This document discusses surgical nutrition and fluid balance. It covers causes and consequences of malnutrition in surgical patients, fluid and electrolyte requirements, nutritional needs of surgical patients after procedures like intestinal resection, and methods of providing nutritional support like enteral and parenteral nutrition. It addresses metabolic responses to starvation, trauma, and sepsis. Key aspects covered include nutritional assessment tools, macro and micronutrient needs, monitoring of feeding regimes, and complications like refeeding syndrome.

1. DR FAZAL HUSSAIN
ASSISTANT PROFESSOR
SURGERY
GAJJU KHAN MEDICAL
COLLEGE SWABI

2. SURGICAL NUTRITION AND FLUID
BALANCE

3. LEARNING OBJECTIVES
• To understand
The causes and consequences of malnutrition in the
surgical patient
Fluid and electrolyte requirements in the pre and
postoperative patient
The nutritional requirements of surgical patients and the
nutritional consequences of intestinal resection
The different methods of providing nutritional support and
their complications

4. INTRODUCTION
• Malnutrition is common. It occurs in about 30% of surgical
• patients with gastrointestinal disease and in up to 60% of those in
whom hospital stay has been prolonged because of postoperative
complications. It is frequently unrecognised and consequently
patients often do not receive appropriate support.
• There is a substantial body of evidence to show that patients who
suffer starvation or have signs of malnutrition have a higher risk of
complications and an increased risk of death in comparison with
patients who have adequate nutritional reserves.
• Long-standing protein–calorie malnutrition as seen in cachexia or
general frailty is easy to recognise
• Short-term undernutrition, although less easily recognised,
frequently occurs in association with critical illness, major trauma,
burns or surgery, and also impacts on patient recovery.
• The aim of nutritional support is to identify those patients at risk of
malnutrition and to ensure that their nutritional requirements are met
by the most appropriate route and in a way that minimises
complications.

5. METABOLIC RESPONSE TO STARVATION
• After a short fast, lasting 12 hours or less, most food from the
last meal will have been absorbed. Plasma insulin levels fall
and glucagon levels rise, which facilitates the conversion of
liver glycogen (approximately 200 g) into glucose. The liver,
therefore, becomes an organ of glucose production under
fasting conditions. Many organs, including brain tissue, red
and white blood cells and the renal medulla, can initially utilise
only glucose for their metabolic needs. Additional stores of
glycogen exist in muscle (500 g), but these cannot be utilised
directly. Muscle glycogen is broken down (glycogenolysis) and
converted to lactate, which is then exported to the liver where
it is converted to glucose (Cori cycle). With increasing
duration of fasting (>24 hours), glycogen stores are depleted
and de novo glucose production from non-carbohydrate
precursors (gluconeogenesis) takes place, predominantly in
the liver.

6. • Most of this glucose is derived from the breakdown of amino acids,
particularly glutamine and alanine as a result of catabolism of
skeletal muscle (up to 75 g per day). This protein catabolism in
simple starvation is readily reversed with the provision of exogenous
glucose. With more prolonged fasting, there is an increased reliance
on fat oxidation to meet energy requirements. Increased breakdown
of fat stores occurs, providing glycerol, which can be converted to
glucose, and fatty acids, which can be used as a tissue fuel by
almost all of the body’s tissues. Hepatic production of ketones from
fatty acids is facilitated by low insulin levels and, after 48–72 hours
of fasting, the central nervous system may adapt to using ketone
bodies as their primary fuel source. This conversion to a ‘fat fuel
economy’ reduces the need for muscle breakdown by up to 55 g per
day. Another important adaptive response to starvation is a
significant reduction in the resting energy expenditure, possibly
mediated by a decline in the conversion of inactive thyroxine (T4) to
active tri-iodothyronine (T3). Despite these adaptive responses,
there remains an obligatory glucose requirement of about 200 g per
day, even under conditions of prolonged fasting.

