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BJA Advance Access originally published online on October 22, 2008
British Journal of Anaesthesia 2008 101(6):832-840; doi:10.1093/bja/aen300
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© The Board of Management and Trustees of the British Journal of Anaesthesia 2008. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

Effectiveness and safety of postoperative pain management: a survey of 18 925 consecutive patients between 1998 and 2006 (2nd revision): a database analysis of prospectively raised data{dagger}

D. M. Pöpping*, P. K. Zahn, H. K. Van Aken, B. Dasch, R. Boche and E. M. Pogatzki-Zahn

Department of Anaesthesiology and Intensive Care, University Hospital Münster, D-48149 Münster, Germany

* Corresponding author. E-mail: poppind{at}uni-muenster.de

Accepted for publication August 17, 2008.


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgement
 References
 
Background: Approximately 30–80% of postoperative patients complain about moderate to severe post-surgical pain, indicating that postoperative pain treatment is still a problem.

Methods: We analysed prospectively collected data on patients in a university hospital receiving systemic and epidural patient-controlled analgesia and continuous peripheral nerve block (CPNB) documented by the acute pain service team in a computer-based system.

Results: Of 18 925 patients visited in the postoperative period between 1998 and 2006, 14 223 patients received patient-controlled epidural analgesia (PCEA), 1591 i.v. patient-controlled analgesia (IV-PCA), 1737 continuous brachial plexus block, and 1374 continuous femoral/sciatic nerve block. Mean dynamic and resting pain scores (VAS 0–100) were significantly lower for peripheral or neuroaxial regional analgesia compared with patient-controlled systemic opioid analgesia (P<0.05). The risk of a symptomatic spinal mass lesion including epidural haematoma (0.02%; 1:4741) or epidural abscess (0.014%; 1:7142) after PCEA was 1:2857 (0.04%). Neurological complications after CPNB occurred in two patients who received interscalene brachial plexus block.

Conclusions: We demonstrated that PCEA, IV-PCA, and CPNB are safe and efficient. Although all of these treatment strategies provide effective analgesia, PCEA and CPNB provided superior pain relief compared with IV-PCA. We demonstrated that serious complications of analgesic techniques are rare but possibly disastrous necessitating a close supervision by an acute pain service. We found a low rate of adverse effects including hypotension and motor impairment and a low incidence of epidural haematoma for thoracic PCEA compared with lumbar PCEA.

Keywords: anaesthetic techniques, regional; complications, neurological; epidural; pain, postoperative; safety


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Conclusion
 Acknowledgement
 References
 
Good postoperative pain control is an important part of adequate postoperative care.1 However, 30–80% of postoperative patients complain about moderate to severe post-surgical pain.2 Inadequate postoperative pain relief may delay recovery, lead to a prolonged hospital stay, and increase medical costs.3 Patient-controlled i.v. or regional analgesia compared with conventional on-demand analgesia improves postoperative pain relief and may decrease hospital length of stay by enhancing patients' recovery.4–6 Similarly, continuous peripheral nerve blocks (CPNB) provide superior postoperative analgesia and fewer opioid-related side-effects compared with opioid analgesia—regardless of catheter location.7 However, i.v. patient-controlled analgesia (IV-PCA) and peripheral and neuroaxial catheter techniques are associated with risks, although the incidence of complications still remains a matter of debate.8–10

Our institutional computer-based documentation system contains prospectively collected data on nearly 20 000 patients who were treated with patient-controlled epidural analgesia (PCEA), CPNB, and IV-PCA with opioids from January 1998 to March 2006. The aim of the present study was to compare the quality of pain relief between different techniques as measured by the VAS score and to compare the incidence of major complications between these techniques. Furthermore, we evaluated the incidence of adverse effects including nausea and vomiting for each of these analgesia regimens.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Conclusion
 Acknowledgement
 References
 
After approval by the ethics committee of the University of Muenster, data of all patients treated by the acute pain service were prospectively enrolled over a period of 195 consecutive months (1 January 1998–31 March 2006). Anaesthesia and analgesia-related data on 18 925 patients receiving either PCEA for abdominal, thoracoabdominal, thoracic, and orthopaedic surgery or a CPNB of the brachial plexus or the femoral/sciatic nerve for upper or lower limb surgery, respectively, were collected in an electronic database. IV-PCA was used for patients after major surgery who could not receive a regional analgesia due to the type of surgery, patient refusal, or other contraindications (Table 1). Piritramide is commonly used in Germany and other European countries for postoperative analgesia and was first choice for IV-PCA in the present study. Piritramide and morphine are of equally analgesic efficacy and show a similar profile of adverse effects.11 12


