Dehydration

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).
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).
3. In a dehydrated patient,
   1. Determine the appropriate volume of fluid for replacement of deficiency and ongoing needs,
   2. Use the appropriate route (oral if the patient is able; IV when necessary).
4. When treating severe dehydration, use objective measures (e.g., lab values) to direct ongoing management.
5. In a dehydrated patient,
   1. Identify the precipitating illness or cause, especially looking for non-gastro-intestinal, including drug-related causes,
   2. Treat the precipitating illness concurrently.
6. Treat the dehydrated pregnant patient aggressively, as there are additional risks of dehydration in pregnancy.

Symptoms of dehydration

• Acute illness
  • GI (N/V/D)
  • Skin (Fever/burns)
  • New medications (diuretics)
• Increased thirst
• Decrease urine/sweating/tears
• Weight loss
• Altered mental status, lethargy, irritability

Signs of dehydration

• Vital signs
  • Orthostatic vitals (HR↑ >30bpm, sBP ↓> 20 or dBP ↓> 10mmHg)
  • Tachycardia, tachypnea
  • Hypotension in severe hypovolemia
• Altered mental status
• Dry mucosa
• Sunken eyes
• Skin turgor
• Capillary refill >3s
• Decreased urine output

Degree

• Mild (3-5% volume lose) - Absent clinical signs
  • Home-based treatment
• Moderate (6-9% volume loss) - Tachycardia, orthostatic hypotension, decreased skin turgor, dry mucous membranes, irritability, delayed capillary refill, deep respirations, possible decreased urine output/tearing and sunken fontanelle
  • ORT (eg. Pedialyte, Enfalyte, breastmilk) x 1 hour, re-assess
    • If concerned, see treatment for severe
• Severe (≥10% volume loss) - "Near-shock" hypotension, lethargy, altered mental status, delayed capillary refill, cool/mottled extremities, tachypnea
  • Requires aggressive isotonic fluid resuscitation to prevent tissue injury
    • 20-40mL/kg IV NS over one hour
    • Consider labs (concern if pH < 7.32, bicarb ≤ 17 mEq/L)

Indications for IV

• Inability for oral intake (mental status, ileus)
• Inability to administer ORT (eg. no caregiver)
• Persistent vomiting
• Electrolyte abnormalities where ORT cannot be monitored

Medications

• Can consider one dose of oral ondansetron to reduce vomiting and facilitate ORT

Laboratory

• Consider Venous or Capillary Blood Gas (pH, electrolytes) +/- serum electrolytes (more reliable than blood gas)
  • Serum bicarbonate ≤ 17 mEq/L in children differentiates moderate-severe hypovolemia from mild
    • Use BUN/Creat ratio in adults
  • Sodium deficit in hyponatremia = 0.6 (or % total body water) × weight in kg x (ideal Na - pt's Na)
    • Replace sodium slowly <12mmol/L/day to avoid central pontine myelinolysis (consider calculator)
  • Free water deficit in hypernatremia = 0.6 (or % total body water) × weight in kg × (pt's Na / ideal Na – 1)
    • % total body water (TBW) = 0.6 if male and 0.5 if female
  • Fluid replacement for a 10 kg child with a 10 percent hypovolemic loss, the following calculations can be made:
    • TBW(n): 0.6 x body weight (eg. 10kg = 6 L), as water is about 60% of total body mass
      • Total fluid deficit: % deficit (eg. 10%) X 6L = 0.6 L
        • Replace half fluids in first 8h, and remaining of 16h

Maintenance in Children (4-2-1 rule)

• 1-10kg = 4 x Wt (kg) mL/hr
• >10-20kg = 40 + 2 x (Wt over 10kg) mL/hr
• >20kg = 60 + 1 x (Wt over 20kg) mL/hr
  • Max of 100mL/hr
  • Can use D5NS

Parkland Formula

• Fluid required in first 24h = 4mLx weight (kg) x BSA (%)
  • Half in 8h, rest in 16h
  • 9% each arm, 18% each leg, 18% front torso, 9% head