Comments a recent paper
about local anesthetic systemic toxicity...

 

Ultrasound Guidance Reduces the Risk of Local Anesthetic Systemic Toxicity Following Peripheral Nerve Blockade.

 

Reg Anes Pain Med 2013; 38: 289-299. 

M.J. Barrington and R. Kluger. 

 

   Local anaesthetic systemic toxicity (LAST) is one of the significant but rare complications of regional anaesthesia. This well-conducted multi-centre study analysed prospectively collected data from over 25000 peripheral nerve blocks (PNB) and examined whether using ultrasound to localise nerves affected the development of LAST.

 

   It is already known that ultrasound reduces both the incidence of vascular puncture and the amount of local anaesthetic required for successful nerve blockade.

 

   This study by Barrington was important because it demonstrated that using ultrasound improved clinical safety. The authors found that using ultrasound, compared to not using ultrasound, significantly reduced the incidence of LAST by a factor of around 3 to 4 times (depending on the statistical model used).

 

   Interestingly however the incidence of vascular puncture in this study, unlike other work, was not reduced by ultrasound. The authors did find the amount of local anaesthetic was reduced when ultrasound was used, and this may therefore be one major reason why LAST was reduced in the ultrasound group. The study was also useful as it provided further data on the incidence of LAST (0.87 per 1000 PNBs) and confirmed that, as expected, the site (paravertebral most commonly, followed by upper then lower limb blocks), local anaesthetic dose and patient weight also were associated with LAST. Interestingly lidocaine was much more likely to be associated with LAST compared with ropivicaine.

 

   Overall, this study is of interest as despite some minor limitations it demonstrates that ultrasound significantly improves the clinical safety profile of peripheral nerve blockade by reducing the incidence of LAST.

 

References

 

Abrahams et al. Br J Anaesth 2009;102: 408–417.

Career Path
Becoming an expert...
 
 

ALAN MACFARLANE MD

 

 

BSc (Hons), MBChB (Hons), MRCP (UK), FRCA

 

Consultant Anaesthetist, Glasgow Royal Infirmary

Honorary Senior Clinical Lecturer, University of Glasgow

 

Training

  • Graduated from University of Glasgow in 1999

  • Anaesthetic training in West of Scotland 2002-2009

  • Regional Anaesthesia Fellowship Toronto Western Hospital 2008

 

Current Appointment

  • Consultant Anaesthetist, Glasgow Royal Infirmary                              2009-

  • Lead Acute Pain Consultant for Plastic Surgery and Burns unit        2009-

 

Teaching

  • Honorary Senior Clinical Lecturer, University of Glasgow                  2010-

  • Faculty and lecturer on variety of USGRA meetings in Vancouver,    2008-

Toronto, Galway, Qatar, ESRA UK, ESRA Europe, ASRA                   

Helped organise a variety of local, national and international                       2009-

(including ESRA 2013 in Glasgow) Regional Anaesthesia

 meetings and workshops

 

Academic

  • Faculty, F1000 medicine.com

  • Reviewer for variety of journals

  • Actively involved in ongoing research – RCTs involving US guided fascia-iliaca blocks for hip arthroplasty and long term outcome of local vesus regional anaesthesia for arteriorvenous fistulas

  • Multiple peer reviewed publications in a variety of journals (including Reg Anes Pain Med, Br J Anaesth, TRIALS, Clin Ortho Rel Res, Eur J Anaesth), several book chapters (Millers Textbook of Anesthesia, Oxford Textbook of Anaesthesia, Ultrasonography in Interventional Pain Management, Ultrasound Guided Regional Anesthesia and Pain Medicine)

 

Interview with the expert
Sharing experiences...
 



  • We know you love regional anesthesia and ultrasound guidance specially, but can we talk about these techniques like the best anesthetic option for most of our patients? Do you think we get the outcomes we would like to obtain with nerve blocks?

 

   This is a difficult question to answer briefly ! The best anaesthetic option depends on patient co-morbidities, the nature of surgery and obviously patient preference also. It is well documented that analgesia and related side effects such as PONV are superior with regional anaesthesia. A very important and interesting question however is whether outcomes such as major morbidity and mortality are reduced by regional compared to general anaesthesia.

 

   Due to the safety of modern anaesthesia and the resultant small numbers of anaesthetic related complications this remains a difficult challenge for the Anaesthetic community to answer. Indeed this would be logistically almost impossible to determine using a randomised trial due to the number of patients required.

 

   Clearly work has been done in this field and one of the more recent retrospective studies for example included almost 400,000 patients undergoing lower limb arthroplasty and although neuraxial anaesthesia was demonstrated to be beneficial (relative risk reduction of 30 day mortality of almost 50%) the ‘number needed to treat’ with neuraxial (rather than general) anaesthesia to prevent one death was approximately 1250 patients. This shows that whilst neuraxial anaesthesia may be superior (there are clearly potential confounding factors in retrospective data) the benefit is actually small.

 

   Further work is therefore required in this interesting field to determine the benefits of regional anaesthesia regarding morbidity and mortality and whether benefits for example are greater in targeted groups of patients – for example those with more co-morbidities.

 

    (Memtsoudis et al. 2013; : 1046-58).

 

 

  • “Primum non nocere”. Sharing with users: Two tips to make your blocks safer.

 

   There is now sufficient evidence that if learning regional anaesthesia then ultrasound improves safety (by reducing vascular punctures, and local anaesthetic toxicity) as well as improving success. It will be much harder to demonstrate (if ever) that nerve injury is reduced using ultrasound although in principle it should reduce direct injury by allowing real time visualisation of the needle tip and the nerve.

 

   When learning with ultrasound, always know where your needle tip is and what you are looking at on the ultrasound screen ! Practice first on phantoms. Ultrasound will not prevent complications if it is used incorrectly.

 

  • Can you talk about the clinical case (related to regional anesthesia) more interesting you have known?

 

   My best regional anaesthesia case was the first one I did by myself as a junior trainee back in 2003. The patient was scheduled for elective hand surgery and had previously had the other hand operated on awake with only a nerve block. She was keen to have the same anaesthetic again but I explained I was by myself and had only performed some analgesic blocks under supervision and had always combined the blocks with a general anaesthetic. I explained I was happy to try however and informed her of the risks (including failure !!) but she was happy with this plan and I performed a successful nerve stimulator guided axillary block.

 

   I know this is not a unique achievement (!) but at that time in my training it was a great feeling that the patient remained awake, was comfortable throughout and delighted with the outcome. I still to this day enjoy upper limb nerve blocks in particular. 

ALAN MACFARLANE MD

 

BSc (Hons), MBChB (Hons), MRCP (UK), FRCA

 

Consultant Anaesthetist, Glasgow Royal Infirmary

Honorary Senior Clinical Lecturer, University of Glasgow