Famona.tripod.com

K. J. Lee: Essential Otolaryngology and Head and Neck Surgery (IIIrd Ed)
Chapter 31: Fluids, Electrolytes, and Acid-Base Balance
Critical disturbances in the fluid, electrolyte, or acid-base balance of the body may have no outward signs or symptoms and only diagnosed by laboratory testing. It is importantto note that the body will try to maintain volume at the expense of osmolarity, electrolytes,or pH. Nonspecific signs such as somnolence, confusion, or weakness may be the only hintsof an underlying abnormality.
The otolaryngolic patient is particularly prone to such disturbances because of the effects of anaesthesia, parenteral feeding, and underlying medical diseases such as diabetes,heart failure, or diuretic therapy. The following lists and tables review some of thesedisturbances. Therapy must be individualized based on all underlying conditions and theirpathophysiology.
Nonspecific Signs of Fluid, Electrolyte, or Acid-Base Disturbances
Signs of Fluid Disturbances
Overhydration
Dehydration
Hyperkalaemia
Potassium-sparing diurecticsHypoaldosteronism - especially in diabeticsCrush injuryRenal failureIncreased intake (salt substitutes)AcidosisProstaglandin inhibitors Decrease intakeCalcium gluconate: 1 ampule (10 mL = 940 mg) IV q 2 hrGlucose: 50 mL 50% dextrose plus insulin (crystalline zinc) 10 IU IV/SCSodium bicarbonate: 1.2 g TID PO or 1 ampule IV q 4 hr to keep bicarbonate level Loop diuretics: 40-80 mg furosemide (Lasix) or 50-100 mg ethacrynic acid (Edecrin) IV or PO. Do not use potassium-sparing diuretics such as spironolactone (Aldactone),hydrochlorthiazide and triamterene (Dyazide), or amiloride (Moduretic or Midamor).
Exchange resins: 25-50 mg sodium polystyrene sulfanate (Kayexelate) PO or by enema Mineralocorticosteroids 0.1 mg fludrocortisone (Florinet) PO q 24 hrDialysis: peritoneal or hemodialysis.
Table 31-1. Hyponatremia (Signs Are Those of Associated Fluid Status)
Pathogenesis
Volume Status
Etiology
Loss of sodium in excess of body water
Volume depletion
Renal losses: diuretics, nephritis, osmotic diuresis
Normal saline: ± 1 L IV q 4-6 hr if cardiac status satisfactory
Extra-renal losses: vomiting, diarrhea, thrid-space losses
Normal saline: ± 1 L IV q 4-6 hr if cardiac status satisfactory
Excess water
Slight overhydration
Addison's disease
- Steroids
Myxedema
- Thyroxine
Inappropriate anti-diuretic syndrome
1. Fluid restriction (1 L/24 hr)
2. Hypertonic saline 300 mL of 3% saline over 4 hr
3. Loop diuretics
4. Dilantin 100 mg t.i.d.
5. Lithium 300 mg p.o. q.i.d.
6. Demeclocycline 300 mg q.i.d.
Excess sodium and excess water
Overhydration with edema
Congestive heart lung
1. Fluid restriction
Nephrosis
2. Diuretics
Cirrhosis
Lasix 40-100 mg IV q 12-24 hr
Renal failure
Edecrin 50-100 mg IV q 12-24 hr.
Table 31-2. Causes of Hypernatremia
Therapy depends on fluid status and must be individualized. One should calculate
the fluid deficit and replace fluids gradually over 1-2 days to avoid cerebral edema or
congestive heart failure. Specific therapy must then be directed at the underlying
condition.
Water loss in excess of sodium loss
Central or nephrogenic diabetes insipidus
Vomiting
Diarrhea
Severe burns
Osmotic diuresis (calcium, glucose, IVP dye)
Excessive insensible losses
Inadequate water intake
Hypothalamic disease
Stupor
Administration of sodium in excess of water
Excessive salt ingestion IV or p.o.
Dialysis
Sodium retention
Cushing's syndrome
Hyperaldosteronism
Loss of renal concentration ability
Uremia
Hypokalemia
Lithium therapy
Methoxyflurane anesthesia
Sickle cell anemia
Multiple myeloma
Hypercalcemia.
