Nutrition
Malnutrition
In surgical practice malnutrition is common,
being present before, or occurring after, operations in about 50
per cent of patients, possibly more in some parts of the world.
Preoperative malnutrition may be due to starvation or to
a failure of digestion. Starvation is caused
by:
• difficulty in swallowing food (dysphagia);
• difficulty in retaining
swallowed food (vomiting);
• self-neglect, e.g. in the
elderly and in alcoholics.
Failure of proper digestion may, for example,
be due to pancreatic or biliary disease (carcinoma or jaundice due to stones),
and duodenal and jejunal conditions (fistula or blind-loop syndrome).
Postoperative (post-traumatic) malnutrition is,
in most cases, of a transient nature consequent upon a short period of
starvation and the stress reaction to trauma. Recovery from any nitrogen deficit
(Table 5.1) due to protein catabolism will follow on return to normal feeding.
Any delay in return to a normal diet, such as may be imposed by the dictates of
the operation (oesophagectomy), or a complication (paralytic ileus from
peritonitis), means that severe malnourishment is likely to occur.
severe trauma (burns) and other severe
disturbances of major viscera (pancreatitis) are accompanied by an accelerated
and profound breakdown of tissue proteins.
Protein
in lean tissue is constantly turned over and renewed. Normally the processes of
protein synthesis and breakdown act in equal and opposite directions to keep the
muscle mass in an adult constant — at
In
sepsis, inflammation, trauma and burns, the muscle wasting results from a
massive loss of amino acids from muscle tissue with depressed muscle protein
synthesis and enhanced muscle breakdown. The mechanism is uncertain but injury
and sepsis trigger a co-ordinated series of inflammatory and immune responses
and the stimulation of macrophages to produce cytokines such as tumour necrosis
factor and interleukin-1. These cytokines are associated with proteolysis,
particularly the breakdown of myoflbrillar proteins but only in the presence of
elevated corticosteroid concentrations.
After injury or
surgical operation
There is an increased oxygen and calorie
consumption and a negative nitrogen balance (Cuthbertson). The increase in
resting metabolic expenditure ranges from minimal after uncomplicated surgery to
30 per cent with multiple fractures, 45 per cent in peritonitis and up to 100
per cent in burns. An increase in metabolic rate and protein catabolism of more
than 25 per cent is regarded as a hypercatabolic state.
The
endocrine profile, activated by fear, apprehension and nervous stimuli from
damaged tissues, is altered after stress with an increase in secretion of most
hormones, in turn resulting in changes in substrate handling by the body.
Glycogen
breakdown in muscle and liver is accelerated principally by adrenaline and
glucagon, leading to increased blood glucose levels, while increased cortisol
and glucagon induces gluconeogenesis from amino acids. Lipolysis — fat
breakdown — is increased by growth hormone, glucagon and noradrenaline. Thus
control of glucose levels is impaired and, together with depressed peripheral
clearance, results in ‘the diabetes of injury’.
The
stimulated protein breakdown in the postoperative period is associated with a
change in synthesis rate in the body cell mass, and this results in a negative
nitrogen balance indicating loss of protein derived from muscle and viscera.
Larger losses are seen in muscular athletic men and the smallest losses in
wasted patients. Epidural anaesthesia inhibits the normal postoperative
increases in cortisol, adrenaline, aldosterone and growth hormone, and so may
reduce the negative nitrogen balance. Nitrogen balance may be improved during
enteral or parenteral feeding if the patient can be mobilised.
Studies
following patients for up to 1 year following uncomplicated surgery suggest that
the maximum weight loss occurs after 2 weeks and that normal body composition is
restored after 6 months.
A
particularly unpleasant effect of surgery is the period of mental and physical
tiredness that follows it. It is not a particular problem in patients who feel
well before surgery, but in those with preoperative tiredness, it is worst
postoperatively at the end of the first week; at 4 weeks it is similar to the
initial preoperative level, and it usually disappears after 3 months. Voluntary
muscle functions deteriorate in a similar pattern to fatigue but postoperative
nutrition, which restores
Uncomplicated,
minimally invasive surgery is believed to be associated with minimal
postoperative fatigue and a shortened convalescence. Initial studies suggest
that the neuroendocrine response is similar to a comparable open operation, and
further studies are required to resolve this paradox.
