Department of Anaesthesiology, Friedrich Alexander University Erlangen-Nuremberg, Erlangen, Germany
*Corresponding author: Department of Anaesthesiology, Friedrich-Alexander Universität Erlangen-Nuremberg, Krankenhausstrasse 12, D-91054 Erlangen, Germany. E-mail: hubert.schmitt@kfa.imed.uni-erlangen.de
Accepted for publication: December 9, 2003
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Abstract |
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Br J Anaesth 2004; 92: 5926
Keywords: anaesthetic techniques, intravenous; complications, Friedreichs ataxia; neuromuscular block, rocuronium
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Introduction |
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Case reports |
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Physical examination revealed marked kyphoscoliosis. She presented as a normally developed girl with slightly reduced muscle strength. The electrocardiogram showed sinus rhythm, and QRS and T patterns consistent with left ventricular strain. Echocardiography revealed concentric left ventricular hypertrophy without obstruction and with good myocardial function. The pulmonary function tests showed an early restrictive abnormality, the forced vital capacity being 2.2 litres (predicted value 3.6 litres) and the forced expiratory volume in 1 s 2.1 litres (predicted 3.0 litres). Transcutaneous oxygen saturation was 95% with ambient air.
After written informed consent from the parents, the girl was fasted overnight and premedicated orally with dikalium-chlorazepat (a benzodiazepine) 10 mg. After the placement of i.v. access and routine monitors (pulse oximeter, ECG, non-invasive arterial pressure monitoring), pre-oxygenation and administration of glycopyrrolate 0.004 mg kg1 i.v., anaesthesia was induced with propofol 2.5 mg kg1 and sufentanil 0.5 µg kg1. After adequate mask ventilation had been established, the trachea was intubated without muscle relaxation and the lungs were ventilated with oxygen in air. A double-lumen catheter was inserted into the right internal jugular vein and the left radial artery was cannulated. A urinary catheter attached to an hourly measuring chamber was inserted. Anaesthesia was maintained with an i.v. infusion of propofol 100200 µg kg1 min1 and sufentanil 0.010.03 µg kg1 min1, titrated to effect. Volatile anaesthetics were not used. For perioperative antibiotic prophylaxis, cephazolin 2 g was given i.v. Tidal volume and respiratory rates were controlled to keep the arterial carbon dioxide pressure between 35 and 40 mm Hg. A warm forced air device was used to maintain body temperature at 36°C, which was monitored by a bladder probe. A device for intraoperative cell saver blood salvage was set up.
After placing the patient in the prone position on the foam-padded operating table, the patients right arm was prepared for neuromuscular monitoring using acceleromyography (TOF-Watch SX; Organon, Germany). The ulnar nerve was stimulated supramaximally with repeated train-of-four (TOF) stimuli (2 Hz, 0.2 ms duration at 15 s intervals) using surface electrodes placed above the wrist. The transducer was tightly fixed to the distal interphalangeal joint of the thumb. An i.v. infusion and arterial pressure cuff were not inserted in the monitored arm. The TOF monitor was connected to a portable PC for online data recording and processing (TOF-Watch SX Monitor program; Organon, Dublin, Ireland). After calibration and initial signal stabilization of the control response, rocuronium 0.6 mg kg1 was given i.v. over 5 s. After rocuronium administration, the heart rate increased from 75 to 80 beats min1. The time from administration of rocuronium to complete clinical recovery was monitored. In accordance with the Copenhagen Consensus Conference,6 the following time course of neuromuscular block was measured: (i) onset time; (ii) time of recovery of first twitch of the TOF response to 10, 25 and 90%; (iii) recovery index (time between 25 and 75% recovery of first twitch of TOF); and (iiii) recovery time (time between 25% recovery of first twitch and recovery of TOF ratio to 90%). On the request of the surgeons, an incremental dose of rocuronium 0.2 mg kg1 was given 75 min later as T1 had returned to 100% and the TOF to 90%. The response to TOF stimuli after the increment was also recorded. The clinical data are summarized in Table 1. Figure 1 shows the recording of the TOF response to the initial and incremental dose of rocuronium in this patient.
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Patient 2
The second patient was a girl of 12 yr, height 143 cm and weight 26 kg, presenting for the same procedure. Friedreichs ataxia was diagnosed and confirmed by genetic testing at the age of 5 yr. She had undergone adenoidectomy at the age of 3 yr, which was uneventful. Because of progressive scoliosis she had been confined to wheelchair for 2 yr.
Preoperative examination showed a pale girl with a body weight of only 26 kg. She presented with reduced muscle strength and upper limb ataxia. ECG showed sinus tachycardia, and echocardiography revealed early left ventricular hypertrophy with normal left ventricular function. In the past she had had several episodes of tachycardia and therefore took verapamil. Because of limited cooperation, preoperative respiratory function was difficult to measure, but it suggested restrictive lung disease (FEV1 and FVC were 35 and 30% of predicted, respectively). The transcutaneous oxygen saturation in ambient air was 94%.
