G. S. Umamaheswara Rao

Evaluation of POSSUM and P-POSSUM scoring systems for predicting the mortality in elective neurosurgical patients.

A simple way of evaluating surgical outcomes is to compare mortality and morbidity. Such comparisons may be misleading without a proper case mix. The POSSUM scoring system was developed to overcome this problem. The score can be used to derive predictive mortality and morbidity for surgical procedures. POSSUM and a modified version P-POSSUM have been evaluated in various groups of surgical patients for the accuracy of predicting mortality. These scoring systems have not been evaluated in neurosurgical patients. Thus, we tried to evaluate the usefulness of POSSUM and P-POSSUM scoring systems in neurosurgical patients in predicting in-hospital mortality. POSSUM physiological and operative variables were collected from all neurosurgical patients undergoing elective craniotomy, from April 2005 to Feb 2006. In-hospital mortality was obtained from the hospital mortality register. The physiological score, operative score, POSSUM predicted mortality rate and P-POSSUM predicted mortality rate were calculated using a calculator. The observed number of deaths was compared against the predicted deaths. A total of 285 patients with a mean age of 38 ± 15 years were studied. Overall observed mortality was nine patients (3.16%). The mortality predicted by the P-POSSUM model was also nine patients (3.16%). Mortality predicted by POSSUM was poor with predicted deaths in 31 patients (11%). The difference between observed and predicted deaths at different risk levels was not significant with P-POSSUM (p = 0.424) and was significantly different with POSSUM score (p < 0.001). P-POSSUM scoring system was highly accurate in predicting the overall mortality in neurosurgical patients. In contrast, POSSUM score was not useful for prediction of mortality.

Hemodynamic changes after administration of mannitol measured by a noninvasive cardiac output monitor.

Mannitol is the most commonly used hyperosmotic agent in neurosurgery. Being an agent that increases intravascular volume by withdrawing water from the brain, it may cause significant changes in stroke volume (SV), cardiac output (CO), systemic vascular resistance and blood pressure. In this study, we monitored the hemodynamic changes in response to a single dose of mannitol by using a noninvasive CO monitorbased on the thoracic electrical bioimpedance technique, in patients undergoing craniotomy. Eleven adult patients undergoing elective craniotomy received mannitol 1.0 g/kg 15 minutes before dural opening. The following hemodynamic variables were recorded: heart rate, systolic blood pressure, diastolic blood pressure, SV, CO, and cardiac index. The measurements were made before the administration of mannitol, at 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, and 45 minutes after the termination of the mannitol infusion. Urine output was measured at 10, 20, 30, 40, 50, 60, 90, and 120 minutes after termination of the mannitol infusion. Heart rate values from 25 to 45 minutes were significantly lower compared with the premannitol values (P<0.05). All the postmannitol systolic blood pressure values were significantly lower than the premannitol value (P<0.05). SV increased significantly for 15 minutes after administration of mannitol (P<0.05). SV at 45 minutes was significantly lower than that from 1 to 30 minutes (P<0.05). Cardiac index also showed a similar change with a significant increase at 1 to 10 minutes and a decrease at 40 to 45 minutes compared with 1 to 15 minutes.The rate of urine secretion was higher during the first 10 minutes (40±15 mL/kg/ h) than during the rest of the study period. The overall fluid balance at the end of 120 minutes was −370±987 mL. In this study using noninvasive measurement of CO by thoracic bioimpedance plethysmography during craniotomy, a single bolus dose of mannitol 1.0 g/kg caused a significant but short duration changes in the hemodynamic variables. The changes in SV, and CO, lasted for only 15 minutes after the infusion.

Sevoflurane and thiopental preconditioning attenuates the migration and activity of MMP-2 in U87MG glioma cells

BACKGROUND Tumor cell migration and diffuse infiltration into brain parenchyma are known causes of recurrence after treatment in glioblastoma (GBM), mediated in part by the interaction of glioma cells with the extracellular matrix, followed by degradation of matrix by tumor cell derived proteases, particularly the matrix metalloproteinases (MMP). Sevoflurane and thiopental are anesthetics commonly used in cancer surgery. However, their effect on the progression of glioma cells remains unclear. The aim of this study was to explore the role of these anesthetics on the migration and activity of MMP-2 in glioma cells. METHODOLOGY Cultured U87MG cells were pretreated with sevoflurane or thiopental and in vitro wound healing scratch assay was carried out to analyze their effect on migration of these cells. Gelatin zymography was carried out to examine the effect of these anesthetics on tumor cell MMP-2 activity using the conditioned media 24 h after pretreatment. Cell viability was analyzed using 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. RESULTS U87MG cells exposed to 2.5% sevoflurane or different concentrations of thiopental significantly decreased migration and activity of MMP-2 compared to control. No effect was seen on the viability of these cells after pretreatment with sevoflurane or thiopental. CONCLUSION/SIGNIFICANCE These results suggest that both sevoflurane and thiopental have inhibitory effect on the migration and MMP-2 activity in glioma cells. Thus, it is important that the choice of anesthetics to be used during glioma surgery takes into account their inhibitory properties against the tumor cells.

