To explore the effect of intraoperative esketamine on pruritus in elderly patients undergoing elective general anesthesia for knee replacement surgery

Pruritus (itching) is one of the most common clinical conditions in the elderly population. Its etiology is complex, and the prevalence gradually increases with age. Pruritus in the elderly not only imposes a significant disease burden but also severely affects their sleep quality and daily life. This chronic, persistent itching often disrupts the skin barrier function, easily creating a vicious itch-scratch cycle, which leads to multiple damages to the patient's quality of life.Esketamine is the right-handed isomer of ketamine and is a non-competitive N-methyHD-aspartate (NMDA) receptor antagonist. It has the effects of rapid pain relief,rapid antidepressant action, sedation, and improvement of sleep. Relevant studies have shown that the NMDA receptor may play an importantrole in the transmission of non-histaminergic itching. However, there is still a lack of reports on whether it can relieve pruritus symptoms in elderly patients. This experiment intends to investigate the effect of intraoperative esketamine infusion on skin pruritus in elderly surgical patients.

Inclusion Criteria:

1. Meet the diagnostic criteria for senile pruritus:

   1. Aged ≥ 65 years old;
   2. Presenting with only skin pruritus without obvious primary skin lesions, with or without scratch-induced skin lesions;
   3. Daily or nearly daily pruritus lasting for more than 6 weeks.

2. Patients undergoing elective general anesthesia for orthopedic knee arthroplasty.

3. Patients aged ≥ 65 years old, with ASA physical status classification Ⅰ-Ⅲ; BMI ranging from 18 to 30 kg/m², with no restriction on gender.

4. Patients have fully understood the nature of this study, are capable of understanding and completing evaluation scales preoperatively, voluntarily participate in this trial, and sign the informed consent form.

Exclusion Criteria:

1. Those who are allergic to the pharmaceutical ingredients of this study or have an allergic constitution;
2. Those with a history of allergy to general anesthetics, opioids, or non-steroidal anti-inflammatory drugs;
3. Those with severe cognitive impairment, a history of neurological diseases, chronic pain, drug addiction, alcoholism, long-term opioid use, or administration of opioids within 48 hours before surgery;
4. Patients with ASA physical status classification Grade IV-V;
5. Those with severe coronary heart disease/arrhythmia/cardiac insufficiency, bronchial asthma, severe hypertension, severe hematopoietic system dysfunction, severe abnormal liver and kidney function, or significant electrolyte disorders;
6. Those with a history of gastrointestinal diseases (peptic ulcer, Crohn's disease, ulcerative colitis);
7. Those with respiratory insufficiency or respiratory failure;
8. Those with BMI < 18 kg/m² or BMI > 30 kg/m²;
9. Those with poor compliance who cannot complete the trial in accordance with the research protocol;
10. Those who have participated in other clinical drug trials within the past 4 weeks;
11. Those deemed unsuitable for enrollment by the researchers for any reason. -