INTRAVENOUS FLUID THERAPY: A REVIEW

Joanne Gaffney, RN, CANP, MS

If this common intervention isn’t managed vigilantly, it actually can exacerbate the risks it’s designed to alleviate.

umerous conditions— In this article, I’ll review the ba- The body loses fluid through metabolic, infective, sics of and the etiology such normal physiologic func- traumatic, and iatro- of fluid loss. I’ll discuss how to as- tions as and urination. N genic—can cause fluid sess fluid depletion, outline the prin- But when certain diseases or en- depletion. In such cases, initiat- ciples of therapy, vironmental conditions substan- ing intravenous (IV) fluid replace- and explain the context in which tially increase fluid loss, the body ment is commonplace. In fact, IV various types of solutions are ad- may be unable to maintain ho- fluid replacement therapy is one ministered. I will not, however, meostasis, and fluid replacement of the most common invasive cover the treatment of diabetes mel- may be necessary. procedures hospitalized patients litus and diabetes insipidus, which undergo, and it’s performed in cer- follow different principles that are NORMAL FLUID LOSS tain outpatient and home care set- beyond the scope of this article. Normal fluid loss includes both in- tings as well. sensible and sensible losses. Each Fluid loss can put patients at FLUID MECHANICS day the skin loses approximately substantial risk for fluid and elec- represents approxi- 300 mL and the lungs lose approxi- trolyte imbalances, which can lead mately 60% of a person’s total mately 700 mL of water from evap- to shock and multiple organ failure. weight. For a 70 kg man, this oration. This insensible water loss Although IV therapy for fluid deple- amounts to about 42 L. Intracellular remains mostly stable at roughly 1 tion is practiced widely, if not ad- fluid accounts for two thirds of it L/day and is responsible for negligi- ministered scrupulously, it actually (roughly 28 L) and extracellular ble loss. Hyperventila- can exacerbate the fluid and elec- fluid for the other third (about 14 L). tion intensifies losses from the trolyte imbalance. It’s essential, includes both lungs, and fever increases losses therefore, that the practitioner re- the interstitial fluid (around 11.2 L) from both skin and lungs. The sponsible for initiating and main- and plasma (the remaining 2.8 L). amounts of fluid lost through these taining fluid replacement therapy In addition to plasma, intravascular two routes increases by 10% for understand the basic mechanisms fluid contains the fluid volume of every degree of fever above 37° C.1 supporting fluid balance, the conse- its other major constituent, the red Sensible water losses occur quences of fluid loss, and the ra- cells. mainly through urination, but also tionale for fluid replacement. The fluid component of red through perspiration and defeca- blood cells represents about 2 L of tion. The average adult voids be- Ms. Gaffney is a nurse practitioner in the surgical intracellular fluid. A person’s total tween 1 and 1.5 L daily. Urine service at the Northport VA Medical Center, North- blood fluid volume, therefore, and generally port, NY and a clinical instructor in the department of nursing at Nassau Community College, Garden equals about 5 L—plasma plus the range in amounts from 40 to 80 City, NY. fluid component of red blood cells. mEq/L. Perspiration contains

