Att G.15 SSI

Procedure-associated Events
SSI

Surgical Site Infection (SSI) Event
Introduction: In 2002, in the United States, an estimated 14 million NHSN operative procedures
were performed (CDC unpublished data). SSIs were the second most common healthcareassociated infection, accounting for 17% of all HAIs among hospitalized patients1. A similar rate
was obtained from NHSN hospitals reporting data in 2006-2008 (16,147 SSI following 849,659
operative procedures) with an overall rate of 1.9%.2
While advances have been made in infection control practices, including improved operating room
ventilation, sterilization methods, barriers, surgical technique, and availability of antimicrobial
prophylaxis, SSIs remain a substantial cause of morbidity and mortality among hospitalized
patients. In one study, among nearly 100,000 HAIs reported in one year, deaths were associated
with SSIs in more than 8,000 cases.3
Surveillance of SSI with feedback of appropriate data to surgeons has been shown to be an
important component of strategies to reduce SSI risk.4,5,6,7 A successful surveillance program
includes the use of epidemiologically-sound infection definitions and effective surveillance
methods, stratification of SSI rates according to risk factors associated with SSI development, and
data feedback.5,6 Recommendations are outlined in the CDC’s Guideline for Prevention of Surgical
Site Infection, 1999. 7
Settings: Surveillance will occur with surgical patients in any inpatient/outpatient setting where the
selected NHSN operative procedure(s) are performed.
Requirements: Select at least one NHSN operative procedure category (Table 1) and indicate this
on the Patient Safety Monthly Reporting Plan (CDC 57.106). Collect numerator and denominator
data on all procedures included in the selected procedure categories for at least one month.
The International Classification of Diseases, 9th Revision Clinical Modifications (ICD-9-CM)
codes, which are defined by the ICD-9 Coordination and Maintenance Committee of the National
Center for Health Statistics and the Centers for Medicare and Medicaid Services (CMS), are
developed as a tool for classification of morbidity data. The preciseness of the data, as well as their
wide use, allows their use in grouping surgery types for the purpose of determining SSI rates. ICD9-CM codes are updated annually in October and NHSN operative procedure categories are
subsequently updated and changes shared with NHSN users. Table 1: NHSN Operative Procedure
Category Mappings to ICD-9-CM Codes below outlines operative procedures and their grouping
into NHSN operative procedure categories according to ICD-9-CM codes. In addition, for certain
NHSN operative procedure categories, Current Procedural Terminology (CPT) code mapping is
provided. A general description of the types of operations contained in the NHSN operative
procedure categories is also provided.

January 2012

9-1

Procedure-associated Events
SSI

Table 1. NHSN Operative Procedure Category Mappings to ICD-9-CM Codes and CPT
Codes
Legacy
Code
AAA

AMP

Operative
Procedure
Abdominal
aortic
aneurysm
repair
Limb
amputation

APPY

Appendix
surgery

AVSD
BILI

Shunt for
dialysis
Bile duct, liver
or pancreatic
surgery

BRST

Breast surgery

January 2012

Description
Resection of abdominal
aorta with anastomosis or
replacement

ICD-9-CM Codes / CPT Codes
38.34, 38.44, 38.64

Total or partial amputation
or disarticulation of the
upper or lower limbs,
including digits
Operation of appendix (not
incidental to another
procedure)
Arteriovenostomy for renal
dialysis
Excision of bile ducts or
operative procedures on the
biliary tract, liver or
pancreas (does not include
operations only on
gallbladder)

84.00-84.19, 84.91

Excision of lesion or tissue
of breast including radical,
modified, or quadrant
resection, lumpectomy,
incisional biopsy, or
mammoplasty

9-2

47.01, 47.09, 47.2, 47.91, 47.92,
47.99
39.27, 39.42
50.0, 50.12, 50.14, 50.21-50.23,
50.25, 50.26, 50.29, 50.3, 50.4,
50.61, 50.69, 51.31-51.37, 51.39,
51.41-51.43, 51.49, 51.51, 51.59,
51.61-51.63, 51.69, 51.71, 51.72,
51.79, 51.81-51.83, 51.89, 51.9151.95, 51.99, 52.09, 52.12, 52.22,
52.3, 52.4, 52.51-52.53, 52.5952.6, 52.7, 52.92, 52.95, 52.96,
52.99
85.12, 85.20-85.23, 85.31-85.36,
85.41-85.48, 85.50, 85.53-85.55,
85.6, 85.70-85.76, 85.79, 85.9385.96
19101, 19112, 19120, 19125,
19126, 19300, 19301, 19302,
19303, 19304, 19305, 19306,
19307, 19316, 19318, 19324,
19325, 19328, 19330, 19340,
19342, 19350, 19355, 19357,
19361, 19364, 19366, 19367,
19368, 19369, 19370, 19371,
19380

