Preliminary evaluation of a new continuous intra-arterial blood gas monitoring device

Continuous intra-arterial blood gas monitoring is a new technique, possibly offering therapeutic advantages through improved monitoring in patients prone to hypoxaemia, hypercapnia and/or respiratory acidosis. Therefore, we studied the clinical applicability, reliability, precision and side effect of long-term continuous intraarterial blood gas monitoring in patients suffering from severe acute respiratory distress syndrome.
In 10 patients continuous intra-arterial blood gas monitoring based on fluorescent optodes technique was performed. At 4 h intervals, arterial blood samples for in vitro blood gas analyses were drawn, stored in ice, and analysed within 3 min. Evaluation of data retrieved from the continuous intra-arterial blood gas monitoring and in vitro blood gas analysis was based on 596 data points using 10 catheters. Average length of insertion was 281±215 h, max. lengths of stay was 750 h. Arterial blood gas data obtained in vivo were compared to the mean of in vivo and in vitro arterial blood gases.
Inter-catheter bias, expressed as percent difference between continuous intra-arterial blood gas and mean in vitro blood gas analysis was 0. 19±0. 23% for pH, 1. 1 ±5. 2% for PaCO₂ and 1. 6±5. 7% for PaO₂. No significant gas partial pressure dependent change in precision was demonstrable. There was no significant time dependent drift in sensor precision over the study period. No negative side-effects related to IABG monitoring were observed.
We conclude that long-term use of this new device is possible in patients and represents a reliable alternative to conventional in vitro arterial blood gas analysis, when continuous monitoring of blood gases and/or acid-base balance is critical.     

Validation of a tonometric noninvasive arterial blood pressure monitor in the intensive care setting

Intra-arterial measurement is considered the gold standard for continuous, beat-to-beat arterial blood pressure monitoring. However, arterial cannulation can be difficult and may cause complications such as thrombosis and ischaemia. Recently, a tonometric system, the Colin CBM-7000 has been developed for noninvasive beat-to-beat measurement of arterial blood pressure from the radial artery. We assessed the level of agreement between the CBM-7000 and invasive radial artery measurements in 15 patients on a neuro-intensive care unit. Agreement of systolic, diastolic and mean arterial pressure values was limited, with approximately 34% of mean arterial pressures differing by over 10 mmHg. In many cases, this was due to a downward drift of the noninvasive measurements over time. Furthermore, there was a tendency to underestimate low pressures and overestimate high pressures. In our opinion, the Colin CBM-7000 cannot be recommended for continuous blood pressure monitoring in the intensive care setting.     

Clinical evaluation of a new continuous intraarterial blood gas monitoring system in the intensive care setting

The present study was designed to evaluate a new continuous intraarterial blood gas monitoring system under routine clinical intensive care conditions. Nine mechanically ventilated adult patients were enrolled in this study. A multiparameter intravascular sensor was inserted into the radial or dorsalis pedis artery through a 20-gauge cannula in each patient. The accuracy of the sensor for pH, Pco₂, and Po₂ values was evaluated by comparing the data simultaneously obtained from the monitoring system and from conventional blood gas analysis. Measurements were performed for 3 days for each sensor. A total of 62 blood samples were obtained for comparison. The ranges of measured variables were: pH 7.185–7.602, Pco₂, 28.8–68.5 mmHg, and Po₂ 45.2–542.4 mmHg. The overall bias ±precision values were 0.002±0.018 for pH units, 0.53±2.04mmHg for Pco₂, and −1.62±20.00 mmHg for Po₂. In clinically important ranges of Po₂, less than 200 mmHg in particular, the bias and precision values were −2.25±6.48 mmHg in the range of less than 100mmHg, and 0.98±14.38 mmHg in the range of 100–200 mmHg. Variations of sensor accuracy as a function of elapsed time were within the clinically acceptable range throughout the study period. These findings suggest that this new device is sufficiently useful for routine clinical settings.     

