Fluid, Electrolytes
Fluid distribution
TBW- 0.60 of wgt.. . of this:
0.67 intracellular (40% T wgt)
0.33 extracellular (20% wgtl)
0.25 vascular (5% wgt)
0.75 interstitial (15% wgt)
HYPERCALCEMIA
Causes: primary hyperparathyroidism
malignancy (PTH-related peptide, ectopic production of 1,25-dihydroxyvitamin D, osteoclast-activating factor, lytic bone mets
non parathyroid endocrine disorder
thyrotoxicosis, pheochromocytoma, adrenal insufficiency, VIP-producing tumor
granulomatous disease (1,25-dihydroxyvitamin D excess)
sarcoidosis, tuberculosis, histoplasmosis, coccidiomycosis, leprosy
medications (thiazide diuretics, lithium, estrogens, antiestrogens)
milk-alkali syndrome
vitamin A or D intoxication
familial hypocalciuric hypercalcemia
immobilization
parenteral nutrition
acute and chronic renal failure
Signs: "Stones, moans, groans, with psychic overtones"
Renal: polyuria (nephrogenic DI), nephrolithiasis, renal failure, ectopic calcification
GI: anorexia, nausea, vomiting, constipation
Neuro: weakness, fatigue, confusion, stupor, coma
ECG: Shortened QT
Treatment: Correct dehydration, increase renal calcium excretion, decrease bone resorption, and treat the underlying disorder.
1. IV hydration, 2.5-4 liters NS per day; watch for CHF
2. IV furosemide after volume repleted; keep I=O
3. Specific treatment in approximate desirability of use:
• calcitonin 4U/kg sq bid to 8 U/kg sq qid-rapid acting; often see rebound once it wears off.
• pamidronate 15-45 mg IV slowly qd x 6 days or as single IV infusion of 90 mg over 24 hours. Effective. Treatment of choice in hypercalcemia of malignancy.
• etidronate 7.5 mg/kg over 4 hours qd x 3-7 days. Slower acting, may be more effective.
• plicamycin (mithramycin-chemo agent) 25 mcg/kg over 4-6 h q1-2 days. Be careful in renal or hepatic failure
• gallium nitrate 200 mg/m2 body surface area in one liter IV fluid per day for 5 days. Nephrotoxic, but effective.
• glucocorticoids 200-300 mg hydrocortisone IV qd x 3-5 days.
HYPERKALEMIA
Causes: spurious due to hemolysis during phlebotomy, greatly increased platelets or WBC
ingestion
renal failure
acidosis, including RTA type IV
iatrogenic
retroperitoneal hematoma
cell death (rhabdomyolysis, burns, tumor lysis)
adrenal insufficiency or other hypomineralocorticoid state
drugs (spironolactone, ACE inhibitor, digitalis overdose)
ECG: tall peaked T waves (K>5.5)
PR prolongation followed by loss of P waves (K>6.5)
QRS widening (K>7.0)
Treatment: 1 amp CaCl2 or Ca gluconate to counter arrhythmias
2 amps bicarb w/ 2 amps D50 plus 10 units regular insulin IV. This will cause temporary cellular shifts only.
NS at 200 cc/hr with furosemide
Kayexelate 50 g po or retention enema
dialysis (last resort)
HYPERMAGNESEMIA
Causes: Renal failure
Overaggressive replacement.
Signs: Rarely symptomatic until Mg >4 mEq/l. Areflexia, lethargy, weakness, paralysis, respiratory failure, hypotension, bradycardia, heart block, asystole
Treatment: Asymptomatic: hold magnesium supplementation
Symptomatic: 1 amp Ca gluconate IV over 10 minutes to antagonize Mg. Support ventilation and heart rate if necessary. Definitive therapy requires dialysis if no renal function, or Ca gluconate infusion to promote Mg excretion.
HYPERNATREMIA
Diagnosis-first assess volume status. This helps to determine underlying cause.
I. Hypovolemia-usually from Na (and hence H2O) losses with H2O losses predominating
A. Urine Na >20 meq/L reflects renal losses from diuretics, glycosuria, mannitol, renal failure, etc. Urine volume also tends to be high with high osmolality.