Severe
sepsis is characterised by an increased rate of whole body protein catabolism,
and when prolonged the depletion of visceral protein results in multiple organ
failure. In patients with sepsis, both protein synthesis and catabolism are
increased with a much greater increase in catabolism resulting in protein loss.
The increase in protein synthesis may be the result of increased hepatic protein
synthesis of acute phase proteins. Intermediate metabolism in sepsis is directed
at increasing substrate availability by lipolysis, glycogenolysis, protein
catabolism and hepatic glucose production. Studies in septic patients have
provided evidence that the myoflbrillar proteins, retin and myosin, are
particularly catabolised in sepsis. The principal mediators are tumour necrosis
factor, interleukin-1 and glucocorticoids.
Fat
oxidation increases with sepsis and is the principal source of energy in the
patient with sepsis, while hepatic glucose production occurs despite
hyperglycaemia and a low respiratory quotient. The increased substrate turnover
is accompanied by an increase in resting energy expenditure.
The
effects of malnutrition
include poor wound healing manifesting as wound dehiscence (Chapter 3) and
leaking anastomoses of bowel, delayed callus formation, disordered coagulation,
reduced enzyme synthesis, impaired oxidative metabolism of drugs by the liver,
immunological depression with increasing susceptibility to infection, decreased
tolerance to radiotherapy and cytotoxic chemotherapy, all with the severe
mental apathy and physical exhaustion of the patient.
Some
clinical indications for nutritional support are:
• preoperative
nutritional depletion;
• postoperative
complications:
— ileus more than 4
days,
— sepsis,
— fistula formation;
• intestinal fistula;
• massive bowel resection;
• management of:
— pancreatitis,
— malabsorption
syndromes,
— ulcerative
colitis,
— radiation
enteritis,
— pyloric
stenosis;
• anorexia nervosa;
• intractable vomiting;
• maxillofacial trauma;
• traumatic coma;
• multiple trauma;
• burns;
• malignant disease;
• renal failure;
• liver disease;
• cardiac valve disease.
Asseasment and
management
It is essential for the clinician to be aware
of the need to assess the state of nutrition of a patient and, if malnutrition
is present or threatens, to consider the nutritional requirements, and then to
use methods of sustaining normality or rectifying any deficiency. Between I and
2 per cent of elderly patients have serious subnutrition as a consequence of
inadequate dietary intake.
Assessment
A malnourished patient has a characteristic
appearance, lean and hungry in most cases of starvation, lean and apathetic in
post-traumatic depletion, with a superimposed hectic flush around sunken cheeks
and pinched nose in a hypercatabolic state. The clinician, when placing a
comforting hand on the patient’s shoulder, discerns the bony scapula bereft of
almost all its muscle. However, these clinical observations only detect gross
malnutrition and therefore measurement of the nutritional status is essential
(Goode). The following parameters are included.
1. Body weight. Careful weighing on a bed weighing machine is the
obvious way of detecting the progress or otherwise of the patient. The desirable
weight of the patient can be checked by reference to the appropriate tables, or
by applying the body mass index (BMI) = weight (kg)/height2 (in). A
woman should have an index of 20, 21 or 23, and a man 20.5, 22 or 23.5 according
to size of frame (small, medium or large).
2.
Upper arm circumference. Feeding is indicated if the circumference is
less than 23 cm in females and 25 cm in males.
3.
Triceps skin fold thickness. Using a skin fold caliper, the minimum is 13
mm in females and 10 mm in males.
4.
Serum albumin should not be less than 35 g/litre.
5. Lymphocyte count. Less than 1500/mm3 indicates an impaired
cellular defence mechanism.
6.
Candida skin test. A negative
reaction also means defective cell-mediated immunity.
7.
Nitrogen balance studies. The total nitrogen intake is compared with the
loss from all sources, such as urine, fistula drainage and nasogastric aspirate
(1 litre = 1 g nitrogen). A greater loss than intake indicates a negative
balance and tissue breakdown. A positive balance means anabolism—tissue
synthesis.
Other measurements include those determining
the rate of muscle breakdown, such as urinary creatinine excretion, or
3-methylhistidine excretion. Body potassium and nitrogen are used to assess the
absolute size of the body cell mass. [t4Cj Leucine incorporation is a
measure of the synthesis rate, while serum transferrin is used as a measure of
visceral protein synthesis (needs to be more than 1.5 g/litre).
