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CHAPTER 13: Assessment of Severity of Illness 83

associated with subsequent improvement in patient outcomes. In addi- CHAPTER Assessment of Severity
49
tion, the majority of studies showing effectiveness of the service have
included a doctor as the team leader, suggesting that the composition of of Illness
the team may also impact patient outcomes. 13
James A. Russell
CONCLUSIONS
Despite the best efforts of health care staff and advances in medicine,
patients admitted to modern hospitals suffer SAEs in up to 20% of KEY POINTS
admissions. Such events are preceded by signs of instability that manifest • In the last four decades, intensive care units (ICUs) and critical
as measurable derangements in the patients’ vital signs, sometimes for care researchers have amassed a great body of pathophysiologic
https://kat.cr/user/tahir99/
several hours prior to the development of the event. The RRS approach and clinical knowledge that has advanced the care of critically ill
involves staff activating the RRT when a ward patient fulfills predefined patients. Severity of illness scoring systems are tools that have been
criteria of instability. In sites where there has been acceptance and designed to both predict and evaluate, from multiple perspectives,
uptake of the RRS, there has been an associated reduction in cardiac the outcomes of critically ill patients.
arrests, and in some cases unplanned ICU admissions and in-hospital
mortality. It is likely that increasing the dose (calls/1000 admissions) of • Most scoring systems evolved from multivariate regression analysis
applied to large clinical databases of discovery cohorts to identify
RRT calls is likely to influence patient outcomes.
the most relevant factors for prediction of mortality. Scoring sys-
tems are then validated by prospective application to independent
validation cohorts.
KEY REFERENCES • The ideal components of a scoring system are data collected during
• Baker GR, Norton PG, Flintoft V, et al. The Canadian Adverse the course of routine patient management that are easily measured
Events Study: the incidence of adverse events among hospital in most or all patients, inexpensive, objective, and reproducible.
patients in Canada. CMAJ. 2004;170(11):1678-1686. • The most widely applied scoring systems in adults are the
• Bellomo R, Goldsmith D, Uchino S, et al. A prospective before- Acute Physiology and Chronic Health Evaluation (APACHE), the
and-after trial of a medical emergency team. Med J Aust. Mortality Probability Models (MPM), Simplified Acute Physiology
2003;179(6):283-287. Score (SAPS), and Sequential Organ Failure Assessment (SOFA).
• Buist M, Bernard S, Nguyen TV, Moore G, Anderson J. Association • The uses of severity-of-illness scoring systems for cohorts of
between clinically abnormal observations and subsequent in-hospital patients include clinical investigation (to compare study groups
mortality: a prospective study. Resuscitation. 2004;62(2):137-141. usually at baseline but sometimes over the course of ICU care),
• Buist M, Harrison J, Abaloz E, Van Dyke S. Six year audit of cardiac ICU administration (to guide resource allocation and budget), and
assessment of ICU performance (to compare performance over
arrests and medical emergency team calls in an Australian outer time or between health care settings).
metropolitan teaching hospital. BMJ. 2007;335(7631):1210-1212.
• Buist MD, Moore GE, Bernard SA, Waxman BP, Anderson JN, • The use of scores to guide decisions about delivery of care to indi-
vidual patients is controversial; in some studies the accuracy of
Nguyen TV. Effects of a medical emergency team on reduction prediction of outcomes of scoring systems is not greater than that
of incidence of and mortality from unexpected cardiac arrests in of the individual clinician’s judgment.
hospital: preliminary study. BMJ. 2002;324(7334):387-390.
• Downar J, Barua R, Rodin D, et al. Changes in end of life care
5 years after the introduction of a rapid response team: a multi-
centre retrospective study. Resuscitation. 2013;84(10):1339-1344. Severity-of-illness scoring systems were developed to evaluate the
• Downey AW, Quach JL, Haase M, Haase-Fielitz A, Jones D, delivery of care and predict outcome of groups of critically ill patients
Bellomo R. Characteristics and outcomes of patients receiving a admitted to intensive care units (ICUs). The purpose of this chapter
medical emergency team review for acute change in conscious is to review the scientific basis for these scoring systems and to make
state or arrhythmias. Crit Care Med. 2008;36(2):477-481. recommendations for their use. While there is a growing recognition
• DeVita MA, Smith GB, Adam SK, et al. “Identifying the hospi- that when properly administered, these tools are useful in assessing and
talised patient in crisis”—a consensus conference on the afferent comparing patient populations with diverse critical illnesses, their use
limb of rapid response systems. Resuscitation. 2010;81(4):375-382. for predicting individual patient outcome remains controversial and
• Hillman K, Chen J, Cretikos M, et al. Introduction of the medical unresolved.
emergency team (MET) system: a cluster-randomised controlled • Novel propensity scoring systems and case:control matching strat-
trial. Lancet. 2005;365(9477):2091-2097. egies have also been developed and are now commonly used to
• Niven DJ, Bastos JF, Stelfox HT. Critical care transition pro- simulate clinical trials to assess efficacy and safety of therapeutics in
grams and the risk of readmission or death after discharge from critical care.
an ICU: a systematic review and meta-analysis. Crit Care Med.
2014;42(1):179-87. PURPOSES OF SCORING SYSTEMS
• Peberdy MA, Ornato JP, Larkin GL, et al. Survival from in- There are six major purposes of severity-of-illness scoring systems
hospital cardiac arrest during nights and weekends. JAMA.
2008;299(7):785-792. (Table 13-1). First, scoring systems have been used in randomized
controlled trials (RCTs) and other clinical investigations to assess bal-
ance of treatment and control groups at baseline. The second purpose
1-5
of severity-of-illness scoring systems is to quantify severity of illness
REFERENCES for hospital and health care system administrative decisions such as
resource allocation and accreditation. The third purpose of scoring
Complete references available online at www.mhprofessional.com/hall systems is to assess ICU performance and compare the quality of

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