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ANALGESIA

An Analysis of Postoperative Epidural Analgesia Failure by Computed Tomography Epidurography

Cyrus Motamed, MD^*, Fayezi Farhat, MD^*, Francis Rémérand, MD^*, Jean Stéphanazzi, MD^*, Agnès Laplanche, MD, and Christian Jayr, MD^*

From the *Department of Anesthesia; and Department of Biostatistics; Institut Gustave Roussy, 39 rue Camille Desmoulins, 94805 Villejuif, Cedex, France.

Address correspondence and reprint requests to Cyrus Motamed, Service d'Anesthésie, Institut Gustave Roussy, 39 rue Camille Desmoulins, 94805 Villejuif, Cedex, France. Address e-mail to motamed{at}igr.fr.

Abstract

In this prospective study involving 125 patients, we analyzed epidural analgesia failure after major abdominal surgery using computed tomography (CT) epidurographies to compare the incidence of dislodgement of epidural catheters and leakage of solution from the epidural space between two groups of patients: patients with successful or failed epidural analgesia. Our hypothesis was that the incidence of dislodgement and leakage should be low when epidural analgesia is successful. A thoracic epidural catheter was inserted before general anesthesia and secured by subcutaneous tunneling. Bupivacaine (0.25%) was administered during surgery followed by continuous epidural analgesia with 0.125% bupivacaine (10 mL/h) and morphine (0.25 mg/h) for 48 h. Failure was defined as a visual analog scale pain score at rest more than 30 mm and/or interruption of epidural analgesia before 48 h for any reason. When failure was not due to unintentionally withdrawn, kinked catheters or adverse events (n = 11), a CT scan with contrast injection was performed. Control CT scans were also performed in patients with adequate analgesia (i.e., the success group). The incidence of failure was 24.8% (n = 31). CT scans in the failure group (n = 20) showed seven patients with catheters outside the epidural space, nine with normal distribution, one with unilateral spread, and three with leakage of solution outside the epidural space. In the success group, CT scans (n = 19) showed 11 patients with normal distribution, five with unilateral spread, and three with leakage. We conclude that the major cause of epidural analgesia failure was dislodgment of the catheter. CT scans were mostly useful for detecting leakage of injectate, which may be the early phase of dislodgment.

Epidural analgesia provides superior postoperative analgesia compared with parenteral opioids (1–4). Unfortunately, epidural analgesia is often associated with failures that may be difficult to resolve when the patient is in a surgical ward or during the night (5–9). Epidural analgesia failures may result from technical difficulties (10,11), insufficiencies or overdosing of local anesthetics (12,13), epidural septum or midline adhesions (14), placement of the epidural catheter through an intervertebral foramen or into the anterior epidural space (15) and problems related to the catheter itself (13,16–18). Mechanical problems with the catheter include the formation of kinks and knots, breakage, dislodgement, leakage, and disconnections (19–22). Dislodgement and leakage are common but are probably under-estimated, especially at the beginning of catheter displacement outside the epidural space (13,23).

We, therefore, conducted a prospective study to analyze epidural analgesia failure by CT epidurography after major abdominal surgery for cancer. Our hypothesis was that the incidence of dislodgement and leakage should be low when epidural analgesia is successful. Therefore, the main objective of our study was to compare the incidence of dislodgement of epidural catheters and leakage of liquid infusion out of the epidural space between two groups of patients: patients with successful or failed epidural analgesia.

METHODS

This prospective study was performed after approval of the IRB. Written informed consent was obtained from each patient. Inclusion criteria were patients undergoing major elective abdominal surgery for cancer via a midline, subcostal, or bisubcostal incision, 18–75 yr of age, ASA I–III and weight 50–100 kg. Exclusion criteria were patient refusal, contraindications to epidural analgesia (e.g., preoperative coagulopathy and localized or uncontrolled systemic infection) and technically impossible epidural catheter placement. Patients were premedicated with 0.5 mg alprazolam 1 h before surgery.

