Nutritional Support Of The Surgical
Patient
Introduction7
Nutrition is an important aspect of the care of the surgical patient. Our role as surgical clinicians, in
conjunction with our Dietetic colleagues, is to ensure that our patients receive this support in the peri-
operative period to enable their bodies to heal themself. The goal of nutritional support in the surgical
patient is to prevent or reverse the catabolic effects of disease or injury. Although several important
biologic parameters have been used to measure the efficacy of nutritional regimens, the ultimate
validation for nutritional support in surgical patients should be improvement in clinical outcome and
restoration of function. The stress of surgery or trauma increases protein and energy requirements by
creating a hypermetabolic, catabolic state. A redistribution of macronutrients (fat, protein, and
glycogen) from the labile reserves of adipose tissue and skeletal muscle to more metabolically active
tissues such as liver, bone, and visceral organs occurs. This response can lead to the onset of protein
calorie malnutrition (defined as a negative balance of 100g of nitrogen and 10,000 kcal) within a few
days and affect the host metabolism, immune defence mechanisms and inflammatory response. Such
alterations of the homeostasis may lead to impaired tissue healing and organ function and eventually
to a poor outcome.
Nutritional Assessment1-4
There are four components to a nutritional assessment:
1. Clinical assessment 3. Laboratory studies
2. Anthropometry 4. Dietary intake.
In order to make a holistic assessment, it is recommended that the above modalities be used in
combination.
1. CLINICAL ASSESSMENT
History of significant unintentional weight loss (≥ 10% of usual body mass), anorexia, weakness,
catabolic disorders which raise nutritional requirements (e.g. pancreatitis, burns, head injuries and
sepsis) and a history of eating difficulty (dysphagia, vomiting, etc.).
A bedside physical examination is conducted to identify features suggestive of malnutrition. These
include muscle wasting, loose or abnormal skin, oedema, motor weakness, loss of body fat,
depigmentation of skin and hair, angular stomatitis and pallor, amongst others. A limitation of this
modality is its subjectivity.
2. ANTHROPOMETRY
The limitations of these modalities are in the presence of oedema and the need for special equipment
and the expertise to operate them.
i. Body Mass Index (BMI) (Kg/m2)
BMI is correlated with body fat and is relatively unaffected by height.
Category BMI Implications
Normal 18.5 – 25
Underweight 16 - 18.4 associated with longer hospital stay
Severe Underweight <16 significant increase in morbidity
Overweight 25 – 29.9 associated with higher incidence of
Obesity > 30 cardiovascular disease, diabetes,
Severe Obesity > 40 or increased rate of infectious complication
>35 + Co-morbidities and venothromboembolism
1
, ii. Mid–arm muscle circumference
• < 23cm in males indicates malnutrition.
• < 22cm in females indicates malnutrition.
iii. Triceps skin fold thickness
• <10mm in males may indicate need for nutritional support.
• < 13mm in females may indicate need for nutritional support.
iv. Hand Grip Dynamometry
Simple test of muscle function. Motivation to perform the test maximally is an important factor
and variables such as age, gender body frame, muscular development and musculoskeletal
condition also play a role.
v. Body composite analysis – Bioelectrical impedance analysis (BIA)
BIA is a commonly used method for estimating body composition, and in particular body fat.
Since the advent of the first commercially available devices in the mid-1980s the method has
become popular owing to its ease of use, portability of the equipment and its relatively low cost
compared to some of the other methods of body composition analysis. It is familiar in the
consumer market as a simple instrument for estimating body fat. BIA actually determines
the electrical impedance, or opposition to the flow of an electric current through body tissues
which can then be used to calculate an estimate of total body water (TBW). TBW can be used to
estimate fat-free body mass and, by difference with body weight, body fat. BIA is non-invasive,
relatively inexpensive, does not expose to ionising radiation, has very limited inter observer
variation, and can be performed on almost any subject because it is portable. BIA works well in
healthy subjects and chronically ill, with a validated BIA that is appropriate with regard to age, sex
and race.
3. LABORATORY EVALUATION
• Plasma proteins
Three serum measures of protein status have differing half-lives. These serum components do not
directly indicate nutritional status, but may rather reflect the severity of illness and must be used in
conjunction with other clinical data such as the duration of the current surgical illness to be useful in
determining therapy. Although decreased levels for these protein markers correlate with adverse
outcomes, improvements in these markers with nutritional supplementation are not reliably
associated with a clinical benefit.
