Ryuichi Abe

Assessment of intraoperative motor evoked potentials for predicting postoperative paraplegia in thoracic and thoracoabdominal aortic aneurysm repair

PurposeMonitoring motor evoked potentials (MEPs) has been recognized as a highly reliable method to detect intraoperative spinal cord ischemia (SCI) in aortic repair. However, the data regarding the sensitivity and specificity of MEPs for predicting postoperative paraplegia are limited. We retrospectively assessed the value of intraoperative MEP amplitudes for predicting postoperative paraplegia.MethodsThe medical records of 44 patients were reviewed. A train-of-five stimulation was delivered to C3–C4, and MEPs were recorded from the abductor pollicis brevis and the tibialis anterior muscles. The cutoff point for detecting SCI was set at 75% decrease of the baseline MEP. Receiver operating characteristic curves were applied at various cutoff points.ResultsThree patients (6.8%) had postoperative paraplegia. The minimum MEP during surgery had 100% sensitivity and 64.9% specificity in predicting paraplegia, and the MEP at the end of surgery had 66.7% sensitivity and 78.0% specificity in predicting paraplegia: only 1 patient, who had borderline paraplegia (right monoparesis), showed a false-negative result. Receiver operating characteristic curves indicated that adequate cutoff points for the minimum MEP during surgery and for the MEP amplitude at the end of surgery were a 75–90% decrease and a 64–75% decrease of the baseline MEP, respectively.ConclusionMonitoring MEPs had relatively high sensitivity and acceptable specificity, with the cutoff point set at 75% decrease of the baseline MEP, for predicting paraplegia and paraparesis. Because of the small sample in our study, further investigations would be necessary to investigate an adequate cutoff point that could predict postoperative paraplegia.

Tracheal intubation by trainees does not alter the incidence or duration of postoperative sore throat and hoarseness: a teaching hospital-based propensity score analysis

BACKGROUND Postoperative throat complications, such as sore throat and hoarseness, are frequent complications of tracheal intubation. To assess whether severity of throat complications is related to the experience of physicians performing tracheal intubation, we compared the incidence and duration of postoperative sore throat and hoarseness and patient satisfaction between tracheal intubation performed by trainees and experienced consultant anaesthetists. METHODS This is a retrospective review of an institutional registry containing records of 21 606 patients undergoing general anaesthesia and was conducted with ethics board approval. All tracheal intubations by trainees were performed under the supervision of consultant anaesthetists. To avoid channel bias, the propensity score analysis was used to generate a set of matched cases (intubations by trainees) and controls (intubations by anaesthetists), yielding 3465 (sore throat) and 3267 (hoarseness) matched patient pairs. The incidence and sustained rate of symptoms were compared as primary outcomes. We also compared patient satisfaction with perioperative care. RESULTS After propensity score matching, there was no difference between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists in the incidences of sore throat (32.9 vs 32.6%, P=0.84) or hoarseness (35.8 vs 35.2%, P=0.60). Odds ratios and 95% confidence intervals for tracheal intubation by trainees were 1.01 (0.91-1.12) for sore throat and 1.03 (0.93-1.14) for hoarseness. The rates of sustained sore throat and hoarseness over the course were low (P=0.85 and P=0.67, respectively). Hazard ratios and 95% confidence intervals for tracheal intubation by trainees were 0.99 (0.94-1.05) for sustained sore throat and 0.99 (0.93-1.05) for sustained hoarseness. Patient satisfaction did not differ between matched groups (P=0.66 and P=0.83). CONCLUSIONS Tracheal intubation by trainees under the supervision of consultant anaesthetists did not worsen the postoperative airway outcomes, such as sore throat and hoarseness.

Evaluation of the applicability of sevoflurane during post-tetanic myogenic motor evoked potential monitoring in patients undergoing spinal surgery

PurposeRecent evidence has indicated that post-tetanic motor evoked potentials (p-MEPs) can be used to improve the reliability of the monitoring of motor function during spinal surgery. However, data on p-MEP monitoring are limited to those in subjects under propofol anesthesia. The present study was conducted to assess the applicability of sevoflurane during p-MEP monitoring in patients undergoing spinal surgery.MethodsThirty-five patients undergoing spinal surgery under sevoflurane anesthesia were enrolled in the study and classified as being without preoperative motor deficits (n = 25) or with preoperative motor deficits (n = 10). For conventional MEP (c-MEP), transcranial train-pulse stimulation was delivered and the compound muscle action potentials were bilaterally recorded from the abductor pollicis brevis, abductor hallucis, tibialis anterior, and soleus muscles. For p-MEP, tetanic stimulation (50 Hz, 50 mA stimulus intensity) for 5 s was applied to the bilateral median and left tibial nerves 1 s prior to transcranial stimulation.ResultsThe amplitudes of p-MEP were significantly higher in all muscle recording sites than those of c-MEP in patients without motor deficits, whereas these amplitudes were significantly higher in only four of the eight muscles in patients with motor deficits (P < 0.05). The success rates of c-MEP and p-MEP recording were 48% and 64%, respectively, in patients without motor deficits and 30% and 60%, respectively, in patients with motor deficits. There were no statistically significant differences in success rates between c-MEP and p-MEP recording.ConclusionAlthough the application of tetanic stimulation prior to transcranial stimulation did not significantly increase the success rates of MEP recording, it significantly enlarged MEP amplitude under sevoflurane anesthesia in patients without preoperative motor deficits.

