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Difficulty: HardPharmacological and Parenteral Therapies

A client is admitted to the emergency department in status epilepticus. The healthcare provider prescribes a loading dose of phenytoin 1,000 mg intravenously STAT. The client has a single 20-gauge peripheral intravenous (IV) catheter, which is currently infusing a primary solution of 5% Dextrose in Water (D5W) at 100 mL/hr. Which sequence of actions by the nurse demonstrates safe administration of this medication?

  1. Pause the primary D5W infusion, flush the IV catheter with 0.9% sodium chloride, and administer the medication using an infusion pump over 20 minutes.Answer
  2. B
    Inject the medication via rapid IV push into the lowest Y-site of the primary D5W tubing to ensure immediate delivery to the central circulation.
  3. C
    Stop the D5W infusion, flush the line with 0.9% sodium chloride, and manually administer the medication via IV push over 5 minutes.
  4. D
    Request the pharmacy to dilute the medication in a 250 mL bag of 5% Dextrose in Water (D5W) and infuse it as a secondary piggyback over 45 minutes.

Answer

The correct action is to pause the primary D5W infusion, thoroughly flush the intravenous catheter with 0.9% sodium chloride, and administer the phenytoin over at least 20 minutes.
Phenytoin is chemically incompatible with all dextrose-containing solutions and will immediately form a solid crystal precipitate if mixed. The nurse must pause the D5W and thoroughly flush the line with 0.9% sodium chloride (normal saline) before and after administration. Additionally, intravenous phenytoin carries a critical warning for severe hypotension and cardiac arrhythmias if administered too rapidly. The absolute maximum safe infusion rate is 50 mg/min. For a 1,000 mg loading dose, the minimum administration time must be calculated: 1,000 mg ÷ 50 mg/min = 20 minutes. The use of an electronic infusion pump ensures this safe rate is strictly maintained.

Step-by-Step Solution

1
Identify the chemical compatibility between the prescribed medication (phenytoin) and the infusing primary fluid (D5W).
Phenytoin is highly alkaline and completely incompatible with dextrose. It will instantly precipitate.
To determine if the medication can be administered concurrently or if the line must be cleared with a compatible solution.
2
Determine the appropriate diluent or flush solution required to safely administer phenytoin.
0.9% sodium chloride (normal saline) is the only compatible crystalloid solution for phenytoin administration.
To clear the IV catheter of any dextrose and provide a safe, compatible medium for the anticonvulsant.
3
Calculate the minimum safe administration time based on the maximum allowable intravenous infusion rate for phenytoin.
Maximum rate is 50 mg/min. For a 1,000 mg dose: 1,000 mg ÷ 50 mg/min = 20 minutes.
Intravenous phenytoin carries a black box warning for severe hypotension and life-threatening cardiac arrhythmias if infused too rapidly.
4
Select the option that correctly combines flushing the incompatible D5W with normal saline and administering the medication over the required minimum time.
The option stating to pause D5W, flush with normal saline, and infuse over 20 minutes is the only safe clinical action.
It successfully prevents chemical precipitation and avoids life-threatening rate-related cardiovascular adverse effects.

Key Concept

Safe parenteral administration of phenytoin requires avoiding all dextrose-containing solutions due to chemical precipitation, and strictly limiting the intravenous infusion rate to a maximum of 50 mg/min to prevent cardiovascular toxicity.
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Topics

Pharmacological and Parenteral Therapies

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