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H H Korsten

Publications and source records attributed to H H Korsten.

At least 19 recordsLinked to original sources
PubMed2003

[Intensive care medicine in the Netherlands, 1997-2001. I. Patient population and treatment outcome].

OBJECTIVE: To describe the patients admitted to intensive care units (ICUs) in the Netherlands between 1997-2001 and the treatment outcome. DESIGN: Descriptive. METHOD: For the years 1997-2001, prospective admission and discharge data as well as all data necessary for calculating prospective severity of illness scores (e.g. APACHE II and SAPS II) were collected for all patients that were admitted to 18 ICUs participating in the Dutch National Intensive Care Evaluation (NICE). Outcome measures were ICU mortality and hospital mortality, length of hospital and ICU admission, and standardised mortality ratio (SMR). RESULTS: Data from 55,016 admissions were registered. The median APACHE II score was 15 (P25-P75: 10-20) and the median SAPS II score was 29 (19-43). The median ICU length of admission for individual ICUs varied between 0.86 and 2.76 days. The occupied ICU capacity of individual ICUs varied between 220 and 1260 days per 100 patients admitted for non-cardiosurgical patients and between 110 and 330 days per 100 patients admitted for cardiosurgical patients. The ICU mortality and hospital mortality were 9.0% and 12.9% respectively. The mean SMR according to APACHE II was 0.95 (95% CI: 0.93-0.98). The SMR of the individual participating hospitals varied between 0.55 (95% CI: 0.37-0.80) and 1.20 (1.13-1.28). CONCLUSION: Hospital mortality for ICU-admitted patients in the NICE registration was 12.9%. For patients who could be evaluated with the APACHE II model, actual hospital mortality was lower than predicted by this model. Significant differences in length of admission, hospital mortality and SMR were found between individual hospitals.

APACHE↗
PubMed2001

The application of ontologies and problem-solving methods for the development of shareable guidelines.

Recently, studies have shown the benefits of using clinical guidelines in the practice of medicine. Computer-based clinical guidelines are increasingly applied in diverse areas such as policy development, utilization management, education, conduct of clinical trials, and workflow facilitation. This paper discusses some of the representations suggested in literature, discusses their weak and strong points, and demonstrates and discusses a new approach that extends earlier developed formalisms by combining primitives, ontologies and the use of problem-solving methods (PSMs). The approach is supported by a framework that facilitates the entire guideline authoring process. The paper demonstrates this framework and presents examples of guidelines, PSMs and systems that were developed by means of this approach. The overall goal of this approach is to improve the acceptance of shareable guidelines and decision support systems in daily care by facilitating the guideline acquisition and execution phases.

Decision Support Systems, Clinical↗
PubMed2001

Design and implementation of a framework to support the development of clinical guidelines.

This paper describes and discusses a framework that facilitates the development of clinical guideline application tasks. The framework, named GASTON covers all stages in the guideline development process, ranging from the definition of models that represent guidelines to the implementation of run-time systems that provide decision support, based on the guidelines that were developed during the earlier stages. The GASTON framework consists of (1) a newly developed guideline representation formalism that uses the concepts of primitives, problem-solving methods (PSMs) and ontologies to represent the guidelines of various complexity and granularity and different application domains, (2) a guideline authoring environment that enables guideline authors to define the guidelines, based on the newly developed guideline representation formalism and (3) a guideline execution environment that translates defined guidelines into a more efficient symbol level representation, which can be read in and processed by an execution time engine. The paper describes a number of design criteria that were formulated regarding the aspects of guideline representation, guideline authoring and guideline execution and explains the framework by example in terms of the four stages that were identified in the guideline development process and the tools that were developed to support each stage. It also shows examples of systems that were developed by means of the GASTON framework.

Artificial Intelligence↗
PubMed2000

Right ventricular failure in acute respiratory distress syndrome.

Right ventricular failure can be the result of acute respiratory distress syndrome (ARDS). A patient with eclampsia and sepsis with Staphylococcus aureus developed life-threatening right ventricular failure as a result of ARDS. She finally stabilized after treatment with inhaled nitric oxide (NO). The pathophysiology of right ventricular failure in ARDS is described.

Administration, Inhalation↗
PubMed1999

A strategy for developing practice guidelines for the ICU using automated knowledge acquisition techniques.

