intravascular volume. Can occur through dehydration, acute blood loss (hemorrhagic shock), or third-space loss of fluids. Treat with acute volume resuscitation and interstitial fluid replacement. Use crystalloids. After boluses the HR should be normal, systolic BP between 90-120mmHg, and CRT and MM should be improved. Can use hypertonic crystalloids (alone or mixed with colloids) to help with intravascular volume expansion.

Shock bolus
90mL/kg for a dog, 55mL/kg for a cat. Can be given in aliquots (1/4, 1/3, etc.) over 10-15 minutes and then the patient reassessed to avoid fluid overload.

Cardiogenic shock
Use a diuretic to help redistribute fluid from the lungs back into circulation, give inotropic support, and give antiarrhythmic agents as needed. Fluid therapy is typically contraindicated.

Obstructive shock
Causes are pericardial effusion causing cardiac tamponade, heartworm disease leading to caval syndrome, pulmonary thromboembolism (PTE), aortic thromboembolism, and cardiac neoplasia. Can also be caused by GDV due to decreased ventricular filling due to decreased venous return. Initiating a moderate or maintenance fluid therapy is appropriate while attempting to find and treat the underlying cause, except in GDV patients. In these patients, a shock bolus is indicated to help restore vascular volume.

Whole blood
Most commonly used of all blood products. Dosed at 13-22mL/kg or can be calculated using the desired PCV, the current PCV, and the donor PCV. Combined with an anticoagulant during the collection process. Must be used within 8 hours of collection. Used in anemic patients for oxygen-carrying capacity and in patients with coagulation factor deficiency. Don’t sue solely for coagulation factors as this can lead to iatrogenic polycythemia.

Calculating whole blood transfusion volume
[(Desired PCV – Actual patient PCV) / PCV of donor blood] x Recipient blood volume

Canine blood volume
88mL/kg

Feline blood volume
66mL/kg

pRBCs
Packed red blood cells. Whole blood that has been centrifuged into packed red blood cells and plasma. One unit from a canine would contain around 200mL/unit and have a hematocrit of 80%. Used for restoring and maintaining enough of an oxygen supply to meet tissue demands. Used to treat anemia due to blood loss, hemolysis, and bone marrow dysfunction. Decision to transfuse should be based in cardiovascular status, anticipated blood loss, ability of bone marrow to respond, chronicity of the anemia, and patient’s hemoglobin and hematocrit values.

FFP
Fresh frozen plasma. Collected and frozen within 8 hours to maintain clotting factors V and VIII. Contains electrolytes, albumin, globulins, coagulation factors, and other proteins. Used to treat coagulation deficiencies dipped to rodenticide intoxication, vitamin K-dependent coagulopathies, hemophilia B, von Willebrand’s disease, and hemophilia A. The dose is 6-10mL/kg IV over 4 hours.

Cryoprecioitate
Collected by thawing FFP at a temperature of 1-6C until a thick white precipitate is formed and centrifuges off. Contains factors VIII:C, XIII, von Willebrand’s factor, and fibrinogen. Dose is 1 unit per 10 kg. Decreased risk of volume overload in patients compared to FFP.

Human immunoglobulin
IGg. Used along with immunosuppressive therapy to treat immune-mediated hemolytic anemia. Prepared from pooled human plasma and therefore still runs a risk of reaction with repeated doses. The dose is 0.5-1gram/kg and is administered over 6-8 hours. Expensive.

DEA
Dog erythrocytes antigen, can be negative or positive. Over 13 canine blood types, but testing is available for only 6 of them for lab use.

Cat blood types
One blood group that contains types A, B, and AB. Type A will have antibodies against type B, and type B will have antibodies against type A. All cats should be typed prior to transfusion and should be cross-matched with donors in their type to avoid a transfusion reaction.

Mik antigen
Found in cats, negative inticated anti-Mik antibodies and could cause a hemolytic transfusion reaction.

Cross-matching
act of determining the compatibility of two blood specimens. Any patient that has received a transfusion in the past (greater than 4 days) needs this done before receiving a transfusion.

Transfusion
Thaw FFP. Inspect any unit for leaks or signs of contamination. No medications should be added to the transfusion line after it is being administered. Normal saline is the only fluid type compatible with a transfusion. All products should be administered through a 170 micron filter to remove clots or debris. An 18 micron filter can be used if using a syringe. Full volume must be administered within 4 hours to avoid contamination. Get a TPR, then administer products. The first 15 minutes should be given at half the rate, then recheck TPR. If still WNL, double the transfusion rate. TPR should then be checked every 30 minutes to monitor for a reaction.

Hemolytic train sfusion reaction
Clinical signs include hemoglobinuria, hemoglobinemia, icterus, and fever.

Febrile, nonhemolytic reaction
An increase in temperature by 1 degree.

Signs of transfusion reaction in dogs
Restlessness, salivation, incontinence, dyspnea, hypotension, collapse, convulsions, vomiting, and acute death (uncommon). Under anesthesia, these signs may not be apparent and trends should be monitored.

Signs of transfusion reaction in cats
Acute death (B cat given A blood). Extension of limbs and apnea. Increased respiratory and heart rate, shock, hypotension.

Treating transfusion reactions
Immediately stop transfusion, give crystalloid fluid with antipyretics. If not severe, give antihistamines and reduce the transfusion rate.

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