Symposium on Complications of General Surgery

Total Parenteral Nutrition

George F. Reinhardt, M.D}' Anthony J. De Orio, M.D.,t and Mitchell V. Kaminski, Jr., M.D.!

The technique of total parenteral nutrition has frequently been referred to as "hyperalimentation." For purposes of clarity, the use of the term "hyperalimentation" will be avoided in this article and the words "total parenteral nutrition" or "TPN" will be used to designate the technique whereby an attempt is made to provide for all nutritional needs for a prolonged period of time using a nonenteric route, generally intravenous. When the intravenous route is used as the primary source of calories, amino acids, electrolytes, and minerals, while partial intestinal function allows for supplemental enteric fetldings, the intravenous component of the total nutritional program is referred to as "parenteral nutrition." The word "starvation" is commonly defined as "long-continued deprival of food."17 In the present context, the word is subdefined to describe the state of the body which exists during a negative caloric or nitrogen balance for an interval in excess of 7 days. A complete discussion of the metabolism of human starvation, the effects of the stress response, and the science of intravenous nutrition is well beyond the intended scope of this section. Many current books have been devoted to these topics, and the reader is referred to such texts for an amplification of both concepts and details in this rapidly expanding field of medical practice. 3 • 23. 28. 36. 49. 52 The very unique needs of infants and children are not included in the subsequent discussion.

THE GENERAL RESPONSE TO FASTING AND STARVATION Daily nutritional needs for healthy adults vary widely and generally reflect the individual's need for energy to maintain body temperature, carry on metabolic processes, and support physical activity. When daily ':'Assistant Professor of Surgery, Loyola University Stritch School of Medicine, Maywood, Illi· nois; Chief, General Surgery Section, Veterans Administration Hospital, Hines, Illinois t Clinical Instructor of Surgery, Loyola University Stritch School of Medicine, Maywood, Illinois; Staff Surgeon, Veterans Administration Hospital, Hines, Illinois tDirector of Medical Education and Research, Saint Mary of Nazareth Hospital Center, Chicago, Illinois

Surgical Clinics of North America- Vol. 57, No.6, December 1977

1283

1284

GEORGE

F.

REINHARDT ET AL.

Table 1. Approximate Tissue Fuel Composition of Normal Man* Kg

FUEL

Fat (adipose triglyceride) Protein (mainly muscle) Glycogen (muscle and liver)

*As modified from

15.0 6.0 0.225

CALORIES

141,000 24,000 900 165,900

Cahill. 13

energy needs are not met because of either increased energy expenditure (fever, stress, increased physical activity) or decreased energy intake (fasting, starvation), available body substrates are used as energy sources to meet the daily requirements. The total available tissue substrates (protein, carbohydrates, fat) of an average 70 kg adult male are shown in Table 1. 13 It is clear from a consideration of Table 1 that man has only two major fuel depots which enable him to survive periods of fasting beyond 24 hours. These fuel depots are fat and protein. The proteins, being essential to all vital functions of the body, are used as an energy source only at major expense to the body, as all protein consumed as energy is function lost to the body. Thus the final goal of the many metabolic adaptations the body makes during starvation is the conservation of body protein at the expense of body fatP' 46 As starvation becomes prolonged, negative caloric and nitrogen balances persist until either sufficient nutriment is provided to reverse the balances or major proportions of body proteins are lost. Should the progressively starved individual survive the ravages of unhealed wounds and loss of immunocompetence, a final endpoint is reached when approximately one-third of body protein is lost. At such a major level of protein loss respiratory musculature commonly fails, and a pneumonic death becomes imminent. Under conditions of stress (sepsis, trauma, burns, surgery), daily caloric and protein expenditures may be several times the usual basal requirements. This effectively shortens the interval of time during which life-threatening catabolic events can occur. 13 • 46