Procedure-associated Events
SSI

Legacy
Code
CARD

Operative
Procedure
Cardiac
surgery

CEA

Carotid
endarterectomy

CBGB

Coronary
artery bypass
graft with both
chest and
donor site
incisions

CBGC

Coronary
artery bypass
graft with chest
incision only

CHOL

Gallbladder
surgery

COLO

Colon surgery

Incision, resection, or
anastomosis of the large
intestine; includes large-tosmall and small-to-large
bowel anastomosis; does
not include rectal operations

CRAN

Craniotomy

Excision repair, or
exploration of the brain or
meninges; does not include
taps or punctures

January 2012

Description
Procedures on the heart;
includes valves or septum;
does not include coronary
artery bypass graft, surgery
on vessels, heart
transplantation, or
pacemaker implantation

ICD-9-CM Codes / CPT Codes
35.00-35.04, 35.06, 35.08, 35.1035.14, 35.20-35.28, 35.31-35.35,
35.39, 35.42, 35.50, 35.51, 35.53,
35.54, 35.60-35.63, 35.70-35.73,
35.81-35.84, 35.91-35.95, 35.9835.99, 37.10-37.12, 37.31-37.33,
37.35-37.37, 37.41, 37.49, 37.60*

Endarterectomy on vessels
38.12
of head and neck (includes
carotid artery and jugular
vein)
Chest procedure to perform 36.10-36.14, 36.19
direct revascularization of
the heart; includes obtaining
suitable vein from donor
site for grafting
Chest procedure to perform
direct vascularization of the
heart using, for example the
internal mammary
(thoracic) artery
Cholecystectomy and
cholecystotomy

9-3

36.15-36.17, 36.2

51.03, 51.04, 51.13, 51.21-51.24
47480, 47562, 47563, 47564,
47600, 47605, 47610, 47612,
47620,
17.31-17.36, 17.39, 45.03, 45.26,
45.41, 45.49, 45.52, 45.71-45.76,
45.79, 45.81-45.83, 45.92-45.95,
46.03, 46.04, 46.10, 46.11, 46.13,
46.14, 46.43, 46.52, 46.75, 46.76,
46.94
44140, 44141, 44143, 44144,
44145, 44146, 44147, 44150,
44151, 44160, 44204, 44205,
44206, 44207, 44208, 44210
01.12, 01.14, 01.20-01.25, 01.28,
01.29, 01.31, 01.32, 01.39, 01.41,
01.42, 01.51-01.53, 01.59, 02.1102.14, 02.91-02.93, 07.51-07.54,
07.59, 07.61-07.65, 07.68, 07.69,
07.71, 07.72, 07.79, 38.01, 38.11,
38.31, 38.41, 38.51, 38.61, 38.81,
39.28

Procedure-associated Events
SSI

Legacy
Code
CSEC
FUSN

Operative
Procedure
Cesarean
section
Spinal fusion

FX

Open reduction
of fracture

GAST

Gastric surgery

HER

Herniorrhaphy

HPRO

Hip prosthesis

January 2012

Description
Obstetrical delivery by
Cesarean section
Immobilization of spinal
column
Open reduction of fracture
or dislocation of long bones
with or without internal or
external fixation; does not
include placement of joint
prosthesis

Incision or excision of
stomach; includes subtotal
or total gastrectomy; does
not include vagotomy and
fundoplication
Repair of inguinal, femoral,
umbilical, or anterior
abdominal wall hernia; does
not include repair of
diaphragmatic or hiatal
hernia or hernias at other
body sites

