Electrolyte & Metabolic Disturbance
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Transcript of Electrolyte & Metabolic Disturbance
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Management of Life-Threatening
Electrolyte and Metabolic
Disturbances
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Introduction
Common in critically ill & injured patients
Alter physiologic function & contribute tomorbidity & mortality
The most common electrolyte disturban-ce in critically ill patients are: disturbancein K, Na, Ca, Mg, P levels
Metabolic disturbance accompany manysystemic disease processes or result ofaltered endocrine function
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Electrolyte Disturbances
Potassium: hypo- & hyperkalemia
Sodium : hypo- & hypernatremia
Others:Calcium : hypo- & hypercalcemia
Phosphate : hypo- & hyperphosphatemia
Magnesium : hypomagnesemia
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Potassium
Essential for maintenance of the electricalmembrane potential
Alteration of K primarily effect the CV,
neuromuscular, and GI systems.
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Hypokalemia
Plasma [K+]
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Causes of hypokalemia
Transcellular Shifts Renal Losses Extrarenal
Losses
Decreased Intake
Alkalosis
Hyperventilation
Insulin
-adrenergic agonists
Hypomagnesemia
Vomiting
Diuresis
Metabolic alkalos
Renal tub defects
Diabetic ketoacid
Drugs (diuretics,aminoglycosides,
amphotericin B)
Diarrhea
Profuse sweating
Malnutrition
Alcoholism
Anorexia nervosa
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Clinical manifestation:
Cardiac system:
arrhythmias (ventricular, & supraventricular,
conduction delay, sinus bradycardia)ECG abnormalities (U waves, QT prolo-
ngation, flat or inverted T waves)
Neuromuscular system: muscle weakness
or paralysis, paresthesia, ileus, abdominalcramps, nausea, and vomiting
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Effect of hypokalemia
CardiovaskularECG changes/dysrhythmias
Myocardial dysfunction
Neuromuscular
Skeletal muscle weakness
Tetany
Rhabdomyolisis
Ileus
Renal
Polyuria (nephrogenic DI)
Increased ammonia production
Increased bicarbonate reabsorption
Hormonal
Decreased insulin secretionDecreased aldosteron secretion
Metabolic
Negative nitrogen balance
Encephalopaty in patients with liver disease
Adapted from Schrier RE,ed: Renal and Electrolyte Disorders, 3rd ed. Little, Brown andCompany, 1986.
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Treatment (1)
Stop offending drugs (if possible)
Correct hypomagnesemia & other
electrolyte disturbances
Correct alkalosis
Treatment is aimed:
Correcting the underlying cause
Administering potassium
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Treatment (2)
Arrhythmias or paralysis: KCl 20-30 mEq viacentral venous catheter (sequential infusion: 10
mEq in 100 mL fluid over 20 mins, infusion rate canbe slowed after symptoms resolve)
Absence of life-threatening manifestation: KCl 10mEq/hr IV
K
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Treatment (3)
Acidemia is present, correct the
potassium level before correcting pH (K
shift intracellularly as the pH increases)
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Monitoring
Continuous ECG monitoring is
necessary (during parenteral
administration of high concentration of
KCl)
Serum K levels must be monitored at
frequent interval during repletion (every
1-2 hrs during initial replacement)
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Hyperkalemia
Potassium >5.5 mEq/L (>5.5 mmol/L)
Most often results from renal dysfunction
Pseudohyperkalemia may result from awhite blood cell count >100,000/mm3 or
platelet count >600,000/mm3.
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Causes of hyperkalemia
Renal dysfunction
Acidemia
Hypoaldosteronism
Drugs (potassium-sparing diuretics,ACE inhibitors, etc.)
Excessive intake
Cell death
Rhabdomyolisis
Tumor lysis
Burns
Hemolysis
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Clinical manifestation
Heart:
arrhythmias (heart block, bradycardia, dimi-
nished conduction and contraction)
ECG abnormalities (diffuse peaked T waves,
PR prolongation, QRS widening, diminished P
waves, sine waves)
Muscle: muscle weakness, paralysis, pares-thesias, and hypoactive reflexes
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Treatment (1)
Recognition & treatment of underlying diseases
Removal of offending drugs
Limitation of potassium intake
Correction of acidemia or eletrolyte abnorma-lities
Any serum potassium level >6 mEq/L should beaddressed, but the urgency of treatment
depends on clinical manifestation The presence of ECG changes mandates
immediate therapy
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Treatment (2)
ECG abnormalities present: CaCl 5-10 mL of a 10%solution IV over 5-10 mins (the effect lasts only 30-60 mins &should be followed by additional treatment)
Redistribution of K: Na bicarbonate 1 mEq/kg (1 mmol/kg) IV over 5-10 mins
(beware of potential Na overload with Na bicarbonate) 50 g of 50% dextrose over 5-10 mins with 10 U of
regular insulin IV
Inhaled 2-agonists in high dose (albuterol 10-20 mg)
Removal of K from body: Increase urine output with a loop diuretic Increase GI K loss with Na polystyrene sulfonate 25-50 g
in sarbitol, enterally or by enema
Dialysis
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Monitoring
Should be monitored during
evaluation & treatment:Repeat serum K levels Continuous cardiac monitoring
and serial ECG tracings
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Sodium
Primary functions:
determinant of osmolality in the body involved in the regulation of extracellular
volume
Abnormalities in circulating Na primarily
effect neuronal & neuromuscular function.
