electrolyte imbalance Importance of Homeostasis by mikesanye

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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
   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
•   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


                                                                                      Hypervolemic
           Hypovolemic
                                                 Euvolemic


UNa+ < 10meq/L
                                                                                   Edematous states
Extrarenal salt loss                              1. SIADH
                                                                                   1. CHF
1. Dehydration                                    2. Post-op hyponatremia
                                                                                   2. Liver Disease
2. Diarrhea                                       3. Hypothyroidism
                                                                                   3. Nephrotic syndrome (rare)
3. Vomiting                                       4. Psychogenic polydipsia
                                                                                   4. Advanced renal failure
                                                  5. Beer potomania
                                                  6. Idiosyncratic drug reaction
                     UNa+> 20meq/L                7. Endurance exercise
                     Renal salt loss
                       1. Diuretics
                    2. Ace inhibitors
                   3. Nephropathies
              4. Mineralocorticoid deficiency
           5. 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
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