Abstract
Ultrasound-guided peripheral nerve blocks may be a good alternative in patients under antithrombotic drugs. We evaluated the efficacy of ultrasound-guided popliteal sciatic nerve block in patients undergoing lower extremity wound debridement of whom antithrombotic drugs could not be stopped. We focused on hemorrhagic complications related to sciatic nerve block. Wound care patients followed by Cardiovascular Surgery Department scheduled for lower extremity wound surgery were included in this prospective observational study. Data was collected between March 2021 and September 2022. All patient were under antithrombotic therapy and discontinuation of anticoagulant drugs were not possible. Single-insertion and multiple-injection sciatic nerve block at popliteal region was applied to all patients under ultrasound guidance. Primary outcome was the rate of hemorrhage. Secondary outcomes were block onset times, block success and postoperative analgesia times. Data of 105 patients was evaluated, 87 were male and 18 were female. Mean patient age was 61.92 ± 10.06, mean patient body mass index was 25.68 ± 6.33. All patients were under 1 or more antithrombotic drugs. Only one minor hematoma was detected by postoperative ultrasonography control in 1 patient. Hemorrhage complication rate was 1 of 105 (% 0.95, 95% CI, 0.00024–0.051). Overall block success rate was 99.05%. Mean block onset time was 16.27 ± 5.69 minutes. Mean postoperative analgesia time was 19.5 ± 11.22 hours. Sciatic nerve block under ultrasound guidance using in-plane technique was safe and provided sufficient surgical anesthesia and postoperative analgesia for lower extremity wound debridement surgery in patients on antithrombotic drugs.
Keywords: antithrombotic, lower extremity, popliteal, sciatic nerve block, ultrasound-guided, wound care
1. Introduction
General anesthesia may pose a high risk in patients undergoing surgical intervention for diabetic or vascular insufficiency-related foot wounds.[1] Furthermore, central neuraxial anesthesia may be contraindicated due to the anticoagulant/antiaggregant drugs that could not be interrupted in patients with serious cardiac comorbidity or peripheral venous disease.[2] Ultrasound-guided peripheral nerve blocks may be a good alternative in this patient group.
The sciatic nerve block is advocated as a safe procedure for patients on antithrombotic drugs who are scheduled for lower extremity surgery.[2] Sciatic nerve blocks are also advantageous in patients with severe comorbidities along with foot wounds, which preserve hemodynamic stability better than general anesthesia or a subarachnoid block.[3]
The evidence about the safety of peripheral nerve blocks in patients with ongoing antithrombotic therapy is limited to few case reports, case series, and retrospective cohort studies.[4] A recent review reports that the level of hemorrhage risk is varying and indicates the importance of further studies especially for some specific regional anesthesia procedures.[5] Moreover, the heterogeneity of the studies with different regional anesthesia techniques and different antithrombotic treatment regimens that are used in heterogenous patient groups, limits the quality of evidence.
In this study, we aimed to evaluate the efficacy and safety of ultrasound-guided popliteal sciatic nerve block for surgical anesthesia in patients undergoing foot wound operation who have ongoing anticoagulant/antiaggregant therapy. We hypothesized that sciatic nerve block might provide sufficient and safe surgical anesthesia without serious hemorrhagic complications in patients on anticoagulant/ antiaggregant drugs. Our primary aim was to identify the rate of possible hemorrhagic complications related to the sciatic block procedure. Our secondary aim was to evaluate the block characteristics, including block success rate, block onset times, and duration of postoperative analgesia in this patient group.
2. Methods
The study was designed as a prospective observational trial. The study was approved by the local Ethics Committee (Sakarya University Faculty of Medicine Ethics Board). Patient’s informed consents were obtained from all participants. Wound care patients with hypertension, diabetes mellitus, coronary artery disease, and peripheral vascular disease, having necrotic or infectious foot wounds, were included in the study. The patients were scheduled for lower extremity wound debridement operation by the Cardiovascular Surgery Department. Data of patients were recorded prospectively between March 2021 and September 2022. All patients were under anticoagulant therapy, and discontinuation of anticoagulant drugs was not possible. Demographic data of the patients and anticoagulant drugs used were recorded.