Serum Albumin Has the longest half-life at 18 to 20 days and is the most extensively used
parameter. Low serum albumin (<35 g/L) is a marker of a negative
catabolic state, and a predictor of poor outcome. Surgery decreases serum
albumin levels, as do other acute stresses, and hepatic and renal diseases.
Serum Transferrin Has an intermediate half-life of eight to nine days, reflecting protein status
over the past two to four weeks. Transferrin also reflects iron status, and
low transferrin (<1,5g/l) should be considered an indicator of protein status
only in the setting of normal serum iron.
Serum Prealbumin Has the shortest half-life at two to three days. Although prealbumin
(Transthyretin) responds quickly to the onset of malnutrition and rises rapidly with
adequate protein intake, the level can be altered in the acute phase response
due to acute or chronic inflammation. In general, inflammatory cytokines
reduce the level of prealbumin synthesis by the liver and it can also be
reduced with renal and hepatic disease. Therefore, it is the least helpful of
the three for assessing overall nutritional status.
Other: Retinol-binding Protein
• Creatinine Height Index (CHI)
Urinary excretion of creatinine (U-Cr) is an indicator of muscle mass and total body nitrogen. The
24 hour urinary creatinine excretion of a subject is compared to a control/ideal subject of the same
sex and height and this ratio is expressed as a percentage of age. Subjects must have normal renal
function.
2
, Formula:
CHI = (Measured U-Cr over 24 hrs x 100)/Ideal U-Cr over 24 hrs)
CHI < 80% is abnormal, CHI < 50% indicates severe muscle wasting.
• Other helpful laboratory tests: Electrolytes, glucose, and BUN/creatinine will help assess overall
clinical and volume status and are necessary if parenteral nutrition will be instituted. Iron levels
should be measured in the setting of unexplained anaemia, as should specific vitamin levels if
clinically indicated (eg: B12/folate in macrocytic anaemia’s). Serum calcium, magnesium, and
phosphorous should also be assessed periodically, particularly in the setting of poor oral intake or
diarrhoea
4. MULTIFACTORIAL NUTRITIONAL ASSESSMENT
Since no one method is accurate a series of tools using different combinations of the components
discussed have been devised.
1. Subjective Global Assessment (SGA)
The SGA provides a systematic method of obtaining a nutritional history and physical examination
and applying clinical judgment to rate a patient’s nutrition.
The history focuses on 5 areas:
1 Weight loss Mild [<5%], Moderate [5 – 10%], Severe [>10%]
in past 6 months
2 Pattern of Weight Loss
3 Dietary intake Normal /abnormal and whether quality of diet is balanced or not.
4 GIT Symptoms in Anorexia, nausea and vomiting, diarrhoea, abdominal pain, etc.
past 2 weeks
5 Metabolic Calculations made and necessary interventions chosen, as determined by the
demands underlying disease process and severity
Physical Assessed as Mild, Moderate or Severe. Loss of subcutaneous fat, muscle wasting
examination and the presence of oedema and/or ascites are noted.
This appraisal is largely subjective, and confounding factors such as neurological disease, oedema and
ascites in congestive cardiac failure or renal disease will limit its accuracy. SGA therefore looks into
the food intake and body composition.
Subjects are then classified as:
• Category A= well nourished
• Category B= suspected malnutrition or moderate
• Category C= severe malnutrition
2. Nutritional Risk Index
This is computed by using the serum albumin concentration and the ratio of actual body weight to
usual body weight.
Formula: NRI = 1.519 X Serum Albumin (g/l) + [41.7 X actual mass (kg)/usual mass (kg)]
>100 No risk
Scores
97.5 – 100 Low risk
83.5 – 97.5 Medium risk
< 83.5 Increased risk for post-operative complications
3. Malnutrition Universal Screening Tool (MUST)
Includes 3 clinical parameters:
Scores 0 1 2
1 BMI > 20 18.5 – 20 < 18.5
2 Weight loss over prev 3–6 months < 5% 5- 10% > 10%
3 Acute illness absent present
RESULTS: 0 = low risk, 1 = medium risk, 2 = high risk
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