(Chest. 1999;115:64S-70S.)
© 1999
American College of Chest Physicians
Preoperative Issues in Clinical Nutrition*
Stephen A. McClave, MD;
Harvy L. Snider, MD, FCCP and
David A. Spain, MD
* From the Departments of Medicine (Drs. McClave and Snider) and Surgery (Dr. Spain), University of Louisville School of Medicine and Veterans Affairs Medical Center, Louisville, KY.
Correspondence to: Stephen A. McClave, MD, Professor of Medicine, Division of Gastroenterology/Hepatology, University of Louisville School of Medicine, 550 S Jackson St, Louisville, KY 40292
 |
Abstract
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Allowing a patient’s nutritional state to deteriorate through the
perioperative period adversely affects measureable outcome related to
nosocomial infection, multiple organ dysfunction, wound healing, and
functional recovery. Careful preoperative nutritional assessment should
include a determination of the level of stress, an evaluation of the
status of the GI tract, and the development of specific plans for
securing enteral access. Patients already demonstrating compromise of
nutritional status (defined by > 10% weight loss and serum albumin
level < 2.5 g/dL) should be considered for a minimum of 7 to 10 days
of nutritional repletion prior to surgery. Widespread use of total
parenteral nutrition in unselected patients is unwarranted, may
actually worsen outcome, and should be reserved for preoperative
nutritional support only in severely malnourished patients in whom the
GI tract is unavailable. Compared with the parenteral route, use of
perioperative enteral feeding has been shown to provide more consistent
and beneficial results, and can be expected to promote specific
advantages in long-term morbidity and
mortality.
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Introduction
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Deterioration
of nutritional status in the critically ill patient undergoing major
surgery is associated with reduced systemic immunity, exaggerated
stress response, organ system dysfunction, poor wound healing, and
delayed functional recovery. Weight loss, hypoalbuminemia, and other
purported signs of protein calorie malnutrition have long been
predictors of poor surgical outcome.1
2
3
In the past,
perioperative nutritional support has been synonymous with total
parenteral nutrition (TPN). A high rate of septic complications and
negligible impact on patient outcome with this route of therapy have
raised question about the overall utility of nutritional support and
the risk of interfering with the normal adaptive metabolic response to
injury.4
Increasing evidence suggests that the "motor"
of the multiple organ failure sepsis syndrome is the GI tract,
the integrity of which affects immune defenses, organ function, and
whether the stress response is provoked or attenuated.5
Much more consistent and beneficial responses are being seen with the
provision of perioperative nutritional support by the enteral route.
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Comparison of Enteral and Parenteral Nutrition
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A favorable impact on patient outcome with enteral tube feeding
(ETF) compared with TPN has been shown in several prospective
randomized controlled trials (PRCTs) in a variety of disease processes
ranging from trauma,6
7
8
to head injury,9
10
to pancreatitis.11
12
13
The proposed mechanism for this
difference, which has been extrapolated from animal studies, is that
loss of gut integrity with increased translocation of bacterial
products (predominantly Gram-negative coloforms), in combination with a
heightened immune response induced by ischemia or hypotension, results
in activation of the arachidonic acid cascade.14
The
sequence of events is complex and incompletely
understood.15
Evidence suggests that multiple organ
failure sepsis syndrome and the systemic inflammatory response syndrome
result from the immunosuppressive effects of prostaglandin
E2, the proinflammatory action of leukotriene
B4, and the thrombogenic/vasoconstrictive response induced
by thromboxane A2, all of which are released by this
cascade. A second mechanism contributing to septic complications may
involve loss of gut-associated lymphoid tissue with decreased antigen
processing and stimulation of mucosal-associated lymphoid tissue at
distant sites (ie, lung, kidneys).14
Many aspects of this process have been demonstrated in humans in PRCTs
comparing ETF and TPN.14
Compromise of gut integrity with
reduced small-bowel absorption was demonstrated in one study with
decreased D-xylose and vitamin A absorption and increased lactose
intolerance in a control group receiving TPN.9
Attenuation
of the stress response by ETF was shown in one study by a more rapid
return of interleukin-6 levels to normal,6
and in a second
study by reduced acute phase proteins, less systemic endotoxin
exposure, and reduced overall oxidant stress.11
Hyperglycemia and insulin requirements were decreased in two
studies.9
13
Multiple studies have shown reduced cost of
nutrition support.12
13
16
An effect on patient outcome
with ETF has been suggested by reduced rates of nosocomial
infection,6
7
8
12
17
better return of cognitive function
in head injury patients,9
18
and reduced
mortality.6
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Does Deterioration of Nutritional Status Affect Surgical Outcome?
