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568 PART 5: Infectious Disorders

and Drug Administration has approved the use of PCT for risk assess- TABLE 64-2 Comparison of Severity Index
ment for day 1 of ICU admission to determine progression of severe
sepsis and septic shock, designating less than 0.5 ng/mL and greater than APACHE IV SAPS III SOFA MPM0-III
2 ng/mL as low and high risk for illness severity respectively. PCT has Age Age Age
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also been studied as a marker in a pilot antibiotic stewardship program.
Nobre et al stopped antibiotic therapy when there was greater 90% drop ICU admission diagnosis ICU admission ICU admission diagnosis
in PCT level after 3 days on antibiotics and found a 4-day reduction in diagnosis
antibiotic use, and a 2-day decrease in ICU length of stay, without an Chronic disease Chronic disease Chronic disease
increase in recurrent infections or death. This study excluded immu- Patient location prior to Patient location
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nosuppressed patients or patients with prolonged infections like endo- ICU admission prior to ICU
carditis or osteomyelitis. PCT is the most promising sepsis biomarker admission
to date; however, the assay availability and consensus on how the PCT Nonelective surgery
absolute values should be interpreted and used for clinical judgment is
still undecided. Emergency surgery
To date, there is no single biomarker that provides sufficient diagnos- Length of stay before ICU
tic discrimination either to diagnose or to exclude sepsis. It remains to Mechanical ventilation Mechanical ventilation
be seen whether any biomarker may improve the diagnostic or prognos- within 1 h of admission
tic abilities to what is currently used, such as physical and laboratory CPR 24 h before admission
examinations, and illness scoring systems (see the section Severity index
scores). Given the complexity of sepsis and the common approach to Full code status
integrate multiple pieces of information in decision making for these Physiologic variables
patients, the next approach may be to analyze a group of markers Temp Temp
together in combination. 66 MAP SBP MAP SBP
Severity Index Scores: There are several prognostic severity illness scor- HR HR HR
ing systems that have been studied and validated to risk stratify criti- GCS GCS GCS Coma
cally ill patients on the first ICU day. These include Acute Physiology RR
and Chronic Health Evaluation (APACHE II), Simplified Acute
Physiology Score (SAPS II), Sequential Organ Failure Assessment Pa O 2 /Fi O 2 Fi O 2 and Pa O 2 if Pa O 2 /Fi O 2
(SOFA), and Mortality Prediction Model (MPM-0). Each of these ventilated
scoring systems allows clinicians to predict the likelihood of an Serum bilirubin Serum bilirubin Serum
adverse clinical outcome, such as death. Although they have differ- bilirubin
ing strengths and weaknesses, they universally suffer from the same Serum sodium Serum sodium
basic problem: they only accurately predict outcomes for a group Serum potassium Serum potassium
of patients and not for an individual patient. However, they do
permit institutional benchmarking for quality improvement, and they Serum creatinine Serum
allow clinical researchers to compare treatment effects across patient creatinine or
populations controlling for illness severity or organ dysfunction. urine output
Here we discuss select severity scoring systems as they relate to sepsis WBC WBC
(Table 64-2). Platelet
■ THE ACUTE PHYSIOLOGY AND CHRONIC HEALTH EVALUATION BUN BUN count

The first part of the APACHE scoring system is the Acute Physiology Urine output mL/24 h Urine output
Score (APS). It calculates the probability of hospital mortality based on arterial pH
the main diagnosis and takes into account 33 physiologic measure- Hematocrit
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ments within the first 24 hours of patient presentation. The scoring
system ranges from 0 to 4 for each of the 33 physiologic measurements. Serum bicarbonate
The scoring is based on the worst vital sign, common laboratory, and Glucose
Glasgow Coma Score derangements in the first 24 hours. It also takes Albumin
into account the patient’s chronic health, evaluating preexisting chronic , fraction of inspired oxygen; GCS,
medical conditions or surgeries that will predispose the patient to an APACHE IV, The Acute Physiology and Chronic Health Evaluation; FiO 2
Glasgow Coma Scale; HR, heart rate; MAP, mean arterial pressure; MPM O-III, Mortality Probability
acute illness. APACHE II was validated in a study of 833 consecutive , partial pressure of arterial oxygen; RR, respiratory rate; SAPS II, Simplified
ICU admissions and produced accurate estimates of death rates and Model III at Zero Hours; PaO 2
Acute Physiology Score; SBP, systolic blood pressure; SOFA, Sequential Organ Failure Assessment; Temp,
prognostication in various disease states. APACHE continues to be temperature; WBC, white blood cell.
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updated. APACHE III takes into account the acute diagnosis, the patient’s
location prior to ICU admission and lead time, while APACHE IV
includes additional chemistries, whether the patient was mechanically primary diagnosis makes this scoring system advantageous, because
ventilated, the ICU admission diagnosis, length of hospital stay before often patients in the ICU have multiple or initially unknown diagnoses.
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ICU admission, and whether emergent surgery was performed. 84,86 However, when this scoring system was validated in a multinational
■ SIMPLIFIED ACUTE PHYSIOLOGY SCORE large clinical trial, the study excluded burn and cardiac patients. It is
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considered the simplest system for measuring ICU performance and
SAPS is a severity scoring system for estimating the risk of hospital death comparing across years. 84
and 3 underlying disease states (hematological malignancy, acquired ■ SEQUENTIAL ORGAN FAILURE ASSESSMENT
using 17 variables: 12 physiologic variables, age, type of admission,
immunodeficiency syndrome, and metastatic cancer). SAPS II provides The development of the SOFA score was established to categorize the
estimated risk of death without a primary diagnosis. Not requiring a degree of organ dysfunction over time and to evaluate morbidity in

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