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  		Table 1 Details of postoperative pain management for i.v. and epidural PCEA and CPNB and IV-PCA

 
The exclusion criteria for regional anaesthetic techniques were: patient rejection, coagulation disorders or concurrent treatment with anticoagulant medications, severe infections at the site of catheter insertion, generalized sepsis, and allergy to local anaesthetics. Exclusion criteria for IV-PCA were: inability to operate the device, allergy to opioids, respiratory insufficiency, and acute porphyria.

Obstetric patients, who received epidural analgesia for vaginal delivery, were not included into this database analysis.

All catheters were inserted immediately before operation and a standardized protocol, including information about the procedure, difficulties with catheter placement, acceptable daily pain scores, amount of administered medication, and recording of adverse events, was initiated by the anaesthesiologist.

Effectiveness of PCEA was confirmed perioperatively by analysing opioid consumption. The PCEA was terminated and the catheter removed, if additional systemic opioid therapy was required during operation and intolerable postoperative pain scores (VAS for pain at rest >30 and for dynamic pain >50) could not be treated adequately by PCEA.

At the end of surgery, the patient was transferred to the post-anaesthesia care unit (PACU) and efficacy of the analgesia regimen was documented in the standardized protocol for the acute pain service before discharge to the ward.

During the following postoperative days on their rounds, the acute pain service recorded cumulative analgesic consumption, the number of analgesic demands, and the patients' resting and evoked pain using a VAS score (0–100). The following side-effects were evaluated by the acute pain service at least once a day: incidence of motor block (Bromage score 0=normal; Bromage score 1–3 indicating a reduced motor function); incidence of respiratory depression (ventilatory frequency below 8 bpm); sedation score (1, awake patient, looking around; 2, tired, sleepy, easy to wake up; 3, somnolent patient; and 4, coma); incidence of hypotension (systolic arterial pressure <80 mm Hg); and the incidence of nausea or vomiting. A daily reassessment of the catheter insertion area was conducted by the acute pain service. Redness, pressure-related pain at the insertion area, temperature >38.5°C without a surgical explanation, or both were indications for removing a PCEA or CPNB catheter. Any occurrence of motor impairment or other drug-associated adverse events were treated with a decrease or stop of the background infusion of the PCEA or CPNB device in order to distinguish between a temporary block and persistent neurological damage. Persistent neurological adverse effects exceeding 4 h for PCEA or 24 h for CPNB were examined by a neurologist, who decides about the need for an MRI for patients with an epidural catheter and suspected epidural haematoma or abscess. Spinal malposition of epidural catheters was diagnosed by aspiration with a small syringe. Positive glucose test of the aspirated fluid was used as a sign for cerebral spinal fluid, indicating that the catheter was positioned accidentally intrathecally. Epidural malposition was diagnosed by repeated administration of bolus doses without significant analgesic effect. All documents about suspected adverse events were retrieved and analysed by the investigators.

During the whole observation period between 1998 and 2006, level of supervision of the acute pain service remained unchanged.

Data evaluation and statistical methods
Statistical testing was conducted with the Statistical Package for the Social Science system (SPSS 13.1; SPSS Inc., Chicago, IL, USA). Corrections and insertion of missing data were performed by checking the original documentation sheets or hospital medical records. Nominal scale variables were described using relative and absolute frequencies, and the {chi}2 test was used to assess differences between the groups. Fisher's exact test was used if sample size was small (expected frequencies <5). Owing to the fact that the data were not normally distributed, the Kruskal–Wallis test and Friedmann test were used to compare groups. Because pain intensity may depend on the type of surgical procedure, resting and dynamic pain scores for PCEA and IV-PCA after thoracotomy and visceral/abdominal surgery were compared in subgroup analyses. Furthermore, pain treatment by CPNB and IV-PCA were compared after extremity surgery.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Conclusion
 Acknowledgement
 References
 
Patient characteristics data
We obtained data on 18 925 patients supervised and treated by the acute pain service of the Department of Anaesthesiology (University of Muenster) between 1 January 1998 and 31 March 2006. With a PCEA, 14 223 patients were treated, 10 199 of these received a catheter at thoracic level and 4024 at lumbar level; 1737 patients and 1374 patients received a continuous brachial plexus or a combination of femoral and sciatic nerve block, respectively. An IV-PCA was used in 1591 patients (Table 2).