Nutritional
requirements
These include carbohydrate, fat, protein,
vitamins, minerals and trace elements (Table 5.2).
Energy is provided by carbohydrate and fat. A healthy adult at rest requires
6300—8400 nonprotein kilojoules per day for energy (1500—2000 calories).
Carbohydrate provides 16.8 kJ/g (4.1 kcal/g) and fat 37.8 kJ/g (9.1 kcal/g). The
number of nonprotein kilojoules given should bear a definite relationship to the
nitrogen intake. A typical regime would feature 8400 kJ (2000 kcal) to 13 g N
(about 150 to 1).
Nitrogen requirements. The minimum for dynamic tissue turnover, and so to
keep a healthy adult in positive nitrogen balance, is about 35—40 g of protein
or 5.5—6.5 g of nitrogen per day.
The hypercatabolic patient requiring hyperalimentation may need three or four
times this amount of protein. A daily negative nitrogen balance of 10 g is not
unusual and is equivalent to a loss of 62.5 g of protein or 300 g of muscle
tissue.
Vitamins. Whatever the method of feeding, vitamins are necessary as supplements,
as they are essential for the maintenance of normal metabolic function.
The
water-soluble vitamins B and C act as coenzymes in collagen formation and wound
healing. Postoperatively, the vitamin C requirement increases to 60—80 mg/day.
Preoperative depletion is exacerbated by anorexia, smoking, aspirin and
barbiturate therapy. Vitamin B12 is given 500 micro gram intramuscularly (i.m.)
weekly, particularly to those with initial low levels (coeliac disease,
Crohn’s disease, ileal resection or bypass, blind-loop syndrome, tapeworm
infestation, reduced pancreatic secretion, tropical sprue, excess alcohol
intake, anticonvulsant therapy and after gastric surgery). As the serum folate
falls, especially in those on parenteral nutrition, folinic acid is required
daily in doses of 3—6 mg i.m.
The
fat-soluble vitamins A, D, F and K are reduced in steatorrhoea and the absence
of bile. Vitamin A, 5000 units per week, is required after surgery and, when
appropriate, it enhances the antitumour effect of cyclophosphamide. Vitamin K
5—10 mg i.m. weekly reduces any bleeding tendency. If commercially available
vitamin additives are put into an infusion, the container should be protected
from the light.
Minerals and
trace elements
Sodium, potassium, iron, calcium and magnesium
deficiencies must be identified and made good (Chapter 4). Zinc deficiency is
manifest as a rash on the face and perineum which does not respond to antifungal
therapy, stomatitis which causes disturbance of taste (dysgeusia) and alopecia.
Copper deficiency results in leucopenia and anaemia, while lack of chromium may
give rise to glucose intolerance. The 14 trace elements that are considered
essential for normal enzyme activities include manganese, cobalt, molybdenum and
vanadium. It is to be remembered that long-term parenteral nutrition can result
in depletion.
Methods
of feeding. These are predominantly enteral and less commonly parenteral.
Enteral
nutrition
By mouth
Obviously, as this is the natural way, it
should always be attempted. Only when it is known that this route cannot be used
or is ineffective are other methods considered.
Feeding by mouth demands common sense, cleanliness and compassion on the part of the medical attendants. It is common sense to ensure that an adequate, palatable and varied diet, including all the nutritional requirements, is provided at regular intervals, more frequently than regular meal times if necessary. It is common sense to begin with a liquid diet as soon as bowel sounds return after an abdominal operation, and not, for example, to allow a plate of fish and chips to be put in front of a patient the day after a gangrenous appendix has been removed. Promotion to semisolid (light) and then to more solid food (full diet) follows in steps of 3—7 days according to progress.
Cleanliness in the preparation and serving of food and of the utensils used is of paramount importance in avoiding gastrointestinal infection causing vomiting and diarrhoea. A salmonella infection among elderly patients and children may be a mortal blow.
Compassion is needed to ensure
that the patient actually receives and ingests the proffered food. Food must be
placed within reach of an enfeebled patient. Assistance is often required and
should be freely given. Dental care may be necessary to facilitate oral intake
and false teeth may need consideration. Table 5.3
By nasogastric
tube
Administration
of the feeds is either by gravity or by means of an infusion pump.
