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Difficulty: Very hardPharmacological and Parenteral Therapies

A client with severe diabetic ketoacidosis (DKA) and hyperkalemia (serum potassium 7.2 mEq/L7.2\text{ mEq/L}) is receiving continuous intravenous (IV) infusions through a triple-lumen central venous catheter (CVC). The infusions are as follows:

- Proximal lumen: Regular insulin at 0.1 units/kg/hr0.1\text{ units/kg/hr} in 0.9% sodium chloride.
- Medial lumen: Isotonic 0.9% sodium chloride at 150 mL/hr150\text{ mL/hr}.
- Distal lumen: Sodium bicarbonate 150 mEq150\text{ mEq} in 1000 mL1000\text{ mL} of 5% dextrose in water (D5W) at 100 mL/hr100\text{ mL/hr}.

The client's cardiac monitor suddenly displays widening QRS complexes. The healthcare provider verbally prescribes an emergent IV bolus of 10%10\% calcium gluconate (1000 mg1000\text{ mg}) to stabilize the myocardium. The client currently has no peripheral IV access. Which of the following actions is the most appropriate for the nurse to take?

  1. A
    Pause the sodium bicarbonate infusion, thoroughly flush the distal lumen with 0.9% sodium chloride, administer the calcium gluconate, flush again, and resume the bicarbonate.
  2. Administer the calcium gluconate via the injection port of the medial lumen's IV tubing closest to the client, allowing the 0.9% sodium chloride to act as a carrier fluid.Answer
  3. C
    Administer the calcium gluconate via the injection port of the proximal lumen's IV tubing, pausing the regular insulin infusion only during the active IV bolus.
  4. D
    Delay the administration and immediately establish a new peripheral IV line, because infusing calcium and sodium bicarbonate concurrently through the same CVC will cause precipitation.

Answer

The most appropriate action is to administer the calcium gluconate via the medial lumen, utilizing the continuous 0.9% sodium chloride as a compatible carrier fluid.
The correct action is to administer the calcium gluconate via the medial lumen. The medial lumen contains 0.9% sodium chloride, which is fully compatible with calcium gluconate. Crucially, because the separate lumens of a CVC act as independent catheters with staggered exit ports in the superior vena cava, the calcium exiting the medial port will instantly dilute in the rapid central venous blood flow, preventing it from precipitating with the sodium bicarbonate exiting the distal port. Using this lumen ensures immediate, safe administration without interrupting necessary ongoing therapies or risking an accidental bolus of insulin.

Step-by-Step Solution

1
Analyze the clinical emergency.
The client has hyperkalemia with widening QRS complexes, indicating impending ventricular fibrillation.
Immediate administration of calcium gluconate is required to stabilize the myocardial threshold. Delaying for peripheral IV access is contraindicated.
2
Evaluate the compatibility of the prescribed medication with the current infusions.
Calcium gluconate is highly incompatible with sodium bicarbonate (forms a chalky precipitate). It is compatible with 0.9% sodium chloride.
Identifying chemical incompatibilities prevents catastrophic line occlusion and embolization of precipitates.
3
Assess the multi-lumen CVC physiology and existing infusions.
The distal lumen has bicarbonate, the proximal has a high-alert insulin drip, and the medial has compatible normal saline. Separate CVC lumens act as completely independent IV lines.
Because CVC lumens exit at different points in the high-volume superior vena cava, incompatible drugs will instantly dilute in the blood without precipitating, eliminating the need for separate catheter insertion sites.
4
Select the safest lumen for IV push administration.
The medial lumen is selected.
It avoids mixing with bicarbonate (distal) and avoids flushing the dead space of the insulin line (proximal), which would cause a dangerous hypoglycemic bolus.

Key Concept

Multi-lumen central venous catheters (CVCs) function as completely independent intravenous lines, safely allowing the concurrent infusion of physically incompatible medications. Furthermore, medications should never be pushed through the tubing of a continuous high-alert medication due to the risk of delivering an unintended bolus from the tubing's dead space.
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Topics

Pharmacological and Parenteral Therapies

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