Surgical Treatment for Obesity

To facilitate weight loss surgically, many different types of bariatric procedure methods have been developed and established (National Institutes of Health 2009) which fall into three main categories:

• restrictive procedures that lead to physical reduction, fixed or adjustable in the size of the upper gastrointestinal tract
  
• malabsorptive procedures that bypass a proportion of the intestine with less physical restriction of food intake
  
• a combination of the restrictive and malabsorptive, which combines restriction of the upper food pathway with intestinal bypass.

There are four major surgical treatments (Burke et al. 2005) that are used after patient selection, assessment, and evaluation to identify and optimally treat medical co-morbidities that may affect perioperative risks and long-term outcomes:

• laparoscopic adjustable gastric banding
  
• laparoscopic sleeve gastrectomy
  
• laparoscopic gastric bypass
  
• laparoscopic duodenal switch.

Patients who are considered to carry too high a risk for surgery can have a less ­invasive procedure such as placement of an intra-gastric balloon in order to facilitate short-term weight loss, which in turn will mean less dependency on medication and an improvement in the overall wellbeing of the patient, achieving the NICE guidance for bariatric surgery for long-term weight loss.

Anaesthetic Classification

The classification system adopted by the American Society of Anesthesiologists (ASA) for assessing preoperative physical status used to achieve optimal general anaesthetic outcomes is shown in Box 29.1.

As many bariatric patients fall under risk levels 3 and 4, careful selection according to NICE (2006) guidance will ensure risk stratification enabling pre-optimisation prior to surgery. ASA risk classification is also influenced by a person’s weight.

Risks Associated with Obesity

Respiratory system

Obstructive sleep apnoea

Redundant fat deposit in the pharynx results in decreased patency and can cause inter­mittent obstruction of the air passage. Preoperative history with evidence of characteristic increasing snoring with subsequent apnoea and daytime somnolence may be due to ­obstructive sleep apnoea. All patients undergoing obesity surgery should be suspected of this condition as it can go unrecognised and untreated (Adams and Murphy 2000). To confirm obstructive sleep apnoea, formal sleep studies (polysomnogaphy) can be performed.

Preoperative evaluation must include airway assessment as there is a higher ­incidence of difficult airway management in these patients due to restricted jaw mobility and mouth opening, short neck and limitation of cervical spine and atlanto-occipital flexion and extension brought about by the fatty deposits (Adams and Murphy 2000).

Cardiovascular system

Obesity may affect the heart through its influence on known risk factors such as: hypertension, ischaemic heart disease (IHD), cardiomyopathies, cardiac failure, arrhythmias and dyslipidaemias (high cholesterol). Venous insufficiency and peripheral vascular disease due to increased atherosclerotic processes may also be present (AAGBI 2007).

Obesity also increases the risk of diabetes by diminishing glucose tolerance as the abnormalities in lipid and glucose metabolism appear to be related to fat distribution and total body weight (Adams and Murphy 2000).

Anthropometric evaluation covering blood pressure, waist circumference, weight and height are essential (AAGBI 2007). Laboratory tests include fasting lipid profile, fasting insulin and glucose, haemoglobin A1C, liver profile and thyroid-stimulating hormone evaluation (AAGBI 2007).

Signs of increased jugular venous pressure, added heart sounds, pulmonary crackles, hepatomegaly and peripheral oedema may be difficult to detect due to the large adipose layer of tissue hence, pre-assessment is critical in establishing IHD by performing ­electrocardiogram and echocardiogram (AAGBI 2007).

Gastro-oesophageal reflux disease

This group of patients may get gastro-oesophageal reflux due to the acid escaping into the oesophagus through a weak or overloaded valve at the top of the stomach. Also, hiatus hernia is more common in this group (National Institutes of Health 2009). These patients have increased intra-abdominal pressure, which displaces the lower oesophageal sphincter and increases the gastro-oesophageal gradient. There is also an ­association with obesity and vagal nerve function abnormalities causing higher output of bile and pancreatic enzymes, which makes the refluxed stomach acids more toxic to the ­oesophageal lining (Adams and Murphy 2000).

History of heartburn and difficulty in sleeping flat due to regurgitation may provide some indication of reflux. Non-invasive or conservative treatment is to reduce acid in the stomach using proton pump inhibitors (PPI) which work on stopping the ­proteolytic enzyme pepsin necessary for hydrochloric acid secretion. Surgical treatment for obesity has proved to be a better intervention for gastro-oesophageal reflux disease (Adams and Murphy 2000).

Communication

Professional and welcoming attitudes will help in maintaining a calm patient. Besides the physical, psychological effects and social burdens of obesity being debilitating, it can lead to a very vulnerable stage and careless comments or remarks can be very ­hurtful. Having surgery performed in a specialist unit where the medical and nursing staff are sympathetic and understanding to the needs of the obese patient is important (Walsh et al. 2008). If invasive monitoring is to be used, informed consent in addition to the surgical procedure must be taken from the patient (Department of Health 2009).

Anaesthetic Management

Because of the engorged extradural veins and extra fat constricting the potential space, less local anaesthetic is needed for epidurals. Between 75 and 80% of the normal dose may well be sufficient (Adams and Murphy 2000).

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