Problems of
tube feeding
Gastric emptying should he normal. In ill
patients ensure that the stomach empties by injecting 60 ml water down a
nasogastric tube and aspirate 4-hourly. If after 24 hours fluid is passing
through the stomach, commence feeding for the first day and aspirate
intermittently to ensure that the stomach empties. Then remove the tube and
introduce the fine-bore tube.
Blockage
of a 1-mm bore tube is cleared by flushing through with 2 ml water — do not
add effervescent potassium to the feed as curdling will follow.
Most
fine-bore tubes incorporate a male ‘luer’ lock connector making the
nasogastric drip system incompatible with intravenous lines.
Check
the drip rate hourly.
All
feeds should be stored at 40C until use, not exposed to room
temperature for more than 8 hours and discarded if not used after 12 hours. As
diet kitchens may be a source of Klebsiella
infection, the bacteriological monitoring of feeds is desirable.
Unwanted effects. Nausea, vomiting and pulmonary aspiration are avoided by regulation of
the infusion rate and ensuring initial gastric emptying. Diabetes and
hyperosmolar states are related to high carbohydrate intake with particular
hazard for the established diabetic. Diarrhoea is common and the pathogenesis is
not fully understood, but fluid and electrolytes are secreted into the bowel in
response to a high osmotic load. The use of broad-spectrum antibiotics is also
associated with diarrhoea. Recent studies suggest that osmolality, electrolyte
content and volume of the feed are not
A choice of procedure is to fashion either a
gastrostomy or jejunostomy. The contraindications to the former are:
•
impaired gastric emptying;
•
significant gastro-oesophageal reflux;
•
loss of the gag reflex.
By gastrostomy
(Fig 5.1 and Fig 5.2)
There are two long-term types of gastrostomy:
Stamm and Janeway. An upper abdominal (midline) incision is optimal for giving
the best exposure and the catheter can be placed laterally away from the
incision. The Stamm gastrostomy is the simplest to perform and is particularly
valuable as a temporary procedure or in the patient who is a poor postoperative
When
a quick temporary measure is necessary, the ink-well (Kader—Senn) technique is
valuable. The tube should be large and, as in all gastrostomies, the end of the
tube should be directed towards the fundus.
Complication
rates as high as 30 per cent have been associated with gastrostomy procedures,
reflecting poor nutritional status, impaired wound healing and pulmonary
complications because of immobility. Leakage around the tube can be controlled
by inserting a larger catheter with a balloon and taping the tube with gentle
traction.
The
endoscopic placement of gastrostomy tubes in therapeutic endoscopy is an
innovation during the last decade (Fig 5.3 and Fig
5.4). Percutaneous endoscopic
gastrostomy has reduced the need for the surgical fashioning of a feeding
gastrostomy under general or local anaesthesia. Thus, whenever a surgical
gastrostomy is indicated, a percutaneous endoscopic technique may he used. As
the gastroscope must be passed into the stomach, a complete oesophageal
obstruction will be an absolute contraindication, as are ascites, sepsis,
abnormal clotting and peritoneal dialysis. The patient should have no intake for
8 hours before the procedure. The basic gastrostomy is fashioned in a retrograde
manner from within the stomach. A suture is placed through the anterior
abdominal and gastric wall and brought out through the mouth. A catheter with a
tapered tip is then fixed to the oral end of the suture from the abdominal wall.
The catheter is then delivered through the abdominal wall. The holding sutures
are removed from the abdominal wall after 1 week.
There
is a 3 per cent incidence of major complications, sepsis, puncture of another
viscus such as the colon or the need for a laparotomy. Minor complications in 7
percent of cases include wound infection and circum stomal drainage.
A tract forms within 2 weeks and, if the
catheter is removed, another of similar size may he inserted within a few hours.
By
jejunostomy (Fig 5.5 and Fig 5.6)
There are two types of feeding jejunostomy: a Witzel jejunostomy with
formation of a serosal tunnel, and a needle jejunostomy using a catheter of a
small gauge. The ease of jejunostomy as an adjunct to an intraabdominal
surgical procedure has increased in popularity.
It is of importance to control infusion rates
of nutrients, particularly with a jejunal feed. The perceived benefits of an
enteral pump infusion system include:
• reduced abdominal discomfort;
• decreased incidence of osmotic diarrhoea.
