Pre‐Operative Assessment Goals

Conceptually, pre‐operative assessment aims to identify co‐morbid and pathological conditions, assess the absolute and relative risk posed by those conditions and address these. Addressing will ideally be to optimally manage conditions to produce the lowest overall risk and communicate these risks, individualised to the greatest degree possible to the patient and the multi‐professional team involved.

On a wider level, the pre‐operative process should be an opportunity to gather information to facilitate scheduling of cases and identify factors that may be associated with longer operative times and adverse outcomes. The harvested data should also provide indications of the calibration of prediction tools and/or the perception of service performance.

There are many health conditions that are reported to be associated with poor operative outcomes in general. These amplified risks equally apply to the bariatric patient, e.g. diabetic control, liver disease, sleep apnoea, but may be of a much higher prevalence in the bariatric population.

In the bariatric patient, there may be a large number of specialist teams involved and it is the function of the pre‐operative service to seek, collate and balance these recommendations. In the UK, with medical weight management services often involved prior to surgical, there is an opportunity to present a patient to a surgical service with many conditions identified and optimised (see Chapters 8–10 – pre‐operative management relating to medical, dietetic, lifestyle and psychological aspects).

However, it is important that there is an appreciation that surgery is not a static continuation of risk but is a dynamic process, involving raised physiological load, physical risk and the significant potential for a patient to suffer a ‘waterfall’ effect, with a complication becoming directly detrimental and then a compounding of effect.

With this in mind, it is important that there is a continued move away from the mindset of ‘fit for anaesthetic’ to ‘risks optimised for intended surgery and potential complications…’.

Body Mass Index (BMI), Phenotypes and Mass

Body mass index is associated with increased operative risk. However, in planning care, it is important to also consider both absolute mass and weight distribution. Predominant abdominal adiposity is not only associated with increased risk of metabolic disease states, but this distribution also predicts operative difficulty and poor respiratory performance.

Commonly, there is a failure to appreciate increased depth of cervical and upper thoracic spinous processes, leading to difficulty in airway management and brachial plexus injuries. Identification should direct enhanced focus towards operative positioning.

Figures 12.1 and 12.2 illustrate problem of supine neck extension, the increased depth of anterior and posterior adipose layers and the airway fat deposition (normal airways are approximately 25 mm at narrowest point; this is a 10 mm external diameter with an endotracheal tube in situ). Since airway flow resistance is related to the fourth power of radius, in this case, this patient can be extrapolated to have a 16‐fold increased difficulty in breathing. The massing of the breasts on the chest reduces lung volumes, and mean normal airway access is hindered (these patients’ supine also always looks steep head down as a result).

BMI rises may be predominantly lymphoedema in the abdominal apron and lower limbs. Special consideration should be given, regarding the potential to provide a bespoke operating environment including table width. A large abdominal apron may have a pendulous effect and need appropriate control strapping. In large dependent areas, there are also likely to be trophic skin changes with the potential for large but superficial varicose veins to underly, making careful attention to skin care essential.

Absolute mass and physical dimensions may need teams to consider the equipment available for the whole of the operative period. In clinics and wards, appropriate chairs and toileting should be available. Manual handling for transfers needs to be actively considered, such as mass‐appropriate bed frames, mattresses, mobility aids and transfer aids such as pneumatic transfer mats and jacks. Operating tables and other mechanical devices may have not only a static weight limit, but a safe movement limit based on motor or gearing. This also applies to imaging modalities where both table limits and scan orifice size may need to be borne in mind.