Electrolyte management in the PICU

2012

Goals

• To discuss the pathophysiology of electrolyte disturbances

• To review the acute management of electrolyte disturbances

• To discuss 2 cases with audience participation

Case 1

• 13 yo male admitted to the PICU after crashing into a wall during a motorcross competition.

• He is intubated with a current GCS of 6T and is receiving aggressive management for increased ICP’s.

• Review head CT on next slide• On hospital day 2, his urine output increases

to 10ml/kg/h.

Case 1

• HR 120 T 36 BP 110/62 98% on 50% FiO2

• CVP 2

• I/0 balance = -600

• What could be happening?

• What labs would you send?

Case 1

• Differential diagnosis:• Post resuscitation diuresis• Polyuric ATN• Hyperglycemia/post-mannitol • Central Diabetes Insipidus• Cerebral salt wasting

• Labs to send:• UA with spec grav• Urine osmolality, Urine sodium• Serum osmolality, Serum sodium• Basic metabolic panel

Case 1

• Na 158 K 4 BUN 25 Creat 0.7 Gluc 140• Sosm 340 Uosm= 121• UA sg 1.001 glucose negative• Una= 10• Sum it up:

• Hypernatremia + Hypovolemia + Increased DILUTE urine output

Case 1

• What other information would you want to know?

• Types/amounts of IVF received over the last 24 hours• Whether mannitol or diuretics were given

• What is the most likely diagnosis?• DI

• How would you manage this patient?• Resuscitate with NS if needed• Fluid replacement with 1/2 or 1/4 NS• Vasopressin infusion titrated to UOP 3-4ml/kg/h

Case 1

• Your management strategy is effective and the patient’s UOP slows to 3-4ml/kg/hr.

• On hospital day 4, previous therapies to adjust UOP have been discontinued.

• The UOP continues to slow to <1ml/kg/hr.

Case 1

• T 36 HR 89 BP 118/72 CVP 12• Na= 129, Serum Osm 277 BUN 10• UA 1.025 Uosm=550 Una= 75• Sum it up:

• Hyponatremia + euvolemia + low UOP that is CONCENTRATED

• What diagnoses would you consider?• SIADH, hythyroidism, glucocorticoid deficiency, psychogenic

polydipsia, iatrogenic free water exces

• How would you treat this?• Fluid restriction 30-50% maintenance• Avoid free water excess (use isotonic solutions)

Case 1

• On HD #6, despite fluid restriction and avoidance of excess free water, the sodium continues to trend down. UOP is 3-4ml/kg/hr.

• Serum Na= 125 • Repeat UA = sg 1.015 Una= 250• Sum it up:

• Hyponatremia + euvolemia + high normal UOP that has A LOT of SODIUM

• What could be happening? • Cerebral salt wasting

The body keeps your Posm between 280-290 mOsm/L….

Plasma osmolality

vasopressin thirst

Salt intake

Blood pressure/effective ECF

vasopressin

Symphathetic nervous system

Atrial naturietic factor

Renin-angiotensinthirst

Salt intake

Hyponatremia

Hyponatremia: Clinical signs and symptoms

• Nausea/vomiting• Lethargy• Headache• Confusion• Seizures• Non-cardiogenic pulmonary edema• These are mostly due to CNS dysfunction

and cerebral edema!

Hyponatremia: Causes

• Hypovolemia• Extra-renal sodium loss (Una<10)

» Sweat, diarrhea, vomiting» 3rd spacing: trauma, burns, pancreatitis

• Renal sodium loss (Una >20)» Diuretics» Mineralocorticoid deficiency» Cerebral salt wasting» Proximal type II RTA

• Euvolemia (Una>20)• SIADH• Glucocorticoid deficiency• Hypothryoidism• Psychogenic polydipsia• Drugs: desmopressin, psychoactive agents, chemotx

Hyponatremia: Causes

• Hypervolemia (Una<20)• Acute or chronic renal failure Una>20• Congestive heart failure• Cirrhosis/hepatic failure• Nephrotic syndrome

• Hyperosmolar• Hyperglycemia, mannitol, glycine

SIADH

• Causes• Intracranial pathology, mechanical ventilation, post-operative,

malignancy, neck surgery, pulmonary pathology

• Diagnosis• Patient should be euvolemic• Labs: Serum osm, Urine osm, Una• Urine will be inappropriately concentrated for a patient who is

hypoosmolar• Urine Na will be elevated and Urine output will be low

• Treatment• 3% NS• Fluid restriction to 30-50% maintenance• Avoid excess free water-->make sure to check drips!

