Does Perioperative Lidocaine Infusion Decrease the Mininmum Alveolar Concentration of Isoflurane viz-a-viz Depth of Anaesthesia using Processed Electroencephalogram (Bispectral Index)

Introduction: Minimal alveolar concentration (MAC) ofvolatile anaesthetics is that which prevent movement in50% of subjects in response to a noxious stimulus. MACis influenced by several drugs like fentanyl, midazolam,propofol, clonidine. Various successful studies have been doneto demonstrate the effect of IV anaesthetics and opioids onMAC of various inhaled anaesthetics in balanced anaesthesiasettings. To assess the effect of a perioperative lidocaineinfusion on the MAC of isoflurane in a balanced anaesthesiatechnique by correlating it with the depth of anaesthesia asassessed by the Bispectral Index (BIS).Material and methods: It is a prospective randomized studyconsisting of 100 patients. The patients were categorized intogroup L and group S, Group L received a bolus of 1.5mg/kg of lidocaine five minutes before the induction of generalanaesthesia followed by 1.5mg/kg/hr of lidocaine infusiontill the end of the surgical procedure or upto a maximum ofthree hours (whichever was earlier). Group S received salinesimilarly. BIS was maintained between 40 to 60 and MAC ofisoflurane was measured in both group.Result: Significant difference with regard to MAC ofisoflurane used to maintain anaesthesia was noted betweenthe two groups. It was found overall average MAC ofisoflurane in Group L was (0.761±0.011) and control groupwas (0.885±0.020).Conclusion: Our study found that lidocaine loading dosefollowed by infusion significantly reduces volatile anaestheticrequirement as measured by MAC of isoflurane.

Comparison of finger photoplethysmogram and cerebral state index for monitoring depth of anaesthesia / 实用医学杂志

Objective To explore the similarities and differences between finger photoplethysmogram (PPG) and CSI in monitoring the depth of anaesthesia in Chinese adults under general anaesthesia. Methods Ninety-three patients, ASA ⅠorⅡ, aged 20-67, under general anaesthesia were enrolled. Anaesthesia was induced with target-controlled infusion (TCI) of propofol. The initial TCI concentration of propofol was set at 0.5 mg·L-1 followed by increments of 0.5 mg·L-1 at 3-min interval until the score of Modified Observer's Assessment of Alertness/Sedation Scale (MOAAS)reached 0. PPG and CSI were continuously monitored and their values were recorded every 2-4 seconds. MOAAS was recorded every 30 seconds to evaluate the sedation level in the study period. ResultsFor the periodfrom pre-induction to pre-intubation, the difference of photoplethysmogram amplitudevalues had statistical significance between level 4 and level 3, level 3 and level 2 of MOAAS (P<0.05). CSIvalues declined along with the decrease of MOAAS levels and were statistically different between every two neighboring levels of MOAAS (P < 0.05). Photoplethysmogram amplitude (PPGA) and pulse beat interval (PBI) values showed significant differences before and after intubation, pre- and post-incision (P < 0.05). Conclusions PPGA and PBI appear to be suitable to monitor the nociceptive component of balanced general anesthesia , while the CSI exhibits a good performance in monitoring the sedation or hypnotic component of balanced general anesthesia , thusthe combination of PPGA and CSI would benefit the monitoring of the adequacy of depth of anaesthesia.

Depth of anaesthesia monitors and the latest algorithms

This paper reviews the existing depth of anaesthesia (DoA) monitors and their algorithms and also proposes to improve their performance from four aspects. An ideal DoA monitor should be able to suggest a personalised drug dosage, to predict and provide early warnings when dosages are inappropriate, to be portable and highly cost-effective. The limitations of the existing DoA monitors commonly include unsatisfied data filtering techniques, time delay for the monitoring responses, and inflexible and low noise immunity problems. The latest research results show that their performance can be improved using up-to-date computing technology and neurophysiology. The findings in Chinese market review show that neither the imported nor the Chinese domestic DoA monitors are widely utilised at hospitals, but the demand for DoA monitors is very high. Clearly there is a high demand which encourages the development of a better DoA monitor and its mass production in China.

Extraction method of 40Hz ASSR for monitoring the depth of anaesthesia / 医疗卫生装备

In recent years, 40Hz auditory steady state response (ASSR) has been paid more attention when the depth of anaesthesia monitored because its same source with the middle latency auditory evoked potential (MLAEP), strong anti-jamming ability and close relationship with consciousness level. This article brings forward some effective and steady methods for extracting ASSR according to its characteristics. The results of these methods are analyzed and compared based on the actual records from clinical practice. And thus an extraction method fit for monitoring the depth of anaesthesia is determined.