Chapter 6: Fluid/Electrolyte Balance Flashcards
Is the edema acute/sudden or chronic (e.g., duration, progression)? Is it unilateral or bilateral? Is the edema generalized or localized? Is it pitting or nonpitting? Is it dependent? In addition to edema, what other characteristics are associated with the edema (e.g., redness, pain)? What is the pertinent past or coexisting medical history? What medications is the patient taking? You may want to refer to the hematopoietic function chapter and the cardiovascular function chapter to help determine the diagnosis.
Activity: Identify the probable diagnosis and what data support your decision. Describe the pathogenesis for the diagnosis. What data are inconsistent with your diagnosis? What diagnostic tests would you order, if any, and how would you treat this patient? Note: Assume history and physical examination is normal if not listed.
Case 1: Mrs. Rodriguez, a 45-year-old woman, is complaining of intermittent mild bilateral feet/ankle swelling for the past 2 months, but it is worse on her right leg. She denies leg pain, but she does describe her legs as feeling heavy at times and reports standing for long periods worsens the swelling. She notes that the veins in her legs are getting larger. For the past 8 months, she has been experiencing intermittent numbness in her feet and reports her left knee has been achy. She is a server at a busy restaurant and sometimes works 10-hour days. She denies any fever, warmth, erythema, or trauma.
- Past medical history: obesity (BMI 31); type 2 diabetes mellitus
- Medications: metformin
- Physical examination: vital signs are within normal limits; exam is unremarkable except for bilateral tortuous veins in both lower extremities, which are worse on the right leg, and decreased sensation in both feet
Mrs. Rodriguez most likely has varicose veins. Varicose veins occur as a result of improper valve function. The valves become incompetent, blood flow is reversed, and venous pressure and distention are further increased. Risk factors in this case include prolonged standing and obesity.
There is no inconsistent data with this diagnosis; she has the usual symptoms of varicose veins, which include irregular, purplish, and bulging veins; edema; fatigue; and aching, numbness, and tingling in the legs. Her intermittent numbness in her feet, however, may be associated with neuropathy from type 2 diabetes mellitus, and this should be evaluated.
Diagnosis of varicosities is usually accomplished through visualization during physical examination. Additional tests may initially include a venous duplex Doppler ultrasound. Other diagnostic tests include photoplethysmography and venogram.
Treatment ranges from conservative to invasive and includes the following measures:
- Rest with the affected leg elevated
- Compression stockings
- Avoiding prolonged standing or sitting
- Exercise
- Sclerotherapy (injection of a sclerosing agent that produces fibrosis inside the vessel) if they are small
- Surgical removal or endovenous ablation (use of radiofrequency or laser energy to cauterize the vein)
Case 2: Mr. Quincy, a 68-year-old man, is complaining of left leg swelling for the past 2 weeks. The swelling started while he was on a cruise. The swelling is intermittent and below the knee to his foot. He describes a cramplike pain in his left calf. Lately, both legs have been cramping while walking, but it resolves when he sits. He denies any fever, warmth, erythema, or trauma.
- Past medical history: iliofemoral deep vein thrombosis of his left leg after he had left hip replacement for osteoarthritis 9 months ago; treated with rivaroxaban for 6 months; stable angina; obesity (BMI 31); dyslipidemia
- Social history: quit smoking 4 years ago but resumed one-fourth pack per day 1 year ago
- Medications: simvastatin; aspirin; metoprolol
- Physical examination: vital signs are within normal limits; right leg is within normal limits except hairless, shiny skin; left leg has 1+ pitting edema in the pretibial area and foot; mild pain with left calf compression and one small tortuous vein on the medial aspect of his calf; left leg is also hairless and shiny
- Venous duplex Doppler ultrasound of his left leg performed and revealed no deep vein thrombosis
The most probable diagnosis is post-thrombotic syndrome because Mr. Quincy had an iliofemoral deep vein thrombosis 9 months ago. The disorder occurs as a result of damage to the venous valves leading to valvular incompetence and increased venous pressure as a result of the clot. He also has what sounds like a left leg varicosity that could also contribute to his symptoms.
