Acute nociceptive pain management — formative SAQs

1. The WHO two-step ladder

The WHO two-step analgesic ladder adapted for children places a non-opioid (paracetamol, with an NSAID where not contraindicated) plus an adjuvant and non-pharmacological measures at step one, and an opioid for moderate-to-severe pain at step two. The 2012 WHO revision removed the historical intermediate weak-opioid step, because codeine and tramadol are prodrugs activated by CYP2D6, and a CYP2D6 ultrarapid metaboliser converts them to a flood of morphine causing fatal respiratory depression; the drugs are contraindicated in children under 12 and after tonsillectomy. The modern step-two opioid is therefore morphine, which is titrated and monitored. ^[11]

2. The scheduled non-opioid foundation

Paracetamol is 15 mg per kg per dose every 4 to 6 h: for a 30 kg child that is 450 mg per dose (rounded to a formulation), to a maximum of 60 mg per kg per day (1.8 g per day here, well below the adult cap of 4 g per day, which I check explicitly). Ibuprofen is 5 to 10 mg per kg per dose every 6 to 8 h, maximum 30 mg per kg per day, from three months and over 5 kg: that is 150 to 300 mg per dose for this child. He is drinking and passing urine with no renal impairment, bleeding risk or aspirin-sensitive asthma, so the NSAID is appropriate. Both are given on a scheduled (by-the-clock) basis for established pain, not as-needed. ^{[8] [11]}

3. The opioid layer and its monitoring

If the pain is not controlled, the intravenous morphine dose is 0.1 mg per kg (about 3 mg for a 30 kg child), titrated in small increments to the pain score and the sedation score. For ongoing postoperative pain, patient-controlled analgesia uses a morphine bolus of about 20 micrograms per kg (about 600 micrograms) with a 10-minute lockout, run under the acute pain service. The mandatory monitoring is a sedation score (the primary safety monitor, because sedation precedes respiratory depression), the respiratory rate against the age-normal range, and oxygen saturation, with a documented reassessment. ^{[11] [12]}

4. The over-sedated child

The diagnosis is opioid-induced respiratory depression: a difficult-to-rouse child with a respiratory rate of 10 and a low pain score is in respiratory depression, not well-controlled pain. The immediate management is to stimulate the child, support the airway and breathing, and hold the PCA, then give naloxone titrated to the respiratory rate — not to full reversal. The goal is a breathing child who is still comfortable. Because naloxone's half-life is shorter than morphine's, the child is monitored for recurrence, with repeat boluses or an infusion as required, and the regimen, concentrations and monitoring that allowed the event are reviewed. The defence that should have caught it earlier is a sedation score charted with the respiratory rate. ^[9]