Arthroplasty of hip

9-4

ICD-9-CM Codes / CPT Codes
74.0, 74.1, 74.2, 74.4, 74.91, 74.99
81.00-81.08
79.21, 79.22, 79.25, 79.26, 79.31,
79.32, 79.35, 79.36, 79.51, 79.52,
79.55, 79.56
23615, 23616, 23630, 23670,
23680, 24515, 24516, 24538,
24545, 24546, 24575, 24579,
24586, 24587, 24635, 24665,
24666, 24685, 25337, 25515,
25525, 25526, 25545, 25574,
25575, 25607, 25608, 25609,
25652, 27236, 27244, 27245,
27248, 27254, 27269, 27283,
27506, 27507, 27511, 27513,
27514, 27535, 27536, 27540,
27758, 27759, 27766, 27769,
27784, 27792, 27814, 27822,
27826, 27827, 27828
43.0, 43.42, 43.49, 43.5, 43.6,
43.7, 43.81, 43.82, 43.89, 43.91,
43.99, 44.15, 44.21, 44.29, 44.31,
44.38-44.42, 44.49, 44.5, 44.6144.65, 44.68-44.69, 44.95-44.98
17.11-17.13, 17.21-17.24, 53.0053.05, 53.10-53.17, 53.21, 53.29,
53.31, 53.39, 53.41-53.43, 53.49,
53.51, 53.59, 53.61-53.63, 53.69
49491, 49492, 49495, 49496,
49500, 49501, 49505, 49507,
49520, 49521, 49525, , 49550,
49553, 49555, 49557, 49560,
49561, 49565, 49566, 49568,
49570, 49572, 49580, 49582,
49585, 49587, 49590, 49650,
49651, 49652, 49653, 49654,
49655, 49656, 49657, 49659,
55540
00.70-00.73, 00.85-00.87, 81.5181.53
27125, 27130, 27132, 27134,
27137, 27138, 27236, 27299

Procedure-associated Events
SSI

Legacy
Code
HTP
HYST

Operative
Procedure
Heart
transplant
Abdominal
hysterectomy;
Includes that
by laparoscope

Description
Transplantation of heart

ICD-9-CM Codes / CPT Codes
37.51-37.55

Removal of uterus through
abdominal wall; includes
that by laparoscope

68.31, 68.39, 68.41, 68.49, 68.61,
68.69
58150, 58152, 58180, 58200,
58210, 58541, 58542, 58543,
58544, 58548, 58570, 58571,
58572, 58573, 58951, 58953,
58954, 58956
00.80-00.84, 81.54, 81.55
27438, 27440, 27441, 27442,
27443, 27486,
27487

KPRO

Knee
prosthesis

Arthroplasty of knee

KTP

Kidney
transplant
Laminectomy

Transplantation of kidney

55.61, 55.69

Exploration or
decompression of spinal
cord through excision or
incision into vertebral
structures
Transplantation of liver

03.01, 03.02, 03.09, 80.50, 80.51,
80.53, 80.54†, 80.59, 84.60-84.69,
84.80-84.85

30.1, 30.21, 30.22, 30.29, 30.3,
30.4, 31.45, 40.40-40.42

LAM

LTP
NECK

Liver
transplant
Neck surgery

NEPH

Kidney surgery

OVRY

Ovarian
surgery

Major excision or incision
of the larynx and radical
neck dissection; does not
include thyroid and
parathyroid operations
Resection or manipulation
of the kidney with or
without removal of related
structures
Operations on ovary and
related structures

PACE

Pacemaker
surgery

Insertion, manipulation or
replacement of pacemaker

PRST

Prostate
surgery

Suprapubic, retropubic,
radical, or perineal excision
of the prostate; does not
include transurethral
resection of the prostate

January 2012

9-5

50.51, 50.59

55.01, 55.02, 55.11, 55.12, 55.24,
55.31, 55.32, 55.34, 55.35, 55.39,
55.4, 55.51, 55.52, 55.54, 55.91
65.01, 65.09, 65.12, 65.13, 65.2165.25, 65.29, 65.31, 65.39, 65.41,
65.49, 65.51-65.54, 65.61-65.64,
65.71-65.76, 65.79, 65.81, 65.89,
65.92-65.95, 65.99
00.50-00.54, 17.51, 17.52, 37.7037.77, 37.79-37.83, 37.85-37.87,
37.89, 37.94-37.99
60.12, 60.3, 60.4, 60.5, 60.61,
60.62, 60.69

Procedure-associated Events
SSI

Legacy
Code
PVBY

REC

RFUSN
SB

Operative
Procedure
Peripheral
vascular
bypass surgery
Rectal surgery

Refusion of
spine
Small bowel
surgery

Description
Bypass operations on
peripheral arteries

ICD-9-CM Codes / CPT Codes
39.29

Operations on rectum

48.25, 48.35, 48.40, 48.42, 48.43,
48.49-48.52, 48.59, 48.61-48.65,
48.69, 48.74
81.30-81.39

