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120 C.P. Delaney and J.M. MacKeigan
Many patients undergoing minor surgery need minimal
investigation, even if they have chronic medical conditions.
Review of current evidence indicates that routine laboratory
tests are rarely helpful except in the monitoring of known disease states. New guidelines have a significant impact on
reducing preoperative testing and have not caused an increase
in untoward perioperative events.
55,56
Historically, ordering
routine preoperative investigations was quite often driven
more by personal experience than by scientific evidence.
This led to inefficient clinical practice, with healthy patients
undergoing useless, time-consuming, costly, and sometimes
harmful procedures. A prospective study found that whereas
16% of results were abnormal, only 0.013% caused a change
in management for 400 patients undergoing elective surgery.
Higher complication rates were significantly associated with
the extent of surgery, but not with abnormal preoperative
blood results. Other studies have also found that only a small
percentage of abnormal preoperative investigations changed
management.
59
This is especially true, as a repeat test is an
adequate response to most abnormal biochemical results
because an abnormal test does not necessarily correlate with
pathology. Because reference intervals of most tests take the
normal distribution and standard deviation of the population
into consideration, cut-off points for normality are set such
that patients whose test results exceed the upper 2.5% of
healthy individuals or are below the lower 2.5% of healthy
individuals are said to have abnormal results. Thus, 5% of
patients whose values are outside the reference range do not
necessarily have disease and may be normal. The greater the
number of tests ordered, the greater the probability of finding
a result outside the reference range.
Age, history of chronic heart disease, renal disease, emergency surgery, and type of operation are predictors of the risk
of mortality.
60
Fit, young patients undergoing minor and intermediate procedures do not need routine preoperative investigations and in the pediatric age group, a thorough clinical
examination has been found to be of greater value than routine
laboratory screening. A good history and physical examination
have been said to be more important rather than laboratory
data in the development of a treatment plan for anesthesia.
Quality cost-effective preoperative preparation of patients
undergoing anesthesia and surgical procedures is a central
issue in perioperative patient management. Minimizing routine preoperative testing results in better utilization of
resources and a greater cost-benefit ratio without adverse
effect to the patient. Review of preoperative evaluation of
patients found that 60% of the amount spent on preoperative
laboratory testing was wasted.
61
False-positive and borderline
tests led to further investigation causing reduced efficiency of
practice, creating the potential for iatrogenic disease and
increasing medicolegal risk. Thus, guidelines for preoperative
testing based on best available evidence are important for efficient resource utilization and prevention of undue surgical
risk to the patient. Although the general consensus is that
screening must be replaced by indicated testing, the danger
identified is that some indicated tests may also be abandoned
in the quest for reducing routine investigations.
62
previous tests helps avoid duplication of tests and also helps
identify potential problems.
Assessment of Specific Organ Systems
Cardiac Evaluation
57
The detection of a rhythm other than sinus and the presence of
premature atrial contractions and frequent premature ventricular contractions increase the risk of perioperative cardiac
13
events.
highly correlated to age but most dysrhythmia can be sus-
58
pected from physical examination.
Cardiology (ACC) and American Heart Association (AHA)
recommendations for preoperative cardiac evaluation consider
the magnitude of the particular procedure being performed and
patient factors that influence perioperative cardiac risk.
History of coronary artery disease, cardiovascular procedures,
and symptoms of angina or congestive heart failure are important. Patients without symptoms and with a normal cardiac
stress test within 2 years or coronary artery bypass graft in the
last 5 years, those who are clinically stable and underwent
angioplasty 6 months to 5 years previously do not need any
further assessment. Patients who had an angioplasty within
6 months and those having emergency surgery may need cardiac evaluation and angiography. Patients with intermediate
risk and poor functional capacity may need stress testing.
