Since the 1980s, minimally invasive techniques have been applied to an increasing number and variety of surgical procedures with a gradual increase in the complexity of procedures being successfully performed laparoscopically. In the past, obesity was considered a contraindication to laparoscopy due to the higher risk of co-morbid conditions such as diabetes, hypertension, coronary artery disease and venous thromboembolism. Performing laparoscopic gynaecological procedures in morbidly obese patients is no longer a rare phenomenon; however, it does necessitate changes in clinical practice patterns. Understanding of the physiological changes induced by laparoscopy, particularly in obese patients, is important so that these may be counteracted and adverse outcomes avoided. Laparoscopy in obese patients confers certain advantages such as shorter hospital stay, less post-operative pain and fewer wound infections.
In addition to these benefits, minimal-access surgery has been demonstrated as safe and effective in obese patients; however, specific surgical strategies and operative techniques may need to be adopted.
Introduction
The worldwide prevalence of obesity has reached epidemic proportions, and recent figures have shown that 26% of the UK population has a body mass index (BMI) ≥30 kg/m 2 . The health implication of obesity has been well established, and it is associated with a variety of medical conditions, in addition to adversely affecting morbidity and quality of life. Physicians of all backgrounds and specialties have had to adapt their practice to manage the specific challenges posed by obesity, and gynaecology is no exception. Modern laparoscopy has continued to evolve enabling more complex procedures to be successfully performed using minimally invasive techniques. Laparoscopy is particularly well suited for treatment of gynaecological diseases in obese patients due to faster recovery and lower rates of wound infections.
Obesity – a health burden
Obesity is a term most commonly used to define an excess of body fat, usually relating to increased weight for height. The most common method of measuring obesity is the BMI, a universally recognized scale allowing for comparisons between different countries and populations. The World Health Organization distinguishes between different categories of BMI and defines class 1 obesity as BMI >30, class II obesity BMI 35–40 and class III or morbidly obese as those with a BMI >40 ( Table 1 ) . Modifications to these categories do exist with some surgical literature including an additional class of super obesity for those patients with a BMI >45. Other organizations, notably the National Institute for Health and Clinical Excellence (NICE) recommend the use of BMI in conjunction with waist circumference, specifically for those patients with a BMI <35 . Abdominal obesity assessed by waist circumference is a predictive factor in obesity-related health risk and correlates well with abdominal fat content. A raised waist circumference is defined as >102 cm in men and 88 cm in women. These sex-specific cut-offs can be used to identify those patients at an increased risk of developing obesity-related diseases, notably type 2 diabetes, hypertension and cardiovascular vascular disease. An increased waist circumference can be a marker for increased risk even in people of normal weight, and substantial evidence indicates that waist circumference is a stronger marker of health risk than BMI alone . However, amongst the morbidly obese, waist circumference adds little to the measure of risk secondary to BMI.
| Body mass index | Obesity class | Disease risk according to waist circumference | ||
|---|---|---|---|---|
| Women < 88 cm | Women > 88 cm | |||
| Underweight | <18.5 | |||
| Normal | 18.5–24.9 | |||
| Overweight | 25.0–29.9 | Increased | High | |
| Obesity | 30–34.9 | I | High | Very high |
| 35.0–39.9 | II | Very high | Very high | |
| Morbidly obese | >40.0 | III | Extremely high | Extremely high |
The prevalence of obesity continues to rise with a year-on-year increase. This epidemic brings with it huge health implications and represents a huge strain on National Health Service (NHS) resources. Based on the latest available health surveys, more than half of the adult population (52%) in the European Union reported that they were overweight or obese . In recent years, the obesity rate has doubled in many European countries and is currently 26% in the UK . Obesity is also attributed with developing a wide range of medical conditions, including type 2 diabetes mellitus, stroke, ischaemic heart disease, hypertension, osteoarthritis, depression and many common cancers (i.e., endometrial and breast cancer). These diseases, although preventable, cause over 10,000 obesity-related premature deaths annually in the UK . Recent studies demonstrated BMI as a strong predictor of mortality among adults. Moderate obesity (30–35 kg/m 2 ) was found to reduce life expectancy by an average of 3 years, whilst morbid obesity reduced life expectancy by 8–10 years, a finding equivalent to the effect of lifelong smoking . Annual medical spending attributed to obesity is considerable and continues to rise. The current cost to the NHS of treating obesity-related condition exceeds £5 billion per year with indirect costs to wider society at approximately £20 billion per year . If obesity continues to rise at the present rate, the cost to the NHS of treating obesity-related conditions has been projected to reach £10 billion per year by 2050 .