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Opinions on the length of time a previously normal individual can
be starved without adverse effects ranges from as long as 12 to 14 days
to as little as 72 h.4
19
20
21
No PRCTs exist to
support any of these positions. A well-nourished person should have a
7- to 10-day energy and protein reserve, such that starvation alone
over this time period in the absence of severe injury or illness should
be well tolerated.19
While some reports claim that
development of protein calorie malnutrition affecting patient outcome
does not occur until after 12 to 14 days of starvation,4
others contend that the stress and hypermetabolism of critical illness
and major surgery shorten this time period to 5 to 7
days.4
19
Still, others refer to a 72-h window of
opportunity, coinciding with transition from the ebb to flow phase of
injury, after which any benefit from the enteral route of feeding is
lost.21
In a very early report, weight loss was shown to be an indicator of
operative risk in 50 patients undergoing gastric resection for peptic
ulcer disease, where a correlation was seen between preoperative weight
loss and postoperative complications.1
A more recent
prospective study used percent ideal body weight, percent weight loss,
serum albumin level, and arm muscle circumference to evaluate noncancer
patients preoperatively.2
Patients with at least one
abnormality of these markers had a significant increase in the
incidence of overall complications (48% vs 23%, p < 0.05), in
major complications (31% vs 9%, p < 0.05), and in length of stay
(29 vs 14 days, p < 0.05), when compared respectively with patients
in whom all markers were normal.2
In another prospective
study of patients undergoing elective surgery involving resection of a
portion of the upper GI tract, patients with weight loss alone > 10%
faired no worse than control subjects without weight
loss.3
However, those patients with > 10% weight loss
with some evidence of physiologic impairment (defined by abnormal serum
protein levels, maximal inspiratory pressure, hand grip dynanometry, or
body composition) sustained a significantly higher incidence of major
complications (primarily septic).3
In a prospective study
of female patients undergoing surgery for femoral neck fracture, the
thinnest of three groups preoperatively (defined by percent ideal body
weight > 2 SDs below the mean) had significantly lower oral intake, a
more prolonged period of rehabilitation, and a higher overall
mortality.22
Interestingly, nutritional intervention in the perioperative period
does not necessarily reverse the abnormalities in the traditional
markers. Significant improvement in weight, prealbumin levels, and
certain anthropometric measures was seen in response to tube feeding in
severely malnourished, underweight female subjects with femoral neck
fractures when compared with control subjects.22
This
effect was not seen in women who were only moderately malnourished and
underweight.22
Albumin levels that improved after surgery
in a group given dietary supplements compared with control subjects
were probably more related to the reduction in major complications than
the adequacy of caloric provision.23
In a third study,
anthropometric measures and grip dynamometry did not change
significantly in a group receiving preoperative TPN, despite a
clear-cut benefit with reduced postoperative morbidity compared with
control subjects.24
A lack of response in these markers
suggests that they may not always reflect nutritional status and that
they may be insensitive, in the short term, to changes in nutritional
status.24
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Does Nutritional Intervention Affect Surgical Outcome?
