Fluid Therapy PDF

Emergency Medicine 14 CH A P TE R Patricia A. Schenck...

Emergency Medicine 14 CH A P TE R Patricia A. Schenck b. Occurs when there is a loss of water and FLUID THERAPY electrolytes in proportion to that in serum. I. Indications 2. Hypertonic dehydration A. Resuscitation from shock a. Elevated serum sodium concentration in the B. Correction of dehydration, hypokalemia, and presence of dehydration metabolic acidosis b. Occurs when there is water loss in excess C. Correction of other electrolyte disturbances of electrolytes in serum D. Parenteral nutrition 3. Hypotonic dehydration E. Treatment of anemia and coagulopathies a. Low serum sodium concentration in the II. Distribution of body water and electrolytes presence of dehydration A. Water b. Loss of isotonic fluid with intake and 1. Total body water is about 50% to 70% of body absorption of hypotonic fluids with a net weight in adults. Cats have slightly less body dilutional effect water; young animals and neonates have a C. Detection of dehydration higher percentage of body water 1. Dehydration is detectable when approximately 2. Intracellular water is about 40% of body weight 5% of body weight in water has been lost. An 3. Extracellular water is about 20% of body weight acute loss of more than 12% body weight in 4. Interstitial fluid is about 12% to 14% of body water is life-threatening weight, and intravascular fluid is about 6 to 2. History of decreased water intake or vomiting, 8% of body weight polyuria, diarrhea, excessive panting or B. Electrolytes salivation may suggest dehydration 1. Sodium and chloride are high in extracellular 3. Physical examination fluid and low in intracellular fluid a. Findings associated with dehydration in- 2. Potassium, magnesium, and phosphorus are low clude depression, acute loss of body weight, in extracellular fluid and high in intracellular sunken eyes, decreased skin turgor, dry fluid mucous membranes, tachycardia, dimin- III. Maintenance requirements ished capillary refill, and signs of shock A. Water intake should equal water loss in normal b. Skin turgor animals (1) When skin is lifted a short distance, it B. Insensible water loss is about 20 mL/kg/day should return quickly C. Sensible losses are 20 to 40 mL/kg/day in normal (2) As dehydration progresses, the time animals consuming food required for the skin to return to its D. A 0.45% sodium chloride solution makes a good normal position increases maintenance solution but does not contain (3) Dehydration is as much as 5% to 10% be- adequate potassium. Lactated Ringer’s and fore a loss of skin turgor can be detected 0.9% sodium chloride are not good maintenance D. Assessment of dehydration solutions because they contain too much sodium 1. Packed cell volume (PCV) and total plasma and chloride protein both increase with dehydration IV. Replacement needs (dehydration) 2. Urine specific gravity should increase in a A. Causes of dehydration dehydrated animal if the kidneys are healthy 1. Decreased water intake (decreased thirst and 3. Metabolic acidosis is common in dehydration appetite centers in sick animals, decreased E. Correction of dehydration food intake) 1. Volume of fluid  % dehydration weight (kg) 2. Increased water loss (e.g., polyuria, vomiting,  liters of fluid to be replaced diarrhea, salivation, burns) 2. Type of fluid is chosen based on electrolyte B. Type of dehydration status and acid-base status 1. Isotonic dehydration V. Types of fluids a. Normal serum sodium concentration in the A. Crystalloid solutions redistribute quickly. Best for presence of dehydration rehydration or replacement of fluid loss 201 202 SECTION II SMALL ANIMAL 1. Osmolality 2. Do not add sodium bicarbonate to fluids a. Hypotonic: Osmolality less than 300 mOsm/kg containing calcium (0.45% saline) 3. Do not use in patients with respiratory b. Hypertonic: Osmolality greater than dysfunction 300 mOsm/kg (5% dextrose in 0.9% saline) C. Magnesium c. Isotonic: Osmolality near 300 mOsm/kg 1. Indicated in patients