Abstract 173: Microcirculatory Alterations After Cardiac Arrest Are Worse With Longer Downtime and Are Not detected by Measurement of Blood Pressure
Aim: Abnormalities in microvascular blood flow are of increasing interest during the post-resuscitation phase following cardiac arrest because they may not be detected by macrocirculatory indices, such as arterial blood pressure. The goal of our study was to examine microvascular blood flow using sublingual microscopy in a swine model following prolonged cardiopulmonary arrest (CA).
Methods: In 9 female, isoflurane-anesthetized swine, macro-and microcirculatory metrics were examined at baseline and post-resuscitation after either 10 (CA10; n=3) or 15 minutes (CA15; n=6) of CA. Cardiac output (CO), mean arterial pressure (MAP), arterial lactate concentration (Lac) and mixed venous oxygen saturation (SvO2) were measured before induction of ventricular fibrillation and 5, 15, 30, 60, 120 and 240 minutes after return of spontaneous circulation (ROSC). Concurrently, 20-second clips of the sublingual microcirculation were captured with a non-invasive intravital videomicroscope at five locations per time point. Microvascular blood flow was quantified off-line by determining the microvascular flow index (MFI). For this, the image was divided into four quadrants and blood flow in small vessels in each quadrant was assigned a score of either “0” for absent flow, “1” intermittent, “2” sluggish, or “3” continuous blood flow. The average of MFIs from the five different locations at a given time was calculated and used for analysis.
Results: MFIs were significantly reduced 5 minutes after ROSC in CA10 (p=0.021) and in CA15 (p<0.001) and gradually recovered over the next 4 hours to baseline in CA10 (p=0.887), but not in CA15 (p<0.001). CO, SvO2 and Lac, but not MAP, were abnormal 5 minutes after ROSC and reached baseline 60 minutes after reperfusion in both groups, with the exception of Lac, where baseline levels were not achieved until 120 minutes in CA10, and values remained elevated in CA15 at 240 minutes post ROSC (p<0.001).
Conclusions: Microvascular blood flow abnormalities are evident on microscopy, appear more profound with longer periods of arrest, and may not recover within the first 4 hours after ROSC if downtime is very long. Macrohemodynamic metrics, especially MAP, often fail to reflect the presence of microcirculatory disturbance after cardiac arrest.
- © 2010 by American Heart Association, Inc.