Assessment of left ventricular function by radionuclide scan or
echocardiography is also indicated for patients in whom an
impaired left ventricular function is suspected on clinical
examination or radiology although the best test remains
unclear.
with definite clinical predictors identified from history, physical examination, electrocardiogram, and functional status
along with the risk associated with the operation itself. Cardiac
interventions are generally only recommended for patients
who would otherwise have benefited regardless of any
unplanned noncardiac surgery. These recommendations have
been reviewed and summarized by the ACC (www.acc.org/
clinical/guidelines/perio/update/fig1.htm) and others.
Transfusion and Hematologic Evaluation
Most patients with anemia tolerate operations well unless
they have associated disease, and therefore anemia rarely
changes management unless operative blood losses are
expected to be great. Risk of thromboembolism and bleeding
disorders can be assessed by a detailed history and by tests
that measure coagulation factors (prothrombin and partial
thromboplastin time) and that assess platelet count and function (bleeding time). Measures to reduce the risk of thromboembolism have been well documented and are part of the
practice parameters available from the American Society of
Colon and Rectal Surgeons
Yield of electrocardiogram in unselected patients is
63
The American College of
64
Further cardiac evaluation is only needed in patients
66,67
(see Appendix A).
Review of
53,65
8. Preoperative Management—Risk Assessment, Medical Evaluation, and Bowel Preparation 121
Blood grouping and cross-matching is obviously critical
when planning major surgery in which significant blood
losses may occur. An important consideration is to have a routine sample for blood type on file for patients undergoing
major surgery, even if transfusion is not expected, and crossmatching would not usually take place. This allows a double
level of security when urgent samples are sent if bleeding
occurs during surgery. This may help avoid the risk of transfusion reaction if there is concern about errors with sample
labeling or source at any time.
Anemic patients who are scheduled for elective surgery
may be treated preoperatively by allogenic transfusion but
consideration is also given to autologous donation, erythropoietin, intraoperative hemodilution with autotransfusion, or
consideration of cell salvage techniques, which are still being
evaluated in colorectal surgery. Preoperative autologous
donation (PAD) has been criticized recently because of costineffectiveness, large wastage of PAD units, and the potential
for leaving patients more anemic after surgery than without
68
PAD.
Techniques including acute normovolemic hemodilution and cell salvage may be more efficient; however, investigations into their use continue.
69
Renal Function Evaluation
When indicated, measurement of serum electrolytes in the
preoperative period helps in preventing perioperative problems. This is particularly true for serum potassium, because
both hypokalemia and hyperkalemia may lead to cardiac conduction disturbances. Normal renal function is necessary for
the excretion of the nondepolarizing muscle relaxants used
for anesthesia and surgery. Renal function is also a consideration when choosing postoperative analgesic regimens
including nonsteroidal medications such as Ketoralac. Age,
hypertension, and diabetes may be indications for preoperative selective renal function testing.
Respiratory Tract Evaluation
Patients with a history of chronic lung disease require careful
assessment to minimize problems with anesthesia. In addition, patients with grossly normal lungs may rarely develop
respiratory abnormalities secondary to anesthetic agents and
operation. Common pulmonary complications after surgery
are atelectasis, pneumonia, and bronchitis and predisposing
risk factors include cough, dyspnea, smoking, history of lung
disease, obesity, and abdominal or thoracic surgery. Cessation
of smoking 8 weeks before surgery is beneficial to the patient
by allowing recovery of the mucociliary apparatus. Bronchodilators are helpful in patients with asthma and bronchitis.
Active pulmonary infection should be treated before surgery
when possible. A Global Initiative for Chronic Obstructive
Lung Disease (COLD) now recommends optimal treatment
for COLD patients, and these treatments may need to be optimized before surgery.
The incidence of abnormalities detected on a routine preoperative chest film is higher in elderly patients but most
occur in patients with recognizable risk factors. Preoperative
chest X-rays may be of value in ruling out metastases but do
not otherwise have a major influence on the decision to operate or on the type of anesthesia, and abandonment of routine
ordering of preoperative chest X-rays does not produce
70
adverse patient effects.
