Download Importance of Homeostasis

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 Acidbase 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
Hypocalcemia - Symptoms
• 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 - 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
Hyperkalemia
• Associated With:
– HIV
– diabetic ketoacidosis
– Medications
•
•
•
•
Surgical Med - Aminocaproic acid
Ace Inhibitors
Trimethoprim
Immunosuppressive medications
Hyperkalemia
• Findings
– Muscle weakness
– Abdominal distention
– Diarrhea
– Rare finding – flaccid paralysis
Hyperkalemia
• 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 - 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
Hyperkalemia – Emergent TX
• 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 – 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
Hypokalemia - Signs
• Common findings
– Muscular weakness
– Muscle cramps
– Fatigue
– Constipation or ileus
Hypokalemia - Labs
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•
•
•
•
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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
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•
•
•
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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
–
•
SEVERE HYPONATREMIA
–
•
plasma sodium levels under <135 mmol x L(-1).
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, thirdspacing)
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
Hypervolemic
Hypovolemic
Euvolemic
UNa+ < 10meq/L
Extrarenal salt loss
1. Dehydration
2. Diarrhea
3. Vomiting
UNa+> 20meq/L
Renal salt loss
1. Diuretics
2. Ace inhibitors
3. Nephropathies
4. Mineralocorticoid deficiency
5. Cerebral sodium wasting syndrome
1. SIADH
2. Post-op hyponatremia
3. Hypothyroidism
4. Psychogenic polydipsia
5. Beer potomania
6. Idiosyncratic drug reaction
7. Endurance exercise
Edematous states
1. CHF
2. Liver Disease
3. Nephrotic syndrome (rare)
4. Advanced renal failure
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 ?