• Calcium is the most abundant mineral in the human body and is found in dairy products, eggs, green vegetables and some fish (e.g. sardines). An adequate supply is obtained from a well-balanced diet but certain groups can require more such as teenagers and pregnant or nursing mothers. It is absorbed from the intestines and is an essential structural component of bone where we find approximately 99% of our calcium (with the other 1% found in blood). Calcium is required for vascular contraction and vasodilation, muscle function, nerve transmission, intracellular activity and hormonal secretion. It also provides rigidity in bones in the form of calcium phosphate. Calcium regulation is controlled by the action of parathyroid hormone, vitamin D and calcitonin (Geissler and Powers 2005) with less than 1% of vitamin D and calcitonin needed to support metabolic function. As it is tightly regulated, the levels in the body do not fluctuate with dietary changes; instead the body uses bone tissue as a source of calcium to maintain concentrations. A negative calcium balance occurs when net calcium absorption fails to compensate for urinary calcium losses. Signs of calcium deficiency include stunted growth, poor quality bones, teeth and bone malformation. Bone undergoes continuous remodelling with constant resorption and deposition into new bone. The balance between these two actions can change with age. For example, in a period of growth (in children and adolescents), formation exceeds absorption. In adulthood both actions are relatively equal but in the aging population, particularly post-menopausal women, bone resorption exceeds formation resulting in bone loss and an increased risk of osteoporosis. During these periods, this results in a change in the recommended daily intake. Recommended daily calcium intakes vary from country to country. The recommended daily intake for the USA and United Kingdom are shown in Tables 10.1 and 10.2.
• Phosphorus is essential for skeletal development and is found in cheese, oatmeal, liver and kidney. It is also added to foods and drinks such as cola as polyphosphates or phosphoric acid. Where there is a normal level of calcium a deficiency of phosphorus is unlikely as bone mineral consists of calcium phosphate. Along with calcium and vitamin D, it is involved in the hardening of bones.
• Iron is an essential trace element. Sources include liver, beef, lamb, soya beans, tofu, lentils, kidney beans and green leafy vegetables. The recommended daily intake varies according to sex and age e.g. for females aged 19–50 years, 18 mg daily is advised while for males of the same age 8 mg daily is advised (Office of Dietary Supplements 2007) with only a small proportion absorbed (less than 15%). Iron is essential for the formation of haemoglobin (oxygen-carrying component) in red blood cells. Iron deficiency is a condition that causes anaemia if iron stores are depleted and is the most common nutritional deficiency. Mild anaemia in many individuals is of little health consequence due to compensatory mechanisms in the body (such as increased cardiac output, diversion of blood flow and increased release of oxygen from haemoglobin), but the body cannot compensate in severe anaemia which results in poorer oxygen delivery to the tissues and impacts on body function. Work performance is limited and this will influence the participation of patients in rehabilitation post injury and after surgery. It is essential that the patient’s haemoglobin is within an acceptable range to facilitate recovery and rehabilitation.
• Zinc can be obtained from shellfish, meat and whole grains with the recommended intake being 10–12 mg daily. Reduced growth is the only clearly demonstrated consequence of mild zinc deficiency although it is thought that zinc plays a central role in turnover and metabolism of connective tissue so a deficiency may have a negative influence on bone formation (Geissler and Powers 2005).
• Sodium is found in most foods and can also be added to food. It helps regulate water content in the body. A diet high in sodium increases urinary calcium excretion. Sodium occurs as an extracellular action and is involved in muscle contraction, transmission of nerve impulses along the axons and water and electrolyte balance. The British Nutrition Foundation (2012) recommends a salt intake (sodium chloride) of no more than 6 g daily. Currently intakes of sodium are high and although some is essential, a substantial reduction in intake is required.
• Potassium is found in fruit and vegetables and other foods. As with sodium, it is also involved in muscle contraction, transmission of nerve impulses and water and electrolyte balance and occurs as an intracellular action.
• Fluoride is involved in the mineralisation of bones. Fluoride is present in the majority of foods. Adding fluoride to drinking water is controversial; low fluoride levels may be beneficial but higher levels are toxic, resulting in fluorosis leading to joint pain and spinal defects (Geissler and Powers 2005). Fluorosis is rare in the Western world but is common in parts of Africa, China and India.
• Magnesium is important in calcium homeostasis and in the metabolism and/or action of vitamin D so is essential for the synthesis and secretion of the parathyroid hormone. A deficiency results in impaired parathyroid hormone secretion, disturbed calcium homeostasis and hypocalcaemia is a common symptom of a moderate to severe deficiency (Expert Group on Vitamins and Minerals 2003).
• Aluminum toxicity occurs in chronic renal failure or in patients receiving parenteral nutrition, or when drinking or ingesting substances that are high in aluminium, or living or working in an environment that contains high levels of aluminium or is very dusty. Osteoblast function is impaired in this toxic environment and there is reduced bone remodelling and osteomalacia.
• Manganese is required for bone health. It is found in vegetables, cereals and nuts and tea provides a rich resource. A deficiency is rare.

