Use of creatinine clearances to monitor the effect of low-dose dopamine in critically ill surgical patients

INTRODUCTION: Despite uncertain evidence of its efficacy, "low-dose dopamine" (2-5 microg/kg/min) has often been used to augment renal perfusion in critically ill surgical patients. The 2-h creatinine clearance (CC) has been shown to be a monitor of renal function in critically ill patients. We therefore studied the use of sequential CC determinations to monitor the effect of low-dose dopamine (LDD) in surgical intensive care unit (SICU) patients. We hypothesized that sequential CC measurements could demonstrate whether individual patients had positive responses in renal function to LDD. METHODS: Data were prospectively collected for patients on LDD in a university SICU. CC were recorded for these patients immediately before and after the institution of LDD or before and after the cessation of LDD. APACHE II scores, gender, urine creatinine, age, blood pressure, heart rate, and urine output (UO) were also recorded for these patients; P < 0.05. RESULTS: Twenty-four pairs of CC values were observed during the study. The mean APACHE II score for the patients was 15.1. In 10 cases after initiation of LDD, the mean CC increased from 52.5 +/- 23.7 ml/min to 68.1 +/- 33.8 ml/min (P = 0.056). UO also increased from 48.0 +/- 27 to 75.9 +/- 49 ml/h (NS). In 14 cases after discontinuation of LDD, CC decreased from 85.6 +/- 36.3 ml/min to 63.6 +/- 45.5 ml/min (P = 0.044) and UO decreased from 105.1 +/- 73.9 to 89.6 +/- 76.7 ml/h (NS). Overall, 13 of the 24 patients had a 25% change or more in CC upon initiation or cessation of LDD. CONCLUSIONS: LDD institution increased CC in individual patients in the SICU population. Because using LDD in the absence of a discernable improvement in renal function is costly and may harbor risks, we recommend following CC in patients on LDD to determine which patients derive benefit from the intervention.     

Changes in the bispectral index and the spectral edge frequency 90 during different phases of anesthesia with sevoflurane

INTRODUCTION: Electroencephalographic monitoring is one of the techniques used to measure hypnosis during anesthesia. Efforts to find a means to apply this monitoring function are justified by cases of intraoperative awakening and are in the interest of guaranteeing patient welfare and controlling anesthesia. OBJECTIVES: To determine the changes in two electroencephalographic parameters, the bispectral index (BIS) and the spectral edge frequency 90 (SEF90), during the different phases of anesthesia.Patients and method. Forty-eight patients undergoing abdominal surgery were studied prospectively. Anesthesia was induced by propofol, fentanyl or sevoflurane. Anesthesia was maintained with sevoflurane and O2/N2O at a concentration of 70% to maintain BIS between 40 and 60. Variables monitored were heart rate, blood pressure, arterial oxygen saturation (with a pulse oximeter), expired CO2 partial pressure, inspired and expired sevoflurane partial pressure, esophageal temperature, SEF90 (defined as the frequency below which 90% of the power in the electroencephalogram resides) and BIS. All variables were recorded during three phases: induction, maintenance and recovery from anesthesia. We then performed an analysis of variance, with p < 0.05 considered significant. RESULTS: During induction mean BIS decreased from 95.6 to 34.7 after intubation, while SEF90 fell from 20.5 Hz to 11.9 Hz. During maintenance BIS, SEF90 and expired sevoflurane partial pressure remained constant. During recovery mean BIS increased from 59.2 to 92.3 upon extubation, and SEF90 went from 15.1 to 22.2 Hz; although heart rate increased, blood pressure did not. The mean electroencephalographic values recorded when movement occurred were 77 for BIS (range 58-96) and 18 for SEF90 (range 13-18). CONCLUSION: Electroencephalographic monitoring is useful for distinguishing between states of consciousness and unconsciousness during anesthesia, and is valid for the phases of induction and recovery. BIS values over 58 and SEF90 values over 13 may indicate inadequate hypnosis.     

