Surgery SC039: Feed Him Up Before Surgery: Surgical Nutrition, Enteral And Parenteral Feeding Flashcards
Malnutrition
Definition:
1. Gross underweight
- weight for height <80% of ideal weight
2. Recent weight loss of >=10% over 3 months
3. Body mass index 17-18.5
Clinical manifestations of **Gross malnutrition:
Recognised readily by clinical examination
Less severe malnutrition can be detected by **anthropometric + ***laboratory studies
1. Severe wasting
2. Loss of SC fat
Clinical manifestations of ***Severe malnutrition:
1. Loss of cheek fat, obvious intercostal space
2. Sarcopenia (loss of muscle mass)
Effect on outcome of surgery (elective surgery):
- ↑ complication rate 4x
- ↑ mortality rate 6x
Anthropometric + Laboratory studies: Measurement of nutritional status
Measure of Static calorie reserve (i.e. Subcutaneous fat):
1. ***Triceps skinfold
2. Subscapular skinfold
Measure of Static protein reserve (i.e. Muscle mass):
1. ***Midarm circumference
2. Psoas muscle density + area on CT
Measure of Circulating protein status:
1. Long t1/2 protein: ***Albumin
2. Short t1/2 protein: Transferrin, Prealbumin, Retinol-binding protein
Measure of Immune function:
1. Delay hypersensitivity skin reaction
2. ***Total lymphocyte count
***Predisposing factors for Malnutrition
- ↓ Oral intake
- e.g. CA esophagus - ↑ GI loss
- e.g. Intestinal fistula, Diarrhoea - ↑ Catabolism
- e.g. Sepsis, Burn, Acute pancreatitis - Cancer cachexia
Risk of malnutrition to patient
- Hypoproteinaemia
- render patient unable to handle excess salt / water intake
- bowel edema —> inhibit GI function
- wound edema —> inhibit healing (esp. important after surgery)
- prevent normal CVS response to shock (∵ intravascular volume already low) - Muscle wasting
- impair ventilating capacity + susceptibility to ventilatory failure + chest infection (∵ weak respiratory muscles (intercostal + diaphragmatic muscle)) - Impaired cell-mediated immunity
- **susceptibility to infection (∵ lower lymphocyte count, **esp. important after surgery)
Magnitude of weight loss: Rough predictor of its effect on clinical outcome
0-10% weight loss: Limited outcome
10-20%: Significant
20-30%: Serious
30-40%: Life-threatening
40-50%: Lethal
Means to avert malnutrition
- ↑ Nutrient intake
- ↓ Output: Eradicate cause of nutrition
- e.g. drainage of abscess, resection of cancer
***Perioperative nutritional support
Operation:
- Induce ↑ catabolic response to surgery, ↑ proteolysis, ↓ immunocompetence
Intensive nutritional therapy:
- ↓ net catabolic response to surgery
- improve protein synthesis (critical for maintaining muscular, respiratory, metabolic, immunologic function)
Parenteral nutrition efficacy:
- relative risk reduction of 21% for major complication
- relative risk reduction of 32% for case-fatality
- save hospital cost
**Indications:
1. **Malnourished patient undergoing major surgery (minor surgery: delay surgery until nutritional buildup ∵ not life-threatening)
2. Major operations with **long period of fasting (>7 days) after surgery
3. Post-op complications (which render the patient unable to eat)
4. Catabolism
5. **Absent oral food intake
Means:
1. Pre-operative (~2 weeks)
- Oral / Enteral (feeding tube) / Parenteral
- Post-operative
- Parenteral —> then Enteral / Oral
Indications of TPN (Felix Lai)
- Patients who ***cannot use the GIT properly
- Short gut syndrome
- Intestinal obstruction / Paralytic ileus
- Tumours (∵ intestinal obstruction/ cancer cachexia/ increased demands)
- Inflammation of GIT
- Inflammatory bowel disease (IBD)
- Mucositis of intestine following chemotherapy
- Radiation enteritis - Patients who have current / predicted inadequate **increased demands + **Unable to tolerate enteral feeding methods