OBJECTIVES: To implement practice guideline entry tools in a reminder system in order to provide decision support to health care workers in clinical care and emergency care environments. To design a knowledge acquisition environment that enables physicians to formulate, update, and verify guidelines without the assistance of a knowledge engineer. METHODS: We developed a knowledge acquisition environment for the Intensive Care Unit (ICU) consisting of 1) a graphical knowledge acquisition tool, 2) tools that perform logical and semantic tests on proposed guidelines, 3) a Patient Data Management System (PDMS) containing clinical patient data, and 4) an expert system that reminds ICU health care workers of inconsistencies between a treatment plan and implemented guidelines. Physicians enter the guidelines using the knowledge acquisition tool, after which consistency and correctness tests are performed on the guidelines. The guidelines are then transferred to the knowledge base of the reminder system and validated by applying the new guidelines to a large stored data set of previous patients. If the new guidelines are approved, they are exported to the reminder system that is used in daily practice. RESULTS: ICU physicians used the knowledge acquisition tool to enter 58 guidelines into the reminder system's knowledge base. These guidelines were tested on a data set consisting of 803 previously admitted patients. As a result, 27 guidelines fired at least once, generating 406 reminders in total. Of the 406 generated reminders, 356 (88%) were issued correctly and 50 (12%) were false alarms. The reminders that were issued correctly involved 3 situations: 1) the database contained inconsistent or incomplete information, 2) the actions or decisions of the health care workers were not the most appropriate ones, and 3) there was a potential risk involved. All false alarms were caused by the fact that the corresponding guidelines were not specific enough to handle certain exceptions. As a result of this analysis, the guidelines could be improved in such a way as to eliminate all false alarms. CONCLUSIONS: These first results demonstrate that this bottom-up knowledge acquisition strategy, implemented by the automated knowledge acquisition tools, enables medical specialists to improve the quality of computer support in an ICU without assistance of a knowledge engineer.

Artificial Intelligence↗
PubMed1997

Partition coefficients (n-octanol/water) of N-butyl-p-aminobenzoate and other local anesthetics measured by reversed-phase high-performance liquid chromatography.

For the determination of the logarithmic partition coefficients between n-octanol and water (log P(o/w)) of local anesthetics, the pH of the aqueous phase needs to be adjusted to high values to ensure that the local anesthetics are in the unionized form. Using the shake-flask or the stir-flask method, this high pH may catalyze hydrolysis, leading to increasing amounts of impurities in time. These impurities exclude non-selective quantification methods like UV spectrometry and require repetitive quantitative analysis of both liquid phases resulting in a tedious and time-consuming method. A rapid reversed-phase HPLC method was developed to measure log P(o/w) of the local anesthetics N-butyl-p-aminobenzoate, methyl-p-aminobenzoate, benzocaine, procaine, mepivacaine, prilocaine, lidocaine, bupivacaine, etidocaine, tetracaine and oxubuprocaine.

1-Octanol↗
PubMed1997

Event-related potential measures of information processing during general anesthesia.

To investigate the incidence and manner of auditory information processing during a state of presumed unconsciousness event-related brain potentials (ERPs) were studied in 41 patients undergoing cardiac surgery with propofol/alfentanil anesthesia. The ERPs were recorded during auditory oddball tasks administered before and within several periods of the operation. Mean nasopharyngeal temperature and anesthetic concentrations were determined for each intraoperative ERP recording epoch. During anesthesia ERP waves could still be observed up to 500 ms after stimulus onset indicating that auditory information processing was not suppressed completely by the administered anesthetic agents. Relative to the preoperative recordings, the P1-N1-P2 complex was delayed and more positive going during anesthesia. Comparable changes in ERP morphology have been observed during Stage II-IV sleep, suggesting parallels in the mechanisms underlying early auditory processing in both states of reduced arousal level, possibly related to a selective reduction of a non-specific activity. N1 and P2 peak amplitudes were found to be larger for the deviant tones compared to the standard tones. These amplitude differences most likely reflect automatic detection of stimulus deviance, although it cannot be excluded entirely that they were due to differences in refractoriness. Anesthetic concentrations and nasopharyngeal temperature were found to be of minor significance for ERP control. It is suggested that ERPs could serve as intraoperative reference measures, providing the earliest evidence for auditory processing. This characteristic is important for validation of signals and techniques that are proposed to improve conventional monitoring of anesthesia with respect to detecting unintended awareness.

Adult↗
PubMed1997

A randomized multicenter double-blind comparison of urapidil and ketanserin in hypertensive patients after coronary artery surgery.