Parenteral
nutrition
Parenteral nutrition by intravenous feeding is
used in less than 4—5 per cent of
all hospital admissions, either when enteral feeding is not possible, or to
supplement deficient enteral feeding. It has been suggested that although the
incidence of serious, noninfectious complications is lower in patients
receiving total parenteral nutrition, the incidence of septic complications is
substantially higher and only in severely malnourished patients do the benefits
outweigh the risks.
Total
parenteral nutrition is particularly complicated by displacement of the
catheter, sepsis, mechanical problems and metabolic derangements — which occur
in up to 10 per cent of postoperative patients.
Intravenous
(i.v.) fat has many immunosuppressive effects:
i.v. long-chain
triglycerides reduce the functions of the reticuloendothelial system and
neutrophils and the ratio of Thelper to T-suppressor cells. Contraindications
include cardiac failure, severe liver disease, disorders of fat metabolism,
uncontrolled diabetes, shock and severe blood dyscrasias. It must be remembered
that total parenteral nutrition is not to be undertaken lightly. It is
potentially hazardous and can be dangerous in inexperienced hands. The formation
of multidisciplinary nutritional care teams
When
planning an intravenous feeding regimen, first
weigh the patient and calculate the fluid
needs for the next
24 hours. Energy and nitrogen intake should be
calculated on
a body weight basis, remembering that daily
needs may
change. Daily biochemical patient monitoring
is essential
(Table 5.4).
Most
feeding teams decide on the nitrogen and energy requirements of their patients,
and tailor-make the feeds
As
most glucose solutions are hypertonic and irritant, they are usually given
through central veins, the cannulation of which requires technical finesse. In
the short term, the nutritional requirements in aseptic patients can be
adequately met with mixtures of amino acids, fat and glucose given peripherally.
Fat buffers the vein wall and sometimes subtherapeutic doses of heparin and
hydrocortisone are given to act locally in the prevention of thrombophlebitis.
The energy requirements of surgical patients have often been overestimated; few
will require more than 8400 kJ (2000 kcal) per day (Macfie).
Technique for
central venous catheter insertion with a skin tunnel (Fig.
5.7)
Percutaneous catheter insertion requires
expertise to prevent the complications which
may occur in one in five attempts. These are air embolism, pneumothorax and
injury to the subclavian artery or brachial plexus because of significant
variation in relationship of the subclavian vein to the clavicle and first rib.
A suhclavian vein cutdown technique may be employed to allow cannulation of the
vein under direct vision. A silicone rubber catheter of 1 mm diameter (Vygon,
Vygon UK Ltd, Uxbridge, UK) is inserted by intraclavicular approach, the
introducer inserted under local anaesthetic through a 1-cm skin incision (A) 2
cm below the midclavicular point. The position of the catheter is checked
radiologically, ensuring the tip is in the superior vena cava or right atrium.
The catheter hub is removed and the introducer withdrawn. The introducer is now
inserted through the skin puncture at (B) about 7 cm below and medial to (A); it
is passed through the subcutaneous tissue to
Commence
feeding using half-strength solution and increase to the desired daily intake
over days. Additives to solutions should be avoided and given through a separate
line, although central mixing in pharmacy allows addition under sterile
conditions into a 3-litre bag delivery system.
Catheter-related
sepsis may occur in up to a third of patients fed parenterally. Skin flora are
important in the pathogenesis of this sepsis and the skin at the site of the
catheter insertion should be swabbed on alternate days. Bacteriological skin
culture shows a strong association between microbial growth, usually Staphylococcus
epidermidis, and the development of catheter-related infection. Factors
known to increase the risk of infection include variation from the strict
nursing protocol for care of the catheter, the age of the patient and the
duration of hospital stay before the institution of parenteral nutrition.
Home parenteral
nutrition
Chronic intestinal failure results in a
failure of adequate nutrient absorption from the gut to maintain body weight.