Refusion of spine
Incision or resection of the
small intestine; does not
include small-to-large
bowel anastomosis
Resection or manipulation
of spleen
Noncardiac, nonvascular
thoracic surgery; includes
pneumonectomy and hiatal
hernia repair or
diaphragmatic hernia repair
(except through abdominal
approach)

SPLE

Spleen surgery

THOR

Thoracic
surgery

THYR

Thyroid and/or
parathyroid
surgery

Resection or manipulation
of thyroid and/or
parathyroid

VHYS

Vaginal
hysterectomy;
includes that
by laparoscope
Ventricular
shunt

Removal of uterus through
vagina; includes that by
laparoscope

VSHN

XLAP

Abdominal
surgery

January 2012

Ventricular shunt
operations, including
revision and removal of
shunt
Abdominal operations not
involving the
gastrointestinal tract or
biliary system; includes
diaphragmatic hernia repair
through abdominal
approach

9-6

45.01, 45.02, 45.15, 45.31-45.34,
45.51, 45.61-45.63, 45.91, 46.01,
46.02, 46.20-46.24, 46.31, 46.39,
46.41, 46.51, 46.71-46.74, 46.93
41.2, 41.33, 41.41-41.43, 41.5,
41.93, 41.95, 41.99
32.09, 32.1, 32.20-32.23, 32.25,
32.26, 32.29, 32.30, 32.39, 32.41,
32.49, 32.50, 32.59, 32.6, 32.9,
33.0, 33.1, 33.20, 33.25, 33.28,
33.31-33.34, 33.39, 33.41-33.43,
33.48, 33.49, 33.98, 33.99, 34.0134.03, 34.06, 34.1, 34.20, 34.26,
34.3, 34.4, 34.51, 34.52, 34.59,
34.6, 34.81-34.84, 34.89, 34.93,
34.99, 53.80-53.84
06.02, 06.09, 06.12, 06.2, 06.31,
06.39, 06.4, 06.50-06.52, 06.6,
06.7, 06.81, 06.89, 06.91-06.95,
06.98, 06.99
68.51, 68.59, 68.71, 68.79

02.21*, 02.22, 02.31-02.35, 02.39,
02.42, 02.43, 54.95^

53.71, 53.72, 53.75, 54.0, 54.11,
54.12, 54.19, 54.3, 54.4, 54.51,
54.59, 54.61, 54.63, 54.64, 54.7154.75, 54.92, 54.93

Procedure-associated Events
SSI

*NOTE: The procedure represented by this ICD-9-CM code can be performed in a number of ways.
However, as for all surgeries, if, at the end of the procedure, the skin incision edges do not meet
because of drains, wires, or other objects extruding through the incision, the incision is not
considered primarily closed. Therefore, the procedure is not considered an NHSN operative
procedure and any subsequent infection is not considered a procedure-associated infection (i.e., not
an SSI or PPP).
†NOTE: If this procedure is performed percutaneously, it is not considered an NHSN operative
procedure and should not be included in LAM denominator data.
^

NOTE: Include only if this procedure involves ventricular shunt.

For a complete mapping of all ICD-9-CM codes to their assignment as an NHSN operative
procedure category, a surgical procedure other than an NHSN operative procedure (OTH), or a nonoperative procedure (NO), see ICD-9-CM Procedure Code Mapping to NHSN Operative Procedure
Categories at http://www.cdc.gov/nhsn/library.html.
Definitions:
An NHSN operative procedure is a procedure
1) that is performed on a patient who is an NHSN inpatient or an NHSN outpatient; 2) takes place
during an operation (defined as a single trip to the operating room (OR) where a surgeon makes at
least one incision through the skin or mucous membrane, including laparoscopic approach, and
closes the incision before the patient leaves the OR; and 3) that is included in Table 1.
*NOTE: If the skin incision edges do not meet because of wires or devices or other objects
extruding through the incision, the incision is not considered primarily closed and therefore the
procedure is not considered an operation. Further, any subsequent infection is not considered a
procedure-associated infection (i.e., not an SSI or PPP).
NHSN Inpatient: A patient whose date of admission to the healthcare facility and the date of
discharge are different calendar days.
NHSN Outpatient: A patient whose date of admission to the healthcare facility and date of
discharge are the same calendar day.
Operating Room (OR): A patient care area that met the Facilities Guidelines Institute’s (FGI) or
American Institute of Architects’ (AIA) criteria for an operating room when it was constructed or
renovated.8 This may include an operating room, C-Section room, interventional radiology room,
or a cardiac catheterization lab.
Implant: A nonhuman-derived object, material, or tissue that is placed in a patient during an
operative procedure. Examples include: porcine or synthetic heart valves, mechanical heart, metal
rods, mesh, sternal wires, screws, cements, internal staples, hemoclips, and other devices. Nonabsorbable sutures are excluded because Infection Preventionists may not easily identify and/or
differentiate the soluble nature of suture material used.

