Block-related complications in peripheral nerve blocks
Regarding PNBs (Table 4), we found four cases of LAST (0.19/1000) and three cases of pneumothorax after periclavicular blocks (1.48/1000). There was no statistical significance in the rates of LAST and pneumothorax between awake and sedated or anaesthetised patients.
The incidence of bloody tap was significantly higher in sedated (3.3%) and anaesthetised (3.8%) patients (awake 2.2%; P < 0.001). After adjustment for relevant confounders (sex, age, anticoagulation, use of ultrasound, multiple skin puncture, premature termination), both sedation [adjusted OR: 1.82 (1.50 to 2.21)] and general anaesthesia [adjusted OR: 1.33 (1.01 to 1.78)] seem to be associated with a significantly increased risk for a bloody tap.
The incidence of multiple skin puncture was found to be significantly lower in sedated (11.2%) and higher in anaesthetised (18.8%) patients (awake 13.9%; P < 0.001). Adjusted for relevant confounders (age, diabetes, anticoagulation, use of ultrasound, bloody taps, premature termination), the risk for multiple skin puncture was similarly lower in sedated [adjusted OR: 0.78 (0.71 to 0.85)] and higher in anaesthetised patients [adjusted OR: 1.28 (1.12 to 1.46)].
The overall rate of premature termination was low (0.25%) and sedation was associated with a significantly lower incidence (awake: 0.3%, sedated: 0.1%; P = 0.01) and risk [adjusted OR: 0.45 (0.22 to 0.91); adjusted for anticoagulation, use of ultrasound, multiple skin puncture, bloody tap]. Under general anaesthetic, the incidence of premature termination (awake: 0.3%, anaesthetised: 0.5%, P = 0.21) and the risk [adjusted OR 1.11 (0.52 to 2.37)] were comparable with awake patients. Unfavourable anatomical conditions were much more often the reason for abandoning the block procedure than insufficient patient compliance.
The incidence of primary failure was significantly lower when the block was performed under sedation (awake: 0.8%; sedated: 0.5%; P < 0.01) and as was the risk [adjusted OR: 0.58 (0.40 to 0.83); adjusted for use of ultrasound, multiple skin puncture].
For postoperative paraesthesia, we found a decreased incidence (awake: 3.4%; sedated: 1.2% and anaesthetised: 0.5%; P < 0.001) and risk in the group of sedated [adjusted OR: 0.35 (0.28 to 0.45)] and anaesthetised [adjusted OR: 0.16 (0.06 to 0.38)] patients (adjusted for age, anticoagulation, use of ultrasound, multiple skin puncture, bloody tap).
Patient satisfaction with the regional anaesthesia was significantly higher whenever performed under sedation (awake: 8.0 ± 3.4; sedated: 9.2 ± 2.1; P < 0.001). We found no further benefit for patients receiving the block procedure under general anaesthetic (awake: 8.0 ± 3.4; anaesthetised: 8.2 ± 3.5; P = 0.6).
Block-related complications in neuraxial blocks
Regarding neuraxial blocks (Table 5), four cases of LAST (0.19/1000), one case of pneumothorax (0.10/1000) after a thoracic epidural attempt and 96 cases of accidental dural puncture within thoracic (4.9/1000) and lumbar (7.2/1000) epidurals were documented. There was no statistically significant difference in the rates of LAST, pneumothorax and accidental dural puncture between the study groups.
The incidence of bloody tap in neuraxial blocks was comparable between awake and sedated patients, but significantly lower in anaesthetised patients (awake: 1.4%; sedated: 1.2% and anaesthetised 0.0%; P < 0.001).
The incidence of multiple skin puncture was significantly higher in sedated (31.4%) and lower in anaesthetised (17.0%) patients (awake 27.0%; P < 0.001) as was the risk, being increased under sedation [adjusted OR: 1.18 (1.09 to 1.29)] and decreased under general anaesthetic [adjusted OR: 0.53 (0.39 to 0.72); adjusted for sex, diabetes, anticoagulation, use of ultrasound, bloody taps, premature termination].