Obesity – a health burden
Obesity is a term most commonly used to define an excess of body fat, usually relating to increased weight for height. The most common method of measuring obesity is the BMI, a universally recognized scale allowing for comparisons between different countries and populations. The World Health Organization distinguishes between different categories of BMI and defines class 1 obesity as BMI >30, class II obesity BMI 35–40 and class III or morbidly obese as those with a BMI >40 ( Table 1 ) . Modifications to these categories do exist with some surgical literature including an additional class of super obesity for those patients with a BMI >45. Other organizations, notably the National Institute for Health and Clinical Excellence (NICE) recommend the use of BMI in conjunction with waist circumference, specifically for those patients with a BMI <35 . Abdominal obesity assessed by waist circumference is a predictive factor in obesity-related health risk and correlates well with abdominal fat content. A raised waist circumference is defined as >102 cm in men and 88 cm in women. These sex-specific cut-offs can be used to identify those patients at an increased risk of developing obesity-related diseases, notably type 2 diabetes, hypertension and cardiovascular vascular disease. An increased waist circumference can be a marker for increased risk even in people of normal weight, and substantial evidence indicates that waist circumference is a stronger marker of health risk than BMI alone . However, amongst the morbidly obese, waist circumference adds little to the measure of risk secondary to BMI.
| Body mass index | Obesity class | Disease risk according to waist circumference | ||
|---|---|---|---|---|
| Women < 88 cm | Women > 88 cm | |||
| Underweight | <18.5 | |||
| Normal | 18.5–24.9 | |||
| Overweight | 25.0–29.9 | Increased | High | |
| Obesity | 30–34.9 | I | High | Very high |
| 35.0–39.9 | II | Very high | Very high | |
| Morbidly obese | >40.0 | III | Extremely high | Extremely high |
The prevalence of obesity continues to rise with a year-on-year increase. This epidemic brings with it huge health implications and represents a huge strain on National Health Service (NHS) resources. Based on the latest available health surveys, more than half of the adult population (52%) in the European Union reported that they were overweight or obese . In recent years, the obesity rate has doubled in many European countries and is currently 26% in the UK . Obesity is also attributed with developing a wide range of medical conditions, including type 2 diabetes mellitus, stroke, ischaemic heart disease, hypertension, osteoarthritis, depression and many common cancers (i.e., endometrial and breast cancer). These diseases, although preventable, cause over 10,000 obesity-related premature deaths annually in the UK . Recent studies demonstrated BMI as a strong predictor of mortality among adults. Moderate obesity (30–35 kg/m 2 ) was found to reduce life expectancy by an average of 3 years, whilst morbid obesity reduced life expectancy by 8–10 years, a finding equivalent to the effect of lifelong smoking . Annual medical spending attributed to obesity is considerable and continues to rise. The current cost to the NHS of treating obesity-related condition exceeds £5 billion per year with indirect costs to wider society at approximately £20 billion per year . If obesity continues to rise at the present rate, the cost to the NHS of treating obesity-related conditions has been projected to reach £10 billion per year by 2050 .
Physiological considerations in the obese patient
Obesity is often associated with hypertension, which may lead to left ventricular hypertrophy. Cardiac response is often altered in patients with an increased BMI due to increased metabolic demands and resultant increased preload and resting cardiac output. Larger cardiac stroke volume and raised cardiac output can lead to additional strain on the heart resulting in hypertension, cardiomegaly and eventual congestive cardiac failure. Studies have demonstrated a higher risk of death in patients with ventricular hypertrophy and cardiac failure caused by obesity . Unexplained cardiac arrhythmias have also been demonstrated as more prevalent in obese patients .
Obese patients may also be affected by altered respiratory physiological functioning. Oxygen consumption is often increased due to increased metabolic demand in addition to an increase in carbon dioxide production. This predisposition for hypercapnia is a direct result of reduced chest wall compliance as a result of excess adipose tissue located around the ribs, diaphragm and intra-abdominally. This combination of increased oxygen consumption and reduced chest wall compliance leads to decreased lung compliance, lower expiratory reserve volume and decreased functional reserve capacity.
Both supine positioning and anaesthesia in the obese patient can further compromise functional residual capacity (FRC) to levels lower than closing capacity leading to airway closure and potential hypoxaemia. In morbidly obese patients, the vital capacity is reduced by 20%, voluntary ventilation by approximately 30% and expiratory reserve by 30–60% . These values may be further compromised in patients with obstructive sleep apnoea conditions.