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  		Table 2 Patient characteristics and types of surgery

 
Efficacy of pain treatment
The postoperative pain intensity of all patients was determined by using a VAS (0–100) for resting and dynamic pain. The median VAS scores in patients who received a PCEA were below 30 when measured in the recovery room on the day of surgery. On postoperative day 1, median (range) VAS scores were 0 (0–100) at rest and 20 (0–100) for dynamic pain. Subsequently, median VAS scores for resting pain and dynamic pain decreased to 0 (0–100) and 10 (0–100), respectively, during the following 5 postoperative days (Fig. 1).


Figure 1
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  		Fig 1 Comparison between resting (A) and dynamic (B) pain scores of PCEA, IV-PCA, and CPNB during the first four postoperative days. The box plots show the median (fat bars), the inter-quartile range, and the extreme scores for individual variables (**P<0.001 using the Friedmann test with post hoc testing using Wilcoxon rank-sum test).

 
Patients who received CPNB, including brachial plexus block and femoral/sciatic nerve block, had median (range) pain scores on postoperative day 1 of 10 (0–100) for resting pain and 20 (0–100) for dynamic pain. A decrease of pain scores was observed during the following postoperative days (Fig. 1).

Patients who were prescribed IV-PCA had a median (range) VAS score of 10 (0–100) at rest and 30 (0–100) for dynamic pain on the day of operation, with a decline in pain scores the following postoperative days (P<0.001; Fig. 1). After thoracotomy and visceral/abdominal surgery, PCEA provided superior pain relief when compared with IV-PCA (P<0.05; Fig. 2). Furthermore, pain treatment by CPNB was significantly more effective compared with IV-PCA after lower or upper extremity surgery (P<0.05; Fig. 2).


Figure 2
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  		Fig 2 Procedure-specific dynamic pain intensity in patients undergoing thoracotomy (A), major abdominal surgery (B), and major extremity surgery (C). Comparison of PCEA and CPNB with patient-controlled i.v. analgesia during the first four postoperative days (**P<0.001 and * P<0.05 according to the Friedmann test with post hoc tests by Wilcoxon).

 
Adverse effects and complications of postoperative pain management
We found a significant lower rate of nausea and vomiting (P<0.001) in patients who received PCEA (13.7%) compared with patients who received IV-PCA (19.7%).

Patients who received IV-PCA suffered significantly less often from hypotension compared with patients with PCEA (2.6% vs 6.7%) (P<0.001). We observed a significantly higher incidence of hypotension with lumbar PCEA (7.7%) compared with thoracic PCEA (4.1%) (P<0.001). We recorded a significantly lower incidence of respiratory depression (ventilatory frequency <8 bpm) for patients receiving IV-PCA (0.7%) compared with a PCEA (1.1%) (P=0.002). Severe respiratory depression with subsequent tracheal intubation and ventilation occurred in one patient, who was treated with a thoracic PCEA (bupivacaine 0.175% and sufentanil 0.75 µg ml–1). The continuous background infusion of the PCEA was with 9 ml h–1 which was greater than our mean infusion rate of 4.97 ml h–1. None of the patients with IV-PCA showed symptoms of severe respiratory depression.

Non-neurological catheter-associated complications in patients with PCEA
Technical difficulties (Table 3) during placement of the epidural catheter included more than two attempts before correct placement of the catheter (thoracic 18.91%; lumbar 18.33%), paraesthesia during puncture or catheter placement (thoracic 0.47%; lumbar 0.82%; P<0.01), perforation of the dura (thoracic 0.81%; lumbar 1.02%; P<0.01), and a bloody tap (thoracic 1.75%; lumbar 3.06%; P<0.01). Epidural malposition was reported in 7.15% of thoracic and 6.71% of lumbar epidurals (P<0.001). Spinal malposition was reported in 0.54% of thoracic and 0.71% of lumbar epidurals (P<0.01). Unobserved disconnection of the PCEA system from the catheter for more than 2 h (hospital standard) (thoracic 0.63%; lumbar 0.69%) and occlusion of the catheter (thoracic 0.38%; lumbar 0.42%) resulted in the removal of the epidural catheter by the acute pain service (Table 3).