The Royal College of Radiologists
recommended preoperative chest X-rays only for patients
with acute respiratory symptoms, possible metastases, those
with suspected or established cardiorespiratory disease without a chest X-ray in the preceding 12 months, and recent
migrants from endemic countries. Other studies also suggest
using specific indications for preoperative testing rather than
routine X-rays, culminating in a metaanalysis by Archer and
colleagues.
71
There are no well-established guidelines as to who requires
pulmonary function testing. Such candidates may include
patients with chronic pulmonary disease, wheezing or dyspnea on exertion, chest wall and spinal deformities, morbid
obesity, heavy smokers with persistent cough, thoracic surgery, elderly patients (>70 years of age), and patients who are
to undergo upper abdominal surgery. The American College
of Chest Physicians criteria recommend preoperative spirometry only in patients undergoing lung resection, those who
undergo cardiac and upper abdominal surgery in the presence
of a history of smoking and dyspnea, and patients with pulmonary symptoms and uncharacterized disease scheduled for
prolonged lower abdominal surgery.
Neurologic System
The prevalence of occult cerebrovascular disease in elderly
patients, who constitute a large proportion of patients requiring surgical attention, is a special concern. An asymptomatic
carotid bruit indicates the presence of peripheral vascular disease and is an indication for further evaluation by duplex
scanning. However, prophylactic endarterectomy is not indicated usually, because the increased risk of a perioperative
stroke compared with the unselected population is small.
Symptomatic disease that is untreated or undiagnosed before
preoperative assessment should be assessed and treated
before all but emergency surgery. Patients at high risk may be
kept on aspirin products during the time of surgery to minimize their risk of stroke. Some may require endarterectomy
before their scheduled surgery, although this is quite rare.
Metabolic and Endocrine System
Assessment for diabetes, thyroid disorders, and other
endocrine problems is an integral part of preoperative evaluation. Obesity is now so prevalent that fasting blood glucose in
obese patients may pick cases of unexpected diabetes.
Pregnancy may dictate reassessment of the indication for surgery, type of procedure being performed, and issues related to
anesthesia. Patients on steroids may need extra dosage in the
72
73
122 C.P. Delaney and J.M. MacKeigan
perioperative period. Patients with known diabetes will need
careful management of their blood sugar in the per-operative
period, with standard recommendations for insulin and oral
hypoglycemic use.
Nutritional Assessment and Hepatic Function
Nutritional measurements help in assessing the physiologic
status and optimizing function of the patient with regard to
immunology, fluid balance, and metabolic response to trauma
and surgery. Patients at particular concern for malnutrition are
those who have lost more than 10% of their body weight in the
previous 6 months, and those with an albumin less than 3 g/dL.
Malnourished patients have increased complications after surgery, although nutrition must be supplemented for at least
2 weeks before clinical outcome parameters are improved.
74
Abnormal liver function may affect hemostatic mechanisms and drug metabolism, but is an unusual clinical problem. Significant liver impairment is detectable on certain
standard clinical and laboratory examinations, but is not routinely evaluated biochemically. Hepatitis may pose increased
risk to the medical personnel taking care of the patient.
Preoperative Assessment Specific for Colorectal
Procedures
For patients undergoing surgery for colorectal disorders, a
previous major laparotomy may preclude laparoscopic surgery or indicate an increased risk of conversion to open surgery. Body habitus of the patient, mental status, visual acuity,
and the presence of other disorders such as arthritis may
determine the decision on whether a stoma is formed and its
placement. Assessment of patients’ attitudes toward surgery,
addressing their concerns, and counseling them regarding
what to expect during hospitalization forms an integral part of
the preoperative evaluation.