B. Urine Na <10 meq/L reflects extrarenal losses (sweat, GI, insensible). Urine volume is low with high osmolality.
II. Isovolemia-reflects loss of free water.
A. Diabetes insipidus-if DI is present, urine volume will be high but osmolality will be low. Consider testing by water deprivation; if patient does not appropriately concentrate urine, consider DI. If DDAVP causes subsequent increase in urine concentrating ability, DI is confirmed.
1. Central-CNS trauma, basilar meningitis, pituitary/hypothalamic damage (tumor, fungus, TB, abscess, granuloma, Sheehan's, surgery, irradiation), idiopathic
2. Nephrogenic-severe hypokalemia, hypercalcemia, CRI, medullary/interstitial kidney disease, Li, demeclocycline, amphotericin, propoxyphene, methoxyflurane
B. Mild extrarenal losses-skin & respiratory insensible losses
III. Hypervolemia-usually from net Na gain.
A. Iatrogenic-IVF with hypertonic saline or NaHCO3, NaCl tablets, hypertonic IVF (e.g. cryoprecipitate with Nacitrate anticoagulant), dialysis with hypertonic solutions
B. Mineralocorticoid excess-primary hyperaldosteronism, Cushing's disease, congenital adrenal hyperplasia
Treatment depends on underlying volume status
I. Hypovolemia-replace volume with NS until hemodynamically stable, then use 1/2NS. To determine rate of replacement, calculate H20 deficit = 0.6(weight in kg)(serum Na - 140)/140. Replace 1/2 deficit over first 24 hours and remainder over next 1-2 days.
II. Isovolemia-calculate water deficit as above and replete with free water.
III. Hypervolemia-diurese and replace volume with free water.
HYPERPHOSPHATEMIA
Causes: Renal failure
Tumor lysis
Hypoparathyroidism/pseudohypoparathyroidism
Acidosis
Overzealous PO4 replacement
Signs: Hypocalcemia, ectopic calcifications if Ca x PO4 product >70
Treatment: Calcium salts are preferable
CaCO3 (OsCal) 1-2 tab po tid (comes in 500 and 650 mg tablets)
Ca acetate (PhosLo) 1-2 tab po tid (comes in 667 mg tablets)
Aluminum hydroxide (AmphoGel) 600 mg po tid may be used if Ca is already high, but risk aluminum toxicity with long-term use
Alternatives: saline diuresis if no renal failure, dialysis
HYPOCALCEMIA
if low, make sure to correct for
low albumin (see formula section) or measure ionized Ca. Note alkalosis augments Ca binding to albumin and increases severity of symptoms.
Causes: renal failure
critically ill patients
hypoparathyroidism or pseudohypoparathyroidism (PTH resistance)
severe hypomagnesemia or hypermagnesemia
acute pancreatitis
rhabdomyolysis
tumor lysis syndrome
vitamin D deficiency
post transfusion
Signs: paresthesias, tetany (especially carpopedal spasm), lethargy, confusion, seizures
Trousseau's sign, Chvostek's sign, QT prolongation
Treatment: Symptomatic hypocalcemia should be corrected by replacement with calcium gluconate IV (1 amp = 10 cc of 10% Ca gluconate = 90 mg Ca). Start with 2 amps IV over 10 minutes.
If present, low Mg should also be corrected because it contributes to low Ca.
HYPOKALEMIA
Causes: inadequate intake
GI loss (vomiting, diarrhea, laxative abuse, fistula)
drugs (diuretics, insulin, gentamicin, amphotericin, carbenicillin)
excess mineralocorticoids (Cushing's, hyperaldosteronism, hyperreninemia)
congenital (Bartter, Liddle)
RTA types I, II
metabolic alkalosis
acute hyperventilation
DKA
ECG: T wave flattening ± inversion, U waves, arrhythmias (e.g. PSVT, Afib, etc.), and ST changes, pseudo-prolonged QT.
Treatment: Check creatinine first!
Supplement to keep 4.0 or greater except in patients with renal insufficiency who are almost always not supplemented.
