A client is ordered to receive insulin lispro (Humalog) at mealtimes. When should the nurse instruct the client to administer the medication?

Choice A rationale:

COPD (Chronic Obstructive Pulmonary Disease) is a chronic lung disease that causes airflow obstruction. While labetalol can cause some bronchoconstriction, it is generally considered safe for use in patients with COPD. However, it's essential to monitor respiratory status closely, especially in those with severe COPD.

Choice B rationale:

Narrow-angle glaucoma is an eye condition characterized by increased intraocular pressure (IOP) due to impaired drainage of aqueous humor. Labetalol can exacerbate this condition by further increasing IOP through its beta-blocking effects. This can lead to acute angle-closure glaucoma, a medical emergency that can result in permanent vision loss.

Specific mechanisms by which labetalol can increase IOP:

Reduced aqueous humor production: Beta-blockers like labetalol can decrease the production of aqueous humor, the fluid that maintains eye pressure. While this might seem beneficial, a significant reduction can lead to anterior chamber shallowing, which can mechanically block the drainage angle and trigger angle closure.

Impaired uveoscleral outflow: Beta-blockers can also impair the uveoscleral outflow pathway, an alternative route for aqueous humor drainage that becomes more important in glaucoma patients. This can further contribute to IOP elevation.

Vasoconstriction of ciliary blood vessels: Labetalol's alpha-blocking effects can cause vasoconstriction of the ciliary blood vessels, which supply blood to the ciliary body responsible for aqueous humor production. This can reduce blood flow and indirectly hinder aqueous humor drainage.

Pupillary dilation: Beta-blockers can cause pupillary dilation, which can mechanically narrow the anterior chamber angle and obstruct aqueous humor outflow.

Therefore, labetalol is generally contraindicated in patients with known narrow-angle glaucoma.

Choice C rationale:

Hypertension (high blood pressure) is one of the primary indications for labetalol. It is an effective antihypertensive medication that works by blocking beta receptors, leading to decreased heart rate, contractility, and blood pressure.

Choice D rationale:

Tachycardia (fast heart rate) can also be treated with labetalol due to its beta-blocking effects. It helps to slow down the heart rate and restore a normal rhythm.

Choice A rationale:

Mixing insulins in a vial is generally not recommended unless specifically instructed by the healthcare provider. It can alter the effectiveness of the insulins and increase the risk of dosage errors.

Premixed insulins, which are already combined in a specific ratio, are available if a combination of insulins is needed.

However, in this case, the patient is instructed to administer regular and NPH insulin separately, indicating that they should not be mixed in a vial.

Choice B rationale:

Insulin can be injected into various subcutaneous sites, including the abdomen, thighs, upper arms, and buttocks.

There is no specific requirement to inject mixed insulin into the buttocks only.

The choice of injection site can be based on individual preferences, absorption rates, and the presence of lipohypertrophy (thickening of the subcutaneous tissue due to repeated injections).

Choice C rationale:

Drawing up NPH insulin first could lead to contamination of the regular insulin vial with NPH insulin.

NPH insulin is a suspension, and drawing it up first could introduce some of its particles into the regular insulin vial, potentially altering its absorption and action profile.

Choice D rationale:

It's crucial to draw up the regular insulin first to prevent contamination of the regular insulin vial with NPH insulin. The following steps outline the correct procedure:

Wash hands thoroughly with soap and water.

Inspect the insulin vials for clarity, expiration date, and any damage.

Roll the NPH insulin vial gently between the palms to resuspend the insulin particles (if applicable). Wipe the rubber stoppers of both vials with an alcohol swab.

Using a sterile syringe, withdraw air into the syringe equal to the amount of regular insulin to be drawn.

Inject the air into the regular insulin vial, keeping the needle tip above the fluid level to avoid creating bubbles. Invert the regular insulin vial and withdraw the prescribed dose of regular insulin.

Without injecting air into the NPH insulin vial, withdraw the prescribed dose of NPH insulin. Administer the insulin as directed, using proper injection technique.