Reliability of right atrial pressure monitoring to assess left ventricular preload in critically ill septic patients

Right atrial pressure (RAP) can be used as a guide to fluid therapy in critical care settings. RAP and pulmonary capillary wedge pressure (WP) were measured in 27 septic patients without cardiac disease and on mechanical ventilation. An r of .61 was obtained with a regression line defined by the equation WP = 7.38 + (0.53 x RAP) +/- 3.15. However, a large SD of data points can invalidate the clinical usefulness of this equation. The reliability of various RAP interval values in predicting optimal WP was then studied in these patients. We concluded that RAP values less than or equal to 5 mm Hg were highly specific (97%) in predicting low or normal WP (less than or equal to 12 mm Hg).     

Use of bispectral electroencephalogram monitoring to assess neurologic status in unsedated, critically ill patients

OBJECTIVE: To test whether spectral indices derived from the electroencephalogram (EEG), and especially the bispectral index (BIS), can be used as measures of neurologic status in unsedated, critically ill patients. DESIGN: Prospective, observational study. SETTING: Medical intensive care unit (ICU) of a university-affiliated teaching hospital. PATIENTS: Thirty-one awake, unsedated critically ill adults were assessed in 108 separate sessions. MEASUREMENTS AND MAIN RESULTS: In each session, severity of illness was assessed by the Acute Physiology and Chronic Health Evaluation (APACHE III). The APACHE III Acute Physiology Score was used to quantify the degree of physiologic derangement. Neurologic function was assessed using the APACHE III Neurologic Score, the Glasgow Coma Scale, the Reaction Level Scale, and the Modified Ramsay Sedation Scale. All indices were plotted against various spectral parameters of the EEG, including BIS, an empirical index of EEG activity that is scaled from 0 to 100. BIS was significantly (p <.05) correlated with neurologic score regardless of scoring system used and was more strongly correlated than any other EEG spectral parameter. Better neurologic function was associated with higher values of BIS. In multivariate analysis, the combination of BIS and relative power in the theta band of the EEG accounted for 38% of the variability in the Glasgow Coma Scale. CONCLUSIONS: BIS provides a reliable index of neurologic status in awake, unsedated, critically ill patients. Further research is needed to determine whether the effects of neurologic status and pharmacologic sedation upon EEG are additive, whether BIS can be used to assess pharmacologic sedation in the critically ill patient population, and whether such objective measures of neurologic status have prognostic value.     

Bedside blood gas and electrolyte monitoring in critically ill patients

A major advantage of near-patient testing is time savings that facilitate important diagnostic and therapeutic decisions. Recent technologic advances have made available a number of systems that allow for near-patient testing. The reliability of these instruments must be validated in the clinical setting in the hands of their intended users. We evaluated the Gemstat blood gas, electrolyte, and Hct portable analyzer in the critical care setting when used by numerous individuals with no previous laboratory training. Blood gas, Na, K, and Hct results were highly correlated with those from the clinical laboratories (PaO2, r = .96; PaCO2, r = .92, pH, r = .96; Na, r = .93; K, r = .95; Hct, r = .91). The Gemstat represents a new generation of portable, rapid, safe, and accurate instruments that are well suited for ICU settings. The instrument can facilitate clinical management of patients, and may improve patient care.     

