Fluids, Electrolytes, and Acid-Base Balance

Question 1

A 35-year-old man sustains crush injuries to both legs and presents to the Emergency Department with serum potassium of 7 mEq/L. Describe the approach to this patient.

Answer 1

• ATLS. Watch for acute compartment syndrome (If compartment pressure w/in 30 mmHg of diastolic - dx) and take to OR
• hyperK emergency: vitals, UOP q1h, EKG q2h, BMP q2h
  
  • calcium gluconate 1g over 2-3 mins; continuous telemetry
  • reg insulin 10-20 units in d10 500ml over 60 mins; q1h glucometer x6 hrs
  • lasix 40 mg IV q12h; if euvolemic, replace fluid w/ NS
  • hemodialysis if renal fct impaired

Question 2

What are the criteria for hyperkalemic emergency?

Answer 2

• clinical: muscle weakness, paralysis
• cardiac conduction abnormalities, arrhythmias
• K > 6.5
• K > 5.5 w/ renal impairment, K source (GI bleed, rhabdo, trauma)

Question 3

What EKG changes are associated w/ hyperK?

Answer 3

peaked T, wide QRS

Question 4

A 65-year-old man on chronic loop diuretic therapy presents with muscle cramps. His serum potassium is 2.0 mEq/L. Describe how to approach this patient.

Answer 4

• severe hypokalemia
• EKG and telemetry; BMP
• DC loop lasix for spironolactone
• 40 mEq IV K q4h, 40 mEQ PO K q6h
• check serum K q2h

Question 5

Most common causes of hypokalemia

Answer 5

GI or GU losses: vomiting, diarrhea, diuresis

Question 6

What kind of EKG changes can hypokalemia produce?

Answer 6

depression of the ST segment, decrease in the amplitude of the T wave, and an increase in the amplitude of U waves which occur at the end of the T wave

any arrhythmia

Question 7

A 45-year-old woman undergoes total thyroidectomy and becomes acutely hypoparathyroid. Describe the presentation of this patient.

Answer 7

• tetany - perioral numbness, paresthesias, muscle cramps
• severe sx - laryngospasm, seizure
• Trousseau’s - carpopedal spasm w/ BP cuff
• Chvostek’s - facial twitch w/ facial nerve tap (anterior to ear)
• chronic - basal ganglia calcifications, cataracts, dental abnormalities, and ectodermal manifestations

Question 8

A 45-year-old woman undergoes total thyroidectomy and becomes acutely hypoparathyroid. Describe the management of this patient.