Epidural Catheter Placement and Management of Anesthesia
Before general anesthesia, an epidural catheter was placed by an attending anesthesiologist in a patient who was seated upright. After local anesthesia of the skin and the intervertebral tissue, the epidural space (T9–11) was identified using an 18-gauge Tuohy needle via a midline approach, and the loss-of-resistance technique with saline solution. An open-end, single-hole catheter (Portex Ltd®) was then advanced 4 cm into the epidural space and 5-cm subcutaneous tunneling was performed. The catheter was sutured and dressed with Tegaderm®. A 5-mL test dose of 2% lidocaine with epinephrine (5 µg/mL) was injected, and 0.25% bupivacaine (8–10 mL) with epinephrine (5 µg/mL) and fentanyl (0.1 mg) was injected. Bupivacaine was reinjected until the sensory block attained the T4 level. The extent of analgesia was determined by bilateral loss of sensation to ice. When the T4 level was obtained, general anesthesia was induced with etomidate, fentanyl, and neuromuscular blocking drugs, and was maintained with isoflurane and nitrous oxide in oxygen. Intraoperative analgesia was obtained by intermittent epidural injections of 0.25% bupivacaine approximately every 45 min. If hypotension occurred, a bolus of ephedrine (3–6 mg) was injected. Adequate intraoperative analgesia was evaluated according to hemodynamic stability (heart rate and arterial blood pressure within 25% of baseline) and fentanyl was administered IV when bupivacaine failed to provide adequate intraoperative analgesia. After completion of surgery, tracheal extubation was performed after reversal of the neuromuscular block.

Postoperative Pain Management
In the recovery room, a mixture of 0.125% bupivacaine (10 mL/h) and morphine (0.25 mg/h) was infused continuously into the epidural space. The infusion rate was reduced if motor block was above 0 according to a modified Bromage scale (0 = no motor block; 1 = inability to raise extended legs; 2 = inability to flex knees; 3 = inability to flex ankle joints) (2–4). Paracetamol (1 g/4 h) was injected IV on request when pain relief exceeded 30 mm at rest or when the patient complained of pain other than from abdominal origin (e.g., sore throat).

Abdominal pain was assessed at rest and while coughing using a 100-mm visual analog scale (VAS) (0 mm = no pain; 10 mm = worst pain imaginable) every 15 min in the recovery room and every 4 h thereafter. The spread of sensory block was determined by loss and return of cold sensation to ice. Patients were discharged from the recovery room when the pain score at rest was <30 mm.

On the surgical ward, the following variables were recorded every 4 h: level of sedation, VAS at rest and while coughing, extent of sensory blockade, presence of motor block as well as vital signs.

The following criteria signaled failure of analgesia:

• Interruption of epidural analgesia before 48 h for any reason.
  
• A VAS score that exceeded 30 mm at rest and persisted for 45 min after a rescue 5 mL epidural 0.125% bupivacaine injection and 1 g paracetamol IV were administered.
  

If the patient did not meet the failure criteria after the rescue dose, the infusion rate was then increased. The absence of a sensory level with a VAS not exceeding 30 mm was considered successful analgesia.

If an epidural analgesia failure occurred, a vertebral axial CT scan was acquired after injection of contrast medium via the catheter into the epidural space (5 mL iopamidol, 400 mg/mL). Image slices (2.5 and 5 mm thick) were acquired; two vertebrae above and below the site where the epidural catheter had been inserted. A tiny lead ball taped onto the skin marked the vertebral level where the catheter had been inserted for CT scan detection.

On the third postoperative day, before the removal of the epidural catheter, a CT scan was also performed in 19 patients in the success group (control group). These patients were selected as follows: after CT-epidurography in a patient in the failure group, CT-epidurography was performed in the next patient with successful epidural analgesia.

Both a radiologist and anesthesiologist who were blinded to the efficacy of epidural analgesia interpreted the CT scans. Three categories of images were defined: if contrast medium was present in the epidural space on at least one slice, it was "IN," (Figs. 1a and 2), if contrast medium was not found in the epidural space, it was "OUT" (Fig. 1b). When the contrast medium was "IN" and "OUT" on the same image, it was considered to be "LEAKING" out of the epidural space (Fig. 2).

View larger version (86K): [in this window] [in a new window]   Figure 1. (a) Left: Lower thoracic axial computed tomography scan after contrast injection through a catheter in a patient with a normally functioning catheter. (b) Right: Computed tomography scan after contrast injection through a catheter in a patient in whom epidural analgesia failed. The contrast medium accumulated in the subcutaneous tissue outside the epidural space.

