Research Article: Procedural Complications of Spinal Anaesthesia in the Obese Patient

Date Published: July 30, 2012

Publisher: Hindawi Publishing Corporation

Author(s): Manuel Wenk, Christian Weiss, Michael Möllmann, Daniel Matthias Pöpping.


Background. Complications of spinal anaesthesia (SpA) range between 1 and 17%. Habitus and operator experience may play a pivotal role, but only sparse data is available to substantiate this claim. Methods. 161 patients were prospectively enrolled. Data such as spread of block, duration of puncture, number of trials, any complication, operator experience, haemodynamic parameters, was recorded and anatomical patient habitus assessed. Results. Data from 154 patients were analyzed. Success rate of SpA in the group of young trainees was 72% versus 100% in the group of consultants. Trainees succeeded in patients with a normal habitus in 83.3% of cases versus 41.3% when patients had a difficult anatomy (P = 0.02). SpA in obese patients (BMI ≥ 32) was associated with a significantly longer duration of puncture, an increased failure ratio when performed by trainees (almost 50%), and an increased number of bloody punctures. Discussion. Habitus plays a pivotal role for SpA efficiency. In patients with obscured landmarks, failure ratio in unexperienced operators is high. Hence, patient prescreening as well as adequate choice of operators may be beneficial for the success rate of SpA and contribute to less complications and better patient and trainee satisfaction.

Partial Text

Ever since the introduction of spinal anaesthesia more than a century ago, complications have been part of the technique; failed or insufficient block, headaches, nausea, vomiting, and pain around the injection site are common minor complications [1, 2]. The technique of spinal anaesthesia (SpA) is considered a basic skill, however, one that first has to be mastered. According to literature, the incidence of failed or partially failed SpA ranges between 0.5 and 17% [3–5]. The incidence of postdural puncture headaches (PDPHs) ranges between 0,7 and 11% based on the type of needle used [6, 7], and transient neurologic syndromes can still be observed after SpA with an incidence of 0–7% [8].

After approval from the Ethics Committee of the Medical Faculty of the University of Muenster (protocol 2009-459-f-S), 161 patients planned for elective orthopedic or vascular surgical procedures of the lower limb under SpA were enrolled in the study. Informed consent was obtained from each patient.

161 patients were enrolled in the study. 7 patients were excluded due to changes in the treatment plan. Complete data sets of 154 patients were subsequently analyzed.

Spinal anaesthesia has an excellent safety record in terms of major complications. However, there is a significant number of minor complications that—each on its own—may cause unpleasant sequelae for the patient [3, 4, 13]. The majority of complications are associated with the procedure itself. Insufficient or failed SpA ranges from 0 to 17% and bloody punctures as well as significant hypotension are not uncommon [3, 9]. The current study shows that the overall failure rate of SpA is comparable to previously published data. We have shown that success and failure rate appears to be directly dependent on the operator’s experience and the individual patient habitus. Trainees failed significantly more attempts to perform SpA, had more difficulties placing SpA in patients with obscured landmarks, and had significantly more bloody punctures, and the procedure duration was significantly longer as compared to experienced specialists. It has been shown previously that SpA is a complex procedure that is more difficult to master than, for example, endotracheal intubation [14]. Furthermore, it has been estimated that the experience of around 100 performed SpA is required to achieve a 90% success rate [15]. Our data shows that young trainees had a success rate of 84% in patients with a normal anatomy, indicating that some trainees have probably mastered the technique while others were still on the ascending part of the learning curve. However, this picture changes completely when patients present with obscured landmarks or difficult anatomy. Trainees, who were able to perform SpA successfully in anatomically “easy” patients, suddenly faced a failure rate of 52% in those patients with a difficult habitus, significantly different to “easy” patients. Consultants were able to place a SpA even in the difficult patients but in 42.5% of cases, 3 or more punctures were required to position the spinal needle in the correct location. To our knowledge, this is the first study that specifically investigated the role of the individual patient habitus by rating landmarks and other anatomical features. Part of educating trainees is to accept that they do have a higher failure rate [16, 17], and it is the responsibility of the relevant societies to define what is an acceptable failure rate for which procedure [18]. Based on our findings we postulate that an experienced anesthesiologist should anatomically rate all patients who are about to receive SpA and if the habitus is considered to be difficult, young trainees should probably not perform SpA to avoid frustration and build a more solid foundation based on successfully performed punctures rather than failing every second attempt. However, from our data, it appears that young trainees do have a higher failure rate, but they do not cause significantly more complications. Hence exposure to the difficult patient is relatively safe, once a solid foundation of the technique has been established. We recommend that the level of supervision should be adequate to avoid that the operator’s success or fail rate in these patients is significantly lower than in experienced operators. Multiple attempts by young trainees as well as experienced operators lead to a more significant reaction of hemodynamic parameters. Blood pressures dropped significantly more in patients where multiple attempts were necessary. We offer two possible explanations. Firstly, multiple attempts may lead to the operator changing spinal segments, and the direction is usually upwards thus causing more sympathetic block. Secondly, multiple attempts may cause stress and enhance anxiety in the patient hence causing disturbances of the autonomous sympathetic regulation. Last but not least, avoiding multiple attempts may also affect patient satisfaction, but we have not investigated that matter.

Albeit a relatively safe technique, SpA has its problems and pitfalls, and our study has shown that increased operator-experience results in a higher success rate of SpA. Furthermore, the individual patient’s habitus plays a pivotal role when trainees are involved in performing SpA. Even for experienced anesthesiologists this group of patients has its challenges, but the failure rate of SpA is still very low. We conclude that careful patient selection and prescreening as well as adequate choice of operators is beneficial for the success rate of SpA and may contribute to less complications, greater safety, better patient, and trainee satisfaction.




Leave a Reply

Your email address will not be published.