electrolyte imbalance and acid-base disorders victor politi, m.d., facp, medical director, st....
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Electrolyte Imbalance and Acid-Base disorders
Victor Politi, M.D., FACP, Medical Director, St. John’s University Dr. Andrew J. Bartilucci Center College of Pharmacy and Allied Health Professions, PA Program
Importance of Homeostasis
• Fluid and electrolyte and Acid-base balance are critical to health and well-being – Maintained by intake and output
– Regulation by renal and pulmonary systems
Imbalances Result From:
• Illness
• Altered fluid intake
• Prolonged vomiting or diarrhea
Distribution of Body Fluids
• Water is the largest single component of the body– 60% of adult’s weight is water
• Healthy people can regulate balance
Composition of Body Fluids
• Water• Electrolytes
– Separates into ions when dissolved• Carries an electrical charge
– Positive charge – CATIONS
» Sodium, Potassium, Calcium
– Negative charge – ANION
» Bicarbonate, Chloride
Fluid Intake
• Regulated primarily by thirst mechanism – In the hypothalamus
• Osmoreceptors monitor serum osmotic pressure– Hypothalamus stimulated when osmolarlity increases
– Thirst mechanism stimulated
» With decreased oral intake
» Intake of hypertonic fluids
» Loss of excess fluid
» Stimulation of renin-angiotensisn-aldosterone mechanism
» Potassium depletion
» Psychological factors
» Oropharyngeal dryness
Fluid Intake (cont)
• Average adult intake– 2200-2700 cc/day
• Oral – 1100-1400• Solid foods – 800-1000• Oxidative metabolism – 300
– By-product of cellular metabolism of ingested foods
Fluid Intake (cont)
• Must be alert
• Able to perceive mechanism
• Able to respond to mechanism
• **At risk for dehydration:– Elderly– Very young– Neurological disorders– Psychological disorders
Fluid Output Regulation
• Kidneys– Major regulatory organ
• Receive about 180 liters of blood/day to filter• Produce 1200-1500 cc of urine
• Skin– Regulated by sympathetic nervous system
• Activates sweat glands– Sensible or insensible-500-600 cc/day
» Directly related to stimulation of sweat glands
• Respiration– Insensible
• Increases with rate and depth of respirations, oxygen delivery– About 400 cc/day
• Gastrointestinal tract – In stool
– Average about 100-200» GI disorders may increase or decrease it.
Acid-Base Balance• pH measures amount of Hydrogen ion
concentration– Greater the concentration, lower the pH
• 7 is neutral; <7 acidic; >7 basic or alkaline
– Needed to maintain cell membrane integrity and speed of cellular enzymatic actions
– Normal range – 7.35-7.45– Regulated by buffers
Physiological Regulation
• Lungs and Kidneys – Lungs adapt fast
• Try to correct pH before biological buffers kick in– Hydrogen and carbon dioxide levels provide stimulus for
respirations
» Lungs alter depth and rate according to hydrogen concentration
– With metabolic acidosis, respirations increase to exhale more carbon dioxide
– Metabolic alkalosis, lungs retain carbon dioxide by decreasing respiraitons
– Kidneys take from a few hours to several days• Reabsorb bicarbonate in case of acid excess; excrete it in
cases of acid deficit
Common Disturbances Electrolyte Balance
• Sodium– Hypernatremia (Na > 145, sp gravity < 1.010)
• Caused by excess water loss or overall sodium excess– Excess salt intake, hypertonic solutions, excess
aldosterone, diabetes insipidus, increased s water loss, water deprivation
– S&S: thirst, dry, flushed skin, dry, stick tongue and mucous membranes
– Hyponatremia (Na < 135, sp gravity > 1.030)• Occurs with net loss of sodium or net water excess
– Kidney disease with salt wasting, adrenal insufficiency, GI losses, increased sweating, diuretics, SIADH
– S&S: personality change, postural hypotension, postural dizziness, abd cramping, n&v, diarrhea, tachycardia, convulsions and coma
Common Disturbances Electrolyte Balance
• Potassium– Hyperkalemia (K > 5.3; EKG irregularities-bradycardia,
heart block, wide QRS pattern-cardiac arrest)• Primary cause: renal failure; major symptom: cardiac
irregularity– Fluid volume deficit, massive cell damage, excess K+ given,