View larger version (94K): [in this window] [in a new window]   Figure 2. Lower thoracic axial computed tomography scan depicting a posterior leak after contrast injection through a catheter in a patient in whom postoperative epidural analgesia failed.

The presence or absence of symmetrically surrounding contrast medium was recorded as well as its unilaterality or bilaterality.

In the failure group, all catheters that were displaced from the epidural space were leaking, exhibited total unilateral distribution, or were in the foramen were removed, and epidural analgesia was switched to parenteral morphine, but those with normal distribution inside the epidural space were maintained and the infusion rate was readjusted so as to provide efficient analgesia.

Statistical Analysis
The main objective of our study was to compare the incidence of epidural catheter dislodgement and leakage of liquid infusion out of the epidural space between two groups of patients: patients with successful versus failed epidural analgesia. As dislodgment and leakage may be responsible for 66% of epidural analgesia failure (13) and the incidence of dislodgement and leakage should be low when epidural analgesia is successful, we estimated that 40 patients would be required to demonstrate a difference of 50% in dislodgment and leakage on CT scan between groups with a 5% type I error and a 10% type II error using a two-tail test.

Preoperative characteristics in the two groups were compared using ² analysis for category variables and the Student's t-test for continuous variables. Analysis was performed using Statistical Analysis System (SAS, Cary, NC).

Univariate and multivariate analyses were performed to search for factors associated with epidural analgesia failure, such as demographic characteristics, type of surgery and incision, the physician performing the procedure, distance from the skin to the epidural space, extent of sensory block, presence of motor blockade, low arterial blood pressure, and asymmetrical sensory blockade.

Postoperative category variables were compared by ² analysis or Fisher's exact test when necessary.

Data were expressed as mean ± sd, or percentages. A P-value of <0.05 was considered statistically significant.

RESULTS

One-hundred-twenty-five patients were included in this study. No patients were excluded because of technical difficulties during catheter insertion.

Thirty-one patients (24.8%) were classified as failures while the others were classified as successes. Twenty CT scans were performed in the failure group. For the other 11 patients, CT scanning was not requested because the cause of analgesia failure was obvious: adverse events, unintentional catheter withdrawal, and difficult venous access in a patient who was able to ingest fluids. Nineteen CT scans were performed in the success group. Different CT images are shown in Figures 1and 2.

Demographic characteristics and sensory block information are detailed in Table 1 and Figure 3. There were no differences in the body mass index, the duration and type of surgery, or in the amount of intraoperative fentanyl administered between groups. Intraoperative ephedrine was administered more often in the success group (Table 1, P < 0.05).

View larger version (16K): [in this window] [in a new window]   Figure 3. Upper and lower left and right sensory blocks observed on both sides of patients assessed after insertion (test dose), in the postanesthesia care unit, at days 1 and 2. When sensory blockade was present, no differences were noted between groups. Patients with no sensory block were not included in the figure.

After multivariate analysis, only intraoperative ephedrine requirements were associated with successful epidural analgesia.

The Failure Group: (n = 31)
Interruption of Epidural Analgesia Despite Good Pain Relief (n = 2)
In one patient, morphine was removed from the infusion because of intense pruritus. Despite the presence of an adequate symmetrical sensory block, pain scores increased to 45 mm at 48 h. Epidural analgesia was therefore interrupted and subsequently replaced by parenteral morphine.

In another patient, epidural analgesia was stopped after 36 h because of a total, unilateral (right) block and concomitant prolonged hypotension, which was treated with ephedrine and intravascular volume replacement. Pain scores remained less than 10 mm on the VAS. However, a CT scan was performed before removal of the catheter. The epidural space was bilaterally opaque without any leakage, but right asymmetry (more opacity on the right side) was noted. No contrast medium was detected in the subdural or intradural spaces.

Interruption Unrelated to Epidural Analgesia (n = 2)
Two catheters were removed at 24 and 36 h. It was not possible to achieve peripheral venous access in one patient. However, oral fluid and per os medication were allowed because he had undergone a nephrectomy. The second patient expressed major anxiety concerning the epidural analgesia. Pain scores, however, were <30 mm in both cases.

