SLR - August 2018 - Elizabeth F. Neubauer
Reference: Baeriswyl M, Taffé P, Kirkham KR, Bathory I, Rancati V, Crevoisier X, Cherix S, Albrecht E. Comparison of Peripheral Nerve Blockade Characteristics Between Nondiabetic Patients and Patients Suffering from Diabetic Neuropathy: A Prospective Cohort Study. Anaesthesia. 2018 JuneScientific Literature Review
Reviewed By: Elizabeth F. Neubauer, DPM
Residency Program: Regions Hospital/HealthPartners Institute, St. Paul, MN
Podiatric Relevance: Many surgical procedures performed by podiatric physicians are aided by popliteal nerve blockade, and a large portion of these patients are living with diabetes. It has been recommended that a reduced dose of local anesthetic be used in this population due to presumed decreased sensitivity of the diabetic nerve secondary to chronic ischemic hypoxia and decreased perineural blood flow. It was hypothesized that patients with diabetes suffering from diabetic peripheral neuropathy would have increased block duration and decreased time to onset of the blockade. The study under review analyzed differences in block duration, time to onset and postoperative pain scores between diabetic patients with peripheral neuropathy and nondiabetic patients without peripheral neuropathy.
Methods: Thirty-three type II diabetic patients with peripheral neuropathy and 23 nondiabetic control patients scheduled for forefoot surgery were included in the study. Patients without diabetes and without neuropathy all had no loss of pinprick sensation and a tibial nerve cross-sectional area (CSA) less than 19.01 mm2. All patients received an ultrasound-guided popliteal nerve block with 30 mL of a 1:1 mixture of 1 percent lidocaine and 0.5 percent bupivacaine (both without epinephrine). The block was considered successful if the patient received a score of 0/2 for sensory nerve testing and 0/2 for motor function by one of the researchers. This assessment was performed five minutes after the initial administration of the local anesthetic and was repeated every five minutes for a total of 45 minutes. Following surgery, patients received a standard postoperative analgesic regimen consisting of 1,000 mg of acetaminophen every four hours and 5 mg of oxycodone every four hours as needed. The time elapsed before their first opioid request was documented. Patients were asked to rate their pain on a numeric scale from 0 to 10 on postoperative day 1. Patients were also contacted at one week and four weeks postoperatively to report on any other complications, such as hematoma, infection, persistent paresthesia or weakness.
Results: Patients with diabetic peripheral neuropathy had significantly longer median time to first opioid request compared to patients in the control group—1,440 and 710 minutes, respectively. By 24 hours postoperatively, only 30 percent of patients in the diabetic peripheral neuropathy (DPN) group had requested opioid pain medication, compared with 83 percent of patients in the control group. Patients in the DPN group also demonstrated a shorter sensory and motor onset times. Pain-related outcomes were also significantly lower in the DPN group with a mean pain score of 0/10 on postoperative day 1.
Conclusions: Results of this study suggest that a lower dose of local anesthetic may be necessary to adequately anesthetize patients with diabetic peripheral neuropathy. Authors describe several likely causes, including increased nerve sensitivity to the local anesthetic, impaired sensation at the surgical site and the presence of concurrent microangiopathy that would delay absorption of the local anesthetic. The study’s small sample size, however, does not permit new dosing recommendations because it does not assess the safety of varying doses and further research is needed in this area.