Ultrasound guided sciatic nerve block at popliteal region is applied for this patient group as a standard procedure in our clinic. The blocks are performed by experienced staff anesthesiologists of our clinic at a separate room allocated for the block procedure. The patients are under light sedation during the block procedures. We implemented a nontraumatic, echogenic needle (Sonoplex STIM, Pajunk, Geisingen, Germany) for the blocks. We used a single insertion and multiple injection method in which the needle is redirected when needed; to accomplish a homogenous spread around the nerve and to obtain a coin-sign ultrasound image (Fig. 1). Administration of local anesthetic covering the sciatic nerve circumferentially with ultrasound guidance improves the success of sciatic block without increasing the duration of block procedure, compared to a single injection technique.[6,7] The necessity of needle redirections was under the responsibility of the operator performing the block.
Figure 1.
Circumferential spread of local anesthetics around the sciatic nerve provided by multiple-injection technique in one of our patients. LA = local anesthetic spread.
Total number of needle redirections was recorded in each block procedure. We recorded total percent of local anesthetic distribution around the nerve after the block procedure in transverse and longitudinal ultrasound scans. We recorded ultrasound visibility of the sciatic nerve in a 5-scale categorization as: 5-Excellent, 4-Good, 3-Optimal, 2-Difficult, 1-Impossible.
We administered a 1:1 mixture of local anesthetic solution (15 mL 0.5% bupivacaine and 15 mL 2% lidocaine, totally 30 mL) for the blocks. Bleeding at the needle insertion point or blood aspiration during the block procedure was recorded.
After the surgical procedure, the needle insertion site and block region were scanned with ultrasound for signs of a hematoma. Ultrasound scans after the blocks were performed by a blinded researcher; to identify an early subcutaneous/intramuscular or perineural hematoma at the block area or near the sciatic nerve. The primary outcome was the rate of hemorrhagic complications related to the block procedure. Block characteristics were recorded prospectively, including block onset times, block success, and postoperative analgesia durations. Block success was defined as surgical anesthesia provided by the block in addition to light or deep sedation that preserves spontaneous respiration and does not require endotracheal intubation or placement of a supraglottic airway device. The procedure was considered a failed block if general anesthesia was required. We asked the postoperative analgesia time and pain scores at 24 and 48th hours by phone call. Data were collected and assessed by a blinded researcher.
2.1. Statistical methods
Descriptive statistical methods (mean, standard deviation, frequency) were implemented to evaluate the results of the study. We used the SPSS 20 (Statistical Package for Social Sciences) software (IBM Corp., Armonk) for the statistical assessment of the study data. Individual mean and standard deviations for each parameter were calculated from the values of all procedures in each subject. Exact binomial confidence intervals (95% CI) were calculated for hemorrhagic complication rate.
3. Results
A total of 111 patients were enrolled in the study in the determined study period. All patients were under 1 or more anticoagulant drugs. Totally, 6 patients were excluded from the study. Data of 105 patients were evaluated, 87 patients were male and 18 were female. Mean patient age was 61.92 ± 10.06, mean patient body mass index was 25.68 ± 6.33. Demographic characteristics are shown in Table 1. The flow diagram of the study is shown in Figure 2.
Table 1.
Demographic characteristics of patients. The values are given as numbers and mean ± standard deviation.
| Gender (male/female) | 87/18 |
|---|---|
| Age (yr) | 61.92 ± 10.06 |
| Weight (kg) | 77.14 ± 18.07 |
| Height (m) | 170.47 ± 8.46 |
| BMI (kg/m2) | 25.68 ± 6.33 |
| ASA I | 15 |
| ASA II | 85 |
| ASA III | 5 |
ASA = American Society of Anesthesiologists, BMI = body mass index.