- GI fistula (∵ malabsorption / increased loss)
- Hypercatabolic states
- Sepsis
- Major trauma
- Severe burns
- Severe recurrent pancreatitis (∵ malabsorption / hypercatabolic state)
- Liver failure with hepatic encephalopathy (∵ unable to feed enterally / hypercatabolic state)
- Pre-operative nutritional build-up
- Malnourished patient undergoing major surgery
- Patient undergoing major surgery with expected post-operative NPO > 7 days
- Post-operative complications and cannot tolerate enteral feeding
Composition of nutrients in Parenteral nutrition
- Protein
- a.a: 300 mg N/kg/day
- protein:calorie ratio = 1gm N: 100-150 Kcal - Carbohydrate
- glucose 30 cal/kg/day —> ***major source of nutrition in sepsis - Fat
- long-chain triglyceride
- medium-chain triglyceride
- at most 1 gm/kg/day
Rate given: 42 ml/hour —> 1L per day
If cannot eat at all —> 2L per day
Parenteral nutrition: Routes of administration
- Peripheral vein nutrition (Superficial vein)
- low dextrose concentration
- fat emulsion
—> provides 60% of calorie
—> reduces irritating effect of a.a. on vein wall - Central vein nutrition / Total parenteral nutrition
- indication: **run out of peripheral vein / **longer duration use is anticipated
- provide ***full nutritional support
- high dextrose concentration
- administration:
—> catheter (silicone) with tip in central vein (SVC: via IJV / Subclavian or IVC: via Femoral)
—> tunneled catheter: Hickman / Broviac catheter (silicone): insertion by direct exposure of cephalic vein / EJV —> percutaneous puncture of subclavian vein (below clavicle) —> catheter tip in SVC (CXR to confirm position + exclude pneumothorax)
—> IV fluid administration set / tubing
—> bag / bottle containing nutrients
Administration of TPN
Principle:
- **Caloric source infused with **protein simultaneously to spare protein for anabolism
- Slow, regulated by infusion pump (too rapid: hyperglycaemia, electrolyte disturbance)
- 3-in-1 TPN system / 2 bags in Y connection (prone to decay if pre-mixed)
- can add additional supplement (e.g. K supplementation, trace elements)
***Complications of TPN
- Catheter-related
- Catheter sepsis
- Catheter embolism (tip of catheter broke, either during insertion / pulling out)
- Air embolism - Percutaneous puncture of subclavian vein
- Pneumothorax
- Hydrothorax
- Haemothorax - Nutrient-related
- Excessive glucose —> Ketoacidosis, ↑ CO2, Fatty liver, Suppressed phagocytic function
- Excessive fat —> Saturation of reticuloendothelial system, Fatty liver
- Excessive nitrogen —> Uraemia
Prescription of TPN
- Protein
- ***300 mgN/kg/day - Glucose / Fat
- ***30 cal/ kg/day - Vitamin (Multi)
- 5-10 ml - Trace mineral
- 10 ml - Electrolytes
- Blood test everyday
- Na, K, PO4, Mg
Enteral nutrition
Indications:
1. **Unable to swallow
2. **Functioning GI tract that can be used safely
- Burn (Airway injury / Mechanical intubation)
- Upper GI obstruction
- Chemotherapy (Mucositis, Ulcer)
- RT (Stricture, Esophagitis, Gastritis)
- Stroke
Routes of administration:
1. NG (more reflux but can be done bedside) / Nasoduodenal tube (less reflux / aspiration ∵ have pyloric sphincter but need endoscopy to help insertion)
2. Gastrostomy
3. Jejunostomy (e.g. in Gastroparesis)
Confirmation:
- Use of Radioopaque tube / marker at tip —> CXR / AXR to confirm position
Prescription of Enteral nutrition
- Intact protein, starch, medium-chain triglyceride
- ***1 cal/ml (e.g. 1500 cal/day requirement —> 1.5L)
- minimally hyperosmolar (300 Osm/kg), used in most instances - Elemental diet (for patients with loss of GI function, poor absorption)
- di/tripeptides
- oligosaccharides
- medium-chain triglyceride
- ***1 cal/ml
- hyperosmolar
- used in GI fistula, pancreatic disease
