麻醉深度监测与自主神经系统

背景目前临床上应用的麻醉深度监测方法多基于对脑电图（electroencephalogram,EEG）的分析,主要反映全身麻醉的意识状态,对临床麻醉中的自主神经系统活动反映不敏感。目的综述心率变异性（heartrate variability,HRV）分析对自主神经系统的评估在麻醉深度监测中的价值。内容总结近年来有关麻醉深度监测方法的研究进展,现有麻醉深度监测方法的局限性及对自主神经活动性的评价在麻醉深度监测中的应用。趋向HRV分析用于自主神经系统功能评估将使麻醉深度的判断更趋完善。     

氯胺酮和咪唑安定对儿童自主神经功能的不同影响

心率变异性(heart rate variability,HRV)功率谱分析是用于麻醉监测的一项新技术.HRV是指逐次心搏周期间的微小差异,它产生于自主神经系统对心脏窦房结自律性的调节.一般认为,HRV总功率(TP)反映总的自主神经张力;HRV的高频成分(HF)反映副交感神经活性;低频成分(LF)代表交感神经张力[1,2].进一步研究认为,TP、HF和LF结合其标准化值nuHF和nuLF能更好地反映自主神经系统张力的变化[3,4].HRV用于成人麻醉监测已见诸多报道,但有关氯胺酮和咪唑安定麻醉时小儿HRV的变化报道很少.本研究观察氯胺酮和咪唑安定用于学龄前儿童麻醉时对HRV的影响,并分析两者对自主神经功能的不同影响.     

心率变异度及其在慢性肾脏病患者中的研究进展

心率变异度（heart rate variability,HRV）是一种用于评价自主神经功能的简单、无创性检查,目前已越来越多的用于临床.HRV可以用来评估人体在生理条件下的自主神经（ANS）的调节功能,亦可用来评估病理条件下ANS的调节功能.目前已有很多文献[1～8]证实HRV对健康人群及心血管疾病患者猝死及主要的心律失常事件的诊断价值,以及对糖尿病患者自主神经病变的诊断价值,在慢性肾脏病（CKD）领域HRV的研究也有了一定的进展,故本文就CKD患者HRV的相关研究进展做一综述.     

心率变异性的临床应用和研究进展

心率变异性（heart rate variability，HRV）是近年来比较受关注的无创性心电监测指标之一，可用来预测心脏性猝死，评价心脏自主神经的活动性，均衡性及相关的病理状态，具有重要临床价值。如果由于某种原因（如疾病或使用药物）导致自主神经系统调节作用减弱或消失。会引起HRV减少或变为零。许多因素如创伤，应激，麻醉药物都可能导致自主神经功能损害，心血管疾病，猝死往往伴有HRV的显著降低。对围术期HRV的研究不仅有助于澄清麻醉药物及手术对自主神经功能的影响，也能为麻醉深度的判断，手术病人心血管功能及预后的估计增添了一个无创性的定量指标，尤其对老年人，冠心病高危因素者的围术期管理具有重要指导意义。     

听觉诱发电位指数用于诱导插管期间麻醉深度监测的临床评价

目的 观察听觉诱发电位指数在全麻诱导插管期间的变化，评价其用于临床麻醉深度监测的有效性。方法 ASAⅠ-Ⅱ级，全麻下行择期手术的病人40例。依次给予咪唑安定0.06mg/kg，芬太尼4μg/kg，丙泊酚0.5mg/kg，维库溴铵0.1mg/kg诱导后，行气管插管，观察诱导前，气管插管前，插管时及插管后1-5分钟等8个时点的AEPI，BIS，HRV，SEF及MAP，HR和RPP的变化。结果 诱导后各观察指标较诱导前的基础值均有所降低，插管后BIS，HRV，SEF等指标均在5分钟内回复至插管前水平，AEP在第3分钟即可回复至插管前水平，插管前后几项观察指标变化趋势相一致。结论 AEPI，BIS，HRV，SEF均能有效反映插管的应激反应。AEPI较其他几项指标更为迅速灵敏，可作为麻醉深度监测的有效指标。     

心率变异性分析用于临床麻醉监测的展望

心率变异性(heart rate variability,HRV)是判断自主神经功能的客观指标.心率变异性分析方法主要有时域、频域、非线性分析法.目前,临床上HRV信号的分析主要是时域、频域分析,非线性分析法则不多.作者重点综述了心率变异性的非线性分析方法在临床麻醉中的应用.     