PATIENT SELECTION All ill patients have definite daily energy and nutritional needs, and with few exceptions these needs exceed those of the same individual when in good health. While body reserves may temporarily meet. these needs in the acute situation, these reserves can become rapidly depleted, leaving the patient both ill and starved. The weight of accumulated evidence must lead us to the conclusion that the ill and starving patient will have a much improved chance of recovery if the starvation component is eliminated. s , 7.15. 35. 37 Bedside recognition of the early stages of starvation is difficult

1285

TOTAL PARENTERAL NUTRITION

because of our inability to measure body protein losses and remaining protein reserves accurately. Variables in therapy such as the degree of blood volume replacement and the intermittent administration of protein-containing fluids such as albumin only compound the problem of nutritional assessment. Recent work by Blackburn, Bistrian, and others has led to a method of profiling the nutritional and metabolic status of hospitalized patients using bedside and laboratory measurements. 4 , 6, 8 In the absence of such a profile, our recent baseline criterion for the initiation of aggressive nutritional support has been a 7-day (or longer) interval of negative caloric and nitrogen balance with no imminent return of normal gastrointestinal function. This baseline time interval has been shortened only in the obviously hypermetabolic patient such as the patient suffering from major burns or multiple injuries.

ROUTES OF THERAPY Once the need for special nutritional support has been established, the physician must weigh the risks, benefits, and efficiency of three possible routes of nourishment-oral (or oral-enteric), enteric, and parenteral (Fig. 1). For those patients with a functional gastrointestinal tract, supplemental feedings with or without the addition of elemental diets may be sufficient. If an oral, esophageal, or gastric impediment to feeding exists, a nasogastric, gastric, or jejunal feeding tube may be indicated. When tube feedings are used, the risks of aspiration, metabolic abnormalities, and nonabsorption of nutrients must always be anticipated. Most of these risks can be minimized by the gradual introduction

INTRAVENOUS -

(Glucose. Amino Acid., Fal.)

\.,.......... Figure 1. Three possible routes of nourishment in man.

(R8C)ulor, Liquid Of

Elemental Diet)

, i I

/

. -t I

'I'

"'ENTERIC(Blenderized,

Liquid or Elemental Diet)

1286

GEORGE

F.

REINHARDT ET AL.

of feedings with advancement after patient tolerance is demonstrated. The use of elemental diets can be a major advantage when digestive capacity is uncertainY' 12, 32 Total parenteral nutrition is indicated in those patients who are in a negative caloric and nitrogen balance and whose gastrointestinal function is insufficient to reverse these balances over a reasonable interval of time. For the previously well nourished adult, a reasonable interval can be 7 to 11 days. For a prestarved adult, or an adult with increased energy and protein needs, the 7-to-ll day interval may be much too long, and aggressive nutritional therapy must begin before the 7th day. In some patients the adequacy of tube feedings remains doubtful after a 7 day challenge using the enteric route. Nitrogen balance studies, while helpful in this situation, are not always available. When an experienced TPN team is available the intravenous route can be safely and efficiently used as the primary route for the administration of calories, nitrogen, and electrolytes, and the oral or enteric route used to supplement the patient's water, vitamin, fat, mineral, and trace element needs. The advantages of this approach are threefold: (1) the intravenous route gives the physician more precision in determining and controlling actual caloric and nitrogen intake; (2) the risks of intravenous nutrition in the hands of an experienced team can be so low as to be less than that of oral or tube feedings of borderline adequacy; and (3) patient nutritional and metabolic reserves can be more rapidly repleted, providing a more adequate cushion of reserve should unforeseen challenges (such as surgery or infection) occur during hospitalization. The importance of an experienced TPN team cannot be overemphasized. Several studies have demonstrated catheter infection rates in excess of 15 per cent when catheter care is not provided by trained personne1. 16 , 29, 47 Metabolic problems can be both numerous and serious when therapy is undertaken by individuals unfamiliar with the many potential hazards of the TPN system. 19 , 26, 52 The TPN team has as major responsibilities the care of intravenous access routes, the maintenance of metabolic flow sheets, and the training of all personnel in contact with the patient of the special needs of the patient receiving TPN. The size of a TPN team will vary with the needs of each institution, but at minimum should consist of physician, nurse, and pharmacist. All intravenous nutritional solutions are prepared by the pharmacy using a sterile, closed technique within a laminar air-flow hood. Additives to the basic solutions other than electrolytes and vitamins are avoided, thereby eliminating the problems of inactivation of both additive and solution.

