Dehydration – BC Guideline 2010

Dehydration
  • XS intracellular fluid loss (from GI, skin, or kidney) usually due to hypovolemia
  • Highest morbidity and mortality in peds
Hypovolemia

1) Hypertonic/hypernatremic

  • GI losses, fever, DM, renal dz
  • Net loss of extracellular water, or gain of sodium

2) Isotonic

  • Hemorrhage, GI losses, trauma
  • Loss of sodium is proportional to water

3) Hypotonic / hyponatremic

  • GI Losses, pancreatitis, heart failure, ascites,
  • adrenal insufficiency, psychogenic polydipsia, salt wasting nephropathy / DI
  • net loss of sodium relative to extracellular water

1  When assessing the acutely ill patient, look for signs and symptoms of dehydration. (e.g., look for dehydration in the patient with a debilitating pneumonia).

In patients with unstable vital signs or decreased level of consciousness, the possibility of severe dehydration should be considered. Although

Although change in weight is the most accurate way to determine the degree of dehydration, this is often not practical and physical signs may be helpful.

Hx:
  • Acute illness, N/V/D
  • Meds
  • ↑ thirst, Concentrated urine, decreased sweating, postural dizzy, flushed
  • Lethargy, ↓ LOC
  • Peds: ↓ # number of wet diapers, crying with tears?, recent wt when well?
PE: degree of extracellular Volume contraction
  • Postural Vitals: + if HR↑ >30bpm, sBP ↓ > 20mmHg or dBP ↓ > 10mmHg after standing for 1-2 min
  • Resting tachycardia >90bpm / weak pulse
  • Supine HoTN
  • Coma, dry mucosa / tongue, sunken eyeballs, skin pinch
  • ↓ U/O

Mild (5% 2yr fluid loss)
  • Normal HR/BP/Ant Fontanelle, Eyes, Skin Turgot, Cap Refill (<3sec)
  • Decreased Urine Output and slightly dry oral mucosa
Moderate (10% <2yr, 6% >2yr fluid loss)
  • Rapid HR, Low-normal BP, Markedly decreased U/O
  • Dry oral mucosa, sunken ant fontanelle / eyes, ↓ skin turgor & normal-↑ cap refill
Severe (15% <2yr, 9% >2yr fluid loss)
  • Rapid, weak HR
  • Shock – decreased BP (late finding in peds)
  • Anuria
  • Parched oral mucosa
  • Markedly sunken ant fontanelle and eyes
  • Tenting & increased cap refill (>3sec)

2  In the dehydrated patient, assess the degree of dehydration using reliable indicators (e.g., vital signs) as some patients’ hydration status may be more difficult to assess (e.g., elderly, very young, pregnant).

Assessment of Severity of Dehydration: C BASE H2O – see above
  • Cap Refill
  • BP
  • Ant fontanelle
  • Skin turgor
  • Eyes sunken
  • HR
  • Oral mucosa
  • Output of urine

3  In a dehydrated patient,
a)  Determine the appropriate volume of fluid for replacement of deficiency and ongoing needs,
b)  Use the appropriate route (oral if the patient is able; IV when necessary).

Dehydrated child must receive adequate fluid management –
  • replace 1) deficit + 2) ongoing losses (one large vomit / diarrhea = 8ml/kg body wt) + 3) provide maintenance fluids
  • replace 1/2 in the first 8 hr and second 1/2 over remaining 16 hr
Deficit
  • = pre-illness wt – post-illness wt
  • = % deficit x 10ml/kg x pre-illness wt
  • = 0.6 x wt x (Na-140)/140
Degree of dehydration
  1. No dehydration
    • Age-appropriate diet and replace ongoing losses
  2. Mild Dehydration
    • Rehydrate with ORT at 50ml/kg over 4h
    • Replace ongoing losses with ORT
    • Age-appropriate diet after rehydration
  3. Moderate Dehydration
    • Rehydrate with ORT at 100ml/kg over 4h
    • Replace ongoing losses with ORT
    • Age-appropriate diet after rehydration
  4. Severe dehydration
    • IV NS or RL at 20-40ml/kg over 1hr
      • Reassess and repeat prn
    • Begin ORT to replace ongoing losses when stable
    • Age-appropriate diet after hydration
Maintenance Fluid Requirement – 4-2-1 Rule or 100-50-20 rule
  • 1-10kg: 100cc/kg/d or 4 cc/kg/h
  • 11-20kg: 50cc/kg/d or 2 cc/kg/h
  • >20kg: 20cc/kg/d or 1 cc/kg/h
Common IV fluid
  • 1st month of life: D5W/0.2 NS + 20mEq KCL/L (only add KCL if voiding well)
  • children: D5W/NS + 20m EqKCl/L
  • NS as bolus to restore circulation in dehydrated children