Answer 8

• Acute hypoparathyroidism — symptomatic postsurgical hypoparathyroidism are initially treated with IV calcium + PO calcitriol
• IV calcium therapy if acute decrease in serum corrected calcium to ≤7.5 mg/dL (1.9 mmol/L), even if asymptomatic
• Oral calcium should be initiated as soon the patient is able to take supplements orally, in order to facilitate weaning of intravenous calcium.
• Severe symptoms or acute decrease to ≤7.5 mg/dL – Patients with acute hypoparathyroidism may have a rapid decline in serum calcium and PTH, precipitating severe symptoms. Emergency therapy is indicated in patients with tetany, seizures, or markedly prolonged QT intervals on electrocardiogram and also in patients with an acute decrease in serum corrected calcium to ≤7.5 mg/dL (1.9 mmol/L), even if they are asymptomatic.
• Treatment in adults is initiated with the intravenous administration of one 10 mL ampule of 10 percent calcium gluconate (90 mg of elemental calcium per 10 mL) in 50 mL of 5 percent dextrose infused over 10 to 20 minutes, followed by an intravenous infusion of calcium gluconate. (See “Treatment of hypocalcemia”, section on ‘Intravenous calcium’.)
• Oral calcitriol (0.5 mcg two times daily) and calcium (1 to 4 g of elemental calcium carbonate daily in divided doses) should be initiated as soon as possible (ie, when the patient is able to take oral supplements). When the serum calcium is in a safe range (>7.5 mg/dL [1.9 mmol/L]) and the patient is asymptomatic, intravenous calcium is gradually weaned.
• Acute management in children is with intravenous administration of calcium gluconate (90 mg elemental calcium/10 mL vial) at a slow rate (not greater than 2 mL [1.86 mg of elemental calcium]/kg over 10 minutes) while closely monitoring pulse rate (and the QT interval).
• Mild to moderate symptoms – For adults with milder degrees of symptoms (eg, paresthesias) and hypocalcemia (corrected serum calcium >7.5 mg/dL [1.9 mmol/L]), initial treatment with oral calcium and vitamin D supplementation is sufficient (table 3). The initial dose in adults is 1 to 4 g of elemental calcium carbonate in divided doses along with calcitriol 0.5 mcg twice daily. If symptoms do not improve with oral calcium, intravenous calcium infusion is required.
• For children with milder degrees of symptoms of hypocalcemia in the postoperative period, initial treatment is with intravenous calcium gluconate (10 mL = 90 mg elemental calcium in 100 mL) infused at a rate sufficient to maintain calcium levels in the asymptomatic, low-normal range. Oral calcium citrate or calcium glubionate (25 to 50 mg/kg elemental calcium daily in divided doses) and calcitriol (infants 0.04 to 0.08 mcg/kg daily, children >1 year 0.25 mcg daily) are also initiated. When the serum calcium is normal and the child is asymptomatic, the intravenous calcium is gradually weaned.
• Postsurgical hypoparathyroidism may be transient, resolving within three to six weeks but occasionally only after a year [19]. Because it may be transient, calcium and vitamin D supplements should be tapered slowly three to six weeks after surgery. Most patients are able to discontinue supplements entirely. Patients with a recurrence of hypocalcemia during the taper are more likely to have permanent hypoparathyroidism and should remain on oral supplementation.

Question 9

EKG in hypocalcemia

Answer 9

prolonged QT

Question 10

A 65-year-old man sustains a traumatic brain injury and 3 days later is found to have serum sodium of 165 mEq/L. Describe the approach to this patient.

Answer 10

• ddx: central and peripheral diabetes insipidus, salt overload
• urine and plasma osm
• FWD
• tx w/ free water and desmopressin

Question 11

A 65-year-old man presents with nausea, anorexia, and obtundation. Imaging reveals a cerebral tumor and routine laboratory tests show a sodium level of 120 mEq/L. Describe how to approach this patient.

Answer 11

• plasma osmolal gap, urine osmolality
• fluid restriction
• be aware of rapid correction causing myelinolysis

Question 12

A 45-year-old woman has undergone loop jejunostomy for malignant obstruction and has copious output. She presents with tachycardia, muscle fasciculation, and weakness. Describe the approach to this patient.

Answer 12

• Describe and perform a complete history and physical examination, with special attention to orthostatic vital signs, carpopedal spasm, and urine output.
• Identify both fluid volume and electrolyte disturbances.
• Determine the appropriate lab tests (electrolytes, EKG, corrected calcium).
• Guide therapy with fluid, magnesium, potassium, and phosphate.

Question 13

A 67-year-old woman with a history of chronic renal insufficiency develops peptic ulcer disease and has been using an over-the-counter antacid. She presents with muscle flaccidity and a depressed level of consciousness. Describe the approach to this patient.

Answer 13

• Describe and perform a complete history and physical examination, with special attention to orthostatic vital signs, deep tendon reflexes, and urine output.
• Identify both fluid volume and electrolyte disturbances.
• Determine the appropriate lab tests (electrolytes, EKG, corrected calcium).
• Guide therapy with fluid, calcium, diuretics, and dialysis.

Question 14

A 17-year-old woman with a history of anorexia and laxative abuse is admitted for severe dehydration and malnutrition. After 3 days of hyperalimentation, she presents with confusion and convulsions. Describe the approach to this patient.

Answer 14

• Describe and perform a complete history and physical examination, with special attention to orthostatic vital signs, deep tendon reflexes, and clinical signs of hypocalcemia.
• Identify both fluid volume and electrolyte disturbances.
• Recognize refeeding as the cause of the decompensation.
• Guide therapy with fluid, calcium, phosphate, and thiamine.