The influence of ketamine on the bispectral index, the spectral edge frequency 90 and the frequency bands power during propofol anesthesia]

To investigate the influence of ketamine on the bispectral index (BIS), the spectral edge frequency 90 (SEF 90) and relative power in four frequency bands (beta, alpha, theta, sigma), we studied 13 patients (ASA I-II) undergoing elective surgery. In the first study (n = 7), we administered ketamine (1.0 mg.kg-1, bolus, i.v.) during propofol anesthesia. Thirty minutes after the administration, BIS, SEF 90 and relative beta power increased significantly. In the second study (n = 6), bolus administration of ketamine (0.5 mg.kg-1 i.v.) followed by continuous infusion was started during propofol anesthesia. The infusion rate of ketamine was 0.5 mg.kg-1.h-1 for 30 minutes and then increased to 1.0 mg.kg-1.h-1. BIS, SEF 90 and relative beta power increased significantly after ketamine administration, but the parameters did not change in dose-related manner. We conclude that further investigation is necessary to use electroencephalographic parameters as an indicator of the anesthesia depth during propofol/ketamine anesthesia.     

Evaluation of the sedation level with propofol with electroencephalographic Entropy in comparison with bispectral index monitor

BACKGROUND: Entropy, a newly available electroencephalographic monitor, demonstrates two parameters, response entropy (RE) and state entropy (SE). The aim of this study is to compare RE and SE with bispectral index (BIS) during anesthetic induction with propofol. METHODS: Fifteen patients received target controlled infusion of propofol starting at 3 microg x ml(-1). We measured RE, SE and BIS and recorded effect-site concentrations of propofol at three sedation levels: VR1; conscious state before infusion of propofol, VR2; no response to verbal command, and VR3; no response to verbal command and shaking. Spearman rank correlations and prediction probability for sedation level were analyzed. RESULTS: Effect-site concentrations of propofol at VR1, VR2, and VR3 were 0, 1.8 +/- 0.7, and 2.4 +/- 0.7, respectively. All three parameters showed significant correlations with sedation levels. Prediction probability values of SE, RE, and BIS were 0.905, 0.894, and 0.890, respectively. CONCLUSIONS: Response entropy and SE can provide similar information as BIS about the sedation level with propofol.     

The effect of the decreased serum concentration of propofol induced by rapid fluid infusion on the spectral edge frequency 90 and median frequency

The effect of decreased serum concentration of propofol induced by rapid infusion therapy on the EEG was assessed by spectral edge frequency 90% (SEF90) or median frequency (MF) during propofol anesthesia. The eight scheduled surgical patients were administered propofol with a constant rate, and the rapid infusion therapy with 10 ml.kg-1 of acetate Ringer's solution significantly decreased the serum concentration of propofol from 1.96 +/- 0.22 micrograms.ml-1 to 1.68 +/- 0.19 micrograms.ml-1 (approximately 17% reduction). Simultaneous monitoring of SEF90 and MF, however, demonstrated no change during investigation. These results suggest that the mild decrease of the concentration of propofol might not induce the significant change of EEG, or that the reduction of propofol concentration by infusion might be deceptive and produce no significant change in the concentrations of each pharmacological compartment.     

熵指数监测全麻患者镇静水平的准确性

目的 评价反应熵和状态熵监测全麻患者镇静水平的准确性.方法 择期行腹部手术患者20例,ASAⅠ或Ⅱ级,入室后监测反应熵(RE)、状态熵(SE)及脑电双频谱指数(BIS),静脉注射异丙酚、维库溴铵和芬太尼麻醉诱导,气管插管后机械通气,吸入七氟烷、间断静脉注射维库溴铵和芬太尼维持麻醉.分别于入室时、意识消失前10min、意识消失即刻、气管插管时、手术1 h、意识恢复前10 min、意识恢复即刻、拔管后10 min时记录RE、SE和BIS.结果 RE、SE和BIS在意识改变前后差异均有统计学意义(P＜0.05),RE、SE和BIS判断意识消失的临界值分别为76、73和68,灵敏度分别为94%、95%和92%,特异度分别为92%、94%和9l%,临界值判断意识消失的准确度分别为93%、95%、94%;判断意识恢复的临界值分别为82、75和70,灵敏度分别为95%、95%和91%,特异度分别为93%、96%和93%,临界值判断意识恢复的准确度分别为98%、96%和97%.结论 熵指数能够准确地监测全麻患者镇静水平.     

