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M Sydow

Publications and source records attributed to M Sydow.

At least 19 recordsLinked to original sources
PubMed1998

Determination of functional residual capacity (FRC) by multibreath nitrogen washout in a lung model and in mechanically ventilated patients. Accuracy depends on continuous dynamic compensation for changes of gas sampling delay time.

OBJECTIVE: Validation of an open-circuit multibreath nitrogen washout technique (MBNW) for measurement of functional residual capacity (FRC). The accuracy of FRC measurement with and without continuous viscosity correction of mass spectrometer delay time (TD) relative to gas flow signal and the influence of baseline FIO2 was investigated. DESIGN: Laboratory study and measurements in mechanically ventilated patients. SETTING: Experimental laboratory and anesthesiological intensive care unit of a university hospital. PATIENTS: 16 postoperative patients with normal pulmonary function (NORM), 8 patients with acute lung injury (ALI) and 6 patients with chronic obstructive pulmonary disease (COPD) were included. INTERVENTIONS: Change of FIO2 from baseline to 1.0. MEASUREMENTS AND MAIN RESULTS: FRC was determined by MBNW using continuous viscosity correction of TD(TDdyn), a constant TD based on the viscosity of a calibration gas mixture (TD0) and a constant TD referring to the mean viscosity between onset and end of MBNW (TDmean). Using TDdyn, the mean deviation between 15 measurements of three different lung model FRCs (FRCmeasured) and absolute volumes (FRCmodel) was 0.2%. For baseline FIO2 ranging from 0.21 to 0.8, the mean deviation between FRCmeasured and FRCmodel was -0.8%. However, depending on baseline FIO2, the calculation of FRC using TDmean and TD0 increased the mean deviation between FRCmeasured and FRCmodel to 2-4% and 8-12%, respectively. In patients (n = 30) the average repeatability coefficient was 6.0%. FRC determinations with TDmean and TD0 were 0.8-13.3% and 4.2-23.9% (median 2.7% and 8.7%) smaller than those calculated with TDdyn. CONCLUSION: A dynamic viscosity correction of TD improves the accuracy of FRC determinations by MBNW considerably, when gas concentrations are measured in a sidestream. If dynamic TD correction cannot be performed, the use of constant TDmean might be suitable. However, in patient measurements this can cause an FRC underestimation of up to 13%.

Adult↗
PubMed1998

Evaluation of respiratory inductive plethysmography in controlled ventilation: measurement of tidal volume and PEEP-induced changes of end-expiratory lung volume.

STUDY OBJECTIVE: To determine the accuracy of respiratory inductive plethysmography (RIP) with a respiratory monitor (Respitrace Plus; NIMS Inc., Miami) operating in the DC-mode for the measurement of tidal volumes (VT) and positive end-expiratory pressure (PEEP)-induced changes of end-expiratory lung volume (deltaEELV) in patients with normal pulmonary function, acute lung injury (ALI), and COPD during volume-controlled ventilation. DESIGN: Prospective comparison of RIP with pneumotachography (PT) for assessment of VT and with multibreath nitrogen washout procedure (N2WO) for determination of deltaEELV as reference methods. SETTING: Mixed ICU at a university hospital. PATIENTS: Thirty-one sedated and paralyzed patients: 12 patients with normal pulmonary function mechanically ventilated after major surgery, 10 patients with respiratory failure due to ALI, and 9 patients with a known history of COPD ventilated after surgery or because of respiratory failure due to bronchopulmonary infection. INTERVENTIONS: Stepwise increase of PEEP from 0 to 5 to 10 cm H2O and reduction to 0 cm H2O again. On each PEEP level, N2WO was performed. MEASUREMENTS AND MAIN RESULTS: The baseline drift of RIP averaged 25.4+/-29.1 mL/min but changed over a wide range even in single patient measurements. Determination of VT for single minutes revealed that 66.5% and 90.0% of all values were accurate within a range of +/-10% and +/-20%, respectively. The deviation for VT measurements between RIP and PT in patients with COPD was significantly (p<0.05) higher compared to patients with ALI or normal pulmonary function. The difference of deltaEELV between RIP and N2WO was 11.6+/-174.1 mL with correlation coefficients of 0.77 (postoperative and COPD patients) and 0.86 (ALI patients). However, just 25.8% and 46.2% were precise within +/-10% and +/-20%, respectively. deltaEELV determination in COPD patients differed more between RIP and N2WO than in the other groups, but this was not significant. CONCLUSION: In a mixed group of patients undergoing controlled ventilation, RIP using the Respitrace Plus monitor was not consistently precise enough for quantitative evaluation of VT and EELV when compared to our reference methods. This was most evident in patients with COPD. For long-term volume measurements, a better control of the baseline drift of RIP should be achieved.

