Page 529 - ACCCN's Critical Care Nursing

19 Gastrointestinal, Liver and

Nutritional Alterations

Andrea Marshall
Teresa Williams
Christopher Gordon

INTRODUCTION
Learning objectives
During episodes of critical illness, patients often experi-
ence disturbance in their metabolic and/or endocrine
After reading this chapter, you should be able to: function. The gastrointestinal system and the associated
● describe the changes in normal gastrointestinal physiology splanchnic circulation may be compromised without
and metabolism associated with critical illness overt signs being evident. This alteration in regional
● integrate theoretical knowledge of the nutritional blood flow and tissue oxygen delivery can compromise
requirements, assessment of and potential for malnutrition normal metabolic and endocrine function. In this chapter
in the critically ill with clinical practice and rationalise the effect of gastrointestinal physiology on critical illness
selected nutritional support strategies for specific patients is provided. Second, nutritional requirements and support
● identify patients at risk for the development of stress ulcers strategies for critically ill patients are described. Third,
and rationalise therapeutic interventions for their complications associated with the stress, including the
prevention development of stress-related mucosal diseases, are dis-
● discuss the effects of critical illness on hepatic function and cussed. Fourth, assessment and management of liver
evaluate the consequences of liver dysfunction dysfunction, including liver transplantation, is reviewed.
● describe the treatment of liver failure, including liver Finally, hyperglycaemia in critical illness, the role of gly-
support therapies and transplantation caemic control and the assessment and management of
● critically analyse the role of glycaemic control in the context diabetic ketoacidosis is addressed.
of critical illness
● describe the physiological changes that occur during GASTROINTENSTINAL PHYSIOLOGY
diabetic ketoacidosis and rationalise assessment and
treatment strategies. Digestion and absorption of nutrients such as carbohy-
drates, amino acids, minerals and water are key functions
of the gastrointestinal system. Digestive enzymes are
responsible for breaking down food into smaller sub-
stances that can be absorbed by the gastrointestinal tract.
While some digestion begins in the oral cavity (for
Key words example, the breakdown of starch into sugar by salivary
amylase), the stomach, pancreas, and small intestine
secrete the most enzymes responsible for digestion (Table
anabolism 19.1). The small bowel plays an important part in the
catabolism digestion and absorption of these nutrients, where the
hypermetabolism processes of diffusion, facilitated diffusion, osmosis and
enteral nutrition active transport are responsible for absorption of 90%
total parenteral nutrition of all nutrients. The remaining 10% of nutrients are
1
glycaemic control absorbed in the large intestine.
diabetic ketoacidosis The secretion of enzymes and absorption of these small
liver failure molecules produced during digestion is an energy-
hepatic encephalopathy consuming process that can be negatively influenced by
hepatorenal syndrome gastrointestinal hypoperfusion and the failure of the gas-
extracorporeal liver support trointestinal tract to receive sufficient oxygen and nutri-
506 tients required for cellular function.