Basic science II. Perioperative management 11 12 nutrition TPN Refeeding syndrome

  1. NRI?
    15 * albumin in gm/dl + 41 * (weight / Ideal wt)
  2. What are the indications of nutritional support in a surgical patient.  [TU 2072/6] 

    Short note on Parenteral nutrition?
    Definition of TPN - 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.
    •  Small bowel ileus
    •  High output fistula >500 mls/day
    •  Mechanical small bowel obstruction
    •  Bowel infarction/bowel ischemia
    •  Inability to tolerate enteral feeding
  3. Composition of TPN -
    • Dextrose - 60-70% 
    • Amino acids - 10-20% 
    • Lipids – 10-20%
    • Electrolytes - Na, K, Ca, PO4, Mg, Cl, Acetate
    • Vitamins - Vitamine B-12
    • Minerals - Zinc, copper, manganese, selenium, chromium
    • Total Calorie - 25-35 kCal/kg/day
  4. Types of TPN?
    • Low concentration // High concentration
    •  < 10% dextrose, Amino Acids // > 10% dextrose, Amino
    •  A.k.a. Peripheral solutions // A.k.a. Central Venous solutions
    •  Usually through 18 gauge angiocath // Through PICC, CVC site only
  5. Route of delivery of TPN?
    • 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 manoeuvred into the central venous system (peripherally inserted central venous catheter (PICC) line) or by using a conventional short cannula in the wrist veins.
    • Central - catheter can be inserted via the subclavian or internal or external jugular vein. Whichever technique is employed, a post-insertion chest x-ray is essential before feeding is commenced to confirm the absence of pneumothorax and that the catheter tip lies in the distal superior vena cava to minimise the risk of central venous or cardiac thrombosis.
  6. Discuss complications of TPN. [TU 2069,72/3] 

    Complications of TPN?
    •  Related to nutrient deficiency
    • Hypoglycaemia/hypocalcaemia/ hypophosphataemia/hypomagnesaemia (refeeding syndrome)
    • Chronic deficiency syndromes (essential fatty acids, zinc, mineral and trace elements)

    •  Related to overfeeding
    • Excess glucose: hyperglycaemia, hyperosmolar dehydration, hepatic steatosis, hypercapnia, increased sympathetic activity, fluid retention, electrolyte abnormalities
    • Excess fat: hypercholesterolaemia and formation of lipoprotein X, hypertriglyceridaemia, hypersensitivity reactions
    • Excess amino acids: hyperchloraemic metabolic acidosis, hypercalcaemia, aminoacidaemia, uraemia

    •  Related to sepsis
    • Catheter-related sepsis
    • Possible increased predisposition to systemic sepsis

    •  Related to line
    • On insertion: pneumothorax, damage to adjacent artery, air embolism, thoracic duct damage, cardiac perforation or tamponade, pleural effusion, hydromediastinum
    • Long-term use: occlusion, venous thrombosis
  7. Contraindications of TPN?
    • Cardiac failure 
    • Blood dyscriasis 
    • Altered fat metabolism
  8. TPN administration practice guidelines?
    •  Always infuse TPN with an infusion pump
    •  Change TPN tubing every 24 hours (daily at 1400)
    •  Monitor for signs & symptoms of complications
  9. What is refeeding syndrome? [TU 2070]
    • 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.
  10. Pathophysiology of refeeding syndrome?
    • During fasting the body switches its main fuel source from carbohydrates to fatty acids or amino acids as the main energy source. The spleen decreases its rate of red blood cell breakdown thus conserving red blood cells. Many intracellular minerals become severely depleted during this period, although serum levels remain normal. Importantly, insulin secretion is suppressed in this fasted state and glucagon secretion is increased.
    • During refeeding, insulin secretion resumes in response to increased blood sugar, resulting in increased glycogen, fat and protein synthesis. This process requires phosphates, magnesium and potassium which are already depleted and the stores rapidly become used up. Formation of phosphorylated carbohydrate compounds in the liver and skeletal muscle depletes intracellular ATP and 2,3-diphosphoglycerate in red blood cells, leading to cellular dysfunction and inadequate oxygen delivery to the body's organs. Refeeding increases the basal metabolic rate. Intracellular movement of electrolytes occurs along with a fall in the serum electrolytes, including phosphorus and magnesium. Levels of serum glucose may rise and the B1 vitamin thiamine may fall. Cardiac arrhythmias are the most common cause of death from refeeding syndrome, with other significant risks including confusion, coma and convulsions and cardiac failure
  11. Treatment of refeeding syndrome?
    Refeeding syndrome can be fatal if not recognized and treated properly. An awareness of the condition and a high index of suspicion are required in order to make the diagnosis.

    The electrolyte disturbances of the refeeding syndrome can occur within the first few days of refeeding. Close monitoring of blood biochemistry is therefore necessary in the early refeeding period. In critically ill patients admitted to an Intensive Care Unit, if phosphate drops to below 0.65 mmol from a previously normal level within three days of starting enteral or parenteral nutrition, caloric intake should be reduced to 480 kcals per day for at least two days whilst electrolytes are replaced. Prescribing thiamine, vitamin B complex (strong) and a multivitamin and mineral preparation is recommended.
  12. Short note on Fast-tract surgery. [TU 2072] 

    ERAS colorectal surgery?
    Enhanced Recovery After Surgery (ERAS) is a comprehensive evidence- based consensus review of perioperative care for colonic surgery.

