Sirs

Systemic Inflammatory Response Syndrome

Dr. Vinayak

Shock associated with sepsis syndrome is common cause of death in surgical intensive care units.

Patient in shock from sepsis are at risk for subsequent multiple organ failure.

Multiple organ failure can be caused by an exaggerated endogenous inflammatory response to invasive infection.

Ultimate survival of infected patient in shock may depend on therapies that ameliorate the immune response while the patient retains the capacity to kill invading microorganisms.

Bone and colleagues defined four categories of clinical disease that represented successive levels of escalating severity of inflammatory response

Consensus conference described the response to infection as beginning with a systemic inflammatory response syndrome (SIRS).

SIRS is not exclusively a reaction to infection but can also be observed in response to the sterile insult of pancretitis, aspiration pneumonitis , burns, trauma and post-surgery.

Criteria for four categories of systemic inflammatory response syndromeSystemic inflammatory response syndrome

(SIRS) Two or more of the following, due to either an infectious or a

noninfectious etiology: • Temperature 38C or 36C • Respiratory rate 24 breaths/ min • Heart rate 90 beats/ min • WBC count 12,000/L or 4000/L, or

10% immature (bands) cells in peripheral blood smear

Sepsis— same criteria as SIRS with clearly established focus of infection

Severe sepsis— Sepsis associated with organ dysfunction and hypoperfusionIndicators of hypoperfusion : Systolic blood pressure <90 mmhg >40 mmhg fall from normal systolic blood

pressure Lacticacidemia Oliguria Acute mental status changes

Septic shock— Patient with sever sepsis who: Are not responsive to intravenous fluid infusion for resuscitation Require inotropic or vasopressor agents to

maintain systolic blood pressure

Majority of SIRS patient have clinically suspected or culture-positive site of infection.

Four most common sites of infection: pulmonary bloodstream genitourinary tract intra-abdominal infections

Bacterias responsible for septic shock: Gram positive sepsis 44% Gram negative sepsis 44% Fungamia 3% Mixed infections in remaining cases

Top three gr +ve bacterias Staphylococcus aureus Enterococcus species Coagulase negative staphylococcus speciesTop three gr -ve bacterias Escherichia coli Klebsiella species Pseudomonas aeruginosa

It indicates that with new diagnosis of SIRS blood culture should be obtain as well as culture from suspected sites before instituting empirical therapy with antibiotics

Broad spectrum antibiotics may prevent progression to septic shock

Emperical antifungal therapy should not be routinely given unless patient is immunocompromised

Toxins released by bacteria killed by antibiotics are capable of provoking the inflammatory response

SIRS as an Exaggerated Inflammatory Response

Systemic inflammatory response syndrome (SIRS)Definition Delocalized and dysregulated inflammation

process of high intensity. It leads to disorders of microcirculation, organ perfusion and finally to secondary organ dysfunction.

This secondary dysfunction is not due to primary insult, but due to autoaggressive systemic inflammatory response of the organism to the primary insult.

This systemic inflammatory response syndrome (SIRS), leads without therapeutic intervention to multiple organ dysfunction syndrome (MODS) and death.

PathogenesisProinflammatory cytokines:

TNF – alphaIL - 1, IL – 6, IL – 8, IL – 12Interferon – gamma

Anti-inflammatory cytokinesIL – 4, IL – 10, IL – 13Transforming growth factor (TGF) - beta

Systems responsible for inflammatory response

PathogenesisProinflammatory cytokines activate:

Biochemical systemsComplement, coagulation, kinin, etc.

Endothelial cellsPMN's/plateletsRelease of secondary mediators

NO, prostaglandins, vasoactive agents, endorphins, free-O2 radicals, etc.

The complex interactions involved in SIRS with both beneficial and deleterious effects

Pathways for recovery from SIRS or progression to MODS

SepsisMechanisms of Injury

Ischemia

Cytopathic injury

Massive proinflammatory response

Septic ShockPathophysiology: Cardiovascular

Systemic circulationArterial & venous dilationBiventricular depression of the ejection fraction

with ventricular dilatation.

Septic ShockPathophysiology: Vascular

Regional circulationAltered blood flow

Microcirculation Development of microthrombi

Decreased functional capillariesAbnormal O2 utilizationIncreased microvascular permeability

SepsisSpecific Organ Responses

Lung:

V/Q mismatchHypoxemia

Increased microvascular permeabilityInterstitial/alveolar edema

ARDS


Gastrointestinal:Impaired GI motility

Bacterial translocation >> MODSStress-ulcer GI bleedingHepatic dysfunction


Kidney:Altered renal functionATN/ acute renal failure

Increases mortality rate

Neurologic:EncephalopathyPeripheral polyneuropathy

68% - 100%


Hematologic:Leukocytosis/leukopeniaThrombocytopeniaCoagulopathyDIC

~ 15% - 20%

ManagementThe key of management is early recognition of the condition

The priorities in the management are ABCs.First priority is to secure adequate airway and

oxygenation. Suplemental oxygen to be given to all patients.Adequate amount of fluids to restore the perfusion

of the vital organs .

Cardiovascular support preload - MAPContractility – Sr. Ca, Sr.Mg,hypoxemia, beta

blockers Inotropic agentsafterload

Hematologic supportTransfusion of plateletsTransfusion of FFP

MonitoringRespiratory monitoringCardiovascular monitoring

Indications for ICU admissionIntubation for airway supportRespiratory failure requiring higher FIO2. or

reqiring mechanical ventilationRequiring advanced cardiovascular / inotropic

supportRenal replacement therapy

SummarySIRS is systemic inflammatory response to variety

of stimuliInfection is present in only 50% of casesOnce systemic response has been initiated it

continues despite being self harmingPrompt diagnosis and effective resuscitations are

essentialProgression to MODS carries high mortality rate

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