This may follow extensive bowel resection, multiple high output fistulas,
motility disorders and extensive Crohn’s disease. Such patients require
prolonged nutritional management by a skilled and experienced team. Long-term
home parenteral nutrition depends upon suitable case selection and
Notes
on solutions. Fructose, sorbitol or alcohol solutions are potentially
disadvantageous owing to an associated lactic acidosis or hepatocellular
damage. Fat, isotonic preparations of vegetable oils in water with an
emulsification agent or purified egg phospholipid in lntralipid (to stabilise
the mixture) should not be used 12 hours before blood sampling as they interfere
with analysis. The rate of clearance of intravenous fat is increased after
surgery or when energy demands are high (Feggetter).
The
nitrogen sources are either casein hydrolysates, or laevorotatory isomers of
amino acids. In such solutions, all essential amino acids should be present with
a broad spectrum of the nonessential amino acids. No single amino acid should
predominate since, if its use is inefficient, this will interfere with the use
of the others (Tweedle). In sepsis, renal failure and hepatic failure, the use
of solutions containing only essential amino acids, isoleucine, leucine, valine,
phenylalanine, lysine and tyrosine is under investigation.
Complications.
The initial complications of parenteral feeding arise from malposition of the catheter tip and radiographic confirmation of
the site of the catheter tip is mandatory before infusion. Infection, particularly septicaemia, arises from continuous direct
vascular access and immune depression in malnourished patients, together with
the solutions being ideal bacterial and fungal culture media. Catheter insertion
with strict asepsis, daily care of the entry site cleaned with 1—2 per cent
tincture of iodine and alcohol solutions, and the strict use of the line only
for nutrient solutions all contribute to prevention. However, if a patient
develops an unexplained fever, hypotension, vomiting, diarrhoea, confusion or
seizures, a full clinical examination with appropriate radiology and
bacteriological culture of blood, sputum, urine and swabs of the catheter site
are indicated. If a source of infection is discovered it is treated, but if no
source is found and the fever persists for 24 hours, remove the catheter and
send the tip for bacteriological and fungal culture, Candida albicans, staphylococci or Klebsiella frequently being isolated. Recommence the parenteral
regimen using a new catheter at a fresh site.
Prolonged
use of amino acids and glucose alone will result in essential fatty acid
deficiency, with dermatitis, anaemia and
increased capillary permeability, a complication avoided by the use of
intravenous fat solutions or essential fatty acids rubbed into the skin weekly.
Similarly, hypophosphataemia is seen
with such regimens and accentuated by the use of insulin, resulting in enzyme
defects, adenosine-5’-triphosphate (ATP) deficiency and a shift to the left in
the oxygen dissociation curve. This is prevented by a daily intake of 13 mmol of
potassium dihydrogen phosphate. Table 5.6 lists some clinical syndromes and
biochemical disorders resulting from drug—nutrient interactions and Table 5.7
lists other biochemical complications. Jaundice
occurring during parenteral nutrition is cholestatic, perhaps the result of
sepsis, malnutrition and hypoxia.
Severe
hepatic steatosis is rare during total
parenteral nutrition. However, transient hepatic abnormalities are so common
that some authorities regard it as the most frequent metabolic complication. A
cholestatic picture tends to predominate with increases in alkaline phosphatase
and bilirubin. Elevations of serum transaminases may also be found. Hepatic
biopsy performed in the jaundice phase shows histological evidence of fatty
infiltration, periportal lymphocytic infiltration with bile duct proliferation
and intrahepatic cholestasis or biliary sludging resulting in extrahepatic
obstruction.
The
syndrome differs somewhat between infants and adults. In the former, typical
morphological changes and jaundice, fatty metamorphosis and even cirrhotic
transformation are described, whereas older patients predominantly have enzyme
derangements.
The
patho physiology of hepatic dysfunction is not entirely understood.
Up
to 40 per cent of surgical patients have an elevation of alkaline phosphatase,
particularly if the feeding solution contains more than 214 kJ/kg daily, while
it has been suggested that reduction in carbohydrate intake by increased use
of a fat solution reduces liver dysfunction. In the vast majority of patients,
hepatic function disturbance is both mild and self-limiting and spontaneous
recovery is invariable after cessation of total parenteral nutrition.
In
the patient with jaundice, it is proposed that cyclical nocturnal total
parenteral nutrition reverses abnormalities when replacing continuous parenteral
nutrition. Metabolic acidosis, much
less common if fructose and alcohol are avoided, may arise from infusion of
available hydrogen ions in amino acid solutions and is simply corrected with
sodium bicarbonate solution.