Effects of Propofol General Anesthesia on Olfactory Relearning

Parosmia and dysgeusia after intravenous propofol-based general anesthesia: A case report

Various drugs, including anesthetic agents, can cause parosmia in the perioperative period. There are reported cases of patients with alterations of smell and taste due to local anesthetics, nerve damage, or as a side effect of general anesthesia. We present a case of a 58-year-old male who developed parosmia and dysgeusia in the postoperative period after radical nephrectomy and inferior vena cava thrombectomy. The anesthetics used were fentanyl and propofol for general anesthesia and ropivacaine for epidural analgesia. Clinical examination did not reveal any pathology.

Effects of SSRI treatment on GABA and glutamate levels in an associative relearning paradigm

Impaired cognitive flexibility represents a widespread symptom in psychiatric disorders, including major depressive disorder (MDD), a disease, characterized by an imbalance of neuro-transmitter concentrations. While memory formation is mostly associated with glutamate, also gamma-Aminobutyric acid (GABA) and serotonin show attributions in a complex interplay between neurotransmitter systems. Treatment with selective serotonin reuptake inhibitors (SSRIs) does not solely affect the serotonergic system but shows downstream effects on GABA- and glutamatergic neurotransmission, potentially helping to restore cognitive function via neuroplastic effects. Hence, this study aims to elaborate the effects of associative relearning and SSRI treatment on GABAergic and glutamatergic function within and between five brain regions using magnetic resonance spectroscopy imaging (MRSI).

In this study, healthy subjects were randomized into four groups which underwent three weeks of an associative relearning paradigm, with or without emotional connotation, under SSRI (10mg escitalopram) or placebo administration. MRSI measurements, using a spiral-encoded, 3D-GABA-edited MEGA-LASER sequence at 3T, were performed on the first and last day of relearning. Mean GABA+/tCr (GABA+ = GABA + macromolecules; tCr = total creatine) and Glx/tCr (Glx = glutamate + glutamine) ratios were quantified in a ROI-based approach for the hippocampus, insula, putamen, pallidum and thalamus, using LCModel. A total of 66 subjects ((37 female, mean age ± SD = 25.4±4.7) for Glx/tCr and 58 subjects (32 female, mean age ± SD = 25.1±4.7) for GABA+/tCr were included in the final analysis.

A significant measurement by region and treatment (SSRI vs placebo) interaction on Glx/tCr ratios was found (p_cor=0.017), with post hoc tests confirming differential effects on hippocampus and thalamus (p_cor=0.046). Moreover, treatment by time comparison, for each ROI independently, showed a reduction of hippocampal Glx/tCr ratios after SSRI treatment (p_uncor=0.033). No significant treatment effects on GABA+/tCr ratios or effects of relearning condition on any neurotransmitter ratio could be found.

Here, we showed a significant SSRI- and relearning-driven interaction effect of hippocampal and thalamic Glx/tCr levels, suggesting differential behavior based on different serotonin transporter and receptor densities. Moreover, an indication for Glx/tCr adaptions in the hippocampus after three weeks of SSRI treatment could be revealed. Our findings are in line with animal studies reporting glutamate adaptions in the hippocampus following chronic SSRI intake. Due to the complex interplay of serotonin and hippocampal function, involving multiple serotonin receptor subtypes on glutamatergic cells and GABAergic interneurons, the interpretation of underlying neurobiological actions remains challenging.

A case of anosmia and hypogeusia as a complication of propofol

Anesthetics represent an uncommon cause of taste and smell disorders. We describe a case of anosmia and hypogeusia for 6 weeks after recovery from a uterine curettage operation in a 32-year-old woman. The case is unusual because propofol was the only anesthetic used during surgery and anesthesia. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed no abnormality. This case may highly suggest that propofol could induce smell and taste disorders.

Recent progress on the molecular pharmacology of propofol

The precise mechanism by which propofol enhances GABAergic transmission remains unclear, but much progress has been made regarding the underlying structural and dynamic mechanisms. Furthermore, it is now clear that propofol has additional molecular targets, many of which are functionally influenced at concentrations achieved clinically. Focusing primarily on molecular targets, this brief review attempts to summarize some of this recent progress while pointing out knowledge gaps and controversies. It is not intended to be comprehensive but rather to stimulate further thought, discussion, and study on the mechanisms by which propofol produces its pleiotropic effects.

Loss of Smell and Taste After General Anesthesia: A Case Report

This case report describes a patient, who lost the ability to smell and taste after receiving a propofol-based general anesthesia for a laparoscopic inguinal hernia repair. Immediately after the procedure, the patient had anosmia (loss of smell), ageusia (loss of taste), and light dysphagia. Assessment by an otorhinolaryngologist and the results of a magnetic resonance imaging could not clarify the pathology behind these symptoms. Although there are several plausible explanations for the patient's anosmia and ageusia (eg, cerebral infarcts, nerve damage, chronic sinusitis), the most likely explanation is an uncommon adverse drug reaction to the anesthetic agents used during the procedure.