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Fluid Balance & Dehydration

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Nurse Grad Issue 2007 • Page 43
Fluid Balance & Dehydration

When it comes to assessing fluid balance, new grads must ask questions, seek mentors — and soak up knowledge like sponges

Kids play in it, adults pay for it, and most people appreciate the bounty of nature that grows in it. But everyone drinks it. Aside from the air we breathe, water is the most vital component to sustaining life. Every body system requires it to function properly, and maintaining a state of water balance is essential for health and well-being.

Although the total body water content varies according to age, gender and total fat content, the average adult male is comprised of about 60 percent water, while the average female is about 52 percent.1 Full-term newborns contain 75-80 percent water, which slowly decreases to adult levels by 1 year of age.2

The body continually loses water through the skin, mucous membranes, lungs, bowels and kidneys. And while precise requirements vary, fluids must be replenished on an ongoing basis. In addition, some patient populations are at greater risk for fluid imbalance and dehydration, including infants and children, the elderly, athletes, people living or working in hot environments, as well as patients with illnesses or injuries, such as diabetes and burns.3

The first symptom of inadequate hydration is thirst. However, 2 percent of total body water content can be lost before the thirst mechanism is present, and a number of conditions can interfere with it. And while complications are rare in mild dehydration, if fluids aren't replaced, the consequences can be life-threatening.4

At 5-6 percent water loss, symptoms may include lethargy, nausea, confusion, headache and paresthesias. Heart and respiratory rates rise, while blood pressure falls. With a 10-15 percent loss, muscles may become spastic, vision may dim, urinary output is markedly decreased, vital signs continue to decompensate and patients may become delirious. Losses greater than 15 percent usually are fatal.4

At some point, all nurses will be exposed to the many faces of fluid imbalance. So a good first step for new graduates is to recognize common symptoms and have a basic understanding of diagnostic indicators and treatment options in vulnerable patient populations.

The Elderly

The following is a representative case study contributed by Tamara Murphy, MS, CCRN, APRN,BC, gerontology clinical nurse specialist, and Victoria Schirm, PhD, RN, FNGNA, director of nursing research, Penn State Milton S. Hershey Medical Center, Hershey, PA.

On a warm summer day, an 80-year-old female embarks on a bus tour of local shopping outlets. At approximately 11 a.m. she complains of dizziness, then stumbles and falls. When EMS personnel arrive on the scene, they find her prone but awake. After confirming airway, breathing and circulatory status, they perform a basic coronary and stroke survey.

Although appearing slightly dazed, the patient is oriented to person, place and time. She has no unilateral weaknesses, visual or speech abnormalities and denies chest, arm or neck pain. Her mouth is dry and she complains of thirst. Vital signs: temperature 97.2ûF; heart rate 116/min. and slightly irregular; respiratory rate 26/min.; BP sitting 100/50 mm Hg, standing 80/50 mm Hg. Cardiac monitoring at the scene reveals no ST abnormality.

A verbal assessment reveals a history of atrial fibrillation and mild CHF. The patient hasn't voided since awakening and states she took her "heart and water pills and an aspirin" with toast and one cup of coffee at 7 a.m. She denies further intake.

"It's not uncommon for patients to self-limit fluids if they're unsure of bathroom facilities," said Victoria Schirm, PhD, RN, FNGNA.

Females More Susceptible

Adding that females are more susceptible to dehydration than males for biological as well as social reasons, Tamara Murphy, MS, CCRN, APRN,BC, explained that fat has a lower water content, and women have a higher fat-to-muscle ratio than men. And Schirm pointed out that as primary caregivers, women are often more attentive to the health status of others than their own.

To rule out CHF, assessment would include chest auscultation to detect rales in the posterior and lateral lung fields, as well as evaluation of ankle edema and neck vein distention.

EMS personnel start an IV infusion of normal saline at 75 cc/hr. The patient is transported to the ED at Penn State Hershey Medical Center. Diagnostic workup includes electrolytes, a renal panel and a CBC.

Hypertonic Dehydration

"This is probably a hypertonic dehydration, meaning she's lost fluid but not necessarily sodium," Murphy said. "And because she takes diuretics and has had IV fluid replacement without added potassium, she may be a little hypokalemic."

Because kidney disease also is prevalent in the elderly, an increased BUN-to-creatinine ratio on the renal panel is the primary marker in dehydration as opposed to renal insufficiency (see sidebar: Dehydration).5 "Other clinical signs of dehydration are furrows in the tongue, dry mucous membranes and poor skin turgor," Murphy said.

