Use of near infrared spectroscopy for the prediction of perioperative complications in patients undergoing elective microsurgical resection of cerebral arteriovenous malformations- a prospective observational trial (NIRSCAM trial)

PURPOSE

Cerebral arteriovenous malformations (AVM) represent focal abnormal areas of low resistance circulation which render the peri-nidal neuronal tissue susceptible to ischemia. The post-excision cerebral perfusion surge can result in hyperaemic complications.We hypothesised that Near Infrared Spectroscopy (NIRS)-guided perioperative management can aid in the prediction and prevention of perioperative complications in patients presenting for surgical excision of cerebral AVMs. We also intended to identify a threshold value of regional cerebral oxygen saturation (rScO2) to predict the incidence of perioperative complications.

METHODS

This was a prospective observational study involving patients undergoing elective supratentorial AVM resection surgeries. Intraoperative rScO2 and hemodynamic monitoring were done and continued for postoperatively for 12 h. Any drift in rScO2 by > 12% from baseline was managed as per study protocol and perioperative adverse events were recorded and analyzed. Post surgery,for analytical purpose patients were categorized into two groups, Group A - patients without complications and Group B - patients who had complications postoperatively.

RESULTS

Twenty-five patients presenting for surgical excision of cerebral AVM were recruited for this study of which 9 patients had postoperative adverse events and were allocated to group B. The ipsilateral mean rScO2 at the time of complication (Pc) was significantly lower in Group B than in group A [62.08 ± 9.33 vs.70.52 ± 7.17; p = 0.04]. The mean ipsilateral rScO2 drift from N2- N5 (i.e., post excision) was significantly higher in Group B than in Group A [12.01 ± 2.63% vs. 4.98 ± 5.7%;p = 0.02]. Mean ipsilateral rScO2 Drift ratio (N5 :N2) was significantly higher in group B as compared to group A [1.32 ± 0.01 vs. 1.01 ± 0.06;p < 0.001]. In the immediate post excision phase, the ipsilateral mean rScO2 was significantly higher in Group B at the post excision time point compared to Group A [ 83.03 ± 6.08 vs. 73.52 ± 7.07;p < 0.01)]. The mean ipsilateral rScO2 drift from N1-N6 (i.e., postoperatively) was significantly higher in Group B as compared to Group A [14.96 ± 0.080% vs. 6.88 ± 4.5% ; p < 0.01]. Similarly, the Mean Ipsilateral rScO2 Drift ratio (N6:N1) was significantly lower in group B as compared to group A [2.17 ± 0.02 vs. 1.05 ± 0.03 ;p < 0.0001].

CONCLUSIONS

In patients undergoing cerebral AVM resection, a post-resection ipsilateral rScO2 increase by > 12% with a drift ratio of > 1.3 could signify cerebral hyperemia. A postoperative ipsilateral rScO2 drift > 14.5% with a drift ratio of 2.1 from the baseline is associated with postoperative complications in our study. Further multi-centric randomized control trials are needed to support our research findings.

Evaluation and correlation of nociceptive response index and spectral entropy indices as monitors of nociception in anesthetized patients

Objectives

During anesthesia, the response to these stimuli depends on the balance between nociception and antinociception. Recently, various monitoring systems based on the variables derived from electroencephalography, plethysmography, autonomic tone, reflex pathways, and composite algorithms have been introduced for monitoring nociception. The main aim of our study was to evaluate and correlate the physiological variables which reflect the autonomic nervous system response to nociception, such as heart rate (HR), systolic blood pressure (SBP), perfusion index (PI), and nociceptive response index (NRI), with the spectral entropy indices response entropy (RE) and RE-state entropy (SE), which reflects electromyographic (EMG) activation as a response to pain.

Materials and Methods

This is a retrospective analysis of the data from a prospective study on the hypnotic and analgesic effects and the recovery profile of sevoflurane-based general anesthesia. Eighty-six patients undergoing single-agent sevoflurane anesthesia were recruited in the study. The study parameters, HR, SBP, SE, RE, RE-SE, PI, and NRI, were recorded at predefined time points before and after a standardized noxious stimulus. Correlation between the variables was carried out by applying the Pearson correlation equation for normal and the Spearman correlation equation for non-normally distributed data. Receiver operating characteristic (ROC) graphs were plotted, and the area under the curve was calculated to assess the diagnostic accuracy of post-stimulus NRI in detecting pain which was defined as RE-SE >10.

Results

There was a significant increase in the SBP, HR, NRI, RE, SE, and RE-SE and a considerable decrease in PI values during the post-noxious period compared to the pre-noxious period. There was no correlation between the absolute values of NRI and entropy indices at T2. However, among the reaction values, there was a weak correlation between the reaction values of NRI and RE (r = 0.30; P = 0.05). The area under the ROC curve for NRI to detect pain as defined by RE-SE >10 was 0.56.

Conclusion

During sevoflurane anesthesia, the application of noxious stimulus causes significant changes in variables reflecting sympathetic response and EMG activity. However, NRI failed to detect nociception, and there was only a weak correlation between the reaction values of NRI and RE-SE.

