Acute extrapyramidal symptoms (EPS) are possible with most antiemetic medications, especially the phenothiazines (promethazine and prochlorperazine). The two most common acute examples of EPS are the dystonic reaction and akathisia. Dystonia manifests as involuntary, sustained muscle contractions, often in the head or neck region. Torticollosis is one example.
Akathisia is underappreciated by most emergency medicine providers. Patients report having "restlessness and inner tension or discomfort, an urge to constantly move their legs, and difficulty in maintaining a posture for several minutes, such as sitting still in a chair or standing in one place. They display semi-purposeful or purposeless limb movements and tend to repeatedly shift their bodily position while sitting, and shift weight from foot to foot or pace while standing. In its milder presentation, the disorder may resemble anxiety."9 It is easily mistaken for anxiety or agitation. EMS systems that treat N&V should have protocols in place to treat EPS. Paramedics must familiarize themselves with the various symptoms of EPS and be ready to administer diphenhydramine or benzodiazepines.
Our first medication takes us back to the basics. There is research suggesting that supplemental oxygen reduces the incidence of nausea and/or vomiting during ambulance transport of patients with minor trauma.10 As we all know, nausea, motion sickness and vomiting increase the discomfort of patients with traumatic injuries and cause further distress and anxiety. The act of vomiting may subsequently result in dehydration, aspiration of emesis and increased intracranial pressure, and its impact on vagal stimulation causes adverse changes in heart rate and blood pressure. A good example is the spine board-immobilized patient who is being transported for a possible cervical spine injury. If the patient becomes nauseated and begins to vomit, he risks aspiration and exacerbation of the spinal injury. Management of this patient generally requires additional personnel, thus taxing the resources of smaller EMS systems.
Oxygen is an inexpensive and widely available intervention that has been successful in the treatment of perioperative and postoperative N&V. Oxygen may be a simple method of reducing uncomfortable and potentially dangerous vomiting in EMS patients during transport.11
Ondansetron is a selective serotonin 5-HT3 receptor antagonist that works by blocking serotonin in the intestinal tract and CTZ (chemoreceptor trigger zone). It is available in solution for both IV and IM injection, as well as a rapid ODT (orally disintegrating tablet) and an oral solution. The standard dose for adults is 4 mg for IV or IM administration and 8 mg for the ODT. For pediatric patients (under 40 kilograms), the standard dose is 0.1 mg/kg up to 4 mg.
Ondansetron has very low incidence of adverse reactions, and the only contraindication is hypersensitivity. Zofran was originally developed to prevent nausea in chemotherapy patients, but its use has become more widespread in the emergency medicine setting since it became available as a generic. Most of the reported adverse effects have been attributed to chemotherapeutic agents taken by the patients.
Ondansetron was recently studied in the prehospital setting (Multnomah County, Oregon) for undifferentiated N&V in 952 EMS patients.12 It was shown to be "moderately" effective in decreasing N&V in a wide variety of patients with undifferentiated symptoms. The study also showed it to be safe for both adult and pediatric patients in the prehospital setting with no reported adverse effects.
Promethazine is a phenothiazine that works as an H1 antagonist. Although it was originally designed as an anti-psychotic, it is primarily used as an anti-emetic.
For EMS use, promethazine is supplied in 25 mg/ml Carpuject syringes, as well as 25 mg/ml and 50 mg/ml vials for injection. The standard adult dose of promethazine is 12.5–25 mg and can be administered IV, IM and rectally.