(Food Poisoning, Gastroenteritis)
The patient seeks medical care 1 to 6 hours after eating because of severe nausea, vomiting, retching, and abdominal cramps that may progress later into diarrhea. He may have relatively minor symptoms or may appear very ill: pale, diaphoretic, tachycardic, orthostatic, perhaps complaining of paresthesias, or feeling as if he is “going to die.” Others may have similar symptoms from eating the same food. The physical examination, however, is reassuring. There is minimal abdominal tenderness, localized, if at all, to the epigastrium or to the rectus abdominis muscle (which is strained by the vomiting).
What To Do:
Obtain as much historical information as possible and completely examine the patient. Always consider pregnancy in women of childbearing age who present with vomiting. If there is any suspicion of a more serious underlying disorder (especially in the older patient), perform those tests needed to rule out myocardial infarction, perforated ulcer, aortic aneurysm, or any of the catastrophes that can present in a similar fashion. Always maintain a high index of suspicion for acute appendicitis or other surgical conditions in the patient who presents with abdominal pain and vomiting.
In the meantime, rapidly infuse 0.9% NaCl or Ringer lactate solution IV and observe the patient, doing repeated vital sign checks and physical examinations. Fluid and electrolyte replenishment is the mainstay of medical treatment. In adults who have the renal and cardiovascular reserve to handle rapid hydration, 1 to 2 L infused over an hour often provides dramatic improvement of all symptoms.
Older patients require more cautious rehydration and are more likely to require a comprehensive diagnostic workup.
The use of antiemetics for acute gastritis or gastroenteritis is somewhat controversial. With mild symptoms, there is probably no need to add this treatment and incur additional expense as well as risk the potential side effects of some of these drugs. For someone who is actively vomiting, however, these drugs can provide comfort and improve the process of rehydration.
In adults, ondansetron (Zofran), 4 mg IV is particularly advantageous, because it has minimal side effects. Alternatives include prochlorperazine (Compazine), 10 mg, which can also be given IV, along with diphenhydramine (Benadryl), 12.5 to 25 mg, to help reduce the incidence of extrapyramidal symptoms (such as dystonic reactions and akathisia). Metoclopramide (Reglan) can also be given (slowly to reduce risk of akathisia) in a dose of 10 mg IV.
During pregnancy, metoclopramide and ondansetron because they are classified as pregnancy category B drugs.
For children who are older than 6 months of age, ondansetron (Zofran), 0.15 mg/kg IV, can be given. Ondansetron (although very expensive under the brand name) can also be given as an oral disintegrating tablet (ODT) (which is reasonably priced as a generic). Half of a 4-mg tablet (2 mg) is an appropriate dose for an average 2-year-old (weighing 8 to 15 kg). The 4-mg tablet can be given to children weighing 16 to 30 kg, and 8 mg can be given to heavier children. Alternatively, metoclopramide (Reglan), 0.1 to 0.2 mg/kg IV, can be given.
If after 1 to 2 hours the pediatric patient is improving and beginning to tolerate oral fluids and has a benign repeat abdominal examination, discharge him with instructions to advance his diet over the next 24 hours, starting with an oral rehydration solution, such as the following recipe from the World Health Organization:
1 cup of orange juice
¾ tsp of table salt
1 tsp of baking soda
4 tbsp of sugar
4 cups of water
He should expect to be eating and feeling well in another 1 or 2 days.
Children can be rehydrated using the techniques described in Chapter 68.
If symptoms resolve more slowly, discharge the patient with a single dose of an antiemetic as described earlier.
Adults with abdominal cramping may be helped with a dose of the antispasmodic dicyclomine (Bentyl), 20 mg qid PO/IM.
Patients should always be encouraged to return for further evaluation and treatment if their symptoms return or if pain continues or worsens.
If hypotension or other significant signs or symptoms persist, if the patient cannot tolerate parenteral rehydration, or if he cannot resume oral intake, he may have to be admitted to the hospital for further evaluation and treatment.
What Not To Do:
Do not presume food poisoning without a good history for it.