with hypokalemia, dia- (lactated Ringer’s solution, Plasma-Lyte 148, betic ketoacidosis, and CHF Normosol-R, 0.9% saline) 2. Magnesium sulfate or magnesium chloride is 2. Replacement fluids are formulated for specific commonly used electrolyte deficits 3. Do not use in oliguric patients 3. Maintenance fluids may differ greatly from D. Dextrose: Indicated in hypoglycemia owing to serum, and becausee they usually contain sepsis, insulinoma, overdose of insulin, and liver glucose, their effect is hypotonic. The energy disease available from these fluids is insufficient to E. Calcium meet nutritional needs 1. Use either calcium gluconate or calcium chloride B. Colloid solutions contain large macromolecules 2. Do not use subcutaneously (SC) and attract water out of interstitial spaces. They 3. Indicated in hypocalcemic seizures or tetany. are ideal for replacing intravascular volume but Monitor heart rate; bradycardia is a sign of are not good for replacing extravascular fluid loss toxicity 1. Natural colloids are produced in the body and F. Phosphorus harvested for later use (blood transfusion 1. Only significant hypophosphatemia requires components) phosphorus supplementation (usually in 2. Synthetic colloids (such as hetastarch) are diabetic ketoacidosis) complex polysaccharide molecules 2. Avoid oversupplementation a. Used in conjunction with crystalloid fluid VII. General guidelines for fluid selection therapy. They are used primarily in patients A. Serum sodium level as a guide with hypoproteinemia and low oncotic 1. If sodium is normal (normonatremia), use pressure and in the treatment of shock fluids that are normal in sodium and b. Use with caution in those at risk for noncar- osmolality (lactated Ringer’s, Plasma-Lyte 148, diogenic pulmonary edema, in patients with Normosol-R, or 0.9% NaCl) congestive heart failure (CHF), and in those 2. If serum sodium is elevated (hypernatremia), with renal origin oliguria or anuria the fluids should contain more water than salt. C. Fluids to keep on hand Choose a hypotonic solution (5% dextrose in 1. The fluid of choice in the absence of labora- water, 0.45% NaCl in 2.5% dextrose) tory data is an alkalinizing basic electrolyte 3. If serum sodium is low (hyponatremia), fluids solution (lactated Ringer’s solution, should contain more salt However, hypertonic Plasma-Lyte 148, Normosol-R) fluids are usually not used unless hyponatremia 2. If extra sodium or chloride is needed to main- is severe tain volume expansion or correct metabolic B. Preservatives alkalosis, 0.9% saline is chosen 1. Benzoic acid may be used as a preservative, 3. When treating patients with hypernatremia or and can be toxic a water deficit, choose a low-sodium fluid 2. Signs of toxicity are neurologic (0.45% saline in 2.5% dextrose, Plasma-Lyte 56, 3. Do not use fluids containing preservatives in Normosol-M, or 5% dextrose in water) cats, puppies, or small dogs 4. Keep a synthetic colloid on hand to administer VIII. Routes of administration for parenteral fluids in conjunction with crystalloid fluids when A. SC route rapid intravascular expansion is needed or if 1. Do not use in shock, severe dehydration, hypo- there is lowered oncotic pressure thermia, or emergency replacement of fluids VI. Supplementation of parenteral fluids 2. Do not give 5% dextrose in water SC with A. Potassium severe dehydration 1. Added to fluids if serum potassium concentra- 3. Choose a site on the trunk for administration tion is less than 3.5 mEq/L. May still be indi- B. Intravenous (IV) route cated if potassium is between 3.5 and 4.5 mEq/L 1. Use for accurate delivery of large amounts of if ventricular arrhythmias are present fluids 2. Add approximately 20 to 30 mEq/L of potas- 2. Use the jugular vein in cats and small dogs, or sium to maintenance fluids if needed if serious disease is present 3. The rate of infusion is most important. Do not 3. Cephalic, femoral, or lateral saphenous veins exceed a rate of 0.5 mEq/kg/hr are also used 4. Use potassium supplementation