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  		Table 3 Catheter-related complications of PCEA and CPNB. Data are shown as numbers of patients and percentages. N/A, not applicable. *P<0.001 for comparisons between thoracic and lumbar epidurals ({chi}2 test)

 
Neurological catheter-associated complications in patients with PCEA
Temporary neurological symptoms lasting <5 days and not attributed to operation damage, including paraesthesia and motor impairment (Bromage score >1), were observed in 66 patients (0.46%) who received PCEA. We detected a significantly higher incidence of motor impairment after lumbar epidural analgesia (27/4024; 0.67%) than after thoracic epidural analgesia (39/10 199; 0.38%) during the 5 day observation period (P<0.001).

Epidural haematoma
Of the 14 223 patients who received PCEA, three patients were diagnosed by MRI with epidural haematoma giving a rate (95% CI) of 2.1 (0.4–6.1) per 10 000 patients. All the haematomas occurred in patients receiving lumbar epidurals (a total of 4024) giving a rate of lumbar epidural haematoma of 7.5 (1.5–22) per 10 000 and of thoracic epidural haematoma of 0 (0–3.6) per 10 000. None of these patients needed surgical intervention nor suffered prolonged neurological complications. All three cases with an epidural haematoma were female patients undergoing lower limb surgery and received a lumbar epidural catheter. In all cases, the catheter was still in place when the haematomas were diagnosed. Two of them were older than 75 yr with osteoporotic deformities (Table 4). All three epidural haematomas occurred in female patients who received lumbar epidurals (2496 patients) giving a rate of 12 (2.4–35) per 10 000 in this population.


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  		Table 4 Details of patients developing severe complications after a neuroaxial block

 
Epidural abscess
Two patients with PCEA were diagnosed with an epidural abscess on postoperative day 5, 1.4 (0–5.1) per 10 000 patients. One was thoracic and one lumbar giving rates of thoracic 0.1 (0.0–5.4) per 10 000 and lumbar 2.5 (0–13.8) per 10 000. The first patient undergoing surgery for knee infection developed a cauda equina syndrome and underwent immediate laminectomy revealing an epidural inflammatory process; information about the type of infection could not be retrieved from the hospital or postoperative pain database. A follow-up examination after 6 months showed only a partial recovery of neurological function, with persistent urinary incontinence but normal sphincter function. The second patient had a thoracic epidural catheter for major abdominal cancer surgery and suffered 5 days after surgery of pyrexia, back pain, and headache. The diagnosis was confirmed by MRI. After antibiotic treatment with a third-generation cephalosporin and flucloxacillin, the patient made a full neurological recovery. Only one of these two patients had an infection of the epidural insertion site (Table 4).

Meningitis
In the present database analysis, we observed one case of meningitis after epidural catheter placement, an incidence of 0.7 neurological deficits for more than 5 days (0.0–3.9) per 10 000. The patient had typical symptoms including back pain, headache, nuchal rigidity, and pyrexia. These occurred 10 days after catheter placement (5 days after catheter removal). Perforation of the dura did not occur during catheter placement. After excluding an epidural abscess by an MRI, the lumbar puncture revealed a positive culture with Staphylococcus aureus. After antibiotic treatment, the patient showed complete recovery (Table 4).

Non-neurological catheter-associated complications in patients with CPNB
Technical difficulties placing the peripheral catheter were observed for brachial plexus block in 5.5% and femoral/sciatic nerve block in 9.1% (Table 3). Failed insertion of the peripheral catheter was reported for 8.9% in cases of brachial plexus block and for 6.0% in cases of femoral/sciatic nerve block. The incidence of catheter disconnection and occlusion was below 1% in all peripheral regional analgesia regimens.

Neurological catheter-related complications in patients with CPNB
The incidences of temporary neurological complications including sensory and motor impairment lasting <5 days and was 1.7% for brachial plexus block and 0.55% for femoral/sciatic nerve block. Prolonged neurological deficits for >5 days upon catheter removal occurred in two of 1737 patients with an interscalene brachial plexus catheter after shoulder surgery, a rate of 11.6 (1.4–41.7) per 10 000 and in none of the patients with a combined sciatic and femoral nerve block. The overall incidence of severe neurological complications after CPNB was 2:3111 (0.06%). However, we could not distinguish in several cases of neurological complications between a needle or catheter-related trauma and other variables including perioperative positioning, tourniquet ischaemia, or surgical traction. All events resolved without sequel.