Perioperative stroke following anterior cervical discectomy.

We describe a case of postoperative stroke in a patient undergoing anterior cervical discectomy caused by a combination of intraoperative retraction of an atherosclerotic carotid vessel and arterial hypotension.

Additional phenytoin is frequently needed in patients undergoing craniotomy for supratentorial tumour.

EDITOR: Phenytoin is generally prescribed to patients with supratentorial tumours to decrease the risk of seizures. Earlier studies showed that plasma phenytoin concentration may not be in the therapeutic range despite continued therapy [1]. During craniotomy for a supratentorial tumour, an intraoperative loading dose of phenytoin is generally used to prevent postoperative seizures [2,3]. In our institution, it has been common practice not to administer phenytoin intraoperatively. To understand the consequences of our practice of withholding intraoperative phenytoin, we measured perioperative serum phenytoin concentration in a group of patients undergoing supratentorial tumour surgery. We also tried to determine the factors influencing postoperative serum phenytoin concentrations. Twenty-five adult patients (ASA I or II) of either sex, receiving phenytoin for a period not less than 7 days before supratentorial surgery, were studied after institutional approval and informed consent. On the day of surgery, 300 mg of phenytoin was administered either orally or intravenously 4 h before surgery. The anaesthetic technique comprised of induction with thiopentone (5–6 mg kg), tracheal intubation facilitated by a muscle relaxant and maintenance with either isoflurane or propofol. Intraoperative analgesia was provided by fentanyl. Serum phenytoin concentration was measured before induction, immediately after surgery and 24 h after surgery. The assay, performed by a chemiluminescence technique using an Immulite Assay Kit (DPC; Los Angeles, CA, USA), permitted the measurement of total phenytoin concentration. The following parameters were recorded in all patients: duration of anaesthesia and surgery, volume of crystalloids, colloids and blood products administered, volume of urine output and blood loss, and occurrence of immediate postoperative seizures. A repeated-measures analysis of variance (ANOVA) with Bonferroni’s test was used to find out significant differences among the preinduction, immediate postoperative and delayed postoperative serum phenytoin concentrations. Study variables in patients with therapeutic and subtherapeutic concentrations of phenytoin were compared by one-way ANOVA for continuous data and a x-test for categorical variables. Pearson’s test was used to correlate preinduction phenytoin concentration and its decrease in the immediate postoperative period. Logistic regression analysis was used to determine the independent predictors of immediate postoperative subtherapeutic serum phenytoin concentration. A P value of ,0.05 was considered significant. There were 17 male and 8 female patients in the study. Their age was 38 6 12 yr and body weight was 56 6 11 kg. Twelve patients had a preoperative history of seizures. The preinduction serum phenytoin concentration was highly variable among the patients (range 2.5–37.3 mg mL (95% CI 5 9.8– 17.8 mg mL)). Despite continuous medication until the morning of surgery, 11 patients (44%) had a subtherapeutic concentration of serum phenytoin (normal range 10–20 mg mL) in the preinduction sample. Serum phenytoin concentration was significantly lower in the immediate postoperative sample compared with the preinduction sample (9.5 6 7.0 vs. 13.8 6 9.4 mg mL; P , 0.001). The concentration increased significantly in the delayed postoperative sample (11.8 6 8.0 mg mL; P , 0.001). The decrease in phenytoin concentration in the immediate postoperative sample correlated with its preinduction value (P , 0.01; r 5 0.8). Seizures within 24 h of surgery occurred in two patients. Only one of these patients had a preoperative history of seizures. Serum phenytoin concentration was within the therapeutic range (16.3 and 10.4 mg mL) in both the patients. In the immediate postoperative period, serum phenytoin concentration was in a subtherapeutic range in 15 out of the 25 study patients. On univariate analysis, the variables that were significantly different between the therapeutic and subtherapeutic groups were the patient’s gender, preinduction phenytoin concentration, blood loss, blood transfusion, duration of surgery and duration of anaesthesia (Table 1). Of these, preoperative phenytoin level, intraoperative blood transfusion and the duration of surgery/anaesthesia were found to be the independent predictors of low serum phenytoin concentration in the immediate postoperative period (P , 0.05). The value of prophylactic administration of antiepileptic drugs in patients with brain tumours remains controversial. Some authors claim a significant decrease in the incidence of seizures in the Correspondence to: G. S. Umamaheswara Rao, Department of Neuroanaesthesia, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore 560029, India. E-mail: gsuma123@yahoo.com; Tel: 191 8

Effect of propofol anesthesia on resting state brain functional connectivity in Indian population with chronic back pain

