Lecture 10b 21 March 2011 Parenteral Feeding

Nutrients go directly into blood stream bypassing gastrointestinal tract Used when a patient cannot, due to physical or psychological impairment, consume sufficient nutrients enterally Used when patients gi system will not adequately process food for body Actual infusion depends on site of infusion and patient’s fluid and nutrient requirements Usual fluid volume is L over a 24 hour period Solutions are fairly limited in variety due to standard concentrations of protein, carbohydrate, and fat in standard volumes. Thus individualisation of parenteral formulas is rather limited

Parenteral Feeding Usual fluid volume is L over a 24 hour period Solutions are fairly limited in variety due to standard concentrations of protein, carbohydrate, and fat in standard volumes. Thus individualisation of parenteral formulas is rather limited

Parenteral Feeding Composition Dextrose Amino acids Lipid emulsion Sterile water Electrolytes Vitamins

Carbohydrate Dextrose- provides 3.4 kcal/g and not 4 kcal/g -difference is due to what? Concentration is 10 % (peripheral introduction) to 25 % (total parenteral nutrition) Restricted in ventilator patients because oxidation of glucose produces more carbon dioxide than does oxidation of fat

Protein Mixture of essential and non-essential amino acids Concentration 5-15 % of solution Quantity of amino acids depends on patients estimated requirements and hepatic and renal function-why?

Lipid emulsions Safflower and soybean oil with egg lecithin used as an emulsifier (why the emulsifier and how does it work?) Isotonic Significant source of calories

Lipid emulsions Available in 10 and 20 % concentrations supplying 0.9 and 1.8 kcal/ml respectively Math Usual dose is 0.5 to 1 g/kg/day to supply 30 % of total kcal requirement IV fat contradicted for severe hepatic pathology, hyperlipidemia or severe egg allergies Used cautiously with atherosclerosis, blood coagulation disorders

Electrolytes Dictated by patients blood chemistry values and physical assessment findings Can be changed every 8 hours (3 x/day) to compensate for lab values However there is a degree of risk in this (what risk?)-contamination If 24 hour bag of total parenteral nutrition (TPN) this type of adjustment is more difficult

Standard multivitamin preparation may be added to TPN solution Minerals- exact requirements have not been worked out for many of the minerals for TPN

Types of Parenteral Nutrition Peripheral parenteral nutrition (PPN) Total parenteral nutrition (TPN) Basic difference between the two is the concentration of nutrients infused

PPN -must be isotonic and therefore low in dextrose and amino acids to prevent phlebitis and increased risk of thrombus formation The need to maintain isotonic solutions of dextrose and amino acids while avoiding fluid overload limits the caloric and nutritional value of PPN

PPN delivers complete but limited nutrition the final concentration cannot exceed 10 % dextrose and 5 % amino acids vitamins and minerals are added lipid emulsion may be added to supplement calories depending on the patients tolerance

PPN -provides temporary nutritional support -short term days and do not require more than 2000 to 2500 kcal per day

PPN -may be used for a post surgical ileus or anastomotic leak or for patients who require nutritional support but are unable to use TPN because of limited accessibility to a central vein -sometimes used to supplement an oral diet or tube feeding or transition from TPN to enteral intake

TPN Hypertonic solutions provide more dextrose and/or protein but they must be delivered centrally in a large diameter vein so that they can be quickly diluted

TPN TPN is used when nutritional requirements are high and anticipated need is relatively long 3 litres of 10 % dextrose provides only 1020 kcal -calculation

TPN -catheter to superior vena cava -typically 3 L of solution daily with a final concentration of 25 % dextrose and 3.5 % amino acids -additional 250 ml of 20 % lipid is ordered -used if enteral intake (enteral includes tube and oral in my view) will not work eg-due to impairment of gi function

TPN Indications severe malnutrition GI abnormalities : due to obstruction, peritonitis, severe acute pancreatitis after surgery or trauma especially that involving extensive burns, sepsis need for supplementation of inadequate oral uptake in patients who are being treated aggressively for cancer bone marrow transplantation

TPN cyclic -constant infusion for 8-12 hours -used for home patients -used to support inadequate oral intake -allows insulin and glucose to drop when infusion is not taking place -switch from continuous TPN to cyclic TPN should be gradually decreased by several hours per day and signs of glucose overload and fluid imbalance should be monitored