Chapter 073. Enteral and Parenteral Nutrition (Part 9)

ComplicationsMechanical The insertion of a central venous catheter should be performed by trained and experienced personnel using aseptic techniques to limit the major common complications of pneumothorax and inadvertent arterial puncture or injury. Catheter position should be radiographically confirmed to be in the superior vena cava distal to the junction with the jugular or subclavian vein and not directly against the vessel wall. Thrombosis related to the catheter may occur at the site of entry into the vein and extend to encase the catheter. Catheter infection predisposes to thrombosis, as does the systemic inflammatory response. ...
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Chapter 073. Enteral and Parenteral Nutrition (Part 9) Chapter 073. Enteral and Parenteral Nutrition (Part 9) Complications Mechanical The insertion of a central venous catheter should be performed by trainedand experienced personnel using aseptic techniques to limit the major commoncomplications of pneumothorax and inadvertent arterial puncture or injury.Catheter position should be radiographically confirmed to be in the superior venacava distal to the junction with the jugular or subclavian vein and not directlyagainst the vessel wall. Thrombosis related to the catheter may occur at the site ofentry into the vein and extend to encase the catheter. Catheter infectionpredisposes to thrombosis, as does the systemic inflammatory response. Theaddition of 6000 U of heparin in the daily parenteral formula in hospitalizedpatients with temporary catheters reduces the risk of fibrin sheath formation andcatheter infection. Temporary catheters that develop a thrombus should beremoved and, based on clinical findings, treated with anticoagulants. Thrombolytictherapy can be considered for patients with permanent catheters depending on theease of replacement and presence of alternate, reasonably acceptable venousaccess sites. Low-dose warfarin therapy of 1 mg/d reduces the risk of thrombosisin permanent catheters used for home PN, but full anticoagulation may be requiredin patients who have recurrent thrombosis related to permanent catheters. A recentU.S. Food and Drug Administration mandate to reformulate parenteralmultivitamins to include vitamin K at a dose of 150 µg daily may affect theefficacy of low-dose warfarin therapy. There is a no vitamin K version availablefor patients receiving this therapy. Catheters can become mechanically occludedand may also become occluded by fibrin at the tip, or by fat, minerals, or drugsintraluminally. These occlusions can be managed with low-dose alteplase forfibrin, with indwelling 70% alcohol for fat, with 0.1 N hydrochloric acid formineral precipitates, and with either 0.1 N hydrochloric acid or 0.1 N sodiumhydroxide for drugs, depending on their pH. Metabolic The most common problems related to PN are fluid overload andhyperglycemia (Table 73-8). Hypertonic dextrose stimulates a much higher insulinlevel than meal feeding. Because insulin is a potent antinatriuretic and antidiuretichormone, hyperinsulinemia leads to sodium and fluid retention. In the absence ofgastrointestinal losses or renal dysfunction, net fluid retention is likely when totalfluid intake exceeds 2000 mL/d. Close monitoring of body weight, as well as fluidintake and output, is necessary to prevent this complication. In the absence ofsignificant renal impairment, the sodium content of the urine is likely to be As a rough estimate, the amount of insulin can be provided in a similar proportionto the amount of calories provided as TPN relative to full feeding, and the insulincan be placed in the TPN formula. Subcutaneous regular insulin can be providedto improve glucose control as assessed by measurements of blood glucose every 6h. About two-thirds of the total 24-h amount can be added to the next days order,with subcutaneous insulin supplements as needed. Advances in TPN concentrationshould be made when reasonable glucose control is established, and the insulindose adjusted proportionately to the calories added as glucose and amino acids.These are general rules, and they are conservative. Given the adverse clinicalimpact of hyperglycemia, it may be necessary to use continuous insulin therapy asa separate infusion with a standard protocol to initially establish control. Onceestablished, this insulin dose can be added to the PN formula. Acid-baseimbalance is also common during PN therapy. Amino acid formulas are buffered,but critically ill patients are prone to metabolic acidosis, often due to renal tubularimpairment. The use of sodium and potassium acetate salts in the PN formula mayaddress this problem. Bicarbonate salts should not be used because they areincompatible with TPN formulations. Nasogastric drainage produces ahypochloremic alkalosis that can be managed by attention to chloride balance.Occasionally, hydrochloric acid may be required for a more rapid response orwhen diuretic therapy limits the ability to provide substantial sodium chloride. Upto 100 meq/L and up to 150 meq of hydrochloric acid per day may be placed in afat-free PN formula.