Seizures associated with local anaesthetic intoxication

Abstract

Editor—We are interested in the study by Griffiths and colleagues1Griffiths JD Barron FA Grant S Bjorksten AR Hebbard P Royse CF Plasma ropivacaine concentrations after ultrasound-guided transversus abdominis plane block.Br J Anaesth. 2010; 105: 853-856Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar which has relevance to a recent case we encountered. A 59-yr-old patient with chronic liver disease was admitted for an acute episode of encephalopathy after an incarcerated inguinal hernia. The patient had Child’s grade C cirrhosis with coagulopathy and chronic ascites treated with regular paracentesis. We elected to undertake surgery for the inguinal hernia repair using a locoregional technique (LA). We performed an ultrasound-guided transversus abdominis plane (TAP) block (TAPB) with 30 ml ropivacaine 7.5% injection (3 ml kg−1). Fifteen minutes later, the patient had seizures. We immediately injected 200 ml (3 ml kg−1 20% Intralipid solution). It produced a rapid neurological improvement. The plasma ropivacaine concentration at the time of the seizures was 2.8 µg ml−1. Neurological symptoms have been shown to occur at a mean plasma venous concentration of 2.2 µg ml−1.2Knudsen K Beckman Suurkla M Blomberg S Sjvall J Edvardsson N Central nervous and cardiovascular effects of i.v. infusions of ropivacaine, bupivacaine and placebo in volunteers.Br J Anaesth. 1997; 78: 507-514Abstract Full Text PDF PubMed Scopus (792) Google Scholar In our case report, LA intoxication was confirmed. Surgery was possible 30 min after the seizures. The patient was transferred to the intensive care unit. Convulsions complicating TAPB had not previously been described. We used a dose of ropivacaine within the normal range (3 ml kg−1),3Abdallah FW Chan VW Brull R Transversus abdominis plane block: a systematic review.Reg Anesth Pain Med. 2012; 37: 193-209Crossref PubMed Scopus (176) Google Scholar and injected the LA with repeated negative aspiration and ultrasound control. The 15 min delay between injection and onset of seizure was too long for it to be due to direct injection. One of the hypotheses was relative overdose in our patient in relationship with cirrhosis. Pharmacokinetics of most local anaesthetic drugs is altered by poor liver function and associated alterations in circulation and body fluids. In end-stage liver dysfunction, the clearance of ropivacaine was found to be about 60% lower than that in healthy volunteers, but interestingly, plasma concentrations were similar. The latter finding may depend on increased volumes of drug distribution at the steady state (Vdss) of ropivacaine. Even in end-stage liver dysfunction, α-1 acid glycoprotein is synthesized and thus provides some protection against LA toxicity.4Rosenberg PH Veering BT Urmey WF Maximum recommended doses of local anesthetics: a multifactorial concept.Reg Anesth Pain Med. 2004; 29: 564-575Crossref PubMed Google Scholar In patients with hepatic dysfunction, single-dose blocks can usually be performed safely with normal doses of the LAs.4Rosenberg PH Veering BT Urmey WF Maximum recommended doses of local anesthetics: a multifactorial concept.Reg Anesth Pain Med. 2004; 29: 564-575Crossref PubMed Google Scholar As large doses of LAs are injected in TAPB, systemic toxicity of the LA, as a result of absorption into the circulation, should always be considered. A TAPB can potentially cause systemic toxicity of LAs.5Kato N Fujiwara Y Harato M et al.Serum concentration of lidocaine after transversus abdominis plane block.J Anesth. 2009; 23: 298-300Crossref PubMed Scopus (83) Google Scholar The vascularity (density of capillaries) and LA binding to the tissues influence the initial rate of absorption into the circulating blood. Cirrhotic patients have a hypervascularization of the abdominal wall after portal hypertension. They can have poor synthesis of binding proteins.4Rosenberg PH Veering BT Urmey WF Maximum recommended doses of local anesthetics: a multifactorial concept.Reg Anesth Pain Med. 2004; 29: 564-575Crossref PubMed Google Scholar Griffiths and colleagues showed that a dose of 3 mg kg−1 may be excessive in some patients. However, they believed that clinically important toxicity with this technique is infrequent.1Griffiths JD Barron FA Grant S Bjorksten AR Hebbard P Royse CF Plasma ropivacaine concentrations after ultrasound-guided transversus abdominis plane block.Br J Anaesth. 2010; 105: 853-856Abstract Full Text Full Text PDF PubMed Scopus (146) Google Scholar Toxicity can occur. In fact, our case report suggests that we should reduce LA dose in the case of specific medical conditions such as Child’s C cirrhosis. None declared.