Shock

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Shock index[60]

The shock index (SI), defined as the ratio of the heart rate (in beats per minute) to the systolic blood pressure (in mmHg), has been shown to be a clinically useful bedside method to estimate the level of shock and mortality in potential hemorrhagic and infection-related shock states. The normal range for SI is from 0.5 to 0.7. An SI >1.0 has been associated with significant shock and poor outcome due to circulatory failure. Elderly age, hypertension, and current treatment with calcium-channel blockers or beta-blockers may weaken the association of SI with shock and mortality.[60]

Sepsis screening tools

Sepsis screening tools are designed to promote the early identification of sepsis. They consist of manual methods or automated use of the electronic health record (EHR), which includes the National Early Warning Score (NEWS), Modified Early Warning Score (MEWS), and quick Sequential Organ Failure Score (qSOFA) Criteria. There is wide variation in the diagnostic accuracy of these tools, but they are an important component in the early identification of sepsis for timely intervention.[2]

Early warning scores are based on several physiologic parameters, where the greater the deviation from normal, the higher the score. Each parameter is evaluated individually and then the final score is aggregated.

NEWS is based on the evaluation of six individual parameters, each of which is assigned a score of 0 to 3. The parameters are: respiratory rate, oxygen saturations, temperature, blood pressure, heart rate, and level of consciousness. The aggregate NEWS2 score triggers the level of response required, including the seniority of the clinical decision maker, the urgency of review, and the most appropriate place of care. An aggregate score of ≥7 has a significant risk of mortality, so it should prompt emergency evaluation by a critical care specialist and transfer to a high-dependency setting for continuous monitoring of vital signs.[24]

MEWS draws on five physiologic parameters (systolic blood pressure, heart rate, respiratory rate, temperature; and alert, voice, pain, unresponsive score [AVPU score]).[61] Scores of 5 or more are associated with increased risk of death, intensive care unit (ICU) admission, and high-dependency unit (HDU) admission. It identifies patients at risk of deterioration who require increased levels of care in the HDU or ICU.[61]

The qSOFA uses three variables to predict death and prolonged ICU stay in patients with known or suspected sepsis: a Glasgow Coma Score <15, a respiratory rate ≥22 breaths/minute, and a systolic blood pressure ≤100 mmHg. When any two of these variables are present simultaneously, the patient is considered qSOFA positive.

Studies have shown that qSOFA is more specific but less sensitive than having two of the four Systemic Inflammatory Response Syndrome (SIRS) Criteria for early identification of infection induced organ dysfunction.[2] Neither SIRS nor qSOFA are ideal screening tools for sepsis and the bedside clinician should understand the limitations of each.[2] Although the presence of a positive qSOFA should alert the clinician to the possibility of sepsis in all resource settings, its poor sensitivity has led the Surviving Sepsis Campaign to advise against using the qSOFA, compared with NEWS or MEWS, as a single screening tool for sepsis or septic shock.[2]

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