Initial Tx with ORT
  • ↓ cost & incidence of iatrogenic hyper/hyponatremia,
  • no IV needed,
  • parental involvement
IV rehydration therapy:
  • Severe dehydration requires close monitoring & frequent assessment of electrolytes
  • Inability to tolerate ORT: Vomiting, ↓ LOC, ileus, monosaccharide malabsorption etc
  • Inability to provide ORT or Failure of ORT (persistent diarrhea or vomiting)

4  When treating severe dehydration, use objective measures (e.g., lab values) to direct ongoing management.

Initial B/W for all pt:
  • Electrolyte disturbances (Na, K, Cl) and glucose
  • Acid-base disturbances: blood pH, pCO2, HCO3
  • Impaired renal function: Cr, BUN (BUN/Cr >25:1 indicates dehydration)
  • Urine specific gravity and osmolality
Monitor Fluid and electrolyte status
  • Daily I/O (oral + IV & U/O, diarrhea, emesis, drains)
  • If receiving >50% of maintenance fluids through IV, serum electrolyte should be monitored DAILY and adjusted accordingly
  • Avoid iatrogenic hyper/hyponatremia
  • keep the possibility of SIADH in mind
    • Hyponatremia + excretion of concentrated urine
    • Renal faluire, certain meds (morphine), post-op, pain, N/V, pulm dz (PNA), CNS dz (meningitis)
    • Acute hyponatremia is associated with rapid administration of hypotonic IV, lead to cerebral edema and herniation

5  In a dehydrated patient,
a)  Identify the precipitating illness or cause, especially looking for non-gastro-intestinal, including drug-related, causes,
b)  Treat the precipitating illness concurrently.

Risk factors
  • Extremes of age
  • Acute illness
  • Cognitive impairment – delirium, sedation, psychosis
  • Limited fluid intake – dysphagia, fear of incontinence, limited mobility
  • Increased Fluid losses – illness (GI), environment, diuretics, hemorrhage, trauma
  • Altered thirst – CNS lesions, medications
Dehydration Etiology
  1. ↓ Intake:
    • poor oral intake during acute illness, due to dysphagia, or other factors
    • Breastfeeding difficulties,
    • eating disorders
  2. ↑ Losses
    • GI: diarrhea, vomiting, bleeding, pancreatitis / cirrhosis with ascites
    • Skin / mucous membranes: fever, sweating, burns, stomatitis
    • Vascular: trauma, hemorrhage
    • Heart failure
    • Urinary: osmolar diuresis (hyperglycemia, DKA), diuretic Tx, post-obstructive / Post ATN recovery diuresis
    • SIADH and salt wasting nephropathy – DI, psychogenic polydipsia, Adrenal insufficiency
    • Respiratory: tachypnea, bronchiolitis, PNA

6  Treat the dehydrated pregnant patient aggressively, as there are additional risks of dehydration in pregnancy.

  • During pregnancy, decreased systemic vascular resistance, increased venous pooling, changes in respiratory physiology and the presence of two rather than one patients makes the prompt treatment of dehydration imperative
  • Greater physiologic reserve (inc CO, HR, blood VO) – physical markers of dehydration will be delayed
  • T1/T2 – result in SA or oligohydramnios
  • T3 – Premature labour, abruption

References:
  • BC Guidelines and Protocols Advisory Committee. Oral Rehydration Therapy. 2010
  • TN2014
  • UpToDate
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Posted in 22 Dehydration, 99 Priority Topics, FM 99 priority topics, GI

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