The incidence of premature termination for anatomical reasons was much greater than insufficient patient compliance and it was equally distributed between the study groups (awake: 0.6%; sedated: 0.5% and anaesthetised: 0.7%). In contrast to our results in PNBs, neither sedation nor general anaesthesia influenced the risk of premature termination.
The incidence of primary failure was comparable between sedated (0.2%) and awake (0.3%; P = 0.07) patients. In contrast to our results in PNBs, sedation did not decrease the risk of primary failure in neuraxial blocks (adjusted for anticoagulation, multiple skin puncture).
Regarding the risk of postoperative paraesthesia, we found no influence of sedation, but a significantly higher risk for patients receiving the neuraxial block under general anaesthetic [adjusted OR: 2.45 (1.19 to 5.02); adjusted for multiple skin puncture].
Patients were significantly more satisfied with regional anaesthesia when the neuraxial block was performed under sedation (awake: 7.4 ± 3.8, sedated: 7.9 ± 3.6; P = 0.01), whereas those receiving the neuraxial block under general anaesthetic had lower satisfaction (awake: 7.4 ± 3.8, anaesthetised: 6.5 ± 4.1; P < 0.001).
In contrast to paediatric regional anaesthesia, only a few single-centre studies and anecdotal reports are available for regional anaesthesia performed in anaesthetised adults to assess the balance between comfort and safety.18–24 In searching for block-related acute complications, we were able to analyse 21 338 cases with PNBs and 21 316 cases with neuraxial blocks. Our multicentre analysis of 42 654 cases is the first study to focus upon the patient's state of consciousness during regional anaesthesia procedures and how this may affect the incidence and risk of complications, and patient satisfaction.
We found that LAST and pneumothorax rates were independent of the state of consciousness. The incidence of LAST was low in peripheral and neuraxial puncture sites (0.19/1000), nevertheless close to the range known from literature (0.07 to 1/1000).25 Sedation or block placement under general anaesthetic did not affect the incidence of LAST, so our results for adult patients are in accordance with Taenzer et al.'s22 registry analysis in 53 564 paediatric patients. A very low incidence was also found for pneumothorax. Only one of four reported cases was related to a thoracic epidural (0.10/1000), three occurred in the context of periclavicular block placement (1.48/1000) performed without ultrasound guidance. By using the landmark technique or nerve stimulation, the incidence of pneumothorax reported in previous studies ranges from 0.2 to 0.7% for infraclavicular and up to 6.1% for supraclavicular blocks.26,27 Gauss et al.28 reported only four pneumothoraces in 6366 ultrasound-guided periclavicular blocks and attributed the reduced incidence of pneumothorax to the ability to visualise the pleura and the advancing needle tip by ultrasound. According to our data, additional sedation or block placement under general anaesthetic seems not to influence the incidence of pneumothorax. Underreporting is possible, because the diagnosis of pneumothorax is not systematically excluded in clinical routine. In our study, the incidence of pneumothorax and LAST was too low to draw any firm conclusions regarding the patients’ state of consciousness during regional anaesthesia procedures but we feel that, based on these data, there is no strong reason to withhold sedation from patients or not to perform regional anaesthesia under general anaesthesia as long as appropriate vigilance is maintained for these complications.
In PNBs, the risk of a bloody tap increased significantly under sedation or general anaesthesia possibly because of the vasodilatation caused by anaesthetics and sedative drugs. When nerve stimulation instead of ultrasound is used, the vessels cannot be detected.29 Surprisingly, in our analysis, the increased risk of a bloody tap was independent of the use of ultrasound, even though ultrasound per se is known to reduce the rate of vascular punctures.30 But venous blood vessels in particular can be easily compressed by the transducer and can be overlooked. Although we expected underreporting of the incidence of bloody tap, there was no positive correlation between the increased incidence of bloody tap under sedation or general anaesthetic and the incidence of LAST. The increased risk for a bloody tap caused by sedation and general anaesthesia seen in PNBs was not confirmed in neuraxial blocks. Although we expect underreporting, the incidence of bloody tap in neuraxial blocks is obviously lower than in PNBs. A possible reason for this phenomenon could be the fact that PNBs are usually performed under continuous aspiration; therefore, a puncture of even a small vessel will be immediately detected. On the other hand, neuraxial blocks are performed using continuous positive pressure to detect the loss of resistance reaching the epidural space. In this case, only a vascular puncture of the epidural veins can be visualised, provided that there is sufficient bleeding to passively fill the needle used for the neuraxial block, which is usually thicker than a needle used for PNBs. But overall, the incidence of documented bloody taps in our network is too low to reach a reliable conclusion.
