Use of Femoral Arterial Doppler Velocity to Detect Perfusing Pulses During Cardiac Arrest

Introduction: Manual pulse detection is inaccurate in cardiac arrest(CA) and Doppler ultrasound may detect blood flow without an adequate perfusion blood pressure (pseudo-pulseless electrical activity). The purpose of this study is to assess whether maximum femoral arterial velocity during a pulse check is correlated with arterial line systolic blood pressure (SBP) and whether it can be used to accurately identify a SBP of ≥60mmHG. Methods: This is a prospective study of CA patients at a quaternary care Emergency Department. During a pulse check, a linear ultrasound was placed at the common femoral artery and the presence or absence of an arterial Doppler waveform, the associated maximum velocity value, and arterial line SBP were recorded simultaneously. The correlation between SBP and maximum waveform velocity was assessed. Arterial SBPs were dichotomized as <60mmHG or ≥60mmHg, as this was deemed as an adequate perfusion pressure, and a receiver operator characteristic curve analysis was performed to determine optimal cutoff value of maximum velocity associated with SBP ≥60mmHG. Sensitivity (Sn), specificity (Sp), and accuracy (Acc) of manual palpation and femoral artery pulse wave doppler for detection of SBP ≥60mmHg were calculated. Results: A total of 51 patients and 183 pulse checks were analyzed. There was a strong correlation between arterial line SBP and maximum waveform velocity (Spearman correlation coefficient: 0.92; p<0.001). The optimal cutoff value of waveform velocity associated with a SBP ≥60mmHG was 20 cm/second (Sn: 0.89; specificity: 0.94; area under the curve: 0.98) with an Acc of 0.92. To detect SBP ≥60mmHg, manual palpation had a Sn of 0.45, Sp of 0.82, and Acc of 0.67 McNemar's test showed that Sn (p<0.001), Sp (p=0.009), and Acc (p<0.001) was significantly higher for doppler ultrasound >=20cm/sec compared with manual palpation. Conclusion: In this study, during a pulse check, patients with a femoral arterial doppler waveform with a maximum velocity greater than 20cm/sec had a high probability of having a SBP ≥60mmHg, and improved Sn, Sp and Acc over manual palpation. The results demonstrate femoral arterial doppler maximum velocity is an accurate and objective tool to determine the presence of a pulse with adequate perfusion pressures.