January 2012

9-7

Procedure-associated Events
SSI

For surveillance purposes, this object is considered an implant until it or the area/structures
contiguous with the implant are manipulated for diagnostic or therapeutic purposes. If infection
develops after such manipulation, do not attribute it to the operation in which the implant was
inserted; instead attribute it to the latter procedure. If the latter procedure is an NHSN operative
procedure, subsequent infection can be considered SSI if it meets criteria. If the latter procedure is
not an NHSN operative procedure, subsequent infection cannot be considered an SSI but may meet
criteria for other HAI and be reported as such.
REPORTING INSTRUCTIONS:
• Some products are a combination of human- and nonhuman-derived materials, such as
demineralized human bone matrix with porcine gel carrier. When placed in a patient during an
operative procedure, indicate “Yes” for the Implant field.
A superficial incisional SSI must meet one of the following criteria:
Infection occurs within 30 days after the operative procedure
and
involves only skin and subcutaneous tissue of the incision
and
patient has at least one of the following:
a. purulent drainage from the superficial incision.
b. organisms isolated from an aseptically obtained culture of fluid or tissue from the superficial
incision.
c. at least one of the following signs or symptoms of infection: pain or tenderness, localized
swelling, redness, or heat, and superficial incision are deliberately opened by surgeon, and
are culture-positive or not cultured. A culture-negative finding does not meet this criterion.
d. diagnosis of superficial incisional SSI by the surgeon or attending physician.
NOTE: There are two specific types of superficial incisional SSIs:
1. Superficial Incisional Primary (SIP) – a superficial incisional SSI that is identified in
the primary incision in a patient that has had an operation with one or more incisions
(e.g., C-section incision or chest incision for CBGB)
2. Superficial Incisional Secondary (SIS) – a superficial incisional SSI that is identified
in the secondary incision in a patient that has had an operation with more than one
incision (e.g., donor site [leg] incision for CBGB)
REPORTING INSTRUCTIONS:
• Do not report a stitch abscess (minimal inflammation and discharge confined to the points of
suture penetration) as an infection.
• Do not report a localized stab wound infection as SSI. While it would be considered either a
skin (SKIN) or soft tissue (ST) infection, depending on its depth, it is not reportable under this
module.
• “Cellulitis”, by itself, does not meet the criteria for Superficial Incisional SSI.

January 2012

9-8

Procedure-associated Events
SSI

•
•
•
•

If the incisional site infection involves or extends into the fascial and muscle layers, report as a
deep-incisional SSI.
Classify infection that involves both superficial and deep incision sites as deep incisional SSI.
An infected circumcision site in newborns is classified as CIRC. Circumcision is not an NHSN
operative procedure. CIRC is not reportable under this module.
An infected burn wound is classified as BURN and is not reportable under this module

A deep incisional SSI must meet one of the following criteria:
Infection occurs within 30 days after the operative procedure if no implant is left in place or within
one year if implant is in place and the infection appears to be related to the operative procedure
and
involves deep soft tissues (e.g., fascial and muscle layers) of the incision
and
patient has at least one of the following:
a. purulent drainage from the deep incision but not from the organ/space component of the
surgical site
b. a deep incision spontaneously dehisces or is deliberately opened by a surgeon and is culturepositive or not cultured and the patient has at least one of the following signs or symptoms:
fever (>38°C), or localized pain or tenderness. A culture-negative finding does not meet this
criterion.
c. an abscess or other evidence of infection involving the deep incision is found on direct
examination, during reoperation, or by histopathologic or radiologic examination
d. diagnosis of a deep incisional SSI by a surgeon or attending physician.
NOTE: There are two specific types of deep incisional SSIs:
1. Deep Incisional Primary (DIP) – a deep incisional SSI that is identified in a primary
incision in a patient that has had an operation with one or more incisions (e.g., C-section
incision or chest incision for CBGB)
2. Deep Incisional Secondary (DIS) – a deep incisional SSI that is identified in the
secondary incision in a patient that has had an operation with more than one incision
(e.g., donor site [leg] incision for CBGB)