The cramplike pain is inconsistent with post-thrombotic syndrome; his description of cramping while walking along with relief with rests are consistent with intermittent claudication as a result of peripheral artery disease (PAD). He is also a smoker, which increases his risks for PAD. The hairless, shiny skin in both legs are also consistent with PAD.
The manifestations that support the post-thrombotic syndrome are the intermittent, unilateral edema in the leg, specifically in the leg affected by a clot in the past.
A venous duplex Doppler ultrasound was already done to rule out another deep vein thrombosis. Further testing for post-thrombotic syndrome may not be necessary, but other venous studies could include photoplethysmography and venogram as diagnostic tests.
Mr. Quincy should also be evaluated for peripheral artery disease with an arterial Doppler ultrasound and ankle brachial index measurements.
He should be advised to quit smoking.
For the post-thrombotic syndrome, he could wear compression stockings and avoid prolonged standing.
Case 3: Mrs. Delaney, an 85-year-old woman, has had bilateral ankle and foot swelling for the past 3 weeks; she states her feet hurt and her shoes feel tight and describes this swelling as the first occurrence. She denies fever, erythema, warmth, or trauma.
- Past medical history: aortic valve replacement; hypertension; dyslipidemia; osteoporosis.
- Medications: amlodipine; benazepril; atorvastatin; alendronate sodium; aspirin
- Physical examination: vital signs within normal limits; exam unremarkable except for grade 1 systolic ejection murmur at the left sternal border, second intercostal space with no radiation, and mild (<1+) pitting edema bilateral ankles and feet
Mrs. Delaney’s edema is most likely a side effect of amlodipine (a dihydropyridines calcium channel blocker). These medications cause arteriolar dilatation with subsequent increased capillary pressure with fluid extravasation.
There is no inconsistent data, and the mild edema and use of amlodipine support this probable diagnosis.
No diagnostic tests are needed at this time. If bothersome, the medication can be discontinued and another antihypertensive prescribed.
Case 4: Mr. Smith, a 78-year-old man, is complaining of increased swelling in his lower legs for the past 3 weeks. He states it worsens when his legs are hanging down and improves some when he elevates them. The swelling started about a week after he left the hospital for an episode of pneumonia. He states his legs occasionally swell, especially when he eats too much salt, and the last time it happened was about 8 months ago. He reports taking a water pill for a while but not lately. He noted that he feels like he has put on a few pounds this week and feels a bit more tired and short of breath. He has had to sleep propped up with two pillows. He denies leg pain, fever, warmth, or trauma.
- Past medical history: anterior wall myocardial infarction 2 years ago; hypertension; heart failure with reduced ejection fraction; dyslipidemia
- Social history: one pack a day smoker for 30 years; quit 2 years ago
- Medications: sacubitril/valsartan; metoprolol; rosuvastatin; aspirin (which he forgets to take)
- Physical examination: temperature 98.5°F, pulse 70 beats/minute, respirations 22 breaths/minute, blood pressure 150/80 mmHg; pulse oximeter 96%; weight increase of 5 pounds in 1 month; cardiovascular exam remarkable for an S3 gallop; lungs with bibasilar fine inspiratory crackles; bilateral lower extremities pretibial to feet with 2+ pitting edema and mild pain when depressing skin
Mr. Smith is exhibiting signs of systemic fluid overload as a result of his heart failure. Disorders such as heart and renal failure that cause sodium and water retention resulting in volume increases that the body is unable to accommodate will lead to increased venous pressure and edema. Although the sodium is retained, the sodium plasma levels may actually be low (dilutional hyponatremia), as there is a proportionate amount of water retained. Venous pressure can also increase when the fluid return system is affected, which occurs with cardiac pump failure.
There is no data inconsistent with the diagnosis; the data that supports systemic fluid volume overload include weight gain, S3 gallop (created during early diastole/rapid ventricular filling phase and when there is increase fluid in ventricle and additional fluid flows in), bibasilar fine crackles, and bilateral lower extremity dependent edema.
