Effects of Ankle Block on Postoperative Analgesia in Diabetic and Non-Diabetic Patients

Diabetes mellitus is a common chronic metabolic disease, and its increasing prevalence has led to a rise in diabetes-related complications. Diabetic neuropathy is one of the most frequent complications and is associated with structural and functional changes in peripheral nerves, including axonal degeneration and demyelination. These alterations may affect the onset, duration, and quality of peripheral nerve blocks.

Previous clinical and experimental studies have demonstrated that peripheral nerve blocks in patients with diabetic neuropathy may have longer duration and altered onset times compared to non-diabetic patients. Proposed mechanisms include changes in sodium and potassium channel function, delayed clearance of local anesthetics, and reduced microvascular absorption due to diabetic microangiopathy.

Ultrasound-guided ankle block is a commonly used regional anesthesia technique for foot and ankle surgeries, particularly in patients with diabetic foot ulcers, wound debridement, or minor amputations. It provides effective anesthesia and postoperative analgesia while avoiding the potential risks of general or neuraxial anesthesia in high-risk patients.

This study is designed as a single-center, prospective, observational study conducted at Fatih Sultan Mehmet Training and Research Hospital. Adult patients scheduled for lower extremity surgery under ultrasound-guided ankle block between January 2026 and October 2026 will be included after obtaining written informed consent. No additional interventions beyond routine clinical practice will be performed.

The ankle block will be administered preoperatively under ultrasound guidance by an experienced anesthesiologist using a standardized local anesthetic mixture. Sensory and motor block assessments will be performed using pinprick testing and motor function evaluation. Block onset times and block resolution times will be recorded.

Postoperative outcomes will include pain scores assessed using the Visual Analog Scale (VAS), total opioid consumption within the first 24 hours (expressed as morphine equivalents), time to first analgesic request, and the need for rescue analgesia. Patient and surgeon satisfaction will be evaluated using a 10-point numerical rating scale.

Patients will be categorized based on diabetes status and further subgrouped according to glycemic control using HbA1c levels (<7.5% and ≥7.5%). Outcomes will be compared between diabetic and non-diabetic patients and between glycemic control subgroups to evaluate the effect of diabetes and metabolic control on ankle block characteristics and postoperative analgesic outcomes.

The findings of this study are expected to contribute to a better understanding of regional anesthesia outcomes in diabetic patients and may help optimize anesthetic management strategies in this high-risk population.

Inclusion criteria

• Adults aged 18 years and older.
• Patients scheduled for lower extremity surgery under ultrasound-guided ankle block as part of routine clinical care.
• Patients able to provide written informed consent.
• Availability of complete perioperative data including blood glucose levels, -HbA1c values, pain scores, and postoperative analgesic consumption.

Exclusion criteria

• Refusal or inability to provide informed consent.
• Failure of ankle block requiring conversion to another anesthesia technique.
• Known coagulation disorders contraindicating peripheral nerve block.
• Active infection at the site of block application.
• Chronic opioid or analgesic use, chronic alcohol use, or substance abuse.
• History of diabetic ketoacidosis or hyperosmolar hyperglycemic state.
• Severe renal or hepatic insufficiency.
• Known allergy to local anesthetics such as lidocaine or bupivacaine.
• Inability to perform perioperative blood glucose monitoring.
• Cognitive impairment or psychiatric conditions interfering with study participation or data collection.