ESTABLISHING THE INTRAVENOUS ROUTE Successful TPN requires that sufficient nonprotein calories be given to exceed the patient's daily caloric expenditure. Achieving such high caloric intakes in critically-ill adults for prolonged intervals requires the use of glucose-amino acid solutions which are hyperosmo-

TOTAL PARENTERAL NUTRITION

1287

lar in relationship to blood plasma. These solutions, when administered intravenously, must be rapidly diluted to avoid the complications of phlebitis and hemolysis. Adequate dilution has been demonstrated in both the superior and inferior vena cava; using the superior vena cava reduces the risk of catheter dislodgment or infection. Access to the superior vena cava is usually obtained by subclavian venipuncture, though an upper arm cephalic vein cutdown can provide an alternate route in the patient with a tracheostomy or other potentially infected neck wound. The placement of central venous catheters using the subclavian approach is basic to the technique of TPN and has been described by many authors. IB , 22, 50 Safe subclavian 'catheter placement requires meticulous attention to details of patient preparation (including blood volume replacement and bedside positioning), use of anatomic landmarks and sterile technique, and care in the handling of needles and catheter if the numerous potential complications are to be avoided. All catheter care is done under sterile conditions with the patient in the modified Trendelenburg position (supine, head and neck- dependent, feet elevated) to minimize the risks of infection and air embolism. One modification of the subclavian insertion technique has the advantage of removing the long needle used for subclavian venipuncture from the field once catheter placement is complete (Fig. 2). This modification, designed specifically for TPN use, requires the use of a 3 inch long 14 gauge needle, a 9-inch long, 16 gauge radiopaque silicone infusion catheter, an 18 gauge tubing adapter, and a I-inch Teflon sleeve. After the infusion catheter is threaded through the needle and into the central venous system, the needle is carefully withdrawn over the catheter and from the field. An intravenous infusion with an in-line, 0.45 p, filter is then connected to the infusion catheter using an 18 gauge adapter. A small Teflon sleeve protects the catheter-adapter junction and provides a point of stability for securing adapter, catheter, and sleeve to the anterior chest wall with nonabsorbable suture (see Fig. 2). A second suture, located at the catheter exit site through the skin, is

Figure 2. Detail of subclavian catheter skin exit site.

1288

GEORGE

F.

REINHARDT ET AL.

secured to the catheter tight enough to prevent motion at the skin exit site. An iodophor antibiotic ointment is used to seal the skin exit site, after which a sterile dressing which seals the exit site, external catheter, and adapter-filter junction within the dressing is applied. Mask and gloves are used whenever this dressing requires changing. No TPN solution is infused until a chest film demonstrates the tip of the infusion catheter to be within the superior vena cava.

