Parenteral nutrition energy support titration
- Titrate PN support to enteral advancement as dictated per primary team.
- For patients with no anticipated advancements in enteral feeds, consider serial physiological advancements in PN to maintain normal growth/development.
- If weight/height increased greater than anticipated by velocity or change in Z-scores for 2 consecutive visits or >2 months, wean by 5-20%, typically 10%.
- If weight/height decreased less than anticipated by velocity or change in Z-scores for 2 consecutive visits or >2 months, increase by 5-20%, typically 10%.
- Otherwise no PN changes.
Characterics of different standard intravenous fluids
|
|
pH |
Na+ |
K |
Cl- |
Ca++ |
Lactate |
Osmolarity (mOsmol/L) |
Kcal/L |
|
Normal saline |
5.5 (4.5 to 7) |
154 |
- |
154 |
- |
- |
308 |
0 |
|
½ normal saline |
5.5 (4.5 to 7) |
77 |
- |
77 |
- |
- |
154 |
0 |
|
D10% ½ normal saline |
4.3 (3.5 to 6.5) |
77 |
- |
77 |
- |
- |
660
|
340 |
|
D5% ½ normal saline |
4 (3.2 to 6.5) |
77 |
- |
77 |
- |
- |
406 |
170 |
|
D5% Lactated ringes |
4.6 (4.0 to 6.0) |
130 |
4 |
112 |
3 |
28 |
530 |
170 |
|
Lactated ringers |
6.5 (6 to 7.5) |
130 |
4 |
109 |
3 |
28 |
273 |
0 |
Social Media
From Boston Children's Hospital's HPN Facebook Group on February 2, 2017: https://www.facebook.com/groups/HPNBostonChildrens/permalink/620456148159701:
"Check hydration on HPN by:- Changes in weight (increase/decrease)
- Changes in urination (amount/color)
- Changes in heart rate (increase/decrease)
- Urine tests: Urine specific gravity
- Blood tests: blood urea nitrogen (BUN), creatinine, CO2."
Sodium
- Requirement 2-4 mEq/kg/day
- Adult Daily Amount 1-2 mEq/kg/day
- Patients with increased sodium losses may have
- Urine sodium may be better assessment sodium status than serum sodium (normal >25[u1] )0
- Fractional excretion of sodium (FENA) to consider in case of dehydration
- Children w/ ileostomy are at increased risk of sodium deficiencyr6
1 tsp salt = 6 g salt ≈ 2,400 mg sodium = 104 mmol sodium = 104 mEq sodium
Potassium
- Requirement 1-3 meq/kg/day[u2]
- Urine potassium varies depending upon sodium, potassium and volume status
- Adult Daily Amount Requirement 1-2 mEq/kg/day
- Calculation of potassium infusion rate = K (mEq/L) x max infusion rate (ml/hour) / 1000/ patient weight (kg) = max K infusion rate (mEq/kg/h)
- FYI: max K infusion rate (BCH inpatient max without CVR monitor is 0.25mEq/kg/h):
- potassium phosphate: 1.47 x mMol of phos = mEq of K OR mEq of K/1.47 = mMol of phos
Potassium Phosphate 10 mmol = 15 mEq potassium
Calcium
Requirement: 0.5-2.5 mEq/kg/day (see RDA with enteral supplementation if needed)
Adult Daily Amount Requirement 10-15 mEq/kg/day
- Adjustment for hypoalbuminemia
(4-albumin) * 0.8 + serum calcium
Monitoring:
- Check serum calcium every 1-2 months or more frequently as needed.
- Monitor trend in phosphate.
- Monitor trends in urine calcium and creatinine levels.
- WARNING: Calcium level often elevated in dehydration.
Hypercalcemia
- Dehydration
- vitamin D toxicity
- parathyroid excess
- immobilization
- drugs
- osteolytic process (cancer) drugs
- endrocrine dysfunction
- Mild: often asymptomatic
- nausea
- vomiting
- loss of appetite
- constipation
- abdominal pain
- polydipsia
- fatigue
- lethargy
- muscle weakness
- joint pain
- confusion.
Hypocalcemia
Causes:
- Rare in pediatric HPN (consider lab artifact due to hypoalbuminemia)
- hypoparathyroidism
- magnesium depletion
- vitamin D deficiency
- hypophosphatemia
- hungry bone syndrome
- chelation
- acute pancreatitis
- medications
- cancer
Symptoms:
- Mild: often asymptomatic
Moderate-severe:
- seizures
- tetany
- refractory hypotension
- arrythmias
For IV calcium gluconate: 1 g calcium gluconate = elemental calcium 93 mg = calcium 4.65 mEq = calcium 2.33 mmol
Magnesium
- Requirement 0.25-0.5 meq/kg/day
Hypomagnesemia:
Symptoms:
- tiredness
- weakness
- muscle cramps
- arythemias
- tremors
- irritability
- paresthesias
- irritability
- seizures
- hypokalemia
- hypocalcemia 2/2 hypoparathyroidism
- metabolic bone disease
- tetany
- coma or death
Causes:
- insufficient intake
- kidney wasting
- medications (thiazide diuretics, PPI, tacrolimus, aminoglycoside)
- chronic alcoholism
- Inflammatory bowel disease
Hypermagnesemia:
Symptoms:
- hypotension
- respiratory depressin
- cardiac arrest (prolongation of PR interval, widening of QRS complex, increased T-wave amplitude)
- abscence of deep tendon reflexes.
