Supply Induced Demand in Intensive Care Unit: a Retrospective Trial

Intensive Care Unit (ICU) represents a high-level healthcare resource in hospitals. An ICU bed is expensive compared to other types of beds, estimated at between €937 and €1,472 each, according to studies in several European countries. The ICU is the department where the hospital's most seriously ill patients are treated. The nature of the hospitalization can vary, and each hospital has the option of having a multispecialty ICU (dedicated to all critically ill patients), or alternatively dedicated ICUs based on the primary pathology, such as cardiac surgery, neurosurgery, post-operative intensive care, transplant surgery, etc.

The causes of hospitalization in critical care are therefore multiple, and over the years numerous prognostic scores have been proposed, which therefore correlate the severity of the pathology with the predicted mortality from a statistical point of view. The function of the scores is also to assist the physician in clinical choices, helping to select patients who are presumed to have the greatest chance of benefiting from hospitalization in an intensive care environment, and therefore discarding patients who are either not too serious, or vice versa too compromised to benefit from hospitalization of this type. The long and difficult stay in Intensive Care can also influence the turnover of beds, and their availability.

The two most frequently used prognostic scores in critical care are the Acute Physiology And Chronic Health Evaluation (APACHE) II score and the Simplified Acute Physiology Score (SAPS) II. Both widely used in clinical and scientific settings, these scores present some differences: while the SAPS II has a more streamlined framework of the patient's clinical characteristics, the APACHE II considers a little more the anamnesis and chronic pathologies of the subject hospitalized in Intensive Care. In fact, the vital and physiological parameters addressed with the APACHE II are numerically higher than those of the SAPS II. Despite this, there does not appear to be a difference between the two scores in terms of predictive value of mortality; some studies have examined this hypothesis, finding both systems reliable from this point of view.

The choice to admit a patient to Intensive Care, therefore, is a clinical, economic and managerial choice. In recent years, several studies have examined the availability of beds in Intensive Care and their impact on the clinical and economic performance of the department. Sometimes the turnover is technically and temporally expensive due to numerous reasons, such as the severity of the clinical picture, the high level of monitoring and the number of connected machines, delaying the patient's admission. Several studies have noted how the waiting time before admission to Intensive Care increases patient mortality, especially when it is longer than 6 hours.

Due to the costs of the ICU beds, as well as to the fact that shortage of beds may have a significant clinical impact on patients, many studies addressed the issue of supply-induced scarcity (SIS), i.e. scarcity due to a lack of supply and not to an excess of demand.

In the case of beds in Intensive Care, some authors have demonstrated how the phenomenon of SIS affects the critical environment, but without alterations in the perception of value; for example, although the economic cost of a bed of this type is higher than in other departments, the cost/benefit ratio in terms of perception of the service provided remains positive for the patient and for the community. From 2020 onwards, following the Covid-19 pandemic, we have witnessed a profound revolution in the availability, number and type of triage that underlie the availability of beds in Intensive Care.

On the other side, Health Economics has demonstrated that often an increase in supply can generate an increase in demand, even when this increase is not strictly necessary or appropriate. This phenomenon, called supply-induced demand (SID), to the best of our knowledge, few studies have been conducted in critical care settings; moreover, the correlation between SID and outcomes, specifically mortality, has never been demonstrated.

The aim of this retrospective, single-center study, therefore, is to investigate the presence of SID, and the consequent effects on mortality outcome, in a multispecialty Postoperative Intensive Care Unit.