Hyponatremia: Therapy

• Correct rapidly with 3% NS for severely symptomatic patients

• 4ml/kg 3%NS will increase [Na] by 5• Normalize sodium at a rate of 8-12 mEq/L

over 24 hours with 0.45% or 0.9% NS• Central pontine myelinolysis

• may be irreversible • dysarthria, dysphagia, spastic paresis, coma

• Check frequent sodiums (q1 or q2h)

3% NS

• Characteristics• 513 mEq/L• pH= 5.0• 1027 mosm/L

• Can be administered peripherally (in the acute setting) or centrally (recommended)

• 3-5 ml/kg will raise serum sodium by 4-6 mEq/L

• Adverse effects• Metabolic acidosis and hyperchloremia• Venous irritation/phlebitis

Hypernatremia

Hypernatremia: Clinical signs and symptoms

• Nausea/vomiting

• Restless, irritable, or lethargic

• Anorexia

• Stupor/coma

• Subarachnoid hemorrhage--Why?

Hypernatremia: Causes

• Free water loss• Diuretics (loop)• Post obstructive diuresis• Acute and chronic renal disease• Sweating, fistula, burns, diarrhea, vomiting• Diabetes insipidus (central, nephrogenic)

• Sodium gain• Hypertonic saline or sodium bicarbonate• TPN• Hyperaldosteronism• Cushing’s syndrome

Hypernatremia: Therapy

• Risk of seizures and cerebral edema if corrected too rapidly

• Correct hypovolemia with NS• Correct Na with 0.45% NS• Check Na frequently and adjust fluid therapy

for a goal of 0.5-1mEq/L decrease qhour• Urine replacement (0.22% or 0.45% NS)• Vasopressin for central DI

Diabetes insipidus (central)

• Causes• Surgical resection, trauma, tumor infiltration, genetic,

• Diagnosis• Rising Na and Serum osmolality• low Uosm and low Urine sg • increased UOP

• Treatment• Urine replacement with 1/2 or 1/4 NS• Vasopressin infusion: titrate to UOP 3-4ml/kg/h• Na checks every hour

SIADH CSW DI central Post resus

diuresis

Body water Increased decreased decreased Normal or increased

Sodium low low high normal

Serum osm <280mOsm/L decreased >300mOsm/L Normal (280-290mOsm/L)

Urine osm >500mOsm/L increased decreased variable

Urine to serum osm ratio

>1 >1 <1.5 variable

Urine output low high high high

Urine sodium increased increased decreased variable

Case 2

Case 2

• 15 yo male playing linebacker for high school football team presents in August with syncope, weakness, and palpitations. Bedside I-stat : 7.22/32/98/12/-9 Na 136 K 7 Gluc 189 iCa 0.7

• Cardiac monitors indicated the following:

Case 2

• What is this rhythm?

In case you were wondering, this is BAD!!!!

Case 2

• What electrolyte disturbances does this patient have?

• Hyperkalemia• Metabolic acidosis• Hypocalcemia

• What therapies would you initiate? • Calcium gluconate 100mg/kg• Sodium bicarbonate 1mEq/kg• Insulin 0.1 units/kg + D10 or D25 2ml/kg• Kayexalate PR

• What other lab studies are needed? • BMP, Mg, Phos, Lactate, CK, Tox screen, Serum osmolality

Case 2

• HR 130 RR 28 BP 90/50 98% on 2L

• Obese male, tachypneic, diaphoretic, able to talk, clear breath sounds, no murmur, thready pulses

• Na 137 K 7.5 HCO3 12 BUN 28 Creat 1.6 Gluc 190 Ca 6 Mg 1.1 Phos 6

• CK 45000

Case 2

• Despite initial therapies, patient remains hyperkalemic

• What would you do? • Continue to administer Na bicarb, insulin/glucose,

Calcium gluconate• Place a hemodialysis catheter• Keep a defibrillator and hands-free pads nearby

• What disease processes could cause this? • Acute renal failure• Tumor lysis syndrome• Rhabdomyolysis

Hypokalemia

Hypokalemia: Signs and symptoms

• Generalized muscle weakness• Paralytic ileus• Cardiac arrhythmias

• Atrial tachycardia• AV dissociation

• EKG changes• Flat/inverted T waves• ST segment depression• U waves

• Ascending paralysis and impaired respiratory function (K<2)

EKG in hypokalemia

Hypokalemia: Causes

• Renal loss– Primary hyperaldosteronism, hypothermia, genetic

syndromes (i.e. Liddle’s), type I and II RTA, drugs (I.e. amphotericin, foscarnet)

• GI loss– Vomiting, diarrhea (VIPoma, enteric fistula,

malabsorption, jejunoileal bypass)

• Transcellular shiftAlkalosis, beta agonists, caffeine, insulin,

thryrotoxicosis, hypokalemic periodic paralysis

Hypokalemia: treatment

• Determine the cause• When to correct?• How much?