REPORTING INSTRUCTIONS:
• Classify infection that involves both superficial and deep incision sites as deep incisional SSI.
An organ/space SSI involves any part of the body, excluding the skin incision, fascia, or muscle
layers, that is opened or manipulated during the operative procedure. Specific sites are assigned to
organ/space SSI to further identify the location of the infection. The table below lists the specific
sites that must be used to differentiate organ/space SSI. An example is appendectomy with
subsequent subdiaphragmatic abscess, which would be reported as an organ/space SSI at the
intraabdominal specific site (SSI-IAB). Specific sites of organ/space (Table 2) have specific
criteria which must be met in order to qualify as an NHSN event. These criteria are in addition to
the general criteria for organ/space SSI and can be found in Chapter 17.

January 2012

9-9

Procedure-associated Events
SSI

An organ/space SSI must meet one of the following criteria:
Infection occurs within 30 days after the operative procedure if no implant is left in place or within
one year if implant is in place and the infection appears to be related to the operative procedure
and
infection involves any part of the body, excluding the skin incision, fascia, or muscle layers, that is
opened or manipulated during the operative procedure
and
patient has at least one of the following:
a. purulent drainage from a drain that is placed through a stab wound into the organ/space
b. organisms isolated from an aseptically obtained culture of fluid or tissue in the organ/space
c. an abscess or other evidence of infection involving the organ/space that is found on direct
examination, during reoperation, or by histopathologic or radiologic examination
d. diagnosis of an organ/space SSI by a surgeon or attending physician.
REPORTING INSTRUCTIONS:
• Occasionally an organ/space infection drains through the incision and is considered a
complication of the incision. Therefore, classify it as a deep incisional SSI.
• Report mediastinitis following cardiac surgery that is accompanied by osteomyelitis as SSIMED rather than SSI-BONE.
• If meningitis (MEN) and a brain abscess (IC) are present together after operation, report as SSIIC.
• Report CSF shunt infection as SSI-MEN if it occurs ≤ 1 year of placement; if later or after
manipulation/access, it is considered CNS-MEN and is not reportable under this manual.
• Report spinal abscess with meningitis as SSI-MEN following spinal surgery.
• Episiotomy is not considered an operative procedure in NHSN.
Table 2. Specific sites of an organ/space SSI. Criteria for these sites can be found in the NHSN
Help System (must be logged in to NHSN) or Chapter 17.
Code
Site
Code
Site
BONE Osteomyelitis
JNT
Joint or bursa
BRST Breast abscess or mastitis
LUNG Other infections of the respiratory
tract
CARD Myocarditis or pericarditis
MED
Mediastinitis
DISC Disc space
MEN
Meningitis or ventriculitis
EAR
Ear, mastoid
ORAL Oral cavity (mouth, tongue, or gums)
EMET Endometritis
OREP Other infections of the male or female
reproductive tract
ENDO Endocarditis
OUTI Other infections of the urinary tract
EYE
Eye, other than conjunctivitis
SA
Spinal abscess without meningitis
GIT
GI tract
SINU Sinusitis
HEP
Hepatitis
UR
Upper respiratory tract
IAB
Intraabdominal, not specified
VASC Arterial or venous infection

January 2012

9-10

Procedure-associated Events
SSI

Code
IC

Site
else-where
Intracranial, brain abscess or dura

Code
VCUF

Site
Vaginal cuff

Numerator Data: All patients having any of the procedures included in the selected NHSN
operative procedure category(s) are monitored for signs of SSI. The Surgical Site Infection (SSI)
form (CDC 57.120) is completed for each such patient found to have an SSI. If no SSI events are
identified during the surveillance month, check the Report No Events field in the Missing PA
Events tab of the Incomplete/Missing List.
NOTES:
1. If a patient has several NHSN operative procedures prior to an infection, report the operative
procedure code of the operation that was performed most closely in time prior to the infection
date, unless there is evidence that the infection is associated with a different operation.
2. If a procedure from more than one NHSN operative procedure category was done through a
single incision, attempt to determine the procedure that is thought to be associated with the
infection. If it is not clear (as is often the case when the infection is a superficial incisional
SSI), or if the infection site being reported is not an SSI, use the NHSN Principal Operative
Procedure Category Selection Lists (Table 3) to select which operative procedure to report.
Table 3. NHSN Principal Operative Procedure Category Selection Lists
The following lists are derived from Table 1, NHSN Operative Procedure Categories. The
operative procedures with the highest risk of surgical site infection are listed before those
with a lower risk.
Priority
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18