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Much of the support for TPN, for the existence of nutrition
support teams, and for the goal of achieving positive nitrogen balance
has been based largely on uncontrolled studies and the basic belief
that life cannot be sustained without nutrient
sustenance.4
The true impact of nutritional intervention
can be ascertained only in PRCTs in which study patients are compared
with control subjects who receive no nutritional therapy. To our
knowledge, only two such studies have shown a clear benefit of
preoperative TPN on hospital course following major
surgery.24
25
In the most quoted study (reported in two
parts),25
26
patients undergoing surgery for GI or
pancreatic cancer who received preoperative TPN with a glucose solution
had a significant twofold decrease in major postoperative complications
and a fourfold decrease in mortality when compared with control
subjects who were treated with IV fluid resuscitation and regular
hospital diet. Interestingly, a third arm of the study included
patients receiving a similar amount of calories via TPN, but one half
of the nonprotein calories given were comprised of
lipids.25
This group had postoperative complications and
mortality that were similar to those of control subjects, suggesting
that any benefit from the preoperative TPN may have been lost by the
immunosuppressive effects of the lipid emulsion.25
26
A
second trial involving a smaller number of patients undergoing
resection of hepatocellular carcinoma demonstrated that preoperative
TPN significantly lowered postoperative morbidity compared with control
subjects receiving no nutritional therapy (34% vs 55%;
p = 0.02).24
Weight loss was less, liver function (as
measured by indocyanine green) was better, and there was a lower
incidence of ascites requiring diuretic therapy in the group receiving
7 days of preoperative TPN.24
The largest study, the
Veterans Affairs Cooperative Study,27
was designed to
substantiate the perioperative use of TPN. It was performed in 395
malnourished (mostly male) patients undergoing abdominal or thoracic
surgical procedures.27
Surprisingly, the TPN group had a
higher percent of infectious complications compared with unfed control
subjects (14.1% vs 6.4%; p = 0.01). Patients who were borderline or
mildly malnourished had no demonstratable benefit from TPN. Only a
subset of severely malnourished patients receiving TPN had fewer
noninfectious complications than control subjects (5% vs 43%;
p = 0.03), complications that were related to healing wounds
(anastomotic leaks, bronchopleural fistulas) and maintaining normal
organ function.27
The experience with postoperative TPN has been dismal. In a PRCT of
patients undergoing major pancreatic resection for malignancy, use of
postoperative TPN was associated with a higher incidence of major
complications compared with no therapy (45% vs 23%;
p < 0.001).28
In a second, larger study of patients
undergoing acute or elective major surgical procedures, no clinical
benefit was seen in those patients receiving postoperative TPN compared
with control subjects receiving no therapy.29
In fact,
20% of study patients developed a protracted, complicated course.
Those patients placed on a regimen of TPN had a higher mortality rate
than control subjects who had a similar complicated course but did not
receive TPN.29
In summarizing the data on perioperative TPN, widespread use in
unselected patients undergoing major surgery is not warranted. Worse
outcome has been shown with use of postoperative TPN alone.
Preoperative TPN for a minimum of 7 to 10 days, particularly in
patients with severe malnourishment, may reduce postoperative
morbidity.
Experience with perioperative enteral nutrition has been much more
consistent with more favorable outcomes, although the PRCTs tend to be
smaller in size and fewer in number. Patients with obstructive jaundice
undergoing percutaneous transhepatic biliary drainage,30
who were randomized to receive a mean of 20 days of preoperative
nutritional hyperalimentation (86% by the enteral route), showed a
decrease in postoperative morbidity from 46.8 to 17.8% (p < 0.05)
and a decrease in mortality from 12.5 to 3.5% (p < 0.05) when
compared with control subjects receiving no additive nutritional
support.30
In a second study,31
malnourished
patients undergoing surgery were randomized to receive preoperative
enteral hyperalimentation or a routine hospital diet. Those patients
receiving nasogastric feeding for 10 days prior to surgery showed a
significant improvement in body weight, serum protein levels, and
multiple anthropometric measures compared with control subjects. Wound
infections were three times more common (37.2% vs 10.4%) and
mortality was doubled (11.7% vs 6.0%) in control subjects compared
with the study patients.31
In a third study, patients with
squamous cell carcinoma of the head and neck were randomized as
outpatients to receive a regular diet with nocturnal supplements for 10
to 21 days prior to surgery, and they were compared with a control
group receiving a regular diet alone.32
Postoperative
complications in the patients who received supplements were one half
those of the control subjects (32% vs 59%).32
Data supporting use of postoperative enteral feeding are more
substantial. One of the more quoted studies in trauma patients compared
a study group placed on a regimen of immediate jejunostomy feeding
after major abdominal trauma with a control group given IV fluid
resuscitation for 5 to 7 days and allowed to return to normal diet on
their own.8
Although a small percentage of patients in
both groups had to be "rescued" with TPN after 7 days, the study
group receiving enteral feeding had a significantly lower incidence of
sepsis than control subjects (26% vs 4%; p < 0.05).8
In a small study of patients undergoing liver transplant, a control
group receiving early postoperative nasoenteric feeding had a
significantly lower incidence of viral infections than control subjects
receiving no additive enteral support (0% vs 17%,
p < 0.05).33
The most impressive data involved two
large studies in women undergoing surgery for femoral neck
fractures.22
23
In the larger study,22
744
women were classified at the time of surgery by anthropometric measures
into one of three groups designated as well-nourished, thin (between 1
and 2 SDs below the mean), and very thin (> 2 SDs below the mean).
