Appendix Table 1: ICD-9 and CPT Categories
Endocrine, nutritional and
metabolic, and immunity disorders
Diseases of the blood and blood
forming organs
Mental disorders
3*
CPT
Description
Operations on the nervous system
Operations on the endocrine
system
Operations on the eye
4*
Operations on the ear
5*
6*
7
Diseases of the nervous system and
sense organs
Diseases of the circulatory system
8*
Diseases of the respiratory system
8*
9
10
Diseases of the digestive system
Diseases of the genitourinary
system
Complications of pregnancy,
childbirth, and the puerperium
Diseases of the skin and
subcutaneous tissue
Diseases of the musculoskeletal
system and connective tissue
congenital anomalies
9
10
Operations on the nose; mouth; and
pharynx
Operations on the respiratory
system
Operations on the cardiovascular
system
Operations on the hemic and
lymphatic system
Operations on the digestive system
Operations on the urinary system
Category
1*
2*
3*
4*
5*
6
11
12*
13
14*
ICD-9
Description
Infections and parasitic diseases
Neoplasms
Category
1*
2*
7
11*
12
13*
14
Operations on the male genital
organs
Operations on the female genital
organs
Obstetrical procedures
Operations on the musculoskeletal
system
15*
Certain conditions originating in the
15*
Operations on the integumentary
perinatal period
system
16*
Symptoms, signs, and ill-defined
16*
Miscellaneous diagnostic and
conditions
therapeutic procedures
17
Injury and poisoning
17*
Other
18*
Supplementary
18
Anesthesia Procedures
ICD-9 = International Classification of Diseases, Ninth Revision; CPT = Current Procedural Terminology
* Category excluded from analysis due to containing too few (<500) patients
Appendix Table 2: Zero-inflated Poisson regression with healthy pregnant women excluded
(n=5242)
Laboratory Results
Medication Orders
Overall
Ratio of
Overall
Ratio of
variable
expected Regression
variable
expected Regression
Variable
Variable value
effect
number
p-value
effect
number
p-value
p-value
of days*
p-value
of days*
ASA Class
<.001†
<.001†
1
1.00
1.00
2
1.80
<.001†
2.39
<.001†
3
3.94
<.001†
5.10
<.001†
4
5.47
<.001†
6.82
<.001†
Sex
0.090
0.004†
Female
1.00
1.00
Male
0.97
0.090
0.93
0.004†
Age
<.001†
<.001†
0.997
<.001†
0.997
<.001†
Emergency Status
<.001†
<.001†
Non-emergent
1.00
1.00
Emergent
0.66
<.001†
0.66
<.001†
Admission Status
<.001†
<.001†
Outpatient
1.00
1.00
Same Day
0.88
<.001†
0.83
0.007†
Inpatient
1.70
<.001†
1.35
<.001†
ICD-9 Category
<.001†
<.001†
2
1.00
1.00
6
1.35
0.032
0.62
0.001†
7
0.42
<.001†
0.43
<.001†
9
1.04
0.271
0.95
0.334
10
1.30
<.001†
1.35
<.001†
11
0.97
0.707
0.64
<.001†
13
0.90
0.087
1.03
0.64
17
0.79
<.001†
0.78
<.001†
CPT Category
<.001†
<.001†
3
1.00
1.00
7
1.86
<.001†
0.72
0.020†
9
1.22
0.163
0.64
0.002†
10
0.91
0.534
0.38
<.001†
12
1.03
0.860
0.44
<.001†
14
1.15
0.298
0.54
<.001†
18
2.23
<.001†
0.82
0.278
*The effects are ratios, obtained by exponentiating the model regression coefficients, of the expected number of
days (with either laboratory results or medication orders) for each level of a variable compared to the reference
level (first row) of that variable, that is, an effect of 2.0 for ASA 3 indicates that ASA 3 is estimated to have 2 times
the number of days as ASA 1. For the “Age” variable the ratio represent the estimated change with in the number of
days with each additional year.
†Statistically significant at the 0.05 significance level