Do not overlook pregnancy as a possible cause of vomiting.
Do not assign blame for the cause of any suspected food poisoning. The information available is almost always circumstantial until public health authorities complete their investigation.
Do not skimp on IV fluids. Monitor vital signs and urinary output and generously replace fluid losses.
Do not pursue expensive laboratory investigations for straightforward cases. Diagnostic tests usually are unnecessary in an otherwise healthy patient who is stable and whose history and physical examination are consistent with acute gastroenteritis.
▪ Whenever possible, the cause of vomiting should be ascertained and specific treatment for an underlying cause initiated—particularly when emergent conditions, such as central nervous system (CNS) lesions, myocardial infarction, acute abdomen, bowel obstruction, endocrine/metabolic disorders, are suspected. As mentioned above, always consider pregnancy in women of childbearing age who present with vomiting. Consider bowel obstruction if there is distention and pain on abdominal palpation. Feculent vomiting is concerning for large bowel obstruction. Patients may present with a chief complaint of vomiting and, on exam, have nystagmus; these patients should be evaluated and treated for vertigo. Eating disorders must also be considered. In the diabetic, gastroparesis may be the cause. Frequent use of marijuana may be associated with recurrent vomiting as well. Many prescription drugs may cause nausea and vomiting, and these will be cured with cessation of the drug; so, take a good medication history, asking about both prescribed and nonprescribed drugs. However, in most cases of simple, uncomplicated vomiting with gastroenteritis or foodborne illness, the precise cause need not be determined, and therefore symptomatic treatment is all that is required.
▪ Many of the symptoms accompanying any gastroenteritis seem to be related to electrolyte disturbances and dehydration, which can be substantial even in the absence of copious vomiting and diarrhea. Lactated Ringer solution is considered the choice for IV rehydration by many clinicians, because it approximates normal serum electrolytes and can be infused rapidly. Lactated Ringer approximately replaces the electrolytes lost in diarrhea, although normal saline has more of the chloride lost by vomiting. Both work quite well in the acute setting for either diarrhea or vomiting or a combination of the two.
▪ Most food items that cause foodborne illness are raw or undercooked foods of animal origin, such as meat, milk, eggs, cheese, fish, or shellfish. A clearly implicated food source may give a clue to the cause: shellfish suggesting Vibrio parahaemolyticus; rice suggesting Bacillus cereus; meat or eggs suggesting staphylococci, Campylobacter organisms, clostridia, salmonellae, shigellae, enteropathic Escherichia coli, or Yersinia sp.
▪ Vibrio bacteria, so named because they are so motile that they appear to vibrate, are most common in states bordering the Gulf of Mexico. These flagellated bacteria inhabit marine environments and can cause gastroenteritis, wound infections, and septicemia. V. vulnificus infection more often follows ingestion of raw or undercooked oysters, and V. parahaemolyticus infection is more likely to be associated with eating shrimp or crabs. Fever, chills, and headache, in addition to the gastrointestinal symptoms, are common manifestations of this infection. Patients with liver disease, impaired immune systems, and diabetes are at increased risk for fulminant infections.
▪ B. cereus causes an acute emetic syndrome, most commonly within 1 to 6 hours of ingesting fried rice obtained from a Chinese restaurant. B. cereus also causes a less common diarrheal syndrome with an onset 8 to 16 hours after ingestion. There is no role for antimicrobial therapy in the treatment of these syndromes.
▪ The most common food poisoning seen in most emergency departments is caused by the heat-stable toxin of staphylococci, which is introduced into food from infections in handlers and grows when the food sits warm. Foods that are frequently incriminated in staphylococcal food poisoning include meat and meat products; poultry and egg products; salads, such as egg, tuna, chicken, potato, and macaroni; bakery products, such as cream-filled pastries and cream pies; and milk and dairy products. Foods containing the toxins usually look and taste normal. Sudden onset of nausea, vomiting, abdominal pain, and watery diarrhea usually occurs 30 minutes to 8 hours after eating contaminated food. Because these symptoms are toxin mediated, antibiotics are not indicated.