Diagnosis is mild dehydration; treatment is rehydration and education.

Under normal circumstances, the Institute of Medicine advises that men consume about 13 cups of total beverages a day and women consume about 9 cups a day.6 "But during exercise or increased activity, we advise as much as 30 cc of fluid per kilogram at least every 20-30 minutes," Murphy said.

So for a 145-pound (65.9 kg) person, a minimum of about one cup every half hour is recommended.

"Any fluid is better than none, but water is best," Murphy continued. "And I teach my patients to watch their urine color — if they're getting dry, it will be dark and concentrated."

Suboptimal choices are caffeinated beverages because of their diuretic effect and most sports drinks because of their high sugar content. If electrolyte placement is needed, she said a product such as Pedialyte is best.

And because elderly patients may have several chronic diseases and often walk a fine line between dehydration and over-hydration, Murphy said nurses must hone their assessment skills and be able to interpret clinical findings within the context of specific disease processes.

Patient Education

Adding that nursing interventions vary according to setting, Schirm said patient education should always address the potential for dehydration.

"Often older adults who come in for outpatient procedures have been fasting for long periods of time," Schirm said. "There needs to be a greater awareness of preventing, recognizing and treating dehydration in the elderly."

Pediatrics

The following case study was contributed by Geneva Burnap, MBA, BN, RN, CPN, administrative supervisor at Children's Medical Center, Dallas.

An 11-month-old boy with a 24-hour history of vomiting and diarrhea is a direct admit from a pediatrician's office. Preliminary diagnosis is rotavirus. Although Geneva Burnap, MBA, CPN, BSN, RN, said rotavirus is fairly benign in older children, it's one of the most common causes of dehydration in infants.

According to the infant's mother, he hasn't kept anything down for a day. She hasn't counted diaper changes but reports multiple watery stools. He is awake and fussy. Temp is 101ûF; heart rate is 160/min.; respirations are 54/min.; BP is 80/50 mm Hg, and weight is 22 pounds (10 kg).

Start an IV

"In the acute pediatric setting, IV skills are critical," Burnap said. "We'd want to get a peripheral IV started as quickly as possible." Explaining that the pediatric advanced life support protocol regarding IV insertion recommends no more than three peripheral attempts, she said if unsuccessful, an intra-osseus route may be necessary — a procedure new grads don't perform.

However, a peripheral IV is established and normal saline is infused at 40 cc/hr (see sidebar: Pediatric IV Rate Formula). Blood chemistry is checked every 8-12 hours to monitor the status of rehydration and to make any changes in IV solution.

Burnap said if severe dehydration is prevented and fluid balance is restored, rotovirus usually runs its course without complications. However, if the child remains symptomatic, other pathologies must be considered.

"We look for the most common and then rule out other possibilities," she said. "If fever persists, we'd do a blood culture before starting antibiotics."

Parent Teaching

Aside from heriditary diseases or other uncommon ailments, nursing intervention for dehydration after stabilization and restoration of fluid balance is education.

"Babies don't come with an instruction book," Burnap said. "With new grads, we stress parent teaching and providing reassurance that they can manage their child's care at home."

Instruction should include the difference between spitting up and projectile vomiting, as well as how many wet diapers are normal according to their child's age. Small amounts of fluid should be offered frequently, and drinks with a high sugar content are discouraged. If electrolyte replacement is necessary, Pedialyte, Rehydralyte and sometimes Gatorade are recommended.

"New grads need to know that listening to parents and taking a good history to determine what is normal for their child is key to good patient care and discharge teaching," Burnap said.

Burns

The following case study was contributed by Yvette Wilson, RN, charge nurse, the Johns Hopkins Burn Center in Baltimore.

A 65-year-old male in an outlying rural community was using an accelerant to burn trash. The wind shifted, catching dry foliage on fire. The patient attempted to extinguish the flames, suffering first and second degree burns with a total burn surface area (TBSA) of 75 percent. He was intubated at the scene by rescue personnel. Large bore intracaths were inserted bilaterally, and he was evacuated by emergency air transport to the burn center.

"Skin is the largest organ in the body," Wilson said. "Burn patients lose the protective barrier that maintains fluid balance and prevents infection." And while burn management presents a myriad of challenges typically unencountered in critical care nursing, the amount of IV fluids required to prevent systemic organ failure can be astounding to new graduates and seasoned nurses alike.