Multimodal monitoring in traumatic brain injury: current status and future directions

Traumatic brain injury (TBI) remains a major cause of morbidityand mortality, particularly in young people. Despite encouraginganimal studies, human trials assessing the use of pharmacologicalagents after TBI have all failed to show efficacy. Current managementstrategies are therefore directed towards providing an optimalphysiological environment in order to minimize secondary insultsand maximize the body's own regenerative processes. Modern neurocriticalcare management utilizes a host of monitoring techniques toidentify or predict the occurrence of secondary insults andguide subsequent therapeutic interventions in an attempt tominimize the resulting secondary injury. Recent data suggestthat the use of protocolized management strategies, informedby multimodality monitoring, can improve patient outcome afterTBI. Developments in multimodality monitoring have allowed amovement away from rigid physiological target setting towardsan individually tailored, patient-specific, approach. The wealthof monitoring information available provides a challenge interms of data integration and accessibility and modern softwareapplications may aid this process.     

Fire safety and emergency evacuation guidelines for intensive care units and operating theatres: for use in the event of fire,flood, power cut,oxygen supply failure,noxious gas,structural collapse or other critical incidents

The need to evacuate an ICU or operating theatre complex during a fire or other emergency is a rare event but one potentially fraught with difficulty: Not only is there a risk that patients may come to harm but also that staff may be injured and unable to work. Designing newly-built or refurbished ICUs and operating theatre suites is an opportunity to incorporate mandatory fire safety features and improve the management and outcomes of such emergencies: These include well-marked manual fire call points and oxygen shut off valves (area valve service units); the ability to isolate individual zones; multiple clear exit routes; small bays or side rooms; preference for ground floor ICU location and interconnecting routes with operating theatres; separate clinical and non-clinical areas. ICUs and operating theatre suites should have a bespoke emergency evacuation plan and route map that is readily available. Staff should receive practical fire and evacuation training in their clinical area of work on induction and annually as part of mandatory training, including ‘walk-through practice’ or simulation training and location of manual fire call points and fire extinguishers, evacuation routes and location and operation of area valve service units. The staff member in charge of each shift should be able to select and operate fire extinguishers and lead an evacuation. Following an emergency evacuation, a network-wide response should be activated, including retrieval and transport of patients to other ICUs if needed. A full investigation should take place and ongoing support and follow-up of staff provided.     

Use of conventional ECG electrodes for depth of anaesthesia monitoring using the cerebral state index: a clinical study in day surgery

Background: The cost–benefit relationship for depth of anaesthesiamonitors is complicated by the high cost of specially designedEEG electrodes. The cerebral state index (CSI) monitor willaccept regular ECG electrodes with snap connectors. The purposeof this study was to determine if generic ECG electrodes couldreplace the more expensive proprietary EEG electrodes for theCSI monitor. Methods: Two identical cerebral state monitors were used simultaneouslyduring sevoflurane anaesthesia for knee arthroscopy in 14 ASAI–II patients. One monitor used proprietary (Danmeter)EEG electrodes and the other used ECG electrodes (3M^TM Red Dot^TMDiagnostic ECG Electrodes). Paired CSI values were recordedevery other minute. Anaesthetic depth was titrated clinically.Sedation depth was scored according to the Observer's Assessmentof Alertness/Sedation (OAAS) scale. Results: The agreement between the two measures was found to be high,mean difference – 0.23, and the overall repeatabilitymean bias was 6.6 and 153/163 pairs (94%) were located withinthe 95% limits of agreement. No major difference was noted inimpedance, noise, or artifacts. A large overlap in CSI was notedfor each level of the OAAS scale; patients with CSI values aslow as 40–50 responded whereas patients not respondingto surgical stimulation had CSI values as high as 75. The directcost of disposables decreased from 4 to 0.50 per patient byusing ordinary ECG electrodes. Conclusions: Switching from proprietary EEG electrodes to ordinary genericECG electrodes maintains the same accuracy at about a 10th ofthe cost when measuring CSI during day surgery with sevofluraneanaesthesia.     

