A set of the cardiac index data during extracorporeal circulation (ECC) for patients with mixed venous oxygen saturation (SvOdos) above 68%, mean arterial pressure (MAP) above 60 mmHg and tissue oxygen delivery (DO2) greater than 280 mL/min/m 2 , in the function of haemoglobin density and tissue oxygen delivery
The linear regression curves for three selected oxygen delivery (DO2) levels showing the relationship between cardiac index (CI) and haemoglobin density
Recently accumulating evidence has suggested that the trends in current perfusion practice need to be improved as we experience tremendous technological improvement every day. The discussed new GDP concept provides an ideal opportunity to apply treatment which is tailored to the individual patient’s needs and, therefore, aims to diminish the risk of complications throughout the entire surgical procedure. Consequently, the emerging concept jeopardizes the current widely accepted CPB strategies of organ perfusion based on a constant pump flow rate and the ubiquitous indicators of tissue perfusion, such as lactate concentration and urine output, with lactates representing effective tissue perfusion and metabolism balance, and urine output being a vital indicator of renal perfusion. The main goal of GDP is to optimize tissue oxygen delivery and extraction. Interestingly, adequate perfusion represented by the flow rate is a crucial component of DO2.
In current clinical practice, the haemodynamic values used by perfusionists are based solely on observational studies designed on the basis of the physiology of a healthy individual. For instance, the pump flow rate is the equivalent of the average calculated cardiac index (CI). The advancement in System M in-line non-invasive monitoring provides an opportunity to conduct real-time observation of flow rates, both venous and arterial saturation, haemoglobin level, the extent of carbon dioxide production and also calculate all exponents of oxygen transport. The aim of our study was to find the relationships between the set pump flow rates and the ultimate GDP conditions, such as DO2 > 280 mL/min/m2, SvO2 > 68% and the minimum MAP of 60 mmHg. Statistical analysis was performed with Data Science calculation tool, which is more frequently introduced as codes that can assess with high probability if, for instance, a skin mole will turn into cancer or classify genes responsible for leukaemia [12, 13]. In our study, we strived to present how the application of this technology can help to easily visualise the correlation between factors that would be incalculable elsewhere. Using the described tools, the pattern in the data that corresponds to the relationship between CI and Hb for the same DO2i value was derived (Fig. 3). Hence, to ensure a certain level of DO2 at MAP> 60 mmHg, haemoglobin value necessitates the adjustment of the appropriate pump flow rate. The graph illustrates that at Hg of 10 g%, the initial pump flow rate within the study population was set on 2.2 l/min/m 2 , while at Hg level of 8 g% the pump flow rate should be sustained on approximately 2.6 l/min/m 2 . The described relationship is part of the GDP concept, however, the perfusion pressure above 60 mmHg is an additional parameter that was analysed.
The presented observations reflect substantial mechanisms in the newly created haemodynamic patient – heart-lung machine model. Nevertheless, the depicted concept requires further observation. Appropriate models dedicated to higher perfusion pressures and different DO2 values should be evaluated as it would be extremely useful in managing patients concurrently affected by primary cerebral and visceral hypoperfusion in particular. Moreover, perfusion strategy should be individualized to match the patient’s unique physiology that changes over time.