Only thin and very thin patients were randomized postoperatively to
receive standard diet with nocturnal tube feeding vs regular diet
during hospitalization to discharge. Results were most dramatic for
those patients in the very thin group, in which study patients
receiving nocturnal feeds had significant reductions in the duration of
their long-term rehabilitation following surgery.22
Mortality was 8% in study patients vs 21.7% in control subjects, but
this difference did not reach significance.22
Enterally
supplemented patients in the thin group also showed significant
reductions in rehabilitation time compared with control
subjects.22
In a similar, but smaller study, elderly women
with femoral neck fractures were randomized to daily oral supplements
in addition to regular diet vs regular diet alone following
surgery.23
The supplements given as nocturnal feeds were
continued throughout their hospital stay for a mean of 32 days. A
favorable clinical outcome (defined by occurrence of 
1 minor and no
major complications) was seen in 56% of study patients vs 13% of
control subjects (p < 0.05), a difference that was sustained
throughout 6 months of rehabilitation.23
In summary, use of perioperative ETF appears to be well tolerated and
more consistently benefits postoperative morbidity and mortality.
Preoperative ETF in the nutritionally compromised patient may be
underutilized in current practice. Accurate nutritional assessment and
preoperative planning of nutritional support are needed for optimal
results.
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Nutritional Assessment
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The term "protein calorie malnutrition" refers to an older
concept based on parameters that have been shown recently to be
impractical, poorly reproducible, insensitive, inappropriate, and
unreliable in distinguishing patients who need aggressive nutritional
support from those who do not.2
19
34
The term might be
better replaced by the concept of risk for nutritional deterioration. A
thin patient undergoing elective cholecystectomy should tolerate
several days of starvation without incident. A trauma patient may be
well nourished immediately before his or her injury, but then may
suddenly be at great risk for deterioration of nutritional status and
in need of aggressive support. Anthropometric measures (ie,
arm muscle circumference, triceps skin-fold thickness, creatinine
height index) are limited by intraobserver and interobserver variation,
right/left arm dominance, and poor sensitivity to sudden changes in
nutritional status.34
Skin tests for cell-mediated
immunity in preoperative patients are of little value due to low
frequency of anergy.2
Visceral protein levels
(ie, albumin, prealbumin, transferrin) are valuable
prognostic indicators for use on initial evaluation and are still used
in most surgical studies to define "malnourished"
patients.27
Fluid shifts, increased vascular permeability,
extravascular extravasation, and change in hepatic prioritization of
protein synthesis induced by the stress response limit serial use of
these proteins as a marker for nutritional status or as a monitor for
adequacy of nutritional support.34
35
Tests to evaluate
body composition such as total body nitrogen or potassium levels, dual
radiographic absorptiometry, or bioelectrical impedance are difficult
to perform in the critically ill patient, are expensive and impractical
outside of the research setting, and may be inaccurate with massive
fluid shifts and hemodynamic instability.19
In contrast,
muscle function testing is probably underutilized. Tests such as hand
grip dynamometry and maximal inspiratory pressure are simple to
perform, inexpensive, sensitive, and may be a valid indicator of
skeletal muscle dysfunction and increased risk for postoperative
complications.19
Weight as a percentage of ideal body
weight (IBW) or as a percentage of weight lost from the patient’s
usual weight is still one of the best markers to identify patients who
may already have compromised nutritional status.1
2
28
A recent proposed revision of the International Classification of
Diseases, ninth revision, codes for protein calorie malnutrition
has simplified nutritional assessment, basing definitions on four
parameters: percent weight loss from usual weight, percent IBW, serum
albumin level, and inability to eat for 
7 days (actual or
predicted).19
Weight lost as a percentage of the
patient’s usual weight is considered mild if 10%, moderate
between 10% and 20%, and severe if 20%.19
Significant marasmus is suggested by actual weight < 85% of IBW.