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Hyponatremia
Sodium 135 mmol/L)
Most common cause: associated with a low serumosmolality is excess secretion of ADH (euvolemichyponatremia) or associated with hypovolemic andhypervolemic conditions
The presence of a nonsodium solute: glucose andmannitol (characterized by an elevated serumosmolality
Pseudohyponatremia: occurs in the presence ofsevere hyperlipidemia, hyperproteinemia, orhyperglycemia
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Causes of hyponatremia
Euvolemia Hypovolemia Hypervolemia
SIADH
Psychogenic polydipsiaHypothyroidism
Inappropriate water admi-
nistration to infanst/chil-
dren
Diuretic use
Aldosterone deficiencyRenal tubular dysfunction
Vomiting
Diarrhea
Third-space fluid losses
CHF
CirrhosisNephrosis
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Clinical manifestation
CNS: disorientation, decreased mentation,
irritability, seizures, lethargy, coma,
nausea and vomiting
Muscle: weakness & CNS-driven
respiratory arrest
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Algorithm for treatment of hyponatremia
hyponatremia
water & Na+ loss water loss increased Na+ content
replace isotonic loss replace water deficit loop diuretic
replace water deficit replace any water deficit
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Treatment (1)
Treating the underlying disease
Removing offending drugs
Improving the circulating Na level Hypovolemic hyponatremia: usually responds to IV
volume repletion (with normal saline). Volume is
replaced, ADH is suppressed & free water is
excreted by the kidneys.
Hypervolemic hyponatremia: usually not severe &
improves with successful treatment of the
underlying condition
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Treatment (2)
Hyponatremia is acute or symptomatic:serum Na level should be increasedrestricting free-water intake
increasing free-water clearence with loop
diuretics
replacing IV volume with normal saline
(154 mEq/L) or hypertonic 3% saline (513
mEq/L) The goal of therapy: to remove free water
& not Na
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Hypernatremia
Sodium 145 mmol/L)
Indicates intracellular volume depletion
with a loss of free water, which exceedsNa loss
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Causes of hypernatremia
Water Loss Reduced Water
Intake
Excessive Sodium
Intake
Diarrhea
Vomiting
Excessive sweating
Diuresis
Diabetes insipidus
Altered thirst
Impaired access
Salt tablets
Hypertonic saline
Sodium bicarbonate
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Clinical manifestation
CNS: altered mentation, lethargy,
seizures, coma
Muscle function: muscle weakness
Polyuria: the presence of diabetes
insipidus or excess salt and water intake
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Treatment (1)
Centers on correcting the underlying cause
of hypernatremia
The vast majority of patients require free-
water repletion
The water deficit can be calculated using
equation:
water deficit (L)=0.6 x wt (kg) [(Na2/Na1)-1]Na1 = the normal sodium level
Na2 = the measured sodium level
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METABOLIC DISTURBANCES
Acute Adrenal Insufficiency
Hyperglycemic Syndromes
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Acute Adrenal Insufficiency
Lack of specific signs & symptoms makesearly recognition of acute renal insufficiencydifficult
May result from:
Failure of the adrenal glands (autoimmunedisease, granulomatous disease, HIV
infection, adrenal hemorrhage, meningococ-
cemia, ketoconazole)
Failure of the hypothalamic/pituitary axis
(withdrawal from glucocorticoid therapy)
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Clinical manifestation
Weakness Nausea/vomiting Abdominal pain Orthostatic hypotension Hypotension refractory to volume or
vasopressor agents Fever
Suggestive laboratory findings: Hyponatremia Hyperkalemia Acidosis Hypoglycemia Prerenal azotemia
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Emergent treatment
Indicated in critically ill patients, even if thediagnosis is not established
High-risk patients include: AIDS, disseminatedtuberculosis, sepsis, acute anticoagulation,
post CABG patients, patients from whomglucocorticoid therapy was withdrawn withinthe past 12 months
If dexamethasone is used for emergent steroidreplacement, a short adrenocorticotropichormone stimulation test can be performed fordiagnosis after resuscitative therapy isinstituted
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Short ACTH Stimulating Test
Blood for serum cortisol is drawn at baseline Synthetic 1-24 ACTH (cortrosyn, cosyntropin), 250 ug,