OBJECTIVES: To compare the hemodynamic responses, safety, and efficacy of urapidil and ketanserin in hypertensive patients after coronary artery surgery. DESIGN: Randomized double-blind study. SETTING: Multi-institutional. PARTICIPANTS: One hundred twenty-two patients undergoing elective coronary artery surgery. INTERVENTIONS: When hypertension (defined as mean arterial pressure > 85 mmHg) developed within the first 2 hours after arrival in the intensive care unit, patients received urapidil (n = 62) or ketanserin (n = 60) to reach a mean arterial pressure between 65 and 75 mmHg. Urapidil was administered by repeated bolus injections (25 to 125 mg) followed by a continuous infusion of maximally 50 micrograms/kg/min. Ketanserin was administered by repeated bolus injections (10 to 50 mg) followed by a continuous infusion of maximally 4.0 micrograms/kg/min. MEASUREMENTS AND MAIN RESULTS: A complete hemodynamic profile was determined at baseline and at 30 and 60 minutes after start of study medication. In the urapidil group, mean arterial pressure (+/-SD) decreased significantly from 100.6 +/- 12.4 mmHg at baseline to 74.6 +/- 12.1 mmHg at 30 minutes and 73.5 +/- 13.8 mmHg at 60 minutes. In the ketanserin group, mean arterial pressure decreased significantly from 98.7 +/- 10.7 mmHg at baseline to 83.5 +/- 16.8 mmHg at 30 minutes and 83.1 +/- 15.3 mmHg at 60 minutes. Between the groups, there was a significant difference in the degree of lowering mean arterial pressure at 30 and 60 minutes. Heart rate increased significantly by 5.8 +/- 12.7 (30 minutes) and 8.6 +/- 16.5 (60 minutes) beats/min in the ketanserin group. In the urapidil group, no changes in heart rate occurred. Cardiac output increased to the same extent (0.7 L/min) in both groups. Within and between the groups, there were no relevant changes in pulmonary filling pressures. The number of patients not responding adequately to the study medication (mean arterial pressure > 85 mmHg after 30 minutes despite the maximum doses of study medication) was comparable in both groups (9 [U] v 13 [K]). Adverse events attributable to the study medication occurred to a similar degree in both groups. In the patients treated with urapidil, a significantly higher incidence (32.3%) of hypotension (mean arterial pressure < or = 65 mmHg for more than 10 minutes) occurred after 60 minutes of continuous infusion. CONCLUSIONS: In contrast to ketanserin, urapidil did not increase heart rate. Urapidil was more effective in lowering arterial blood pressure than ketanserin. However, one third of the patients treated with urapidil developed hypotension after 60 minutes of continuous infusion.

Aged↗
PubMed1997

Epidural and intrathecal n-butyl-p-aminobenzoate solution in the rat. Comparison with bupivacaine.

BACKGROUND: Epidural administration of an aqueous suspension of n-butyl-p-aminobenzoate (BAB) to humans results in long-lasting sensory blockade without motor block. The dose-response of BAB administered epidurally and intrathecally as a solution was studied in rats to define the local anesthetic properties in an established animal model. METHODS: The time course of changes in tail withdrawal latency and motor function were determined in rats after epidural or intrathecal administration of solutions of BAB or bupivacaine. The dose-response relation was determined and median effective dose values were calculated. RESULTS: After epidural and intrathecal administration of BAB solutions, the onset and duration of the antinociceptive action were comparable to bupivacaine. Median effective dose values for tail-withdrawal latency of 6 s or more were significantly greater for BAB. After both routes of administration, BAB clearly affected motor function. CONCLUSIONS: When administered epidurally and intrathecally as a solution, BAB is a local anesthetic of relative low potency with onset and duration of action comparable to those of bupivacaine. These findings suggest that the long-lasting action obtained after applying BAB suspension results from the slow dissolution (continuous release) of the solid BAB deposited in the epidural space.

Anesthesia, Epidural↗
PubMed1996

The local anesthetic, n-butyl-p-aminobenzoate, reduces rat sensory neuron excitability by differential actions on fast and slow Na+ current components.