Serum albumin levels are considered moderately depressed if < 3.2
g/dL, or severely depressed if < 2.5 g/dL.19
Thus,
significantly malnourished patients defined by the parameters of
> 10% weight loss and serum albumin level < 2.5 g/dL, with major
surgery pending, should be considered for at least 7 days of
preoperative nutritional repletion and early postoperative
support.19
A key aspect of nutritional assessment is to define the patient’s
level of stress and degree of critical illness. The APACHE (acute
physiology and chronic health evaluation) III scoring system, Ranson
criteria for pancreatitis, and Adjusted Trauma Index (ATI) scores are
useful for this purpose. An important concept is that subtle changes in
management decisions are more likely to affect patient outcome with
greater degrees of critical illness. In severely ill trauma patients
with ATI > 24, use of the enteral route of feeding was associated
with fewer infections than use of the parenteral route (11.1% vs
47.6%; p < 0.005).17
In patients with lesser disease
severity and ATI scores < 24, no significant differences in rates of
infection were seen between the two routes of nutritional
support.17
Control of hyperglycemia on the first day
following major surgery was shown to significantly impact the incidence
of severe infections later in the hospital course (20% with poor
control and glucose levels > 220 U vs 0% with good control,
p < 0.05).36
By the second postoperative day, when
patients were less critically ill, control of glucose level no longer
affected the incidence of later infections.36
Another key aspect of nutritional assessment is evaluation of the
status of the GI tract. The term "ileus" and slogans such as "if
the gut works, use it" are misleading and their use should be
avoided. These references incorrectly imply that the gut turns off and
on as a single unit. The gut never stops "working" in the sense
that absorption of luminal nutrients probably never stops. It is not
always safe to permit bowel absorption in a patient with
hemodynamic instability or vasopressor therapy who is at risk for
intestinal ischemia. It may be appropriate to delay enteral feeding
until patients are not receiving vasopressive therapy and fully
resuscitated. Gastric tonometry, by indirectly measuring intramucosal
pH, may emerge as a useful tool in reducing the risk of gut wall
ischemia.37
An important factor in tolerance of enteral
feeding is the degree and level at which intestinal contractility has
been maintained. Abdominal bloating or distention, nausea, vomiting, or
high residual volumes in response to feeding may be used to assess
gastric contractility, while passage of stool and flatus may reflect
colonic contractility. Bowel sounds are only an approximate measure of
small-bowel contractility and are not required for low rates of enteral
infusion. Gut disuse, status of intestinal villi, and whether standard
formulas can be assimilated normally are clinical judgments that need
to be made at the bedside.
Energy expenditure and caloric requirements can vary tremendously in
the critically ill patient and may be difficult to determine using only
predictive equations. Critically ill patients monitored over 24 h
can vary up to 35% about a mean level. Daily variability in resting
energy expenditure can range as high as 46% early in hospitalization
when a patient is more critically ill, decreasing to < 12% during
recovery when the patient is in more stable condition.38
Caloric requirements are best measured by indirect calorimetry. Despite
reports of > 200 similar equations described in the literature, none
is more commonly used nor any more accurate (or inaccurate) than the
Harris-Benedict equation.38
The simplified empiric formula
of 22 to 25 kcal/kg of actual body weight per day correlates to
the measured resting energy expenditure in a similar fashion to these
more sophisticated equations.39
Predictive equations,
though, are inherently inaccurate in the individual
patient.38
The importance of accuracy of the nutritional
support regimen is underscored by reports that increased mortality was
seen in pancreatitis patients with a persistently negative nitrogen
balance and in trauma patients with a cumulative 10,000-calorie
deficit.40
41
The most important aspect of nutritional assessment for the patient
anticipating major surgery is to plan the method by which enteral
access is to be secured for postoperative nutritional support. More
options for tube placement are available preoperatively. The procedure
can be done electively without interfering with surgery or it can be
performed intraoperatively. This avoids the situation of performing
endoscopic or radiographic procedures on a patient with poor
postoperative intestinal motility and recent gut anastomoses.
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Enteral Access
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The type of enteral access is determined by the anticipated needs
of a particular patient. The level at which to infuse feeding, duration
of feeding preoperatively and postoperatively, and the need to
simultaneously decompress the stomach are factors that need to be taken
into account when selecting the proper access device. Ultimately, the
decision for the specific tube or placement method is related to local
expertise and physician preferences.
