Electrolyte changes should not necessitate a change in the TPN order. Unusually large amounts of electrolytes should be added to a separate IVF and infused separately to avoid wasting a 24 hour TPN solution. Call the pharmacy (6848) regarding compatibility for any additives not listed on the order form.

1. Sodium - (60-150 meq/day). Hyponatremia is usually dilutional due to fluid overload or SIADH.

2. Potassium - (60-180 meq/day). Refractory hypokalemia may be due to low magnesium or phosphate. Use acetate salts in presence of metabolic acidosis as 1 meq of sodium or potassium acetate is equal to 1 meq of sodium bicarbonate.

The choice of chloride versus the acetate salt depends on the patient's acid-base status. Remember acetate is converted to bicarbonate in the body on a 1:1 ratio.

3. Chloride - (60-150 meq/day). Acidosis is common when all electrolytes are given as chloride. Usually give only enough chloride to match sodium. If patient is alkalotic, give chloride to match sodium and most potassium. Use more chloride in metabolic alkalosis resulting from potassium deficiency, loss of gastric contents from vomiting, or nasogastric suction.

4. Acetate - Use more acetate when patients have excessive bicarbonate loss as in proximal renal tubular acidosis, massive diarrhea, small bowel and pancreatic fistulas, and administration of acetazolamide. Also use in patients with renal failure, distal renal tubular acidosis, and those receiving amphotericin B and potassium-sparing diuretics who have a decrease chloride need since hydrogen excretion is decreased.

Pharmacy will use acetate to balance cations in TPN gopher system.

Acetate to balance = ( meq Na + meq K) - (meq Cl + meq PO₄)

Be sure to increase the milliequivalents of chloride ordered when patients are alkalotic and receiving amphoterecin or other drugs which require high amounts of potassium.

5. Phosphorus - (15-45 mM/day). 1 mM of phosphate supplies 1.33 meq Na or 1.47 meq K. Hypophosphatemia can occur in patients with chronic weight loss, alcohol abuse, and chronic antacid or diuretic therapy, especially during the first week of TPN therapy. Tissue rebuilding and large glucose loads shift phosphate, potassium, and magnesium to intracellular space. Referred to as refeeding syndrome. Symptoms include paresthesias, cardiac block, confusion, weakness, hypertension, and cardiac arrhythmias.

6. Calcium - (9-13.5 meq/day). Calcium levels must be interpreted with respect to the serum albumin as 40-50% of total serum calcium is bound to albumin. Serum albumin does not affect the free unbound calcium which is the active form. To determine the actual value of the bound calcium, ther serum calcium level obtained must be corrected by increasing the serum calcium level 0.8 mg/dL for each 1 g/dl decrease in serum albumin below normal (4 g/dl).

7. Magnesium - (8-24 meq/day). Uncorrected magnesium deficiency impairs repletion of cellular potassium and may also be the cause of persistent hypocalcemia (especially in Crohn's patients with short bowel syndrome). May occur in patients with CHF, digitalis toxicity, cisplatin therapy and in patients receiving potent loop diuretics. Serum magnesium may not reflect intracellular Mg stores. If serum magnesium is normal in a patient with suspected low magnesium, consider obtaining a 24 hour urine for magnesium. If excreting less than half of the adminstered amount of Mg, the patient is Mg deficient. If normal, the patient will excrete >60% of the administered amount of magnesium.

8. Heparin - (1 unit/ml). Used especially in central line TPN to prevent venous thrombosis.

Adult patients should routinely receive 10 ml/day of MVI-12.

Vitamin K (aquamephyton) should be given as 10 mg IM or SQ weekly to patients not taking any food by mouth.

Patients with large GI losses (diarrhea, drainage) are prone to zinc deficiency and may require more than recommended.

 

 

1. H2 antagonists - Ranitidine can be added to TPN and when needed, it is recommended to add to TPN instead of hanging another 24 hour IVF.

2. Albumin will NOT be added to TPN as a protein source. It also has the potential to increase microbial growth of fungi and bacteria in 24 hr TPN.

3. Call pharmacy regarding compatibility for additives not listed in the gopher system.