听觉诱发电位指数、双频指数和边缘频率与丙泊酚镇静作用的相关性研究

目的　分析听觉诱发电位指数 (A line○R ARX indexAAI)、双频指数 (BIS)、95 %边缘频率 (95 %SEF)与丙泊酚镇静作用的相关性。方法　选择 18例ASAⅠ～Ⅱ级 ,在下胸腰段硬膜外阻滞下行妇科手术的成年病人。监测AAI、BIS和 95 %SEF ,依据OAA/S评分法评估镇静程度。术中分次静注丙泊酚 ,每隔 3分钟 2 0mg ,直至OAA/S评分达到 1分。分析AAI、BIS、95 %SEF与OAA/S评分值之间的相关性。结果　AAI、BIS、95 %SEF随病人镇静程度加深明显降低 ,且与OAA/S评分值显著相关 (诱导期Spearman’s等级相关系数r =0 95 8、0 898、0 82 0 ,P <0 0 0 1;恢复期r =0 94 6、0 70 2、0 6 14 ,P <0 0 0 1)。诱导期和恢复期AAI的相关系数与其他两者之间差异皆有高度统计意义 (P <0 0 1)。结论　AAI、BIS和 95 %SEF均可较好地反映丙泊酚的镇静效果。     

Influence of age on hypnotic requirement, bispectral index, and 95% spectral edge frequency associated with sedation induced by sevoflurane

BACKGROUND: Aging is associated with a reduction in anesthetic requirements. The effects of age on the electroencephalographic response to inhalational anesthesia have not been well documented. The objective of the present study was to determine the influence of age on hypnotic requirement and electroencephalographic derivatives such as bispectral index and 95% spectral edge frequency associated with sedation induced by sevoflurane. METHODS: Ninety-six patients were randomly allocated into one of three age groups A, B, and C, ranging in age from 18-39 yr, 40-64 yr, and 65-85 yr, respectively. Patients in each group were sedated with sevoflurane at two predetermined concentrations ranging between 0.45% and 0.85%. The relationship between sevoflurane concentration and response to a verbal command, as well as the relationships between response and bispectral index and 95% spectral edge frequency, was determined. RESULTS: Multiple regression analysis showed that end-tidal sevoflurane concentration and age significantly affected both bispectral index and 95% spectral edge frequency. ED50 values of sevoflurane concentration for loss of consciousness, defined as no response to verbal command, were different between groups A and C: 0.72 (95% confidence interval: 0.68-0.75) versus 0.59 (95% confidence interval: 0.56-0.62). However, the same effective values of bispectral index and 95% spectral edge frequency at this same clinical end point did not differ. CONCLUSIONS: Increasing age reduced sevoflurane requirements to suppress responses to a verbal command but did not change bispectral index and 95% spectral edge frequency associated with this end point, and in a population with a wide age range, bispectral index would predict depth of sedation better than end-tidal sevoflurane concentration.     

Reversal of prolonged sedation using flumazenil in critically ill patients

Thirteen critically ill patients received flumazenil after multiple doses, or an infusion, of midazolam was used as part of a sedation regimen to facilitate intensive care. All patients remained excessively sedated after the midazolam was stopped for 6 hours or longer. An improvement in conscious level occurred in eight patients (61%). In four of these eight patients, the duration of action of flumazenil necessitated its continued administration by an infusion to maintain the improvement in conscious level. The dose of flumazenil required each hour was less than estimated previously; this indicates that it may be subjected to similar alterations of elimination as those described for midazolam. Flumazenil appears to be a useful drug for the reversal of prolonged benzodiazepine sedation but repeated bolus doses or an infusion are needed if significant accumulation of benzodiazepines has occurred.     