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sodium in amounts ranging from ments, where it’s unavailable to sup- temperature, hyperglycemia, dia- 34 mEq/L to 50 mEq/L. Normal port the circulation).3 Third spacing betes insipidus, or hyperalimenta- sweating, however, accounts for a can occur with ascites, bowel ob- tion) and with saltwater loss (GI daily fluid loss of only 100 mL. Pro- struction, pancreatitis, and in- tract loss, profuse sweating, hy- fuse sweating, as occurs with stren- jury (from trauma, infection, or poaldosteronism, diuretic use, or uous exercise, can raise this burns) that causes . third spacing). amount to 1,500 mL, making both If water and salt are lost in iso- A drop in intracellular fluid, as fluid and salt loss significant. In the tonic amounts, there is no osmotic occurs with simple water loss, typi- absence of diarrhea, fluid lost in shift in fluids between the extracel- cally causes and such central stool ranges from 100 to 200 mL in lular and intracellular compart- nervous system disturbances as adults. ments. In such cases, volume restlessness, weakness, listless- In total, therefore, basic adult depletion occurs only in the extra- ness, muscular twitching, irritabil- fluid losses equal approximately 2.5 cellular fluid compartment. ity, disorientation, delusions, and L daily. These losses should be hallucinations. The patient may taken into account when consider- ASSESSING FLUID DEPLETION have flushed skin, fever, dry and ing fluid replacement. The degree of fluid depletion may sticky mucous membranes, oli- be estimated by weight loss, with guria, or orthostatic hypotension. ABNORMAL FLUID LOSS one pound representing 500 mL of Laboratory values show an ele- Excessive fluid loss can mean ei- fluid. Using this guide, weight vated serum sodium level (above ther dehydration (the loss of simple losses of 2% (or 2.4 lb in a 120-lb 145 mEq/L), increased serum os- water or of more water than salt) person) would be considered mild molality (above 295 mOsm/kg), re- or hypovolemia (the loss of iso- fluid depletion, whereas 5% (or 6 lb duced urinary sodium (10 to 20 tonic saltwater). These two types in a 120-lb person) would be con- mEq/L or less), and—except in the of water loss affect the body in dif- sidered moderate and 8% (or 9.6 lb case of diabetes insipidus—a nor- ferent ways. or more in a 120-lb person) would mal urine specific gravity above Simple water losses may be be considered severe.3 1.015. If fluid depletion is due to di- brought on by water deprivation or Alternatively, water deficit may abetes insipidus, urine specific by an increase in body or environ- be calculated as follows: water gravity may be as low as 1.005.3 mental temperature. Hypergly- loss in liters = total body water x A drop in extracellular fluid, as cemia, diabetes insipidus, and [(serum sodium/140) – 1], where occurs with both simple and salt- nasogastric overfeeding (especially total body water in liters is said to water losses, causes thirst, fatigue, if not balanced with adequate be 60% of body weight in kilo- muscle cramps, weakness, and water intake) are other possible grams for lean men and 50% of postural dizziness.5 Body tempera- causes of simple water loss.2 body weight in kilograms for lean ture may be low and the skin is dry. The loss of simple water in- women.4 Fluid loss estimates must Assess skin turgor by pulling up on creases the solute content of the factor in history and physical signs the skin covering the sternum: blood, which results in intravascu- (though these are minimal when Tenting that remains for several lar hypertonicity. This causes an os- depletion is mild) and replacement seconds indicates fluid deficit. The motic shift of water from within must be guided by continual physi- mucous membranes are dry and the cells into the plasma. There is, cal assessment and laboratory eyeball tension may be reduced (to thus, a loss of fluid from both the findings. the touch). The tongue is shrunken extracellular and intracellular com- History should include medica- and coated with multiple furrows partments. tions, fluid intake and output, ill- (in addition to the normal midline Saltwater may be lost with gas- nesses, and any signs or symptoms furrow). Typically, a diminished ap- trointestinal (GI) losses, sweating, of fluid loss (such as thirst, fatigue, petite progresses to nausea and hypoaldosteronism, diuretic use, weakness, malaise, or decreased vomiting. and third spacing (the leakage of urinary output). Keep in mind eti- If salt is lost in proportion to saltwater fluid into a third space ologies associated with simple water, the serum sodium level may that’s outside of the extracellular water loss (fluid deprivation, an in- be normal, though there would be a and intracellular fluid compart- crease in environmental or body relative increase in urea, albumen,