Because he already has a diagnosis of heart failure, and this is an exacerbation, it must be determined if he is stable or unstable. If he is unstable and/or unable to care for himself, he needs to be hospitalized. If he is stable and has support or can care for himself, then he could be managed on an outpatient basis with close follow-up. The treatment for this type of fluid overload is diuresis, usually with a loop diuretic; reducing sodium intake; and possibly reducing fluid intake. He should continue to weigh himself daily.
Case 5: Mr. Evans, a 40-year-old man, is complaining of right leg swelling, pain, erythema, and warmth for the past 2 days. The swelling started after he accidentally cut the front of his leg with a pocket knife while fishing.
- Past medical history: hypertension
- Medications: amlodipine
- Social history: drinks four to five beers on the weekends and has smoked one or two cigarettes a day for the last 15 years (he states he is trying to quit)
- Physical examination: temperature 100°F, pulse 88 beats/minute, respirations 18 breaths/minute, blood pressure 140/92 mmHg; exam unremarkable except for edematous anterior right leg with open linear wound approximately 1-inch long; wound with scant purulent drainage; area warm and tender with blanching erythema that extends 3 inches around the wound
Mr. Jason’s edema is a result of cellulitis that has developed after cutting the front of his leg. Edema in this circumstance as a result of acute inflammatory response with increased capillary permeability, leading to fluid shifts.
There is no inconsistent data. All data points to edema because of the cellulitis. The edema is unilateral and located over the area of injury.
No diagnostic tests are necessary to determine the cause of edema. Treatment will include leg elevation, rest, and administration of antibiotics.
Case 1: A 16-year-old girl with type 1 diabetes mellitus who takes insulin several time a day becomes markedly confused, and a friend calls 911. Her friend states that they have been camping, and she thinks her friend was not using her insulin regularly like she has seen her do before. In the emergency department, she is tachypneic, breathing deeply at a rate of 24 breaths/minute. She is normotensive, but her heart rate is elevated at 112 beats/minute. On examination, she is oriented only to her name and is delirious. A fruity breath odor is noted. Serum chemistries reveal a glucose level of 500 mg/dL, potassium of 3.7 mEq/dL, and sodium of 132 mEq/L. Her serum osmolality is 298. Urine dipstick is grossly positive for ketones. It is determined that she is in diabetic ketoacidosis due to inadequate insulin use.
Questions:
- What factors would cause her to have a fluid volume deficit?
- What are potential electrolyte imbalances that may be noted given her hyperglycemia?
Glucose normally has a minor contribution to osmotic pressure in comparison to sodium. Glucose, like sodium, is an effective osmole because it does not freely cross the cell membrane and needs to be transported by insulin. Thus, excess glucose (hyperglycemia) in the extracellular fluid, specifically intravascular fluid, increases osmotic pressure and hypertonicity, causing water to be drawn out of the intracellular fluid (cells). The cells become dehydrated. The kidneys compensate by eliminating excess glucose and water, causing osmotic diuresis. Potassium follows glucose out of the cell, with resulting hyperkalemia (in the intravascular compartment). However, other electrolytes, such as sodium, become diluted due to excess water. For every 100 mg/dL of serum glucose above normal (100 mg/dL), sodium decreases about 1.6 mEq/L. As an example, if the serum sodium is 125 mEq/L and the serum glucose is 300 mg/dL, then the corrected sodium would be 125 + (1.6 mEq/L 3 2) = 128.2 mEq/L. Hyperglycemia can cause a fluid deficit due to water being pulled out of the cell and compensatory diuresis.
What is the most abundant intracellular cation?
Potassium
Colloid osmotic pressure is created mainly by
Albumin
electrolyte response to alkalosis
When experiencing alkalosis, the primary electrolyte response is typically a decrease in chloride ions (Cl-) alongside a potential drop in potassium levels, leading to a condition known as “hypokalemic hypochloremia” - meaning low potassium and low chloride in the blood; this is most commonly observed in metabolic alkalosis
electrolyte response to acidosis
In response to acidosis, the primary electrolyte change observed is a decrease in serum bicarbonate (HCO3-) levels, often accompanied by a shift of potassium ions from intracellular to extracellular spaces, leading to potential hyperkalemia; this means that acidosis typically causes a decrease in bicarbonate and can lead to increased potassium levels in the blood