Hypocalcemia
Hypoparathyroidism: iatrogenic, idiopathic.
PseudohypoparathyroidismPancreatitisRenal failureHypomagnesemiaVitamin D deficiencyMalabsorptionHypoalbuminemia (does not need therapy).
1. Acute therapy: 10 mL of 10% calcium chloride or calcium gluconate IV repeat of 2. Chronic therapy: (a) calcium 1 g p.o. t.i.d.
(b) Vitamin D 50.000 units, or Dihydrotachysterol 0.125 mg to 0.4 mg/day (c) Magnesium (if deficient) 2 mL magnesium sulphate IM p.r.n.
Table 31-3. Hypercalcemia
Hyperparathyroidism
Ectopic parathyroid hormone secretion
Bony metastases
Milk alkali syndrome
Vitamin D toxicity
Sarcoid
Tuberculosis
Therapy (to be individualized)
1. Parathyroidectomy
2. Hydration: oral fluids as tolerated
3. Saline 1-2 L IV q 2-4 hr (watch cardiac status)
4. Loop diuretics Lasix 40 mg, Edecrin 50 mg IV or p.o.
5. Phosphate 250-500 mg p.o. q 6 hr (as Neutra-Phos)
6. Steroids 100 mg Solu-Cortef IV q 8 hr or 25 mg cortisone acet. q 6 hr
7. Mithramycin 15-25 microg/kg IV q 24-48 hr
9. Indomethacin 25 mg p.o. q 6 hr.
Table 31-4. Acid-Base Disturbances
Disturbance
Hydrogen ion
bicarbonate
Metabolic acidosis
Metabolic alkalosis high
Respiratory acidosis
Respiratory alkalosis
Normal range
7.35-7.45
36-45 mEq/L
35-45 mmHg 22-26 mEq/L.
* Primary abnormality.
Causes of Metabolic Alkalosis
DiureticsVomitingDiarrheaAntacid therapyHyperladosteronismGastrointestinal fistula.
Potassium chloride to maintain K level above 3.5 mEq/L, fluids, carbonic anhydrase inhibitors (acetazolamide - Diamox - 250 mg p.o. q.i.d.). Treat underlying condition.
Causes of Respiratory Acidosis
General anesthesiaCardiac arrestSedationPulmonary edemaSevere pneumoniaBronchospasm LaryngospasmForeign body aspirationMechanical ventilation.
Alveolar hypoventilationObstructive pulmonary diseaseBrain tumorRespiratory muscle weakness or nerve damageRestrictive lung disease.
Directed at improving respiratory gas exchange.
Causes of Respiratory Alkalosis
AnxietyHysteriaOainFeverSalicylate intoxicationStrokeCNS trauma, infection, tumor.
Congestive heart failurePneumoniaHypoxiaHepatic insufficiencyGram-negative sepsisMechanical ventilators.
Treat underlying condition, increase "dead space" if on ventilator.
Causes of Metabolic Acidosis
Increased Anion Gap
Increased Organic Acid Production
lactic acidosisdiabetic ketoacidosisstarvation ketosisalcoholic ketoacidosis Inability to Excrete Inorganic Acids
Ingestion of Exogenous Acids
salicylatesmethanolparaldehideethylene glycol Normal Anion Gap
Loss of Bicarbonate
GI tract lossureterosigmoidostomyrenal tubular acidosisuremia (early)carbonic anhydrase inhibitor therapyhypoaldosteronismcorection of chronic respiratory alkalosis Chloride Therapy
hyperalimentationammonium chloridelysine hydrochloridearginine hydrochloride Administration of Acids with Rapid Renal Clearances of Unmeasured Ions
sulfuric acidphosphoric acidsulfur containing amino acids.
Bicarbonate therapy to raise pH above 7.3-7.35 and treat underlying abnormality.
Electrocardiographic Abnormalities of Electrolyte Abnormalities
Hyperkalemia
Hypokalemia
Prolonged QT intervalST segment depressionU waves Hypocalcemia
Lengthened QT segment (Normal T wave duration) Hypercalcemia

Source: http://famona.tripod.com/ent/lee/lee31.pdf