Serum potassium rises 0.1 for every 10 meq of supplementation.
In the units, you may write a sliding scale if creatinine is stable and <1.3. Intravenous potassium replacement should be given no faster than 10 mEq per hour by peripheral IV or 20 mEq per hour by central line.
Serum K mEQ K
PO/IV
3.8-3.9 20
3.6-3.7 40
3.4-3.5 60
3.2-3.3 80
3.0-3.1 100
<3.0 120 & call HO
HYPOMAGNESEMIA
Causes: Decreased intake or absorption (malnutrition, malabsorption, diarrhea, NG aspiration)
Increased excretion (hypercalcemia, osmotic diuresis, hyperparathyroidism)
Drugs (loop diuretics, aminoglycosides, amphotericin, cisplatin, cyclosporine, alcohol, pentamidine)
Signs: lethargy, confusion, tremor, fasciculations, ataxia, nystagmus, tetany, seizures
hypokalemia, hypocalcemia
PR and QT prolongation
Treatment: supplement to keep 2.0 or greater except in renal failure patients. Oral preparations differ from one hospital to another. Note that oral preparations cause diarrhea in larger doses.
Hospital
Moffitt
Mag complex
300 mg elemental Mg
1-2 tab qd
VA
Mag oxide
420 mg (240 mg elemental Mg)
1-2 tab qd
SFGH
Mag gluconate
500 mg (27 mg elemental Mg)
1-2 tab qd
For parenteral therapy, MgSO4 for IV comes in amps, 1 amp = 1 gram (8 mEq). You may write a sliding scale in the units.
Serum Mg MGSO4 IV
1.8-1.9 2
1.6-1.7 3
1.4-1.5 4
1.2-1.3 5
<1.2 6 & call HO
HYPONATREMIA
def:<135mEq/L
<120-mental status changes
<110-seizures, coma, needs
immediate Tx.
Na deficit: (140-[Na])xTBW.
(TBW=60% wt. in kg)
Just follow the following algorithm:
I. Assess serum osmolality
A. Normal (280-295)-isoosmotic hyponatremia (pseudohyponatremia)
1. Hyperproteinemia
2. Hyperlipidemia
B. Elevated (>295)-hypertonic hyponatremia.
1. Hyperglycemia (no osmolar gap)
2. Hypertonic infusions (mannitol, glycine)
C. Low (<280)-hypotonic hyponatremia. Proceed to step II below
II. Assess volume status and urine sodium
A. Hypovolemic-total body depletion of Na disproportionately to water losses
1. Urine Na >20-renal loss (osmotic diuresis, salt-losing nephropathy, diuretic, proximal RTA, adrenal insufficiency, vomiting with bicarbonaturia and obligate Na loss,
cerebral sodium- wasting syndrome).
2. Urine Na <20-extrarenal loss (vomiting, diarrhea, third-spacing)
B. Hypervolemic-retention of free water
1. Urine Na >20-renal failure
2. Urine Na <20-nephrotic syndrome, CHF, cirrhosis
C. Euvolemic-a mixed bag
1. Urine Na >20-renal failure, SIADH, hypothyroidism, pain/emotional stress, various drugs (amitriptyline, carbamazepine, clofibrate, Cytoxan, morphine, vincristine), selective glucocorticoid deficiency.
2. Urine Na <20-water intoxication.
3. Beer Potomania
4. Endurance exercise
Alternative approach:
compare Uosm/Posm
if >1.2, then high SIADH state
FeNa: low: nephrotic synd, chf,dehydr
high: cri, adrenal insuff, SIADH
III. Treatment-depends on situation. If symptomatic, remember to correct slowly with max daily change 20 meq/l to avoid central pontine myelinolysis. If asymptomatic, can correct even more slowly than that.
A. Hypovolemic-correct underlying disorder and replete volume with NS.
B. Hypervolemic-salt and water restriction; treat underlying disorder.
C. Euvolemic-salt and water restriction; treat underlying disorder. For severe, symptomatic hyponatremia (Na <110-115) may wish to correct with IV furosemide and replacement of electrolyte losses.
