1 Birmingham, AL, USA 2 Izumo City, Japan
EditorThe repeated neurological deficit noted in the patient described by Sakura and colleagues1 is a matter of concern as the patient appeared to have received tetracaine 10 mg intrathecally followed by two separate doses of 10 ml of mepivacaine 1.5% within 60 min. She developed burning pain on the buttocks and thighs, and sacral numbness lasting for weeks and months, respectively. In the past, local anaesthetic dosages for neuroaxial anaesthesia were limited by their potential for causing decreases in blood pressure or systemic neurotoxicity (somnolence, convulsions). The combined spinalepidural anaesthesia technique was described injecting supplemental doses of a local anaesthetic into the epidural space after a small dose of a similar drug had been administered intrathecally.2 In the case in question, the authors appear to have developed a technique of injecting a full dose of tetracaine followed by, what some may consider as a near full dose of mepivacaine into the peridural compartment, repeating it again within 1 h. As Bernards and colleagues3 have reported, local anaesthetics injected extradurally act by crossing the meningeal barrier, direct neurotoxicity to the nerve roots and cauda equina may occur from excessive dosage or concentration.4 Although the blood pressure did not fall and the patient did not convulse, the neurological deficit experienced by this patient lasting for months suggests direct neurotoxicity upon the distal neural elements contained in the thecal sac.
The so called transient nerve root irritation is not to be taken lightly as, in some cases, it results in permanent neurological deficit, then termed arachnoiditis.5 This impression has been confirmed by Avidan and colleagues,6 who recently reported the radiological diagnosis of enhanced (inflamed and swollen) nerve roots at MRI as demonstrated in Figure 1. Fortunately, most cases do not progress toward the proliferative phase of arachnoiditis when those nerve roots are found clumped and/or adherent to the wall of the meningeal sac (Fig. 2). The relevance of these radiological findings during transient nerve root irritation is the feasibility of treating this condition with corticosteroids and anti-inflammatories, as this window of opportunity may only last from two to three months before gradually evolving into the phase when fibroblasts and collagen deposition result in permanent fibrosis, scarring and adhesions.
|
|
J. A. Aldrete
Birmingham, AL, USA
EditorThank you for the opportunity to reply to Dr Aldrete. He comments on our case report1 that described recurrent pain and persistent hypoaesthesia in the buttocks of a patient after two consecutive Caesarean sections under combined spinal and epidural anaesthesia.
I agree that we should abandon the clinical use of an agent (or combination of agents) that are suspected of being the cause of such a complication. Regarding tetracaine, we became aware of a case of transient neurological symptoms (TNS) after spinal anaesthesia with this local anaesthetic combined with phenylephrine, that was added to prolong its duration.7 We then, performed a prospective study, which confirmed that the vasopressor increased the occurrence of TNS after spinal tetracaine.8 The results led us not to use a vasopressor with a local anaesthetic for spinal anaesthesia.
However, I do not agree with his suggestion that tetracaine should be replaced by bupivacaine in order to avoid this complication. Evidence indicates that, although spinal lidocaine could induce TNS in 40% of cases,5 the incidence of TNS after spinal tetracaine is 13%,8 11 which is similar to that after spinal bupivacaine.11
Dr Aldrete quotes Avidan and colleagues,6 who reported details of magnetic resonance imaging of a patient with TNS after spinal lidocaine. It indicated a local inflammatory process as the possible aetiology for the symptoms, and concluded that TNS in some cases results in permanent neurological deficit. Our case report1 also suggests that TNS may be mediated by the neurotoxic effect of the local anaesthetic. However, case reports do not provide conclusive evidence. The results of a recent animal study by Kishimoto and colleagues12 demonstrated equivalent neurotoxic injury with prilocaine and lidocaine. In contrast, clinical data13 14 showed a considerable difference in the incidence of TNS between the two agents. Thus, we still need to be cautious of drawing such conclusions.
S. Sakura
Izumo City, Japan
References
1 Sakura S, Toyota K, Doi K, Saito Y. Recurrent neurological symptoms in a patient following repeat combined spinal and epidural anesthesia. Br J Anaesth 2002; 88: 1413
2 Torrieri A, Aldrete JA. Spinalepidural needle for combined anesthesia. Acta Anaesthesiol Belg 1986; 30: 656
3 Bernards CM, Hill H. Physical and chemical properties of drug molecules governing their diffusion through the spinal meninges. Anesthesiology 1992; 77: 7506[ISI][Medline]
4 Kubina P, Gupta A, Oscarsson A, et al. Two cases of cauda equina syndrome following spinalepidural anesthesia. Reg Anesth 1997; 22: 44750[ISI][Medline]
5 Hampl KF, Schneider CM, Ummerholder W, et al. Transient neurological symptoms after spinal anesthesia. Anesth Analg 1995; 81: 114853[Abstract]
6 Avidan A, Gomori M, Davidson E. Nerve root inflammation demonstrated by magnetic resonance imaging in a patient with transient neurologic symptoms after intrathecal injection of lidocaine. Anesthesiology 2002; 97: 2578[ISI][Medline]
7 Sumi M, Sakura S, Kosaka Y. Intrathecal hyperbaric 0.5% tetracaine as possible cause of transient neurological toxicity. Anesth Analg 1996; 82: 10767[ISI][Medline]
8 Sakura S, Sumi M, Sakaguchi Y, et al. The addition of phenylephrine contributes to the development of transient neurological symptoms after spinal anesthesia with 0.5% tetracaine. Anesthesiology 1997; 87: 7718[CrossRef][ISI][Medline]
9 Aldrete JA. Anesthetic substances in the spine. In Arachnoiditis: the Silent Epidemic. JA Aldrete (ed). Futuremed: Denver, CO, 2000; 77101
10 Vandam LD, Dripps RD. Exacerbation of pre-existing neurological disease after spinal anesthesia with lidocaine. N Engl J Med 1956; 255: 843[ISI]
11 Freedman JM, Li D-K, Drasner K, et al. Transient neurologic symptoms after spinal anesthesia: an epidemiologic study of 1,863 patients. Anesthesiology 1998; 89: 63341[ISI][Medline]
12 Kishimoto T, Bollen AW, Drasner K. Comparative spinal neurotoxicity of prilocaine and lidocaine. Anesthesiology 2002; 97: 12503[CrossRef][ISI][Medline]
13 Hampl KF, Heinzmann-Wiedmer S, Luginbuehl I, et al. Transient neurologic symptoms after spinal anesthesia: a lower incidence with prilocaine and bupivacaine than with lidocaine. Anesthesiology 1998; 88: 62933[ISI][Medline]
14 de Weert K, Traksel M, Gielen M, Slappendel R, Weber E, Dirksen R. The incidence of transient neurological symptoms after spinal anaesthesia with lidocaine compared to prilocaine. Anaesthesia 2000; 55: 10204[CrossRef][ISI][Medline]