Labeled acetate to assess intestinal absorption in critically ill patients

OBJECTIVE: To compare the absorption of carbon-13(13C) acetate-enriched nutrients with D-xylose absorption. DESIGN: Prospective cohort observational study. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: A total of 24 critically ill patients requiring enteral nutritional support. INTERVENTION: The patients were divided into three groups according to the route of 13C acetate administration: 1) gastric, 2) jejunal, and 3) intravenous. D-xylose was administered via the same route as enteral nutrition. MEASUREMENTS AND MAIN RESULTS: 13C acetate absorption and oxidation were reflected by pulmonary 13CO2 excretion. Breath 13CO2 isotopic enrichment was measured by mass spectrometry. 13C acetate absorption was rapid, and D-xylose absorption was depressed in all three groups, compared with the normal values (p <.0001). Breath CO isotopic enrichment was similar after intravenous and jejunal administration but slightly delayed during the first 240 mins after gastric administration (p <.01). Enteral feeding was well tolerated: mean energy delivery amounted to 77%, 88%, and 86% of measured resting energy expenditure on days 1-3. CONCLUSIONS: Gastric and jejunal 13C acetate are rapidly absorbed in critically ill surgical patients requiring enteral nutrition, contrasting with a depressed or delayed D-xylose absorption. 13CO2 recovery kinetics was similar after jejunal or intravenous 13C acetate and slightly depressed after gastric administration. Further studies are required to determine the value of labeled nutrients to assess gastric emptying and intestinal absorption.     

Reliability of electrocardiogram interpretation in critically ill patients

OBJECTIVE: To assess the intrarater and interrater reliability of electrocardiogram (ECG) interpretation in critically ill patients and to assess the effect of knowledge of cardiac troponin values on these reliability estimates. DESIGN: Prospective cohort study. SETTING: Fifteen-bed medical-surgical intensive care unit. PATIENTS: Consecutive adults admitted over a 2-month period. MEASUREMENTS AND RESULTS: All consecutive 12-lead ECGs were interpreted independently by two raters for the presence of myocardial ischemia or infarction and secondarily for specific ischemic ECG abnormalities. The ECGs were first interpreted blinded to the patient's troponin levels and reinterpreted on two separate occasions, blinded and unblinded to the troponin values. Results are reported using chance-independent agreement (phi) with associated 95% confidence intervals. For the presence of ischemia or infarction, the intrarater reliability ranged from fair to moderate (phi = 0.35 [95% confidence interval = 0.16, 0.52] and 0.59 [0.33, 0.77] for the two raters, respectively); interrater reliability was slight when blinded to troponin levels (phi = 0.18 [0.03, 0.32]) and increased to moderate when the raters were unblinded to troponin values (phi = 0.52 [0.33, 0.66], p value for the difference = .004). For specific ECG changes, the intrarater and interrater reliability were low for T-wave flattening, whereas detection of a left bundle branch block showed high reliability. CONCLUSIONS: ECG interpretation in critically ill patients for the presence of myocardial ischemia or infarction showed moderate reliability at best; however, there was high reliability for specific ECG changes. Knowledge of the patient's troponin values increased the reliability for all studied ECG changes and resulted in a statistically significant increase in the interrater reliability for diagnosing myocardial ischemia or infarction. Additional studies assessing the appropriate methods of diagnosing myocardial ischemia and infarction and assessing the reliability of these diagnostic tests in critically ill patients are required.     

Intrathoracic blood volume accurately reflects circulatory volume status in critically ill patients with mechanical ventilation

Positive pressure ventilation in patients with acute respiratory failure (ARF) may render the interpretation of central venous pressure (CVP) or pulmonary wedge pressure (PCWP) difficult as indicators of circulating volume. The preload component of cardiac (CI) and stroke index (SI) is also influenced by the increased intrathoracic pressures of positive pressure ventilation. Moreover CI and SI do not indicate volume status exclusively but also contractility and afterload. We investigated whether intrathoracic blood volume (ITBV) more accurately reflects blood volume status and the resulting oxygen transport (DO₂). CVP, PCWP, cardiac (CI) and stroke index (SI) were measured, oxygen transport index (DO₂I) and oxygen consumption index (VO₂I) were calculated in 21 ARF-patients. Ventilatory patterns were adjusted as necessary. CI, SI and intrathoracic blood volume index (ITBVI) were derived from thermal dye dilution curves which were detected with a 5 F fiberoptic thermistor femoral artery catheter and fed into a thermaldye-computer. All data were collected in intervals of 6h. There were 224 data sets obtained. Linear regression analysis was performed between absolute values as well as between the 6 h changes (prefix ). The following correlation coefficients were determined: CVP/CI and PCWP/CI 0.01 and –0.142 (p<0.05); CVP/SI and PCWP/SI –0.108 and –0.228 (p<0.01); ITBVI/CI and ITBV/SI 0.488 (p<0.01) and 0.480 (p<0.01); ITBVI and DO₂I 0.460 (p<0.01); CVP/CI and PCWP/CI –0.069 and–0.018; CVP/SI and PCWP/SI –0.083 and –0.009; ITBVI/CI and ITBVI/SI 0.715 (p<0.01) and 0.646 (p<0.01); ITBVI and DO₂I 0.707 (p<0.01). We conclude that in mechanically ventilated patients ITBV is a suitable indicator of circulating blood volume.     

