The more the better? Cardiac output monitoring during cardiopulmonary rescuscitation Free

I read with great interest the recent work by Dr. Twomey and coworkers comparing internal vs. external cardiopulmonary resuscitation [1].

I strongly believe that the authors touch an important, albeit somewhat neglected theme.

Based on the current published papers, open chest massage seems to achieve higher cardiac indices with a twofold increase in contrast to closed chest massage (0.6 vs. 1.3 l/min/m²). In line, coronary perfusion pressure is increased [2]. However, one has to take into account that a total number of 11 patients were included in that study with it certain limitations. Furthermore, the method used for cardiac output measurement in this 42-year-old study may not necessarily be as accurate and precise as current gold standard therapy. The Swan-Ganz catheter, which is currently appreciated as the gold-standard therapy for clinical cardiac output measurement, was first described five years after the aforementioned study focusing the cardiac index during either open or closed chest compression [3].

Cardiac output/index monitoring during open or closed chest compression in resuscitation necessitates a continuous measure. It is preferable to use a beat-by-beat monitoring tool in this regard to obtain the appropriate stroke volumes of each chest compression rather than a mean of stroke volumes over a given time duration, such as 2 min.

A non-invasive cardiac output monitor appears to be attractive in this regard. An ultrasonic cardiac output monitor (USCOM) has been found to be at least as accurate as the current gold standard monitoring tool, the Swan-Ganz catheter [4]. It allows beat-by-beat stroke volume determination by a suprasternal approach focusing the blood column in the ascending aorta. During cardiopulmonary resuscitation, a high normal cardiac output of 5.75 l/min (cardiac index 3.12±1.67 dyne×s×cm⁻⁵) is achievable with paramedics performing the closed chest compression [5]. The range of cardiac output measured in 6 cardiopulmonary closed chest resuscitation patients was 2.7 to 12 l/min (1.2 dyne×s×cm⁻⁵ to 5.7 dyne×s×cm⁻⁵). However, the level of cardiac output/Index did not correlate in those six patients with the establishing of sustained circulation. Actually, the 2/6 patients arriving at the hospital with circulation had the lowest cardiac outputs (2.7 l/min, 66-year-old male and 3.5 l/min, 90-year-old female) in comparison to the 4 other patients, where cardiopulmonary resuscitation failed (4.8–12 l/min, 33–87 years). Whether this discrepancy in survival rate is based on undetermined factors in that study which might have contributed to the outcome is unclear. In other words, whether a higher cardiac output/index is mandatory to be associated with a better outcome, e.g. survival, has to be studied in further studies.

References