Obesity is defined by the World Health Organization as:
abnormal or excessive fat accumulation that presents a risk to health.
The Body Mass Index (BMI) is frequently used to define obesity and is calculated by a patient's weight (kg)/the square of their height (m). Normal BMI ranges from 18.5 to 25. A BMI of 25–30 is considered overweight and obesity is defined as a BMI of more that 30. Morbid obesity is defined as a BMI of 40 or greater.
Approximately 25% of adults in the United Kingdom are obese and 2% are morbidly obese. The incidence of obesity is increasing and an understanding of the specific challenges of managing the obese traumatized patient is vital for trauma clinicians.
Obesity has been shown to be an independent risk factor for mortality and multiple organ failure (MOF) following major trauma. Additionally, injury patterns differ between obese and non-obese patients. Obese patients are more likely to sustain thoracic trauma, as well as pelvic and extremity trauma compared with non-obese patients. Obese patients have been shown to sustain fewer, and less severe head injuries compared with non-obese patients. It is also a risk factor for knee dislocation, even after relatively minor trauma.
Obese patients have compromised respiratory function with reduced lung compliance. Increased chest wall resistance and increased abdominal pressure also impairs respiratory function. Obese patients are at increased risk of ARDS and pulmonary complications following trauma.
Obese patients are frequently hypertensive with an increased cardiac output and circulating volume. Myocardial hypertrophy and decreased compliance make the obese patient particularly vulnerable to changes in cardiovascular status following trauma.
Glucose intolerance, insulin insensitivity, and increased resting energy expenditure are common in obese patients. In the catabolic phase following trauma obese patients have a relative block to lipolysis and fat oxidation resulting in a preferential shift to protein catabolism. Despite their excess of fat reserves, obese patients are unable to utilize these reserves and are particularly susceptible to metabolic derangement.
Despite their excess of adipose tissue, obese patients frequently have nutritional deficiencies. This has important implications for wound healing.
Obesity is frequently associated with other co-morbidities, such as ischaemic heart disease and diabetes, which will affect the management of traumatised obese patients. Associated co-morbidities are one reason why obese patients have higher mortality following major trauma.
Principles of management
The traumatised bariatric patient presents unique difficulties to clinicians. Movement of the patient is difficult, equipment often does not fit, and assessment of injuries is more challenging.
Control of exsanguinating external haemorrhage
Massive haemorrhage must be rapidly controlled. Tourniquets may not fit obese limbs. Direct external compression of haemorrhage relies on compression of bleeding vessels against bony structures. This may be impossible with excess overlying adipose tissue and direct pressure may be insufficient. Application of haemostatic agents will be harder to apply to bleeding vessels due to substantial layers of overlying fat.
Airway with cervical spine control
Airway management is more difficult in the obese patient. Simple airway manoeuvres, such as a jaw thrust are harder to perform. Obesity is associated with obstructive sleep apnoea, which will predispose the obese patient with reduced consciousness to airway compromise. Gastro-oesophageal reflux is also more common in the obese patient, making airway protection particularly important and challenging. Laryngeal masks may not fit the anatomy of the obese patient and intubation is more demanding. Oesophageal intubation may be harder to detect and definitive airway protection may have to be deferred until arrival at the trauma centre. Surgical airway management will be extremely challenging in the obese patient with excess soft tissues obscuring the normal airway anatomy.
Cervical collars are designed to fit a variety of neck sizes. The morbidly obese patient may be too large for standard cervical collars carried by ambulance personnel and alternative methods of protecting the cervical spine may have to be employed.
Breathing and ventilation
Examination and assessment of the thorax is more challenging. Breath sounds may be harder to hear due to overlying soft tissue, tracheal displacement impossible to feel and symmetrical chest expansion harder to assess. The diagnosis of flail chest will be hard to detect. Needle thoracocentesis using a standard intravenous cannula may not be possible due to the depth of soft tissue covering the chest, so the use of a longer needle, such as a 16G spinal needle, may be required. Thoracostomy will also be more challenging due to overlying soft tissues, as will insertion of an intercostal drain.
Increased chest wall resistance and raised intra-abdominal pressure require increased airway pressures to ventilate the unconscious obese patient. This may predispose these patients to iatrogenic barotrauma.
The obese patient is at high risk of underlying cardiac disease making assessment and management of haemorrhage particularly difficult. Obese patients will frequently have underlying hypertension and relative tachycardia, and this should be considered when assessing circulatory status following trauma.
Equipment may be too small for the obese patient. Thigh tourniquets may have to be used on the upper limb. Poor peripheral vascular access will make peripheral cannulation difficult. Transport of the traumatized obese patient should not be delayed for prolonged attempts at obtaining intravenous access. Other techniques of peripheral venous access such external jugular vein cannulation may have to be used. Venous cut down is particularly useful in the obese patient as the saphenous vein remains relatively superficial at the ankle despite more adipose tissue. Insertion of central venous lines and arterial lines will be challenging for the same reasons and skin hygiene may also be difficult to maintain around vascular devices.