Aged↗
PubMed1997

Variation of nitric oxide concentration during inspiration.

OBJECTIVE: To evaluate the pattern of inspiratory nitric oxide concentration in a simple, constant flow delivery system during the use of two phasic-flow ventilatory modes. DESIGN: Laboratory study in a lung model. SETTING: University experimental laboratory. SUBJECT: Nitric oxide (800 ppm in nitrogen) was administered continuously into the inspiratory circuit to deliver a nitric oxide concentration of 10 and 40 ppm to a test lung during volume-controlled (constant flow) and pressure-controlled (decelerating flow) ventilation, with an FIO2 of 1.0. INTERVENTIONS: In each mode, minute ventilation of 7, 14, and 21 L/min and installation of mixing chambers (none, 1-L, 2-L, and 3.2-L turbulence boxes) were studied, respectively. Nitric oxide and nitric dioxide were monitored by chemiluminescence. Since the nitric oxide/nitrogen gas is the only nitrogen source in the system during ventilation with an FIO2 of 1.0, we evaluated the fluctuation in the inspiratory nitric oxide (NOx) concentration by measuring nitrogen with a fast-response analyzer. To test the effect of the measurement site, we measured nitric oxide concentrations using chemiluminescence at different positions in the inspiratory and expiratory limbs, with and without the mixing chambers, with a minute ventilation of 14 L/min and a nitric oxide concentration of 40 ppm. MEASUREMENTS AND MAIN RESULTS: Nitrogen dioxide production was not influenced by the flow pattern. During a nitric oxide concentration of 10 ppm, nitrogen dioxide was always < 0.6 ppm. During a nitric oxide concentration of 40 ppm, the highest nitrogen dioxide (4.47 ppm) concentration was found at the lowest minute ventilation and the largest inspiratory circuit volume. Nitric oxide values displayed by chemiluminescence indicated stable concentrations at all settings. However, without mixing chambers, NOx concentration calculated from nitrogen measurements demonstrated marked inspiratory fluctuations and was highest with a minute ventilation of 21 L/min and higher during pressure-controlled ventilation compared with volume-controlled ventilation (nitric oxide concentration of 40 ppm, pressure-controlled ventilation: 14.5 to 130.5 ppm; volume-controlled ventilation: 21.6 to 104.7 ppm; nitric oxide concentration of 10 ppm, pressure-controlled ventilation: 3.2 to 30.9 ppm; volume-controlled ventilation: 4.5 to 27.1 ppm). NOx concentration fluctuation decreased with an increasing mixing chamber, and was negligible at all settings with the 3.2-L turbulence box. Nitric oxide concentration fluctuation influenced chemiluminescence measurements. The displayed nitric oxide values varied, depending on the sampling site, and did not accurately reflect mean inspiratory nitric oxide concentration. Incorporation of a mixing chamber eradicated this sampling site influence. CONCLUSIONS: Continuous flow delivery of nitric oxide into the circuit of a phasic-flow ventilator results in marked inspiratory nitric oxide concentration fluctuation that is not detected by a slow-response chemiluminescence analyzer. Moreover, nitric oxide concentration fluctuation can influence the accuracy of the chemiluminescence measurements. These effects can be diminished by using additional mixing chambers to facilitate a stable gas concentration. As these mixing volumes increase the contact time of nitric oxide with oxygen, an increase of nitrogen dioxide has to be taken into account.

Lung↗
PubMed1997

Flow-proportional administration of nitric oxide with a new delivery system: inspiratory nitric oxide concentration fluctuation during different flow conditions.

