electrolyte imbalance and acid-base disorders

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 – CausesSeveral 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 ?