Obese patients should be assessed for neurological dysfunction in the same way as any other patient. As stated, airway compromise may occur with less impairment of consciousness compared with non-obese patients, due to underlying obstructive sleep apnoea. Patients should be log rolled as normal, although extra staff may be required to safely log roll the obese patient.
Obese patients are as susceptible to hypothermia as non-obese individuals. Every effort should be made to maintain the patient’s core temperature prior to arrival at hospital. Extrication and transport of the obese patient will be extremely challenging. Entrapped obese patients are more likely to have prolonged entrapment times than non-obese patients. Early consideration should be given to requesting medical personnel with advanced pre-hospital trauma skills.
Once extricated, the transport of obese patients, particularly morbidly obese patients, will require considerable numbers of personnel. The use of helicopter transport may be precluded by the size of the morbidly obese individual and liaising with the ambulance control early will help determine the most appropriate mode of transfer to the trauma centre. All personnel should be familiar with manual handling techniques. Use of these techniques will be particularly important to prevent injury to those charged with moving and transporting the morbidly obese patient. Forewarning the receiving emergency department about the patient’s size will allow extra manpower to be made available on arrival to hospital and will allow suitable trolleys and equipment to be prepared for use.
Care in the emergency department
All emergency departments should have rapid access to bariatric trolleys suitable for managing the obese patient. Standard emergency department (ED) trolleys have a weight limit of around 160 kg, whilst bariatric trolleys can carry up to 300 kg. Moving the morbidly obese patient from the confined space of an ambulance to the resuscitation room will be difficult. The use of additional staff, such as hospital security, to assist in transferring these patients should be employed.
The diagnostic challenges of the obese patient
Management in the ED should follow the standard approach as for any other patient. The identification of life-threatening complications during primary survey is more challenging in the obese patient. As stated previously, maintaining and protecting the airway and cervical spine is particularly challenging. The use of fibreoptic equipment to aid intubation is particularly useful. Examination of the thorax may give limited signs of life-threatening complications—breath sounds may be masked, asymmetrical chest movements may not be apparent, flail chest may not be visible, and thoracic wounds may be obscured by skin folds. Adequate standard chest radiography may not be possible and several attempts may be required to view the entire thorax. Overlying adipose tissue may mask subtle radiographic changes. Obese patients are at particular risk of thoracic injuries and respiratory complications following trauma. The insertion of an intercostal drain (ICoD) is performed using standard techniques, but the use of an assistant will be invaluable and is strongly advised. Standard needles may not penetrate sufficient depth for the administration of local anaesthesia and longer needles, such as a 16G spinal needle should be available. Positioning the ICoD in a skin fold may make subsequent skin hygiene more difficult to maintain. Where possible the ICoD should be inserted away from skin creases.
Identifying the source of haemorrhage
The obese patient will show the same features of haemorrhagic shock as the non-obese patient. However, obese patients often have underlying hypertension and relative tachycardia. This should be considered when making decisions about their circulatory status. Vascular access will be more challenging and venous cut downs or central venous access may be required. The use of ultrasound to identify peripheral veins is particularly useful to avoid these measures.
The obese patient displaying signs of haemorrhagic shock presents a unique diagnostic challenge. Efforts to identify the source, or sources, of haemorrhage will be more difficult. Clinical signs of haemothorax will be masked. The chest radiograph may be inadequate and subtle signs of thoracic haemorrhage may be masked. Examination of the obese abdomen will be harder to interpret than the non-obese abdomen. Tenderness will be harder to localize and bruising may be less apparent. Examination of the pelvis and long bones will also be more difficult.
Haemorrhagic shock in the presence of a pelvic fracture should be treated with a pelvic splint. Commercially available splints may not fit around the obese patient and a sheet tied firmly around the greater trochanters may be used instead. Another sheet should be applied around the legs holding the limbs in internal rotation. Femoral fractures should be treated with traction. In the absence of a suitably sized Thomas splint then skin traction can be used instead. Significant external haemorrhage should still be easy to identify. External haemorrhage from upper limbs should be treated with elevation and direct compression. The use of a thigh tourniquet may be required for the obese upper limb. Massive lower limb haemorrhage should also be treated with a tourniquet and the absence of a suitably large tourniquet may require one to be improvised, such as with a pelvic splint.
The obese patient with severe unresponsive haemorrhagic shock should proceed directly to the operating theatre in the same way that a non-obese patient would. Early involvement of senior surgeons will facilitate the appropriate surgical strategy to be employed to control massive haemorrhage. Forewarning theatres of the patient’s size, in addition to the usual information, is particularly important in organizing a bariatric surgical table and other equipment.
Patients displaying enough haemodynamic stability to be further investigated should have further radiographic imaging. Focused Assessment with Sonography for Trauma (FAST) is usually an accurate and rapid way to identify intraperitoneal haemorrhage in shocked patients. The thick layers of adipose tissue in obese patients may prevent accurate images being obtained. This may preclude the use of FAST scans, particularly in the morbidly obese patient.