Multiple skin puncture is a risk factor for infectious complications and has to be avoided whenever possible.31 Our hypothesis, that sedation during block performance could enhance the operating conditions and therefore reduce the incidence and the risk of multiple skin puncture, was confirmed in PNBs. Surprisingly, instead of the expected further reduction, performing PNBs in anaesthetised patients increased the risk. In literature, there is no evidence for this phenomenon, but one possible hypothesis could be the ‘human factor’: when performing PNBs in anaesthetised patients who are not able to report the pain produced by the skin puncture, the threshold for rectifying the needle position with a new skin puncture may be lower than in awake or sedated patients. Our results concerning multiple skin puncture in neuraxial blocks are in contrast to our findings in PNBs. We can only speculate why sedation significantly increases the incidence and risk for multiple skin puncture in neuraxial blocks, whereas block placement under general anaesthetic decreases it. The incidence of multiple skin puncture in neuraxial blocks is much greater than the incidence in PNBs, and is most likely because of the necessity to try different levels if there are anatomical difficulties. Our data show that sedation is less common for neuraxial techniques than for PNBs and we expect it to be used particularly in difficult block placement, which is associated itself with an increased risk for multiple skin puncture.32 Performing neuraxial blocks in anaesthetised patients constituted an exception in our network data and it is certainly reserved for very experienced anaesthesiologists or specific situations (e.g. ICU). This may explain the lower risk for multiple skin puncture in this subgroup of patients.
Sedation significantly reduced the risk of premature termination of the PNB as well as the risk of primary failure. Our results confirm the hypothesis that sedation can enhance the operating conditions for the anaesthesiologist performing the block and can reduce the risk of a required change in anaesthetic techniques. Moreover, we observed no benefit in terms of circumventing anatomical difficulties when general anaesthesia was used. Considering that anatomical problems were the most reported cause for abandoned neuraxial blocks, it seems logical that improving the operating conditions by periprocedural sedation may also reduce complications in neuraxial blocks. This hypothesis was not proven for accidental dural puncture being comparable between awake, sedated and anaesthetised patients. Although the sample size particularly in the group of anaesthetised patients is too small for a reliable statement, our results (which revealed a mean of 0.39% for accidental dural puncture) are close to the rates reported in the literature (0.4 to 0.7%).33–35 Additional sedation or block placement after induction of general anaesthesia in neuraxial blocks did not influence the risk for premature termination or primary failure, which confirms our impression that additional sedation in neuraxial blocks does not have the same beneficial value than in PNBs. This can also be applied to the risk of postoperative paraesthesia after epidural catheter placement not being influenced by sedation. Caution should be exercised performing neuraxial catheter placements under general anaesthetic. The risk for postoperative paraesthesia may be raised, but the power of our present analysis is too low to be definitive in this setting.
Although the NRA database does not provide information on long-term outcomes of acute complications, there is evidence that paraesthesia extending beyond the normal residual effects of the peripheral regional anaesthesia is a serious warning sign and has to be monitored closely.36,37 In our analysis, the mean incidence for postoperative paraesthesia in patients with continuous regional anaesthesia was 1.05% for neuraxial block and 1.46% for PNB. This is comparable with the previously reported incidences because early transient postoperative neurologic symptoms are very common in the first days and decline with time.38–40 Our results show that both sedation and general anaesthesia reduce significantly the incidence and the risk of postoperative paraesthesia in PNBs and may therefore contribute to increased safety in continuous peripheral regional anaesthesia.
