Factors Affecting Transcranial Motor-Evoked Potential Measurements Using Single-Train Stimulation with an Increased Number of Pulses during Adolescent Scoliosis Surgery: A Prospective Observational Study.

Measurement of transcranial motor-evoked potentials (TcMEPs) during scoliosis surgery helps detect postoperative new neurological defects. However, TcMEP interpretation is difficult owing to the influence of intraoperative physiological, pharmacological, and time-related factors as well as stimulation conditions. In this study, we aimed to investigate the effect of the abovementioned factors on TcMEP amplitude using single-train stimulation with an increased number of pulses (STS-INP) during adolescent scoliosis surgery; moreover, we evaluated the complications of TcMEP measurement. We included 50 patients and 706 TcMEP measurements. A total of 1412 TcMEP waveforms were analyzed, each on the bilateral abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles. We estimated the mean difference (95% confidence interval (CI)) and predicted mean difference (95% CI) evaluated using the interquartile range of each factor, based on a mixed-effect model with random intercepts for TcMEP amplitude. The predicted mean differences in TcMEP amplitude were clinically small compared with the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. Using STS-INP during adolescent scoliosis surgery may enable accurate measurement of TcMEP amplitude with neither complications nor the influence of various intraoperative factors.

Acquired laryngomalacia as a cause of post-extubation stridor and extubation failure following craniotomy: a case report.

BACKGROUND: Laryngomalacia is a dynamic airway condition characterized by flaccid laryngeal tissue and inward collapse of supraglottic structures during inspiration. Although it may cause airway obstruction and requires careful management, there have been few reports regarding laryngomalacia after surgery. We report a case of adult-onset laryngomalacia occurred after craniotomy requiring reintubation. CASE PRESENTATION: A 21-year-old man was admitted to the ICU after craniotomy for a cerebellopontine angle tumor. He developed severe stridor immediately after extubation on the postoperative day 2 and required reintubation. On the postoperative day 5, similar episode occurred following re-extubation and fiberoptic laryngoscopy revealed a collapsed epiglottis and left arytenoid into the glottis. A diagnosis of laryngomalacia was made, and he underwent tracheostomy. Laryngomalacia had completely improved; however, bilateral vocal cord paralysis was detected 2 weeks later. CONCLUSIONS: Acquired laryngomalacia should be considered as a possible mechanism of the airway symptoms in a patient with neurological dysfunction.

Effects of ephedrine and phenylephrine on cerebral oxygenation: observational prospective study using near-infrared time-resolved spectroscopy.

It has been reported that cerebral oxygenation (ScO2) measured by near infrared spectroscopy is maintained or increased by treatment with ephedrine, whereas almost all previous reports demonstrated that phenylephrine reduced ScO2. As the mechanism of the latter, the interference of the extracranial blood flow, that is extracranial contamination, has been suspected. Accordingly, in this prospective observational study, we utilized time-resolved spectroscopy (TRS), in which the effect of extracranial contamination is thought to be minimal, and evaluated whether the same result was obtained. We measured the changes in ScO2 as well as the total cerebral hemoglobin concentration (tHb) after treatment with ephedrine or phenylephrine during laparoscopic surgery by using a tNIRS-1 (Hamamatsu Photonics, Hamamatsu, Japan), which is a commercial instrument utilizing TRS. Based on a mixed-effects model with random intercepts for ScO2 or tHb including mean blood pressure, the mean difference and 95% confidence interval were evaluated as well as the predicted mean difference and its confidence interval using the interquartile range of mean blood pressure. Fifty treatments with ephedrine or phenylephrine were done. The mean differences of ScO2 were less than 0.1% and the predicted mean differences were less than 1.1% for the two drugs. The mean differences of tHb were less than 0.02 µM and the predicted mean differences were less than 0.2 µM for the drugs. The changes in ScO2 and tHb after treatments with ephedrine and phenylephrine were very small and clinically insignificant when measured by TRS. Previous reports about phenylephrine may have been affected by extracranial contamination.

Age Difference of the Relationship Between Cerebral Oxygen Saturation and Physiological Parameters in Pediatric Cardiac Surgery with Cardiopulmonary Bypass: Analysis Using the Random-Effects Model.

Recently, monitoring of cerebral oxygen saturation (ScO2) has become widespread in pediatric cardiac surgery. Our previous study reported that mean blood pressure (mBP) was the major contributor to ScO2 throughout cardiac surgery with cardiopulmonary bypass (CPB) in children weighing under 10 kg. We speculated that this result might be attributable to incomplete cerebral autoregulation in such young children. Accordingly, our hypothesis is that the relationship between ScO2 and the physiological parameters may change according to the growth of the children. ScO2 was measured with an INVOS 5100C (Somanetics, Troy, MI). Random-effects analysis was employed with ScO2 as a dependent variable, and seven physiological parameters (mBP, central venous pressure, nasopharyngeal temperature, SaO2, hematocrit, PaCO2, and pH) were entered as independent covariates. The analysis was performed during the pre-CPB, CPB, and post-CPB periods by dividing the patients into two groups: infants (Infant Group) and children who were more than 1 year old (Child Group). The Infant and Child Groups consisted of 28 and 21 patients. In the random-effects analysis, mBP was the major contributor to ScO2 during CPB in both groups. During the pre-CPB period, the effect of mBP was strongest in the Infant group. However, its effect was second to that of SaO2 in the Child Group. During the post-CPB period, SaO2 and mBP still affected ScO2 in the Infant group. However, the dominant contributors were unclear in the Child Group. Cerebral autoregulation may be immature in infants. In addition, it may be impaired during CPB even after 1 year of age.

The Relationships of Cerebral and Somatic Oxygen Saturation with Physiological Parameters in Pediatric Cardiac Surgery with Cardiopulmonary Bypass: Analysis Using the Random-Effects Model.

Recently, tissue oxygenation in pediatric heart surgery is measured by using near-infrared spectroscopy. Monitoring of cerebral oxygen saturation (ScO2) is most common but that of somatic tissue oxygen saturation (SrO2) is also gradually becoming widespread. However, the value of their monitoring is not well established. One of the reasons for this may be that the physiological factors affecting ScO2 and SrO2 have not been sufficiently clarified. Accordingly, we prospectively observed the changes in ScO2 and SrO2 simultaneously throughout cardiac surgery with cardiopulmonary bypass (CPB) in children weighing under 10 kg and evaluated their relationships with physiological parameters by using the random-effects model. ScO2 and SrO2 were measured with an INVOS 5100C (Somanetics, Troy, MI, USA). The random-effects analysis was applied for ScO2 and SrO2, as dependent variables, and seven physiological parameters (mean blood pressure, central venous pressure, rectal temperature, SaO2, hematocrit PaCO2, and pH) were entered as independent covariates. The analysis was performed during the pre-CPB, CPB, and post-CPB periods. Next, the same analysis was performed by dividing the patients into univentricular and biventricular physiological types. Forty-one children were evaluated. Through the whole surgical period, ScO2 correlated strongly with mean blood pressure regardless of the physiological type. On the other hand, the contribution of mean blood pressure to SrO2 was weak and various other parameters were related to SrO2 changes. Thus, the physiological parameters affecting ScO2 and SrO2 were rather different. Accordingly, the significance of monitoring of cerebral and somatic tissue oxygen saturation in pediatric cardiac surgery should be further evaluated.