Obvious Failure of Epidural Analgesia (n = 8)
Seven catheters were unintentionally completely withdrawn (1 in. the postanesthesia care unit (PACU), 4 during the first 24 h, and 2 between 24 and 48 postoperative hours). In one case, catheter kinking blocked the infusion on the first postoperative day and subsequent reinfusion was not possible. CT scans were not performed.

Analgesia Failure Without Any Obvious Cause (n = 19)
In these patients, the VAS score at rest exceeded 30 mm (see Methods section). The results of clinical assessments and CT scan findings are detailed in Table 2.

CT Scan Results
The Failure Group (n = 20 of 31)
In seven patients, no contrast medium was seen in the epidural space (OUT) (Fig. 1b). This difference with the control group was statistically significant (P < 0.01).

Contrast medium was strictly seen in the epidural space in 10 patients (IN) (Fig. 1a and Table 2) but there was no statistical difference between groups.

Contrast medium leakage was observed in three patients; in one case from the intervertebral foramen and in the other two from the posterior wall (Fig. 2 and Table 2).

The Success Group (n = 19 of 94)
In none of the success group patients was the catheter outside the epidural space (Table 2, P < 0.05). Three patients had leakage of contrast medium (in one case from the intervertebral foramen, in two cases from the posterior wall).

DISCUSSION

The main objective of this prospective study was to compare the incidence of dislodgement of epidural catheters and leakage of liquid infusion out of the epidural space between patients with failed epidural analgesia and those with efficient epidural analgesia in a large homogenous population of patients after major abdominal surgery for cancer.

The results of this observational study revealed a relatively frequent incidence (24.8%) of suboptimal epidural analgesia using bupivacaine and morphine. The major cause of failure of epidural analgesia was dislodgment of the epidural catheter (45%, P < 0.01). No other differences between the two groups were seen on CT scan. Eight percent (n = 10) of the total patient population had inadequate pain relief despite catheter placement in the epidural space. The incidence of perioperative hypotensive episodes was more frequent in the success group; however, it is difficult to compare the two groups as they were unequal in size (Table 1). Interestingly, 5/6 (83%) dislodgment events in the PACU did not result in perioperative hypotension, suggesting that the catheter had not functioned properly during surgery. Intraoperative hypotension may, therefore, be predictive of epidural analgesia efficacy.

We found that the spread of sensory block was often confirmed by the spread of contrast medium in the epidural space (Table 2), which is consistent with what has been reported (24). CT scans were therefore mostly useful for detecting leakage of contrast medium.

Other published reports cite dislodgment as a common cause of technical failure, with incidence rates comparable to those in our study. Studies on large patient populations (i.e., 1,014–5,628 patients) reported dislodgment rates of between 10% and 13% of all population (5,13,23). However, the proportion of dislodgement and leaking responsible for inadequate epidural analgesia may be as high as 66% (13) and 45% in our study. By contrast, less dislodgment (2%–3%) was reported in other studies (7,25,26), but the reason for these discrepancies among studies is unclear.

In our experience, dislodgment occurred early in the PACU or late in the surgical ward. Nonetheless, some studies have reported an increase in the failure rate according to the duration of epidural catheterization (27,28).

Lumbar epidural catheter tip position and the distribution of injectate assessed by CT scanography have been reported exclusively in patients receiving successful epidural anesthesia (29). In that study, CT was performed within 4 h of surgery and with an additional 10 mL injection of contrast medium. The author found that nonuniform distribution of injectate was common (at least 57% of cases) and compatible with uniform anesthesia (29) which is similar to our results since 42% of CT epidurography did not show uniform spread of contrast medium in our success group. Only 5 mL of contrast medium was injected in our study, which differs from that mentioned above (29). We used a volume mostly associated with postoperative analgesia conditions, larger volumes would simulate anesthesia conditions.

Interestingly, failures in the PACU were mainly due to dislodgment (Table 2, 6/7 failures, 86%). One explanation could be that when the catheter is properly placed in the epidural space, failed analgesia does not occur during the early postoperative phase because large amounts of local anesthetics are injected during and at the end of surgery. The second reason for analgesia failure was the dosing of the epidural medication with unilateral analgesia that may have been solved in some cases by increasing the infusion rate if the catheter is correctly placed in the epidural space (15,29). Epidurography has demonstrated that adequate analgesia with bilateral sensory blockade does not necessarily mean bilateral and symmetrical diffusion of contrast medium into the epidural space. Satisfactory analgesia can sometimes be maintained despite leakage outside the epidural space (Table 2). In the Hogan study (29), spread of injectate through the intervertebral foramina was seen in all patients.