A peripheral insertion site infection was detected in 22 (95% CI 12.9–31.1) (1.3%) patients with a brachial plexus block and in 33 (95% CI 21.8–44.1) (2.4%) patients with a combined femoral or sciatic nerve block. However, none of the patients developed an abscess or needed surgical treatment. No serious bleeding or haematoma due to CNPB was observed in the present series.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Conclusion
 Acknowledgement
 References
 
The present study is the largest prospective single-centre analysis of postoperative pain patients published yet. Our data suggest that multimodal postoperative pain regimes with PCEA, CPNB, and IV-PCA, supervised daily by an acute pain service, are safe and sufficient. The efficacy of pain relief with PCEA or CPNB at rest and during movement was superior to IV-PCA. A low incidence of adverse effects and complications was detected for neuroaxial and i.v. analgesic regimes. We observed a lower rate of adverse effects including hypotension and motor impairment for thoracic PCEA compared with lumbar PCEA. We also observed a lower incidence of epidural haematoma with thoracic PCEA than lumbar PCEA, but the number of events was too small for a statistically meaningful comparison and this difference could have been due to chance. Serious adverse effects after CPNB were rare.

Efficacy of postoperative pain relief by PCEA, IV-PCA, or CPNB
There is ample evidence that postoperative IV-PCA and PCEA gives better pain relief than conventional on-demand opioid treatment, may decrease surgical morbidity, and is the preferential choice of patients for postoperative pain treatment.5 6 Several studies comparing PCEA5 6 13 or CPNB7 with IV-PCA found lower scores for resting and dynamic pain, better recovery, and a decrease in the length of hospital stay. Similar results were obtained in the present study demonstrating superior analgesia in combination with reduced adverse side-effects and improved mobility for PCEA and CPNB compared with IV-PCA.

Opioid-related adverse effects
Nausea and vomiting
The most common symptoms besides pain in the perioperative period are nausea and vomiting. Although pain by itself can contribute to nausea and vomiting, an important reason for its occurrence in the postoperative period is the use of perioperative opioids. In a recent evidence-based review, including female and male patients receiving PCEA with different opioids or IV-PCA, the mean incidence of nausea and vomiting was 16–19% and 21–32%, respectively.14 Although it has been hypothesized that the incidence of nausea and vomiting may be greater for IV-PCA than for PCEA, only a few studies investigated this issue. In the present study, we demonstrated a significant lower incidence of opioid-induced nausea and vomiting for PCEA (13.7%) compared with IV-PCA (19.7%) during the observation period. Because opioid-induced nausea and vomiting during acute pain therapy is dose-dependent, a smaller dose of neuroaxial administered sufentanil of 0.75 µg ml–1 compared with 1 µg ml–1 frequently used in other studies may be a reason for these reduced side-effects during PCEA compared with IV-PCA.

Respiratory depression
A potentially serious complication for i.v. or neuroaxial PCA is opioid-induced respiratory depression which is defined by a ventilatory frequency <8–10, a percutaneous oxygen saturation <90%, or by an arterial blood gas analysis of carbon dioxide >6.5 kPa.15 The incidence varies depending on the methods used to detect respiratory depression and has been reported to be 1.2–11.5% for IV-PCA and 1.1–15.1% for PCEA.15 In a retrospective analysis of published data, Cashman and Dolin15 found no difference in respiratory depression, defined by ventilatory frequency, between PCEA and IV-PCA. Similar results were obtained by Mann and colleagues16 in a prospective randomized study in elderly patients after major abdominal surgery. Flisberg and colleagues17 reported in a prospective study a higher frequency of respiratory depression for IV-PCA compared with PCEA. Furthermore, the authors found a tendency to early respiratory depression for PCEA and a delayed reduction of ventilatory frequency for IV-PCA.17 In contrast to others, we observed a significantly greater incidence of respiratory depression for PCEA (1.1%) compared with IV-PCA (0.7%). The reason for this discrepancy may be the use of an IV-PCA with background infusion in several other studies which has been identified as an important factor for respiratory depression.4

