biology

Systemic inflammatory response syndrome

Systemic inflammatory response syndrome is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Systemic inflammatory response syndrome rather than just read about it. In short: In immunology, systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult.

Key takeaways

Systemic inflammatory response syndrome belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Systemic inflammatory response syndrome to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Systemic inflammatory response syndrome from memory before moving on to harder problems.

Reference excerpt

In immunology, systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult. Although the definition of SIRS refers to it as an "inflammatory" response, it actually has pro- and anti-inflammatory components.

Presentation

Complications SIRS is frequently complicated by failure of one or more organs or organ systems. The complications of SIRS include

Acute kidney injury Shock Multiple organ dysfunction syndrome

Causes The causes of SIRS are broadly classified as infectious or noninfectious. Causes of SIRS include:

bacterial infections severe malaria trauma burns pancreatitis ischemia hemorrhage Other causes include:

complications of surgery adrenal insufficiency pulmonary embolism complicated aortic aneurysm cardiac tamponade anaphylaxis drug overdose

Diagnosis

SIRS is a serious condition related to systemic inflammation, organ dysfunction, and organ failure. It is a subset of cytokine storm, in which there is abnormal regulation of various cytokines. SIRS is also closely related to sepsis, in which patients satisfy criteria for SIRS and have a suspected or proven infection. Many experts consider the current criteria for a SIRS diagnosis to be overly sensitive, as nearly all (>90%) of patients admitted to the ICU meet the SIRS criteria.

Adult Manifestations of SIRS include, but are not limited to:

Body temperature less than 36 °C (96.8 °F) or greater than 38 °C (100.4 °F) Heart rate greater than 90 beats per minute Tachypnea (high respiratory rate), with greater than 20 breaths per minute; or, an arterial partial pressure of carbon dioxide less than 4.3 kPa (32 mmHg) White blood cell count less than 4000 cells/mm³ (4 billion cells/L) or greater than 12,000 cells/mm³ (12 billion cells/L); or the presence of greater than 10% immature neutrophils (band forms). Band forms greater than 3% is called bandemia or a "left-shift". When two or more of these criteria are met with or without evidence of infection, patients may be diagnosed with "SIRS". Patients with SIRS and acute organ dysfunction may be termed "severe SIRS". Note: Fever and an increased white blood cell count are features of the acute-phase reaction, while an increased heart rate is often the initial sign of hemodynamic compromise. An increased rate of breathing may be related to the increased metabolic stress due to infection and inflammation, but may also be an ominous sign of inadequate perfusion resulting in the onset of anaerobic cellular metabolism.

Children The International Pediatric Sepsis Consensus has proposed some changes to adapt these criteria to the pediatric population. In children, the SIRS criteria are modified in the following fashion:

Heart rate is greater than 2 standard deviations above normal for age in the absence of stimuli such as pain and drug administration, or unexplained persistent elevation for greater than 30 minutes to 4 hours. In infants, also includes heart rate less than 10th percentile for age in the absence of vagal stimuli, beta-blockers, or congenital heart disease or unexplained persistent depression for greater than 30 minutes. Body temperature obtained orally, rectally, from Foley catheter probe, or from central venous catheter probe less than 36 °C or greater than 38.5 °C. Respiratory rate greater than 2 standard deviations above normal for age or the requirement for mechanical ventilation not related to neuromuscular disease or the administration of anesthesia. White blood cell count elevated or depressed for age not related to chemotherapy, or greater than 10% bands plus other immature forms. Temperature or white blood cell count must be abnormal to qualify as SIRS in pediatric patients.

Treatment Generally, the treatment for SIRS is directed towards the underlying problem or inciting cause (i.e. adequate fluid replacement for hypovolemia, IVF/NPO for pancreatitis, epinephrine/steroids/diphenhydramine for anaphylaxis). Selenium, glutamine, and eicosapentaenoic acid have shown effectiveness in improving symptoms in clinical trials. Other antioxidants such as vitamin E may be helpful as well. Septic treatment protocol and diagnostic tools have been created due to the potentially severe outcome septic shock. For example, the SIRS criteria were created as mentioned above to be extremely sensitive in suggesting which patients may have sepsis. However, these rules lack specificity, i.e. not a true diagnosis of the condition, but rather a suggestion to take necessary precautions. The SIRS criteria are guidelines set in place to ensure septic patients receive care as early as possible. In cases caused by an implanted mesh, removal (explantation) of the polypropylene surgical mesh implant may be indicated.

History The concept of SIRS was first conceived of and presented by William R. Nelson, of the Department of Surgery of the University of Toronto. SIRS was more broadly adopted in 1991 at the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference with the goal of aiding in the early detection of sepsis. Criteria for SIRS were established in 1992 as part of the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference. The conference concluded that the manifestations of SIRS include, but are not limited to the first four described above under adult SIRS criteria. In septic patients, these clinical signs can also be seen in other proinflammatory conditions, such as trauma, burns, pancreatitis, etc. A follow-up conference, therefore, decided to define the patients with a documented or highly suspicious infection that results in a systemic inflammatory response as having sepsis. Note that SIRS criteria are non-specific, and must be interpreted carefully within the clinical context. These criteria exist primarily for the purpose of more objectively classifying critically ill patients so that future clinical studies may be more rigorous and more easily reproducible.

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Systemic inflammatory response syndrome

Start with the simplest possible case. Write down what Systemic inflammatory response syndrome claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Systemic inflammatory response syndrome before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Systemic inflammatory response syndrome ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Systemic inflammatory response syndrome

In research: Systemic inflammatory response syndrome appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Systemic inflammatory response syndrome in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Systemic inflammatory response syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Causes of death, Immune system disorders, Intensive care medicine, so understanding it makes those chapters shorter.
In everyday life: Look for Systemic inflammatory response syndrome outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Systemic inflammatory response syndrome in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Systemic inflammatory response syndrome means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Systemic inflammatory response syndrome out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Systemic inflammatory response syndrome in simple terms?

In immunology, systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is the body's response to an infectious or noninfectious insult.

Why does Systemic inflammatory response syndrome matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Systemic inflammatory response syndrome?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Systemic inflammatory response syndrome.