– 0.5-1 mEq/kg over 1 hour

• What to use?– KCl po or IV– KPhos

Hyperkalemia

Hyperkalemia

• Definition: K>6 mEq/L

• Symptoms• EKG changes: peaked T waves, prolonged PR

interval, widened QRS, V-fib• Muscle weakness/paresthesias

Hyperkalemia: Causes

• Impaired excretion• Renal failure, mineralocorticoid deficiency, drugs, type IV

RTA,

• Iatrogenic • Transcellular shift

• Acidosis, beta blockers, digitalis overdose, somatostatin

• Other• Tumor lysis• rhabdomyolysis

Hyperkalemia: Treatment

• Calcium gluconate• 100mg/kg IV peripheral or central

• Insulin/glucose• Insulin 0.1units/kg IV • Glucose 2ml/kg D10 or D25• The most effective way to quickly lower K!!!

• Sodium bicarbonate• 1-2mEq/kg

• Hemodialysis• Kayexalate

• 1gram/kg po or PR

Ca, Mg, Phos

Calcium homeostasisHormone Calcium Phosphate

PTH Increase Kidney reabsoption of Ca

decreased Decreased absorption in kidney

Vitamin D Increase Increased absorption in kidney and intestine

increased Increased absorption in kidney and intestine

Calcitonin Decrease Decreased bone resorption/ decreased kidney reabsorption

No effect

Hypocalcemia

• Symptoms appear when iCa<0.7• Symptoms include:

• Neuromuscular irritability (tetany)• Paresthesias of hands/feet• Circumoral numbness• Laryngospasm or bronchospasm• Anxious/irritable/depressed/confused• Hypotension• Rickets

• EKG changes include:• Prolonged QT• Non-specific ST-Twave changes

Hypocalcemia: Causes and Diagnosis

• Determine the cause• PTH level• Vitamin D levels (25OHD3 and 1,25OHD3)• 24 hour urine calcium

• Hypoparathyroidism• Irradiation, surgery, hypomagnesemia, DiGeorge,

polyglandular autoimmune syndrome, storage disease, HIV

• Vitamin D deficiency• Malnutrition, malabsorption, hepatobiliary disease, low

sun exposure

Hypocalcemia: Causes

• Calcium chelation/precipitation• Tumor lysis, rhabdomyolysis, citrate, foscarnet

• Multifactorial• Sepsis, pancreatitis, burns

Hypocalcemia: Treatment

• Calcium gluconate• 25-100mg/kg IV

• Calcium chloride• 10-20 mg/kg IV• Must be given centrally

• Treat low Magnesium• Treat underlying disease• When should you avoid treating

hypocalcemia?• Tumor lysis syndrome (unless patient is symptomatic)

Hypomagnesemia: Symptoms

• Symptoms:• Refractory hypocalcemia• Diarrhea• Ventricular arrhythmias• Muscle weakness, tremors, tetany

• Causes• Decreased intake or malabsorption• Decreased renal reabsorption (familial, diuretics,

amphotericin, bartters’s, gitelman’s• Transcellular shift (hyperaldosteronism, pancreatitis,

respiratory alkalosis, catecholamines)

Hypomagnesemia

• Treatment• Magnesium sulfate 25-50 mg/kg• Replace potassium and calcium• Oral supplementation

Hypophosphatemia

• Symptoms• Muscle weakness, paralysis• Respiratory depression• Leukocyte and platelet dysfunction• Hemolysis

• Causes• Decreased intake or malabsorption• Decreased renal reabsorption (hyperparathyroidism,

fanconi’s, vitamin D deficiency, medications)• Transcellular shift (catecholamines, theophylline,

respiratory alkalosis)

Hypophosphatemia: Treatment

• Determine underlying cause (many times it is multifactorial)

• Replace using:• NaPhos• Kphos 0.08-0.32 mmol/kg over 4-6 hours

REVIEW QUESTIONS

What is the most effective way to lower serum K?

Insulin and glucose

How do you treat seizures due to hyponatremia?

3% NS 4ml/kg

Why does low magnesium often cause hypocalcemia?

Low magnesium inhibits PTH release

What electrolyte abnormality may lead to failed extubation

attempt?

hypophosphatemia

Thank you!