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Continued from page 42 red blood cells, , and 0.45%, or 77 mEq/L. Potassium ad- INTRAVENOUS THERAPY FOR Hct secondary to hemoconcentra- ditions start at 20 mEq/L and can ABNORMAL FLUID LOSS tion. If more water than salt is lost, be increased to 40 mEq/L, which is For abnormal water losses that ex- laboratory findings are similar to usually sufficient to replace normal ceed the loss of salt, treatment con- those that accompany simple water loss. sists of simple water administration. (intracellular fluid) loss. Calories also are added to re- Often, this water replacement must With a 20% fluid loss or less, car- placement fluid therapy. Each 1-L be administered intravenously, as diac output remains adequate. With solution containing 5% dextrose patients in such cases tend to vomit. moderate fluid deficit cardiac out- supplies 50 g of carbohydrate and Usually, a 5% glucose solution is put decreases. The neck are approximately 170 calories. While used. It’s administered gradually flat when the patient is supine (un- even 2 or 3 L provides only a por- over 48 hours. Convulsions can less the patient has congestive heart tion of the patient’s daily caloric in- occur if the brain expands too failure). refill is delayed take, it’s useful in preventing quickly. (greater than three seconds) and ketosis, which occurs with starva- Replace no more than half the urinary output reduced (25 to 30 tion. A patient who isn’t eating and patient’s water deficit within the mL/hour or less). An early and accu- is receiving parenteral therapy re- first 24 hours to lower the serum rate sign of fluid volume deficit is quires supplemental protein, vita- sodium concentration by about the presence of postural hypoten- mins, and other after 0.5 mEq/L/hr.4 Of course, frequent sion with systolic pressure dropping one week.5 A discussion of total assessment of the patient and lab 15 mm Hg or more when the patient parenteral nutrition, however, is values should guide all fluid re- moves from a supine to sitting posi- beyond the scope of this article. placement. tion.6 Another indication is the nar- For normal fluid loss, the ideal When replacing abnormal saltwa- rowing of pulse pressure. A plasma replacement generally consists of ter losses, a balanced salt solution, fluid volume deficit of 30% or more 5% dextrose in water with 0.45% such as normal saline, can be used is accompanied by hypotension; sodium and 20 mEq/L to replace half the deficit; after that, cold, clammy, mottled skin; delayed potassium delivered in amounts of the patient should be reassessed. capillary refill (of three to five sec- 2 to 3 L/day until normal oral intake Evaluate electrolytes, intake, onds or more); and stupor or coma, of fluids and food is resumed.5 and output, and consider ongoing as shock ensues and cardiac and Serum electrolytes are monitored weight and fluid losses until vital cerebral perfusion is reduced.7 and supplemental sodium and signs and urinary output are normal. potassium are adjusted accord- Serial measurement of urine sodium INTRAVENOUS THERAPY FOR ingly. For patients who require less may be useful. If urine sodium is NORMAL FLUID LOSS electrolyte replacement, hypotonic below 25 mEq/L in a patient with no If normal fluid losses are to be re- salt solutions also come in 0.33% renal disease, kidneys are sensing placed intravenously (if oral re- solutions, which contain 56 mEq/L persistent volume depletion and placement isn’t possible or is . more fluids should be given.9 contraindicated), sodium chlo- Hypertonic salt solutions have GI disorders cause a loss of elec- ride—and often potassium—may no place in maintenance fluid ther- trolyte rich fluids. Losses from the be added to the replacement fluid apy. Even isotonic saline isn’t used upper GI tract, above the pylorus, as indicated by urinary output and unless the patient’s serum sodium are isotonic and contain sodium, serum levels of these electrolytes. level falls below 130 mEq/L. Hyper- chloride, potassium, and hydrogen. Normally, sodium and potassium tonic 3% saline solution may be Losses from below the pylorus are excretion in urine varies because used if the serum sodium level falls isotonic and contain sodium, po- the healthy can conserve or below 115 mEq/L.8 tassium, and .10 Upper waste as needed—though random Close serum electrolyte monitor- GI tract losses usually occur from specimens tend to contain at least ing helps prevent overhydration vomiting or nasogastric suctioning. 40 mEq/L of both.3 and hyponatremia. Potassium in Diarrhea is the most common Customarily, when added to re- amounts greater than 40 mEq/L is cause of lower GI content loss; placement fluid, salt is replenished irritating to small veins and, there- others include intestinal resection in hypotonic amounts starting at fore, can’t be infused peripherally. and fistulas.10