7. • Metabolic response to starvation
• ● Low plasma insulin
• ● High plasma glucagon
• ● Hepatic glycogenolysis
• ● Protein catabolism
• ● Hepatic gluconeogenesis
• ● Lipolysis: mobilisation of fat stores (increased fat oxidation)
–
• overall decrease in protein and carbohydrate oxidation
• ● Adaptive ketogenesis
• ● Reduction in resting energy expenditure (from
approximately
• 25–30 kcal/kg per day to 15–20 kcal/kg per day

8. METABOLIC RESPONSE TO TRAUMA
AND
SEPSIS
• From a nutritional point of view, two factors deserve
emphasis. First, in contrast to simple starvation, patients with
trauma have impaired formation of ketones, and the
breakdown of protein to synthesise glucose
(gluconeogenesis) cannot be entirely prevented by the
administration of glucose. Second, although it is generally
accepted that the metabolic response to trauma and sepsis is
always associated with ‘hypermetabolism’ or
hypercatabolism’, these terms are ill defined and do not
indicate the need for very high-energy intakes. There is no
evidence to show that the provision of high-energy intake is
associated with an amelioration of the catabolic process and it
may indeed be harmful; there is mounting evidence for the
benefits of permissive underfeeding in critically ill surgical
patients.

9. METABOLIC RESPONSE TO TRAUMA AND
SEPSIS
● Increased counter-regulatory hormones: adrenaline,
noradrenaline, cortisol, glucagon and growth hormone
● Increased energy requirements (up to 40 kcal/kg per day)
● Increased nitrogen requirements
● Insulin resistance and glucose intolerance
● Preferential oxidation of lipids
● Increased gluconeogenesis and protein catabolism
● Loss of adaptive ketogenesis
● Fluid retention with associated hypoalbuminaemia

10. NUTRITIONAL ASSESSMENT
• Laboratory techniques
There is no single biochemical measurement that reliably
identifies malnutrition. Albumin is not a measure of
nutritional status, particularly in the acute setting. . Although
a low
serum albumin level (<30 g/L) is an indicator of poor
prognosis,

11. BODY WEIGHT AND ANTHROPOMETRY
Unintentional weight loss of more than 10% of a patient’s
weight in the preceding 6 months is a good prognostic
indicator of poor outcome. Body weight is
frequently corrected for height, allowing calculation of the
body mass index (BMI, defined as body weight in kilograms
divided by height in metres squared. A BMI of less than
18.5 indicates nutritional impairment and a BMI below 15 is
associated with significant hospital mortality.

12. • Anthropometric techniques incorporating measurements of
skinfold thicknesses and mid-arm circumference permit
estimations of body fat and muscle mass, and these are
indirect measures of energy and protein stores.
• Similarly, use of bioelectrical impedence analysis (BIA)
permits estimation of intra- and extracellular fluid volumes.
These techniques are only useful if performed frequently on a
sequential basis in individual patients; in this respect, trends
are much more important than absolute impedance figures. All
of these techniques are significantly impaired by the presence
of edema.

13. CLINICAL
• The possibility of malnutrition should form part of the
workup of all patients. A clinical assessment of nutritional
status involves a focused history and physical
examination, an assessment of risk of malabsorption or
inadequate dietary intake and selected laboratory tests
aimed at detecting specific nutrient deficiencies.
Recently, the British Association of Parenteral and
Enteral Nutrition introduced a malnutrition universal
screening tool (MUST), which is a five-step screening
tool to identify adults who are malnourished or at risk of
undernutrition.

14. MUST TOOL

15. FLUID AND ELECTROLYTES
• Lungs. About 400 mL of water is lost in expired air each 24
hours. This is increased in dry atmospheres or in patients with
a tracheostomy, emphasising the importance of humidification
of inspired air.
• Skin. In a temperate climate, skin (i.e. sweat) losses are
between 600 and 1000 mL/day. 3 Faeces. Between 60 and
150 mL of water are lost daily in patients with normal bowel
function.
• Urine. The normal urine output is approximately 1500 mL/
day and, provided that the kidneys are healthy, the specific
gravity of urine bears a direct relationship to volume. A
minimum urine output of 400 mL/day is required to excrete the
end products of protein metabolism.

