Renal, Electrolyte, and Acid Base Disturbances



Renal, Electrolyte, and Acid Base Disturbances













TABLE 5.1. Hypernatremia
























Therapy Dosage Comments
5% dextrose in water (D5W) or 0.45% NaCl By calculation: see comment Free water replacement is based on formula for calculating water deficit:
Water deficit (L) = normal total body water – estimated total body water
Water deficit = (0.5 × body weight [kg]) – [(0.5 × body weight [kg]) × (140/actual serum Na+)]
Replace half of water deficit in the first 24 h and the remainder over the following 2–3 d
Monitor serum Na+ q1–2h to ensure gradual correction
Correcting too rapidly may produce cerebral edema, seizures, and death
Desmopressin (DDAVP) Intranasal: 0.1–0.4 ml (10–40 μg) qd Can be administered as a single daily dose or divided into 2 doses
  SC/IV: 0.5–1 ml (2.0–4.0 μg) qd When switching from the intranasal to IV route, the comparable antidiuretic dose is approximately 1/10 of the intranasal dose
Vasopressin SC/IM: 5–10 U bid-tid Low cost; however, complications include hypertension and sterile abscesses
IV administration not usually recommended
IM, intramuscular; IV, intravenous; SC, subcutaneous

  • Homeostasis of extracellular fluid is more dominant mechanism than maintenance of osmolality. Hypernatremia may be associated with low, normal, or excessive body water.
  • If thirst mechanism is intact, vasopressin replacement is a matter of convenience.
  • Excessive or rapid correction is particularly dangerous if hypernatremia has persisted for more than 24 hours because there is increased central nervous system intracellular osmolality. In this setting, secondary cerebral edema may produce seizures or death.









TABLE 5.2. Hyponatremia
































Therapy Dosage Comments
Furosemide 20–200 mg IV q4–6h Treatment usually required if serum sodium <110 mEq/L or patient is symptomatic
    Aim to bring serum sodium up to 120–125 mEq/L, but raise no more than 12 mEq/L in the first 24 h
0.9% NaCl (154 mEq Na+/L) By calculation (see comment) Calculation: Na+ deficit (mEq) = 0.60 × lean body wt (kg) × (120 – measured Na+)
3% NaCl (513 mEq Na+/L) By calculation (see comment above) Only for severe neurologic derangements or seizures
Administer very cautiously as overly rapid correction can cause CNS toxicity (central pontine myelinolysis) or volume overload
Demeclocycline 300 mg PO q12h For patients with SIADH
    Antagonizes ADH action in the distal nephron
ADH, antidiuretic hormone; CNS, central nervous system; PO, by mouth; SIADH, syndrome of inappropriate antidiuretic hormone release

  • Important to exclude “spurious” hyponatremia caused by hyperglycemia. This occurs because the osmotically active solute, glucose, causes a shift of water from the intracellular compart- ment to the extracellular compartment and dilutes extracellular sodium. For every 62 mg/dl rise in glucose, there is a 1 mEq/L fall in sodium.
  • The rate of correction of hyponatremia should be proportional to its rate of occurrence. Acute correction of hyponatremia should not exceed a 20 mEq/L rise in concentration of serum sodium in the first 48 hours of therapy.
  • Osmolality (mOsm/kg) = 2(Na+ + K+) + (BUN/2.8) + (glucose/18).









TABLE 5.3. Hyperkalemia











































Therapy Dosage Onset/Duration Comments
Acute Management
Sodium bicarbonate (NaHCO3) 1 mEq/kg IV over 3–5 min Onset: 15–30 minDuration: 1–2 h Can cause sodium overload and hyperosmolality
Calcium gluconate 10% (100 mg/ml = 9 mg/ml elemental Ca+2, 0.46 mEq/ml) 5–10 ml IV over 2–5 min Onset: 1–5 min
Duration: 1–2 h		 Rapid onset, but short-lived
Not compatible with NaHCO3; must flush line between infusions
Can augment digoxin toxicity
Calcium chloride 10% (100 mg/ml = 27.2 mg/ml elemental Ca+2, 1.36 mEq/ml) 5–10 ml IV over 2–5 min Onset: 1–5 min
Duration: 1–2 h		 Rapid onset, but short-lived
Not compatible with NaHCO3; must flush line between infusions
Can augment digoxin toxicity
Preferred preparation when volume is an issue because it contains more elemental calcium per g than calcium gluconate
Dextrose and insulin Dextrose 0.5 g/kg with 0.3 U regular insulin per g dextrose Onset: 10–15 min
Duration: 3 h		 Usual dosing is 25 g dextrose with 6–10 U regular insulin
Insulin should be given IV to avoid delayed hypoglycemia that can follow SC insulin; important to administer glucose concurrently
Albuterol 10–20 mg via nebulized aerosol Onset: 30 min
Duration: 2 h		 Mechanism is intracellular shunting of potassium by β 2-adrenergic agonists
Beware of possible angina
Subacute and Chronic Management
Sodium polystyrene sulfonate (SPS) PO: 15–60 g in 100–200 ml 20% sorbitol q4h
PR: 50 g in 50 ml 70% sorbitol added to 100–200 ml water		 Onset:
PO: 2 h
PR: 1 h
Duration: 4 h		 Resin exchanges sodium for potassium in the gut
PO SPS removes 1 mEq KCl/g, PR SPS removes 0.5 mEq KCl/g
Be aware of sodium load in patients with heart failure
IV, intravenous; PO, by mouth; PR, per rectum; SC, subcutaneous
If conservative methods of therapy fail, up to 50 mEq/h of potassium can be removed by hemodialysis. Peritoneal dialysis removes approximately 10 mEq/h.