Motor block
Early mobilization improves patient morbidity and decreases the length of hospital stay. Besides adequate postoperative analgesia, a low incidence of motor block during PCEA is important to reach this goal. Motor block has frequently been reported during the use of epidural analgesia and is often a reason for early termination of postoperative epidural analgesia.17 In our study, we revealed an overall low motor impairment of 0.5% indicating that the regime used by our institution allows early mobilization in almost all postoperative patients. We detected a higher incidence of motor block for lumbar PCEA compared with thoracic PCEA which is consistent with reports by others17 and supports the preferential use of thoracic epidural analgesia in the perioperative period whenever it is indicated.

Because sympatholytic effects accompany a motor block, we analysed the rate of hypotension associated with PCEA and identified an increased incidence of hypotension for lumbar vs thoracic PCEA which may be explained in part by reflex arterial dilatation and bradycardia via the Bezold–Jarisch reflex.18 Together with clinical and experimental studies reporting a reduced myocardial blood flow distal from coronary artery stenosis, a possible increase of oxygen demand by sympathetic activation in non-blocked thoracic segments and an impairment of myocardial wall motion for lumbar epidural anaesthesia,18 19 the present results favour the preferential use of thoracic epidural anaesthesia for thoracic or thoracoabdominal surgeries.

Epidural haematoma
A recent large retrospective analysis of severe neurological complications after central neuroaxial blocks in Sweden (1990–1999) demonstrated a specific risk for epidural haematoma in a certain population of patients and detected an incidence of epidural haematoma in obstetric patients of 1:200 000 and in female patients with knee arthroplasty of 1:3600 (mean overall risk for epidural haematoma 1:18 000).10 Two recently published single-centre database analyses by Christie and colleagues9 (8100 patients) and Cameron and colleagues8 (8120 patients) detected a higher overall incidence of epidural haematoma between 1:2700 and 1:4105. Christie and colleagues9 reported that all three cases of epidural haematoma were elderly (65–79 yr) female patients. In the present study, we detected three epidural haematomas in 14 223 patients receiving PCEA and calculated similarly to Christie and colleagues and Cameron and colleagues an overall incidence of 2.1 per 10 000 patients (1:4761). All three cases with an epidural haematoma were female patients who received a lumbar epidural catheter for lower limb surgery. Two of them were older than 75 yr with osteoporotic deformities. Similar to Moen and colleagues, we detected a high incidence of epidural haematoma for female patients undergoing lower limb surgery of 12 (2.4–35) per 10 000 (1:832). Reasons for this high incidence of epidural haematoma in this subgroup of patients are complex and not completely understood. Lower limb arthroplasty is most often performed in elderly patients receiving often traditional non-steroidal anti-inflammatory drugs (NSAIDs) and anticoagulants which both impair platelet function—an important cause for catheter-induced epidural haematoma. However, our patients did not receive NSAIDs or heparin during PCEA in the present study. Furthermore, the national guidelines for anticoagulation and antiplatelet treatment during neuroaxial anaesthesia were followed for catheter placement and removal during the whole observation period (1997–2006). Moen and colleagues10 reported that in their study only four of the 13 orthopaedic patients with epidural haematoma received traditional NSAIDs. However, alteration in hepatic and renal metabolic function, especially in the elderly, may result in a reduced elimination of anticoagulation and antiplatelet agents. Postmenopausal elderly female patients may suffer from osteoporosis and have a high incidence of osteoporotic or degenerative deformities of the spine resulting in repeated attempts of catheter placements, another risk factor for the development of an epidural haematoma.10

Our study offers further support to the impression that elderly female patients with lower limb surgery receiving a lumbar epidural catheter have a high incidence of epidural haematoma, although it should be borne in mind that our observation is based on only three events and so could be due to the effect of chance. The exact reasons for a possible increased incidence of epidural haematoma with lumbar epidurals are not fully understood. A recent meta-analysis demonstrates that, for major knee surgery, a peripheral nerve block produced similar pain relief with less adverse effects compared with a lumbar epidural analgesia;20 we suggest the use of CPNB for lower limb surgery.