Wilson said it's unusual, but not unheard of, to give 2,000 cc/hour for the first 8 hours. "And they might also require additional fluid boluses to maintain an adequate urinary output or blood pressure," she said.

Burn fluid resuscitation, the amount of fluids given in the first 24 hour, is usually calculated using the Parkland Burn Formula, which multiplies the patient's weight in kilograms by the TBSA. This number is then multiplied by four. Half of the resultant number is given during the first 8 hours, while the second half is given over the next 16 hours.7

The formula applied to a 200 pound (90.9 kg) patient with a 75 percent TBSA:

  • 90.9 x 75 = 6,817.5

  • 6,817.5 x 4 = 27, 270

  • 27,270 cc is the total 24 hour requirement

  • Half 13,635 cc is given during the first 8 hours

  • The IV rate is 1,704 cc/hr. for the first 8 hours

  • The rate is 852 cc/hr. for the next 16 hours8

    Hence, the need for two large bore IV sites, as well as IV pumps used in the burn setting that have the capability of delivering almost 1,000 cc/hr.

    After the first 24 hours, fluids may be continued at the 16-hour rate, but multiple factors are taken into consideration including urinary output and lab values.

    Vigilance Required

    Fluid balance requires an understanding of disease pathologies, as well as the needs of specific patient populations. However, throughout the continuum of healthcare delivery, fluid balance should be an integral part of all nursing assessments. New graduates must be vigilant to ask questions, seek out mentors and, when it comes to water, soak up knowledge like sponges.

    For a list of references, visit www.advanceweb.com/nurses; click on References.

    Elissa Crocker is a frequent contributor to ADVANCE.

    Dehydration

    Dehydration: The body loses more water than is taken in

    Minimal criteria for clinical diagnosis

  • Suspicion of increased output and/or decreased intake

  • At least two physiological or functional signs or symptoms, such as dizziness, dry mucous membranes, functional decline

  • A BUN/creatinine ratio of >25-1; OR orthostasis, a 20-point drop in sitting to standing systolic BP; OR a pulse of >100 beats/minute; OR a 10-20 beats/min. increase in sitting to standing pulse rate

    If indicated, diagnostic work-up at minimum should include electrolytes, BUN and creatinine. Normals:

  • Na = 135-145 mEq/L

  • K = 3.5-5.5 mEq/L

  • Cl = 95-112 mEq/L

  • CO2 = 22-32 mEq/L

  • BUN = 7-27 mg/dL

  • Creatinine = 0.7-1.4 mg/dL

  • BUN/creatine ratio: 10-1 Ð 20-1

    Understanding its nature, causes and severity is critical

  • Hypertonic dehydration: water loss exceeds salt loss; higher serum Na

  • Hypotonic dehydration: water loss is less than salt loss; lower serum Na

  • Isotonic dehydration: water loss and salt loss equal

  • Excessive water intake and retention

  • Excessive water and salt retention

    Characterizing severity

  • Mild: lab abnormalities such as marginally elevated BUN or high or low Na that do not seriously impair circulation, organ function or level of functioning.

  • Moderate: lab abnormalities exist that impair circulation or organ function but are not immediately life threatening, such as decrease in blood pressure in a patient with a sodium level of 155 mEq/L.

  • Severe: lab abnormalities causing significant, life-threatening risks or problems with circulation, organ function or activities of daily living such as BUN elevation >100 mg/dL; or confusion in a patient with a Na <123 mEq/L.

    Treatment must be based on the underlying causes of the problem

  • For example, hyponatremia (serum Na <125 mEq/L) differs according to cause.

  • If caused by salt and water loss, fluids and Na may be indicated.

  • If caused by excess water intake or retention, fluids may be restricted.

    Source: American Medical Directors Association. Dehydration and fluid maintenance: National Guideline Clearinghouse: www.guideline.gov

    Pediatric IV Rate Formula

    The first 10 kg: 4 cc/hr. per kg

    The next 10 kg: 2 cc/hr. per kg

    The remaining kg: 1 cc/hr. per kg

    For a child weighing 22 kg (48.4 pounds),

    the IV rate is 62 cc/hr.

    10 kg x 4 = 40 (the first 10 kg)

    10 kg x 2 = 20 (10 - 20 kg)

    2 kg x 1 = 2 (the remaining 2 kg)

    Total = 62 cc/hr.

    Source: Children's Medical Center, Dallas




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