adrenal insufficiency, acidosis, rapid infusion of stored blood, potassium-sparing diuretics
– S&S: dysrhythmias, paresthesia
– Hypokalemia (K < 3.5; EKG irregularities-ventricular)• Most common electrolyte imbalance; affects cardiac
conduction and function. Most common cause: potassium wasting diuretics
– Diarrhea, vomiting, alkalosis, excess aldosterone secretion, polyruia, extreme sweating, insulin to treat diabetic ketoacidosis
– S&S: weakness, ventricular dysrhythmias, irregular pulse
Common Disturbances Electrolyte Balance
• Calcium– Hypercalcemia (Ca > 5; x-rays show calcium loss,
cardiac irregularities)• Frequently symptom of underlying disease with excess
bond resorption and release of calcium– Hyperparathyroidism, malignant neoplastic disease,
Paget’s disease, Osteoporosis, prolonged immobization, acidosis
– S&S: anorexia, nausea and vomiting, weakness, kidney stones
– Hypocalcemia (Ca < 4.0, EKG abnormalities)• Seen in severe illness
– Rapid blood transfusion with citrate, hypoalbuminemia, hypoparathyroidism, Vitamin D deficiency, Pancreatitis, Alkalosis
– S&S: numbness and tingling, hyperactive reflexes, positive Trousseau’s sign (wrist), positive Chvostek’s sign (cheek), tetany, muscle cramps, pathological fracture
Common Disturbances Electrolyte Balance
• Chloride
• Usually seen with acid-base imbalance– Hyperchloremia (Na >145, Bicarb <22)
• Serum bicarbonate values fall or sodium rises
– Hypochloremia (pH > 7.45)• Excess vomiting or N/G drainage; loop of
thiazide diuretics because of sodium excretion– Leads to metabolic alkalosis due to reabsorption of
bicarbonate to maintain electrical neutrality
Acid Base Balance
• Arterial blood gas is best measure– pH
• Measures hydrogen ion concentration– 7.35-7.45
– PaCO2 • Measures carbon dioxide (pulmonary ventilation)
– 35-45 < hyperventilation; > hypoventilation
– PaO2
• Oxygen in arterial blood– 80-100
– Oxygen Saturation• How much hemoglobin is carrying oxygen
– 95-99%
– Base Excess • How much blood buffer is present
– High – alkalosis Caused from: Antacids, rapid blood transfusion, IV bicarb– Low – acidosis Caused from: Diarrhea
– Bicarbonate• Major renal component of acid-base balance
– Excreted and reproduced by kidneys• 22-26; 20 times the level of carbonic acid : low is metabolic acidosis, high alkalosis
Common Disturbances in Acid-Base Balance
• Respiratory acidosis (pH <7.35; CO2> 45;)
– Increased carbon dioxide, excess carbonic acid, increased hydrogen ion concentration
• Causes: HYPOVENTILIATION– Atelectasis, pneumonia, cystic fibrosis, respiratory failure,
airway obstruction, chest wall injury, overdose, paralysis of respiratory muscles, head injury, obesity
– S&S: neurological changes and respiratory depression» Confusion, dizziness, lethargy, headache, ventricular
dysrhythmias, warm flushed skin, muscular twitching
Common Disturbances in Acid-Base Balance
• Respiratory alkalosis (pH > 7.45; CO2 < 35;)
– Decreased carbon dioxide, decreased hydrogen ions
• Causes: hyperventilation– asthma, pneumonia, inappropriate ventilator settings, anxiety,
hypermetabolic state, CNS disorder, salicylate overdose
– S&S: dizziness, confusion, dysrhythmia, tachypnea, numbness and tingling, convulsions, coma
Common Disturbances in Acid-Base Balance
• Metabolic acidosis (pH < 7>35; Bicarb < 22)– Increased acid (hydrogen ions, decreased
sodium bicarbonate• High Anion Gap (Sodium minus Chlorine + Bicarb)
– Causes: starvation, diabetic ketoacidosis, renal failure, lactic acidosis, drug use (paraldehyde, aspirin)
– S&S: tachypnea with deep respirations, headache, lethargy, anorexia, abdominal cramps
Common Disturbances in Acid-Base Balance
• Metabolic alkalosis– Loss of acid (hydrogen ions) or increase
bicarbonate• Most common cause: vomiting and gastric
secretions– Hypokalemia, hypercalcemia, excess aldosterone,
use of drugs (steroids, bicarb, diuretics)– S&S: numbness and tingling, tetany, muscle cramps
Assessing Blood Gases• 1st look at pH
– Over 7.45 Alkalosis– Below 7.35 Acidosis
• 2nd check CO2– Should move in opposite direction as pH
• if abnormal, respiratory cause• if normal, metabolic