Current Recommendations
Tests that need to be performed include hemoglobin for evidence of anemia and as a baseline level for postoperative
management. Renal and liver function tests are not routinely
indicated but rather in patients with medical conditions or taking medication that would indicate these tests. Preoperative
blood glucose determination is obtained in patients 45 years
of age or older because current recommendations suggest that
all patients older than 45 years ought to be screened; diabetes
mellitus also increases perioperative risks. A urine pregnancy
test ought to be considered for all women of childbearing age.
Coagulation tests are only indicated in patients on anticoagulation, with a family or personal history of bleeding disorder,
or those with liver disease. Patients undergoing major surgery
with a potential for blood loss should have a type and screen
taken for filing in the laboratory, even if transfusion is not
expected. This may help minimize the risk of later transfusion
reaction.
1,54
Electrocardiogram is indicated in male patients older than
40 years of age, females older than 50 years, and those with a
history suggestive of cardiac disorders. Chest X-rays are performed on the basis of findings from the medical history or
physical examination. As part of preoperative risk assessment, patients found to have medical conditions requiring further specific therapy before surgery should also be considered
for more intensive medical supervision. This is important
while in the hospital for their surgery, and also as part of their
post-discharge follow-up.
Bowel Preparation
The practice of mechanical bowel preparation (MBP) before
surgery has undergone major changes over the last century.
Mechanical preparation became routine for all surgeons by
the start of the 1990s,
oral or intravenous antibiotic prophylaxis. This practice was
thought to offer less risk of anastomotic leak, and to reduce
the risk of wound infection, both postulated to be related to
the bacterial load of stool. There are approximately 10
11
10
anaerobic bacteria and 105to 107aerobic bacteria in the
colon, per gram of stool. The normal colonic flora comprises
approximately 20 species of aerobic bacteria and more than
50 species of anaerobic bacteria. Bacteroides fragilis is the
most frequently cultured species, followed by clostridia and
peptostreptococci, in postoperative infections in colon and
rectal surgery.
Method of Bowel Preparation
The techniques used to mechanically prepare the bowel have
changed hugely over the last 25 years. When Goligher
reported outcomes in the 1970s, patients were restricted to a
liquid diet for 3–5 days, before being given cathartic agents
and enemas.
solution by nasogastric tube while the patient remained on the
commode.
10–14 days. These dietary restrictions were combined with
oral aperients such as castor oil, and the use of enemas before
surgery. Such protocols were associated with problems of
fluid overload, hyponatremia, and nausea and vomiting.
The description of polyethylene glycol (PEG) preparations,
which were minimally absorbed and could irrigate the bowel
effectively, changed MBP practice. Preparation time was
shortened to 1 day by drinking 4 L of a balanced electrolyte
solution which would not be absorbed or metabolized.
Studies quickly showed that PEG provided better bowel
preparation and was more easily tolerated by patients than the
traditional 5-day regimes.
Sodium phosphate was then developed and used to clean
bowel for colonoscopy. Similarly with this product, patient
acceptance was high, because volumes to drink were smaller.
Transient phosphatemia was noted but was rarely a significant
76
77
Others recommended diet restriction for up to
75
and this was used in combination with
9
to
Some authors recommended 10 L of crystalloid
78
8. Preoperative Management—Risk Assessment, Medical Evaluation, and Bowel Preparation 123
event.79The new solution was quickly used for elective
colonic surgery.
80
The preparations were also given at home,
so that patients could come to the hospital the morning of surgery. Although this practice adequately cleans bowel, it does
mean that patients tend to need more fluid resuscitation in the
perioperative period.
81
The lower-volume sodium phosphate
preparations are now used routinely by many surgeons, but
should be avoided in those with significant history of cardiac
or renal dysfunction.
The most recent development is the description of a sodium
phosphate pill. This may now be taken as a series of 28–32
pills on two occasions to give an effective preparation,
although some concerns remain about hydration and electrolyte issues.
results at bowel cleansing for colonoscopy
82
This has been reported to give equivalent
83
; however, many
clinicians do not use this form of preparation because of con-
84
cerns about electrolyte imbalance.