Objective: Functional magnetic resonance imaging (fMRI) studies in healthy volunteers have shown alterations in brain connectivity following anesthesia as compared to the awake state. It is not known if the anesthesia-induced changes in brain connectivity are different in a pathological state. This study aims to evaluate changes in the resting state functional connectivity in the brain, after propofol anesthesia, in patients with chronic back pain (CBP). Materials and Methods: Fourteen adults with CBP were included in this prospective study over 6 months. After excluding structural brain pathology, a resting state fMRI was performed in the awake state, and the sequences were repeated after propofol anesthesia. The primary outcome measure was change in resting state connectivity after propofol. Students t-test was performed between the pre and post-propofol sedation data of all patients with total brain volume as covariates of interest. A repeated measures analysis of variance was used to compare pre- and post-propofol changes in cardiorespiratory parameters. Results: There were 8 male and 6 female patients in the study, and the mean age of the study population was 46.9 ± 11.3 years. Propofol sedation resulted in an increased strength of functional connectivity between the posterior cingulate cortex (PCC) and thalamus in patients with CBP, whereas there was a generalized decrease in functional integration within the large scale brain networks. The changes in cardiorespiratory parameters before and after propofol administration were not statistically significant. Conclusion: Strengthening of functional connectivity was seen between PCC and thalamus with decrease in large scale brain networks following propofol anesthesia in patients with CBP. These changes are similar to those previously described in normal volunteers.

Good airway reflexes and normal sensorium do not assure safe tracheal extubation in patients with cerebral hemispheric pathology.

Abstract Following brain injury, return of consciousness and cough reflex are presumed to be associated with safe airway. We describe two patients who had a normal cough reflex, but impaired swallowing, which led to prolonged hospital stay. This report highlights the dissociation between the cough reflex and swallowing function in such patients.

Anesthetic management for foramen magnum decompression in a patient with Morquio syndrome : a case report

Morquio syndrome is a hereditary mucopolysaccharide disorder presenting with an abnormality of the craniocervical junction from childhood. We describe an adult patient who presented with Morquio syndrome who had subglottic narrowing of the airway, restrictive pulmonary disease, and mild mitral regurgitation and trivial aortic regurgitation. The anesthetic management of this patient for atlantoaxial stabilization is presented.

Dynamic local connectivity uncovers altered brain synchrony during propofol sedation

Human consciousness is considered a result of the synchronous “humming” of multiple dynamic networks. We performed a dynamic functional connectivity analysis using resting state functional magnetic resonance imaging (rsfMRI) in 14 patients before and during a propofol infusion to characterize the sedation-induced alterations in consciousness. A sliding 36-second window was used to derive 59 time points of whole brain integrated local connectivity measurements. Significant changes in the connectivity strength (Z Corr) at various time points were used to measure the connectivity fluctuations during awake and sedated states. Compared with the awake state, sedation was associated with reduced cortical connectivity fluctuations in several areas connected to the default mode network and around the perirolandic cortex with a significantly decreased correlation of connectivity between their anatomical homologues. In addition, sedation was associated with increased connectivity fluctuations in the frequency range of 0.027 to 0.063 Hz in several deep nuclear regions, including the cerebellum, thalamus, basal ganglia and insula. These findings advance our understanding of sedation-induced altered consciousness by visualizing the altered dynamics in several cortical and subcortical regions and support the concept of defining consciousness as a dynamic and integrated network.

In reply: is dexmedetomidine really superior to propofol?

1. Banik S, Prabhakar H. Is dexmedetomidine really superior to propofol? J Anesth. 2015. doi:10.1007/s00540-015-2005-0. 2. Sriganesh K, Reddy M, Jena S, Mittal M, Umamaheswara Rao GS. A comparative study of dexmedetomidine and propofol as sole sedative agents for patients with aneurysmal subarachnoid hemorrhage undergoing diagnostic cerebral angiography. J J Anesth. 2014. doi:10.1007/s00540-014-1952-1. 3. Charan J, Biswas T. How to calculate sample size for different study designs in medical research? Indian J Psychol Med. 2013;35:121–6. 4. Noordzij M, Tripepi G, Dekker FW, Zoccali C, Tanck MW, Jager KJ. Sample size calculations: basic principles and common pitfalls. Nephrol Dial Transpl. 2010;25:1388–93. To the Editor: We thank Drs. Banik and Prabhakar for their comments [1] on our paper [2]. Based on the parameters we studied in 60 patients with subarachnoid hemorrhage (SAH), we found dexmedetomidine to be a better choice for sedation compared to propofol in spontaneously breathing patients for cerebral angiography. They opine that sample size calculation based on an earlier study might not hold well for our study. We differ with their observation. The study we used was closest to our design. The calculation of sample size depends on whether the outcome variable is quantitative or qualitative [3]. When qualitative parameters are used, sample size required is larger. It also depends on degree of difference the investigators wishes to accept between study and control groups. There are many formulas for different types of data and study designs. It is important that the parameter used for estimating the sample size should be one that measures treatment effects that we consider clinically relevant. In most studies, investigators use standard deviation from a pilot study or from published data [4]. Although previous studies have differences with the current study, such as dissimilar eligibility criteria