After written informed consent, the girl was premedicated orally with dikalium-chlorazepat 5 mg. The patient received cephazolin 1 g for antibiotic prophylaxis. The anaesthetic and surgical procedure were the same as for patient 1. As with patient 1, rocuronium 0.6 mg kg1 was given for muscle relaxation as a single bolus. This induced an increase in heart rate from 81 to 85 beats min1. Neuromuscular monitoring was carried out as specified above, and the results are presented in Table 1. The surgical procedure lasted 6 h. The blood loss was estimated at 800 ml and was replaced with one pack of allogenic red blood cells and 330 ml autologous cell-saver salvaged blood together with 2 units of fresh frozen plasma. The girl was haemodynamically stable throughout the procedure. She was then transferred to the intensive care unit and the lungs were ventilated overnight. Further volume replacement with another pack of red blood cells and additional fresh frozen plasma was required. She was weaned from artificial ventilation over 6 h and the tracheal tube was removed 23 h after surgery. The further postoperative course was uncomplicated and she was discharged from hospital on postoperative day 16.
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Discussion |
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Friedreichs ataxia is a rare, recessively inherited disease with a variety of causes for its pathogenesis. Recent advances in basic research have revealed a mutation in the gene that encodes the mitochondrial protein frataxin as the underlying pathological cause.7 Reduction in frataxin protein production leads to mitochondrial iron accumulation with impaired mitochondrial respiratory function.
The main anaesthetic implications of Friedreichs ataxia relate to concomitant myocardial problems and the administration of neuromuscular blocking drugs. Early reports of hyperkalaemia after administration of succinylcholine to patients with disorders resulting in denervated muscle suggest that it is preferable to avoid depolarizing muscle relaxants in these patients. There are only a few reports of the use of non-depolarizing muscle relaxants in patients with Friedreichs ataxia. Though an early case report showed hypersensitivity to tubocurarine,2 later anecdotal reports described a normal or near-normal response to various non-depolarizing neuromuscular blocking drugs (tubocurarine, atracurium, vecuronium).35 In all the case reports, anaesthesia was supplemented with volatile anaesthetics (isoflurane, enflurane or halothane), agents known for their enhancing effect on neuromuscular block, which can result in prolonged recovery. Only one published report gives complete details of neuromuscular monitoring after administration of atracurium.5
A bolus of rocuronium 0.6 mg kg1 has an onset time of approximately 90 s and an intermediate clinical duration (T25) of about 25 min, with a wide individual range. Though the clinical duration (T25) differed markedly between our two patients (44 and 24 min for patients 1 and 2, respectively; Table 1), the data are within the range reported in children without neuromuscular disease.8 9 The time course of neuromuscular block and recovery in the two patients confirms the report by Mouloudi and colleagues, who found normal recovery data after atracurium in a woman with Friedreichs ataxia. However, as a result of the administration of a different chemical type of neuromuscular blocking drug by these workers and the supplementary use of isoflurane in the earlier report, comparison with our report is of limited use. The recovery indexes in patient 1 (12 min) and patient 2 (13 min) are comparable to data from patients without Friedreichs ataxia, indicating normal pharmacokinetics in these patients.
Comparison of neuromuscular block data in patients with neuromuscular disease is difficult. In addition to a comparable study design with respect to anaesthesia and drug dose, the neuromuscular monitoring techniques, such as the method of measurement, frequency of stimulation and the site of neuromuscular monitoring, are important. All these factors may influence evoked responses to electrical stimuli. In our investigation neuromuscular monitoring was performed using acceleromyography. We chose acceleromyography because of its ease of use compared with bulky mechanomyography equipment during a procedure in which the patient was in the prone position compared with the fairly bulky equipment of mechanomyography. Another option would have been the use of electromyography. Though an investigation in children without neuromuscular disease showed the superiority of acceleromyography compared with electromyography, monitoring recovery from residual neuromuscular block in patients with Friedreichs ataxia is not well described.10
In contrast to reported cases where volatile anaesthetics were administered, we chose an anaesthetic technique based on propofol and sufentanil titrated to effect without any inhalational agent. This anaesthetic technique, together with adequate fluid replacement, enabled us to avoid major changes in arterial pressure. Both patients had left ventricular hypertrophy without outflow obstruction, a common finding in patients with Friedreichs ataxia.11 As both girls had normal left ventricular function, no other anaesthetic measures were required during surgery.
In summary, the successful anaesthetic management of two children with Friedreichs ataxia scheduled for major orthopaedic surgery is reported. The response to a bolus of rocuronium 0.6 mg kg1 was comparable to its effect in children without neuromuscular disease, although a greater number of patients is required to confirm these findings. We recommend accurate assessment of neuromuscular block throughout anaesthesia in patients with Friedreichs ataxia.
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References |
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