对心率变异性的再认识

心率变异性(HRV)的临床应用由时域法过渡到了频域法,目前多采用三个频段,而超高频和超低频的生理意义还不能肯定。HRV不但用于预测某些心脏病的发生,另一方面还用来监测自主神经功能状态,用途广泛。由于影响自主神经活动的因素是多方面的,因此应用时要注意受测对象条件的一致性。文中还讨论了其它一些注意的问题。     

肌松药对脑电双频指数监测麻醉深度的影响

脑电双频指数(bispectral index,BIS)是基于原始脑电图的一种麻醉深度监测指标,近年来已广泛用于临床.术中监测麻醉深度能提高麻醉质量和手术安全性,通过合理调控麻醉深度,减少麻醉用药量和避免麻醉并发症的发生.但是.关于BIS监测在临床麻醉中应用的实际意义或价值以及BIS值判读准确性及可能的影响因素仍是人们一直关心的热点问题,结合近期国内外有关文献,现就肌松药对BIS监测麻醉深度的影响及相关临床应用情况作一综述.     

BIS与HRV监测下丙泊酚TCI麻醉用于声带息肉摘除术的临床观察

支撑喉镜下声带息肉摘除术由于其独有的麻醉要求,如何有效地抑制心血管不良反应,是需要解决的问题.我们在脑电双频指数(BIS)与心率变异性(HRV)监测下,观察丙泊酚靶控输注(TCI)麻醉用于声带息肉摘除术的效果,现报道如下.     

定量脑电分析与麻醉深度监测

随着计算机技术的发展,定量化脑电图分析已用于麻醉深度监测,其中尤以双频谱指数最有价值。本文介绍其原理及其临床应用。     

Anesthetic management of a patient with olivopontocerebellar atrophy using heart rate variability (HRV)

A 65-year-old woman with olivopontocerebellar atrophy (OPCA), manifested with cerebellar ataxia mainly, with coexisting impairment of the autonomic nervous system function, and extrapyramidal symptoms, was scheduled for cholecystectomy. With no premedication, anesthesia was induced with sevoflurane and maintained with 1-1.5% of sevoflurane and 66% of nitrous oxide mixed with oxygen. Heart rate variability (HRV) calculated from ECG was used for a monitor of the autonomic nervous system activity. Before the induction of anesthesia, severe reduction of the HRV parameters suggested that both her sympathetic and parasympathetic nervous activities might have been severely reduced. We considered that the patient might have postganglionic sympathetic nerve hypersensitivity against inotropic agents. When her blood pressure decreased temporarily after the induction of anesthesia, a bolus dose of ephedrine 1 mg wa given intravenously, which stimulated the sympathetic nervous system indirectly, and could increase her blood pressure. Hypotension during anesthesia in a patient with OPCA with severe autonomic nervous failure was successfully treated by a minimal dose of ephedrine.     

Heart rate variability and arterial blood pressure variability show different characteristic changes during hemorrhage in isoflurane-anesthetized, mechanically ventilated dogs.

We assessed the changes in heart rate variability (HRV) and blood pressure variability (BPV) as indices of autonomic nervous system and volume status during hemorrhage in isoflurane-anesthetized, mechanically ventilated dogs. Nine dogs were used. They were sequentially subjected to withdrawal of 30% estimated blood volume and graded isoflurane inhalation of 1% and 2% followed by discontinuation of isoflurane and retransfusion. The power spectra of HRV and BPV were computed using the fast Fourier transformation, and were quantified by determining the areas of the spectrum in two component widths: low-frequency component (LF) (0.04-0.15 Hz) and high-frequency component (HF) (0.15-0.4 Hz). During hemorrhage and isoflurane anesthesia, both HRV-LF and HRV-HF were decreased and plateaued at the smaller concentration of isoflurane, whereas BPV-LF decreased concentration-dependently. BPV-HF showed a completely different response and increased significantly during 2% isoflurane. We speculate that HRV and BPV-LF would be affected by the autonomic nervous activity, whereas BPV-HF would depend on relative/absolute change in circulating blood volume. IMPLICATIONS: Power spectra of heart rate variability (HRV) and blood pressure variability (BPV) were computed using the fast Fourier transformation. The HRV and BPV showed their differential characteristics during hemorrhage, isoflurane anesthesia, and retransfusion, and would help to assess changes in autonomic nervous system and preload under mechanical ventilation.     