危重病人肠内营养胃残余量监测研究进展

对胃残余量定义、阈值、监测方法意义及在临床中的应用进行综述,为危重病人肠内营养供给提供参考。     

Reliability of anion gap as an indicator of blood lactate in critically ill patients

Objective: To evaluate the sensitivity, specificity, and predictive values of an elevated anion gap as an indicator of hyperlactatemia and to assess the contribution of blood lactate to the serum anion gap in critically ill patients. Design: Prospective study. Setting: General intensive care unit of a university hospital. Patients: 498 patients, none with ketonuria, severe renal failure or aspirin, glycol, or methanol intoxication. Measurements and results: The anion gap was calculated as [Na⁺] − [Cl⁻] − [TCO₂]. Hyperlactatemia was defined as a blood lactate concentration above 2.5 mmol/l. The mean blood lactate concentration was 3.7 ± 3.2 mmol/l and the mean serum anion gap was 14.3 ± 4.2 mEq/l. The sensitivity of an elevated anion gap to reveal hyperlactatemia was only 44 % [95 % confidence interval (CI) 38 to 50], whereas specificity was 91 % (CI 87 to 94) and the positive predictive value was 86 % (CI 79 to 90). As expected, the poor sensitivity of the anion gap increased with the lactate threshold value, whereas the specificity decreased [for a blood lactate cut-off of 5 mmol/l: sensitivity = 67 % (CI 58 to 75) and specificity = 83 % (CI 79 to 87)]. The correlation between the serum anion gap and blood lactate was broad (r ² = 0.41, p < 0.001) and the slope of this relationship (0.48 ± 0.026) was less than 1 (p < 0.001). The serum chloride concentration in patients with a normal anion gap (99.1 ± 6.9 mmol/l) was comparable to that in patients with an elevated anion gap (98.8 ± 7.1 mmol/l). Conclusions: An elevated anion gap is not a sensitive indicator of moderate hyperlactatemia, but it is quite specific, provided the other main causes of the elevated anion gap have been eliminated. Changes in blood lactate only account for about half of the changes in anion gap, and serum chloride does not seem to be an important factor in the determination of the serum anion gap. Received: 22 May 1996 Accepted: 13 January 1997     

Intra-abdominal pressure monitoring for critically ill patients

Increased intra-abdominal pressure (IAP) is associated with a variety of clinical situations and has profound effects, both locally and systemically, that may result in organ dysfunction and failure. If not identified and treated promptly, increased IAP can be fatal. Urinary bladder pressure monitoring is a simple and reliable method of quantifying IAP and is a key factor leading to prompt management and a successful outcome for patients.     

Less invasive hemodynamic monitoring in critically ill patients

Over the last decade, the way to monitor hemodynamics at the bedside has evolved considerably in the intensive care unit as well as in the operating room. The most important evolution has been the declining use of the pulmonary artery catheter along with the growing use of echocardiography and of continuous, real-time, minimally or totally non-invasive hemodynamic monitoring techniques. This article, which is the result of an agreement between authors belonging to the Cardiovascular Dynamics Section of the European Society of Intensive Care Medicine, discusses the advantages and limits of using such techniques with an emphasis on their respective place in the hemodynamic management of critically ill patients with hemodynamic instability.     

