The letters QTc probably
would not register as anything besides letters to most people. However, I
continue to learn and be amazed at how important this is to clinical nursing.
As a cardiac nurse especially, I must be familiar with this term.
In clinical practice alone, a QT interval measurement is meaningless
because if its negative correlation with heart rate. For it to be
meaningful, it must be independent of the patient's underlying heart rate.
A rate formula is used to calculate what that is the corrected QT
interval, also know as QTc interval. The formula looks like this:1
Comparing
multiple QT intervals overtime is especially important after administration of
drugs known to prolong the QT interval.
When potentially proarrhythmic drugs are being administered, a baseline
QT/QTc interval should be established before administration of the first dose.
Depending on the drug's risk, the ongoing QT/QTc monitoring may be as frequent
as every 20 minutes after the dose is administered, or every 4, 8, or 12 hours.
The upper 99th percentile limit of QTc intervals is 470 ms for men and
480 for women. A QTc that is prolonged greater than 60 ms from baseline
after QT drug administration and/or a QTc interval greater than 500 ms should
be considered abnormal and necessitates immediate assessment and evaluation.2
A study performed by the American Heart association reported that with increasing baseline QTc interval,
the risk of death systematically increases.3
You as a nurse are a great clinician to monitor for and detect
QT-interval abnormalities. Always remember that you are your patients'
advocate! Make sure you understand each medicine you administer, as well
as side effects and contraindications.
References
1. British Journal of Anesthesia. (2013). Retrieved from http://ceaccp.oxfordjournals.org/content/8/2/67/F2.expansion
2. Pickham, D. (2013) Understanding and documenting QT intervals. Critical Care Nurse, 33(4), 73-75.
3. Brendorp, B., Elming, H., Jun, L., Kober, L., Malik, M., Jensen, G.B., & Torp-Pedersen, C. (2001). QTc interval as a guide to select those patients with congestive heart failure and reduced left ventricular systolic function who will benefit from antiarrhythmic treatment with dofetilide. American Heart Association Circulation, 103, 1422-1427. doi: 10.1161/01.CIR.103.10.1422
No comments:
Post a Comment