Figure 2.
The flow-diagram of the study.
One of the excluded patients had diffuse cellulitis at his lower extremity, covering the needle insertion site, which made the block performance impossible. In 1 patient, we could not visualize the sciatic nerve clearly, and block performance was impossible. Thus, the procedure was considered a failed block. Three patients were excluded due to the interruption of the anticoagulant drugs preoperatively. One patient was excluded due to an inadequate anesthesia and requirement of general anesthesia. Sixty five patients were operated under a sole sciatic nerve block and 40 patients were operated under sciatic nerve block along with per-operative additional intravenous sedatives.
All patients were under 1 or more anticoagulant drugs. The drug types of 53 patients who received single antithrombotic therapy were as follows: 49 patients were on aspirin (46.6%), 2 patients on low molecular weight heparin (LMWH; 0.02%), 1 patient on clopidogrel (0.01%) and 1 patient on new oral anticoagulant drugs (rivaroxaban; 0.01%). The drug types of 47 patients who received dual antithrombotic therapy were as follows: 31 patients on aspirin + clopidogrel (29.5%), 11 patients on LMWH + clopidogrel (10.4%), 4 patients on LMWH + aspirin (0.04%), 1 patient on new oral anticoagulant (NOAC) + clopidogrel (0.01%). Of the patients 5 were using triple anticoagulant/antiaggregant therapy (LMWH + aspirin + clopidogrel; 0.05%). The usage of antithrombotic drugs is summarized in Table 2.
Table 2.
Types of anticoagulant drugs and usage of the patients.
| Type of anticoagulant drug | Number of patients (%) |
|---|---|
| Antiaggregants: Aspirin Clopidogrel |
49 (46.6%) 1 (0.01%) |
| Anticoagulants: LMWH Warfarin |
2 (0.02%) 0 (0 %) |
| Combination of antithrombotic drugs: Aspirin + clopidogrel LMWH + clopidogrel LMWH + aspirin LMWH + aspirin + clopidogrel NOAC + clopidogrel |
31 (29.5%) 11 (10.4%) 4 (0.04%) 5 (0.05%) 1 (0.01%) |
| NOACs (rivaroxaban) | 1 (0.01%) |
LMWH = low molecular weight heparin, NOACs = new oral anticoagulant drugs.
Overall block success rate was 99.05%. Mean block onset time was 16.27 ± 5.69 minutes. Mean operation time was 29.28 ± 12.9 minutes. Mean postoperative analgesia time was 19.5 ± 11.22 hours. Mean percent of local anesthetic distribution around the sciatic nerve was 88.80 ± 13.49 in transverse ultrasonography and 78.22 ± 17.91 in longitudinal ultrasonography scans. All block characteristics and ultrasound visualization scores are given in Table 3.
Table 3.
Data of block characteristics. Data were expressed as numbers, percentage and mean ± standard deviation.
| Mean block performance time (min) | 6.92 ± 3.18 |
|---|---|
| Mean number of needle redirections | 2.55 ± 0.95 |
| Mean percent of local anesthetic distribution Transverse axis Longitudinal axis |
88.8 ± 13.49 78.22 ± 17.91 |
| Mean block onset time (min) | 16.27 ± 5.69 |
| Sensorial block onset rate in 30 min | 96.19% |
| Motor block onset rate in 30 min | 79.04% |
| Mean operation time (min) | 29.28 ± 12.09 |
| Overall block success rate (%) | 99.05 % |
| Mean postoperative duration of analgesia (h) | 19.5 ± 11.22 |
| Ultrasound visibility Excellent Good Optimal Difficult Impossible |
5 (4%) 29 (27%) 34 (32%) 37 (34.9%) 1 (0.9%) |
We detected a hypoechoic perineural area during postoperative ultrasound scans in 1 patient, and we interpreted this as a minor perineural hematoma (Fig. 3). The patient was on triple antithrombotic drugs: aspirin 100 mg once a day, clopidogrel 75 mg once a day, and low molecular weight heparin 0.4 mL twice a day. The operation was completed without a complication and the patient’s postoperative follow-up showed no significant further complications, such as pain in the lower extremity or a neurologic deficit. The patient did not report swelling at the block site, numbness, paresthesia, or weakness at the related extremity during the 48-hour phone follow-up.
