Complications Linked to Enteral or Parenteral Feeding

7. Complications Linked to Enteral or Parenteral Feeding

Thrombophlebitis

Hyperosmolar solutions increase the risk of thrombophlebitis. For peripheral vessels, it is recommended that solutions not exceed 600 to 750 mOsmol/L (Chan et al., 2002; Chandler et al., 2000a). The rate at which milliosmoles (mOsmol) are administered clinically appears to be as crucial as the osmolarity of the solution. Therefore, a 650 mOsmol solution should not be administered at twice the maintenance rate for the purpose of increasing the amount of calories delivered to the patient per unit of time. This limitation results in the need to use parenteral solutions containing high lipid emulsion concentrations with a high energy to milliosmole ratio, or to provide only a portion of the patient's energy requirement. One author reports that using polyurethane catheters in previously unused vessels for the administration of peripheral parenteral solutions when administrating peripheral parenteral nutrition (PPN) is well tolerated (Chan et al., 2002).

Septicemia

Parenteral nutrition solutions represent an ideal culture environment for bacteria. To minimize the infection risk these solutions should be prepared and administered in completely aseptic conditions.

Once it is in place the catheter and the tube must be protected from any risk of contamination by using a dedicated catheter. Medication must not be administered through the dedicated catheter nor should blood be drawn from the dedicated catheter.

Once it is in position, the catheter and the intravenous tubing must be protected from any risk of contamination. (© UCD VMTH ICU Service).

Hyperglycemia

There is a growing body of evidence in the human literature that blood glucose clamping with exogenous insulin of ICU patients may decrease mortality rates. This is due to a reduction in multiple-organ failure secondary to sepsis (van den Berghe, 2002).

The effect appears to be due to the maintenance of euglycemia rather than the beneficial effect of insulin itself, since in humans increased insulin administration is positively associated with death (Finney et al., 2003). Hyperglycemia has long been known to decrease immune function due to adverse effects on polymorphonuclear leukocyte phagocytosis as well as impaired chemotaxis, phagocytosis and intracellular killing as seen in diabetic subjects (Watters, 2001). This may, in part explain the lower incidence of sepsis in patients receiving 50% of their RER from PPN in a review by Chan (2002) compared to the frequency reported in two retrospective TPN studies by Reuter et al., (1998) and Lippert et al., (1993). Although patient selection probably plays a key role in the likelihood of developing septicemia, it is possible that the lower incidence of hyperglycemia associated with the use of PPN was also important.

Villous Atrophy and Bacterial Translocation

The enterocytes rely heavily on nutrients derived from the gut lumen as energy sources (Ziegler & Young, 1997). Thus, available energy for enterocytes is diminished with the use of parenteral nutrition. This reduction results in decreased enterocyte health and villous atrophy, and in turn increased intestinal permeability.

The loss of intestinal integrity can increase the risk of gut flora entering the bloodstream; referred to as bacterial translocation (Steinberg, 2003). There is debate as to when and if this breakdown occurs, but in humans it usually occurs after a prolonged period of parenteral nutritional support and may not be as significant as rodent models would indicate (Alpers, 2002).

There is also controversy regarding the best method of preventing villous atrophy and bacterial translocation. While some human and animal studies suggest that infusing glutamine as an energy substrate to prevent villous atrophy and bacterial translocation has some benefit, other studies have not proven this to be an effective intervention (Buchman, 1999; Marks et al., 1999). In addition, possible contraindications exist, such as liver disease - especially hepatic encephalopathy, and possibly renal disease.

Adynamic Ileus

Adynamic ileus is a common sequela of anorexia, especially in patients supported with parenteral nutritional support. Enteral feeding may decrease this risk as hormonal and neurologic signals are restored by the presence of nutrients in the gut lumen. Adynamic ileus does not always occur, and in many patients normal peristaltic reflexes continue with high pressures being generated during fasted states (Heddle et al., 1993). This point has implications for patients that have undergone intestinal surgery.

The convention of resting the bowel to prevent leakage through enterostomy sites may be flawed. There is evidence that early enteral feeding following major abdominal surgery may be preferable to parenteral support (Braga et al., 1998 & 2002).

Conclusion

• Nutritional support is indicated in canine patients with prolonged anorexia, recent body weight loss unrelated to hydration status, poor body condition and hypoalbuminemia not due to correctable losses.
• Nutritional support can enhance immune function, wound repair, response to therapy, recovery time, and survival.
• Selection of the route and diet for nutritional support should be based on patient tolerance and prevention of adverse side effects.
• Administration of single macronutrients may not be adequate to meet the patient's energy and nutrient requirements and may provide only a limited protein-sparing effect.
• The administration rate of nutritional support should provide the patient's resting energy requirement without increasing the likelihood of volume intolerance or metabolic complications like hyperglycemia, hyperlipidemia and the refeeding syndrome.
• Monitoring of patients on nutritional support should be aimed at preventing adverse complications and to ensure successful management.