Gender differences in the antianhedonic effects of repeated ketamine infusions in patients with depression

Effect of Ketamine on the Bispectral Index, Spectral Edge Frequency, and Surgical Pleth Index During Propofol-Remifentanil Anesthesia: An Observational Prospective Trial

BACKGROUND

Ketamine administration during stable propofol anesthesia is known to be associated with an increase in bispectral index (BIS) but a "deepening" in the level of hypnosis. This study aimed to evaluate the association between the effect-site concentration of ketamine (CeK) and 2 electroencephalogram (EEG)-derived parameters, the BIS and spectral edge frequency (SEF95), after the administration of a ketamine bolus. Secondary aims included investigating the BIS and SEF95 variations with time and changes in the surgical pleth index (SPI).

METHODS

We conducted an observational, prospective, single-center study analyzing intraoperative data from 14 adult female patients undergoing breast oncologic surgery. During stable propofol-remifentanil target-controlled infusion (TCI) anesthesia, a ketamine analgesic bolus was delivered with the target CeK set to 1 μg.mL-1 (Domino model) corresponding to a dose of 0.57 mg.kg-1 (interquartile range [IQR] 0.56-0.57 mg.kg-1). Once the CeK reached a value of 1 μg.mL-1, the target CeK was set to 0 μg.mL-1. We determined the median BIS, SEF95, and SPI trends with time and as a function of the modeled CeK.

RESULTS

BIS and SEF95 showed no significant change from when ketamine was administered to when CeK=1 μg.mL-1, but a significant increase was observed at lower CeKs. The maximum BIS was reached at 16.0 minutes [10.2-22.7 minutes] after CeK=1 μg.mL-1, at CeK=0.22 μg.mL-1 [0.12-0.41 μg.mL-1]. The peak SEF95 value was observed at 10.0 minutes [8.62-14.1 minutes] after CeK=1 μg.mL-1, at CeK=0.43 μg.mL-1 [0.25-0.50 μg.mL-1]. No significant association was found between CeK and the registered SPI values.

CONCLUSIONS

Our results show that BIS and SEF95, but not SPI, follow a CeK-dependent trend after administering a ketamine bolus. Interestingly, their peak values were not reached at CeK=1 μg.mL-1, but after several minutes after the drug infusion at CeKs in the 0.2 to 0.5 μg.mL-1 range. This may be explained by the specific pharmacodynamics of ketamine and its varying effects at different concentrations, as well as by the time delay associated with the calculation of the BIS.

An Update on the Efficacy of Single and Serial Intravenous Ketamine Infusions and Esketamine for Bipolar Depression: A Systematic Review and Meta-Analysis

Ketamine has shown rapid antidepressant and anti-suicidal effects in treatment-resistant depression (TRD) with single and serial intravenous (IV) infusions, but the effectiveness for depressive episodes of bipolar disorder is less clear. We conducted an updated systematic review and meta-analysis to appraise the current evidence on the efficacy and tolerability of ketamine/esketamine in bipolar depression. A search was conducted to identify randomized controlled trials (RCTs) and non-randomized studies examining single or multiple infusions of ketamine or esketamine treatments. A total of 2657 articles were screened; 11 studies were included in the systematic review of which 7 studies were included in the meta-analysis (five non-randomized, N = 159; two RCTs, N = 33) with a mean age of 42.58 ± 13.1 years and 54.5% females. Pooled analysis from two RCTs showed a significant improvement in depression symptoms measured with MADRS after receiving a single infusion of ketamine (1-day WMD = -11.07; and 2 days WMD = -12.03). Non-randomized studies showed significant response (53%, p < 0.001) and remission rates (38%, p < 0.001) at the study endpoint. The response (54% vs. 55%) and remission (30% vs. 40%) rates for single versus serial ketamine infusion studies were similar. The affective switch rate in the included studies approximated 2.4%. Esketamine data for bipolar depression are limited, based on non-randomized, small sample-sized studies. Further studies with larger sample sizes are required to strengthen the evidence.

A comparison of the antianhedonic effects of repeated ketamine infusions in melancholic and non-melancholic depression

OBJECTIVES

Melancholic depression may respond differently to certain treatments. The aim of this study was to compare the antianhedonic effects of six intravenous injections of 0.5 mg/kg ketamine in patients with melancholic and non-melancholic depression, which remain largely unknown.

METHODS

Individuals experiencing melancholic (n = 30) and non-melancholic (n = 105) depression were recruited and assessed for anhedonic symptoms using the Montgomery-Åsberg Depression Rating Scale (MADRS). The presence of melancholic depression was measured with the depression scale items at baseline based on DSM-5 criteria.

RESULTS

A total of 30 (22.2%) patients with depression fulfilled the DSM-5 criteria for melancholic depression. Patients with melancholic depression had a non-significant lower antianhedonic response (43.3 vs. 50.5%, t = 0.5, p > 0.05) and remission (20.0 vs. 21.0%, t = 0.01, p > 0.05) to repeated-dose ketamine infusions than those with non-melancholic depression. The melancholic group had significantly lower MADRS anhedonia subscale scores than the non-melancholic group at day 26 (p < 0.05).

CONCLUSION

After six ketamine infusions, the improvement of anhedonic symptoms was found in both patients with melancholic and non-melancholic depression, and the efficacy was similar in both groups.