▪ Chemical toxins have a similar presentation, but the onset of symptoms may be more immediate. Heavy metal poisoning is a rare cause of gastroenteritis and results from gastric irritation caused by copper, zinc, iron, tin, or cadmium. Accidental ingestion of these substances can occur if a person drinks an acidic or carbonated beverage that came into contact with a metal container or metal tubing. Common symptoms include nausea, vomiting, diarrhea, cramps, and, with copper and tin, a metallic taste that usually occurs 5 to 60 minutes after ingestion. For chemical or heavy metal poisoning, consult with a poison control center for advice on appropriate treatment (see Appendix G).
▪ Other bacterial food poisonings usually present with onset of symptoms later than 1 to 6 hours after eating, less nausea and vomiting, more cramping and diarrhea, and longer courses. See Chapter 68 for management of these predominantly diarrheal illnesses.
▪ Seafood ingestion syndromes, such as ciguatera poisoning and scombroid poisoning, can be distinguished from other forms of foodborne illnesses by symptoms such as perioral numbness and reversal of temperature sensation (ciguatera poisoning) or flushing and warmth (scombroid poisoning). Grouper, red snapper, amberjack, sea bass, and barracuda are the most common species of fish implicated in ciguatera poisoning.
▪ Ciguatoxin is a naturally occurring toxin found in a dinoflagellate (Gambierdiscus toxicus) that is consumed by fish. The ciguatoxins become concentrated in these larger fish and are unaffected by normal cooking. Symptoms appear about 5 hours (2 to 30 hours) after eating toxic fish. The first manifestations of poisoning include abdominal pain, nausea, vomiting, painful defecation, and diarrhea. Pruritus and paresthesias, described as uncomfortable tingling sensations, most often develop in the extremities and mouth and, along with a peculiar sensory reversal of hot and cold, are the symptomatic hallmarks of ciguatera poisoning. Pain, paresthesias, pruritus, and weakness may persist for several weeks, and chronic symptoms have been reported. Successful management of these neurologic symptoms with IV mannitol has been described in the past, but a double-blind randomized trial of mannitol therapy in ciguatera fish poisoning did not support single-dose mannitol as standard treatment. Pruritus can be treated with antihistamines, such as hydroxyzine (Atarax, Vistaril), 25 mg 3 to 4 times daily. Treat neuropathic symptoms with gabapentin (Neurontin), 100 mg qd to tid, titrating up to 800 to 1200 mg tid as needed. The patient should be instructed to avoid all fish, alcohol, caffeine, and nuts for 6 months, because these items may precipitate a recurrence of symptoms.
▪ Scombroid poisoning is caused by improper refrigeration of Scombroidea (bluefin and yellowfin tuna, skipjack, albacore, marlin, and mackerel). Nonscombroid fish, such as mahi-mahi, amberjack, and herring may also produce this syndrome. Bacterial growth and breakdown of the fish flesh result in the production of histamine and the production of a histamine-like toxin, saurine, neither of which are affected by normal cooking temperatures. These fish either may have a bitter, peppery, or metallic taste or may taste perfectly normal. Symptoms consist of a histamine-like reaction that includes flushing, rash, and hot sensations of the skin and mouth, along with headache, anxiety, dizziness, nausea, vomiting, and diarrhea occurring approximately 10 to 30 minutes after ingestion. Antihistamines, such as hydroxyzine (Atarax, Vistaril), 25 mg qd to qid, are effective, along with H2 blockers, such as ranitidine (Zantac), 150 mg bid, and, in more severe cases, methylprednisolone (Solu-Medrol), 125 mg IV. Symptoms are self-limited, but medications may be required for several days.
▪ When symptoms are severe with large ingestions of either form of fish poisoning, patients should also be given activated charcoal AD (Superchar), 1 g/kg orally.
▪ Whenever someone suffers any gastrointestinal upset, it is natural, if not instinctive, to implicate the last food eaten. When the index of suspicion for a foodborne illness is high, this information should be reported to the local health department for definitive diagnosis and epidemiologic management.