Question 6

College Answer

a)
 Lower injury severity scores overall.
 More severe extremity injuries.
 More thoracic injury.
 Less brain injury – controversial.
 Longer extraction time may make for higher risk for crush injury.

b)
Airway
 Increased risk of partial airway obstruction when lying flat.
 Possibility of difficult intubation and difficult bag mask ventilation (cervical collar, neutral position, pre-existing signs of airway obstruction, possible sleep apnoea syndrome).

Breathing
 Increased difficulty inserting chest drains.
 Possible obesity hypoventilation syndrome.
 Increased risk of atelectasis.

Circulation
 Need for appropriately sized BP cuff.
 IV access more difficult so consider early inter-osseous access.

Other
 Caution with analgesia.
 Clinical signs, e.g. pneumothorax, difficult to detect by palpation and auscultation.
 Log rolling requires additional assistants.

c)
 Bedside investigation avoids transfer to CT scanner.
 Technically challenging with difficulty achieving adequate beam penetration and image quality.
 FAST is less sensitive than in non-obese.
 False positive pericardial collections are more common in the obese.

Discussion

Change in the pattern of injuries associated with morbid obesity

• Injury scores are lower in obese patients (Arbabi et al, 2003)
• Pattern of blunt trauma is different (Boulanger et al, 1992)
  • Injuries that are more likely:
    • pulmonary contusion
    • rib fractures
    • pelvic injuries
    • kneedislocations (Fuchs et al, 2014)
    • extremity fractures
    • proximal upper extremities seem to get it worst (Evans et al, 2011)
  • Injuries that are less likely:
    • head injuries
    • liver injuries
• "Obese people injured in vehicular crashes had a similar injury pattern with no difference in seating position, direction of impact, seat belt use, and ejection."

Influence of morbid obesity on the primary and secondary survey

1. - Difficult airway; difficult bag-mask ventilation more likely than actual difficult intubation.
   - Short handle may be required for direct laryngoscopy; most people would just resort to the videolaryngoscope.
   - When intubating, the FRC is small and the patient will become hypoxic rapidly, which means fewer attempts will be possible.
   - Increased risk of obstruction, even when awake
   - When obtunded, a virtual certainty of obstruction
    
2. - Poor chest wall compliance
   - Increased risk of atelectasis
   - Obesity hypoventilation syndrome
   - Difficult access for chest drains
   - Difficult windows for trauma TTE
   - Difficult auscultation and percussion, eg. for pneumothorax
   - Increased aspiration risk
    
3. - Difficulty measuring accurate blood pressure (need for appropriate size cuff)
   - Realistic possibility that no cuff will be appropriate and arterial access may be required
   - Difficult IV access- CVC as well as PIVC; the college answer recommends to go straight for the intraosseous needle
   - Intraosseous access is hardly fool-proof and can also be frustrated by obesity, considering especially the likelihood of there being bilateral knee prostheses
   - Possibility of pulmonary hypertension, cor pulmonale or CCF makes haemodynamic management more complex
    
4. - Likely, CO₂ retention and narcosis (influences doses of induction drugs)
   - Medullary sensitivity to CO₂ will be even more reduced by opiates
   - Some sort of syndromic condition may complicate neurological assessment (eg. Prader Willi syndrome)
    
5. - Log rolling will require additional assistants, or some sort of unusual equipment.

Influence of morbid obesity of FAST assessment

• Morbid obesity is one of the limitations of FAST
• Difficult insonation of the appropriate spaces; image quality is likely to be poor
• Pericardial fat can be misinterpreted as clotted blood
• Perinephric fat may be misinterpreted as intraperitoneal free fluid
• The advantage is, if you can't fit into the CT scanner this is all you've got.

Bochicchio, Grant V., et al. "Impact of obesity in the critically ill trauma patient: a prospective study." Journal of the American College of Surgeons 203.4 (2006): 533-538.

Diaz Jr, Jose J., et al. "Morbid obesity is not a risk factor for mortality in critically ill trauma patients." Journal of Trauma and Acute Care Surgery 66.1 (2009): 226-231.

Lambert, David M., Simon Marceau, and R. Armour Forse. "Intra-abdominal pressure in the morbidly obese." Obesity surgery 15.9 (2005): 1225-1232.

Boulanger, Bernard R., et al. "Body habitus as a predictor of injury pattern after blunt trauma." Journal of Trauma and Acute Care Surgery 33.2 (1992): 228-232.

Dhungel, Vinayak, et al. "Obesity delays functional recovery in trauma patients." journal of surgical research 193.1 (2015): 415-420.

Ciesla, David J., et al. "Obesity increases risk of organ failure after severe trauma." Journal of the American College of Surgeons 203.4 (2006): 539-545.

Arbabi, Saman, et al. "The cushion effect." Journal of Trauma and Acute Care Surgery 54.6 (2003): 1090-1093.

Evans, David C., et al. "Obesity in trauma patients: correlations of body mass index with outcomes, injury patterns, and complications." The American surgeon 77.8 (2011): 1003-1008.

Fuchs, I., et al. "Vascular Injury in Obese Patients after Ultra-Low-Velocity Trauma." J Anesth Clin Res 5.488 (2014): 2.