TABLE 5.4. Hypokalemia
















Therapy Dosage Comments
Potassium chloride (KCl) See sliding scale for IV infusion (Table 5.5)
Maximum infusion rate of 40 mEq/h IV through a central line with continuous cardiac monitoring
Solutions should be prepared in non-dextrose containing fluids (i.e., NS or 0.45% NaCl)		 Life-threatening hypokalemia usually is caused by gastrointestinal losses (diarrhea) or genitourinary losses (diuretics)
Magnitude of deficit can only be approximated
Loss of 200–400 mEq of potassium lowers plasma potassium by 1 mEq/L
Clinical manifestations are rare when potassium level is ≥2.5 mEq/L, the exception being patients with cardiac disease
The most serious complications are conduction disturbances and arrhythmias; muscle weakness can occur
Cautious replacement in oliguric or anuric patients
Peripheral IV administration can be painful; pain is less if solutions contain less than 60 mEq KCl/L
Rapid IV replacement (greater than 20 mEq/h) warrants continuous cardiac monitoring
Check magnesium and supplement if below lower limit of normal
Potassium citrate and citric acid 40–60 mEq PO bid to qid Solution of 1,100 mg potassium citrate and 334 mg citric acid monohydrate per 5 ml; equivalent to 2 mEq potassium and 2 mEq bicarbonate per ml
Dose may be adjusted based on urine pH
Useful in renal tubular acidosis, when replacement of both potassium and bicarbonate is required
Aggressive treatment of acidosis with bicarbonate alone may aggravate coexisting hypokalemia
NS, normal saline (0.9%); NaCl, sodium chloride.
Potassium sparing diuretics may be considered in patients with severe renal losses of potassium; however, they should not be used in patients with renal insufficiency or in conjunction with aggressive potassium supplementation.









TABLE 5.5. Sliding Scale Algorithm for Potassium Chloride (KCl) Infusion






















K+ (mEq/L) KCl Infusion Rate (mEq/h)
<2.5 20–40
2.5–3.0 15–20
3.1–3.5 10
3.6–4.0 5
>4.1 —
Potassium level should be checked frequently—i.e., every 4 to 6 hours, during IV infusion.
Patients receiving ≥15 mEq/h should have cardiac monitoring. Doses ≥15 mEq/h should ideally be delivered via central vein because of pain with peripheral administration. (Maximum recommended concentration is 0.4 mEq/ml of solution.)









TABLE 5.6. Hypercalcemia





















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Jun 16, 2016 | Posted by in CRITICAL CARE | Comments Off on Renal, Electrolyte, and Acid Base Disturbances

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Therapy Dosage Comments
0.9% NaCl 250–500 ml/h With or without furosemide 20 mg IV q4–6h
Volume expansion in patients with normal renal function leads to urinary calcium losses
Calcium loss up to 2 g/24 h
Need to monitor magnesium, phosphorus, and potassium
Calcitonin-salmon Initial: 4 IU/kg SC/IM q12h
Repeat: 8 IU/kg SC/IM q12h		 Perform skin test for allergy before first dose in patients with suspected sensitivity to calcitonin-salmon
Decreases bone reabsorption, but effect is limited and diminishes after several days
Maximum dose 8 IU/kg q6h if no response to lower doses
May be added to bisphosphonate to achieve normal calcium levels within a few days
Zoledronic acid 4 mg IV as a single dose over at least 15 min Minimum time period for retreatment is 7 d
Pamidronate disodium 60 mg (for moderate hypercalcemia) or 90 mg (for severe hypercalcemia) as a single IV infusion (diluted in 1 L 0.9% NaCl or D5W) over 24 h