Indeed, any sodium
phosphate preparation may cause hypocalcemia, hyperphosphatemia, and hypokalemia, leading to increased caution for
their use in the elderly and those with renal dysfunction.
Whether to Use an MBP
Over the last decade, several studies have suggested that a
mechanical preparation may not be necessary, and these data
will be reviewed here. Initial studies included several case
series that suggested low anastomotic leak rates could be
obtained without bowel preparation.
reminiscent of the trauma literature suggesting that equally
good or better outcomes could be achieved performing repair
in unprepared bowel.
87
These studies have been accompanied by a series of randomized, controlled trials evaluating the presence or absence
of MBP, culminating in the recent publication of a Cochrane
review on the subject (Table 8-5).
trials over the last decade, two showed higher anastomotic
leak rates with bowel preparation. The remaining trials
showed no difference. Interestingly, some authors suggested
that anastomotic leak may be worse in those who received a
bowel preparation who had a poor result, leaving the colon
loaded with liquid stool. No study showed a worse outcome
in control patients (no preparation).
85,86
These results were
88–94
Of the five randomized
A Cochrane review was performed to analyze all randomized, controlled data and specifically to determine the effect
of MBP on morbidity and mortality rates after elective col-
93
orectal surgery.
Of patients with anastomoses, there were
576 MBP patients and 583 without MBP. There was no difference in anastomotic leak rates for low anterior resection
(12.5% versus 12%), or colonic surgery (1.2% versus 6%) in
patients with or without MBP. Overall anastomotic leak rates
were significantly lower without MBP (5.5% versus 2.9%;
P = .02). Mortality, peritonitis, reoperation, wound infection,
and extraabdominal complications were similar between
groups. The results failed to support the hypothesis that MBP
reduces complication rates, but because there was no a priori
hypothesis that MBP might increase complication rates, this
could not be stated.
These data certainly show the safety of performing anastomosis in unprepared bowel in patients undergoing gynecologic or other surgery who have not had MBP and are found
to have other pathology. Furthermore, this metaanalysis provides important evidence questioning the routine use of MBP
in elective colorectal surgery. Whereas avoidance of bowel
preparation may not be possible for laparoscopic approaches
for technical reasons, it should be considered for open surgery, perhaps especially when using PEG preparations.
94
Bowel Preparation in Special Situations
Obviously, patients with acute intestinal or colonic obstruction cannot be given a high-volume or cathartic bowel preparation. Certain other patients are not suitable for bowel
preparation. Perhaps the most important example are those
with obstructive symptoms, or a chronic partial obstruction.
Most surgeons would avoid a bowel preparation in this circumstance, and if necessary perform an on-table lavage
before anastomosis. This practice is further supported by the
data suggesting that bowel preparation may be unnecessary.
Some surgeons will reserve use of milder preparative
agents for patients with chronic partial obstruction, such as
that seen in cases of longstanding Crohn’s disease. Options
here would include prescribing small volumes of magnesium
citrate, or managing the patient with older regimes, such as
dietary restriction for a longer period of time than overnight.
T
ABLE 8-5. Randomized, controlled trials and Cochrane report relating to preoperative mechanical bowel preparation (all results as MBP ver-
sus no MBP, %)
Author Year n Anastomotic leak Wound infection Mortality
Brownson et al.
Burke et al.
Santos et al.
Miettinen et al.
Zmora et al.
Guenga et al.
Slim et al.
*
Significant result.
