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 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 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 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 mOsm/L…. Plasma osmolality vasopressin thirst Salt intake

Blood pressure/effective ECF vasopressin Symphathetic nervous system Atrial naturietic factor Renin-angiotensin thirst 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= 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

SIADHCSWDI central Post resus diuresis Body water Increaseddecreased Normal or increased Sodium low highnormal Serum osm <280mOsm/Ldecreased>300mOsm/LNormal ( mOsm/L) Urine osm >500mOsm/Lincreaseddecreasedvariable Urine to serum osm ratio >1 <1.5variable Urine output lowhigh Urine sodium increased decreasedvariable

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 shift Alkalosis, 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

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 homeostasis HormoneCalciumPhosphate PTH IncreaseKidney reabsoption of Ca decreasedDecreased absorption in kidney Vitamin D IncreaseIncreased absorption in kidney and intestine increasedIncreased absorption in kidney and intestine Calcitonin DecreaseDecreased 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 mg/kg IV Calcium chloride 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 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 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!