• 3rd evaluate bicarbonate– Should move in same direction as pH
• If so, metabolic cause• if not, respiratory cause
• 4th both CO2 and bicarbonate abnormal?– Which more closely corresponds to pH and deviates more
from normal?• Shows likely cause, other is trying to compensate
Hypercalcemia
Hypercalcemia
• Most common causes (90% of cases):– Malignancy associated hypercalcemia
• Tumor production of PTH-related protein is the commonest paraneoplastic endocrine syndrome, accounting for most cases of hypocalcemia in inpatients
– Primary hyperparathyroidism• Most common cause in ambulatory patients
Hypercalcemia - symptoms
• Symptoms• (usually occur if serum calcium is > 12mg/dl and
tend to be more severe if hypercalcemia develops acutely)
– Constipation – Polyuria– Heart
• Ventricular extrasystoles and idioventricular rhythm
– Neurologic symptoms • Stupor, coma, azotemia in severe cases
Hypercalcemia - TX
• Treatment– Ultimate goal – locate primary disease
process & control– Treatment of hypercalcemia of malignancy
• Bisphosponates – effective in 95% of cases
– Emergency tx of choice• Saline & furosemide (prevent volume overload and
enhances Ca2+ excretion)
Hypocalcemia
Hypocalcemia
• Often mistaken as a neurological disorder
• Most common cause– renal failure
• Other causes:– Malabsorption– Vitamin D deficit– Alcoholism– Diuretic therapy– Endocrine disease
Hypocalcemia - Symptoms
• Hypocalcemia increase excitation of nerve and muscle cells, primarily affecting the neuromuscular and cardiovascular systems
• Symptoms:– Muscle cramps and tetany– Laryngospasm w/stridor– Convulsions – Paresthesias of lips & extremities– Abdominal pain
Hypocalcemia - Symptoms
• Chvostek’s & Trousseau’s signs are usually readily elicited– Chvostek’s sign
• Contraction of the facial muscle in response to tapping the facial nerve anterior to the ear
– Trousseau’s sign• Carpal spasm occurring after occlusion of the
brachial artery with a bp cuff for 3 minutes
Hypocalcemia - Symptoms
Hypocalcemia - Labs
• ECG:– Prolonged QT interval
• Serum calcium concentration:– < 9mg/dl
• Serum magnesium– usually low
• Serum phosphate level– usually elevated in hypoparathyroidism or end-stage
renal failure– Suppressed in early stage renal failure or vitamin D
deficiency
Hypocalcemia - Tx
• Severe, symptomatic hypocalcemia– 10-15 milligrams of calcium per kilogram of body
weight, or 6-8 10-ml vials of 10% calcium gluconate (558-744mg of calcium) added to 1 liter of D5W and infused over 4-6hrs. Adjust infusion rate to maintain serum calcium level at 7-8.5mg/dL
– In presence of tetany, arrhythmias or seizures• Calcium gluconate 10% (10-20 ml) IV over 10-15min
Hypocalcemia - Tx
• Asymptomatic Hypocalcemia– Oral calcium 1-2g and vitamin D preparations
are used
Hyperkalemia
Hyperkalemia
• Many cases associated with acidosis
• Pseudohyperkalemia – result of lysis of red cells releasing potassium into the serum
• Associated With:– HIV – diabetic ketoacidosis – Medications
• Surgical Med - Aminocaproic acid• Ace Inhibitors• Trimethoprim• Immunosuppressive medications
Hyperkalemia
Hyperkalemia
• Findings– Muscle weakness– Abdominal distention– Diarrhea– Rare finding – flaccid paralysis
• Heart rate may be slow, V-Fib & cardiac arrest may occur
• ECG changes include: – Peaked T waves, widening of QRS, biphasic
QRS-T complexes
• Note:nearly 50% of cases with serum levels 6.5meq/L or greater will not exhibit ECG changes
Hyperkalemia
Hyperkalemia - TX
• Confirm elevated level of serum potassium (measure in plasma rather than serum)
• Tx consists of witholding potassium and giving cation exchange resins by mouth or enema– Sodium polystyrene sulfonate 40-80g/d
• Indicated if cardiac toxicity or muscular paralysis present or if hyperkalemia severe > 6.5-7 meq/L– Calcium gluconate 10% 5-30ml IV
– NaHCO3 44-88 meq (1-2 ampules) IV
– Insulin 5-10 units, IV plus glucose 50% 25g,1 ampule, IV
– Nebulized albuterol 10-20mg in 4 ml normal saline inhaled over 10 min
Hyperkalemia – Emergent TX
Hyperkalemia – Nonemergent Tx
• Loop diuretic (Furosemide) 40-160mg IV or orally w or w/o NaHCO3, 0.5-3 meq/kg daily