HYPOPHOSPHATEMIA
Causes: Decreased intake
Vitamin D deficiency, malabsorption, vomiting, steatorrhea, phosphate binders
alcohol abuse/withdrawal
Shifts from serum into cells
respiratory alkalosis, sepsis, hepatic coma, salicylate poisoning, gout, severe burns
recovery from hypothermia, refeeding after malnutrition
hyperalimentation
recovery of DKA, effects of insulin/glucagon/androgens
Increased urinary secretion
hyperparathyroidism
renal tubular defects (aldosteronism, SIADH, steroids, diuretics)
hypomagnesemia
Signs: Generally seen only with total body depletion and serum PO4 <1 mg/dl.
Weakness, rhabdomyolysis, respiratory compromise/failure, CHF
Paresthesias, dysarthria, confusion, stupor, seizures, coma
Hemolysis, platelet dysfunction, metabolic acidosis
Therapy: • Generally you only need to keep PO4 over 1 mg/dl. Above that, oral replacement is preferable to avoid hyperphosphatemia. The exception tends to be ICU patients on a ventilator who may need to have phosphate repletion to optimize weaning.
• When replacing PO4, follow K and Mg because patients are frequently low in these electrolytes as well.
• Follow Ca when replacing PO4 because overshooting and causing hyperPO4 can cause hypocalcemia as well as ectopic calcifications, renal failure, or hypotension if the calcium/phosphate product goes above 70.
IV preparations:
Typical replacement is 8-15 mmol or 0.08-0.16 mmol/kg over 6 hrs; you can give more (up to 0.6 mmol/kg) for severe hypophosphatemia. Use either sodium phosphate or potassium phosphate depending on whether patient also needs K.
Sodium phosphate has 3 mmol/cc = 93 mg PO4/cc with 4 meq Na/cc.
Potassium phosphate has 3 mmol/cc = 93 mg PO4/cc with 4 mEq K/cc.
PO preparations:
Typical dose 0.5-1 gm elemental PO4 bid-tid. Use NeutraPhos or K-Phos depending on whether patient also needs K.
NeutraPhos has 250 mg (8 mmol) PO4, 6-13 meq Na, and 1-7 meq K per tablet
K-Phos has 125 mg (4 mmol) PO4 and 4-14 meq K per tablet.
Pedialyte (total 100 cal\L)
NaCl 45meq/L
K 20 meq/L
Cl 35 meq/L
Citrate 28.4 meq/L
Dextrose 20g/L
Fructose 5g/L
Potassium replacement: (KCI)
defecitranges 200 - 400\1meq/L
IV: (5.0-measured K) x 20.
PO: (5.0-measured K) x 30.
or:
2 mEQ IV for each 0.1 < 5.0
3 mEQ PO for each 0.1 < 5.0
Renal Formulas:
1. Creatinine Clearance
=(140-age)(wt. in kg)/
72 X serum [Cr]
2. Fractional Excretion of Sodium
- FENa
< 1 Pre-renal
> 1 Intra-renal
=(urine [Na+] X serum [Cr])/
(serum [Na+] X urine [Cr])
3. Anion Gap
[Na+] - ( [Cl-] + [HCO3-])
8-12 mEq/L
4. Serum Osmolality
= 2 X [Na+] + [glucose]/18 +
[BUN]/2.8
- normal 285 - 295 mOsm/L
5. Water Deficit (liters)
=0.6 X (wt. in kg) X ([Na+] -140)/140
6. Corrected [Ca+2]
- if albumin decreased by 1 gm/dL,
decrease [Ca+2] by 0.8 mg/dL
7. Colloid Osmotic Pressure
= 1.4 [globulin] + 5.5 [albumin]
= 24 +/- 3 mm Hg
Urine
AG: Na+K-Cl
used to estimate [NH4] in hypchloremic met acidosis
- if Cl is < than Na,K, then there is an RTA with distal acidification defect and inadequate NH4 excretion in the urine.
- if CL >> than Na, K, then there is appropriate NH4 excretion and possible bicarb loss from GI sources1>10>
Dostları ilə paylaş: |