Oxygen and acid-base parameters of arterial and mixed venous blood, relevant versus redundant

A complete pH and blood gas analysis of arterial and mixed venous blood may comprise more than forty different quantities. We have selected sixteen, including patient temperature. The arterial oxygen tension group includes the oxygen tension, fraction of oxygen in inspired air, and fraction of mixed venous blood in the arterial (total physiological veno-arterial shunting). The haemoglobin oxygen capacity group includes effective haemoglobin concentration and fractions of carboxy- and methaemoglobin. The haemoglobin oxygen affinity group includes half-saturation tension and estimated 2, 3-diphosphoglycerate concentration of erythrocytes. In a neonatal care unit fraction of fetal haemoglobin needs to be included. The arterial oxygen extractivity is measured as the oxygen extraction tension, which indicates the degree of compensation among the oxygen tension, capacity, and affinity. The mixed venous group includes mixed venous oxygen tension, and, when measured, cardiac output, and oxygen consumption rate. The acid-base status includes blood pH, arterial carbon dioxide tension, and extracellular base excess. Other quantities such as haemoglobin oxygen saturation, respiratory index, total oxygen concentration (oxygen content), oxygen extraction fraction, oxygen delivery, and several others, provide no essential additional clinical information and are therefore redundant.     

Airway management practices at German university and university-affiliated teaching hospitals--equipment, techniques and training: results of a nationwide survey

BACKGROUND: Until recently, Germany did not have national airway management guidelines. This survey collected comprehensive data on departmental airway management practices from German teaching institutions to identify weaknesses, and the results are presented here. German national airway guidelines were formulated by an expert group on the basis of these data and the current evidence in the literature. METHODS: Questionnaires were mailed to the directors of 452 university and university-affiliated anaesthesia departments. They were asked to respond to 39 questions on the use of particular equipment and techniques, management of the difficult airway and training in airway management. RESULTS: Two hundred and twelve questionnaires were returned. Many alternative devices for endotracheal intubation, such as the Bullard laryngoscope, the Bonfils laryngoscope and the Trachlight, are not used in the majority (80%) of departments. Thirty-six per cent of departments do not have difficult airway carts. No departmental difficult airway management plan is used in 22% of departments. Patients are not provided with written information on their personal airway management difficulties in 14% of departments. Structured training in the form of block rotation is offered in only 29-40% of departments. Although trainees perform fibreoptic intubation (FOI) in most departments, appropriate training in FOI is not available in some departments (8%). CONCLUSION: There are deficits in various areas of airway management, in particular training and the use of algorithms. International guidelines and recommendations are not followed by a large number of German teaching institutions. The provision of German national airway guidelines should improve this situation.     

Performance of the radiometer OSM3 and ABL505 blood gas analysers for determination of sodium, potassium and haemoglobin concentrations

We have compared results obtained from two widely used ward-based blood gas analysers, the Radiometer OSM3 and ABL505, with standard laboratory analysers, for haemoglobin, sodium and potassium measurement in critically ill adult patients. During the study, paired samples for analysis were obtained from 81 patients for haemoglobin, 115 patients for sodium and 95 patients for potassium. There was good agreement between the ward and the laboratory analysers in terms of the mean results for each test. However, the limits of agreement for the ward-based analysers were wide, suggesting that their results should be used with caution.     

Clinical evaluation of circulating blood volume in critically ill patients--contribution of a clinical scoring system

The circulating blood volume (CBV) of critically ill patientsmay be difficult to estimate on the basis of history and physicalexamination. The aim of this study was to evaluate the abilityof seven clinical signs and central venous pressure (CVP) topredict CBV in critically ill patients; CBV was evaluated withthe [¹²⁵I]human serum albumin technique. A scoring system wasconstructed using a combination of independence Bayes methodand logistic regression. Sixty-eight patients constituted a‘model development’ sample and 30 patients a validationsample. Thirty-six patients (53%) in the model development samplewere found to have a low CBV (measured CBV at least 10% lowerthan the predicted mean normal CBV). Neither the haemodynamicvariables monitored in ICU, nor the spot urinary sodium concentrationswere different between patients with and without a low CBV.Individually, none of the clinical signs tested have a goodpositive or negative predictive value. For CVP, only extremevalues seem to have clinical significance. To construct thescore, the signs tested were ranked according to their discriminatingefficacy. The probability of a low CBV was obtained by addingthe weights of each sign tested and converting the score obtainedinto a probability. On a validation sample of 30 patients, thepredictions are reliable as assessed by Z statistics rangingbetween –2 and +2. Our results suggest that: (1) individually,no clinical sign presented a clinical useful predictive value;and (2) a clinical scoring system may be helpful for the evaluationof CBV in critically ill patients. Br J Anaesth 2001; 86: 754–62     