89
90
92
93
94
88
91
1992 179 11.9 vs 1.5
1994 169 3.8 vs 4.6 4.9 vs 3.4 2.4 vs 0.0
1994 149 10.0 vs 5.0
2000 267 4.0 vs 2.0 4.0 vs 2.0 0.0 vs 0.0
2003 249 4.2 vs 2.3 6.6 vs 10.0 1.7 vs 0.8
2003 1159 5.5 vs 2.9 7.4 vs 5.7 0.6 vs 0.0
2004 1454 5.6 vs 3.2
*
*
*
5.8 vs 7.5 0.0 vs 0.0
24.0 vs 10.0 0.0 vs 0.0
7.4 vs 5.7 1.4 vs 0.8
124 C.P. Delaney and J.M. MacKeigan
Prophylactic Antibiotic Usage (See
Appendix B)
Removing the bulk of the stool in a patient was believed to
reduce the risk of complications; however, this remained
unproven. Antibiotics were additionally used to further
reduce the risk of wound infection and possibly other complications. In the initial phases, oral antibiotics were used and
given over the days preceding surgery. More recently, there
has been a major shift toward using parenteral antibiotics to
do this job.
Neomycin and erythromycin were initially chosen as suitable oral antibiotics for prophylaxis of wound infection in
colorectal cases. Such oral antibiotics are given at three time
points the day before surgery (1
before surgery for an 8
AM start time), in an effort to sterilize
the bacteria within the bowel lumen. Antibiotics were shown
to reduce bacterial counts by 1000-fold.
inexpensive, largely remained in the bowel lumen, and were
therefore thought to be suitable for this technique.
Erythromycin has now been replaced by metronidazole
because of its improved activity against anaerobes, and less
gastrointestinal side effects. Although these agents can be
effective,
enteral medications.
96
the results can be equaled or bettered by using par-
97
Over the last 20 years, many studies were performed to evaluate parenteral antibiotics for all forms of general surgery, and
also for colorectal indications. Because of differences in trial
design, antibiotics used, and definitions of wound infection
and other outcome parameters, many of these studies are hard
to compare with each other. Over this time, there was an evolution from using antibiotics for 5 days, down to the current
situation in which they are generally given to cover the time of
surgery itself, or used for 24 hours maximum, unless a therapeutic course is indicated for clinical reasons. This effort to
minimize the number of doses of antibiotics that is given has
been supported by microbiologists and infectious disease specialists, in the hope of reducing cases of nosocomial infection
seen in association with prolonged antibiotic usage, particularly that with Clostridium difficile, which is being seen in epidemic proportions in some geographical areas and institutions.
Furthermore, in the 17 trials comparing single-dose to multiple-dose (two or more doses) regimens, using the same antibiotic or combinations of antibiotics, no trial found a difference
in wound infection rates, and a pooled analysis also showed no
statistically significant difference.
also reduces risk of toxicity, costs, and possibility of developing resistance to the antibiotic used.
Further knowledge has also provided awareness that the
essential time to have coverage (adequate systemic levels) with
antibiotics is from the time of incision to the time of skin closure. Thus, prophylactic antibiotics are ideally given at the time
of anesthetic induction, although the randomized, controlled
trials permitted up to 1 hour after this time, and if necessary are
PM, 2 PM, and 11 PM the day
95
These agents were
96
This single-dose policy
98
repeated after 4–6 hours to keep adequate circulating levels,
particularly if there has been significant blood loss.
Antibiotics need to cover Gram positive, negative, and
anaerobic bacteria, and regimes such as ampicillin, gentamicin, and metronidazole used to be typical. Current choices
usually include a second-generation cephalosporin with
metronidazole, or an agent such as amoxicillin/clavulanic
acid which avoids the need for metronidazole. In patients with
penicillin allergy, ciprofloxacin may be used instead of the
cephalosporin, or another alternative would be gentamicin,
clindamycin, and metronidazole, although we prefer to avoid
clindamycin because of concerns with nosocomial infection.
These issues have been excellently reviewed elsewhere in a
systematic review, documenting outcomes for each major
antibiotic combination.
96
A final issue relates to the combination of oral and parenteral agents. Some surgeons like this practice, thinking that
this may further reduce infectious complications. One recent
study has combined a randomized trial comparing oral
neomycin and metronidazole with placebo in colonic surgery
patients receiving parenteral amikacin and metronidazole.
