Pulmonary collapse alone provides effective de-airing in cardiac surgery: a prospective randomized study

A routine de-airing method for total endoscopic robot-assisted mitral valve repair

Intraoperative water testing is essential for assessing mitral valve morphology and degree of residual mitral regurgitation during mitral valve repair. However, in some cases, evacuating intracardiac air is challenging. Herein, we report the routine de-airing method during total endoscopic robot-assisted mitral valve repair at our institute and discuss its effectiveness. In brief, our de-airing methods involve the following steps: after restricting the blood flow of the cardiopulmonary bypass, intracardiac air was pushed out into the pulmonary veins by drawing blood from the right ventricle. The left atrium, left ventricle, and ascending aorta were filled with blood to remove air from the root cannula. Retrograde blood flow from the coronary sinus was used to remove air from the coronary arteries. At 10 min after cardiopulmonary bypass weaning, transesophageal echocardiography revealed that residual intracardial air was absent in 99% of patients in all three chambers (ascending aorta, left atrium, and left ventricle).

"De-airing" in open heart surgery: report from the CVSAP nation-wide survey and literature review

Since the beginning of cardiac surgery, retained intracardiac air has been an important problem. While transesophageal echocardiography enabled to visualize the air and de-airing procedures have been routinely done, they appear to vary much among institutions not necessarily based on firm scientific evidence. Thus, "de-airing" was chosen as the theme of 2016 CVSAP (cardiovascular surgery and anesthesia and perfusion) symposium and a nation-wide questionnaire survey was carried out prior to it. This paper reports on its results and illustrate "the best of de-airing" based on literature review. The collection rate of the questionnaire survey was 77.9% (278/357) and 83.3% (85/102) from the major institutions of surgeons and anesthesiologists, respectively. More than 90% of both consider de-airing as important, since adverse events of air embolism were actually encountered including critical ones. Most routinely performed de-airing procedures are posture change, lung inflation and aspiration through the vent cannulae. Direct aspiration is performed in one-third of institutions. Carbon dioxide insufflation is performed in 82.5% of institutions (mostly 2-3 L/min). However, not a few surgeons are skeptical for its significance. While many surgeons are grateful for collaboration by anesthesiologists, some expect more information sharing between them. They also expect that clinical engineers understand "de-airing" better and operate the extracorporeal circulation system appropriately to avoid an occurrence of undesirable event. Some surgeons anticipated a convenient device for de-airing. Furthermore, some questions to be solved in the future were raised, including how meticulously the bubbles should be removed or how efficient carbon dioxide insufflation is.

Acidosis induced by carbon dioxide insufflation decreases heparin potency: a risk factor for thrombus formation

Background:

Since the introduction of CO2 insufflation during open heart surgery in our hospital, we incidentally observed thrombus formation in the dissected heart, in the pericardium and in the cardiotomy reservoir of the cardiopulmonary bypass system. Furthermore, we measured very high levels of pCO2, causing severe acidosis, in stagnant blood in the pericardium and cardiotomy reservoir.

Objectives:

In this in vitro study, we assessed the influence of acidosis and hypothermia on heparin potency and thrombin formation.

Methods:

We assessed heparin potency in function of pH (pH 5.0-7.4) and temperature (24-37°C) by comparing the activated partial thromboplastin time in platelet-poor plasma between samples with and without unfractionated heparin. We measured thrombin formation in platelet-poor plasma by means of fluorescent, calibrated, automated thrombography in function of pH (pH 5.0-7.4) and temperature (24-37°C). The parameters of interest were the endogenous thrombin potential and the peak amount of thrombin generation.

Results:

The major finding of this study is the significant decrease in the efficiency of unfractionated heparin in delaying thrombus formation at acidotic (pH 5.0-7.0) conditions (p=0.034-0.05). Furthermore, we found that thrombin formation is significantly increased at hypothermic (24-34°C) conditions (p=<0.001-0.01).

Conclusions:

Based on the results of our in-vitro study, we conclude that acidosis may lead to a decreased heparin potency. Acidosis, as induced by CO2 insufflation, may predispose patients to incidental thrombus formation in stagnant blood in the open thorax and in the cardiotomy reservoir. Hypothermia might further increase this risk. Therefore, we recommend reconsidering the potential advantages and disadvantages of using CO2 insufflation during cardiopulmonary bypass.