Gentamicin volume of distribution in critically ill septic patients

Gentamicin intrapatient pharmacokinetics variations were studied in 40 critically ill medical patients, suffering gram-negative sepsis. These patients were studied in two phases throughout gentamicin treatment: firstly, on the second day of treatment, when aggressive fluid therapy was required, and secondly, five days later, when patients had achieved a more stable clinical condition. Pharmacokinetic parameters were determined using least squares linear regression analysis assuming a one-compartment model using the Sawchuk-Zaske method. The apparent volume of distribution (Vd) in the first phase of the study was 0.43±0.12 L/kg, while on the seventh day of treatment it was 0.29±0.17 L/kg (p<0.001). Statistically significant differences were also observed for peak serum concentration (p<0.001), total dosage recommended (p<0.001) and half-life (p<0.05), whilst differences were not found for trough levels. From the analysis of the results obtained, we recommend increasing the initial dosage and monitoring plasma levels within the first days of therapy in critically ill patients treated with gentamicin, since important variations in aminoglycoside Vd related to disease, fluid balance and renal function, commonly occur in these patients.     

Ultrasound assessment of gastric volume in critically ill patients

Purpose

To assess the feasibility and validity of ultrasonographic measurement of gastric antral cross-sectional area (usCSA) in critically ill patients to predict gastric volume and the use of computed tomography (CT) as a reference to measure gastric volume.

Method

This single-center, prospective, cross-sectional study included 55 critically ill patients who had an abdominal CT scan. usCSA measurements were performed within the hour preceding the CT scan. Gastric volumes were measured on the CT scan using semiautomatic software. The feasibility rate, performing conditions (% “good” and “poor”), internal and external validity of antral usCSA measurements, performed by an ICU physician, were assessed to predict gastric volume.

Results

Antral usCSA measurements were feasible in 95 % of cases and were positively correlated with gastric volume measured by the CT scan when performed in “good” conditions (65 %) (r = 0.43). There was good reproducibility of measurements (intraclass correlation coefficient of 0.97, CI 95 % 0.96–0.99) and there was clinically acceptable agreement between measurements performed by radiologists and intensivists (bias ?0.12 cm²). The receiver operating characteristic curve identified a cutoff value of 3.6 cm² that discriminated an “at-risk stomach” (volume >0.8 mL/kg) at a sensitivity of 76 % and a specificity of 78 %.

Conclusions

Ultrasonographic measurement of antral CSA is feasible and reliable in the majority of critically ill patients. This technique could be useful to manage critically ill patients at risk of aspiration or with enteral feeding.     

Transcutaneous oxygen tension monitoring in critically ill patients receiving packed red blood cells

Purpose

Whether transfusions of packed red blood cells (PRBCs) affect tissue oxygenation in stable critically ill patients is still matter of discussion. The microvascular capacity for tissue oxygenation can be determined noninvasively by measuring transcutaneous oxygen tension (tcpO₂). The aim of this study was to assess tissue oxygenation by measuring tcpO₂ in stable critically ill patients receiving PRBC transfusions.

Methods

Nineteen stable critically ill patients, who received 2 units of PRBC, were prospectively included into this pilot study. Transcutaneous oxygen tension was measured continuously during PRBC transfusions using Clark's electrodes. In addition, whole blood viscosity and global hemodynamics were determined.

Results

Reliable measurement signals during continuous tcpO₂ monitoring were observed in 17 of 19 included patients. Transcutaneous oxygen tension was related to the global oxygen consumption (r = − 0.78; P = .003), the arterio-venous oxygen content difference (r = − 0.65; P = .005), and the extraction rate (r = − 0.71; P = .02). The transfusion-induced increase of the hemoglobin concentration was paralleled by an increase of the whole blood viscosity (P < .001). Microvascular tissue oxygenation by means of tcpO₂ was not affected by PRBC transfusions (P = .46). Packed red blood cell transfusions resulted in an increase of global oxygen delivery (P = .02) and central venous oxygen saturation (P = .01), whereas oxygen consumption remained unchanged (P = .72).

