Relationship between pulse pressure variation and stroke volume variation with changes in cardiac index during hypotension in patients undergoing major spine surgeries in prone position - A prospective observational study.

Background and Aims: Dynamic indices such as pulse pressure variation (PPV) and stroke volume variation (SVV) are better predictors of fluid responsiveness than static indices. There is a strong correlation between PPV and SVV in the prone position when assessed with the fluid challenge. However, this correlation has not been established during intraoperative hypotension. Our study aimed to assess the correlation between PPV and SVV during hypotension in the prone position and its relationship with cardiac index (CI). Material and Methods: Thirty patients aged 18-70 years of ASA class I-III, undergoing spine procedures in the prone position were recruited for this prospective observational study. Hemodynamic variables such as heart rate (HR), mean arterial pressure (MAP), PPV, SVV, and CI were measured at baseline (after induction of anesthesia and positioning in the prone position). This set of variables were collected at the time of hypotension (T-before) and after correction (T-after) with either fluids or vasopressors. HR and MAP are presented as median with inter quartile range and compared by Mann-Whitney U test. Reliability was measured by intraclass correlation coefficients (ICC). Generalized estimating equations were performed to assess the change of CI with changes in PPV and SVV. Results: A statistically significant linear relationship between PPV and SVV was observed. The ICC between change in PPV and SVV during hypotension was 0.9143, and after the intervention was 0.9091 (P < 0.001). Regression of changes in PPV and SVV on changes in CI depicted the reciprocal change in CI which was not statistically significant. Conclusion: PPV is a reliable surrogate of SVV during intraoperative hypotension in the prone position.

A randomized clinical trial comparing the King Vision (channeled blade) and the CMAC (D blade) videolaryngoscopes in patients with cervical spine immobilization.

Background and Aims: Cervical spine immobilization renders direct laryngoscopy difficult. The CMAC D blade and the channeled blade of the King Vision videolaryngoscopes, have both been used for difficult airway management. Our hypothesis is that the channeled blade of the King Vision would be superior to the CMAC D blade in terms of ease of intubation. We tested this hypothesis in a randomized comparison of the two videolaryngoscopes in patients with simulated cervical spine immobilization. Material and Methods: Hundred patients with no anticipated airway difficulty were randomly allocated to two groups after obtaining informed written consent. Following induction, manual inline stabilization (MILS) was applied to simulate a cervical spine injury and immobilzation. Patients were intubated with either of the two videolaryngoscopes. Time for visualization of the glottis, procedural time, intubation difficulty scale (IDS), and hemodynamic response were recorded. Results: The time to visualize the glottis was shorter in the CMAC D group as compared to the King Vision group (P < 0.001). The incidence of external laryngeal manipulation was less in the King Vision group (P < 0.001). The ease of intubation was superior in the King Vision group, based on the IDS (P < 0.001). The haemodynamic response was similar between the groups. Conclusion: King Vision channeled videolaryngoscope was difficult to introduce into the mouth of the patient during laryngoscopy. Once introduced into the mouth, the time for intubation was less and less external laryngeal manipulation maneuvers were performed to achieve successful intubation. The ease of endotracheal intubation was superior for the King Vision videolaryngoscope. The King Vision videolaryngoscope with proper tranining, could be a safe and portable alternative in patients with cervical spine immobilization.

Usefulness of ultrasound-guided measurement of minimal transverse diameter of subglottic airway in determining the endotracheal tube size in children with congenital heart disease: A prospective observational study.

INTRODUCTION: The search for an accurate and predictable method to estimate the endotracheal tube (ETT) size in pediatric population had led to derivation of many formulae. Of this, age-based formulae are the most commonly used. Studies have shown that minimal transverse diameter of subglottic airway (MTDSA) measurements using a high-frequency probe improves the success rate of predicting the airway diameter to about 90%. We did a prospective observational study using MTDSA as the criteria to select the size of ETT in children with congenital heart disease. METHODS: In this prospective observational study, 51 children aged from 1 day to 5 years, scheduled for cardiac surgery, were enrolled for this study. The ETT size was guided solely based on the MTDSA. Leak test was used to determine the best-fit ETT size. RESULTS: Data from 49 patients were analyzed. Agreement between the ETT determined by MTDSA and that predicted by Cole's age-based formulas with the best-fit ETT size was analyzed using a Bland-Altman plot. CONCLUSION: Age-based formula showed poor correlation (27.5%) compared to MTDSA (87.8%) in predicting the best-fit ETT. We observed that pediatric patients with congenital heart disease need a larger sized ETT as compared to what was predicted by age-based formula. Using ultrasound MTDSA measurements to guide selection of ETT size is a safe and accurate method in pediatric cardiac population.

Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications.

Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo-hydrothermal (S-H) method using water-acetonitrile-ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform (FT)-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380-580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm(-1). Cytotoxicity and haemocompatibility investigations of these ZnS microspheres revealed its biocompatibility. ZnS microspheres, along with biological cell lines, were giving visible light emission and could be used for bioimaging applications.

Cortical excitability in drug naive juvenile myoclonic epilepsy.

PURPOSE: To evaluate the effect of diurnal variability on cortical excitability using single pulse transcranial magnetic stimulation (TMS), in drug naive patients with juvenile myoclonic epilepsy (JME) and to look for any differences in cortical excitability between males and females. METHODS: Thirty drug-naive patients with JME and 10 healthy controls were studied. Resting motor threshold (RMT), motor evoked potential (MEP), the duration of central motor conduction time (CMCT) and cortical silent period (CSP) were measured, twice, first early in the morning and again in the afternoon of the same day. RESULTS: Diurnal variation with higher evening values of CMCT and CSP were observed in the control group. In the study group, diurnal variation in RMT, CMCT and CSP was found with higher values in the morning than in control group. However, only the raised values of CSP [mean, 110.7ms, morning and 96.44ms, evening] were of statistical significance [p=0.005, morning and 0.039, evening] as compared to controls. In the study group, males had higher values of RMT, CMCT and CSP than in females. However, the CMCT in males was lower in the evening study than in females. Further, RMT and morning CMCT was lower in females than in controls. In females, the morning CSP [mean, 100.91ms, morning versus 87.86ms, evening] was significantly prolonged [p=0.017, morning versus 0.221, evening] as compared to controls. CONCLUSION: The study is suggestive of the existence of impaired supraspinal/intracortical inhibitory circuits which may account for the hyperexcitability of the motor system being prominent in the morning among drug naïve patients with JME. In this study, increased activity of cortical inhibitory networks, as evidenced by prolonged cortical silent period existed among drug naïve JME patients, but was found to be significant only in female patients. This may explain the increased seizure susceptibility in this cohort, at this time of the day and an increased manifestation of JME in females.