Fibre is found in cereals, beans, pulses, fruit and vegetables and although not a nutrient, it facilitates movement in the gut and helps prevent constipation. Other dietary components can also influence bone health. Excessive alcohol consumption can affect bone quality and increase the risk of fracture. A suggested link between an increased intake of caffeine and fracture is noted in publications on bone health; however, Heaney (2002) reported in a large prospective study of caffeine intake and fracture risk that, while there was a three times greater risk of hip fracture for women consuming more than 817 mg caffeine a day (five cups of coffee), the number of hip fractures in the study were small. It is possible that this intake is not a cause of fractures but may be associated with a change in calcium intake when less milk is ingested. A high intake of carbonated beverages is also associated with a lower bone mineral density due to lifestyle and dietary factors. SIGN (2004) although supportive, report the evidence as inconclusive and do not make any recommendations in this area.

Metabolic response to tissue injury and trauma

The metabolic effect of trauma and surgery is catabolism of stored body fuels. The size and time span of this response is proportional to the injury and any complications (Desborough 2000), so energy requirements will increase depending on the demand created by the processes of recovery and healing. It is essential, therefore, that the nutritional needs of the patient are considered in the post-trauma, preoperative, peri-operative and post-operative periods. The increased demands placed upon the body during recovery from surgery, injury and associated complications can lead to malnutrition and delayed recovery and warrants careful consideration by the multidisciplinary team.

The dietary needs of children and adolescents must take into account their age, growth and development which can make them susceptible to nutritional imbalance and deficiencies. Consideration needs to be given to additional demands related to exercise, sport and training programmes. As individuals age, the risk of chronic disease increases and nutrition plays a role in the development of, susceptibility to and outcome of disease. Other groups at risk of under nutrition and malnutrition include those with learning disabilities, dementia and other mental health conditions. Lee and Kolasa (2011) identify the difficulties of providing adequate nutrition to people with advanced dementia who need assistance with feeding.

Nutrition assessment and intervention

Malnutrition refers to both under-nutrition and over-nutrition. Nutrition deprivation does not imply a lack of food, but the provision of a diet that does not meet the physiological needs of the patient (Kneale 2005). Patients are at risk of malnutrition if the intake of nutrients is affected by comorbidities, surgery or underlying problems that affect appetite or absorption of food. Malnutrition can have a wide range of consequences including impaired immune response, muscle fatigue, impaired wound healing and growth (BAPEN 2011). Patients at risk of malnutrition remain in hospital for longer than those who are well nourished and are more likely to be discharged to alternative settings rather than home. The risk of malnutrition is increased in the older person, leading to impaired coordination with an increased risk of falls. Nutritional support is essential for those who are malnourished; i.e. with a Body Mass Index (BMI) of less than 18 kg/m², unintentional weight loss of >10% in the previous 3–6 months or a BMI of <20 kg/m² and an unintentional weight loss greater than 5% within 3–6 months (NICE 2006).

