Septic Shock: Definition, Diagnosis and Management

Septic shock is a life-threatening condition that occurs when sepsis, a dysregulated host response to infection, leads to organ dysfunction, circulatory failure and metabolic abnormalities. It is associated with a higher risk of mortality than sepsis alone and requires prompt recognition and treatment.

Definition

The latest definition of septic shock was proposed by the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3) in 2016. According to this definition, septic shock is a subset of sepsis in which particularly profound circulatory, cellular, and metabolic abnormalities substantially increase mortality. The diagnostic criteria for septic shock are:

- A confirmed or suspected infection

- A serum lactate level greater than 2 mmol/L (18 mg/dL) after adequate fluid resuscitation

- The need for vasopressor therapy to maintain a mean arterial pressure (MAP) of 65 mmHg or greater

The previous definitions of septic shock, based on the systemic inflammatory response syndrome (SIRS) criteria and the presence of hypotension, were found to be less specific and less predictive of mortality than the Sepsis-3 definition.

Diagnosis

The diagnosis of septic shock relies on clinical assessment, laboratory tests and hemodynamic monitoring. The following steps are recommended for diagnosing septic shock:

- Identify the source of infection by obtaining blood cultures and other relevant specimens before starting antimicrobial therapy

- Measure serum lactate level

- Assess organ function by using sequential organ failure assessment (SOFA) score or quick SOFA (qSOFA) score

- Evaluate fluid status by using physical examination, central venous pressure (CVP), urine output and dynamic parameters such as stroke volume variation (SVV)

- Monitor blood pressure and cardiac output by using invasive or non-invasive methods

- Adjust vasopressor therapy according to MAP and perfusion goals

Initially, it was believed that the elevated lactate levels during sepsis were due to increased production because of insufficient oxygen delivery.
However, several studies have shown an increase in lactate without deficiencies in oxygen delivery. Instead, a connection has been found between epinephrine stimulation and elevated lactate

Management

The management of septic shock aims to restore tissue perfusion, control infection, support organ function and prevent complications. The following interventions are recommended for managing septic shock:

- Initiate empiric broad-spectrum antimicrobial therapy within one hour of recognition of septic shock

- Administer intravenous fluids as initial resuscitation with crystalloids at 30 mL/kg within three hours

- Titrate fluids according to hemodynamic response and avoid fluid overload

- Start vasopressors if MAP remains below 65 mmHg despite adequate fluid resuscitation

- Use norepinephrine as the first-line vasopressor agent; add vasopressin or epinephrine as second-line agents if needed; avoid dopamine unless norepinephrine is unavailable

- Target a MAP between 65 mmHg and 75 mmHg; individualize MAP goals according to patient characteristics such as age, comorbidities and chronic hypertension

- Consider adding an inotrope such as dobutamine if cardiac output is low despite adequate fluid resuscitation and vasopressor therapy

- Reassess source control within six hours; perform timely drainage or debridement of infected foci if indicated

- Provide supportive care such as mechanical ventilation, renal replacement therapy, blood transfusion, glycemic control, stress ulcer prophylaxis and deep vein thrombosis prophylaxis according to guidelines

Conclusion

Septic shock is a medical emergency that requires early identification and aggressive treatment. The latest definition of septic shock emphasizes the presence of hyperlactatemia and vasopressor dependence as markers of increased mortality risk. The management of septic shock involves prompt antimicrobial therapy, fluid resuscitation, vasopressor therapy, source control and supportive care. Further research is needed to improve the outcomes of patients with septic shock.

References:

[1] Singer M et al. The Third International Consensus Definitions for Sepsis ... JAMA. 2016;315(8):801–810.

[2] Rhodes A et al. Surviving Sepsis Campaign: International Guidelines ... Crit Care Med. 2017;45(3):486–552.

[3] Shankar-Hari M et al. Developing a New Definition ... JAMA. 2016;315(8):775–787.

[4] Seymour CW et al. Assessment ... JAMA. 2016;315(8):762–774.

[5] Angus DC et al.

[6] Sébastien Gibot. On the origins of lactate during sepsis. Crit Care. 2012; 16(5): 151.

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