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Even this paper is very speculative Ray; fitting eight minutes after cuff deflation doesn't sound like local toxicity to me. There was a long tourniquet time so acidosis is also possible although again, the long interval from cuff deflation makes this less likely. I think the authors were just hoping it was a prilocaine fit so they could report it as a rare complication! Adrian ----- Original Message ----- From: "Ray McGlone" <[log in to unmask]> To: <[log in to unmask]> Sent: Monday, September 30, 2002 9:04 PM Subject: Re: Bier's Block > Adrian, > > I like you have never had a problem with prilocaine over the years. I can > only find one case report of fitting once the cuff was released (see below). > This must be 1 case in hundreds of thousands in the world over the years. > > Source > Anaesthesia. 49(7):642-3, 1994 Jul. > > > Generalised Convulsions after intravenous regional anaesthesia with > prilocaine > > We wish to report an unusual complication associated with the use of > prilocaine. A healthy 47-year-old man (55 kg, 162 em) was scheduled for > removal of two screws in his right ankle under intravenous regional > anaesthesia (IVRA). He was premedicated with pethidine 40 mg and > promethazine 20 mg intramuscularly 60 min before starting IVRA. After > exsanguination of the right leg, IVRA was performed with prilocaine 4 > mg.kg-' injected over 2 min. The cuff was deflated 50 min after start of > IVRA blood pressure and heart rate were stable and Spo, 98%. Eight min after > deflation of the cuff generalised convulsions occurred. Ventilation was > immediately controlled via a face mask with an Fio. of 1.0 and thiopentone > given. The convulsions stopped completely. but some ventricular > extrasystoles and bigeminy were noticed for 2-3 min. The patient recovered > completely 17 min after the appearance of the convulsions. Unfortunately, > blood samples for plasma concentrations of prilocaine were not collected. > Electrolytes and blood glucose measured after the event were normal. An EEG > was performed which showed no epileptic focus, but a posttraumatic > irritative zone with very little activity in an area close to a suspected > old temporal fracture. CT scan did not show any abnormality and his > neurological status was normal. The patient confirmed a head injury in his > childhood followed by occasional episodes of dizziness, but denied any > convulsions. He left the hospital on the second postoperative day; no > medication was required and he had no complaints. > > Although plasma prilocaine levels were not measured, we still consider that > the principal cause of the convulsions was the release of prilocaine into > the blood stream at the time of the tourniquet's deflation. The convulsions > appeared at a time after cuff deflation when plasma levels of prilocaine are > the highest [1, 2]. > > Promethazine can bind to H2 recaptors in the CNS and stimulate or depress > it. Pethidine. is predominantly a u-agonist and it exerts its chief > pharmacological actions on the CNS and in toxic doses sometimes causes CNS > excitation, characterised by tremors, muscle twitches and seizures. These > symptoms are usually due to an accumulation of its metabolite norpethidine. > An association with promethazine can slow the metabolism of pethidine, and > reinforce the sedation effect. Although the patient had been fasting for 12 > h, hypoglycaemia is an unlikely cause of convulsions. We think therefore it > is reasonable to consider that the convulsions were due to prilocaine even > if this drug is considered as one of the safest local anaesthetics for 1VRA > [3, 41. > > Given its efficacy by the intravenous route and the low > > incidence of thrombophIebitis, prilocaine appears to be the most suitable of > the drugs available for 1VRA [51. Comparison of prilocaine and lignocaine > after intravenous injection showed that the plasma concentration of > prilocaine was far lower than for lignocaine and that a large quantity of > prilocaine is extracted by the lungs on the first pass [61. Similar results > are reported when plasma levels of prilocaine and lignocaine are compared > after release of the cuff during IVRA [71. Lack of correlation between > plasma concentration of local anaesthetics and presence or severity of > symptoms was demonstrated in several studies[ 1, 81. In one of these, > although a dose of prilocaine of only 3 mg.kg-' was used, mild CNS symptoms > (dizziness, lightheadedness and auditory disturbances) were observed after > cuff deflation, 20 min after injection [81. In our case, an EEG a few hours > after the event showed a small irritative inactive zone in the temporal > area, but no epileptic focus. We have been unable to find any evidence to > support the hypothesis that a previous head injury will lower the threshold > for convulsions due to local anaesthetics. To our knowledge, this is the > first case report of' generalised convulsions after an otherwise uneventful > IVRA with prilocaine 4 mg.kg-'. We presented this case to make clinicians > aware of the fact that generalised seizures can appear even after an > uneventful IVRA with this dose of prilocaine and that recommendations for > monitoring. and availability of resuscitation equipment must be adhered to > even when using prilocaine in 'safe' dosages for 1VRA. > > University ' r Hospital of Basel, C. KERN > Basel, Switzerland > Universit ' r Hospital of'Genei,a, Z. GAMULIN > Geneva, Switzerland > > > ----- Original Message ----- > From: "Adrian Fogarty" <[log in to unmask]> > To: <[log in to unmask]> > Sent: Monday, September 30, 2002 7:00 PM > Subject: Re: Bier's Block > > > > ----- Original Message ----- > > From: "Stephen Hughes" > > > As for bier's blocks, I have never seen one because of the mythology > > surrounding them and the lack of prilocaine. Would you believe that? > > > > You could always do a few weeks here in Hampstead, Stephen, and we'll show > > you a few Bier's blocks. You'll have to drop the 'Arlow accent however > > (sorry, I know you've been perfecting it over the last four years). > > > > Steve Meek wrote: > > > Now at Frenchay using prilocaine 1% diluted down to 40mls (0.5% without > > problems) > > > > Yes, I dilute 20mls of 1% with 20mls of water to produce 40mls of 0.5%. I > > presume saline could be used instead. > > > > > I am sure prilocaine is safer than lignocaine and agree with Ray that it > > is then a safe SHO procedure: staring patients, 2 doctors being present > etc > > is unnecessary > > > > I agree but haven't quite delegated this to SHOs yet. However all of ours > > are first years who are now less experienced than ever! I personally don't > > starve or monitor these patients, and I don't use second lines or second > > doctors either. Am not convinced I need to as I haven't seen any problems > > after 12 years' use. Does anyone know, is there any risk of significant > > morbidity using prilocaine? And I've never needed supplemental analgesia > > Ray! > > > > Adrian Fogarty > >