The effect of carbon dioxide, respiratory rate and tidal volume on human heart rate variability

BACKGROUND: Heart rate variability (HRV) has been used for assessment of depth of anesthesia. Alterations in respiratory rate and tidal volume modulate the sympatovagal neural drive to the heart. The changes in PaCO2 that accompany changes in breathing pattern may, through chemoreceptors in the brainstem, independently influence the autonomic control of the heart and modulate HRV. METHODS: We measured the effects of PaCO2, tidal volume and respiratory rate on HRV during spontaneous and mechanical ventilation in 22 healthy volunteers and in 25 mechanically ventilated anesthetized patients. RESULTS: Adding CO2 to the inspiratory gas increased high frequency (HF) and low frequency (LF) components of HRV in awake volunteers both during spontaneous and mechanical ventilation, while this effect of CO2 was abolished in patients during anesthesia. Increase of tidal volume increased HF component of HRV only in volunteers during spontaneous ventilation. On the other hand, when respiratory rate was reduced, the balance of HF and LF power moved toward LF power in all study groups. Breathing frequency altered HRV independent on PaCO2, tidal volume and the level of consciousness. In contrast, the effect of PaCO2 appeared to be related to normal level of consciousness, suggesting that a cortical modulation of the autonomic nervous activity contributes to the effects of PaCO2 on HRV. CONCLUSIONS: PaCO2, tidal volume and respiratory rate should be controlled when HRV power spectrum is measured in conscious patients or volunteers, while in anesthetized patients small changes in end-tidal CO2 or tidal volume do not modulate HRV if respiratory rate remains unchanged.     

Heart rate variability: a diagnostic and prognostic tool in anesthesia and intensive care

The autonomic nervous system (ANS) plays an important role in the human response to various internal and external stimuli, which can modify homeostasis, and exerts a tight control on essential functions such as circulation, respiration, thermoregulation and hormonal secretion. ANS dysfunction may complicate the perioperative course in the surgical patient undergoing anesthesia, increasing morbidity and mortality, and, therefore, it should be considered as an additional risk factor during pre-operative evaluation. Furthermore, ANS dysfunction may complicate the clinical course of critically ill patients admitted to intensive care units, in the case of trauma, sepsis, neurologic disorders and cardiovascular diseases, and its occurrence adversely affects the outcome. In the care of these patients, the assessment of autonomic function may provide useful information concerning pathophysiology, risk stratification, early prognosis prediction and treatment strategies. Given the role of ANS in the maintenance of systemic homeostasis, anesthesiologists and intensivists should recognize as critical the evaluation of ANS function. Measurement of heart rate variability (HRV) is an easily accessible window into autonomic activity. It is a low-cost, non-invasive and simple to perform method reflecting the balance of the ANS regulation of the heart rate and offers the opportunity to detect the presence of autonomic neuropathy complicating several illnesses. The present review provides anesthesiologists and intensivists with a comprehensive summary of the possible clinical implications of HRV measurements, suggesting that autonomic dysfunction testing could potentially represent a diagnostic and prognostic tool in the care of patients both in the perioperative setting as well as in the critical care arena.     

Wavelet transform of heart rate variability to assess autonomic nervous system activity does not predict arousal from general anesthesia

PURPOSE: The relationship between autonomic nervous system (ANS) activity and general anesthesia has been explored. Studies have demonstrated partial recovery of heart rate variability (HRV), representative of ANS activity, in the postoperative period, but the arousal period has not been precisely studied. The goals of this study were to analyze modifications of ANS activity during general anesthesia and, more particularly, around the arousal period, to look for predictors of arousal. METHODS: We analyzed HRV changes using wavelet transform, a time-frequency analysis that, in contrast to Fourier transform, is able to assess abrupt changes of ANS activity. Seventeen patients (mean +/- SD age: 40.9 +/- 16.4 yr) under general anesthesia for hip or knee surgery, were included in the study. The analysis began one hour before anesthesia, focussed on eye opening, and ended three hours after arousal. RESULTS: There was a dramatic decrease in HRV after induction, that extended throughout anesthesia and represented a decrease in global autonomic regulation with, however, a relative predominance of vagal tone. At the moment of eye opening, there was an abrupt change in HRV, representing a sudden shift of ANS balance towards the predominance of sympathetic activity, while none of these indices changed seconds before arousal. CONCLUSIONS: Wavelet analysis of HRV appears to be powerful tool to precisely assess instantaneous changes of HRV during anesthesia. Using this method, there were no identifiable precursory HRV indices of arousal.     

