I was about to administer a chemotherapy infusion. The carboplatin dose was double-checked by a co-worker. First, she calculated the patient’s GFR and then the AUC (area under the curve).
Independently, I calculated the GFR and then calculated the AUC using the carboplatin dose calculator I found on the hospital’s online resource. Following those directions, I plugged in the patient’s GFR, serum creatinine, weight, height, etc. My coworker and I came up with the same answer. Whew.
When the IV bag of carboplatin arrived from pharmacy, we reviewed the bag’s label against our calculations, completing the double check. Holy moley! The dose in the IV bag was different from our calculation. The process stopped while I made a phone call to the pharmacist. Here’s what I learned:
“We cap the serum creatinine value at 0.8 and the GFR at 125. Your patient’s creatinine is 0.6, which increases the GFR above the cap. The dose is based on the capped values.”
“Oh,” I replied.
This is what the FDA says about carboplatin dosing:
Based on preliminary communications with the National Cancer Institute/Cancer Therapy Evaluation Program, a potential safety issue with carboplatin dosing has been identified. By the end of 2010, all clinical laboratories in the US will use the new standardized Isotope Dilution Mass Spectrometry (IDMS) method to measure serum creatinine. The IDMS method appears to underestimate serum creatinine values compared to older methods when the serum creatinine values are relatively low (e.g., ~0.7 mg/dL). Measurement of serum creatinine by the IDMS-method could result in an overestimation of the Glomerular Filtration Rate (GFR) in some patients with normal renal function. If the total carboplatin dose is calculated based on IDMS-measured serum creatinine using the Calvert formula, carboplatin dosing couldbe higher than desired and could result in increased drug-related toxicity.
I must have been under a rock when this happened. Using the capped values, we recalculated the same dose as in the IV bag. I administered the carboplatin. Problem solved — or is it?
Afterward, I vaguely recalled an email from pharmacy sometime last year (or maybe it was a few months ago?) explaining the change in carboplatin dosing. That was the entire rollout of this information. Did in-patient nurses receive more information or an in-service? I don’t know.
I applaud pharmacy for initiating a best-practice in medication dosing. I also feel that a significant change such as this requires more than an informal email, and I suspect this happens often to nurses working in hospitals.
Nurses are expected to assess a patient’s understanding of the education we provide. Likewise, significant changes in clinical practice should be coordinated across departments, using nurse educators and managers to assess their nurses’ awareness and understanding.
Have you had similar experiences missing crucial information that was informally communicated?