with caution 4. Use 20- to 22-gauge in cats and small dogs, and as death can result due to hyperkalemia 14- to 20-gauge in medium to large dogs B. Alkali 5. Place catheter aseptically, and change every 1. Add sodium bicarbonate if alkali replacement 72 hours. Monitor for fever, white blood cells is needed quickly (WBCs), and heart murmurs  CHAPTER 14 Emergency Medicine 203 C. Intraperitoneal route is used for transfusions in anemic puppies and kittens IX. Rate of fluid infusion A. It is best to distribute fluids evenly throughout the day 1. May not be possible if the IV line cannot be watched 2. Can give the 24-hour load over 4 to 8 hours if necessary B. Infusion pumps provide an accurate method of delivering IV fluids Femoral a. C. “Ins and outs” 1. Measure urine output in animals with severe oliguria or polyuria. Otherwise, fluid needs are overestimated in oliguria and underestimated in polyuria 2. Body weight should remain static X. Monitoring efficacy of fluid therapy Dorsal metatarsal a. A. Body weight: A gain or loss of 1 kg body weight represents an increase or decrease of 1000 mL of body water A B. PCV and plasma protein should both decrease with successful rehydration C. Central venous pressure (CVP) should be moni- tored to prevent overloading of the heart and pul- monary edema. If CVP increases suddenly, the rate of fluid administration should be decreased D. Electrolyte and acid-base status: Determine elec- B trolytes and acid base status every 12 to 24 hours XI. Overhydration Figure 14-1 A, Femoral artery puncture. B, Dorsal metatarsal artery puncture. (From Birchard SJ, Sherding RG, editors. Saunders Manual A. Clinical signs include an increase in body weight, of Small Animal Clinical Practice, 3rd ed. St Louis, 2006, increase in CVP, increased urination, gelatinous Saunders.) feel to SC tissue, pulmonary edema, vomiting, or diarrhea B. Discontinue all IV infusions, and give furosemide EMERGENCY TECHNIQUES I. Arterial sampling for blood gas analysis A. Do not perform if a severe coagulopathy is present B. Use a heparinized syringe. The most common sites are the femoral artery in the inguinal region, and the dorsal metatarsal artery distal to the tarsus joint (Figure 14-1) C. After bleeding, place firm pressure over the site for 3 to 5 minutes II. Nasogastric tube A. Do not place in patients with deforming facial trauma, in brachycephalic breeds with respira- tory distress, if severe coagulopathy is present, or if there is severe vomiting B. Premeasure the catheter to the last rib. Place several drops of local anesthetic into the nostril and wait several minutes C. Place the tip of the catheter in the nostril, and gently push the catheter up on the nasal phil- trum, advancing the tube in a ventral and medial direction into the ventral meatus (Figure 14-2) D. Suture the tube to the nostril, and use skin Figure 14-2 Positioning for placement of nasal catheter. (From Birchard SJ, staples to attach the tube to the face Sherding RG, editors. Saunders Manual of Small Animal Clinical Practice, E. Verify placement with radiographs 3rd ed. St Louis, 2006, Saunders.) 204 SECTION II SMALL ANIMAL III. Tracheostomy C. A good site for collection in standing patients is A. Severe coagulopathy is a contraindication caudal to the spleen, slightly to the right of mid- B. Use rapid IV anesthesia; clip and prepare the skin line, with the needle directed toward the urinary C. Incise skin from larynx to the thoracic inlet. bladder. If in left lateral recumbency, go caudal to Bluntly force the tips of Mayo scissors through the umbilicus, slightly to the right of midline, with the tissue. Incise the sternohyoideus muscle to the needle directed toward the urinary bladder expose the trachea D. Aspirate gently to avoid clogging of the needle D. Either incise between two rings in the midcervical with omentum trachea or longitudinally cut through several V. Thoracocentesis rings. Insert tracheostomy tube (choose a tube A Do not attempt in animals with chronic effusions