Laparoscopic surgery requires establishing a pneumoperitoneum using carbon dioxide to create enough space for the surgeon to operate. As the abdominal volume increases, so too does the intra-abdominal pressure (IAP). This increase in IAP in conjunction with Trendelenburg positioning can lead to raised intra-thoracic pressure and reduced FRC resulting in airway closure and resultant ventilation perfusion mismatch with potential hypoxaemia . Carbon dioxide used to maintain the pneumoperitoneum can be absorbed leading to an increase in PaCO 2 , further aggravated by the ventilation perfusion mismatch . Increased IAP during laparoscopy leads to increased systemic vascular resistance and subsequent mechanical compression of the aorta. This sequence of events results in activation of the renin–angiotensin–aldosterone system. Compression of the vena cava leads to a decrease in cardiac output and arterial pressure and a resultant decrease in cardiac output further exacerbated by the Trendelenburg potion and cephalad displacement of the diaphragm . Steep Trendelenburg positioning for prolonged procedure (>4 h) can rarely cause compartment syndrome, which is caused by a combination of reduced perfusion of lower limbs in a raised position, compression of venous vessels with limb supports and reduced drainage secondary to pneumoperitoneum .
Gastric functioning may also be affected by obesity. Patients are likely to have larger gastric volumes, greater acidic gastric contents and delayed emptying, putting them at a higher risk of aspiration during surgery . It is for this reason that prophylaxis is often recommended in the form of an H2 blocker (ranitidine) and a pro-kinetic (metoclopramide) given 12 and 2 h prior to surgery .
The relationship between obesity and an increased risk of infection has been demonstrated, although the precise mechanism remains unclear. Obesity has been shown to impair immune surveillance leading to impaired chemotaxis and macrophage differentiation . Studies have consistently shown that obesity is associated with an increase in the risk of urinary tract infection (UTI). Semins et al. demonstrated that pyelonephritis was almost five times more common in obese female patients compared to non-obese . Several studies have also confirmed obesity to be associated with an increased risk of skin and soft tissue infection. For these reasons, broad-spectrum antibiotic prophylaxis should be administered to patients especially those who are morbidly obese. If possible, open surgery should be avoided as a meta-analysis demonstrated a 70–80% reduction in surgical site infection in obese patients undergoing laparoscopic surgery compared to open surgical procedures .
Exposure techniques and patient positioning
Exposure of the operative field is one of the single most important steps when performing laparoscopy in obese patients. Careful preoperative planning is important to optimize patients from a cardiorespiratory perspective to ensure patients can tolerate Trendelenburg positioning for even long periods of time. Equal importance is placed on ensuring sufficient bowel preparation is given so as to optimize exposure, thereby enabling more complex procedures to be successfully performed laparoscopically. During laparoscopic surgery, the surgeon is obliged to work in a confined space using small delicate instruments for precise dissection. A bowel void of faecal and gaseous content is often easier to handle and place above the promontory, so as to free the pelvis and improve access and exposure to the pelvic organs. For low-complexity procedures, a low-residue diet for 5–7 days prior to surgery is recommended . For more complex surgery, such as in cases of deep endometriosis, an additional enema the night before surgery is advised. In addition to this, some colorectal surgeons recommend an additional enema 2–3 h prior to surgery. A recent randomized study demonstrated that the quality of exposure of the operative field in patients undergoing gynaecological laparoscopic procedures is similar following mechanical bowel preparation when either oral or enema preparations are used . However, only a few studies included laparoscopic procedures. Deciding which preparation to use should be individualized according to patient’s needs and pre-existing medical conditions.
Patient position is equally important and sufficient time should be taken to ensure patients are installed correctly, especially when lengthy surgical procedures are anticipated. Obese patients are at a higher risk of pressure sores and nerve injuries as a result of prolonged compression. Compression of ≥6 h can lead to permanent injuries with the most frequently occurring nerve injuries in obese patients being ulnar and sciatic neuropathies.
To combat these obstacles, the maximal weight capacity of the operating table should be checked or alternatively a bariatric bed used. These beds are typically wider providing ample space for the arms to be tucked alongside the patient’s body. Avoid placing the arms in the extended position so as to optimise positioning of the surgeon and in turn prevent the surgeon leaning on the patient’s arms, which can sometime result in brachial plexus injuries. Padded stirrups with extra padding around pressure points such as the ankles and knees should be used in addition to leg compression devices to minimize the risk of venous thromboembolism ( Fig. 1 ).