Pre-operative measurement of heart rate variability predicts hypotension during general anesthesia

BACKGROUND: Peri-operative hymodynamic instability is one of the major concerns for anesthesiologists when performing general anesthesia for individuals with autonomic dysfunction. The purpose of this study was to examine the potential usage of pre-operative measurement of heart rate variability (HRV) in identifying which individuals, with or without diabetes, may be at risk of blood pressure (BP) instability during general anesthesia. METHODS: We studied 46 patients with diabetes and 87 patients without diabetes ASA class II or III undergoing elective surgery. Participants' cardiovascular autonomic function and HRV were assessed pre-operatively, and hymodynamic parameters were monitored continuously intra-operatively by an independent observer. RESULTS: Only 6% of the participants were classified as having cardiovascular autonomic neuropathy (CAN) based on traditional autonomic function tests whereas 15% experienced hypotension. Total power (TP, P = 0.006), low frequency (LF, P = 0.012) and high frequency (HF, P = 0.028) were significantly lower in individuals who experienced hypotension compared with those who did not. Multivariate logistic regression analysis revealed that TP [odds ratio (OR) = 0.15, 95% confidence interval (CI) = 0.05-0.47, P = 0.001] independently predicted the incidence of hypotension, indicating that each log ms2 increase in total HRV lowers the incidence of hypotension during general anesthesia by 0.15 times. After stepwise multiple linear regression analysis (R2= 11.5%), HF (beta = -11.1, SE = 2.79, P < 0.001) was the only independent determinant of the magnitude of systolic blood pressure (SBP) reduction at the 15th min after tracheal intubation. CONCLUSIONS: Spectral analysis of HRV is a sensitive method for detecting individuals who may be at risk of BP instability during general anesthesia but may not have apparent CAN according to traditional tests of autonomic function.     

Changes in heart rate variability in elderly patients undergoing major noncardiac surgery under spinal or general anesthesia.

BACKGROUND AND OBJECTIVES: Heart rate variability (HRV), widely used as an indicator of activity of the autonomic nervous system, has been reported to decrease during and after both spinal and general anesthesia in patients without cardiovascular disease. We evaluated the changes in HRV bands in 40 patients with a high risk of ischemic heart disease. METHODS: The patients were randomly assigned to receive either spinal (SA) or general anesthesia (GA) for elective total hip arthroplasty or peripheral vascular surgery. Anesthetic techniques and perioperative fluid administration were standardized. Holter monitoring was started preoperatively and continued until the third postoperative day. Three HRV frequency bands were analyzed. RESULTS: A significant decrease was seen in very low frequency (VLF) and low frequency (LF) bands during GA but not during SA. Also the LF/high frequency (HF) ratio decreased during GA but not during SA. A decrease in all HRV frequency bands was seen after both types of anesthesia. None of the frequency bands returned back to the preoperative level during the 3-day trial. Postoperatively circadian variation was found only in the VLF band after SA. CONCLUSIONS: The sympathovagal balance (LF/HF) is more stable during SA than during GA in patients with a high risk of ischemic heart disease. The postoperative decrease in HRV bands, however, is independent of the anesthetic technique.     

Maternal heart rate variability just before surgery significantly correlated with emergence behavior of children undergoing general anesthesia

BACKGROUND: Emergence agitation in pediatric anesthesia is associated with preanesthesia child anxiety, which is strongly influenced by maternal mental conditions. Mental stress affects the autonomic nervous system, thereby influencing heart rate variability (HRV). The present study tested the correlations between preanesthesia maternal HRV and perioperative child behavior. METHODS: A total of 27 pairs of mothers and children were analyzed in the present study. Maternal HRV was recorded from the night before the child's surgery to arrival to the operation room and thereafter recorded data were analyzed. The children underwent minor plastic surgery under general anesthesia, and induction and emergence behavior were assessed. RESULTS: Quality of mask induction did not correlate with the ratio of low-frequency (LF) components to high-frequency (HF) components (LF/HF ratio) of preanesthesia maternal HRV either obtained during 21:00-06:00 (stage I) or 06:00-08:00 (stage II). Scores of the child's emergence behavior did not correlate with the LF/HF ratio of maternal HRV of stage I; however, the LF/HF ratio of maternal HRV of stage II significantly correlated with emergence behavior. CONCLUSIONS: Two-hour maternal HRV just before surgery significantly correlated with emergence behavior of children undergoing general anesthesia.