The combination of oral and intravenous antibiotics reduced
wound infection rates, and this was supported by a metaanalysis of prior literature.
99
Prophylaxis for Endocarditis
and Prosthesis
Patients undergoing invasive colorectal procedures are at
varying risk for endocarditis and infection of prosthesis. The
American Society of Colon and Rectal surgeons has published Practice Parameters (Appendix B) to guide surgeons on
selecting appropriate measures for at risk patients. For
Additional discussion, see Chapter 9.
Communication with the Patient
and Laying the Groundwork for
Postoperative Recovery
No preoperative visit is complete without providing information on expected postoperative outcomes. This discussion
helps the patient to build confidence and trust in the surgeon.
Such discussion is likely to be an important component of any
postoperative care pathway, and this may help lead to significant reduction in postoperative stay.
Patients can be advised of the surgery they will undergo,
their expected milestones in recovery, and possible complications, including issues such as readmission, which may occur
in 10% or more of these patients undergoing major abdominal surgery.
103
100–102
8. Preoperative Management—Risk Assessment, Medical Evaluation, and Bowel Preparation 125
Conclusion
Assessment of the patient undergoing surgery is of extreme
importance in providing patients with a safe recovery from
their operation. This permits stratification of patients into
groups that require intensive, moderate, or minimal investigation or treatment before anesthesia. Tests to investigate
patients should be used selectively based on increasingly
accepted guidelines. Patients who need such evaluation and
treatment before surgery should also be seen by the relevant
medical specialty when in the hospital, and receive any
necessary instructions for appropriate medical follow-up after
their surgery.
MBP continues to be used by the majority of colorectal surgeons, based on traditional practice patterns. Several randomized, controlled trials now suggest that this practice may be
unnecessary. Patients undergoing bowel resection should be
given antibiotic prophylaxis using one dose of parenteral
broad-spectrum agents at the time of induction of anesthesia.
Appendix A: Practice Parameters for the
Prevention of Venous Thromboembolism
Risk Classification
Low-risk Patients
The typical low-risk patient is one undergoing minor surgery
who has one or no risk factors. No specific measures are recommended for patients at low risk other than early ambulation. Unprotected, these patients have a 2% chance of calf
vein thrombosis and a negligible risk of pulmonary embolus.
Moderate-risk Patients
The typical moderate-risk patient is older than 40 years of
age, undergoing major abdominal surgery, with no other
major risk factors. Moderate-risk patients can be treated with
either intermittent pneumatic compression (IPC) alone or
low-dose unfractionated heparin (LDUH). Moderate-risk
patients have two risk factors. Unprotected, these patients
have a 10%–20% risk of calf vein thrombosis, and a 1%–2%
chance of a pulmonary embolism.
High-risk Patients
High-risk patients have three or four risk factors. The typical
high-risk patient is older than 40 years of age, is having major
abdominal surgery, and harbors additional risk factors. Highrisk patients can be treated with LDUH (bid or tid) or lowmolecular-weight heparin (LMWH), although standard
unfractionated heparin seems to be more cost effective. If
heparin cannot or should not be used, IPC should be substituted. When heparin has not been started preoperatively, the
patient should be reevaluated for postoperative heparin.
Unprotected, these patients have a 20%–40% risk of calf vein
thrombosis and a 2%–4% risk of pulmonary embolism.
