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Difficulty: HardPharmacological and Parenteral Therapies

An adult client experiencing recurrent seizure activity is admitted to the neurological unit. The client has a single patent 2020-gauge peripheral intravenous catheter infusing 5%5\% dextrose in 0.45%0.45\% sodium chloride at 80 mL/hr80 \text{ mL/hr}. The provider prescribes a stat loading dose of phenytoin 1000 mg1000 \text{ mg} intravenously. The pharmacy delivers the medication diluted in 100 mL100 \text{ mL} of normal saline. What is the safest method for the nurse to administer this medication?

  1. Pause the primary infusion, flush the catheter with normal saline, infuse the phenytoin over 3030 minutes, and flush again with normal saline.Answer
  2. B
    Attach the phenytoin tubing as a secondary piggyback to the Y-site closest to the insertion site while the primary fluid continues.
  3. C
    Program the infusion pump to deliver the entire dose over a 1010-minute period to rapidly achieve therapeutic serum levels.
  4. D
    Delay administration until a second peripheral intravenous catheter can be inserted specifically for the phenytoin infusion.

Answer

The safest method is to pause the primary dextrose infusion, flush the catheter with normal saline, infuse the phenytoin over 30 minutes, and flush again with normal saline.
The correct action is to pause the primary dextrose infusion and flush the line with normal saline before and after administering the phenytoin. Phenytoin is highly incompatible with dextrose-containing solutions and will precipitate if mixed, forming solid crystals in the tubing. Because the medication is prescribed as a stat dose for recurrent seizures, utilizing the existing patent catheter by clearing it with normal saline is the fastest and safest approach. Additionally, administering the dose over 30 minutes ensures the infusion rate remains below the maximum safe limit of 50 mg/min50 \text{ mg/min}.

Step-by-Step Solution

1
Identify the primary fluid composition and check drug compatibility.
The primary fluid contains dextrose, which is highly incompatible with phenytoin.
Mixing phenytoin with dextrose solutions causes immediate crystallization and precipitation in the intravenous tubing.
2
Calculate the safe infusion rate for the prescribed dose.
The maximum safe rate for intravenous phenytoin is 50 mg/min50 \text{ mg/min}. For a 1000 mg1000 \text{ mg} dose, the absolute minimum infusion time is 2020 minutes (1000÷501000 \div 50).
Infusing phenytoin faster than 50 mg/min50 \text{ mg/min} can cause severe cardiovascular toxicity, including hypotension and arrhythmias.
3
Determine the most efficient and safe administration route utilizing existing resources.
The existing line must be cleared of dextrose using normal saline (flush-administer-flush technique).
This prevents precipitation without unnecessarily delaying a 'stat' medication to insert a new catheter.

Key Concept

Phenytoin Intravenous Administration Safety
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Topics

Pharmacological and Parenteral Therapies

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