Figure 3.
The ultrasound image of the hematoma detected by ultrasound.
Blood was aspirated in 1 patient during the block, however the block procedure and the surgery completed without complication. No other hemorrhagic complications were detected in our patients associated with sciatic nerve block. There were no neurologic complications related to the blocks. Overall hemorrhage complication rate was 1 of 105 (% 0.95, 95% CI: 0.00024–0.051).
4. Discussion
This study showed that sciatic nerve block may be a safe alternative anesthesia technique in patients undergoing lower extremity wound debridement surgery that are under antithrombotic drugs. No major bleeding or an excessive hematoma occurred in our patient group.
Patients suffering from lower extremity vascular disorders are in the group of patients that use constant anticoagulant/antiaggregant drugs.[8] The routine anesthesia procedure is stopping these drugs by adopting international recommendations or institutional guidelines. The clinician should weigh the possibility a bleeding with against the risk of a thromboembolic event due to the decision of stopping antithrombotic drugs.[9] In some cases, antithrombotic drugs cannot be discontinued due to risk of thromboembolic complications.[2] Under these circumstances, a neuraxial block is contraindicated for preventing an epidural hematoma and alternative methods should be implemented. However, general anesthesia is also a high-risk procedure and may be hazardous due to the serious comorbid diseases. Peripheral nerve blocks are good alternatives in patients under antithrombotic therapy where the drugs could not be interrupted.
Safety of the sciatic nerve blocks in patients under antithrombotic drugs was not clear up to date. The multiple injection technique requires multiple-needle redirections to distribute local anesthetics around the nerve which may add risk to the procedure. However, ultrasound guided needle-in-plane technique ensures needle control in real-time to protect the anatomic structures from trauma.[10] We observed that multiple-needle redirections under ultrasound guidance might not increase the risk of bleeding even in patients under antithrombotic drugs. The sciatic nerve block at the popliteal level was categorized as a superficial block in the latest ESAIC/ESRA guidelines and performance was recommended as a safe procedure in anticoagulated patients.[2]
There is a small number of published studies about the safety of sciatic nerve blocks which are limited to case reports.[11–14] In these case reports, sciatic nerve block provided sufficient surgical anesthesia ; without any major hemorrhagic complication in patients receiving 1 or more antithrombotic drugs. The association of femoral and sciatic blocks has also been found as a good alternative to neuraxial blocks for the anesthesia of the lower extremity in patients on antithrombotic treatment.[2] In the case series of Martins et al[15], ultrasound guided femoral + sciatic nerve block was administerd for surgical anesthesia in 7 patients under single or multiple antithrombotic drugs. They reported efficient surgical anesthesia in lower extremity with no bleeding complications. Wardhan et al[16] evaluated the risk of bleeding in a large series of anticoagulated patients receiving femoral and gluteal or subgluteal sciatic perineural catheters for lower limb amputation. They reported only 1 case of hematoma near the femoral catheter among 146 patients (0.68%); who was on dual antithrombotic therapy (aspirin once a day and subcutaneous heparin 3 times a day). In the systematic review of Joubert et al[4], bleeding complications after peripheral nerve blocks were found as rare in patients receiving antiplatelet and/or anticoagulants. The overall bleeding incidence was reported 0.82%. However, data was based on case reports and 6 cohort studies including small populations.