that fits loosely). Suture the skin edges (especially cats). These patients are at high risk (Figures 14-3 and 14-4) for developing fibrosing pleuritis E. Clean or replace as necessary B. If there is fluid in the chest, the site should be ven- IV. Abdominocentesis tral in the 3rd to 7th intercostal spaces about one A. Severe coagulopathy is a contraindication. Do not third of the distance between the costochondral use a blind technique if there is a large abdominal juction and sternum. If there is pneumothorax, the mass or significant organomegaly site should be dorsal in the 5th to 9th intercostal B. It is best to have the patient standing or in sternal spaces about one third down from the dorsal recumbency. Left lateral or dorsal recumbency chest wall can also be used C. Advance the sharp point, with slight negative pres- sure on the syringe, until a “pop” through the pari- etal pleura is felt. Advance catheter, remove needle or stylus, attach three-way stopcock, and drain D. Avoid laceration of the lung parenchyma or Between the rings laceration of a coronary artery SHOCK I. Etiologies A. Lack of oxygen transport 1. Hypovolemia A 2. Hypoxia B. Cardiovascular system abnormalities C. Sepsis II. Clinical signs B A. Depressed mentation B. Weak pulse indicating decreased cardiac output Figure 14-3 Between-the-rings tracheostomy with stay suture or peripheral vascular resistance placement. (From Birchard SJ, Sherding RG, editors. Saunders Manual of C. Color of mucous membranes Small Animal Clinical Practice, 3rd ed. St Louis, 2006, Saunders.) 1. Pale: Reflects anemia or hypovolemia 2. Gray or cyanotic: Reflects arterial hypoxemia or severe cardiovascular compromise 3. Brick red: Common in septic shock D. Hypothermia with cold extremities E. Prolonged capillary refill time indicating hypovolemia and poor peripheral blood flow F. Elevated heart rate G. Increased respiratory rate H. Decreased urine output III. Monitoring A. Blood volume is the most important parameter to optimize. Measure CVP using a manometer attached to a jugular catheter. Maintain plasma proteins B. Arterial pressure can be assessed via digital palpation B C. Cardiac output 1. Urine output is a good indicator Through the rings 2. Capillary refill time, body temperature, and A mentation also reflect cardiac output D. Oxygen delivery is reflected in the color of Figure 14-4 Through-the-rings tracheostomy with stay suture mucous membranes, body temperature, respira- placement. (From Birchard SJ, Sherding RG, editors. Saunders Manual of tory rate, and temperature. Measure hematocrit Small Animal Clinical Practice, 3rd ed. St Louis, 2006, Saunders.) frequently during fluid therapy  CHAPTER 14 Emergency Medicine 205 V. Treatment I. Miscellaneous treatments A. The goal is to optimize functions of the cardiovas- 1. Broad spectrum antibiotics are indicated cular system especially in septic shock B. Initial therapy 2. Maintenance fluids should contain 5% dextrose 1. Establish an airway and administer oxygen if needed CARDIOPULMONARY RESUSCITATION 2. Obtain history; perform physical examination 3. Place a jugular catheter I. Phase 1: Basic life support 4. Obtain blood for complete blood cell count A. Airway: Establish an airway as soon as possible (CBC), hematocrit, total protein, electrolytes, (endotracheal tube, tracheotomy, mouth to muzzle creatinine, and glucose B. Breathing: Use a ventilator or exhaled air. Do not C. Blood volume overinflate the lungs. Sedation or anesthesia may 1. Administer either 0.9% NaCl or lactated be necessary Ringer’s solution to ensure plasma volume C. Circulation: Closed chest compression expansion. If the animal is not hydrated, 1. In dogs that weigh less than 5 kg, use the 0.7% NaCl (hypertonic saline) can be used in thumb and first two forefingers to compress combination with hetastarch the thorax from side to side. In larger dogs, 2. Re-establish normal arterial pressure use the heel of the hands. Provide 80 to 3. Give fresh or frozen plasma if hypoproteinemia 100 compressions/minute is present. Synthetic colloids (such as heta- 2. Ventilate once for every 15 chest compressions starch) can also be used 3. If a third person is available, use the palm of 4. Give fresh or stored blood if the hematocrit the hand to compress the abdomen against the and total protein are very low spine for 5 to 10 seconds. Do this 2 to 3 times D. Blood flow per minute. 