Intravenous

IV drugs are distributed first to the vessel-rich group, just as inhalational anesthetics are and then to the muscle, vessel-poor group, and fat groups. The primary anesthetic effect occurs when the anesthetic reaches an adequate brain concentration; it is then redistributed to other tissues and metabolized to terminate its action.

Propofol is the most commonly used IV induction agent in children. Propofol is an integral part of total intravenous regional anesthesia (TIVA) for maintenance of anesthesia in children undergoing medical or radiologic evaluations and surgery.
1. Propofol is the only anesthetic that has antinausea properties that may be exploited for use in children with histories of nausea and vomiting or who are undergoing emetogenic surgery.
2. Although propofol is used for both sedation and general anesthesia, long-term sedation in infants and children is not recommended with propofol after reports of unexpected death during propofol sedation with >4 mg/kg/hr for >48 hours.
Ketamine is a phencyclidine derivative that offers enormous flexibility in the clinical care of children. This anesthetic can be used as a premedication (orally, nasally, rectally, or intramuscularly [IM]), a general anesthetic induction agent (IV or IM) and maintenance agent as an infusion, as a sedative (IV or IM), or as a neuraxial analgesic (caudal/epidural).
Neuromuscular Blocking Drugs. With standard twitch devices readily available, every child who receives a muscle relaxant should be assessed for twitch response before attempting to antagonize the neuromuscular blockade. The role of neuromuscular agents in children has diminished with the demise in routine use of succinylcholine and the adoption of propofol as the adjunctive medication to facilitate tracheal intubation after induction of anesthesia with sevoflurane.
1. Succinylcholine is the only depolarizing muscle relaxant in clinical practice and remains the agent that provides the most rapid onset and offset of paralysis without additional medications to recover the normal twitch response.
  1. The IV dose of succinylcholine is 3 to 4 mg/kg in neonates and infants, 2 mg/kg in children, and 1 mg/kg in adolescents. The larger dose requirement with decreasing age has been attributed to the larger volume of distribution in younger infants.
  2. Side Effects. The salient side effects associated with succinylcholine are arrhythmias (most notably bradycardia), rhabdomyolysis (with hyperkalemia and myoglobinuria), raised intraocular pressure, fasciculations, and malignant hyperthermia.
2. Rocuronium. The potency of rocuronium is greatest in infants, least in children, and intermediate in adults (ED₉ ₅ in infants is 0.25 mg/kg and in children, 0.4 mg/kg).
  1. In healthy children during sevoflurane anesthesia, 0.3 to 0.4 mg/kg of rocuronium provides suitable intubating conditions in 2 to 3 minutes and permits antagonism within 20 minutes. Twice the ED₉₅ or 0.6 mg/kg IV of rocuronium, provides relaxation in 1 to 1.5 minutes.
  2. At three to four times ED₉₅, 0.9 to 1.2 mg/kg of IV rocuronium yields similar intubating conditions to succinylcholine within 60 seconds and may be used for rapid sequence induction (RSI), although recovery may be markedly prolonged.
3. Neostigmine. Antagonizing neuromuscular blocking agents is recommended in infants and children when extubation is planned, provided the time interval from the last dose has not exceeded 2 hours. (The train-of-four should be ≥0.9 before the trachea should be extubated.)
  1. The dose of neostigmine in infants and children is 30% to 40% less than that in adults, or 20 to 40 µg/kg, which should be administered when at least one twitch is present in the train of four. If recovery of neuromuscular blockade is incomplete, repeat doses of neostigmine may be administered up to 70 µg/kg.
  2. Neostigmine should be preceded by an anticholinergic, 20 µg/kg of atropine, or 10 µg/kg of glycopyrrolate, to minimize the effect of neostigmine on the nicotinic receptors.
4. Sugammadex is a cylindrical oligosaccharide that uniquely binds rocuronium (and to a lesser extent vecuronium) to eliminate its activity. The rocuronium–sugammadex complex is excreted unchanged in the kidney.
Opioid use in infants and children has increased dramatically in the past few decades in response to recognition that children experience pain and that pain adversely affects the speed and quality of recovery.
1. Morphine. In children, perioperative analgesia is accomplished with intraoperative IV doses of 50 to 100 µg/kg and postoperative doses of 50 µg/kg morphine. Morphine may also be administered via the caudal/epidural route (25–50 µg/kg provides prolonged analgesia).
2. Fentanyl is the most widely used intraoperative analgesic in children (used via the IV, IM, oral, intranasal, and caudal/epidural routes).
3. Remifentanil is a unique µ-receptor opioid that undergoes spontaneous degradation in blood by tissue esterases, with an elimination half-life of approximately minutes that is independent of the duration of infusion (administered as a continuous infusion). The infusion rate for remifentanil ranges from 0.05 to 0.25 µg/kg/min with the dose adjusted according to the presence of concomitant medications (inhalational anesthetics).
4. Codeine has been the mainstay of postoperative analgesia in children for decades.
  1. The analgesic effect of codeine depends on its conversion to morphine and possibly to hydrocodone. Because this conversion depends on CYP450 2D6, polymorphisms of this enzyme may produce enormous variability in the analgesia from this drug ranging from no analgesia to an opioid overdose.
  2. Use of codeine is under increasing scrutiny because of these polymorphisms and the potential extreme responses.
Nonopioid Analgesics
1. Acetaminophen is a nonsteroidal analgesic/antipyretic that has been an effective supplement in children.
  1. Acetaminophen has no anti-inflammatory properties and is free of platelet inhibiting properties.
  2. Oral doses of 10 to 15 mg/kg or rectal doses 30 to 40 mg/kg yield adequate blood concentrations. Absorption after oral administration is rapid (~10–15 minutes), but after rectal administration, it is slow and variable (1–2 hours).
2. Ketorolac (0.5 mg/kg) is the only parenteral nonsteroidal anti-inflammatory (NSAID) medication available for use in children. It possesses anti-inflammatory and analgesic properties for mild to moderate perioperative pain, and similar to other NSAIDs, it also inhibits platelet adhesion by reducing the synthesis of thromboxane.
3. Diclofenac is almost twice as effective for acute pain than acetaminophen for the treatment of acute pain during and after surgery. (The IV dose is 0.3 mg/kg, and the oral dose is 1 mg/kg.)

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