Is propofol (intravenous anesthetic agent) safe to use in patients with anosmia (loss of smell)?

Propofol Use in Patients with Anosmia

Propofol can be safely used in patients with anosmia, but caution is warranted as there are rare case reports of propofol potentially causing or exacerbating smell disorders. While no specific contraindications exist regarding propofol use in patients with pre-existing anosmia, clinicians should be aware of the small risk of worsening or prolonging the condition.

Propofol and Olfactory Function

Evidence on Propofol and Anosmia

• Several case reports have documented anosmia following propofol-based general anesthesia:
  • A 60-year-old female developed altered smell and taste immediately after recovery from general anesthesia with fentanyl, propofol, and sevoflurane 1
  • A 32-year-old woman experienced anosmia and hypogeusia for 6 weeks after propofol anesthesia for uterine curettage 2
  • A patient lost smell and taste ability after propofol-based general anesthesia for laparoscopic inguinal hernia repair 3
  • A 58-year-old male developed parosmia and dysgeusia after general anesthesia with fentanyl and propofol 4

Mechanism and Risk Assessment

• The exact mechanism by which propofol might affect olfactory function is not well established
• These cases represent rare adverse events, not mentioned in major guidelines on propofol use
• No large-scale studies have established a definitive causal relationship between propofol and anosmia

Propofol Properties and Administration

Formulation and Pharmacology

• Propofol is formulated as an oil-in-water emulsion containing 1% propofol, 10% soybean oil, 2.25% glycerol, and 1.2% egg lecithin 5
• It acts primarily as a GABA receptor agonist with rapid onset (30-45 seconds) and short duration of action (4-8 minutes) 6
• Propofol produces sedation and amnesia at subhypnotic doses with minimal analgesic effect 6

Established Contraindications

• The only absolute contraindications for propofol are allergies to eggs, soy, or sulfites 5
• Propofol is not contraindicated in patients with sulfonamide allergy 6
• No specific contraindications exist regarding patients with pre-existing anosmia in any guidelines

Clinical Recommendations for Patients with Anosmia

Pre-Procedure Assessment

• Document the patient's baseline olfactory function before administering propofol
• Discuss the rare but reported risk of worsening anosmia with the patient as part of informed consent
• Consider alternative sedatives if the patient has significant concerns about potential worsening of anosmia

During Procedure

• Use the minimum effective dose of propofol to achieve the desired level of sedation
• Consider combination therapy with other sedatives to reduce the total propofol dose needed

Post-Procedure Monitoring

• Assess olfactory function after recovery from anesthesia
• If new or worsened anosmia occurs, consider olfactory retraining, which has shown benefit in some cases 1

Alternative Sedatives to Consider

• Midazolam: A water-soluble benzodiazepine with rapid onset and brief duration of action 6
• Benzodiazepine/opioid combinations: Provide both amnesia and analgesia but may cause more respiratory depression 6

Conclusion

While propofol has been implicated in rare cases of post-anesthesia anosmia, it remains a generally safe option for patients with pre-existing anosmia. The benefits of propofol's favorable pharmacokinetic profile often outweigh the small risk of olfactory complications. Document baseline olfactory function, obtain informed consent regarding the rare risk, and monitor for changes in smell function after the procedure.