Our multicentre analysis confirms results from previous investigations that patient satisfaction with peripheral or neuraxial regional anaesthesia is significantly higher when the block is performed under sedation.41,42 In line with previous studies, which reported that 15 to 57% of patients received sedation during regional anaesthesia procedures, our study found that 56% of PNBs and 15% of neuraxial blocks were performed in sedated patients, which may represent current practice in German hospitals.11,41 However, we found that performing nerve blocks after induction of general anaesthesia did not improve patient satisfaction further. In our analysis, anaesthetised patients account for 10.4% of PNBs and 1.4% of neuraxial blocks, but in the literature, there is a high variability in the percentages of patients receiving regional anaesthesia in an anaesthetised state.13,32,43 This suggests uncertainty among clinicians on this issue and should encourage further research to develop guidance on best practice.
Our investigation was not designed to clarify possible mechanisms of interaction. Data in our registry do not provide information on long-term outcomes of acute complications or on persistent nerve damage. It is necessary to study a large number of patients to reliably determine the incidence of rare complications and to elucidate risk factors in their production. During the long observation period of 5 years, progress in medicine, technique or anaesthesia methods may have caused bias of the results and represents an important limitation in a registry study. All medical centres participating in this registry are enthusiastic proponents of regional anaesthesia, which could have biased our findings.15 Other confounding factors such as the use of tourniquet in trauma and orthopaedic surgery represent a further limitation. Many other ill-described factors (posture, surgery type, catheter misplacement detection) may also be responsible for unknown bias. Registries critically depend on the quality of data entry and handling and we could not provide external validity. The distribution of complications, however, seems to be plausible.
Additional sedation for peripheral regional anaesthesia procedures offers a number of benefits to the patient and the anaesthesiologist and should be recommended to all those patients where there are no contraindications. Performing PNBs under general anaesthetic does not enhance the risk of major complications, but particular precaution should be taken to avoid multiple skin puncture und bloody taps in anaesthetised patients. Procedural sedation for neuraxial blocks enhanced patient comfort without further beneficial effects. Performing neuraxial blocks in anaesthetised patients should be reserved for special situations and for experienced anaesthesiologists because of the increased risk of postoperative paraesthesia.
Acknowledgements relating to this article
Assistance with the study: we thank all hospital centres that are part of the NRA and have collected data for the present study: Bad Saarow – Helios Klinikum, SPW; Bad Wildbad – Sana Klinik, Dr Jens Döffert; Berlin – Charité CCM und CVK, Professor Claudia Spies; Berlin – DRK Kliniken Westend, Professor Arnd Timmermann; Bochum – Knappschaftskrankenhaus, Professor Michael Adamzik; Dresden – Universitätsklinikum, Professor Thea Koch; Erfurt – Helios Klinikum, Dr Gerald Burgard and Professor Andreas Meier-Hellmann; Frankfurt – BGU, Dr Rolf Teßmann; Frankfurt – Orthopädische Uniklinik, Professor Paul Kessler; Hamburg – Universitätsklinikum Eppendorf, Professor Alwin E. Goetz; Hannover – Diakoniekrankenhaus Friederikenstift gGmbH, Professor André Gottschalk; Jena – Uniklinikum, Professor Konrad Reinhart; Marburg – Universitätsklinikum, Professor Hinnerk Wulf; Memmingen – Klinikum, Professor Lars Fischer; Siegen – St. Marien-Krankenhaus, Professor Werner Hering; Solingen – Klinikum, Professor Thomas Standl; Ulm – Rehabilitationskrankenhaus, Dr Peter M. Geiger. We thank Karen Schneider and Ralf Heckmann for their critical revision of the manuscript and language correction.
Financial support and sponsorship: the analysis was supported by institutional funds. The German Network of Regional Anaesthesia database is supported by the Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin e.V., Berufsverband Deutscher Anästhesisten e.V. and Deutsche Forschungsgemeinschaft.
Conflicts of interest: none.
Presentation: preliminary data for this study were presented as a poster presentation at the European Society of Regional Anaesthesia (ESRA) Annual Meeting, 5 September 2013, Glasgow.
Details of authors contributions: CK, KS, NA, NRA Investigators HB and TV had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. Together with TS, TS, AG, WM, SPW, JB, AR, JS, PK and SG, they made substantial contributions to the concept and the design of the study; the acquisition; the analysis and the interpretation of data and drafting the article and revising it critically for important intellectual content.
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