Epidural infections
From retrospective studies, the incidence of an epidural abscess varies between 1:500 and 1:10 000.10 In two recent prospective studies, six8 and nine9 cases of epidural abscess were associated with incidences of 1:1368 and 1:1350, respectively. In the present prospective study, two cases of an epidural abscess, one after lumbar and one after thoracic epidural catheter placement, were observed, resulting in an incidence of 1:7112. Both cases were patients with several risk factors including older age, compromised immunity by complicating diseases,21 and a duration of catheterization of more than 4 days.22 In agreement with Christie and colleagues,9 one of the patients had an infection of the epidural insertion site, indicating that visible inflammation should result in prompt epidural catheter removal,8 22 but that an epidural abscess can also occur in patients without an epidural site infection.

Pooling the data of the studies mentioned above8 9 22 and the present study gives an overall incidence of 1:3127 and suggests that several factors including older age, immunocompromisation, and a prolonged duration of catheterization (more than 4 days) are risk factors for the development of an epidural abscess.

Serious adverse effects: CPNB
Two large prospective studies23 24 reported an incidence of severe neurological complications after peripheral nerve blocks of 2.7–3.8:10 000 (0.03–0.04%). In agreement, we observed in the present study an incidence of neurological complications of 2:3111 (0.06%). However, Capdevila and colleagues25 reported a higher rate of serious neurological adverse events after CPNB of 3:1422 (0.21%). A possible reason for this discrepancy may be that, in this study, two of the three continuous nerve blocks were performed in anesthetized patients. In a recent narrative review, Brull and colleagues26 stated that interscalene blocks carry the highest risk of transient neurological deficits. We observed a prolonged motor block and paraesthesia in two female patients after shoulder surgery with an interscalene brachial plexus block. However, neurological investigations could not distinguish between a possible nerve injury due to the CNPB or shoulder surgery and complete recovery was observed for both cases within 4 weeks.

Continuous perineural catheter infection is a rare event with an incidence between 0.02% and 3%.25 27 In the present study, a peripheral insertion site infection was detected in 22 patients with a brachial plexus block and in 33 patients with a combined femoral/sciatic nerve block, resulting in an overall incidence for moderate infections of 1.8%. However, none of the patients developed an abscess or needed antibiotic or surgical treatment.


   Conclusion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
Acknowledgement
 References
 
In this large prospective single-centre database analysis of postoperative pain patients, we demonstrated that the presented pain treatment regimes of PCEA, CPNB, and IV-PCA are safe and effective. In agreement with other studies, our data suggest that neuroaxial and continuous perineural analgesia is superior to IV-PCA. We observed fewer side-effects including hypotension and motor impairment during thoracic PCEA compared with lumbar PCEA. Close supervision of all of these techniques by an acute pain service in the postoperative period is mandatory.


   Acknowledgement
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgement
References
 
We would like to thank Heinrich Wempe for his support in electronic data processing.


   Footnotes
 
{dagger} Parts of this study were presented as an abstract at the Annual Scientific Meeting of the European Society of Anaesthesiology 2007. Back


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Conclusion
 Acknowledgement
 References
 
1 Wu CL, Rowlingson AJ, Partin AW, et al. Correlation of postoperative pain to quality of recovery in the immediate postoperative period. Reg Anesth Pain Med (2005) 30:516–22.[CrossRef][Web of Science][Medline]

2 Apfelbaum JL, Chen C, Mehta SS, Gan TJ. Postoperative pain experience: results from a national survey suggest postoperative pain continues to be undermanaged. Anesth Analg (2003) 97:534–40. table of contents.[Abstract/Free Full Text]

3 Kehlet H, Holte K. Effect of postoperative analgesia on surgical outcome. Br J Anaesth (2001) 87:62–72.[Abstract/Free Full Text]

4 Momeni M, Crucitti M, De Kock M. Patient-controlled analgesia in the management of postoperative pain. Drugs (2006) 66:2321–37.[CrossRef][Web of Science][Medline]

5 Block BM, Liu SS, Rowlingson AJ, et al. Efficacy of postoperative epidural analgesia: a meta-analysis. J Am Med Assoc (2003) 290:2455–63.[Abstract/Free Full Text]

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7 Richman JM, Liu SS, Courpas G, et al. Does continuous peripheral nerve block provide superior pain control to opioids? A meta-analysis. Anesth Analg (2006) 102:248–57.[Abstract/Free Full Text]

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