Obesity is a common nutritional problem in many developed countries. It exists where there is an excess accumulation of body fat when the BMI exceeds 29.9 (Box 10.1) and associated with high morbidity and mortality rates. Obese patients may prove challenging during all phases of care due to an associated risk of complications. The role of the nurse during preparation for surgery is critical in providing support and advice with respect to achieving weight loss.

Measuring nutritional status can be predictive of health outcomes and the assessment of nutritional intake is required if there may be a need to provide advice to the person or interventions such as enteral or parenteral support. Nutritional assessment approaches include dietary assessment, the use of anthropometry (physical measurement of aspects of human body size) and the use of biochemical, functional and clinical measures or indices. Biochemical status measures are defined for each nutrient and assess the concentration of the nutrient or its derivative in body fluid. Functional indices are assessments of the metabolic processes that are nutritionally dependent. Clinical indices are the signs and symptoms of a nutritional deficiency.

Dietary assessment involves attaining a dietary history from the individual or carer for the previous 24 hours or by administering a questionnaire to determine the frequency of different food groups eaten over the previous week. Anthropometry includes the measurement of body weight and height from which the BMI is calculated (Box 10.1). The percentage of body fat can be estimated by measuring the sum of the thickness of skinfolds over the biceps, triceps, subscapular and supra-iliac sites. The fat content varies with age and gender. It is now recognised that intra-abdominal fat measurement has a greater influence on the development of heart disease and diabetes than fat measurement in subcutaneous sites and is useful in orthopaedic assessment in preparation for surgery.

Box 10.1 Body Mass Index (BMI)

Hydration and dehydration

Good hydration involves ensuring an adequate amount of water is available to body tissues. Dehydration is a depletion of water content in the tissues resulting from either loss of fluid or inadequate intake. Maintaining hydration is critical to maintaining good health especially in advancing age. Poor hydration can lead to multiple problems such as tendons and ligaments becoming less resilient, constipation, dry and itchy skin, acne, nose bleeds, repeated urinary tract infections, dry coughs, sneezing, sinus pressure, headaches and daytime fatigue. These are often as a result of build-up of toxins as excretory mechanisms fail to function properly. Dehydration can also weaken the body’s immune system and leads to chemical, nutritional and pH imbalances. Insufficient hydration fatigues muscles, reduces coordination and causes muscle cramps, restricting the patient’s ability to maintain physical function and mobility.

Water is essential for life. It makes up about 55–60% of body weight with adequate fluid intake essential for healthy organ function. Water is lost during respiration (about 300–400 ml per day) and urination (1–2 L per day with a general rule of thumb of 1 ml/kg/hr with boundaries of 0.5 ml–2 ml/kg/hr). Water is also lost through the skin by evaporation (600 ml per day) and faeces (100–200 ml per day). This loss depends on age, body size, physical activity, health and environmental conditions and is normally balanced by the intake of food and water. Water has many functions, the moistening of food for swallowing, regulation of body temperature, transport of substances around the body, a medium for excretion of waste products, dilution of water products in the body; provision of a moist environment required by cells and the facilitation of metabolic reactions.

The recommended fluid intake is 1.2 litres per day for adults (British Nutrition Foundation 2012). For children, the recommended fluid intake varies with age (NICE 2010) (Table 10.4).

Fluid and electrolyte balance can be affected by the physiological response to the stress of surgery or injury, with glucocortoid secretion increasing reabsorption of sodium and water in the kidneys with a corresponding loss of potassium and hydrogen ions. Increased levels of antidiuretic hormone also increase water reabsorption while high aldosterone levels further increase sodium reabsorption in order to maintain circulating volumes and renal perfusion. As a result of trauma to the tissue from injury or surgery, intracellular potassium is released, resulting in an exchange for retained sodium. Levels of potassium need careful monitoring and should be replaced as appropriate (Alexander et al., 2006).

