Medications and ECMO:
There is a paucity of data regarding the exact effect that the ECMO circuit has on the pharmacokinetics of different medications. In general, we do know that:
- The presence of the circuit increases the effective volume of distribution (Vd) of most medications, so it will take a higher dose to achieve the same plasma concentration.
- Certain drugs are actually sequestered in the PVC tubing of the ECMO circuit, which means it will take a longer time to reach the desired plasma concentration, and the drugs will leak out of the tubing after the infusion has stopped.
- When a patient is decannulated, the effective plasma concentrations of the drugs become much higher because of the absence of the circuit.
- The rate of clearance of drugs on ECMO is reduced, so their effects will take longer to wear off.
Sedatives
- In general it has been observed that patients on ECMO need higher doses of sedating medications to produce the same effect.
- Dosing requirements of benzodiazepines and narcotics tend to increase with time.
- When a patient is decannulated, the pharmacokinetics of sedating medications will be changed, so adjustments are often necessary.
Antibiotics
- Because of the pharmacokinetic changes associated with ECMO, therapeutic drug monitoring should be used whenever possible.
- From the data available, it appears that vancomycin loading doses should be increased slightly (20-30 mg/kg) to account for the larger Vd.
- Voriconazole dosing should be increased initially because of sequestration into the circuit, but monitoring should be employed to avoid toxicity.
Other Medications
- Furosemide (Lasix) has shown to be sequestered in the ECMO circuit, so larger than expected dosing should be expected.
- Heparin appears to be eliminated by the ECMO circuit itself, as well as blood components in the circuit, and so frequent dosing adjustments should be expected.
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