动脉置管处改良采血法检测血气分析与APTT的可行性研究

目的探讨从肝素维持的动脉置管处采集血标本的方法,避免浪费血液。方法对30例带有动脉测压置管患儿,用常规法(弃含有肝素的血液3mL)和改良法(不弃血)分别先后从动脉置管处采血。结果两组血气分析,生化指标即钾(K+)、钠(Na+)、红细胞压积(Hct)、活化部分凝血活酶时间(APTT)比较,差异无统计学意义(均P>0.05)。结论从以肝素维持的动脉置管中采血,不弃血采血法可以替代常规采血法,检测血气分析、生化指标可行。     

Measurement of cardiac output: a comparison between transpulmonary thermodilution and uncalibrated pulse contour analysis

Background: Recently, continuous monitoring of cardiac output (CO) basedon pulse contour analysis (Vigileo^®) has been introducedinto practice. In this clinical study, we evaluated the accuracyof this system by comparing it with the transpulmonary thermodilutiontechnique (TPID) in septic patients. Methods: We studied 24 mechanically ventilated patients with septic shock(16 male, 8 female, age 26–77 yr) receiving treatmentwith norepinephrine who for clinical indication underwent haemodynamicmonitoring by the transpulmonary thermodilution technique usinga PiCCO^®plus system (Pulsion Medical Systems, Munich, Germany).In parallel, arterial pulse contour was applied using the femoralarterial pressure curve (FloTrac^® pressure sensor, Vigileo^®monitor, Edwards Lifesciences, Irvine, USA). After baselinemeasurement, mean arterial pressure was elevated by increasingnorepinephrine dosage, and CO was measured again before meanarterial pressure was reduced back to baseline levels. Fluidstatus and ventilator settings remained unchanged throughout.At each time point, CO by transpulmonary thermodilution wascalculated from three central venous bolus injections of 15ml of saline (<8°C). Linear regression and the Bland–Altmanmethod were used for statistical analysis. Results: Overall, CO was 6.7 (SD 1.8) (3.2–10.1) litre min^–1for CO(TPID) and 6.2 (2.4) (3.0–17.6) litre min^–1for CO(Vigileo^®). Linear regression revealed: CO(Vigileo^®)= 1.54 + 0.72 x CO(TPID) litre min^–1, r² = 0.26 (P <0.0001). Mean bias between techniques [CO(TPID)–CO(Vigileo^®)]was 0.5 litre min^–1 (SD 2.3 litre min^–1). Correlationcoefficients at the three time points were not significantlydifferent from each other. Conclusions: Pulse contour analysis-derived CO (Vigileo^® system) underestimatesCO(TPID) and is not as reliable as transpulmonary thermodilutionin septic patients.     

Strong ions, weak acids and base excess: a simplified Fencl-Stewart approach to clinical acid-base disorders