Scott et al. (23) reported that catheter migration occurs when fluid accumulates under the clear adhesive dressing. Their group was able to minimize such migration and reduced dislodgment rates from 15% to 8% by placing a porous, nonclear dressing over the clear dressing. In our study, leakage was demonstrated in 15% of all analgesia failures on CT scans (Table 2, 6/39). We speculate that leakage from the posterior wall even though the catheter is lodged in the epidural space may be the sign of the early phase of complete dislodgment.

Burstal et al. (30) tried a subcutaneous tunneling technique that resulted in a significant reduction of backward and frontward movement of the epidural catheter, whereas Ballantyne et al. (13) tried various means of securing catheters. None of these methods improved the standard fixation method that involves securing the catheter with a clear, adhesive dressing, surrounded by paper or plastic tape. In another study, the Lockit® device was compared to the standard dressing with a clear adhesive and was found to be superior (31). The standard tunneling technique and the suture technique were compared in one study, but no differences were observed for dislodgment (32). Secondary dislodgement might not be due entirely to the fixation device; other mechanisms such as skin movement could also cause dislodgement.

In summary, the major cause of epidural analgesia failure in our study was catheter displacement. The second reason for analgesia failure was the dosing of the epidural medication that may partly be solved by a more adaptable infusion rate and/or a higher bolus dose in a patient-controlled epidural analgesia device.

ACKNOWLEDGMENTS

The authors thank Lorna Saint Ange for her patience and her editing.

Footnotes

Accepted for publication June 23, 2006.

