The systemic inflammatory response syndrome (SIRS) is the leading cause of morbidity & mortality in the critically ill. It is associated with a 50% reduction in 5 year life expectancy. SIRS is defined as 2 of the following criteria: heart rate >90, respiratory rate >20 or pCO
2
<4.3kPa, temperature <36 or >38°C, white cell count <4 or >12 x10
9
/l. These criteria are used to stratify patients for specific therapies & in research to define interventional groups. Cardiac surgery is associated with systemic inflammation. The validity of the SIRS criteria have never been formally evaluated post cardiac surgery. We undertook to describe the incidence of SIRS post cardiac surgery & relate this to outcome.
Methods:
We retrospectively analysed prospectively collected data from 2764 consecutive admissions following cardiac surgery (coronary bypass grafting 1425, valve surgery 763, combined procedure 252, other 324). The number of criteria met simultaneously within 1 hour epochs was recorded for the entire admissions.
Results:
96.4%, 57.9% & 12.2% of patients met at least 2, 3 or 4 criteria respectively within 24hrs of admission. The temperature criterion was least often fulfilled. ICU mortality was 2.67%. Length of stay exceeded 3 days in 18.5% of patients. The capacity of the criteria to predict mortality & prolonged ICU stay is presented in the table
.
Discussion:
Nearly all patients fulfilled the standard 2 criteria definition of SIRS within 24hrs of admission. This definition does not adequately define the subgroup of patients with greater systemic inflammation, mortality or length of stay. Thus, some clinical manifestations of inflammation are very common following cardiac surgery, although not necessarily prognostic. By contrast, the presence of 3 or more criteria was more discriminatory of death & prolonged ICU stay. We propose that 3 or more SIRS criteria is a more appropriate threshold that defines those patients with clinically significant inflammation post cardiac surgery.
Systemic inflammatory response syndrome post cardiac surgery: a useful concept?