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Difficulty: HardPharmacological Therapies

A practical nurse is preparing to administer 10 units of regular insulin and 20 units of NPH insulin subcutaneously to a client with diabetes mellitus. Arrange the steps for preparing the mixed insulin dose in the correct chronological order.

  1. 1Roll the vial of NPH insulin between the palms to mix the suspension.
  2. 2Inject 20 units of air into the NPH insulin vial and withdraw the needle.
  3. 3Inject 10 units of air into the regular insulin vial and leave the needle inserted.
  4. 4Invert the regular insulin vial and withdraw 10 units of regular insulin.
  5. 5Insert the needle into the NPH insulin vial and withdraw 20 units of NPH insulin.

Answer

The correct chronological sequence is to roll the NPH vial, inject air into the NPH vial, inject air into the regular insulin vial, draw the regular insulin, and finally draw the NPH insulin.
The correct sequence for mixing insulins follows the standard 'clear before cloudy' principle to prevent contaminating the fast-acting (clear) insulin with the intermediate-acting (cloudy) insulin. First, the NPH (cloudy) vial is gently rolled between the palms to mix the suspension without creating bubbles. Next, air equal to the prescribed dose is injected into the NPH vial to prevent a vacuum, and the needle is immediately removed. Then, air equal to the prescribed dose is injected into the regular (clear) insulin vial, and the needle is left in place. The vial is inverted to draw the regular insulin first. Finally, the needle is inserted back into the NPH vial to gently draw the prescribed dose, bringing the total volume in the syringe to the combined ordered amount.

Step-by-Step Solution

1
Roll the NPH insulin vial.
The cloudy insulin suspension is thoroughly mixed without forming air bubbles.
NPH is a suspension where particles settle at the bottom. Rolling ensures an accurate dose, whereas shaking creates bubbles that alter the drawn volume.
2
Inject 20 units of air into the NPH insulin vial.
Pressure is equalized inside the NPH vial.
Injecting air prevents a vacuum from forming. The needle is withdrawn without touching the fluid to keep the needle free of intermediate-acting insulin.
3
Inject 10 units of air into the regular insulin vial.
Pressure is equalized inside the regular insulin vial.
Air equalizes pressure to make drawing easier. The needle is left inside to immediately begin drawing the regular insulin.
4
Withdraw 10 units of regular insulin.
The syringe contains exactly 10 units of clear regular insulin.
Clear insulin must be drawn first to prevent accidental contamination of the rapid-acting insulin vial with intermediate-acting NPH insulin.
5
Withdraw 20 units of NPH insulin.
The syringe contains a total combined volume of 30 units of insulin.
NPH is drawn last. Careful withdrawal is required because any excess cannot be pushed back into the vial without contaminating it with regular insulin.

Key Concept

Safe Preparation of Mixed Insulins (Clear Before Cloudy)
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Topics

Pharmacological Therapies

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