Nausea and vomiting

Post operative nausea and vomiting (PONV) is a common unpleasant experience, with patients at risk of aspiration, electrolyte imbalance, pain, increased length of stay and significant discomfort. Risk factors identified for PONV include obesity, older age, female gender, children, prior history, anxiety, inadequate pain relief, prolonged fasting and post-operative hypotension. Simple measures such as hydration, supplemental oxygen and sitting the patient upright can be effective along with the appropriate use of anti-emetics.

Starvation/fasting

Periods of fasting or starvation related to trauma and surgery can be as a result of ill health, fasting prior to and after surgery and loss of appetite associated with trauma, surgery or ill health. Although metabolic adaptation can sustain the normal energy requirements of the body for approximately 10 hours during starvation, minimising the length of fasting periods is essential in promoting good nutrition and recovery. In the past, surgical patients were fasted routinely from food and drink for long periods of up to 12 hours before anaesthesia to reduce the risk of aspiration and pneumonitis. Despite evidence (Brady et al., 2003, Brady et al., 2009) that shorter pre-operative fasting does not increase the risk of this complication, practice continues to vary. Long fasting times for surgery can impact on hydration and nutrition, therefore surgery should be planned to ensure fasting/starvation times can be kept to a minimum and intravenous hydration implemented.

Preoperative fasting is often in excess of the recommended 2 hours for fluids and 6 hours for milk or food. The ‘2–6’ rule applies to adults; water can be drunk up to two hours before induction of anaesthesia along with a minimum preoperative fasting time of six hours for food (solids, milk and milk-containing drinks). The volume of administered fluid does not appear to have an impact on patients’ residual gastric volume and gastric pH when compared to a standard fasting regime. It is suggested that the anaesthetic team should consider further interventions for patients at the highest risk of regurgitation and aspiration. For children, the 2-4-6 rule applies. The intake of water or other clear fluid should cease two hours before induction of anaesthesia with breast feeding ceasing four hours and formula milk, cow’s milk or other solids ceasing six hours before anaesthesia (RCN 2005). See Box 10.2 for further discussion of the evidence.

Box 10.2 Evidence digest. Reproduced with permission from The Cochrane Collaboration

Minimising the length of fasting times combined with appropriate fluid management during surgery is a key factor in improving patient and surgical outcomes after major surgery. Oesophageal Doppler guided fluid management is a minimally invasive procedure that can enable the anaesthetist to accurately administer IV fluids during surgery and reduce post-operative complications (Callow 2010). Post-operatively, patients should be encouraged to drink as soon as they are ready providing there are no contra-indications (RCN 2005). Intravenous fluid replacement should be administered as prescribed and discontinued when the patient is drinking adequate fluids.

Many serious fluid balance problems can be averted by keeping careful assessment of the intake and output of the patient and maintaining good records (Methany 2000) so that appropriate and timely action can be taken. Accurate fluid balance recording allows the practitioner to monitor intake and output and calculate the balance or discrepancy. Accuracy in both measurement and documentation is fundamental to patient care and outcomes, but this is often neglected, is inaccurate and does not give a clear account of the patient’s input and output.

Summary

Good nutrition and hydration play a key role in the patient’s recovery. By ensuring that consideration is given to nutrition and hydration in conjunction with other aspects of care, good patient outcomes can be achieved while reducing delays in the patient returning to their previous level of independence.

Recommended further reading

1. Council of Europe (2003) Food and Nutritional Care in Hospitals. Available at: https://wcd.coe.int/ViewDoc.jsp?id=85747 (accessed 29 October 2013).
2. Desborough, J.P. (2000) The stress response to surgery and trauma. British Journal of Anaesthesiology, 85(1), 109–117.
3. Hilton, A.K., Pellegrino, V.A. and Scheinkestel, C.D. (2008) Avoiding common problems associated with intravenous fluid therapy. The Medical Journal of Australia, 189, 509–513.

