Prophylactic antiemetics in trauma

The evidence base supporting the prehospital use of prophylactic anti-emetics is limited.  Some jurisdictions administer at least one anti-emetic to trauma patients in an effort to prevent nausea and vomiting in this setting.  Whilst there is no good evidence to support the routine administration of metoclopramide when morphine is administered in the acute care setting ( Simpson et al. Emerg Med Australas 2011 23(4): 452-7) there are logical reasons why prophylactic antiemetics are given for patients with trauma. Patients with traumatic injuries typically experience pain and are commonly administered opiate / opioid analgesics both of which are associated with increased rates of nausea and vomiting.  Additionally many trauma patients have their spine immobilised for the transport to hospital which typically includes the fitting of a semi-rigid cervical collar and being secured to a spine board or stretcher. Additionally these patients may have impaired airway reflexes, delayed gastric emptying and motion sickness all contributing to an increased risk of aspiration.

A recent epidemiological study by Easton et al. (Journal of Trauma and Acute Care Surgery 2012, 72(5): 1249-1254) has described the prevalence and risk factors for prehospital nausea and vomiting after trauma.  They report (in their convenience sample of 196 adult trauma patients) that 38% of patients in this cohort experience nausea and 8% vomited.  Prophylactic anti-emetics were given to 79 patients (40%).  Both metoclopramide and ondansetron were administered to 30/79, metoclopramide only 46/79, and ondansetron only 3/79.  Nausea occurred in only 5% of patients treated with prophylactic anti-emetics compared with 61% of patients not given an anti-emetic.  Importantly, no patient given both agents (metoclopramide and ondansetron) developed symptoms.  Key risk factors for the development of vomiting were injury severity (ISS > 10), older age (>75 years), weight (> 105 kg) and female gender.

The study conclusions were as follows: “Prehospital nausea and vomiting are more common in our cohort of trauma patients than the reported rates in the literature for nontrauma patients transported to hospital by ambulance. These symptoms were associated with female gender, older age, weight, and greater ISS. Our results suggest that antiemetics may be underused in trauma patients, both for prophylaxis and the treatment of active symptoms”. 

An alternate way of looking at this data is to consider how effective is the intervention:

  1. In this study the use of anti-emetics decreases the risk of nausea by 56% (95% CI 45%-66%) therefore only two patients need to be treated to prevent one patient from becoming nauseated.
  2. In this study the use of anti-emetics decreases the risk of vomiting by 9% (95% CI 2%-15%) therefore only twelve patients need to be treated to prevent one patient from vomiting.

Given nausea is a distressing symptom (and can be more so than pain) and that vomiting significantly increases the risk of aspiration and could worsen outcomes for patients with clinically important spinal injuries and that there is evidence that antiemetics in this setting are associated with significantly (statistically and clinically) lower rates of both nausea and vomiting, the routine use of antiemetics in this population appears justified.  Antiemetics should especially be considered in the severely injured, old, obese and female patient groups.

A prospective randomised controlled trial is needed to provide a higher level of evidence looking at a more inclusive population and measuring all  important outcomes (including adverse / side effects of medications).  In the mean time however it appears that the benefits of prophylactic antiemetics outweighs the risks.

Note: the full text of this article is available via CIAP for those readers working for NSW Health

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