OBJECTIVE: To evaluate the accuracy of a flow-proportional delivery system and the pattern of inspiratory nitric oxide (NO) concentration during different flow conditions. DESIGN: Laboratory study in a lung model. SETTING: University experimental laboratory. SUBJECT: With a new delivery system, NO was administered proportional to the inspiratory flow into the inspiratory circuit to deliver a NO concentration of 10 and 30 ppm to a test lung during different ventilatory modes (volume-controlled ventilation [VCV], pressure-controlled ventilation [PCV], and airway pressure release ventilation [APRV]) with a fraction of inspired oxygen (FIO2) of 1.0. INTERVENTIONS: During VCV and PCV, the flow pattern was varied to achieve tidal volumes of 300, 600, and 900 mL, respectively, with inspiratory to expiratory time ratios of 1:3, 1:2, and 1:1. APRV was studied at a minute volume of 6, 12, and 18 L. Nitric oxides (NOx [NO+NO2]) and nitric dioxide (NO2) were monitored by chemiluminescence and electrochemical analysis. As the NO/N2 gas mixture is the only nitrogen source during ventilation with an FIO2 analyzer. RESULTS: During all flow conditions, NOx concentration was stable but slightly higher than expected. Measured and expected mean concentrations differed <9% (mean, <4%). Inspiratory NOx concentration fluctuation derived from N2 concentration was significantly higher than expected at higher flow rates, but this difference was not detected by chemiluminescence or electrochemical analysis. The NO2 production was not affected by the flow rate and was always < or =0.2 ppm (NO, 10 ppm) and < or =1.9 ppm (NO, 30 ppm). CONCLUSION: The tested NO delivery module administered stable mean inspiratory NO concentrations. Although inspiratory NO concentration fluctuates depending on the inspiratory flow rate, this delivery device allows stable NO administration without requiring adjustments when ventilator settings are changed.

Equipment Design↗
PubMed1996

[Variation in inspiratory gas flow in pressure support ventilation. The effect on respiratory mechanics and respiratory work].

UNLABELLED: During pressure support ventilation (PSV), the timing of the breathing cycle is mainly controlled by the patient. Therefore, the delivered flow pattern during PSV might be better synchronised with the patient's demands than during volume-assisted ventilation. In several modern ventilators, inspiration is terminated when the inspiratory flow decreases to 25% of the initial peak value. However, this timing algorithm might cause premature inspiration termination if the initial peak flow is high. This could result not only in an increased risk of dyssynchronization between the patient and the ventilator, but also in reduced ventilatory support. On the other hand, a decreased peak flow might inappropriately increase the patient's inspiratory effort. The aim of our study was to evaluate the influence of the variation of the initial peak-flow rate during PSV on respiratory pattern and mechanical work of breathing. PATIENTS: Six patients with chronic obstructive pulmonary disease (COPD) and six patients with no or minor nonobstructive lung pathology (control) were studied during PSV with different inspiratory flow rates by variations of the pressurisation time (Evita I, Drägerwerke, Lübeck, Germany). During the study period all patients were in stable circulatory conditions and in the weaning phase. METHOD: Patients were studied in a 45 degrees semirecumbent position. Using the medium pressurization time (l s) during PSV the inspiratory pressure was individually adjusted to obtain a tidal volume of about 8 ml/kg body weight. Thereafter, measurements were performed during five pressurization times (< 0.1, 0.5, 1, 1.5, 2 s defined as T 0.1, T 0.5, T 1, T 1.5 and T 2) in random order, while maintaining the pressure support setting at the ventilator. Between each measurement steady-state was attained. Positive end-exspiratory pressure (PEEP) and FIO2 were maintained at prestudy levels and remained constant during the study period. Informed consent was obtained from each patient or his next of kin. The study protocol was approved by the ethics committee of our medical faculty. Gas flow was measured at the proximal end of the endotracheal tube with a pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure (Paw) was determined in the same position with a second differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). Esophageal pressure (Pes) was obtained by a nasogastric balloon-catheter (Mallinckrodt, Argyle, NY, USA) connected to a further differential pressure transducer of the same type as described above. The balloon was positioned 2-3 cm above the dome of the diaphragm. The correct balloon position was verified by an occlusion test as described elsewhere. The data were sampled after A/D conversion with a frequency of 20 Hz and processed on an IBM-compatible PC. Software for data collection and processing was self-programmed using a commercially available software program (Asyst 4.0, Asyst Software Technologies, Rochester, NY, USA). Patient's inspiratory work of breathing Wpi (mJ/l) was calculated from Pes/ volume plots according to the modified Campbell's diagram. Dynamic intrinsic PEEP (PEEPidyn) was obtained from esophageal pressure tracings relative to airway pressure as the deflection in Pes before the initiation of inspiratory flow Patient's additive work of breathing (Wadd) against ventilator system resistance was calculated directly from Paw/V tracings when Paw was lower than the pressure on the compliance curve. Two-way analysis of variance (ANOVA) was used for statistical analysis, followed by post hoc testing of the least significant difference between means for multiple comparisons. Probability values less than 0.05 were considered as significant. RESULTS: COPD patients had significantly higher pressure support than control patients. With decreasing inspiratory flow, Wpi increased significantly in COPD patients.(ABSTRACT TRUNCATED)