Computed tomography (CT) scans are particularly useful in identifying sources of haemorrhage in patients with appropriate haemodynamic stability. Obese patients present a particular challenge. The maximum table weight of most CT scanners is around 210 kg. Some regional centres have CT scanners designed for bariatric patients, although the transport considerations in the context of acute trauma are likely to prevent this. If it is logistically possible for the obese patient to be scanned this should proceed as rapidly as possible, as it would for the non-obese patient. Extra personnel will be required to physically move the patient on to the CT scanner and this is likely to take longer than normal. This makes it particularly important that the trauma team should accompany the patient to the CT scanner.
In the event that the morbidly obese patient cannot logistically be scanned, consideration should be made for the use of diagnostic peritoneal lavage (DPL). Use of DPL in identifying intra-abdominal haemorrhage has been largely superseded by FAST and early CT scanning, but it may continue to have a role where CT scanning is not possible.
The obese patient with haemodynamic stability following trauma should have a secondary survey as usual. Injuries are harder to identify than in non-obese patients. Injuries frequently missed include carpal and finger fractures, and soft tissue knee injuries. A tertiary survey should be performed the following day to minimize the risk of delayed diagnosis of injuries.
As for all patients, planning the definitive management in the obese patient will depend largely on the injuries sustained. All injuries should be identified as early as possible and prioritized accordingly. In the context of multiple trauma, communication and planning between different clinical specialities is particularly important. Ideally, this multidisciplinary co-ordination should commence as soon as the patient arrives at hospital. The obese patient is likely to have other co-morbidities and less physiological reserve compared with non-obese individuals. Clinicians should have a low threshold for adopting a damage control approach to the management of these patients.
Multiply-injured obese patients are likely to require critical care support. Co-morbidities should be identified and addressed as soon as possible, if necessary liaising with the patient’s general practitioner. Obese patients are likely to have poor respiratory function and are at higher risk of acute respiratory distress syndrome (ARDS) compared with non-obese patients. Adequate analgesia following thoracic trauma is particularly important in this patient group and early consideration should be made about the use of regional anaesthesia. The conscious patient should be able to cough up their sputum and respiratory physiotherapy is particularly useful in preventing respiratory complications. Such complications should be identified and treated as early as possible.
Obese patients are also at particular risk of venous thrombo-embolism, in part due to their relative immobility. Appropriate prophylaxis should be used, unless contraindicated. Early mobilization should be initiated wherever possible. The size of the obese patient presents a considerable challenge to nursing staff. Patients should be nursed on an appropriate bariatric bed. Obese patients are at particular risk of skin complications, particularly unconscious or immobile patients. Prevention, identification, and management of pressure sores are made more difficult by their physical size. At risk patients should be nursed on the appropriate mattresses and extra staff may have to be made available by ward managers to facilitate regular turning of patients.
Fracture management in the bariatric patient
The obese patient poses a particular challenge to the orthopaedic trauma surgeon. Surgical exposure of fractures is particularly difficult. Standard implant designs may not be strong enough to withstand the additional body weight of the obese patient. This is more likely if the obese patient is unable to keep their body weight off a lower limb fracture with the use of crutches. If surgical fixation of a fracture is necessary, implant selection should be influenced by the extra forces that the implant must withstand prior to fracture union. For example, a large solid nail may be preferable to a small cannulated nail. The obese patient is equally at risk of compartment syndrome and this complication should be actively excluded, particularly in the unconscious patient. Plaster casts are harder to apply and the obese patient is at particular risk of skin complications beneath the plaster. Care should be taken to pad skin areas at risk and folds and finger prints in the plaster avoided. Standard orthotic devices such as Thoracic-Lumbar-Sacral orthosis (TLSO) may not fit and alternatives may have to be sought.
Despite their normal dietary calorific excess, obese patients are at risk of malnutrition. This may influence wound healing following trauma. Following major trauma the obese patient has a relative block to lipolysis and fat oxidation resulting in a preferential shift to protein catabolism. The multiply-injured obese patient should have their nutritional status assessed as part of their definitive care and the involvement of a dietician may be particularly useful. Strategies for affecting long-term weight loss should also be considered when the patient is recovering from their injuries.
• The incidence of bariatric patients sustaining major trauma will increase in the next decade.
• Standard equipment may not fit the obese patient and appropriate bariatric equipment should be readily available to clinicians involved in trauma management.
• Forewarning colleagues of the patient’s size allows appropriate equipment to be prepared.
• Management should follow established trauma protocols. However, it should be recognized that these patients present a significant diagnostic and therapeutic challenge to trauma practitioners. Timely senior clinical involvement is essential.
• Bariatric patients are more likely to have underlying co-morbidities and are at higher risk of morbidity and mortality following trauma. These risks should be identified and steps taken to minimize them following trauma.
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