REFERENCES

1. Kehlet H. Postoperative opioid sparing to hasten recovery: what are the issues? Anesthesiology 2005;102:1083–5.[Web of Science][Medline]
2. Jayr C, Beaussier M, Gustafsson U, et al. Continuous epidural infusion of ropivacaine for postoperative analgesia after major abdominal surgery: comparative study with i.v. PCA morphine. Br J Anaesth 1998;81:887–92.[Abstract/Free Full Text]
3. Jayr C, Thomas H, Rey A, et al. Postoperative pulmonary complications. Epidural analgesia using bupivacaine and opioids versus parenteral opioids. Anesthesiology 1993;78:666–76.[Web of Science][Medline]
4. Motamed C, Spencer A, Farhat F, et al. Postoperative hypoxaemia: continuous extradural infusion of bupivacaine and morphine vs. patient-controlled analgesia with intravenous morphine. Br J Anaesth 1998;80:742–7.[Abstract/Free Full Text]
5. Burstal R, Wegener F, Hayes C, Lantry G. Epidural analgesia: prospective audit of 1062 patients. Anaesth Intensive Care 1998;26:165–72.[Web of Science][Medline]
6. Andersen G, Rasmussen H, Rosenstock C, et al. Postoperative pain control by epidural analgesia after transabdominal surgery. Efficacy and problems encountered in daily routine. Acta Anaesthesiol Scand 2000;44:296–301.[Web of Science][Medline]
7. McLeod G, Davies H, Munnoch N, et al. Postoperative pain relief using thoracic epidural analgesia: outstanding success and disappointing failures. Anaesthesia 2001;56:75–81.[Web of Science][Medline]
8. Ready LB. Acute pain: lessons learned from 25,000 patients. Reg Anesth Pain Med 1999;24:499–505.[Web of Science][Medline]
9. Dolin SJ, Cashman JN, Bland JM. Effectiveness of acute postoperative pain management I. Evidence from published data. Br J Anaesth 2002;89:409–23.[Abstract/Free Full Text]
10. Lang SA, Korzeniewski P, Buie D, et al. Repeated failure of epidural analgesia: an association with epidural fat? Reg Anesth Pain Med 2002;27:494–500.[Web of Science][Medline]
11. Tolksdorf W, Thurigen W, Lutz H. [The influence of abnormal vertebral column on failure in epidural anaesthesia]. Prakt Anaesth 1977;12:413–8.[Medline]
12. Russell AW. Inadvertent epidural overdose. Anaesth Intensive Care 1994;22:501–2.[Web of Science][Medline]
13. Ballantyne JC, McKenna J, Ryder E. Epidural analgesia – experience of 5628 patients in a large teaching hospital derived through audit. Acute Pain 2003;4:89–97.
14. Gallart L, Blanco D, Samso E, Vidal F. Clinical and radiologic evidence of the epidural plica mediana dorsalis. Anesth Analg 1990;71:698–701.[Free Full Text]
15. Beilin Y, Zahn J, Bernstein HH, et al. Treatment of incomplete analgesia after placement of an epidural catheter and administration of local anesthetic for women in labor. Anesthesiology 1998;88:1502–6.[Web of Science][Medline]
16. Valentine SJ. Defects in epidural catheters. Anaesthesia 1988;43:1062 (letter).[Medline]
17. Smith S. Faulty markings on an epidural catheter. Anaesth Intensive Care 1998;26:594–5.[Web of Science][Medline]
18. Yau G, Ewart MC, Oh TE. Duplicate markings on an epidural catheter. Anaesthesia 1991;46:795–6.[Web of Science][Medline]
19. Stuart AL, McDavid AJ. Knotted epidural catheters. Reg Anesth 1996;21:606 (letter).[Web of Science][Medline]
20. Willens JS. Disconnected epidural catheter. Nursing 1991;21:33 (letter).
21. Asai T, Yamamoto K, Hirose T, et al. Breakage of epidural catheters: a comparison of an arrow reinforced catheter and other nonreinforced catheters. Anesth Analg 2001;92:246–8.[Abstract/Free Full Text]
22. Macfarlane J, Paech MJ. Another knotted epidural catheter. Anaesth Intensive Care 2002;30:240–3.[Web of Science][Medline]
23. Scott DA, Beilby DS, McClymont C. Postoperative analgesia using epidural infusions of fentanyl with bupivacaine. A prospective analysis of 1,014 patients. Anesthesiology 1995;83:727–37.[Web of Science][Medline]
24. Yokoyama M, Hanazaki M, Fujii H, et al. Correlation between the distribution of contrast medium and the extent of blockade during epidural anesthesia. Anesthesiology 2004;100:1504–10.[Web of Science][Medline]
25. Ready LB, Loper KA, Nessly M, Wild L. Postoperative epidural morphine is safe on surgical wards. Anesthesiology 1991;75:452–6.[Web of Science][Medline]
26. de Leon-Casasola OA, Parker B, et al. Postoperative epidural bupivacaine-morphine therapy. Experience with 4,227 surgical cancer patients. Anesthesiology 1994;81:368–75.[Web of Science][Medline]
27. Scott AM, Starling JR, Ruscher AE, et al. Thoracic versus lumbar epidural anesthesia's effect on pain control and ileus resolution after restorative proctocolectomy. Surgery 1996;120:688–95.[Web of Science][Medline]
28. Tsui BC, Gupta S, Finucane B. Confirmation of epidural catheter placement using nerve stimulation. Can J Anaesth 1998;45:640–4.[Web of Science][Medline]
29. Hogan Q. Epidural catheter tip position and distribution of injectate evaluated by computed tomography. Anesthesiology 1999;90:964–70.[Web of Science][Medline]
30. Burstal R, Wegener F, Hayes C, Lantry G. Subcutaneous tunnelling of epidural catheters for postoperative analgesia to prevent accidental dislodgement: a randomized controlled trial. Anaesth Intensive Care 1998;26:147–51.[Web of Science][Medline]
31. Clark MX, O'Hare K, Gorringe J, Oh T. The effect of the Lockit epidural catheter clamp on epidural migration: a controlled trial. Anaesthesia 2001;56:865–70.[Web of Science][Medline]
32. Chadwick VL, Jones M, Poulton B, Fleming BG. Epidural catheter migration: a comparison of tunnelling against a new technique of catheter fixation. Anaesth Intensive Care 2003;31:518–22.[Web of Science][Medline]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Motamed, C. Articles by Jayr, C. Search for Related Content PubMed PubMed Citation Articles by Motamed, C. Articles by Jayr, C. Related Collections Complications Regional Anesthesia