CE Article: Nausea and Vomiting

      You are called for a 15-year-old boy who suddenly developed nausea and vomiting (N&V) after school. He feels better after vomiting, has normal vital signs, and his parents tell you they think it's just the stomach flu like his sister had a few weeks ago. Your partner tells you that you have another 9-1-1 call pending, so you suggest the parents have him checked if he is not better in a day and tell the engine crew to get the "AMA" form signed. Your next shift, you learn the child had surgery to remove a testicle after it infarcted.

   There are myriad causes for nausea and vomiting, some of which are benign and some deadly. EMS providers and patients often think of it as the "flu." While this is a possibility, it is our job to sort out the benign from the deadly and make sound management choices. This article will review recognition and management of illnesses with vomiting as a common chief complaint.

PATHOPHYSIOLOGY

   Few things in medicine elicit a visceral response as powerful as vomiting. The normal genesis for vomiting is complex (see Figure 1). Outside the brain, signals arise from afferent receptors (vagus and sympathetic nerves) in the gastrointestinal (GI) tract. These can be from direct irritation (infectious agents or choking) or distention (GI obstruction). Signals can also arise from non-GI sources. This is why patients with heart attacks, kidney stones and testicular torsion can vomit. Inside the brain is a chemoreceptor zone within the fourth ventricle. This region senses chemical imbalances such as hypoxia, nausea-inducing medications, toxins (e.g., ipecac, opiates and chemotherapy agents) and acidotic states. Finally, other areas of the brain, such as the cerebellum, via the vestibular system or the cortex itself, as in a stroke, may trigger nausea and vomiting.

   The vomiting center within the medulla acts as the incident commander for vomiting.¹ This area processes incoming stimuli from vomiting triggers outside and inside the brain. It is also thought to be the area where nausea is controlled. It then sends out signals to the vagus nerve (to the esophagus, stomach and duodenum), the phrenic nerve (to the diaphragm) and spinal nerves (to the intercostals and abdominal rectus).² These signals begin a series of coordinated events that lead to the coordinated and complex act of vomiting. See Figure 1.

MEDICATION CAUSES

   You are dispatched for a 78-year-old female whose chief complaint is N&V. She has crampy, diffuse abdominal pain and thinks it's the casino food she ate last night. She denies chest pain, dyspnea, fever or headache. She was recently started on Bactrim for a bladder infection. Her other medications include Cardizem, digoxin, simvastatin, calcium and Synthroid. The ED staff informs you later her digoxin level was elevated from an interaction with the Bactrim, and that's what triggered her vomiting.

   Numerous medications cause nausea and vomiting. The classic offenders are antibiotics, opiate analgesics (morphine, oxycodone, hydrocodone and codeine) and chemotherapy agents (see Table I). Other medications that can cause vomiting include oral contraceptives, antiretroviral/antiseizure prophylaxis, digoxin, metformin and lithium. It is important to review the patient's medications, especially any new ones or changes in dosing.

ABDOMINAL CAUSES

   A 42-year-old female calls 911 because of vomiting. It started yesterday, and now she has a fever and chills. As you elicit a "PQRST," she admits to having some colicky right upper quadrant pain, and had a similar episode last year that she was not evaluated for. She has orthostatic dizziness without syncope. She denies any past medical problems, alcohol use, chest pain, dyspnea or diarrhea. Her heart rate is 104, blood pressure 116/78, respiratory rate 28 and temperature 101°F. You start an IV, administer 50 micrograms of fentanyl and 4 milligrams of ondansetron (Zofran) and give her a liter of normal saline.