January 2012

Code
SB
KTP
LTP
BILI
REC
COLO
GAST
CSEC
SPLE
APPY
HYST
VHYS
OVRY
HER
CHOL
AAA
NEPH
XLAP

Abdominal Operations
Small bowel surgery
Kidney transplant
Liver transplant
Bile duct, liver or pancreatic surgery
Rectal surgery
Colon surgery
Gastric surgery
Cesarean section
Spleen surgery
Appendix surgery
Abdominal hysterectomy
Vaginal Hysterectomy
Ovarian surgery
Herniorrhaphy
Gall bladder surgery
Abdominal aortic aneurysm repair
Kidney surgery
Laparotomy

9-11

Procedure-associated Events
SSI

The following lists are derived from Table 1, NHSN Operative Procedure Categories. The
operative procedures with the highest risk of surgical site infection are listed before those
with a lower risk.
Priority
1
2
3
4
5

Code
HTP
CBGB
CBGC
CARD
THOR

Thoracic Operations
Heart transplant
Coronary artery bypass graft with donor incision(s)
Coronary artery bypass graft, chest incision only
Cardiac surgery
Thoracic surgery

Priority
1
2
3

Code
RFUSN
FUSN
LAM

Neurosurgical (Spine) Operations
Refusion of spine
Spinal fusion
Laminectomy

Priority
1
2

Code
VSHN
CRAN

Neurosurgical (Brain) Operations
Ventricular shunt
Craniotomy

Priority
1
2

Code
NECK
THYR

Neck Operations
Neck surgery
Thyroid and or parathyroid surgery

The Instructions for Completion of Surgical Site Infection form (Tables of Instructions, Tables 12
and 2a) includes brief instructions for collection and entry of each data element on the form. The
SSI form includes patient demographic information and information about the operative procedure,
including the date and type of procedure. Information about the SSI includes the date of SSI,
specific criteria met for identifying the SSI, when the SSI was detected, whether the patient
developed a secondary bloodstream infection, whether the patient died, and the organisms isolated
from cultures and the organisms’ antimicrobial susceptibilities.
Denominator Data: For all patients having any of the procedures included in the NHSN Operative
Procedure category(s) selected for surveillance during the month, complete the Denominator for
Procedure form (CDC 57.121). The data are collected individually for each operative procedure
performed during the month specified on the Patient Safety Monthly Surveillance Plan (CDC
57.106). The Instructions for Completion of Denominator for Procedure form (Tables of
Instructions, Table 13) includes brief instructions for collection and entry of each data element on
the form.
NOTES:
1. If procedures in more than one NHSN operative procedure category are performed during the
same trip to the OR even if performed through the same incision, a Denominator for Procedure
(CDC 57.121) record is reported for each NHSN operative procedure category being monitored.

January 2012

9-12

Procedure-associated Events
SSI

For example, if a CARD and CBGC are done through the same incision, a Denominator for
Procedure record is reported for each.
EXCEPTION: If a patient has both a CBGC and CBGB during the same trip to the OR, report
only as a CBGB. Only report as a CBGC when there is a chest incision only. CBGB and CBGC
are never reported for the same patient for the same trip to the OR. For bilateral operative
procedures see #4 below.
2. If procedures of different ICD-9-CM codes from the same NHSN Operative Procedure
Category are performed through the same incision, record only one procedure for that category.
For example, a facility is performing surveillance for both CBGB and CARD procedures. A
patient undergoes an aortocoronary bypass of one coronary vessel (36.11, CBGB) and the
replacement of both the mitral and tricuspid valves (35.23 and 35.27, both CARD) during the
same trip to the OR. You would complete a Denominator for Procedure record for the CBGB
and another one for the CARD because ICD-9-CM codes 35.23 and 35.27 fall in the same
operative procedure category (CARD).
3. If more than one NHSN operative procedure category is performed through the same incision,
record the combined duration of all procedures, which is the time from skin incision to primary
closure.
4. For bilateral operative procedures (e.g., KPRO), two separate Denominator for Procedure (CDC
57.121) records are completed. To document the duration of the procedure, indicate the incision
time to closure time for each procedure separately or, alternatively, take the total time for both
procedures and split it evenly between the two.
5. Laparoscopic hernia repairs are considered one procedure, regardless of the number of hernias
that are repaired in that trip to the OR. In most cases there will be only one incision time
documented for this procedure. If more than one time is documented, total the durations.. Open
[i.e., non-laparoscopic] hernia repairs are reported as one procedure for each hernia repaired via
a separate incision, i.e., if two incisions are made to repair two defects, then two procedures will
be reported. It is anticipated that separate incision times will be recorded for these procedures.
If not, take the total time for both procedures and split it evenly between the two.
6. Following laparoscopic surgeries, if more than one of the incisions should become infected,
only report as a single SSI.
7. If a patient goes to the OR more than once during the same admission and another procedure is
performed through the same incision within 24 hours of the original operative incision, report
only one procedure on the Denominator for Procedure (CDC 57.121) form combining the
durations for both procedures. For example, a patient has a CBGB lasting 4 hours. He returns
to the OR six hours later to correct a bleeding vessel. The surgeon reopens the initial incision,
makes the repairs, and recloses in 1.5 hours. Record the operative procedure as one CBGB and
the duration of operation as 5 hour 30 minutes. If the wound class has changed, report the
higher wound class. If the ASA class has changed, report the higher ASA class.
8. Do not include in the procedural denominators, procedures during which the patient expired in
the operating theatre.