17. • Maintenance fluid requirements are calculated approximately
from an estimation of insensible and obligatory losses.
Various formulae are available for calculating fluid
replacement based on a patient’s weight or surface area. For
example, 30–40 mL/kg gives an estimate of daily
requirements
• The following are the approximate daily requirements of
some electrolytes in adults:
• ● sodium: 50–90 mM/day;
• ● potassium: 50 mM/day;
• ● calcium: 5 mM/day;
• ● magnesium: 1 mM/day
• The nature and type of fluid replacement therapy will be
determined by individual patient needs.

18. NUTRITIONAL REQUIREMENTS
• Total enteral or parenteral nutrition necessitates the provision
of the macronutrients, carbohydrate, fat and protein, together
with vitamins, trace elements, electrolytes and water. When
planning a feeding regime, the patient should be weighed and
an assessment made of daily energy and protein
requirements. Standard tables are available to permit these
calculations. Daily needs may change depending on the
patient’s condition. Overfeeding is the most common cause of
complications, regardless of whether nutrition is provided
enterally or parenterally. It is essential to monitor daily intake
to provide an assessment of tolerance. In addition, regular
biochemical monitoring is mandatory.

19. MACRONUTRIENT REQUIREMENTS
• Energy
The total energy requirement of a stable patient with a
normal or moderately increased need is approximately 20–
30 kcal/kg per day. Very few patients require energy
intakes in excess of 2000 kcal/day. Thus, in the majority of
hospitalised patients in whom energy demands from
activity are minimal, total energy requirements are
approximately 1300–1800 kcal/day.

20. • Carbohydrate There is an obligatory glucose
requirement to meet the needs of the central nervous
system and certain haematopoietic cells, which is
equivalent to about 2 g/kg per day. In addition, there is a
physiological maximum to the amount of glucose that
can be oxidised, which is approximately 4 mg/kg per
minute (equivalent to about 1500 kcal/day in a 70-kg
person), with the nonoxidised glucose being primarily
converted to fat. Plasma glucose levels provide an
indication of tolerance. Avoid hyperglycaemia. Provide
energy as mixtures of glucose and fat. Glucose is the
preferred carbohydrate source.

21. • Fats Fats provide a calorically dense product (9 kcal/g) and
are now routinely used to supplement the provision of non-
protein calories during parenteral nutrition. Energy during
parenteral nutrition should be given as a mixture of fat
together with glucose. There is no evidence to suggest that
any particular ratio of glucose to fat is optimal, as long as
under all conditions the basal requirements for glucose (100–
200 g/day) and essential fatty acids (100–200 g/week) are
met. This ‘dual energy’ supply minimizes metabolic
complications during parenteral nutrition, reduces fluid
retention, enhances substrate utilization (particularly in the
septic patient) and is associated with reduced carbon dioxide
production. Immunosuppression are more likely to occur if the
recommended infusion rates (0.15 g/kg per hour) are
exceeded.

22. • Protein The basic requirement for nitrogen in patients
without pre-existing malnutrition and without metabolic
stress is 0.10–0.15 g/kg per day. In hypermetabolic
patients the nitrogen requirements increase to 0.20–0.25
g/kg per day. Although there may be a minority of
patients in whom the requirements are higher, such as
after acute weight loss when the objective of therapy is
long-term repletion of lean body mass, there is little
evidence that the provision of nitrogen in excess of
14 g/day is beneficial.

23. • Vitamins, minerals and trace elements Whatever the
method of feeding, these are all essential components of
nutritional regimes. 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. Supplemental vitamin B12 is often indicated in
patients who have undergone intestinal resection or gastric
surgery and in those with a history of alcohol dependence.
Absorption of the fat-soluble vitamins A, D, E and K is
reduced in steatorrhoea and the absence of bile. Sodium,
potassium and phosphate are all subject to significant losses,
particularly in patients with diarrhoeal illness. heir levels need
daily monitoring and appropriate replacement. Trace elements
may also act as cofactors for metabolic processes. Normally,
trace element requirements are met by the delivery of food to
the gut and so patients on longterm parenteral nutrition are at
particular risk of depletion. Magnesium, zinc and iron levels
may all be decreased as part of the inflammatory response.
Supplementation is necessary to optimise utilisation of amino
acids and to avoid refeeding syndrome.