CARE OF THE INTRAVENOUS FEEDING CATHETER Once placed with its tip into the superior vena cava, the intravenous feeding catheter is used for no other purpose than to administer TPN . therapy. The intravascular silicone catheter is not changed for the duration of therapy unless catheter sepsis, venous thrombosis, or displacement of the intracaval catheter tip occurs. The catheter dressing and terminal filter are changed routinely every 48 hours by members of the TPN team. Nonscheduled changes are performed only by trained physicians or nursing personnel. All dressing changes require that the patient be masked and placed in the modified Trendelenburg position. Using mask and gloves, a member of the TPN team (1) removes the old dressing, (2) observes the condition of the skin at the catheter exit site, (3) cleans the skin with an organic solvent, (4) paints the exit site and adjacent chest wall with an iodophor solution, (5) applies iodophor ointment to the exit site, (6) changes the terminal filter, and (7) applies a new, sterile, sealed gauze dressing. The terminal 0.45 f.t filter serves as an air, particulate matter, and partial microbial barrier. The bottle of appropriate TPN solution is administered to the patient through an intravenous tubing which has a sterile, in-line volume measuring reservoir with an outlet tubing connecting to the 0.45 f.t filter (Fig. 3). Proper nursing attention to the flow of solution through the volume reservoir obviates the need for an infusion pump in most nursing units. Prescribed hourly flow rates must be met if the risks of hypoglycemia, hyperglycemia, and fluid overload are to be avoided. The intravenous line and volume reservoir are changed with each new bottle of TPN solution.

PRIORITIES OF THERAPY Providing an extracellular environment conducive to substrate utilization is of prime importance any time nutrients are given. In general, patient vital sign stability, hydration, and electrolyte balance are prerequisite to either the initiation or acceleration of TPN therapy. More specifically, patients in crisis situations such as those related to an inadequate airway or respiratory function, an improper blood volume (dehydration, hemorrhage, shock, congestive failure), sepsis (bacteremia or fungemia), electrolyte or mineral imbalance, or hypoglycemia have an extracellular environment which may interfere with normal cellular transport mechanisms; the therapy of these emergencies must receive

1289

TOTAL PARENTERAL NUTRITION

temporary priority over nutrient considerations until metabolic stability has been achieved. The importance of these general principles cannot be overemphasized. Following stabilization of the crisis situation, TPN may be instituted. Patients suffering from the stress of multiple trauma, burns, or infection are hypermetabolic and soon become candidates for TPN. Stress produces an endogenous hyperglycemia secondary to glycogenolysis and gluconeogenesis. During stress the patient may temporarily require exogenous supplementation of insulin in order to maintain glucose homeostasis and to avoid glucosuria. If insulin is needed to prevent hyperglycemia with glucosuria, sufficient insulin should be given. As stress abates, the insulin requirement will rapidly diminish and care must be taken to avoid hypoglycemia. Regular insulin may be added directly to the nutrient solution or given according to a sliding scale. 33

THE CHOICE OF SOLUTIONS The general indication for TPN is gastrointestinal failure, and most solutions available today are designed specifically for this problem. Pa-

TPN SOLUTION--

Figure 3. system.

Bedside TPN delivery

VOLUME RESERVOIR--·

FILTER",

....

~

c.c



Table 2. COMPOSITION PER LITER

Amino acids Dextrose Approximate carbohydrate calories Total nitrogen (gm per liter) Carbohydrate calories per gram nitrogen Electrolytes (mEq per liter) Potassium Phosphate Magnesium Sodium Chloride Acetate

Base Intravenous Nutrition Solutions SOLUTION A

SOLUTION B

500 ml Travasol 5.5 per cent" +500 ml 50 per cent dextrose monohydrate 1000 ml total volume 850 4.63 180

500 ml FreAmine II 8.5 per centt +500 ml 50 per cent dextrose monohydrate 1000 Inl total volume 850 6.25 135

30 30 5 35 35 50

(20H 10 (5)t

5 (20)t

gr

o

~

"Travasol (amino acid) injection with electrolytes, Travenol Laboratories, Inc., Deerfield, Illinois. tFreAmine II (amino acid injection), McGaw Laboratories, Irvine, California. tAs additives (20 mEq KCl and 5 mEq MgSO,).

~ ~

::0

t

Total parenteral nutrition.

Symposium on Complications of General Surgery Total Parenteral Nutrition George F. Reinhardt, M.D}' Anthony J. De Orio, M.D.,t and Mitchell V. Kamin...
2MB Sizes 0 Downloads 0 Views