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INTRODUCTION

FOCUS POINTS

  1. Body composition is different in children than in adults, with children having a higher proportion of total body water than fat and muscle.

  2. Egg allergy does not preclude propofol use (egg lecithin) because the usual allergy is due to egg albumin.

  3. Prolonged propofol infusions (24 hours) can lead to propofol infusion syndrome (PRIS), which is a syndrome defined by metabolic acidosis, rhabdomyolysis, lipemia, and hepatomegaly.

  4. Among the hypnotics, only ketamine has both amnestic and analgesic properties and is considered the most complete anesthetic.

  5. Ketamine should be used with caution in patients that are sympathetically depleted (ICU patients) because it has direct myocardial depressant effects.

  6. Etomidate provides hemodynamic stability upon administration but can cause adrenal insufficiency even after a single dose.

  7. Midazolam is the most common premedication in adults intravenously, and in children orally.

  8. Methohexital can be used for maintenance of anesthesia instead of propofol in patients with mitochondrial disorders. It should be used with caution in patients with seizure history.

Hypnotics are drugs that have dose-dependent effects extending from reduction of anxiety to a sleep-like state. Due to differences in drug distribution between adults and children, dosing needed to exert similar clinical effects may vary. Parameters such as body composition, metabolism, regional blood flow, and clinical state affect distribution and thus effect.

Body composition is different in children than in adults, with children having a higher proportion of total body water than fat and muscle. Total body water is significantly larger in neonates and infants, especially preterm infants. Preterm infants and neonates have other differences in metabolism when compared to older children and adults. They have immature hepatic and renal function and decreased protein binding of drugs.

Regional blood flow plays a significant role in the effects of hypnotic drugs. The brain, heart, and liver are the main organs that first receive the drug. The next group to receive blood flow is the less perfused muscle group. The last group made up of the poorly perfused tissues is fat. Fat in turn acts as a reservoir and can release the drug into the bloodstream, maintaining higher drug concentration levels and prolonging drug effects.

As children get older, the renal and hepatic function increases as a larger fraction of cardiac output goes toward the liver and kidneys. Thus, the half-life of many medications in children over 2 years is shorter than in adults.

Sicker children especially in states of hemodynamic instability may need to have drug dosages reduced and/or given at a slower rate to prevent further cardiovascular deterioration.

As clinicians became more experienced with hypnotic drugs, more drug combinations have been considered to both decrease individual drug doses and improve side effect profile of individual drugs. An example of this is the use of ketamine along with propofol (“ketofol”).

PROPOFOL

Propofol is the ...

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