NMS. Surgery

5

Chapter 1 ♦ Principles of Surgical Physiology

IV. Maintenance IV: Table 1-3 gives electrolyte concentrations of several IV fluids. A. Minimal sodium maintenance would require 70–140 mEq/day. B. Minimal potassium requirements would be 35–70 mEq/day. Water and Electrolyte Deficits and Excesses I. Water A. Hypovolemia 2. Signs and symptoms of gradual volume loss: Loss of skin turgor, thirst, alterations in body temperature, and changes in mental status. 3. Treatment: Acute deficits should be replaced rapidly, whereas chronic deficits should be replaced slowly, with half of the deficit replaced over the first 8 hours and the rest in 24–48 hours. B. Hypervolemia: Well tolerated in healthy patients. 1. Signs and symptoms of acute hypervolemia: Acute shortness of breath, tachycardia. 2. Signs and symptoms of chronic hypervolemia: Peripheral edema, pulmonary edema. 3. Treatment: With normal kidneys, volume restriction and/or diuretics. For nonfunctioning kidneys, renal replacement therapy (hemodialysis). 1. Signs and symptoms of acute volume loss: Tachycardia, hypotension, and decreased urine output. a. Hyperosmolar: Hyperglycemia, mannitol infusion, or presence of other osmotically active particles that draw in water. b. Normo-osmolar (pseudohyponatremia): Hypertriglyceridemia, hyperlipidemia, and hyperproteinemia; large, minimally osmotic molecules displace water and interfere with the lab measurement. c. Hypo-osmolar (1) Hypovolemic: Renal losses, renal tubular acidosis, cerebral salt wasting, GI losses, “tea and toast syndrome”, transcutaneous losses (burns, trauma). (2) Hypervolemic: Related to low cardiac output (the kidneys have less blood flow, and free water is conserved) or hypoalbuminemia (e.g., cirrhosis) or other edematous states wherein salt and free water cannot be excreted by the kidneys (e.g., renal failure). (3) Euvolemic: Syndrome of inappropriate antidiuretic hormone (SIADH) secretion or other disorders (e.g., glucocorticoid deficiency, hypothyroidism, water intoxication from psychogenic polydipsia). II. Sodium: Close relationship to volume status. A. Hyponatremia (Na + <130 mEq/L): (Fig. 1-2) 1. Causes