Adult↗
PubMed1995

Effect of low-level PEEP on inspiratory work of breathing in intubated patients, both with healthy lungs and with COPD.

OBJECTIVE: Evaluation of low-level PEEP (5 cm H2O) and the two different CPAP trigger modes in the Bennett 7200a ventilator (demand-valve and flow-by trigger modes) on inspiratory work of breathing (Wi) during the weaning phase. DESIGN: Prospective controlled study. SETTING: The intensive care unit of a university hospital. PATIENTS: Six intubated patients with normal lung function (NL), ventilated because of non-pulmonary trauma or post-operative stay in the ICU, and six patients recovering from acute respiratory failure due to exacerbation of chronic obstructive pulmonary disease (COPD), breathing either FB-CPAP or DV-CPAP with the Bennett 7200a ventilator. INTERVENTIONS: The patients studied were breathing with zero end-expiratory pressure (ZEEP), as well as CPAP of 5 cm H2O (PEEP), with the following respiratory modes: the demand-valve trigger mode, pressure support of 5 cm H2O, and the flow-by trigger mode (base flow of 20 l/min and flow trigger of 2 l/min). Furthermore, Wi during T-piece breathing was evaluated. MEASUREMENTS AND RESULTS: Wi was determined using a modified Campbell's diagram. Total inspiratory work (Wi), work against flow-resistive resistance (W(ires)), work against elastic resistance (Wiel), work imposed by the ventilator system (W(imp)), dynamic intrinsic positive end-expiratory pressure (PEEPidyn), airway pressure decrease during beginning inspiration (P(aw)) and spirometric parameters were measured. In the NL group, only minor, clinically irrelevant changes in the measured variables were detected. In the COPD group, in contrast, PEEP reduced Wi and its components W(ires) and Wiel significantly compared to the corresponding ZEEP settings. This was due mainly to a significant decrease in PEEPidyn when external PEEP was applied. Flow-by imposed less Wi on the COPD patients during PEEP than did demand-valve CPAP. Differences in W(imp) between the flow-by and demand-valve trigger models were significant for both groups. However, in relation to Wi these differences were small. CONCLUSION: We conclude that the application of low-level external PEEP benefits COPD patients because it reduces inspiratory work, mainly by lowering the inspiratory threshold represented by PEEPidyn. Differences between the trigger modes of the ventilator used in this study were small and can be compensated for by the application of a small amount of pressure support.

Acute Disease↗
PubMed1995

[The determination of total protein is not a suitable diagnosis for the treatment of hypoalbuminemia in intensive care patients].

