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Chapter: Medicine Study Notes : Surgical and Fluid Management

Nutrition in Surgical Patients

Consequences of malnutrition : ­Perioperative mortality (e.g. in 30 days post surgery)

Nutrition in Surgical Patients


Consequences of malnutrition


·        ­Perioperative mortality (e.g. in 30 days post surgery)

·        ¯Healing


·        ­Respiratory infection

·        ¯Immune function

·        ­Wound infection


Nutritional assessment


·        Observe: thin?, how strong is finger grip

·        History: intake over preceding days compared to normal


·        Anthropomorphic measurement (BMI, girth to hip ratio, skinfold thickness, compare actual to standardised 24 hour urine creatinine excretion.)

·        Lab measurements (albumin, transferrin – only for gross malnutrition)

·        Physiological assessment (PEFR, FEV1, hand grip)


Energy Metabolism


·        Adult needs 25 – 30 kcal/kg/day

 ·  Typical diet gives: CHO – 40 – 60% (4 kcal/g) 

o   Fat: 20 – 45% (9 kcal/g)

·        Protein: 10 – 20 % (4 kcal/g)

·        Excess CHO stored as fat, otherwise broken down to glucose


·        Short & medium chain FFA are directly absorbed into the portal vein: so if gut is malabsorbing, give them this – rapid and easy to absorb


·        During starvation, FFA saturate Kreb‟s cycle ® ketones and acids


Protein Metabolism


·        No body storage.  Used, converted to energy or excreted

·        Maintained by protein intake of 0.8 – 1.0 g/kg/day

·        Nitrogen balance Þ nitrogen in equal nitrogen out

·        Protein is 16% N2


Energy metabolism in Starvation


·        Immediate use: liver and muscle glycogen


·        Early starvation: Gluconeogenesis from AA, glycerol and lactate. Leads to catabolism. Only supports CNS and RBCs


·        After few days: ¯metabolism,­ FFA used by heart, kidneys and muscles

·        Prolonged starvation: brain uses ketones.  Protein catabolism ­ as fat stores used up


Nutritional Requirements


·        Basal Energy Requirement (BEE) for otherwise well and sedentary (­ when challenged by illness):

o  Men = 66 + (13.7 * kg) + (5 * height in cm) – (6.8 * years)

o  Women = 655 + (9.6 * kg) + (1.8 * height in cm) – (4.7 * age)


Nutritional Support


·        Protein/Calorie Requirements

·        Well nourished patients without sepsis or injury: H2O and electrolytes OK for 5 days


·        Non-depleted post-operative patients: 1.2 - 1.5 * BEE + 0.8 – 1.0 g protein/kg/day to prevent catabolism


·        Malnourished patients without sepsis or injury: Cautious repletion – avoid refeeding syndrome due to depletion of co-factors ® marked ¯ in PO4 and Mg – monitor

·        Nutritionally depleted patients: 1.5 – 1.8 g protein/kg/day + 1.5 * BEE


·        Patients with sepsis or injury: Well nourished can manage without feeding for a few days. Malnourished need feeding


Enteral Nutrition


·        Adult energy requirements: 40 Kcal/kg/day (approx. 2,500 Kcal per day)


·        Requirement ­ in sepsis, burns, trauma by 50 – 100 %

·        Protein requirement: 1.5g/kg/day (approx. 105 g protein or 14g N2 per day)

·        Enteral much safer and less expensive compared with parenteral

·        Delivered by: NG tube, nasoduodenal tube (¯risk of aspiration), PEG, jejunostomy

·        Problems: aspiration, tube blockage, diarrhoea due to intolerance/inadequate digestion


·        Feed by pump, starting slowly, at 30 – 45 degrees. Stop at night if they can tolerate increased flow during day

·        Tradeoffs: 

o  When sick, ¯ motility and ¯emptying.  Need to be minimal volume but still flow through tube

o  Don‟t include lactose as ¯lactase when sick.  Lactose would ® diarrhoea

o  ­Osmolar load ® ­diarrhoea. So need ­Mr

·        3 types: 

o  Intact nutrient formulas: Blenderised feedings (don‟t flow well), lactose-free feedings (via tube), and nutrient-dense feedings (flavoured for oral use)

o  Pre-digested Nutrients (elemental diets): taste fowl, use NG tube

o  Feeding modules: concentrated sources of one nutrient (e.g. protein, CHO or fat)


Parenteral Feeding


·        For nutritional support when GI tract can‟t be used


·        Via central line: Total Parenteral Feeding (TPN) has very high osmolality. X-ray after insertion to check no pneumothorax and line is outside pericardium (above anterior third rib) to avoid cardiac tamponade following catheter erosion


·        Complete nutrition: electrolytes, glucose, amino acids, fat emulsion, vitamins, etc. Fat a good way of giving calories without ­glucose (which could ® diabetes)


·        Other major risk: sepsis. Test for coagulase +ive staphylococci. Colony count should be 5 times higher in central line sample than in peripheral blood

·        Metabolic problems common, e.g. hyper or hypo glycaemia, acidosis, etc.  Alter constitution of TNP


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