25. MONITORING OF FEEDING REGIMES

26. ARTIFICIAL NUTRITIONAL SUPPORT
• Any patient who has sustained 5 days of inadequate
intake or who is anticipated to have no or inadequate
intake for this period should be considered for nutritional
support

27. • Enteral nutrition The term ‘enteral feeding’ means
delivery of nutrients into the gastrointestinal tract. The
alimentary tract should be used whenever possible. This
can be achieved with normal food, oral supplements (sip
feeding) or with a variety of tube feeding techniques
delivering food into the stomach, duodenum or jejunum.
A variety of nutrient formulations are available for enteral
feeding. These vary with respect to energy content,
osmolarity, fat and nitrogen content and nutrient
complexity.

28. • Sip feeding Commercially available supplementary sip
feeds are used in patients who can drink but whose
appetites are impaired or in whom adequate intakes
cannot be maintained . There is good evidence to
demonstrate that these sip-feeding techniques are
associated with a significant overall increase in calorie
and nitrogen intakes without detriment to spontaneous
nutrition.

29. • Tube-feeding techniques Enteral nutrition can be achieved
using conventional nasogastric tubes (Ryle’s), fine-bore
feeding tubes inserted into the stomach, surgical or
percutaneous endoscopic gastrostomy (PEG) or, finally,
postpyloric feeding utilizing nasojejunal tubes or various types
of jejunostomy. There is some evidence that this might reduce
the incidence of nosocomial pneumonia and aspiration.
Nasogastric tubes are appropriate in a majority of patients. If
feeding is maintained for more than a week or so, a fine bore
feeding tube is preferable.
• If patients require enteral nutrition for prolonged periods (4–6
weeks), then PEG is preferable to an indwelling nasogastric
tube; this minimises the traumatic complications related to
indwelling tubes. PEG does have procedure-specific
complications, although these are uncommon. A persistent
gastric fistula can occur on removal of a PEG if it has been in
place for prolonged periods and epithelialisation of the tract
has occurred. This necessitates surgical closure

31. • Parenteral nutrition Total parenteral nutrition (TPN) is
defined as the provision of all nutritional requirements by
means of the intravenous route and without the use of
the gastrointestinal tract. Parenteral nutrition is indicated
when energy and protein needs cannot be met by the
enteral administration of these substrates. The most
frequent clinical indications relate to those patients who
have undergone massive resection of the small intestine,
who have intestinal fistula or who have prolonged
intestinal failure for other reasons.

32. • Peripheral feeding Peripheral feeding is appropriate for
short-term feeding of up to 2 weeks. Access can be achieved
either by means of a dedicated catheter inserted into a
peripheral vein and maneuvered into the central venous
system (peripherally inserted central venous catheter (PICC)
line) or by using a conventional short cannula in the wrist
veins. The former method has the advantage of minimizing
inconvenience to the patient and clinician. PICC lines have a
mean duration of survival of 7 days. The disadvantage is that
when thrombophlebitis occurs. Peripheral feeding is not
indicated in whom long-term feeding is anticipated.

33. • Central Line When the central venous route is chosen,
the catheter can be inserted via the subclavian or
internal or external jugular vein. There is good evidence
to show that the safest means of establishing central
venous access is by insertion of lines under ultrasound
guidance.Most favour cannulation of internal or external
jugular veins as these vessels are easily accessible.The
infraclavicular subclavian approach is more suitable for
feeding as well.

35. REFEEDING SYNDROME
• This syndrome is characterised by severe fluid and electrolyte
shifts in malnourished patients undergoing refeeding. It can
occur with either enteral or parenteral nutrition, but is more
common with the latter. It results in hypophosphataemia,
hypocalcaemia and hypomagnesaemia. These electrolyte
disorders can result in altered myocardial function,
arrhythmias, deteriorating respiratory function, liver
dysfunction, seizures, confusion, coma, tetany and death.
Patients at risk include those with alcohol dependency, those
suffering severe malnutrition, anorexics and those who have
undergone prolonged periods of fasting. Treatment involves
matching intakes with requirements and assiduously avoiding
overfeeding. Calorie delivery should be increased slowly and
vitamins administered regularly. Hypophosphataemia and
hypomagnesaemia require treatment.