    1 Preadmission information, education and counseling - Patients should routinely receive dedicated preoperative counseling.

    2 Preoperative optimization - increase exercise, stop smoking and alcohol at least 4 weeks before surgery,

    3 Preoperative bowel preparation - MBP should not be used routinely in colonic surgery.

    4 Preoperative fasting and carbohydrate treatment - Clear fluids should be allowed up to 2 h and solids up to 6 hrs prior to induction of anaesthesia.

    5 Preanaesthetic medication - Patients should not routinely receive long- or short acting sedative medication before surgery because it delays immediate postoperative recovery.

    6 Prophylaxis against thromboembolism - Patients should wear well-fitting compression stockings, have intermittent pneumatic compression, and receive pharmacological prophylaxis with LMWH.

    7 Antimicrobial prophylaxis and skin preparation - Routine prophylaxis using intravenous antibiotics should be given 30–60 min before initiating surgery. Additional doses should be given during prolonged operations according to half life of the drug used. Hair clipping is associated with fewer surgical-site infections than shaving with razors if hair removal is necessary before surgery.

    8 Standard anaesthetic protocol - A standard anaesthetic protocol allowing rapid awakening should be given.

    8 PONV - A multimodal approach to PONV prophylaxis should be adopted in all patients with >2 risk factors undergoing major colorectal surgery. If PONV is present, treatment should be given using a multimodal approach.

    9 Laparoscopy and modifications of surgical access - Laparoscopic surgery for colonic resections is recommended if the expertise is available.

    10 Nasogastric intubation - Postoperative nasogastric tubes should not be used routinely. Nasogastric tubes inserted during surgery should be removed before reversal of anaesthesia.

    11 Preventing intraoperative hypothermia - Intraoperative maintenance of normothermia with a suitable warming device and warmed intravenous fluids should be used routinely to keep body temperature >36 C.

    • 12 Perioperative fluid management -
    • • Patients should receive intraoperative fluids (colloids and crystalloids) guided by flow measurements to optimise cardiac output.
    • • Vasopressors should be considered for intra- and postoperative management of epidural-induced hypotension provided the patient is normovolaemic

    13 Drainage of peritoneal cavity after colonic anastomosis - Routine drainage is discouraged because it is an unsupported intervention that is likely to impair mobilisation.

    14 Urinary drainage - Routine transurethral bladder drainage for 1–2 days is recommended.

    • 15 Prevention of postoperative ileus –
    • • Mid-thoracic epidural analgesia and laparoscopic surgery should be utilised in colonic surgery if possible.
    • • Fluid overload and nasogastric decompression should be avoided

    • 16 Postoperative analgesia
    • • Open surgery: Thoracic Epidural anesthesia (TEA) using low-dose local anaesthetic and opioids
    • • Laparoscopic surgery: an alternative to TEA is a carefully administered spinal analgesia with a lowdose, long-acting opioid

    • 17 Perioperative nutritional care
    • • Patients should be screened for nutritional status and if at risk of under nutrition given active nutritional support
    • • Perioperative fasting should be minimised.
    • • Postoperatively patients should be encouraged to take normal food as soon as lucid after surgery.

    18 Postoperative glucose control - Hyperglycaemia is a risk factor for complications and should therefore be avoided

    19 Early mobilization - Prolonged immobilisation increases the risk of pneumonia, insulin resistance and muscle weakness. Patients should therefore be mobilised.
  13. Damage control surgery. [TU 2072/6]
    It is the form of surgery that puts more emphasis on preventing the triad of death rather than correcting the anatomy. 

    • When to institute DCS - Any one of the following 
    • - pH less then or equal to 7.2
    • - serum bicarbonate level less than or equal to 15 mEq/L
    • - core temperature less than or equal to 34⁰C
    • - transfusion volume of packed RBCs more than or equal to 4000 ml
    • - total blood replacement more than or equal to 5000 ml
    • - total fluid replacement more than or equal to 12000 ml

    Stages of damage control surgery in abdomen

    • A. Stage I - 
    • • initial laparotomy
    • • identify the main source of bleeding
    • • perihepatic packing (superior and inferior) • small gastotomies and enterotomies can be rapidly closed
    • • resect non-viable bowel and close the ends
    • • minor pancreatic injuries not involving duct- no treatment
    • • distal injury including the panceratic duct- distal pancreatectomy
    • • No pancreaticoduodenectomy (drainage)
    • • abdominal closure is rapid and temporary- if there is any doubt about abdominal compartment syndrome, left it open (silo- bag, vacuum-pack technique, towel clip)

    • B. Stage II
    • • Begins in ICU
    • • The next 24 to 48 hours are crucial
    • • Correction of metabolic disorder
    • • Core rewarming
    • • Correction of coagulopathy
    • • Complete ventilatory support
    • • Correction of acidosis
    • • Identification of occult injury

    C. Stage III - Planned reoperation 

    • Indications of definitive surgery
    • 1. Core temperature 36°C or above
    • 2. Correction of acid base balance
    • 3. Normalization of coagulation profile.
  14. Discuss the pathophysiology of body’s response to infection. 56
    Preoperative managemanet of diabetic patient under going major surgery 62
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Basic science II. Perioperative management 11 12 nutrition TPN Refeeding syndrome