Very High-risk Patients
A high-risk patient is upgraded to a highest-risk category
when certain additional risk factors are present. These include
a history of thromboembolic events, hypercoagulable states,
and possibly malignancy. Assuming no contraindication,
highest-risk patients ideally should receive pharmacologic
treatment such as LDUH (bid or tid) or LMWH. Untreated,
TABLE 8-A.1. Recommendations for VTE prophylaxis by risk classification
Thromboprophylaxis by risk classification
Low Moderate High Highest
Example Ambulatory surgery, Major abdominal sx, age Major abdominal sx, age Major abdominal sx, prior
Calf vein thrombosis 2 10–20 20–40 40–80
(without prophylaxis)
Clinical PE 0.2 1–2 2–4 4–10
Primary prophylaxis None IPC LDUH (q 8–12 h) or LMWH LDUH (q 8–12 h) or LMWH
Alternate prophylaxis None LDUH (q 12 h) or LMWH IPC† Heparin and IPC‡
Figures are percentages.
sx, symptoms; VTE, venous thromboembolism; PE, pulmonary embolism; q 8–12 h, every 8–12 hours.
*
Modified with permission from Clagett GP, Anderson FA Jr, Geerts W, et al. Prevention of venous thromboembolism. Chest 1998;114:531S–560S.
†Intermittent pneumatic compression boots offer prophylaxis where the risk of bleeding is high. Heparin may be started postoperatively after the risk of bleed-
ing has passed.
‡Some data suggest that IPC combined with heparin may offer increased protection. Where the risk of bleeding is high, IPC may be used intraoperatively and
heparin may be added postoperatively after the risk of bleeding has passed.
Prepared by The Standards Task Force, The American Society of Colon and Rectal Surgeons.
Reprinted from The Standards Task Force of the American Society of Colorectal Surgery.
Society of Colon and Rectal Surgeons.
no risk factors > 40 y, no other risk factors > 60 y, additional risk factors VTE, malignancy, or
*
hypercoagulable state
66
Copyright 2003. All rights reserved. American
126 C.P. Delaney and J.M. MacKeigan
these patients have a 40%–80% risk of calf vein thrombosis
and a 4%–10% risk of pulmonary embolism.
Intuitively, there may be some advantage to a strategy of
dual methods, i.e., combining intermittent pneumatic compression with heparin. Several investigators have suggested
this. This has been shown to be efficacious for patients undergoing cardia and hip replacement surgery, but thus far there
are no published data for colon and rectal surgery patients.
Appendix B: Practice Parameters for
Antibiotic Prophylaxis to Prevent Infective
Endocarditis or Infective Prosthesis During
Colon and Rectal Endoscopy
These parameters are based in part on the recently updated recommendations made by the AHA and the previously published parameters developed by The American Society of
Colon and Rectal Surgeons. According to the AHA, the risk
for endocarditis is determined by the patient’s preexisting cardiac condition and the surgical procedure in question. The
major changes in the new AHA guidelines are the following:
1) it was emphasized that invasive procedures are not the cause
of most cases of endocarditis; 2) cardiac conditions are stratified by the potential outcome if endocarditis develops; 3) procedures causing bacteremia are more clearly specified; 4) an
algorithm for antibiotic prophylaxis for patients with mitral
valve prolapse was developed; 5) prophylactic regimens for
oral or dental procedures were modified; and 6) prophylactic
regimens for genitourinary and gastrointestinal procedures
were simplified. The AHA considers lower gastrointestinal
endoscopy to be a low-risk procedure for initiating problematic bacteremia, and The Standards Task Force concurs. The
Task Force considered other direct and indirect support for the
use of antibiotic prophylaxis in patients with cardiac or other
prostheses. It is the consensus of The Standards Task Force
that prophylaxis be considered only for the high-risk groups
listed in Table 8-B.1. The complex nature of individualized
patient care does not allow standards to be spelled out for
every clinical category.
TABLE 8-B.1. Conditions associated with endocarditis (high risk)
Prosthetic cardiac valves
History of endocarditis
Surgically constructed systemic pulmonary shunts
Complex cyanotic congenital heart disease
Vascular grafts (first 6 months after implantation)
Prepared by The Standards Task Force, The American Society of
Colon and Rectal Surgeons.
Reprinted from Dis Colon Rectum 2000;43(9):1193–1200.
Copyright 2003. All rights reserved. American Society of Colon and
Rectal Surgeons.
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