Evaluation of posttetanic motor evoked potentials--the influences of repetitive use, the residual effects of tetanic stimulation to peripheral nerve, and the variability.

Background Recently, we developed a new technique to augment myogenic motor evoked potentials (MEPs), called as posttetanic MEPs (p-MEPs), in which tetanic stimulation is applied to peripheral nerve before transcranial stimulation. However, the data on p-MEPs are limited. This study was conducted; (1) to evaluate the influences of repetitive use of p-MEPs on p-MEP amplitudes, (2) to evaluate the residual effects of use of p-MEPs on subsequent conventional MEPs (c-MEPs), and (3) to compare the variability of p-MEPs with that of c-MEPs. Methods Sixty patients under propofol/fentanyl anesthesia with partial neuromuscular blockade were enrolled. For p-MEP measurements, tetanic stimulation was applied to posterior tibial nerve 1 second before transcranial stimulation. In study 1, p-MEPs were repetitively recorded with intervals of 10 or 60 seconds. In study 2, the amplitudes of c-MEPs recorded 15, 30, 60, and 120 seconds after p-MEP recordings were compared with those of control. In study 3, the coefficients of variation of c-MEP and p-MEP responses were compared. Results The repetitive use of p-MEP with an interval of 10 seconds, but not 60 seconds, induced a significant reduction of p-MEP amplitude. Amplitudes of c-MEP were significantly increased when applied within 60 seconds after p-MEP recordings. The coefficient of variations of p-MEPs was similar to those of c-MEPs. Conclusions The results indicated that the amplitudes of p-MEP and c-MEP might be affected when applied with a short interval after p-MEP recording.

Airway management with the laryngeal tube in rabbits

The rabbits oropharyngeal anatomy complicates the use of endotracheal intubation for airway management during surgical procedures. To determine if the laryngeal tube is useful for airway management in rabbits, the authors applied the device and evaluated its efficacy to ventilate the lungs. The laryngeal tube was inserted blindly and without difficulty in six healthy male New Zealand White rabbits; all of the rabbits were ventilated adequately with and without neuromuscular blockade. The authors conclude that the laryngeal tube can be used as an alternative means of airway management in rabbits.

Use of a laryngeal mask airway to stop a supraglottic air leak which prevented adequate ventilation via a tracheostomy in a patient with cerebral palsy and pneumonia.

We report an adolescent developing ventilation failure due to supraglottic air leakage with the use of an uncuffed hand-made tracheal tube fit to her tracheobronchial deformity. To eliminate the supraglottic air leakage, a size 2.5 laryngeal mask airway (LMA) was inserted into the oral pharynx. Most of air leakage arose from the LMA. Supraglottic air leakage was not detected under mandatory mechanical ventilation following sealing of the 15-mm connector of the LMA with a piece of tape, and the respiratory condition of the patient gradually improved. The combination of a hand-made Y-shaped tube and the LMA was useful in restoring adequate ventilation. In conditions where air leaks through the glottis during mechanical ventilation interfere with adequate ventilation or the maintenance of airway pressure, the use of an LMA may be adequate to stop or significantly decrease the leak.

Is an urban legend true in the teaching hospital that “you will get hurt if you go to hospital at the beginning of the fiscal year”?

An urban legend that “you will get hurt if you go to hospital at the beginning of the fiscal year” is in circulation, because people in general suppose that inexperienced newcomers start to work at clinical practice during that time period. We tried to determine whether this urban legend was true or not by using data from our operation management system. We retrospectively conducted a study to investigate whether the number of cannulation failures, which was used as an index of patient disadvantages at clinical practice, could be affected by the volume of residents in clinical participation. The number of insertion trials per case was not prominent in the first month of the fiscal year. However, the number of insertion trials per case increased in proportion to the average number of residents per day. It seems that there was no evidence to support the urban legend that “you will get hurt if you go to hospital at the beginning of the fiscal year.” However, our results suggest that rather than an urban legend, we are now confronting the fact that patients may suffer from medical disadvantages in the teaching hospitals.

44. Evaluation of the results of motor evoked potentials monitoring during craniotomy

while the potentials in the long head of left biceps femoris were normal. Four months later, he developed left drop foot; NCS revealed low amplitudes in left peroneal CMAP by peroneal nerve stimulation and left sural nerve sensory action potential (SNAP). The left gluteus medius was not weak but showed denervation potentials in EMG. Presently, he showed marked muscle atrophy, sensory loss and occasional neuralgia in the left L5 and S1 segments. CMAPs and SNAPs were all absent in the left leg in NCS. Cerebrospinal fluid (CSF) analysis showed 7.0 cells/ll and elevated protein level. MRI revealed swelling in left L4–S2 nerve roots. A biopsy specimen of the left sural nerve demonstrated marked loss of myelinated and unmyelinated fibers. A left S1 nerve root biopsy specimen demonstrated T-lymphocyte infiltration within the roots and ganglia and root sheath thickening. CSF lymphocyte analysis later revealed IgH rearrangement and atypism, suggesting a diagnosis of neurolymphomatosis.