Transcutaneous Pacing: Part 3
Complete Heart Block with Altered Mental Status
Josh Kimbrell, NRP
@joshkimbre
Judah Kreinbrook, EMT-P
@JMedic2JDoc
This is the third installment of a blog series showing how transcutaneous pacing (TCP) can be difficult and how you can improve your skills. We will be using information from different cases where paramedics attempted TCP in the field. Details are edited and redacted to preserve patient anonymity.
Paramedics arrived at a home to find an elderly male with profound altered mental status. Per family, the patient has limited verbal communication and is unable to move himself from bed at baseline. He has a past medical history of HTN, HLD, DM, seizures, and ESRD with a regular hemodialysis schedule (per family, he adheres to his schedule meticulously). He was hospitalized one week prior to EMS arrival for a seizure with no other recent illnesses or injuries.
Paramedics note that he is only responsive to deep painful stimuli with shallow ventilations. Rhonchi are auscultated bilaterally. His skin is pale, dry, and cool to the touch in peripheral extremities with a warm torso. Bradycardia with “borderline hypotension” as described by the paramedics (BP 104/40) with 3-lead ECG as seen in Figure 1 were found.
Figure 1: Paramedics correctly note that this is a Complete Heart Block.
Suddenly, the patient deteriorates and breathing becomes increasingly slow and shallow with a dropping pulse oximetry into the “high 80s.” ETCO2 applied via nasal cannula shows values between 20-25mmHg. Ventilations were applied via BVM with NPA in place. IV access was obtained and Atropine 1 mg administered IV. Transcutaneous pacing rate was set to 80 bpm with a slow increase in current. The crew recognizes the image in Figure 2 as not electrical capture and increases the current.
Figure 2: Current started at 50 ma without electrical capture, with several native beats signified by the triangle annotated by the cardiac monitor.
Paramedics increase the current slowly over nearly 3 minutes to 100ma where a documented mechanical capture (pulse palpation site not specified) was noted. The ECG strip shown in Figure 3.
Figure 3: Wide QRS complexes with visible T waves can be seen after each pacer spike. While pulse oximetry is applied, the paramedics do not see it on the monitor because the setting is looking at three ECG leads rather than including ETCO2 and SPO2.
After TCP, the paramedics attempt to intubate. 100mg of Ketamine is administered in an attempt to obtain advanced airway placement but the persistent gag reflex prevents successful intubation. Under physician direction, paramedics administer an additional 100mg Ketamine but are unsuccessful in obtaining an advanced airway (note: NMBA is not allowed to be administered by paramedics in this system). BVM was continued via NPA and the patient transported to the closest hospital. Blood pressures after pacing initiation improve (125/80, 130/66, 150/113) and improvement in ETCO2 (30-32mmHg). Paramedics shift the monitor setting to show ETCO2 and pulse oximetry, as seen in Figure 4.
Figure 4: True electrical capture is seen with synchronized pleth waves from the pulse oximeter.
Unfortunately, no information is available about the in-hospital portion of this patient’s care.
Several learning points are present here:
This crew spotted “false electrical capture,” when ECG artifacts appear similar to the true “QRS-like” electrical capture with a broad T wave in TCP. This recognition is crucial to success, as in many cases TCP is unsuccessful with proper positioning and high currents; a study in an electrophysiology lab demonstrated that even with pad placement in the AP position, approximately 20% will not achieve capture.
Notice, in this case, how similar the Figure 4 ECG looks to phantom complexes. This demonstrates the difficulty of ECG interpretation in these patients and how important it is to use different methods to confirm successful TCP.
Even though this crew had the pulse oximeter on, the waveform was not visible until they adjusted the monitor settings. Know your default settings for your monitor well and how to change them.
Visualizing pleth waves and increased ETCO2 values were key here as we know that palpable pulses are rather unreliable (in our recent study on false electrical capture all patients had a palpable pulse regardless of false versus true electrical capture).
