4.4 Common Traps in Planning and Management

Maintenance IV Fluids: The 4-2-1 Rule

When a child cannot take adequate fluids by mouth, the nurse calculates maintenance fluids — the volume needed to replace normal urine, stool, and insensible losses. The bedside method is the 4-2-1 rule (derived from the Holliday-Segar formula):

• 4 mL/kg/hr for the first 10 kg of body weight
• 2 mL/kg/hr for the next 10 kg (11-20 kg)
• 1 mL/kg/hr for each kg above 20 kg

Worked example - a 22 kg child: (4 mL x 10 kg) + (2 mL x 10 kg) + (1 mL x 2 kg) = 40 + 20 + 2 = 62 mL/hr.

Worked example - a 6 kg infant: the whole weight is within the first 10 kg, so 4 mL x 6 kg = 24 mL/hr (equivalently the daily 100 mL/kg rule gives 600 mL/day = 25 mL/hr). The standard maintenance fluid for most children is a dextrose-containing isotonic or near-isotonic solution with added potassium once urine output is confirmed. Remember that maintenance is the baseline rate; a dehydrated child also needs deficit replacement on top of it, and a child in DKA is deliberately run at no more than about twice maintenance to avoid osmolar shifts.

Congenital Heart Defects and the Tet Spell

Congenital heart defects are grouped as acyanotic (left-to-right shunt, increased pulmonary flow) and cyanotic (right-to-left shunt, decreased pulmonary flow):

Tetralogy of Fallot has four components: ventricular septal defect, pulmonary stenosis, overriding aorta, and right ventricular hypertrophy. These children have hypercyanotic (tet) spells — sudden episodes of deep cyanosis and irritability, often with feeding or crying, peaking at 2-4 months. Priority intervention: place the infant in the knee-to-chest position (older children squat). This increases systemic vascular resistance and venous return, redirecting blood through the lungs and improving oxygenation.

Also keep the child calm, give supplemental oxygen, and notify the provider; morphine, IV fluids, and beta-blockers may follow. Coarctation of the aorta classically shows higher blood pressure and bounding pulses in the arms than the legs with weak or absent femoral pulses.

Digoxin Safety, Fever, and Pain Assessment

Digoxin is used in pediatric heart failure to strengthen contraction and slow the heart rate, but its therapeutic window is narrow. Before each dose the nurse takes a full-minute apical pulse and holds the dose and notifies the provider if the heart rate is below the age threshold — generally about 90-110 bpm in infants, under 70 in older children. Early digoxin toxicity in children presents as vomiting, anorexia, and bradycardia; check the level and serum potassium (hypokalemia potentiates toxicity).

Fever management: fever is a symptom, not a disease. Treat for comfort with weight-based acetaminophen (10-15 mg/kg/dose) or ibuprofen (10 mg/kg/dose, for children over 6 months); avoid aspirin in children because of the risk of Reye syndrome. Encourage fluids and light clothing; tepid sponging is not routinely recommended and alcohol baths are never used.

Pain assessment is developmental. Match the tool to the child:

• Neonates/preverbal: physiologic and behavioral scales (for example, FLACC or N-PASS).
• FLACC (Face, Legs, Activity, Cry, Consolability), scored 0-10, validated for ages 2 months to 7 years and nonverbal children.
• Wong-Baker FACES self-report, validated from about age 3.
• Numeric 0-10 scale for school-age and older children who understand numbers.

Under-assessing pain because a child cannot verbalize it is a classic exam trap — use the behavioral scale instead.

Deficit Replacement and Monitoring Fluid Therapy

Maintenance fluids keep a well-hydrated child even; a dehydrated child also needs the fluid deficit replaced on top of maintenance. The deficit is estimated from the percent dehydration and pre-illness weight: deficit (mL) = percent dehydration x weight (kg) x 10. For a 12 kg toddler who is 10% dehydrated, the deficit is 0.10 x 12 x 1000 = 1,200 mL, typically replaced over 24 hours alongside maintenance, with the first half often given in the first 8 hours for moderate cases. Severe dehydration or shock is treated first with rapid isotonic boluses of 20 mL/kg repeated until perfusion improves.

The nurse monitors the response rather than just running the pump: track urine output (the most sensitive indicator — aim for at least 1-2 mL/kg/hr in younger children), daily weights on the same scale, capillary refill, mucous membranes, fontanelle, and serial electrolytes. Strict intake and output is essential, and an infant's diapers are weighed (1 g equals roughly 1 mL of urine). Watch for overload (crackles, edema, weight gain, hypertension) as well as ongoing deficit.

A few traps recur: adding potassium only after urine output is confirmed; never giving concentrated IV potassium as a push (it is always diluted and infused); and recognizing that a child with persistent vomiting or altered mental status cannot rehydrate orally and needs the IV route. Matching the fluid type, rate, and route to the child's specific deficit and condition — and reassessing — is the core competency this section tests.