References

1. Alexander, M., Fawcett, J. and Runciman, P.J. (2006) Nursing Practice: Hospital and Home, 3rd edn. Churchill Livingstone Elsevier, Edinburgh.
2. BAPEN (2011) The MUST Explanatory Booklet (Online). Available at: http://www.bapen.org.uk (accessed 12 October 2012).
3. Brady, M.C., Kinn, S., Stuart, P. and Ness, V. (2003) Preoperative Fasting for Adults to Prevent Perioperative Complications. Cochrane Database of Systematic Reviews 4 (Art. No.: CD004423). DOI: 10.1002/14651858.CD004423.
4. Brady, M.C., Kinn, S., Ness, V. et al. (2009) Preoperative fasting for preventing perioperative complications in children. Cochrane Database of Systematic Reviews 4 (Art. No.: CD005285). DOI: 10.1002/14651858.CD005285.pub2.
5. British Nutrition Foundation (2012) (Online). Available at: http://www.nutrtion.org.uk (accessed 6 November 2012).
6. Callow C. (2010) Doppler monitoring reduces hospital stay, The Clinical Services Journal, (March), 41–43.
7. Council of Europe (2003) Food and Nutritional Care in Hospitals. Available at: https://wcd.coe.int/ViewDoc.jsp?id=85747 (accessed 29 October 2013).
8. Department of Health (DoH) (2010) Essence of Care: Benchmarks for Food and Drink. The Stationery Office, Norwich.
9. Desborough, J.P. (2000) The stress response to surgery and trauma. British Journal of Anaesthesiology, 85(1), 109–117.
10. Expert Group on Vitamins and Minerals (2003) Safe Upper Limits for Vitamins and Minerals. Food Standards Agency, London.
11. Geissler, C. and Powers, H. (2005) Human Nutrition, 11th edn. Elsevier Churchill Livingstone, Edinburgh.
12. Heaney, R.P. (2002) Effects of caffeine on bone and the calcium economy. Food and Chemical Technology, 40(9), 1263–1270.
13. Kneale, J. (2005) The importance of nutrition, in Orthopaedic and Trauma Nursing, 2nd edn (eds J. Kneale and P. Davis). Elsevier Churchhill Livingstone, Edinburgh, pp.164–179.
14. Lee, T.J. and Kolassa, K. (2011) Feeding the person with late stage Alzheimers Disease. Nutrition Today, 46(2), 75–79.
15. Methany, N. (2000) Fluid and Electrolyte Balance: Nursing Considerations, 4th edn. Lippincott, Philadelphia.
16. National Institute for Health and Clinical Excellence (NICE) (2006) Nutrition Support in Adults CG32. NICE, London.
17. National Institute for Health and Clinical Excellence (NICE) (2010) Nocturnal Enuresis and Bedwetting in Children and Young People CG111. NICE, London.
18. Office of Dietary Supplements (2007) Iron Factsheet. Available at: http://ods.od.nih.gov/factsheets/IronHealthProfessional/ (accessed 31 October 2013).
19. Office of Dietary Supplements (2012) Calcium Factsheet. Available at: http://ods.od.nih.gov/factsheets/CalciumHealthProfessional/ (accessed 4 November 2012).
20. Palmer, C.A., Burnett, D.J. and Dean, B. (2010) Its more than just candy: important relationship between nutrition and oral health. Nutrition Today, 45(4), 154–156.
21. Royal College of Nursing (RCN) (2005) Perioperative Fasting in Adults and Children. RCN, London.
22. SIGN (2004) Managing Osteoporosis, Guidelines 71. Available at: www.sign.ac.uk (accessed 4 November 2012).