Nasoenteric tubes placed into the stomach or small bowel are ideal for
perioperative feeding in the short term for periods < 30
days.20
In most cases, these tubes can be placed at
bedside with the tip located in the stomach. Jejunal placement should
be considered if there is evidence of significant reflux or tracheal
aspiration, gastroduodenoparesis following major surgery, or
pancreatitis.13
20
Passage into the small bowel may be
facilitated by use of metoclopramide, cisapride, patient positioning,
small-bore tubes, or a tube with an unweighted tip,20
although the success of these maneuvers is questionable.42
In a patient with significant gastroparesis at significant risk for
aspiration, simple placement of the feeding tube past the pylorus may
not be adequate, as duodenal atony may often be present as well.
Although radiographic placement can be expected routinely to deliver
the tube to the distal duodenum, endoscopic placement may be required
to place the tube at or beyond the ligament of
Treitz.43
44
Jejunal placement below the ligament of
Treitz may be facilitated endoscopically by placing the tube over a
guidewire, as opposed to dragging the tube into place.45
Securing the nasoenteric feeding tube, particularly after endoscopic or
radiographic placement, is important, as displacement can occur in 40
to 60% of cases.44
46
47
The mean life span for a feeding
tube remaining in place appears to be about 10
days.20
44
47
Displacement is not always limited to
patients with altered mental status.46
Mittens, arm
boards, abdominal posies, and binders all help in protecting the tube.
Bridling the tube with a small five-gauge neonatal feeding tube can be
done at the bedside, is well tolerated, and may be more preferable to
the patient and physician than suturing the tube to the face. A
hemoclip device may be utilized to clip a string at the end of the tube
to the small-bowel mucosa, to hold the tube temporarily in place until
nausea, vomiting, retching, or intestinal dysmotility subsides.
Placement of a percutaneous endoscopic gastrostomy (PEG) or jejunostomy
(PEJ) tube should be considered for long-term feeding for periods
> 30 days. Placement of a surgical jejunostomy tube with or without a
decompressive gastrostomy should be considered in patients undergoing
certain procedures, such as extensive gastrectomy or pancreatic
debridement. No significant differences in success of placement have
been described for the push, pull, or introducer type of PEG
kits.48
49
A recent prospective comparison of the
effectiveness of PEG vs nasogastric tubes showed that a greater
percentage of prescribed calories were provided with use of the PEG
(93% vs 55%, p < 0.05), due primarily to dislodgement of the
nasogastric tubes.50
Surgical placement of gastrostomy or
jejunostomy tubes in comparison to the percutaneous or nasoenteric
methods has no difference in morbidity, mortality, or overall tube
function, but may incur more expense and require longer recovery
time.20
The Stamm gastrostomy may be the preferred
surgical procedure of choice. The Witzel gastrostomy, in which the tube
is tunneled through the gastric wall toward the fundus, is difficult to
convert later to a PEG/PEJ if intolerance develops. Care should be
taken in selecting the percutaneous or surgical gastrostomy tube, in
the event that gastric feeds are not tolerated and a compatible
jejunostomy tube has to be placed through the existing PEG site. Not
all PEG kits are designed to be easily converted to the PEG/PEJ method.
PEGs may be secured by placing T-fasteners, switching to a button PEG
(such that traction dislodges the connecting tube), or converting to
surgical placement.
|
Conclusion
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Nutritional assessment of the critically ill patient anticipating
a major operation is crucial, as deterioration of nutritional status is
a key factor in surgical outcome. The route, manner, and adequacy of
the nutritional support regimen affects the degree of stress response,
the incidence of nosocomial infection/multiple organ failure, wound
healing, length of hospitalization, and mortality. Patients with
evidence of compromised nutritional status (as suggested by weight loss
and hypoalbuminemia) should be considered for preoperative nutritional
support over a 7- to 10-day period, preferably by the enteral route.
Nutritional assessment in the preoperative period should include a
thorough evaluation of the status of the gut with explicit plans for
placement of enteral access.
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References
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- Borzotta, AP, Osborne, A, Bledsoe, F, et al (1993) Enteral nutritional support enhances cognitive recovery after severe closed head injury. Surg Forum 44,29-31
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Abstract
Introduction
