Safety of nitrous oxide administration in patients with Charcot-Marie-Tooth disease

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Abstract

Nitrous oxide is routinely administered to children and adults with Charcot-Marie-Tooth disease (CMT) as an anaesthetic for procedures such as nerve conduction studies and maintenance for general anaesthesia. However it is listed as a ‘moderate to significant’ risk of potential toxicity and worsening neuropathy in people with CMT by the CMT Association (USA), CMT Association of Australia, CMT International (Canada) and CMT United Kingdom. We performed a systematic review focussing on the use of nitrous oxide in patients with CMT to help clarify its safety. This identified 11 studies reporting 41 exposures to therapeutically inhaled nitrous oxide as maintenance for general anaesthesia with no reports of adverse effects or worsening of CMT neuropathy. In the absence of a single case in the literature reporting worsening neuropathy in CMT patients receiving nitrous oxide, this review provides good evidence that nitrous oxide should be considered a safe agent for use in children and adults with CMT.

Introduction

Charcot-Marie-Tooth disease (CMT) in all its forms is the most common inherited peripheral neuropathy in humans, with a total prevalence rate of 1 in 2500 [1]. A list of potential medications to avoid in CMT is maintained by the CMT Association (USA), CMT Association of Australia, CMT International (Canada) and CMT United Kingdom. In particular, nitrous oxide used in children and adults as an anaesthetic for procedures such as nerve conduction studies and maintenance for general anaesthesia is cited as a ‘moderate to significant’ risk of potential toxicity and worsening neuropathy in people with CMT. This is also stated in a recent literature review and analysis of the CMT North American Database (209 respondents) whereby nitrous oxide exposure was reported to exacerbate CMT-related neuropathy in three of six cases (50% of reported exposures) [2].

While the ‘Medical Alert’ on the CMT Association (USA) website (http://www.charcot-marie-tooth.org/med_alert.php) cautions nitrous oxide use, especially with inhalation abuse leading to Vitamin B12 deficiency, it is unclear as to the level of risk in others with CMT where there is far less exposure. Since these ‘Medical Alert’ lists are commonly accessed by patients, treating physicians and the public to assess risk of medication-induced side effects in CMT, we performed a systematic review of the literature focussing on the use of nitrous oxide in patients with CMT to help clarify its safety.

Section snippets

Methods

We performed an Ovid literature search of the databases PREMEDLINE, MEDLINE (January 1966 to October 2007) and EMBASE (January 1980 to October 2007). The search strategy was refined by using various permutations of the terms “Charcot Marie Tooth Disease” or “Hereditary Motor Sensory Neuropathy” and included the keyword “nitrous”. The search was not restricted in language or type of study. All abstracts were reviewed and full text articles were obtained for all studies that reported the use of

Results

The initial literature review identified 28 papers (including the study by Weimer and Podwall [2]) of which 11 reported the use of inhaled nitrous oxide in patients with CMT [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15]. An additional two papers were identified from reference lists [16], [17] which provided less specific information on general anaesthesia in CMT patients. The initial 11 papers were mainly individual cases and two small case series. In the two case series the

Discussion

We were unable to find any reports of worsening of CMT neuropathy associated with therapeutically inhaled nitrous oxide. Weimer and Podwall were also unable to identify any cases of worsening of CMT neuropathy with nitrous oxide in their literature search [2]. However, they only searched for positive cases of nitrous oxide exposure and worsening of neuropathic symptoms in CMT and only searched the MEDLINE database. Weimer and Podwall [2] investigated the relationship between a number of

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