Effects of the local anesthetic, n-butyl-p-aminobenzoate, at a concentration of 100 microM, were investigated using the whole-cell voltage clamp on dorsal root ganglion neurons cultured from neonatal rat in a serum-enriched medium. During current clamp conditions, the drug either increased the firing threshold or blocked tetrodotoxin-sensitive and tetrodotoxin-resistant Na+ action potentials. These actions were reversible. Under voltage clamp conditions, inactivation of the Na+ current revealed the existence of 3 fast Na+ current components, termed F1, F2 and F3 (tetrodotoxin-sensitive) and 2 slow ones, termed S1 and S2 (tetrodotoxin-resistant). The local anesthetic shifted the midpoint potentials of Na+ inactivation curves for F1, F2 and F3 currents by 7, 21 and 6 mV, respectively, towards hyperpolarizing membrane voltages whereas it did not influence these potentials for the slow currents. The amplitudes of only F3 and S2 currents were reduced by n-butyl-p-aminobenzoate to 24 and 11%, respectively, of their control values. These results show that the local anesthetic has a differential mode of action on the 5 types of Na+ currents, which are apparently present in cultured sensory neurons. This differential action can play an important role in the selective analgesic effect observed after epidural administration of a 10% n-butyl-p-amino-benzoate suspension.

Action Potentials↗
PubMed1996

Optimal surface electrode positioning for reliable train of four muscle relaxation monitoring.

In the clinic, a major problem in train of four (TOF) muscle relaxation monitoring is incorrect placement of stimulation and recording electrodes, frequently resulting in incorrect estimates of the patient's degree of relaxation or in abandonment of relaxation monitoring. The aim of this study was to arrive at recommendations that describe how to find optimal positions for the electrodes, where 'optimal' is taken in the sense that small deviations from these positions introduce no or only a small decline in the accuracy of the computed degree of muscle relaxation. This study, which employed the Relaxograph as the stimulation and measuring device, established that incorrect positioning is a real problem that frequently occurs; that the correctness of positioning is not guaranteed when the calibration of the Relaxograph succeeds; that the inadequacy of the electrode position is sometimes discovered for the first time when relaxation deepens; that positioning errors can be discovered by analysing the shape of the evoked compound action potential (ECAP), not only upon calibration but also when relaxation deepens; that a set of optimal electrode positions can be found; and that recommendations of how to find these optimal positions could help clinicians to place the electrodes in such a way, that reliable relaxation monitoring was possible in 100% of the investigated cases. In a first test in 30 adult patients, we surveyed how clinicians routinely positioned electrodes and found that in 14 of the 30 cases positioning was unsuccessful. In a second test in 10 patients, we tested a variety of electrode positions in order to discover 'optimal' stimulation, recording and ground electrode sites. In a third test in 10 patients, electrodes were positioned at these 'optimal' sites; stimulation and recording at these sites was successful in all 10 cases.

Adult↗
PubMed1996

Haemodynamic responses to incision and sternotomy in relation to the auditory evoked potential and spontaneous EEG.

We investigated the effect of incision and sternotomy on the auditory evoked potential (AEP) and EEG, to try to predict a haemodynamic response to incision or sternotomy using the AEP and EEG in 41 patients undergoing cardiac surgery during propofol and alfentanil anaesthesia. The AEP and EEG were recorded before incision, between incision and sternotomy, and after sternotomy. Peak latencies and amplitudes of AEP peaks V, Na, Pa, Nb, Pb and Nc were determined. From the EEG the median, spectral edge and peak power frequencies, and percentages of delta, theta, alpha and beta power were calculated. Each patient was classified as responsive, equivocally responsive or unresponsive to incision or sternotomy based on increase in arterial pressure and heart rate on incision and sternotomy. Before incision, Nb and Pb latency and propofol concentration were higher for unresponsive patients but heart rate and median frequency before incision were lower. After sternotomy, Pa and Nb amplitude, peak power frequency and percentage alpha power were higher, and percentage theta power lower for responsive patients. Pa latency was higher after sternotomy for unresponsive patients. Using a combination of heart rate, arterial pressures and features derived from the AEP (all recorded before incision), the occurrence of a response to incision could be predicted in individual patients with a sensitivity of 85%, positive predictive accuracy of 63% and total accuracy of 72%. We conclude that AEP are more sensitive to pain stimuli than spectral features of the spontaneous EEG. In addition, the AEP may help in predicting inadequate anaesthesia.

Adult↗
PubMed1996

Midlatency auditory evoked potentials as indicators of perceptual processing during general anaesthesia.

