eComment. Organism functionality parameters in predicting the length of intensive care unit stays?

We read the article by Widyastuti et al. [1] with great interest and it is true that cardiac surgery results have improved in accordance with improvements in cardiac techniques and perioperative care. This has led to the fact that the current profile of patients undergoing cardiac surgery is becoming an increasingly more elderly one with greater co-morbidity, thus implying an increase in surgical risk and, likewise, an increase in in-hospital stay, whether in the intensive care unit (ICU) or in total [2]. The currently most-used risk prediction scales have certain limitations and this means that, for specific groups of patients, they are not capable of a correct risk fit [3]. Moreover, it is difficult to know what the evolution of a patient who has been operated on will be, due to the large number of variables that may exert an influence on this aspect, and, therefore, how long the length of ICU stay will be. The variables that measure the organism functionality parameters once the surgical procedure is over could be of great use in estimating subsequent evolution in conjunction with the preoperative risk scales. Many authors, and even various scales, have highlighted the importance of bearing in mind the parameters related with the inflammatory response and haemodynamic state of the patient, such as: hyperlactataemia, bicarbonate, heart rate, lactate and creatinine upon admittance to an ICU in order to establish predictive models that increase the precision of such an estimation [4, 5]. Another important aspect in analyzing immediate postoperative evolution is evaluating the development of complications during the surgical procedure (e.g., bleeding, acute myocardial infarction, inadequate myocardial protection, etc). These are going to be reflected in a series of metabolic alterations like: creatinine, haematocrit, troponin T (TnT), pH, bicarbonate (HCO3-) or the ratio of partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FiO2), etc. With regard to the intraoperative variables to which the authors refer, these are fundamentally centred on bleeding and the need for haemoderivatives [1]. Such variables may give rise to multi-collinear phenomena and it would therefore be advisable to carry out a check with an analysis of tolerance in order to determine the impact that these could have. Another interesting piece of information would have been the comparison that could have been made between the proposed model and other scales based on variables upon ICU admittance, such as APACHE, SAPS II, and MPM II, with the aim of more broadly evaluating its validity. Thus, intraoperative factors may probably modify the preoperative risk stratification: poor operative results, inadequate myocardial protection, etc. All these, and other, serious intra-operative factors could increase the risk of operative mortality to values above those indicated by preoperative risk models or increase the length of ICU stay. It is for this reason that the evaluation of the intraoperative and immediate postoperative variables that reflect the haemodynamic and functional state of the patient, in addition to the predictive risk-scales based on preoperative variables, could help in carrying out a more accurate estimation of the duration of ICU admittance. Conflict of interest: none declared