Case
You receive a call from the neonatal intensive care unit (NICU) regarding an ex-34 week premature infant. “I have this 1 week old male infant who is here for a persistent oxygen requirement and feeding issues. The baby was intubated after delivery but now has weaned to 1 liter of oxygen via nasal cannula. The baby has been on parenteral nutrition but is receiving some feeds via nasogastric tube. Because he is on oxygen, he requires monitoring and we have noted extra beats that causes his monitor to alarm. Could you come by and take a look?”
What am I thinking?
Alarms can be the bane of the NICU nurse’s existence. Bedside monitors can alarm for a number of reasons, both medical and nonmedical. Usually, extrabeats on the monitor indicate some form of rhythm change in a newborn, but not always. Sometimes, it is related to an artifact that is picked up as an extrabeat. Most often, I usually think the extra beat is a reflection of a premature beat such as a premature atrial beat that is conducted and causes a change in rhythm. Next, I begin to think about the potential etiologies of that atrial premature beat. Does this baby have a low potassium? Does the baby have an umbilical venous catheter or central line that has moved into the right atrium? Lastly, I consider management that often is noncardiac in nature.
| Differential diagnosis |
|---|
| Likely |
| Atrial premature beat Artifact |
| Possible |
| Ventricular premature beat |
| Rare |
| Congenital heart disease Cardiac tumor |
History and physical
Infants in the NICU, by definition, require intensive care that may lead to a clinical setup for monitoring combined with idiopathic changes. Extrabeats noted on the monitor and causing alarms should be reviewed as to the frequency of these occurrences. Additionally, it is important to identify specific time frames where the extra beats are noted (e.g., after medication or after feedings). Given the possible etiologies for premature beats, further history into potential electrolyte disturbances or presence of a newly placed central line should be obtained.
Physical exam should focus on auscultation of changes in rhythm associated with the extra beats noted on the monitor. On some occasions, the change in monitor is not reflected by a change in auscultation but more accurately reflects an artifact due to movement such as with hiccoughs. Auscultation should also focus on the presence of murmurs for congenital heart disease or the exceedingly rare “tumor plop” sound of an atrial myxoma. The presence of any central venous catheters should also be noted.
Diagnostic tests
The first step in the investigation is a review of the monitor. As mentioned earlier, the artifact may lead to the alarm based on the monitor’s interpretation of patient movement as a cardiac signal. A useful tip to determine if the signal is cardiac in origin or artifact is to determine the impact on the underlying rhythm. For true cardiac signals, the underlying rhythm is most often impacted resulting in a change in cadence. For artifact, the cadence or rate of the rhythm from beat to beat is unchanged. On occasion, the artifact can be seen transposed on top of a true cardiac signal without any change in underlying rhythm (see Fig. 2.1 ).