Performance of the peripheral nerve blocks under ultrasound guidance reduced the risk of needle trauma as well as increased the success rate, especially when the in-plane technique is used.[17] We did not consider to add a saphenous block for the anesthesia of surgical procedures in our patients and a lack of saphenous nerve territory coverage was not observed. More than 1 block applications may also increase risk of bleeding which was not a necessary procedure in our patients. We implemented a single-insertion/ multiple-injection method to accomplish a higher success rate and a denser block for surgical anesthesia. In our study, overall success rate was high and the sensory block onset period was shorter than expected. This may be related to more than one reason. First, the application of the blocks under ultrasound guidance and the intend of a homogeneous distribution of local anesthetic solution around the nerve may have increased the effectiveness of the injections. Second reason may be that majority of our patients (92%) have diabetes. Approximately 50% of adults with diabetes have diabetic peripheral neuropathy; a complication that affects peripheral nerves throughout their lives.[18] Another reason may be that we use a relatively high volume of 30 mL and use a 1:1 ratio of lidocaine-bupivacaine mixture, which may show a faster onset of action.
Our study revealed a considerable variability in the usage of antithrombotic therapies, which makes the clinical judgment for the decision of regional anesthesia procedures challenging for the anesthetist. There are recommendations in the consensus guidelines of the American Society of Regional Anesthesia and Pain Medicine with the European Society of Anaesthesiology for the discontinuation of antithrombotic drugs and the permission of different regional anesthesia techniques in patients receiving anticoagulant/antiaggregant therapy.[2,19] In these guidelines, there are also warnings regarding the risks for the patients using a combination of some anticoagulant and antiaggregant drugs. However, the variability of antithrombotic therapies and the limited data for administering these drugs may still affect the safety of the patients receiving a peripheral nerve block.
The present study seems to be the first prospective observational trial that evaluated bleeding complications related to sciatic nerve blocks, and focusing on a homogenous patient group. The observational, nonrandomized characteristic of our study and lack of a control group may be considered as limitation. The heterogeneity of the used antithrombotic drugs is another limitation and may be a source of bias. Another limitation is that we did not evaluate perioperative bleeding from the surgical site however, this was not an objective of our study.
In conclusion, ultrasound-guided sciatic nerve block provided effective and safe anesthesia for lower extremity wound debridement operation in high-risk patients whose anticoagulant/antiaggregant therapy cannot be discontinued. The block success rate was high. No major bleeding was observed, except for one minor hematoma, which did not require treatment. The blocks provided sufficient postoperative analgesia where severe lower extremity pain was expected in the perioperative period of this patient group. Nonetheless, we recommend clinicians pay attention and follow up with the patients on antithrombotic drugs concerning hemorrhagic complications related to the block procedures.
Author contributions
Conceptualization: Ali Eman, Onur Balaban.
Data curation: Ali Eman, Onur Balaban, Özge Pekşen, Alper Erkin.
Formal analysis: Onur Balaban, Alper Erkin.
Investigation: Ali Eman, Özge Pekşen.
Project administration: Onur Balaban.
Resources: Özge Pekşen, Alper Erkin.
Validation: Ali Eman, Alper Erkin.
Writing – original draft: Ali Eman.
Writing – review & editing: Onur Balaban, Özge Pekşen, Alper Erkin.
Abbreviations:
- LMWH
- low molecular weight heparin
- NOAC
- new oral anticoagulant.
The study was approved by the Sakarya University Faculty of Medicine Ethics Committee (approval no: 2021-15133-144).
The authors have no funding and conflicts of interest to disclose.
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
How to cite this article: Eman A, Balaban O, Pekşen Ö, Erkin A. Ultrasound-guided popliteal sciatic nerve block for surgical anesthesia in wound care patients with ongoing anticoagulant/antiaggregant therapy: A single-center, prospective study. Medicine 2024;103:44(e40311).
Contributor Information
Ali Eman, Email: dralieman02@gmail.com.
Özge Pekşen, Email: ozgepeksen55@gmail.com.
Alper Erkin, Email: alperkin@hotmail.com.
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