is administered intravenously
A serum cortisol level is drawn 60 mins aftercosyntropin administration
A cortisol level >20 ug/dL (>552 nmol/L) at 60 minsindicates adequate adrenal function
Failure to attain adequate cortisol levels indicates theneed for further testing and expert consultation
Since cortisol level may not be reported quickly,corticosteroid should be administered, pending results,if the clinical situation is suggestive of acute adrenalinsufficiency
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Treatment
Obtain baseline blood samples for cortisol, electrolyte,etc
Infuse D5 normal saline to support blood pressure
Administer dexamethasone 4 mg IV, then 4 mg IVevery 6 hrs
Perform short adrenocorticotropic hormone stimulationtest if needed for diagnosis
If the diagnosis of adrenal failure is confirmed,hydrocortisone 100 mg IV, then 100 mg every 8 hrs,can be administered. Some physicians preferadministration of hydrocortisone as a continuousinfusion, 300 mg over 24 hrs
Treat precipitating conditions
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Hyperglycemic Syndromes
Results from a relative or absolute lackinsulin
Characterized by: hyperglycemia, keto-
acidosis, and osmotic diuresis-induceddehydration
Life-threatening hyperglycemic syndromes:
diabetic ketoacidocis (DKA) and hyper-glycemic hyperosmolar nonketotic syndro-me (HHNK)
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Clinical manifestations
Result from hyperglycemia & excessketone productionHyperglycemia:Hyperosmolality
Osmotic diuresis-induced dehydrationFluid & electrolyte loss
Dehydration
Volume depletion
Ketone (DKA):Acidosis
Osmotic diuresis
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Clinical features
Weakness
Dehydration
Polyuria
Polydipsia Altered mental status
Coma
Tachycardia
Arrhythmias
Hypotension
Anorexia
Nausea/vomiting
Ileus
Abdominal pain Hyperpnea
Fruity odor to thebreath (DKA)
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Laboratory investigation
Hyperglycemia Hyperosmolality (more common in HHNK)
Glukosuria
Ketonemia/Ketonuria (DKA)
Anion gap metabolic acidosis (DKA)
Hypokalemia
Hypophosphatemia
Hypomagnesemia
Leukocytosis
Azotemia Elevated amylase
Creatine phosphokinase
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Treatment (1)
The goal: to restore the fluid & electrolyte
balance, provide insulin, & identify
precipitating factors (infection, stroke, MI,
pancreatitis) Volume deficits correlate with the severity of
hyperglycemia & are usually greater in HHNK
Normal saline: replenish IV volume & restore
hemodynamic stability (1 L in the first hour,
250-500 mL/hr as needed)
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Treatment (2)
After 1-2 L of NS, fluids with less Cl (0.5saline) should be used to avoidhyperchloremic metabolic acidosis
Urine output should be maintained at 1-3mL/kg/hr (ensure adequate tissueperfusion & clearance of glucose)
Invasive hemodynamic monitoring(arterial catheter, PA catheter): requiredin patients with underlying CV disease
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Treatment (3)
DKA: Loading dose: 5-10 U regular human insulin
IV route is the most reliable & easiest to
titrate Continuous infusion is necessary with serial
monitoring of the blood glucose &
electrolyte concentration
HHNK: Smaller doses of insulin are usually
adequate (1-2 U)
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Monitor glucose levels
Frequently
Glucose decreases to >250 mg/dL (150 mg/dL (>8.3 mmol/L)
while continuing insulin infusion
Subcutaneous insulin (BS is controlled,
ketonemia has cleared, the patient is stable)
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Insulin & correction of acidosis shift potassium
intracellularly & may lead to precipitous drops
in K levels
K deficit range from 3-10 mEq/kg K should be added to fluid therapy as soon as
serum K is recognized or thought to be normal
or low and urine output is documented
K levels should be monitored frequently until
levels stabilize & acidosis is resolved (DKA)
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Priorities in initial resuscitation of DKA
Institute crystalloid resuscitation, initially with NS
Institute insulin infusion at 0.1 U/kg/hr
Consider bicarbonate if pH
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References:
Fundamental Critical Care Support, CourseText, 3rd edition, Society of Critical CareMedicine
Lange Clinical Anesthesiology, 3rd edition,Lange Medical Books/McGraw-Hill MedicalPublishing Division
Physiologic and Pharmacologic Bases ofAnesthesia, 2nd edition, Williams and Wilkins
Textbook of Critical Care, 3rd edition, W.B.Saunders Company