1. Evaluate cardiac function if CVP has increased II. Phase 2: Advanced life support but other signs of cardiac output are not A. Drug Therapy: Administer IV if possible normalized 1. Epinephrine to increase heart rate and blood 2. If the electrocardiogram is normal, administer pressure a positive inotropic agent such as dobutamine 2. Lidocaine to treat cardiac arrhythmias. or dopamine. Epinephrine can also improve Do not give to patients with third-degree contractility and increase cardiac output atrioventricular (AV) block 3. Correct any cardiac arrhythmias 3. Sotalol is used for long-term therapy of E. Blood pressure arrhythmias 1. If the pulse is weak or not palpable, 4. Sodium bicarbonate treats metabolic acidosis. blood pressure needs to be increased Not needed until after 10 to 15 minutes of arrest immediately 5. Anticholinergics (atropine) treat bradyarrhyth- 2. Epinephrine can be used if shock is severe mias. Do not give unless indicated 3. Do not use an abdominal wrap to increase 6. Calcium chloride can increase myocardial blood pressure contraction and cardiac output. Do not use 4. Manage hemorrhage with aggressive fluid during the initial phase of treatment replacement B. Parenteral fluids are mandatory (see previous F. Oxygen delivery section on fluid therapy). Use whole blood if 1. If the hematocrit is below 20%, replace red hemorrhage is severe blood cells C. Electrocardiography (see section on cardiology) 2. Administer corticosteroids before transfusion D. Treat bradycardia. If hypoxemic, large doses of to reduce transfusion reactions epinephrine may be needed. Isoproterenol may 3. Administer oxygen supplementation be effective in some cases 4. With severe lung injury, assist ventilation E. Treatment of ventricular fibrillation. The only G. Correct acid-base and electrolyte disturbances consistent method for treatment is with electrical 1. Perform a blood gas analysis to assess defibrillation metabolic acidosis. Correct acidosis with F. Open-chest cardiac massage should be consid- sodium bicarbonate ered if 5 minutes of closed chest compression 2. Hyperkalemia is common and usually corrects and epinephrine are ineffective with fluid replacement therapy and improve- III. Phase 3: Prolonged life support. Adequate oxygen- ment of metabolic state ation is critical 3. Hypokalemia occurs commonly after aggres- A. Gauging, Hypnogenesis (sedation, pain control), sive fluid therapy. Maintenance fluids should Intensive care contain KCl B. Drug therapy H. Corticosteroid therapy should not be used in 1. Catecholamines (dopamine, dobutamine) to in- cases of septic shock. Corticosteroids crease cardiac output and peripheral perfusion (such as dexamethasone sodium phosphate 2. Diuretics (furosemide) to treat pulmonary or prednisolone sodium succinate) should edema. Mannitol can be used if the cardiac be given early in the course of therapy arrest was longer than 3 minutes 206 SECTION II SMALL ANIMAL 3. Glucocorticoids (dexamethasone or prenisolone IV. Treatment sodium succinate) prevent histamine release, A. Early treatment is necessary to reduce mortality stabilize membranes, and cause vasodilation B. The core temperature needs to be lowered early. 