Obesity/High body Mass Index– what are the risks?

We define obesity according to a patient’s body mass index (BMI). This is a measurement that takes into account a person’s weight and height. 

Your BMI is …………… 

Important – If your BMI is more than 35kg/m2, your surgeon and anaesthetist may recommend that you lose weight prior to surgery. This may result in your surgery being delayed until you have lost sufficient weight. This is because the risks of having surgery with an elevated BMI may be too high.

If you are obese, particularly if your waist measurement is more than half of your height, you are at risk of obesity-related conditions. These include: 

• High blood pressure.  
• Diabetes.  
• Obstructive sleep apnoea - this is a condition when a person snores very heavily and stops breathing for short periods during sleep. It is important to tell you anaesthetist if you have these symptoms. 
• Angina. This is chest pain which occurs due to narrowing of the blood vessels in your heart. If you have angina, you are at risk of having a heart attack.  
• Blood Clots in your legs or lungs. 
• Abnormal heart rhythm and sudden unexpected death.

Your risk of having a serious complication during or after surgery is increased if you are obese, especially if you have any obesity-related conditions.  

Problems encountered during surgery: 

• Surgical difficulties - the surgeon may struggle to perform the surgery due to the increased fat layers. 
• Longer operation time - due to potential surgical and anaesthetic difficulties. 
• Maintaining oxygen levels - the anaesthetist may have difficulties inserting a breathing tube and maintaining adequate levels of oxygen in your blood. 
• Heart problems - your heart may be affected by the anaesthetic drugs. 

After an operation, obese patients are more likely to experience: 

• Chest infections or difficulties breathing - if this occurs, you may need antibiotics, physiotherapy and occasionally, assistance with your breathing which requires admission to the critical care unit. 
• Wound infections and poor wound healing - your wound may be slow to heal, and this increases the risk of infections. This may need antibiotics or a further operation. Once healed, the scar may be more prominent. 
• Blood clots in the legs or lungs - this usually requires treatment with blood thinning medication. Blood clots in the lungs can be life-threatening. 

If you develop complications after surgery, you may need to be in hospital for a longer time than is usually required.

Before surgery: 

• Lose Weight - Consult your GP about a weight reduction programme. 
• Stop smoking - Your GP can also help with this. 
• Exercise regularly - This helps to improve your fitness and increases your body’s ability to cope with the stress of surgery. 
• Diabetes control - Good control of your blood sugar is important for wound healing and to reduce infection. 
• Obstructive sleep apnoea - if you have a CPAP(continuous positive airway pressure) machine, use it regularly and ensure you bring it to hospital when you come for your operation. 
• Medication - continue to take your regular medication as prescribed by your GP unless advised otherwise by your surgeon or the pre-assessment team.          

After surgery: 

• Deep breathing exercises can reduce the chance of developing a chest infection. 
• Get out of bed and move around as soon as possible as advised by your doctor. Not moving around can increase the risk of chest infections or blood clots developing in your legs or lungs.  
• Blood thinning medication may be prescribed by your doctor to reduce the change of blood clots developing after surgery. This is usually a daily injection under the skin. 

NHS website

The Association of Anaesthetists 

The Society of Bariatric Anaesthesia 

UCL Hospitals cannot accept responsibility for information provided by external organisations.

Queen Square Pre-Operative Assessment Centre   

National Hospital for Neurology and Neurosurgery  

Box 61, Queen Square, London, WC1N 

020 3448 3348