How should I manage a patient with a one‑week history of a soapy/acetone‑like odor, nausea and vomiting, and normal complete blood count, basic metabolic panel, liver function tests, thyroid panel, and lipase?

Management of Soapy Smell with Nausea and Vomiting

This patient requires immediate evaluation for olfactory hallucination (phantosmia) as the primary diagnosis, with symptomatic management of nausea and vomiting using ondansetron, while ruling out metabolic causes including diabetic ketoacidosis despite normal glucose.

Immediate Diagnostic Considerations

Olfactory Dysfunction Assessment

• The complaint of a persistent "soapy smell" for one week represents phantosmia—perception of odor without external stimulus—which requires evaluation for underlying neurological, infectious, or psychiatric etiologies 1.
• Phantosmia differs from parosmia (distorted perception of actual odors) and can be triggered by viral infections, traumatic brain injury, psychiatric disorders, or medications 1.
• Post-viral olfactory dysfunction, particularly following COVID-19 or other respiratory infections, is a leading cause of qualitative smell disorders 1.

Metabolic Evaluation

• Despite the normal glucose of 95 mg/dL, acetone production in early or intermittent ketosis can cause unusual odor perceptions and may be detected before frank hyperglycemia develops 2.
• Acetone, a ketone body, creates a characteristic fruity or chemical odor that can be perceived as "soapy" and is converted to isopropanol, which may trigger olfactory symptoms 2.
• The normal basic metabolic panel, liver function tests, and thyroid function effectively rule out common metabolic causes of nausea including thyrotoxicosis, hepatic dysfunction, and electrolyte disturbances 3.

Symptomatic Management of Nausea and Vomiting

Antiemetic Therapy

• Administer ondansetron 4 mg IV over 2-5 minutes to facilitate oral intake and prevent dehydration 4, 5.
• Ondansetron is significantly more effective than placebo for controlling nausea and vomiting in adults, with proven efficacy in preventing further emetic episodes 5.

Hydration Assessment and Management

• Evaluate for signs of dehydration including tachycardia, orthostatic hypotension, decreased skin turgor, dry mucous membranes, and decreased urine output 4, 6.
• The normal BUN/creatinine ratio of 11 and creatinine of 0.95 mg/dL suggest adequate hydration status currently 4.
• If mild dehydration is present, initiate oral rehydration solution (ORS) containing sodium 90 mM, potassium 20 mM, chloride 80 mM, bicarbonate 30 mM, and glucose 111 mM 4.
• Replace ongoing losses with 10 mL/kg ORS for each episode of vomiting 4.

Additional Diagnostic Workup Required

Stool Studies

• Although the patient's presentation is primarily olfactory with secondary nausea, if diarrhea develops, obtain stool studies for bacterial pathogens and C. difficile toxin before initiating antimotility agents 4, 6, 7.
• The normal WBC of 7.1 x10³/μL makes inflammatory or infectious diarrhea less likely, but does not exclude it 3, 4.

Neurological Evaluation

• Phantosmia requires determination of etiology through focused history regarding recent viral infections, head trauma, medication changes, and psychiatric symptoms 1.
• Consider brain imaging (MRI) if phantosmia persists beyond 2-4 weeks, is associated with other neurological symptoms, or does not respond to symptomatic treatment 1.

Dietary Modifications

• Eliminate lactose-containing products, alcohol, high-osmolar dietary supplements, spices, coffee, and other potential triggers immediately 4, 7.
• Recommend frequent small meals rather than large portions to minimize nausea 6.
• Resume normal diet once nausea resolves and oral intake is tolerated 4.

Critical Monitoring Parameters

• Instruct the patient to report fever >100.4°F (38°C), bloody stools, severe abdominal pain, inability to tolerate oral fluids, dizziness upon standing, decreased urination, or confusion 4, 6, 7.
• Monitor for progression of phantosmia or development of additional neurological symptoms including headache, visual changes, or altered mental status 1.
• Track frequency and severity of nausea and vomiting episodes daily 6.

When to Escalate Care

Hospitalization Criteria

• Admit if the patient develops severe dehydration despite oral rehydration attempts, hemodynamic instability, inability to tolerate oral fluids, signs of acute kidney injury (rising creatinine), or signs of sepsis 4, 6, 7.
• The slightly elevated RDW of 15.6% and platelets of 453 x10³/μL warrant monitoring but do not currently indicate severe pathology 3.

Common Pitfalls to Avoid

• Do not dismiss unusual odor complaints as purely psychiatric without ruling out metabolic causes, particularly early ketoacidosis which can present with normal glucose 2.
• Do not initiate loperamide or other antimotility agents if fever, bloody stools, or suspected infectious etiology develops 4, 6, 7.
• Do not assume phantosmia is benign—it can be an early sign of neurological disease or post-viral syndrome requiring specific treatment 1.
• The normal lipase of 20 U/L effectively excludes acute pancreatitis as a cause of nausea 3.

Treatment Algorithm for Phantosmia

• If phantosmia persists beyond symptomatic management, consider modified olfactory training (MOT) which has proven effective for post-infectious olfactory disorders including COVID-19-induced parosmia 1.
• Treatment duration for qualitative olfactory disorders varies widely, making it essential to provide ongoing support rather than focusing solely on complete resolution 1.
• Symptomatic relief takes priority while determining the underlying etiology through systematic evaluation 1.