We tested the hypothesis that midlatency auditory evoked potentials (MLAEP) can predict the occurrence of long latency AEP components (LLAEP), which are taken as evidence for perceptual processing. Forty-one patients undergoing cardiac surgery were anaesthetized with propofol and alfentanil. During several periods of surgery we recorded LLAEP. Peak-to-peak amplitude measures were used to determine if a particular LLAEP recording trace contained a recognizable waveform. Both before and after each LLAEP recording epoch, MLAEP and the spontaneous electroencephalogram (EEG) were recorded. Peak latencies and amplitudes of brainstem peak V and midlatency peaks Na, Pa, Nb, Pb and Nc, characteristic frequencies from the spontaneous EEG, mean arterial pressure (MAP) and nasopharyngeal temperature (7) were compared between recording epochs with and without clear LLAEP waveforms. These variables were also used in a discriminant analysis to predict the occurrence of an LLAEP waveform. Pa and Nb latencies were significantly shorter both before and after recording epochs in which an LLAEP waveform occurred, compared with epochs in which no LLAEP waveform occurred. Using a combination of up to six EEG, MLAEP, MAP and T measures, it was possible to predict the occurrence or absence of an LLAEP waveform with a sensitivity of 89% and specificity of 86%. We conclude that MLAEP components provide information on the possibility of perceptual processing during general anaesthesia, and thus may be relevant for monitoring depth of anaesthesia.

Adult↗
PubMed1995

Capillary gas chromatographic method for the determination of n-butyl-p-aminobenzoate and lidocaine in plasma samples.

A fast capillary gas chromatographic method with nitrogen-selective detection is described that allows selective and reproducible quantification of n-butyl-p-aminobenzoate (BAB) and lidocaine in plasma. The sampling and sample storage conditions are critical for the quantification of BAB. Diisopropyl fluorophosphate, an organo-phosphorus pesticide, has to be added during sampling to prevent the rapid decomposition of BAB by cholinesterases.

Anesthetics, Local↗
PubMed1995

Information processing during cardiac surgery: an event related potential study.

The aim of this study was to investigate whether information processing persists during general anesthesia, and if so, to determine the relationship between the degree of cognitive processing measured during anesthesia and the presence or absence of intraoperative memories measured after anesthesia. Subjects were 12 patients, undergoing cardiac surgery with propofol/alfentanil anesthesia. During several periods of the operation, event related potentials (ERPs) to frequent and infrequent tones of different pitch were analyzed. After the operation, a word recognition task with ERP recording was administered to determine whether intraoperatively presented words would elicit a (covert) recognition reaction in the brain. ERP wave forms could be obtained during the intraoperative recording periods but differed substantially from those in the awake state. The presence of ERP components up to 500 msec after stimulus presentation suggests that auditory information processing continued during anesthesia up to a certain level of cognition. Intraoperative ERPs to frequent and infrequent tones were not different from each other implying that differences in pitch could not be detected. The postoperative results demonstrated evidence for intraoperative memories in 3 patients. For 2 of these 3 patients, low propofol levels as well as reliable ERPs with large amplitudes were found close to the moment of information presentation. The results emphasize the importance of combining intra- and postoperative measurements and suggest that late ERP components might be used as indicators of an increased risk of auditory perception.

Acoustic Stimulation↗
PubMed1995

The local anesthetic n-butyl-p-aminobenzoate selectively affects inactivation of fast sodium currents in cultured rat sensory neurons.

BACKGROUND: Aqueous suspensions of the local anesthetic n-butyl-p-aminobenzoate (BAB), epidurally applied in terminal cancer patients, resulted in a sensory blockade, lasting up to several months. To investigate the mechanism of action on the cellular level, the effect of 100 microM BAB on Na+ action potentials and on Na+ currents in dorsal root ganglion neurons from neonatal rats was studied. METHODS: Small neurons grown in cell culture were selected for patch-clamp measurements. Both Na+ action potentials, evoked by current pulses of increasing amplitude (current clamp) and Na+ currents, activated at different membrane potentials (voltage clamp), were investigated in the absence and presence of 100 microM BAB. The local anesthetic was applied by external perfusion for 2 or 10 min. RESULTS: In the presence of 100 microM BAB, either the firing threshold was raised or the action potential was abolished. The maximal peak conductances, underlying the fast sodium current INa,F and the slow sodium current INa,5, were not changed. However, the inactivation of INa,F was increased by BAB. The sigmoid inactivation curve shifted 12 mV toward hyperpolarizing membrane voltages, whereas no changes were found for the inactivation of the slow Na+ current. Only at short exposure times of 2 min, the effects of BAB could be reversed during a 10-min wash-out. CONCLUSIONS: BAB dramatically increased the firing threshold, and in part of the sensory neurons, it blocked the action potential. The inactivation of the fast Na+ channels, but not of the slow Na+ channels, was increased by BAB. Thus, the block of fast Na+ channels by BAB may contribute to epidural analgesia. At exposure times of 10 min, the effect of BAB was not reversible. This probably originates from its high lipid-solubility, which may be an important factor in determining the duration of the block in vivo.

Action Potentials↗