Median frequency revisited: an approach to improve a classic spectral electroencephalographic parameter for the separation of consciousness from unconsciousness

BACKGROUND: In the past, several electroencephalographic parameters have been presented and discussed with regard to their reliability in discerning consciousness from unconsciousness. Some of them, such as the median frequency and spectral edge frequency, are based on classic spectral analysis, and it has been demonstrated that they are of limited capacity in differing consciousness and unconsciousness. METHODS: A generalized approach based on the Fourier transform is presented to improve the performance of electroencephalographic parameters with respect to the separation of consciousness from unconsciousness. Electroencephalographic data from two similar clinical studies (for parameter development and evaluation) in adult patients undergoing general anesthesia with sevoflurane or propofol are used. The study period was from induction of anesthesia until patients followed command after surgery and includes a reduction of the hypnotic agent after tracheal intubation until patients followed command. Prediction probability was calculated to assess the ability of the parameters to separate consciousness from unconsciousness. RESULTS: On the basis of the training set of 40 patients, a new spectral parameter called weighted spectral median frequency was designed, achieving a prediction probability of 0.82 on the basis of the "classic" electroencephalographic frequency range up to 30 Hz. Next, in the evaluation data set, the prediction probability was 0.79, which is higher than the prediction probability of median frequency (0.58) or spectral edge frequency (0.59) and the Bispectral Index (0.68) as calculated from the same data set. CONCLUSIONS: A more general approach of the design of spectral parameters leads to a new electroencephalographic spectral parameter that separates consciousness from unconsciousness significantly better than the Bispectral Index.     

What,why and how to monitor blood glucose in critically ill patients

Critically ill patients are prone to high glycemic variations irrespective of their diabetes status. This mandates frequent blood glucose (BG) monitoring and regulation of insulin therapy. Even though the most commonly employed capillary BG monitoring is convenient and rapid, it is inaccurate and prone to high bias, overestimating BG levels in critically ill patients. The targets for BG levels have also varied in the past few years ranging from tight glucose control to a more liberal approach. Each of these has its own fallacies, while tight control increases risk of hypoglycemia, liberal BG targets make the patients prone to hyperglycemia. Moreover, the recent evidence suggests that BG indices, such as glycemic variability and time in target range, may also affect patient outcomes. In this review, we highlight the nuances associated with BG monitoring, including the various indices required to be monitored, BG targets and recent advances in BG monitoring in critically ill patients.     

The use of bispectral analysis to monitor outpatient sedation.

The bispectral (BIS) index has been used to interpret partial EEG recordings to predict the level of sedation and loss of consciousness in patients undergoing general anesthesia. The author has evaluated BIS technology in determining the level of sedation in patients undergoing outpatient deep sedation. These experiences are outlined in this review article. Initially, the correlation of the BIS index with traditional subjective patient evaluation using the Observer's Assessment of Alertness and Sedation (OAA/S) scale was performed in 25 subjects. In a second study, the recovery profile of 39 patients where the BIS was used to monitor sedation was compared with a control group where the monitor was not used. A strong positive relationship between the BIS and OAA/S readings was found in the initial subjects. From the recovery study, it appears that use of the BIS monitor may help titrate the level of sedation so that less drugs are used to maintain the desired level of sedation. A trend to earlier return of motor function in BIS-monitored patients was also demonstrated. BIS technology offers an objective, ordinal means of assessing the depth of sedation. This can be invaluable in comparing studies of techniques. The BIS index provides additional information to standard monitoring techniques that helps guide the administration of sedative-hypnotic agents. The trend to earlier return of motor function in BIS-monitored patients warrants further investigation.