Systemic Inflammatory Response Syndrome (SIRS)

SIRS is not sepsis - Sepsis is SIRS plus a suspected source of infection. Pancreatitis, major burns, cardiopulmonary bypass, ischemia-reperfusion, and big surgery itself all produce an identical picture with nothing to culture. Almost all septic patients have SIRS, but only 62% of ED patients presenting with SIRS had a confirmed infection, and 38% of infected patients did not meet SIRS at all. Do not let a met-criteria alert start antibiotics you cannot justify, and do not let an unmet one reassure you.

The criteria are sensitive, not specific - Two of four out of temperature, heart rate, respiratory rate, and white cell count is a low bar. A postoperative patient who is cold, tachycardic, and breathing fast meets it with nothing wrong. What separates noise from disease is organ dysfunction, so look at the lactate, the creatinine, the platelet count, the bilirubin, and the mental status rather than stopping at the label.

Know which definition your institution runs on - The 2016 Sepsis-3 task force dropped SIRS criteria from the sepsis definition, redefining sepsis as life-threatening organ dysfunction from a dysregulated host response to infection, and put SOFA forward as the better predictor of in-hospital mortality with qSOFA as the bedside short form. qSOFA outperforms SIRS outside the ICU but loses discrimination inside it, where vasopressors and mechanical ventilation are already in play.

Vasoplegia is your intraoperative problem - Nitric oxide and prostacyclin dilate the vasculature while disrupted endothelial tight junctions dump protein-rich fluid into the interstitium. The patient is intravascularly dry while looking edematous. Expect an exaggerated fall with induction and vasopressor requirements that outrun anything the procedure would predict.

Fluids by responsiveness, not by a fixed number - A single volume target across patients with different cardiac, renal, and intravascular protein reserve does not hold up. After initial resuscitation, guide further volume with dynamic measures of fluid responsiveness rather than a preset total or a CVP number.

Cultures before antibiotics - Blood, sputum, urine, and any obvious wound should be cultured within the first hour of assessment and before the first antimicrobial dose. If you are inducing before that has happened, flag it rather than assuming the floor did it.

Lactate, with one caveat - Serial lactate plus a basic metabolic panel is how you track end-organ perfusion. But epinephrine used as a vasopressor raises lactate on its own by altering the pyruvate cycle, so a climbing lactate on an epinephrine infusion is not automatically worsening hypoperfusion.

Glucose target - Surviving Sepsis recommends keeping blood glucose under 180 mg/dL. Check a glucose intraoperatively; this patient is stress-hyperglycemic and often on insulin already.

Steroids in refractory shock - Low-dose hydrocortisone, 200 to 300 mg per day or equivalent, improves survival and helps reverse shock in patients still hypotensive despite fluid and vasopressors, on the basis of receptor-level unresponsiveness rather than an absolute cortisol deficit. If the patient is on it, continue it through the case and into the postoperative period.

Coagulopathy before neuraxial - IL-1 and TNF-alpha activate the coagulation pathway, producing microthrombosis and, in the severe end of the spectrum, DIC. Look at the platelet count, INR, and fibrinogen before considering a neuraxial technique, not after.

Source control cannot wait for optimization - When the operation is the treatment, incision and drainage, tube drainage of an abscess, or an exploratory laparotomy, resuscitate on the way to the room rather than delaying for a number to improve.

Persistent SIRS after antibiotics - Neutropenic patients and those on total parenteral nutrition with central venous access may need empiric antifungals if the SIRS response persists after empiric antibacterial coverage.

Plan the ICU bed up front - A SIRS score of 2 or more on day 1 of admission predicts progression to MODS, longer ICU stay, and a higher need for mechanical ventilation. Anticipate ARDS, aspiration pneumonitis from encephalopathy, demand-perfusion troponin rise with tachyarrhythmia, acute tubular necrosis, and metabolic acidosis. Book the bed before the case, not at the end of it.

Systemic inflammatory response syndrome (SIRS) is an exaggerated, dysregulated host defense against a noxious stressor: infection, trauma, surgery, acute inflammation, ischemia-reperfusion, or malignancy. It is defined by any two of four criteria, drawn from temperature, heart rate, respiratory rate, and white blood cell count. SIRS with a suspected source of infection is sepsis; SIRS from pancreatitis, major burns, or cardiopulmonary bypass is the same physiology with no organism to treat. Nitric oxide and prostacyclin drive vasodilation while cytokines, TNF-alpha and IL-1 followed by IL-6 and IL-8, disrupt endothelial tight junctions so protein-rich fluid leaks into the interstitium. Unchecked, the response progresses to coagulopathy, end-organ microthrombosis, loss of circulatory integrity, a compensatory anti-inflammatory phase of relative immunosuppression, and finally multiple organ dysfunction syndrome (MODS).