Diagnosis of sepsis is challenging and, sometimes, it can be very difficult. This is due to the wide clinical variability of presentation of sepsis, depending on the site of the infection, the microorganism involved, the pre-existing co-morbidities and the prescribed therapy.
The first definition of sepsis and septic shock dates back to 1992 with the American College of Chest Physicians / Society of Critical Care (ACCP / SCCM) Consensus Conference Committee Report, and was based on four diagnostic categories:
- SIRS (Systemic Inflammatory Response Syndrome):
if at least two of the following conditions: heart rate> 90 beats per minute; Body temperature 38 ° C); tachypnea (>20 breaths per minute or paCO2 12,000/mm³), or an increase of more than 10% of immature forms of neutrophils
- Sepsis: SIRS + infection documented or probable
- Severe sepsis: when you have the presence of sepsis and tissue hypoperfusion or evidence of organ dysfunction (increased lactate, altered state of consciousness or oliguria)
- Septic shock: a hypotension induced by persistent sepsis after adequate fluid resuscitation
Hypotension induced by sepsis was defined as a systolic pressure 40 mmHg, or a decrease of at least 2 standard deviations below the normal value for the age, in absence of other causes of hypotension.
This first attempt to give a definition has been universally acknowledged, and had the merit to create awareness in the clinical setting, and to promote standardization of management of patients with suspected or documented sepsis.
However, during the last years these definitions have been criticized, especially as regards to the non-specificity of SIRS definition. After an initial review of the definition in 2001 (with little impact on the scientific community), on the year 2016 the SCCM together with the European Society of Intensive Care Medicine (ESCIM) have released a consensus document which, after a 18-months work, lead to publication of the third edition of the definitions of sepsis and septic shock (Sepsis-3).
The new 2016 guidelines, published in JAMA, have the purpose of making the diagnosis of sepsis immediate and therefore fast. These new definitions try to shift the focus of clinicians from infection itself to an organ dysfunction caused by infection, thus removing distinction between sepsis and severe sepsis, and also refining definition of septic shock.
Now sepsis is defined as “an organ dysfunction, life-threatening, caused by a dysregulated host response to infection“.
The focus then moves from inflammation assessment, which focused the criteria of SIRS (fever, body temperature, heart rate), to organ dysfunction. According to the authors, this is because the inflammation highlighted by SIRS is usually nonspecific and may even be a positive stress response of the organism. Indeed, the onset of organ failure is a consequence of an abnormal host process, which causes the damage of organs and tissues.
Organ dysfunction is represented by an increase in SOFA score compared to baseline value ≥ 2. If this is not known, it is assumed zero. Patients in this category have a mortality rate of about 10%.
The Consensus Conference now proposes the following definition for septic shock: “Septic shock occurs in a subset of patients with sepsis and comprises of an underlying circulatory and cellular/metabolic abnormality that is associated with increased mortality”. In practice, septic shock is identified in patients with sepsis is associated with the need to use of vasopressors to maintain MAP ≥ 65 mmHg and values of serum lactate ≥ 2 mmol /l.
This new definition focuses on two very important aspects of shock’s pathophysiology: the circulatory failure, which is manifested by hypotension, and the alteration of cellular metabolism, which is expressed by the increase in serum lactate concentration. Where it is not available the dosage of lactic acid, the authors give as an alternative the use of capillary refill time.
Calculate SOFA score outside the ICU is not simple. SOFA (Sequential Organ Failure Assessment score) is used to monitor the condition of a patient hospitalized in an intensive care unit. SOFA is a scoring system used to determine the extent of the organ function of a patient. The final score is based on the evaluation of six different clinical categories (respiratory, cardiovascular, neurological, coagulation, hepatic and renal function).
Therefore, the authors of the new guidelines aim to use the quick-SOFA (or qSOFA), a tool designed for the rapid identification of patients with suspected infection at risk for poor outcome (death or prolonged hospitalization in intensive care).
qSOFA is “positive” if there are at least two of the following criteria:
- Respiratory rate ≥ 22 breaths / min
- Alteration of consciousness
- Systolic blood pressure ≤ 100 mmHg
In cohorts of patients used to validate it, qSOFA was positive in 25% of patients. Mortality is of 1% for a score of 0, and it is over 20% when for score of 3. Compared with SIRS, this score has a better performance to predict mortality in patients with infection criteria and allows a simple and early identification of patients at increased risk of poor outcome, but it is not intended to diagnose either the infection or sepsis.
Citing the new guidelines, this score can be used to prompt clinicians to further evaluate the patient for the presence of infection and/or organ dysfunction, to start or adapt treatment, and to consider transfer to an ICU.
Failure to achieve two or more criteria of the SOFA and qSOFA should not postpone the investigation or treatment of an infectious context.
qSOFA cannot be considered a “screening” test for the sepsis and must be validated prospectively in order to enter in clinical practice.
– Abraham E. New Definitions for Sepsis and Septic Shock: Continuing Evolution but With Much Still to Be Done. JAMA. 2016 Feb 23;315(8):757-759. doi: 10.1001/jama.2016.0290.
–Shankar-Hari M et al. Developing a New Definition and Assessing New Clinical Criteria for Septic Shock: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016 Feb 23;315(8):801-810. doi: 10.1001/jama.2016.0287
– Singer M et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016 Feb 23;315(8):801-810. doi: 10.1001/jama.2016.0287
– Jacob JA. New Sepsis Diagnostic Guidelines Shift Focus to Organ Dysfunction. JAMA. 2016 Feb 23;315(8):739-740. doi: 10.1001/jama.2016.0736.