January 2012

9-13

Procedure-associated Events
SSI

Data Analyses: The SIR is calculated by dividing the number of observed infections by the number
of expected infections. The number of expected infections, in the context of statistical prediction, is
calculated using SSI probabilities estimated from multivariate logistic regression models
constructed from NHSN data during a baseline time period to represent a standard population2
NOTE: The SIR will be calculated only if the number of expected HAIs (numExp) is ≥ 1.

While the SSI SIR can be calculated for single procedure categories, and for specific surgeons, the
measure also allows you to summarize your data across multiple procedure categories, while
adjusting for differences in the estimated probability of infection among the patients included
across the procedure categories. For example, you will be able to obtain one SSI SIR adjusting for
all procedures reported. Alternatively, you can obtain one SSI SIR for all colon surgeries (COLO)
only within your facility.
SSI rates per 100 operative procedures are calculated by dividing the number of SSIs by the number
of specific operative procedures and multiplying the results by 100. SSI will be included in the
numerator of a rate based on the date of procedure, not the date of event. Rate calculations can be
performed separately for the different types of operative procedures and stratified by the basic risk
index. SSI rate calculation options are available in the advanced analysis feature of the NHSN
application.
•

Basic SSI Risk Index. The index used in NHSN assigns surgical patients into categories based
on the presence of three major risk factors:
1. Operation lasting more than the duration cut point hours, where the duration cut point is the
approximate 75th percentile of the duration of surgery in minutes for the operative
procedure.
2. Contaminated (Class 3) or Dirty/infected (Class 4) wound class.
3. ASA classification of 3, 4, or 5.
The patient’s SSI risk category is simply the number of these factors present at the time of the
operation.

________________________
1

Klevens RM, Edwards JR, et al. Estimating health care-associated infections and deaths in U.S. hospitals,
2002. Public Health Reports 2007;122:160-166.

2

Yi M, Edwards JR, et al. Improving risk-adjusted measures of surgical site information for the National
Healthcare Safety Network. Infect Control Hosp Epidemiol 2011; 32(10):970-986.

3

Emori TG, Gaynes RP. An overview of healthcare-associated infections, including the role of the
microbiology laboratory. Clin Microbiol Rev 1993;6(4):428-42.
4

Condon RE, Schulte WJ, Malangoni MA, Anderson-Teschendorf MJ. Effectiveness of a surgical wound
surveillance program. Arch Surg 1983;118:303-7.

January 2012

9-14

Procedure-associated Events
SSI

5

Society for Healthcare Epidemiology of America, Association for Professionals in Infection Control and
Epidemiology, Centers for Disease Control and Prevention, Surgical Infection Society. Consensus paper on
the surveillance of surgical wound infections. Infect Control Hosp Epidemiol 1992;13(10):599-605.
6

Haley RW, Culver DH, White JW, Morgan WM, Emori TG, Munn VP. The efficacy of infection
surveillance and control programs in preventing healthcare-associated infections in US hospitals. Am J
Epidemiol 1985;121:182-205.
7

Centers for Disease Control and Prevention. Guideline for prevention of surgical site infection,1999. Infect
Control Hosp Epidemiol, 1999;20(4):247-278.

8

Facilities Guidelines Institute. Guidelines for design and construction of health care facilities. American
Society for Healthcare Engineering; Chicago IL; 2010.

January 2012

9-15