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Fluid lost through vomiting and selected for replacement usually The opinions expressed herein nasogastric suctioning contains 70 depends on the fluid lost. Patients are those of the author and do mEq/L of sodium chloride, 10 to 20 who are bleeding require blood, not necessarily reflect those of mEq/L of potassium, and hydrogen which most often is infused rap- Federal Practitioner, Quadrant chloride .1 Losses of this type idly under pressure until the pa- HealthCom Inc., the U.S. govern- can result in . Since 0.45% tient’s Hct is 35%. In most other ment, or any of its agencies. normal saline solution contains 77 cases, the fluid of choice is iso- This article may discuss unla- mEq/L sodium chloride, an appro- tonic saline or lactated Ringer’s so- beled or investigational use of priate replacement fluid would lution. The rate of replacement is certain drugs. Please review contain 5% dextrose and 0.45% approximately 1 to 2 L in the first complete prescribing informa- sodium chloride with 20 mEq/L hour.9 Patients who don’t respond tion for specific drugs or drug potassium. Fluid replacement con- to the initial fluid resuscitative ef- combinations—including in- taining sodium chloride and potas- forts should have invasive hemo- dications, contraindications, sium allows for renal excretion of dynamic monitoring. warnings, and adverse effects— bicarbonate and a reversal of the The risks of congestive heart before administering pharmaco- alkalosis. For every 1 mL fluid lost failure and pulmonary edema can logic therapy to patients. in the previous 24 hours, 1 mL of be minimized through the avoid- replacement fluid is administered.3 ance of an excessively elevated pul- REFERENCES 11 1. Pestana C. Fluids and Electrolytes in the Surgi- In addition to a loss of bicar- monary capillary wedge pressure. cal Patient. 5th ed. Philadelphia, PA: Lippincott bonate, diarrhea commonly causes The rate of infusion should be Williams & Wilkens; 2000. 2. Springhouse Corporation staff. Fluids & Elec- a potassium loss of 20 to 40 rapid as long as the patient’s sys- trolytes Made Incredibly Easy! 2nd ed. Spring- mEq/L and in severe cases, such tolic blood pressure and cardiac house, PA: Springhouse Corporation; 2002. 3. Metheny NM. Fluid and Electrolyte Balance: as that associated with colitis, up filling pressure remain low. Nursing Considerations. 4th ed. Philadelphia, to 90 mEq/L. The usual replace- solutions such as albumin, plasma, PA: Lippincott Williams & Wilkens; 2000. 4. Fall PJ. Hyponatremia and hypernatremia. A sys- ment fluid for this loss is lactated or dextran, may be used instead of tematic approach to causes and their correction. Ringer’s solution. Containing 130 crystalloids, especially if plasma Postgrad Med. 2000;107(5):75–82. 5. Singer GG. Fluid and electrolyte management. In: mEq/L of sodium, 109 mEq/L chlo- is low (total Ahya SN, Flood K, Paranjothi S, eds. The Wash- ride, 28 mEq/L lactate, 4 mEq/L serum protein is less than 5.4 g/dL) ington Manual of Medical Therapeutics. 30th ed. Philadelphia, PA: Lippincott Williams & Wilkins; potassium, and 3 mEq/L , or if resuscitation is expected to re- 2001:43–75. its components are similar to quire substantial amounts of fluid 6. Cooper A, Moore M. I.V. fluid therapy. Part 1. Water balance and hydration assessment. Aust those of extracellular fluid. Since (with replacement representing Nurs J. November 1999;7(suppl):1–4. lactate is metabolized in the liver more than 5% of body weight).11 7. Schwartz GR. Shock: Clinical treatment. In: Schwartz GR, Roth PB, Cohen JS, eds. Principles to bicarbonate, lactated Ringer’s remain in the plasma and and Practice of Emergency Medicine. 4th ed. can be helpful when the patient don’t cross over into the interstitial Baltimore, MD: Williams & Wilkens; 1999:37–45. 3 8. Kee JL, Paulanka BJ. Handbook of Fluid, Elec- has mild . Electrolytes space, as do crystalloids. An im- trolyte and Acid-Base Imbalances. Albany, NY: should be monitored and re- provement in mental status, uri- Delmar Publishers; 2000. 9. Rose BD, Post TW. Clinical Physiology of Acid- placed in accordance with serum nary output, and vital signs Base and Electrolyte Disorders. 5th ed. New levels and established urinary provides evidence that tissue perfu- York, NY: McGraw-Hill; 2001. 10. Heitz UE, Horne MM. Pocket Guide to Fluid, output. As with upper GI tract sion is satisfactory. Electrolyte, and Acid-Base Balance. 4th ed. St. fluid losses, for every 1 mL fluid The ability to recognize the clini- Louis, MO: Mosby; 2001. 11. Pflederer TA. Emergency fluid management for lost from the lower GI tract over cal manifestations of fluid depletion hypovolemia. Postgrad Med. 1996;100: 243–244, the previous 24 hours, 1 mL fluid is is crucial to clinicians managing a 247–248, 251–254. replaced.3 wide variety of disease states. A basic understanding of potential WHEN THE PATIENT IS IN SHOCK causes and factors influencing fluid is most often imbalance will guide the practi- E-mail us at: due to bleeding or third spacing, tioner in providing optimal care though any of the causes of vol- and achieving the best possible out- [email protected] ume depletion can produce a simi- comes for patients requiring IV lar outcome. The type of fluid fluid replacement therapy. ●

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