Hyponatremia is a condition in which the _____ is hyperosmolar relative to the _____.
What is the most common cause of hyponatremia?
Excess total body water
NOT deficiency of sodium
What is the most important regulator of sodium?
What types of patient will hyponatremia be seen?
CHF, cirrhosis, drug, water intoxication
What is an important adverse effect of hyponatremia?
Signs and symptoms of hyponatremia
HTN, Bradycardia, confusion, agitation, headache, seizures, N/V, muscle cramps, weakness
Rapid treatment of chronic hyponatremia can result in ____________.
Myelinolysis (dissolving of myelin sheaths around nerves)
Who is are greatest risk for myelinolysis?
Hyponatremic >48 hours, lives transplant, etoh
What should be used to increase sodium levels and at what rate?
Infuse 3% saline at 1-2 ml/kg/hr and sodium level should be increased by no more than 1-2 meq/L/hr
If patient is clinically stable, sodium administration should not exceed 10-15 mmol/L in 24 hours
What sodium level is generally considered safe for patient undergoing general anesthesia?
Intraoperative cerebral edema caused by hyponatremia can be manifested by what signs?
Decrease in MAC, postop agitation/confusion/somnolence
What is the most common cause of hypernatremia with a normal total body sodium content?
Rapid hypernatremia results in shrinking of the brain and increased traction on intracranial veins/sinuses which can ultimately lead to what?
Rapid correction of hypernatremia can lead to what?
Signs and symptoms of hypernatremia
Lethargy, mental status changes, peripheral edema, muscular rigidity and tremor, expanded intravascular volume
How do you correct hypernatremia?
If a patient has acute hypernatremia, what type of solution can be given rapidly?
If a patient has chronic hypernatremia accompanied by volume depletion, correct first with what? Followed by what?
Isotonic crystalloids followed by hypotonic solutions
At what rate should the sodium level be lowered in hypernatremia?
Hypernatremia increases or decreases the MAC for inhalation in animal studies?
At what sodium level should elective surgery be postponed?
What is responsible for the resting membrane potential of the cell?
Causes of hypokalemia
GI loss, renal loss, poor K intake, redistribution of K from ECF to ICF, diuretics, beta adrenergic stimulation, insulin, alkalosis (low PCO2, albuterol inhalers), PCN, aminoglycides, corticosteriods, hyperaldosterone, gastric suctioning, anorexia, alcoholism
Surgical stress may decrease serum K by how much?
Signs and Symptoms of Hypokalemia
ST depression, widened QRS, flattened T waves, ectopy, weakness, confusion
Hypokalemic patients on digoxin are at an increased or decreased risk for dig toxicity?
Intraoperative management of a patient with hypokalemia
1. Administer IV K if arrhythmias develop
2. Avoid hyperventilation
3. Avoid use of glucose in solutions
4. Be aware of increased sensitivity to NMBA's
Causes of hyperkalemia
Acidosis, hemolysis, tissue necrosis, rhabdomyolysis, renal failure, potassium sparing diuretics, hypoaldosteronism, NSAIDS, beta-blockers, ACE inhibitors
Movement of K out of the cells can be seen in what instances?
Administration of sux, acidosis, cell lysis following chemotherapy, hemolysis, rhabdomyolysis, massive tissue trauma, hyperosmolality, digitalis overdose, administration of arginine hyperchloride and beta-2 adrenergic blockade, and during episodes of hyperkalemic periodic paralysis
Average increase in plasma K when sux is administered?
0.5 meq/L (can be exaggerated following large burns or severe muscle trauma and in patient with muscle denervation/paralysis)
Signs and symptoms of hyperkalemia
Tall peaked T waves, widened QRS, ventricular arrhythmias, cardiac arrest, muscle weakness, confusion, parathesias
What is the lethal level regarding hyperkalemia?
Treatment of Hyperkalemia
1. CALCIUM: 5-10mL of 10% calcium gluconate or 3-5 mL of 10% calcium chloride (partially antagonizes the cardiac effects of hyperkalemia--short lived dig toxicity potentiation
2. BICARB: promotes cellular uptake of K
3. BETA-AGONIST: promote cellular uptake
4. IV GLUCOSE AND INSULIN: 30-50g glucose with 10 units of insulin (promotes cellular uptake of K and lowering plasma K but often takes up to 1 hour for peak effect)
Intraoperative management of a patient with hyperkalemia
1. Watch for arrhythmias
2. Sux and LR (2 meq K) are contraindicated
3. Avoid acidosis (may mildly hyperventilate)
4. Be aware hyperkalemia can accentuate the effects of NMDAs
Ionized Ca accounts for what percentage of Ca in the ECF? Where is the remainder?
50%, 10% bound to anions, 40% bound to albumin
Total serum level are largely dependent on what levels?
Causes of hypocalcemia
Hypoparathyroid (may be surgically induced), pancreatitis, malignancy, alkalosis, rhabdomyolysis, renal insufficiency, hypomagnsemia, low albumin due to malnutrition/sepsis/burns, extensive blood transfusions