• Sodium polystyrene sulfonate (Kayexalate) oral: 15-30g in 20% sorbitol (50-100mL) rectal: 50g in 20% sorbitol
• Hemodialysis
• Peritoneal Dialysis
Hypokalemia
Hypokalemia
• Severe hypokalemia may induce dangerous arrhythmias or rhabdomyolysis
• Self limited hypokalemia occurs in 50-60% of trauma patients (possibly related to enhanced release of epinephrine)
• Hypokalemia in the presence of acidosis suggests profound potassium depletion and requires urgent tx
• Common findings– Muscular weakness– Muscle cramps– Fatigue– Constipation or ileus
Hypokalemia - Signs
Hypokalemia - Labs
• ECG
• Decreased amplitude
• T wave broadening
• Prominent U waves
• PVCs
• Depressed ST segment
Hypokalemia – Causes
Several Causes of Hypokalemia– Decreased potassium intake– Potassium shift into the cell
– Renal potassium loss• Primary hyperaldosteronism• Renovascular HTN• Cushing’s Syndrome• Bartter’s Syndrome• Metabolic acidosis
– Extrarenal potassium loss• Vomiting, diarrhea, laxative abuse, • Zollinger-Ellison syndrome
Hypokalemia- Tx
• Mild to moderate deficiency– Oral potassium
• 20 meq/L to prevent hypokalemia, • 40-100 meq/L over a period of days to weeks to
treat hypokalemia and fully replete potassium stores
Hypokalemia - TX
• Moderate to severe– Peripheral IV should not exceed 40meq/L at
rates up to 40 meq/L/h– Continuous ECG monitoring indicated– Check serum potassium q 3-6 hours– Correct magnesium deficiency
Hyponatremia
Hyponatremia
• MILD HYPONATREMIA – plasma sodium levels under <135 mmol x L(-1).
• SEVERE HYPONATREMIA – plasma sodium levels below < 130 mmol x L(-1)
compromising health and performance.
• CRITICAL HYPONATREMIA – plasma sodium levels below 120 mmol x L(-1)
(may be fatal).
Hyponatremia
• Defined as serum sodium concentration less than 130 meq/L
• Most common electrolyte abnormality observed in hospitalized patient population
• Most cases of hyponatremia result from water imbalance not sodium imbalance.
Hyponatremia
• Initial approach is to determine serum osmolality
• Normal (280-295 mosm/kg)
• Low (< 280 mosm/kg)
• High (> 295 mosm/kg)
Hyponatremia
• Measurement of urine sodium helps distinguish renal from non-renal causes– Urine sodium > 20 meq/L
• consistent with renal salt wasting (diuretics, ACE inhibitors, mineralocorticoid deficiency, salt-losing nephropathy)
– Urine sodium < 10meq/L or fractional excretion of sodium < 1%
• implies sodium retention by kidney to compensate for extrarenal fluid loss (vomiting, diarrhea, sweating, third-spacing)
Hyponatremia
• Isotonic & Hypertonic hyponatremia can be ruled out by determining serum osmolality, blood lipids, and blood glucose
• Osmolality = 2 (Na+ meq/L) +
Glucose mg/dL + BUN mg/dL
18 2.8
Hypotonic hyponatremia
Volume Status
HypovolemicEuvolemic
Hypervolemic
Edematous states1. CHF2. Liver Disease3. Nephrotic syndrome (rare)4. Advanced renal failure
1. SIADH2. Post-op hyponatremia3. Hypothyroidism4. Psychogenic polydipsia5. Beer potomania6. Idiosyncratic drug reaction7. Endurance exercise
UNa+ < 10meq/LExtrarenal salt loss1. Dehydration2. Diarrhea3. Vomiting
UNa+> 20meq/LRenal salt loss1. Diuretics
2. Ace inhibitors3. Nephropathies
4. Mineralocorticoid deficiency5. Cerebral sodium wasting syndrome
Hyponatremia - Tx
• Treatment of underlying condition • Water restriction• Diuretics• Hypertonic 3% saline
– Dangerous in volume overloaded states, not routinely recommended
– Emergency dialysis
Hypernatremia
Hypernatremia
– Na > 145, sp gravity < 1.010• An intact thirst mechanism usually prevents
hypernatremia
• Excess water loss can cause hypernatremia only when adequate water intake is not possible, as with unconscious patients
• Rarely, excessive sodium intake may cause hypernatremia
Hypernatremia - Symptoms
• Typical Findings include; – orthostatic hypotension, oliguria
• In severe cases:– hyperthermia, delirium, and coma
Hypernatremia- TX
• Treatment directed at correcting the cause of fluid loss and replacing water and as needed, electrolytes
• If hypernatremia is corrected too rapidly, the osmotic imbalance may cause water to preferentially enter brain cells causing cerebral edema and potentially severe neurologic impairment
Questions ?