Obesity rates continue to increase throughout the world. Associated with this is the increased presence of co-morbid conditions including the Metabolic Syndrome. Whilst the syndrome can occur without co-existing obesity, its presence is over-represented in the obese population.
A syndrome is a concurrence of signs, symptoms, or morbidities that together consistently define a condition. The Metabolic Syndrome is one syndrome that is increasingly recognised in modern medical practice. However, confusion is commonly encountered with this condition that translates into difficulties with identification and management, in particular for the anaesthetist in the peri-operative period.
This report intends to provide a very simple review of the metabolic syndrome and an introduction to the implications for the anaesthetist, and allow the reader to grasp the basics of this condition for application to clinical practice.
At Euroanaesthesia 2018 in Copenhagen the metabolic syndrome and its management, particularly in relation to the obese patient, will be considered as part of the pre-Congress seminar Key issues for the morbidly obese patient. This seminar will be delivered by experts from the Society for Obesity and Bariatric Anaesthesia (SOBA UK) and the European Society for care of the obese patient (ESPCOP). Readers are recommended to register for this seminar to hear more on this topic.
What is the Metabolic Syndrome?
The metabolic syndrome has been documented in medical papers since the 1950s. There are numerous descriptions of the same process – an increased tendency to the development of central abdominal obesity, diabetes mellitus, and atherosclerotic disease processes with an increased risk of death. Various names became associated with this condition – Reaves Syndrome, Syndrome X, and Insulin resistance syndrome are but a few. These different names have added to the confusion over a number of years, but all describe the same process – Metabolic Syndrome.
Increasingly apparent is the appreciation that one does not have to be obese to develop the metabolic syndrome. Certain ethnic groups, for example Asian origin, will develop metabolic syndrome and its associated complications at lower weights.
Facts and Figures
Up to 40% of adults in the Western world are thought to have metabolic syndrome. Some uncertainty exists due to the various names applied to the condition and different diagnostic criteria (see below). Increasing weight is associated with an increased risk of syndrome development – 5% of normal weight individuals, 22% of overweight individuals, and 60% of those who are obese. The presence of the metabolic syndrome results in a threefold increase of myocardial infarction or stroke and fivefold risk of type two diabetes mellitus development.
How to diagnose the Metabolic Syndrome
Numerous classifications exist to diagnose the presence of the metabolic syndrome: the International Diabetes Federation (IDF), World Health Organization (WHO), National Cholesterol Education Programme (NCEP), and American Heart Association (AHA). These different classifications add to the confusion surrounding this syndrome as they do not all agree on the numerical integers for the components assessed.
Whilst these classifications are perfectly acceptable for use in an outpatient or research arena, they do not lend themselves to use by an anaesthetist as part of their pre-operative assessment. A simple approach is required to identify the presence of this condition. Removing the complicating numerical indices from these classifications facilitates easy identification of the components. Metabolic syndrome is diagnosed with the presence of three of the following:
- Visceral obesity
- Low HDL Cholesterol
- Raised Triglycerides
- Abnormal raised blood sugar
What are the peri-operative risks?
With the exception of weight loss surgery, peri-operative risks for all types of surgery are increased morbidity and mortality. In cardiac surgery the presence of the metabolic syndrome increases mortality from 0.9% to 2.4%. Complications also increased, in particular, significant morbidity – stroke, myocardial infraction, kidney failure, and infection rates.
In non-cardiac surgery the presence of metabolic syndrome confers increased peri-operative risks as well. Length of hospital stay, significant peri-operative complications, and mortality are all increased compared with individuals who do not have the syndrome.
For non-cardiac surgery patients who have treated components of the metabolic syndrome, there remains a two-fold increased risk of cerebrovascular complication and up to a seven fold increased risk of renal failure.
Anaesthetic considerations and optimisation of the metabolic syndrome
It is clear from the above commentary that the presence of the metabolic syndrome results in significant issues for anaesthesia. Anaesthetic considerations start with the first patient encounter and diagnosis of the syndrome. A simple approach to bedside diagnosis utilising the approach outlined above is an ideal starting point.
Optimisation of the components identified as part of this syndrome must wherever possible be undertaken prior to surgery. This advocates and supports identification and optimisation as early as possible in the patient pathway. Ideally, no patient should undergo surgery until optimised. The exception to this would be emergency surgery.
All patients should be advised to undertake exercise to improve cardio-respiratory profiles. The added benefit to this will be a degree of weight loss and consequent reduction in effects of the metabolic syndrome.
Glycaemic control must be optimised and avoidance of hyperglycaemia. Concerns have been raised that peri-operative tight sugar control may result in episodes of hypoglycaemia and consequent morbidity. Avoiding rigid protocols and narrow ranges of blood sugar targets should therefore be avoided in the peri-operative period.
The presence of visceral obesity is intimately linked to the development of metabolic syndrome. Pre-operative weight loss must be obtained in this group. Initially visceral, metabolically active fat is reduced with a reduction in the drivers for the syndrome. Weight loss surgery has been demonstrated to be effective in ‘switching’ off the metabolic syndrome. However, this is a major undertaking and should not be considered as first line management for these patients.
Smoking is a powerful catalyst for the development of adverse atherosclerotic events in metabolic syndrome as well as the well-known association with peri-operative respiratory events. Cessation of smoking must be undertaken pre-operatively and appropriate support provided to patients to ensure continued abstinence.
Untreated hypertension is associated with adverse events in the peri-operative period. Pharmacological optimisation must be undertaken prior to surgery to minimise development of adverse events.
Lipid lowering therapy has been demonstrated to have beneficial effects. The statin group of lipid modifying agents also have anti-inflammatory, anti-thrombotic properties that are useful in this group.
Other obesity-related morbidities will also be encountered more frequently in patients with the metabolic syndrome. Assessment for these conditions, such as sleep disordered breathing must be undertaken and appropriate therapy and optimisation undertaken.
References & Further Reading
- Tung A. Br J Anaesthesia 2010;105(S1):24-33.
- Tzimas P, Petrou A, Laou E, et al. Br J Anaesthesia 2015;115(2):194-202.
- Perioperative management of the obese surgical patient 2015. AAGBI & SOBA UK. https://www.aagbi.org/sites/default/files/Peri_operative_management_obese_patientWEB.pdf
Dr D Christopher Bouch
MB ChB FRCA EDICM FFICM
Consultant in Anaesthesia & Intensive Care Medicine
Leicester Royal Infirmary, Leicester, UK
Society for Obesity and Bariatric Anaestheisa