electrolyte imbalance and acid-base disorders victor politi, m.d., facp, medical director, st....

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 ?