Hypo/HyperPHOSPHATEMIA

normal range for phosphorus

2.7-4.5 mg/dL

how is phosphorus absorbed?

from the gut, regulated by vitamin D

How is phosphorus eliminated?

kidneys

what indirectly regulates phosphorus

PTH (has a ‘sensor’ for calcium and phosporus)

what can cause acute hyperphosphatemia

kidneys are unable to excrete the excess phosphate, ingestion of phosphates e.g. fleet enema (2021 FDA warning for at risk patients such as patients with kidney dysfunction)

is hyperphosphatemia typically chronic or acute

chronic

what lab values indicate mild-moderate hypophosphatemia?

serum phosphate 1.5-2.7 mg/dL

what lab values indicate severe hypophosphatemia?

serum phosphate < 1.5 mg/dL

what can cause hypophosphatemia

decreased gut absorption, intracellular distribution (ECF —→ ICF), loss via the kidneys, sometimes loops/thiazides

complications of hypophosphatemia:

seizures, coma, rhabdomyolysis, poor diaphragm function with resulting hypoventilation (phosphate affects all cells/organs)

examples of oral phosphorus products indicated for mild-moderate (asymptomatic) hypophosphatemia:

Phos-NaK and K-Phos Neutral

what is the target phosphorus doses (oral)?

1-2 grams/day divided (single doses can cause diarrhea)

what units are oral phosphorus products dosed in?

mg

what units are IV phosphorus products dosed in?

mmols

phosphate content in Phos-NaK

250 mg (8mmol)

potassium content in Phos-NaK

280 mg (7.1 mEq)

sodium content in Phos-NaK

160 mg (6.9 mEq)

phosphate content in K-Phos Neutral

250 mg (8 mmol)

potassium content in K-Phos Neutral

45 mg (1.1 mEq)

sodium content in K-Phos Neutral

298 mg (12 mEq)

which oral phosphorous product is typically given to CKD or patients at high risk of hyperkalemia?

K-Phos Neutral due to the lower potassium content

ADRs of oral phosphorus products

osmotic diarrhea

what phosphate products are given IV?

sodium phosphate (1 mmol = 1.3 mEq sodium) and potassium phosphate (1 mmol = 1.5 mEq potassium)

dosing of IV phosphate products

0.32 - 0.64 mmol/kg per dose (up to 1mmol/kg in ICU)

infusion rate for IV phosphate products

infuse over 4-6 hours (faster for central line)

why are central lines encouraged for phosphate administration instead of peripheral IVs

phosphate products are vessicants

what are the risks associated with IV phosphate products?

vesication - causes significant tissue damage (blistering and irritation) if the product extravasates from the vein, particularly when infused too quickly or in peripheral veins

what is Meaney’s usually IV dose of phosphate?

10-30 mmols

when should you give IV phosphate supplementation

severe (< 1.5 mg/dL) or symptomatic hypophosphatemia

when should you give a 50% lower dose of phosphate supplementation and closely monitor serum phosphorus?

if patient has kidney dysfunction

T/F: extracellular phosphorus is not a good marker of total body content and repeated laboratory monitoring is important

True <3