5 Written Questions
5 Matching Questions
- What are s/sx of hyperphosphatemia....and what is the most significant effect of hyperphosphatemia??
- What are normal intracellular & extracellular K+ concentrations??
- The normal ranges for:
pH (7.35-7.45), PaCO2 (35-45 mmHg), & HCO3- (22-27 mE/L).
What is the normal HCO3- / H2CO3 ratio??....and what is its significance??
- What hormone regulates osmolality??....what hormone regulates Na+??
- What is the most common electrolyte disturbance in the hospitalized patient??
- a HYPONATREMIA, according to Barash, but Miller states that it is the 3rd most common, behind hypomagnesemia (25%) and hypokalemia (10%).
Hyponatremia occurs when Na+ concentration is <135 mEq/L.
- b Manifestations of hyperphosphatemia are r/t the associated hypocalcemia.
There is increased excitability of nerves (the threshold potential moves toward the resting potential) associated with hypocalcemia, which results in paresthesia (tingling of lips and fingers)....laryngeal stridor (laryngospasm)...carpo-pedal spasm (Trousseau's sign)....masseter muscle spasm (Chvostek's sign)....and SZs.
Prolongation of QT interval may/may not be seen.
Severe hyperphosphatemia causes hypocalcemia....with hyperphosphatemia, calcium phosphate deposits in bone and soft tissue, thereby lowering plasma Ca++ concentrations.
- c The normal HCO3-/ H2CO3 ratio is 20:1.....when the ratio is normal (20:1), then the pH is 7.40. The pH increases when the ratio increases, and pH falls when the ratio decreases.
- d ADH (vasopressin) regulates osmolality....and since the concentration of Na+ salts is 90% of ECF osmolality, regulating Na+ concentration is essentially equivalent to regulating osmolality.....therefore, ADH regulates Na+ concentration.
NOTE:....Aldosterone regulates the 'amount', NOT 'concentration' of Na+....thus, Aldosterone regulates volume.
- e Intracellular K+ is 150 mEq/L & extracellular K+ is ~4.2 mEq/L (ranges 3.8-5.0).....with a ratio of intracellular to extracellular K+ of about 30:1.
Hypokalemia is present when serum K+ is <3.5 mEq/L...and hyperkalemia is present when the serum K+ is >5.0 mEq/L.
5 Multiple Choice Questions
- Alkalosis, Insulin (stimulates the Na+/K+ pump), and Beta-2 Agonists (stimulates the Na+/K+ pumps) will all drive K+ into cells, thus decreasing the extracellular/serum concentration.
**The FASTEST way to correct hyperkalemia is by using SODIUM BICARBONATE (0.5-1.0 mEq/L IV) which drives K+ into cells in ~5 minutes.
**Glucose/Insulin will promote a 'sustained' transfer of K+ into cells, decreasing the serum K+ by 1.5-2.5 mEq/L in ~30-60 minutes....dextrose is given with the insulin to prevent hypoglycemia that would otherwise occur.
**Beta-2 agonists will decrease serum K+ by 1 mEq/L within 30 minutes, with effects lasting up to 2 hours.
**Calcium exerts its effects in 1-2 minutes, BUT it does NOT correct hyperkalemia....it only stabilizes cardiac membrane excitability....thus, Calcium Gluconate 10% (5-10mL) or Calcium Chloride 10% (3-5 mL) is best when there are EKG changes, such as widened QRS and peaked T waves, but underlying hyperkalemia must be treated b/c effects of Ca++ are short-lived (15-20 minutes).....BUT USE CAUTION in patients taking Digoxin, since Ca++ potentiates digoxin toxicity.
- Common causes of metabolic acidosis...
2. Lactic acidosis
3. Renal failure
4. Toxic dose of Salicylates (e.g. ASA)
Common causes of metabolic alkalosis...
2. NG Suctioning
3. Hypokalemia from diuretics
- Hypernatremia usually reflects dehydration, not an excess of total body Na+.....in hyperosmolar state (hypernatremia), ADH output increases, urinary loss of water is decreased, and water is conserved. In addition, thirst mechanisms are activated, and water is ingested....thus restoring an iso-osmotic state.
- The passage of water from a less concentrated solution (e.g. pure water) to a more concentrated solution (e.g. salt water) when the 2 solutions are separated by a semipermeable membrane.
- Chvostek's sign is a contracture of the facial muscle produced by tapping on the facial nerve as it passes through the parotid gland.....it occurs (facial twitching) when there is hypocalcemia.
5 True/False Questions
Na+ salts represent 90% of all electrolytes in the ECF. What 2 physiologic factors regulate Na+ concentrations?? → HYPONATREMIA, according to Barash, but Miller states that it is the 3rd most common, behind hypomagnesemia (25%) and hypokalemia (10%).
Hyponatremia occurs when Na+ concentration is <135 mEq/L.
What are 4 reasons for keeping the patient's pH between 7.35-7.45 when the patient is on a ventilator?? → Normal pH....
1. Insures proper distribution of electrolytes
2. Maintains optimal function of enzymes
3. Optimizes myocardial contractility
4. Maintains optimal saturation of Hgb
How is a hypo-osmotic (hyponatremic) state corrected physiologically? → In a hypo-osmolar state, (hyponatremia) ADH production is reduced, and large volumes of dilute urine are formed. Plasma osmolarity, and hence Na+ concentration, are thereby rsetored to normal.
What is metabolic acidosis and metabolic alkalosis?? → Respiratory Acidosis....when there is decreased elimination of CO2 by the lungs resulting in elevated PaCO2 and low pH....thus increasing alveolar ventilation & eliminating the precipitating factor will help treat this.
Respiratory Alkalosis....when there is excessive elimination of CO2 by the lungs resulting in decreased PaCO2 and increased pH.....when "alveolar ventilation exceeds CO2 production"...(hyperventilation)....thus, slow the respiratory rate.
Why shouldn't PRBCs be reconstituted in LR??? → The Ca++ in LR may reverse the anti-coagulant effect of the Citrate Preservative (Citrate is a preservative used to provide anticoagulation so that PRBCs may be stored...it is responsible for lowering serum Ca++ b/c it binds to free serum Ca++ in the blood when given to a patient, hence, explaining why Ca++ should be supplemented during multi-transfusions).