Background. The Fencl–Stewart approach to acid–basedisorders uses five equations of varying complexity to estimatethe base excess effects of the important components: the strongion difference (sodium and chloride), the total weak acid concentration(albumin) and unmeasured ions. Although this approach is straightforward,most people would need a calculator to use the equations. Weproposed four simpler equations that require only mental arithmeticand tested the hypothesis that these simpler equations wouldhave good agreement with more complex Fencl–Stewart equations. Methods. We reduced two complex equations for the sodium–chlorideeffect on base excess to one simple equation: sodium–chlorideeffect (meq litre^–1)=[Na⁺]–[Cl^–]–38.We simplified the equation of the albumin effect on base excessto an equation with two constants: albumin effect (meq litre^–1)=0.25x(42–[albumin]g litre^–1).Using 300 blood samples from critically ill patients, we examinedthe agreement between the more complex Fencl–Stewart equationsand our simplified versions with Bland–Altman analyses. Results. The estimates of the sodium–chloride effect onbase excess agreed well, with no bias and limits of agreementof –0.5 to 0.5 meq litre^–1. The albumin effectestimates required log transformation. The simplified estimatewas, on average, 90% of the Fencl–Stewart estimate. Thelimits of agreement for this percentage were 82–98%. Conclusions. The simplified equations agree well with the previous,more complex equations. Our findings suggest a useful, simpleway to use the Fencl–Stewart approach to analyse acid–basedisorders in clinical practice. Br J Anaesth 2004; 92: 54–60     

Use of sodium bicarbonate and blood gas monitoring in diabetic ketoacidosis: A review

Diabetic ketoacidosis (DKA) is a severe and too-common complication of uncontrolled diabetes mellitus. Acidosis is one of the fundamental disruptions stemming from the disease process, the complications of which are potentially lethal. Hydration and insulin administration have been the cornerstones of DKA therapy; however, adjunctive treatments such as the use of sodium bicarbonate and protocols that include serial monitoring with blood gas analysis have been much more controversial. There is substantial literature available regarding the use of exogenous sodium bicarbonate in mild to moderately severe acidosis; the bulk of the data argue against significant benefit in important clinical outcomes and suggest possible adverse effects with the use of bicarbonate. However, there is scant data to support or refute the role of bicarbonate therapy in very severe acidosis. Arterial blood gas (ABG) assessment is an element of some treatment protocols, including society guidelines, for DKA. We review the evidence supporting these recommendations. In addition, we review the data supporting some less cumbersome tests, including venous blood gas assessment and routine chemistries. It remains unclear that measurement of blood gas pH, via arterial or venous sampling, impacts management of the patient substantially enough to warrant the testing, especially if sodium bicarbonate administration is not being considered. There are special circumstances when serial ABG monitoring and/or sodium bicarbonate infusion are necessary, which we also review. Additional studies are needed to determine the utility of these interventions in patients with severe DKA and pH less than 7.0.     

Patient's satisfaction with perioperative care: development, validation, and application of a questionnaire

Background: Measuring patient satisfaction after anaesthesia care is complex.The existing patient satisfaction questionnaires are limitedand omit aspects of patient satisfaction, such as professionalcompetence, information provision, service, and staff–patientrelationship. The aim of our study was to develop a valid andreliable self-reported multidimensional questionnaire assessingpatient satisfaction that included these issues. Methods: The development of the Leiden Perioperative care Patient Satisfactionquestionnaire (LPPSq) was as follows: expert consultation, constructionof the pilot questionnaire, pilot study, statistical analysisof the results of the pilot study (validity, reliability, andfactor analysis), compilation of the definitive questionnaire,main study, and repeated statistical analysis (validity, reliability,and factor analysis). The overall patient satisfaction is expressedby the mean satisfaction score. Results: Three hundred and eighty-two patients consented to participatein the study; 80.4% of the patients (n=307) completed the questionnaire.The LPPSq isolated three dimensions: information (Cronbach’s=0.82), fear and concern (Cronbach’s =0.69), and staff–patientrelationship (Cronbach’s =0.94). Patient satisfactionwith perioperative care was not directly dependent on the outcomesof anaesthesia but how patients were approached and the amountof information they received. Age (P=0.001), gender (P=0.001),work situation (P=0.003), and specialty (P=0.017) were the characteristicsmost influencing patient satisfaction. Conclusions: We developed the LPPSq questionnaire to measure patient satisfactionwith perioperative care, of which anaesthesia care is an importantelement. In this study, information provision and the relationshipbetween staff and patient were the major determinants of patientsatisfaction.     