4. Calcium entry blockers (diltiazem) prevent Cooling should be started during transport to the reperfusion injury hospital 5. Sedation. Diazepam is a good alternative to 1. Use cool water to wet the patient, and provide pentobarbital air movement to enhance evaporation 6. Antibiotics 2. Do not use cold water or ice water because to IV. Prognosis is good if there is rapid recovery of do so will result in vasoconstriction and loss of corneal reflexes, swallowing, and spontaneous heat dissipation. Shivering can also result, breathing which generates heat C. On arrival to the hospital, if the body tempera- ture is below 104° F, cooling measures should BLOOD TRANSFUSION be stopped to prevent the development of I. Whole blood is indicated when there is a rapid hypothermia decrease in PCV D. Fluid therapy may not be necessary in early cases II. Crossmatching of heatstroke, but may need to be aggressive in A. Perform before transfusion severe cases. A combination of crystalloid and B. Collect both RBCs and serum from both the colloid fluids is recommended donor and the patient E. If DIC is present, the administration of fresh or C. Measure compatibility between donor and patient frozen plasma is indicated at three temperatures F. Broad-spectrum antibiotics are recommended D. Incompatibility is agglutination or hemolysis 1. Major incompatibility: Mix 100 L donor cells ANAPHYLAXIS  100 L patient serum 2. Minor incompatibility: Mix 100 L patient cells I. Anaphylaxis is a life-threatening allergic reaction  100 L donor serum (type I hypersensitivity) E. Donors can be used if there is mild agglutination II. There is an interaction of antigen and immunoglobu- in the minor cross-match in an emergency lin E (IgE) antibody on the surface of mast cells, F. In dogs, it is best to use animals that do not have which causes the release of histamine dog erythrocyte antigen DEA-1 and DEA-7 III. Triggers include insect and reptile bites, G. Most cats have type A blood but should still be medications, anesthetics, and foods crossmatched due to fatal transfusion reactions IV. Clinical signs include hypotension, bronchospasm, pruritus, erythema, pharyngeal and laryngeal edema, vomiting, and arrhythmias HEATSTROKE A. In dogs, the liver is the shock organ. Clinical I. Cellular damage results from a marked increase in signs result from hepatic congestion and portal body temperature with loss of temperature control. hypertension In heatstroke, heat production overwhelms normal B. In cats, the lungs are the shock organ. heat dissipation mechanisms Respiratory distress is usually the first sign II. Heatstroke usually occurs when the ambient temper- V. Diagnosis is based on history, exposure, and clinical ature is high. High humidity, lack of water, poor ven- signs tilation, obesity, airway obstruction, heart disease, VI. Treatment central nervous system disease, hyperthyroidism, A. Establish an airway seizures, and lack of conditioning can contribute to B. Maintain vascular access, and start fluid therapy the development of heatstroke for hypovolemic shock III. Clinical signs C. Administer epinephrine immediately A. Early clinical signs include panting, hypersaliva- D. Can also administer glucocorticoids, aminophyl- tion, tachycardia, short capillary refill time, line, antihistamines, atropine, and pressors increased blood pressure, bounding pulse, (dopamine) excitation, hyperactivity, elevation of body VII. Prognosis is good if treatment is instituted early temperature VIII. Anaphylaxis is prevented by avoiding exposure to B. As heatstroke progresses, signs of shock are known triggers in the future more pronounced. Rectal temperature may be elevated but can be normal to low. Tachycardia, Supplemental Reading tachypnea, and hyperventilation are common. Dehydration is common, and hematemesis and Bateman S, Chew DJ. Fluid therapy for dogs and cats. In melena signify injury to the gastrointestinal tract. Birchard SJ, Sherding RF, eds. Manual of Small Animal Mentation is altered, and the pupils are dilated. Practice, 3rd ed. St Louis, 2006, Saunders, pp. 82-99. Disseminated intravascular coagulation (DIC) is Bateman SW, Buffington CA, Holloway C. Emergency and common, with petechiation and hemorrhage. critical care techniques and nutrition. In Birchard SJ, Azotemia from renal failure is common. Seizures Sherding RF, eds. Manual of Small Animal Practice, or coma may occur 3rd ed. St Louis, 2006, Saunders, pp. 29-50.