Conclusions

In stable critically ill patients, microvascular tissue oxygenation can be continuously monitored by Clark's tcpO₂ electrodes. According to continuous tcpO₂ measurements, the microvascular tissue oxygenation is not affected by PRBC transfusions.     

重症患者床旁血糖监测的准确性评价及影响因素分析

目的 评价重症患者床旁快速血糖监测的准确性,探讨其相关的临床影响因素.方法 选择240例重症医学科收治年龄≥18岁的重症患者,血糖调控期间依据血糖检测值将患者分为3组:①低血糖组,血糖值＜4.5 mmol/L,32例;②目标血糖组,血糖值4.5 ～ 8.3 mmol/L,138例;③高血糖组,血糖值＞8.3 mmol/L,70例.试验期间,床旁同步采集患者静脉血、动脉血、指端血,分别采用葡萄糖氧化酶法(GOD法)和葡萄糖脱氧酶法(GDH法)快速检测血糖值,同时以中心实验室己糖激酶法(HK法)测定的血糖值作为标准对照进行准确性评估;对可能影响床旁快速血糖检测准确性的各因素进行logistic回归分析.结果 ①低血糖组患者静脉血、动脉血、指端血快速血糖检测错误率(GDH法:25.00％、40.62％、40.62％,GOD法:59.38％、71.88％、71.88％)显著高于同类受检血样的目标血糖组(GDH法:2.90％、9.42％、7.97％,GOD法:18.12％、27.54％、27.54％)和高血糖组(GDH法:1.43％、8.57％、4.28％,GOD法:11.43％、8.57％、11.43％,均P＜0.01).②低血糖组患者快速血糖检测值与实验室对照值间的差值平均水平为0.41～0.69 mmol/L(GDH法)和0.92～1.18 mmol/L( GOD法);目标血糖组分别为0.16～0.33 mmol/L和0.77～0.90 mmol/L;高血糖组相应降至-0.06～0.18 mmol/L和0.56～0.76 mmol/L.③低血糖组患者快速血糖检测值与实验室对照值间相关系数仅为0.812～0.853(GDH法)及0.723～0.816(GOD法);目标血糖组达0.862～0.890及0.768～0.857;高血糖组患者相应升至0.922～0.957及0.896～0.922(均P＜0.01).④Logistic回归分析显示,患者血糖水平、急性生理学与慢性健康状况评分系统Ⅱ(APACHEⅡ)评分、红细胞比容能进入回归方程.结论 重症患者血糖调控期间,血糖、红细胞比容及病情程度等因素影响床旁血糖监测的准确性.低血糖状态下,快速血糖检测的准确性显著降低,更易高估患者的实际血糖水平.     

血容量监测在血液透析中的临床应用

目的观察透析过程中在线监测相对血容量(RBV)变化对预测和防止透析中低血压及调整透析患者干体重的作用.方法监测12例血液透析患者透析过程中RBV、血压、心率的变化,并用超声心动同步测定下腔静脉宽度(IVCD)及心脏参数.结果透析结束时RBV变化范围在78.9%～102.6%,在有和无症状性低血压的透析过程最低血容量(mRBV)有显著差别[(84.41±3.85) v (87.38±4.66)%,P=0.01],RBV与超滤量及心率变化均呈线性相关(r值分别为0.293,-0.359;P<0.01);IVCD变化率与RBV变化呈线性相关(r=0.311,P<0.05);透析结束时RBV降低小于5%的患者经下调干体重高血压好转.结论尽管血液透析过程中RBV变化存在较大的个体间和个体内差异,RBV与透析中低血压的发生密切相关,故血容量监测对预测和防止低血压具有一定作用,此外对判断干体重的高估也有辅助作用.