Noninvasive monitoring of rotary blood pumps: necessity, possibilities, and limitations

Although rotary blood pumps do not contain an inherent mechanism for adaptation to physiological flow necessities, hitherto only a few efforts have been made to obtain robust monitoring and control methods. This paper discusses the necessity of noninvasive monitoring of such pumps and the crucial points of sensor selection and development. A strategy of monitoring atrial pressure out of the data obtained by the collapse of the atrial wall around the inflow cannula and initial results on animal tests and computer simulation of this method are discussed. This approach might lead to reliable and demand-responsive controllers, if some basic criteria are fulfilled.     

Strabismus surgery and post-operative vomiting: clinical observations and review of the current literature; a medical opinion

This study documents the age-related incidence of vomiting in paediatric patients following strabismus surgery under a postoperative policy of delayed oral alimentation (3-6 h), minimized motion and the avoidance of anti-emetic medications. The incidence of vomiting prior to discharge was 4%. The average time from completion of surgery to discharge home was 84 min. The overall incidence of vomiting in the 24 h following surgery was 43%; almost half of this incidence occurred during the car ride home. Children 3 years of age or older were twice as likely to vomit than those younger than 3 years of age. A literature review finds that no drug has been shown by independent investigators to decrease consistently the incidence of vomiting following strabismus surgery. For most drugs, anti-emetic efficacy parallels the degree of sedation and prolongs recovery; once the sedative effects have abated, the incidence of vomiting approaches that in untreated patients. Our protocol allows for early discharge with the same expected incidence of post-discharge vomiting as reported for children receiving pharmacologic anti-emetic prophylaxis.     

血液回收技术中应用钠钾镁钙葡萄糖注射液对肝肾功能和血气指标的影响

目的评价钠钾镁钙葡萄糖注射液应用于血液回收技术中对患者肝肾功能和血气指标的影响。方法选择需行血液回收的神经外科手术患者60例,男31例,女29例,年龄19～67岁,BMI 21～25 kg/m~2,ASAⅠ或Ⅱ级。随机分为钠钾镁钙葡萄糖注射液组(N组)和生理盐水组(C组),每组30例。N组肝素冲管液采用低分子肝素钠25 000 IU加入钠钾镁钙葡萄糖注射液500 ml中配置,洗涤液全部应用钠钾镁钙葡萄糖注射液;C组肝素冲管液采用低分子肝素钠25 000 IU加入生理盐水500 ml中配置,洗涤液全部应用生理盐水。于血液回收前(T_0)、自体血输注完毕后(T_1)、手术后6 h(T_2)采集血样,检测ALT、AST、血清总胆红素(TBIL)、肌酐(Scr)、尿素氮(BUN)等肝肾功能指标;血氧饱和度50%时的氧分压(P_(50))、pH、血浆HCO_3~-、乳酸(Lac)、电解质(K~+、Na~+、Cl~-、Ca~(2+))、血糖(Glu)浓度等血气指标。结果与T_0时比较,T_1时C组BUN、Scr、Lac、Na~+、Cl~-、Glu浓度明显升高(P0.05),P_(50)明显升高(P0.05),pH和血浆HCO_3~-浓度以及K~+、Ca~(2+)浓度明显降低(P0.05)。与T_1时比较,T_2时C组BUN、Scr、Lac、Na~+、Cl~-、Glu浓度明显升高(P0.05),P_(50)明显升高(P0.05),pH和血浆HCO_3~-浓度以及K~+、Ca~(2+)浓度明显降低(P0.05)。与N组比较,T_1和T_2时C组BUN、Scr、Lac、Na~+、Cl~-、Glu浓度明显升高(P0.05),P_(50)明显升高(P0.05),pH和血浆HCO_3~-浓度以及K~+、Ca~(2+)浓度明显降低(P0.05)。两组不同时点AST、ALT、TBIL浓度差异无统计学意义。结论在血液回收中应用钠钾镁钙葡萄糖注射液配置肝素冲管液和洗涤液有利于减轻红细胞的损伤,改善红细胞携氧能力,维持内环境稳定和酸碱平衡,有利于保护患者肾功能,但对肝功能无明显影响。