A Perfusion Index-Based Evaluation and Comparison of Peripheral Perfusion in Sevoflurane and Isoflurane Anaesthesia: A Prospective Randomised Controlled Trial

OBJECTIVE

Perfusion index has shown to be helpful in the operative and critical care settings to monitor peripheral tissue perfusion. Randomised controlled trials quantifying different agents' vasodilatory properties using perfusion index has been limited. Therefore, we undertook this study to compare the vasodilatory effects of isoflurane and sevoflurane using perfusion index.

METHODS

This is a pre-specified sub-analysis of a prospective randomised controlled trial on the effects of inhalational agents at equipotent concentration. We randomly allocated patients scheduled for lumbar spine surgery to either isoflurane or sevoflurane groups. We recorded values of perfusion index at age-corrected 1 Minimum Alveolar Concentration (MAC) concentration at baseline, pre- and post-application of a noxious stimulus. The primary outcome of interest was the measure of vasomotor tone with perfusion index, and the secondary outcomes which were analysed were mean arterial pressure and heart rate.

RESULTS

At age-corrected 1.0 MAC, there was no significant difference in the pre-stimulus haemodynamic variables and perfusion index between both groups. During the post-stimulus period, there was a significant increase in heart rate in the isoflurane group compared to the sevoflurane group, with no significant difference in the mean arterial pressure values between both groups. Though the perfusion index decreased during the post-stimulus period in both groups, there was no statistically significant difference between the 2 groups (P = .526, repeated-measures analysis of variance).

CONCLUSION

In a steady state of age-corrected 1.0 MAC, isoflurane and sevoflurane had a similar perfusion index before and after a standardised nociceptive stimulus, which suggests that both of these agents have similar effect on peripheral perfusion and vasomotor tone.

Comparison of multiple risk scores in assessing medium-to long-term clinical outcomes in unstable angina / non-ST-elevation myocardial infarction patients undergoing multi vessel percutaneous coronary intervention: An observational, registry-based study in India

Objective

Post-revascularization mortality in multivessel coronary artery disease (MVCAD) has been explored via several risk scores. Here, we assessed and compared various risk scores in predicting medium to long-term clinical outcomes in unstable angina/non-ST-elevation myocardial infarction (UA/NSTEMI) patients with MVCAD undergoing percutaneous coronary intervention (PCI).

Methods

We analyzed a cohort of a tertiary care center registry enrolling patients in South India, Kerala, with MVCAD (N = 200) who had undergone PCI between 2010 and 2018. The outcomes evaluated were all-cause mortality and major adverse cardiac events (MACE). The risk scores assessed included SYNTAX score (SS), residual SYNTAX score (rSS), SYNTAX revascularization index (SRI), age, creatinine, and ejection fraction (ACEF) score, clinical SYNTAX score (cSS), and SYNTAX score II (SSII).

Results

Of the analyzed risk scores, SSII had the best predictive capability with the area under the curve (AUC) of 0.79 in c-statistics, followed by ACEF score and cSS with AUCs of 0.74 and 0.65, respectively for all-cause mortality (p < 0.01). Kaplan–Meier survival curves and multivariate analysis by Cox regression showed SSII with cut-offs of >35.15 and > 29.55 to be the only score associated with higher mortality and MACE, respectively.

Conclusions

In UA/NSTEMI patients with relatively less complex MVCAD treated by PCI, the SSII, ACEF and cSS risk scores could predict the outcomes better. The SSII showed the best predictive performance for all-cause mortality and MACE. Scores based on baseline and residual atherosclerotic burden (SS, rSS, and SRI) performed poorly in predicting the mortality and MACE.

An improved clinical method for detecting meningeal irritation

Neck stiffness is the most important sign of meningitis. When the neck is flexed, the inflamed nerve roots and meninges of the cervical region get stretched. This causes protective muscle spasm manifesting as neck stiffness. Kernig's sign represents similar phenomena involving the distal spinal cord and related nerves. A manoeuvre that stretches the neural elements of the whole length of the spinal canal simultaneously will be a more sensitive test for meningeal irritation. Eliciting neck stiffness while the patient sits up with knees extended achieves this. This method is more sensitive, specific, and amenable to objective assessment.

Effects of cricothyroid muscle contraction on laryngeal resistance and glottic area

To determine the functional significance of the cricothyroid muscle (CT) in respiration, laryngeal resistance was measured in anesthetized dogs, along with electromyographic activity of the posterior cricoarytenoid muscle (PCA) and CT. In two dogs the larynx was videotaped simultaneously via a telescope. Increased CT activity was induced by airway occlusion or hypercapnia. Observations were carried out before and during cold blockade of the recurrent laryngeal nerve (RLN) or the nerve to the CT (external branch of the superior laryngeal nerve [Ext SLN]). Paralysis of the CT had no effect on laryngeal resistance or glottic area, even at very high levels of CT activity. Blockade of the RLN increased inspiratory resistance, but did not have a significant effect on expiratory resistance. Electrical stimulation of the Ext SLN produced tetanic CT contraction, which increased laryngeal resistance in both inspiration and expiration. This was true even at very high levels of PCA activity. These results indicate that although artificially induced CT contraction markedly affects laryngeal resistance, physiologic levels of respiratory activity do not have a significant effect.