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clinical dehydration
Etiology:
1) combined Na+ & H2O depletion
a) extra-renal losses
- gastrointestinal
- vomiting
- diarrhea
- gastrointestinal suction
- fistula
- abdominal sequestration
- peritonitis
- rapid accumulation of ascites
- skin
- sweating
- burns
b) renal losses
- renal disease
- diuretic phase of acute renal failure
- post-obstructive diuresis
- chronic renal failure
- salt-wasting renal tubular disease
- diuretic excess
- osmotic diuresis
- diabetic glycosuria
- urea
- mineralocorticoid deficiency
- Addison's disease
- hypoaldosteronism
2) isolated H2O depletion
a) extrarenal
- skin (insensible losses)
- lungs
b) renal
- diabetes insipidus (central & nephrogenic)
c) hypothalamic dysfunction
Pathology:
1) diminished glomerular filtration (pre-renal azotemia)
Clinical manifestations:
1) diminished skin turgor
2) dry mucous membranes
3) resting supine tachycardia
4) orthostatic hypotension
5) supine hypotension with more severe dehydration
6) lethargy, weakness & confusion, especially in the elderly
7) oliguria
8) dizziness (GRS9) [3]
9) dehydration & delirium is common in the elderly
Laboratory:
1) hematocrit may be increased
2) serum protein may be increased
3) serum Na+ may be increased or decreased
4) serum creatinine & urea nitrogen are generally increased (pre-renal azotemia)
5) BUN/creatinine ratio generally > 20
6) urinary Na+
a) < 10 mmol/L with extra-renal losses
b) > 20 mmol/L with renal or adrenal disorders (until Na+ depletion becomes severe)
Complications:
- dehydration associated with acute renal failure demonstrated by rising serum creatinine may be associated with diminished clearance of renally cleared drugs
- elevated gabapentin levels due to diminished clearance may manifest as dizziness [4]
Management:
1) modest dehydration may be corrected by oral fluids in patients without gastrointestinal disorders
2) intravenous fluids
a) normal saline (0.85%) is generally fluid of choice
b) 2-3 liters is generally adequate for moderate dehydration
c) larger volumes may be required for severe dehydration
3) correct electrolyte disturbances
4) (hypodermoclysis) subcutaneous infusion of fluid
-> up to 1500 mL of fluid (i.e. saline) may be infused daily into subcutaneous tissue (i.e. thigh, abdominal wall, thorax or back)
Related
clinical hydration
hypernatremia
hyponatremia
lack of water
General
hypovolemia (extracellular volume depletion)
References
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY,
1994, pg 243-44
- Journal Watch 20(17):138, 2000
- Geriatric Review Syllabus, 9th edition (GRS9)
Medinal-Walpole A, Pacala JT, Porter JF (eds)
American Geriatrics Society, 2016
- Levy HB.
Polypharmacy reduction strategies: tips on incorporating American Geriatrics
Society Beers and screening tool of older people's prescriptions criteria.
Clin Geriatr Med. 2017;33:177-187.
PMID: 28364990