Original articleAre Shock Index and Adjusted Shock Index useful in predicting mortality and length of stay in community-acquired pneumonia?
Introduction
Community acquired pneumonia (CAP) results in about 83,000 hospital admissions in UK every year [1], [2]. Among those patients who require hospitalisation, the average mortality rate is 12%. However, the mortality in CAP can be as high as 40% in patients who develop sepsis or require intensive care therapy [3].
Early and correct identification of patients at risk of death from CAP remains crucial and several indices have been developed. The CURB-65 score which scores 1 each for confusion, serum urea nitrogen level > 19.6 mg/dL [to convert to millimole per litre, multiply by 0.357 i.e. Urea > 7 mmol/L], respiratory rate ≥ 30/min, low blood pressure [< 90 mm Hg systolic or ≤ 60 mm Hg diastolic, and age ≥ 65 years) (severe pneumonia: ≥3 score) is recommended by the British Thoracic Society in the UK to identify patients at risk of dying from CAP. However, blood pressure is dependent on the cardiac output and the peripheral resistance. Using the blood pressure criterion in the severity assessment of CAP may lead to false negativity in the older people due to high prevalence of systolic hypertension with increasing age.
Shock Index (SI) is the ratio of heart rate to systolic blood pressure [4]. It is a sensitive indicator of left ventricular dysfunction [4]. Despite vital signs that may not appear strikingly abnormal, an elevated SI has been found to be useful in identifying patients requiring hospital admission and/or intensive care therapy [5]. Shock Index has been shown to be inversely related to left ventricular stroke volume in acute circulatory failure [6]. Shock index has also been studied as a marker for significant injury in trauma patients with hypovolaemic shock [7]. SI is a better predictor of 48 hour mortality in victims of blunt injury than either heart rate or systolic blood pressure alone [8].
Shock Index normally ranges from 0.5 to 0.7. In a study looking at healthy blood donors with uncompensated blood volume loss, SI was high after 5 min of giving blood [9]. In predicting rupture of ectopic pregnancy, high SI was found to be more useful than heart rate or blood pressure on its own [10]. In risk stratifying patients with acute pulmonary embolism, SI of ≥1.0, independent of echocardiographic findings, was found to be associated with increased in-hospital mortality [11].
To date, very little is known about Shock index and Adjusted Shock Index (corrected to temperature) (ASI) in predicting mortality in patients admitted to the hospital with CAP.
Our hypothesis is that admission SI and/or ASI may be useful in correctly identifying people with CAP who are at a high risk of dying within 6 weeks and may also be used to predict the length of hospital stay.
Section snippets
Methods
We compiled data of prospective audits of CAP from three UK hospitals: one University Hospital in Central Norfolk with a catchment population of ~ 750,000 (April–August 2008), one district general hospital in West Norfolk with a catchment population of ~ 250,000 (December 2006–Jan 2007), and one large district general hospital in Suffolk with a catchment population of ~ 500,000 (April 2007). We used the standardised definition of CAP, case ascertainment method, inclusion and exclusion criteria and
Results
190 patients with CAP admitted to three UK hospitals were included in the study. There were 100 males (53%). The age range was 18- 101 years (median = 76 years).
The sample characteristics presented in Table 1 compares men and women. The median age among the men was 73.2 years (95% CI: 72.9 to 79.9 years) and that for women was 78.7 years (95% CI: 74 to 83.8 years). The median body temperature was similar between men and women but women had a slightly higher median heart rate. Comparing men to women,
Discussion
We found that both high shock index (SI) and adjusted shock index (ASI) of > 1.0 predict death at 6 weeks with all deaths occurring within 30 days in this population with community acquired pneumonia. There was no evidence to suggest that they predict length of stay (defined as stay greater than median).
The number of patients included in the study is somewhat modest at 190 patients. However, the sample size is comparable with the original validation study of CURB-65 by Lim et al [14].
The clear
Learning points
- •
Risk stratifying patients with community-acquired pneumonia is vital in acute care assessment.
- •
Shock index and adjusted shock index are easy to derive and they predict 6 weeks mortality in community acquired pneumonia.
Funding
None.
Disclosure/competing interest statement
None.
Author contributions
PKM, SMT, AVK and DNS designed the audit pro-forma. DNS, HR, ACS, PP and PS collected the data. PKM, SMT and AVK verified the data. PM analysed the data. PS and PKM prepared the draft manuscript and all co-authors contributed in writing of the manuscript.
Acknowledgements
We thank the Clinical Audit Departments of Queen Elizabeth Hospital, King's Lynn; Ipswich Hospital, Ipswich; and Respiratory Medicine Department of Norfolk and Norwich University Hospital, Norwich for their help and assistance with the project.
References (22)
- et al.
A comparison of shock index and conventional vital signs to identify acute critical illness in the emergency department
Ann Emerg Med
(1994) - et al.
A re-evaluation in acute circulatory failure
Resuscitation
(1992) - et al.
Shock Index in diagnosing early acute hypovolemia
Am J Emerg Med
(2005) - et al.
The ability of traditional vital signs and shock index to identify ruptured ectopic pregnancy
Am J Obstet Gynaecol
(2003) - et al.
Prognostic value of shock index along with trans thoracic echocardiographic findings of patients with acute pulmonary embolism
Am J Cardio
(2008) - et al.
Continuous central venous oximetry and shock index in the emergency department: use in the evaluation of clinical shock
Am J Emerg Med
(1992) - et al.
Confusion, Urea, Respiratory Rate and Shock Index or Adjusted Shock Index (CURSI or CURASI) criteria predict mortality in community- acquired pneumonia
Eur J Intern Med
(2010) - et al.
Management of community-acquired pneumonia and secular trends at different hospitals
Respir Med
(2005) - et al.
Community acquired pneumonia in elderly people. Current British guidelines need revision
BMJ
(1998) - et al.
Severity prediction rules in community acquired pneumonia, a validation study
Thorax
(2000)
A prediction rule to identify low-risk patients with community-acquired pneumonia
N Engl J Med
Cited by (50)
In-hospital mortality of acute pulmonary embolism: Predictive value of shock index, modified shock index, and age shock index scores
2022, Medicina ClinicaCitation Excerpt :Due to lack of consensus, studies comparing objective criteria identifying patients with hemodynamic instability in acute pulmonary embolism are needed. Previous studies have shown that the SI, heart rate divided by systolic blood pressure, is a predictor of adverse events in various cardiovascular and non-cardiovascular diseases including pneumonia,10 sepsis,11 stroke,12 acute coronary syndrome,13 and acute pulmonary embolism.14 The normal range for SI is generally accepted as 0.5–0.7, and the SI > 1.0 has been found to predict mortality in these studies.10–14
Shock index predicts up to 90-day mortality risk after intracerebral haemorrhage
2021, Clinical Neurology and NeurosurgeryUse of age shock index in determining severity of illness in patients presenting to the emergency department with gastrointestinal bleeding
2021, American Journal of Emergency MedicineCircadian rhythm in critically ill patients: Insights from the eICU Database
2021, Cardiovascular Digital Health JournalShock index as a predictor of mortality among the Covid-19 patients
2021, American Journal of Emergency MedicineMobile Intensive Care Unit versus Hospital walk-in patients, in the treatment of first episode ST- elevation myocardial infarction
2020, European Journal of Internal Medicine