Causes:
- Renal failure
Phosphate
- Requirement: 1-2 mmol/kg/day
Hypophosphatemia:
Symptoms:
- Weakness (worst-case scenario: diaphragmatic paralysis)
- mental status changes
- rhabdomyolysis
Causes:
- Refeeding
- inadequate intake
- respiratory alkalosis
- malabsorption,
- liver failure
- tumor induced osteomalacia
- hereditary causes
- alcohol abuse
Hyperphosphatemia:
Symptoms:
- Usually asymptomtic.
- Symptoms of hypocalcemia like tetany when calcium level drops simulaneously.
- Soft tissue calcifications.
Causes:
- chronic kidney disease,
- hypoparathyroidism,
- acidosis.
Conversion of of mmol into meq of phosphate for NaPhos and KPhos
- IV NaPhos: 1mMOl NaPhos = 1 mMol phos and 1.33 mEq of Na
- IV KPhos: 1 mMOl of KPhos = 1 mMol phos and 1.47 mEq of K
Clinic here for related Clinical Vignette
- High GI bicarbonate loss (normal anion gap or hyperchloraemic metabolic acidosis)
- D‐lactic metabolic acidosis (> 15 anion gap metabolic acidosis)
Bicarbonate
Interpretation of Stool Electrolytes4
|
Test |
Interpretation |
Notes |
|
Electrolytes (Na, K, Cl) Calculate Stool Osmotic Gap (SOG) 290-[ 2([Na]+[K])] |
· Secretory type diarrhea SOG · Osmotic type diarrhea SOG >75-100 · If SOG negative, suggests presence of additional anion like phosphate · If [Cl] as high or higher than [Na] suggestive of congenital chloride diarrhea |
Order as ‘electrolytes, fluid’ select ‘stool’ |
|
Magnesium |
· Obtain when unexplained osmotic type diarrhea. · >75 mEq/L suggests Mg containing substance |
Order as ‘magnesium, fluid’ select ‘other’ and in comments write ‘stool’ |
|
Osmolality |
· Should be close to serum osmolality · If substantially less than serum, suggests contamination with water or urine |
Order as ‘osmolality, fluid’ select ‘stool’; send on ice |
Compiled by Daniel Kamin
Interpretation of Urine Electrolytes
|
Test |
Interpretation |
Notes |
|
Sodium
FENa = UNa + PCr x100 PNa + UCr |
· Amount of excreted sodium is determined by RAAS and intake; · Urine Na concentration will depend on water reabsorption; FENa+ corrects for water reabsorption · If suspect intravascular volume contraction but clinical data unclear, FENa · FENa inaccurate when patients are on IV fluids Or diuretics · If clinical euvolemia but urine Na+ is
|
Order as ‘Electrolytes, urine’ which gets you Na, K, and Cl; order ‘Creatinine, urine spot’; Also order Chem 7 on same day |
|
Potassium
Transtubular K gradient (TTKG) Uk + Posm Pk + Uosm
|
· Concentration depends on water content of urine, which depends on volume status · TTKG corrects for water reabsorption · TTKG is indirect measure of K secretion in the distal nephron · TTKG depends on dietary K and the activity of aldosterone · >10 suggests hyperaldosterone state, as in hypovolemia · TTKG not important when serum potassium is normal—used to characterize normal or abnormal kidney response in states of hyper and hypokalemia
|
Order as ‘Electrolytes, urine’ which gets you Na, K, and Cl; order ‘Creatinine, urine spot’; Also order Chem 7 on same day
|
|
Hypokalemia |
Appropriate TTKG |
|
|
Hyperkalemia |
· TTKG should be high, indicating appropriate kidney response · consider decreased GFR, acid/base disturbance, insulin deficiency as cause in this case · If it is abnormally low say 2-5, the kidney is not excreting K appropriately. Sometimes this is due to insufficient urine sodium. Urine sodium needs to be over 40 (ideally) to allow distal secretion of K. |
|
|
Chloride |
· Differential diagnosis of metabolic alkalosis · Urine chloride is low in patients with metabolic alkalosis when it is due to vomiting, NG suction (loss of HCl), or chronic diuretic use leading to chloride depletion, laxative abuse, CF, and congenital chloride diarrhea. Also in patients with certain salt-wasting disorders such as Bartter or Gitelman syndrome. · Urine chloride is usually NOT low (>40) in patients with metabolic alkalosis and volume expansion due to certain forms of monogenic hypertension, including primary aldosteronism, Liddle’s syndrome, excess licorice intake, and apparent mineralocorticoid excess. |
|
|
Specific gravity |
· Ratio of the weight of a solution to weight of water · Water = 1.000 · Range 1.001 – 1.035 · SG and Osm rise in parallel · Large molecules increase SG disproportionately (like contrast and proteins) · If s.g. >1.035, consider glucose, contrast exposure. |
|
|
Osmolality |
· Non-infant kidneys should be able to concentrate to 1200 and dilute to 50 mOsm/Kg · In setting of hyponatremia, urine osmolality can distinguish between SIADH (osmolality high) and excessive water ingestion (osmolality low) |
Order as ‘osmolality, urine’ |
- How much salts and fluids to prescribe.
- Whether you’re okay with higher amount of sugar in PN.
- Look for risk of kidney stones.
- Detect other kidney health issues, like urinary tract infect (UTI), protein/blood in urine, other things.
(Very important to find out whether you need to collect sample during or after HPN infusion.)"