In clinical practice, the administration of supplementary albumin often depends on the measured plasma concentration of total protein (TPC). A TPC of less than 5 g/dl is generally accepted as an indication for albumin therapy, assuming an albumin concentration of less than 2.5 g/dl. However, a physiological relation between TPC and albumin cannot be expected in critically ill patients, and thus, measurement of TPC may be misleading as an indicator for the use of albumin. Therefore, we investigated the sensitivity and specificity of TPC testing for diagnosing hypoalbuminaemia requiring treatment. METHODS. In this prospective study, 210 consecutive patients were included. Protein electrophoresis was performed three times a week; the second electrophoresis was selected for evaluation. Applied statistical analysis revealed the number of positive total protein tests indicating hypoalbuminaemia requiring treatment (sensitivity) and the number of negative with tolerable reduced albumin concentrations (specificity). RESULTS. Of the investigated patients, 27.6% had normal TPCs between 6.2 and 8.0 g/dl. In 81.9% of cases an albumin concentration below 3.5 g/dl was found, while 43 patients had a concentration below 2.5 g/dl. The sensitivity and specificity of TPC measurement for the diagnosis of clinically relevant hypoalbuminaemia (albumin concentration < 2.5 g/dl) was calculated at different cutoff points for total protein. With a TPC of 6.0 g/dl, the sensitivity was 0.96 and the specificity 0.44. With a cutoff point of 5.0 g/dl, the sensitivity was reduced to 0.65 and specificity increased to 0.86. Finally, with a TPC of 4.0 g/dl sensitivity was 0.25 and specificity almost 1. CONCLUSIONS. Depending on the cutoff point for TPC, a relevant albumin requirement would frequently not be detected. In other cases, a need for albumin would be assumed from a reduced TPC even though the albumin concentration still exceeded 2.5 g/dl. Therefore, determination of TPC is not a suitable indicator of the need for albumin replacement. As a result, we suggest routine determination of albumin concentrations instead of TPC.

Adolescent↗
PubMed1994

[Determination of intrinsic PEEP during mechanical ventilation. Validation of a new optional method of measurement provided by the EVITA mechanical ventilator].

Intrinsic positive end-expiratory pressure (PEEPi) occurring during mechanical ventilation depends on expiratory time constants, expiratory volume and expiration time as well as on external flow resistance (tubes, valves, etc.). It is not routinely determined in mechanically ventilated patients, but it is necessary to optimize respirator settings. The aim of the present study was the validation of an automated PEEPi determination method implemented in the respirator EVITA (Drägerwerke, Lübeck) in mechanically ventilated patients with acute lung failure. PATIENTS. The method was validated in ten sedated, myorelaxed patients with respiratory insufficiency of different etiologies (five with restrictive, and five with obstructive pulmonary disease). PEEPi was determined using the volume constant ventilatory mode at ZEEP or at an external PEEP of 5 as well as 10 cm H2O. METHOD. PEEPi was first determined with the automated method implemented in the EVITA (five measurements at each end-expiratory pressure level; PEEPEvita). Steady-state was attained between each measurement. These values were compared to the results obtained with end-expiratory occlusion (external, computer-controlled valve in the inspiratory limb of the circuit) at the respective pressure levels (PEEPEEO). The average of five measurements at each PEEP level with each method was defined as PEEPi for the particular ventilatory situation. Gas flow was measured at the proximal end of the endotracheal tube with a heated pneumotachometer (Fleisch no. 2, Fleisch, Lausanne, Switzerland) and a differential pressure transducer. Tracheal pressure was determined in the same position with a further differential pressure transducer (Dr. Fenyves & Gut, Basel, Switzerland). After A/D conversion, data were sampled with a frequency of 20 Hz and processing as well as for control of the occlusion valve was self-programmed. For the statistical analysis we used the Mann-Whitney U-test or Wilcoxon signed-ranks test; a P value less than 0.05 was considered significant. RESULTS. At the given respiratory setting and without PEEP patients with obstructive lung disease had a higher PEEPi (median: 6.4 cm H2O; range: 5.0-9.6 cm H2O) than those with restrictive pulmonary disease (median: 2.3 cm H2O; range: 0.8-3.0 cm H2O) (P < 0.05). Increasing external PEEP to 5 or 10 cm H2O significantly decreased the pressure difference between PEEPi and external PEEP (P < 0.05), but was unable to eliminate it completely. There was no statistically significant difference between PEEPEEO and PEEPEvita (P = 0.43; Wilcoxon signed-ranks tests). Regression analysis showed a highly significant correlation between PEEPEEO and PEEPEvita values (r = 0.985, P < 0.001; y = 1.03 x-0.18). DISCUSSION. PEEPi occurs during ventilation in patients with obstructive and restrictive lung disease. The difference between external end-expiratory pressure and PEEPi decreases with increasing external PEEP. However, PEEPi may increase with increasing external PEEP in some instances. The reason for this may be that the PEEPi determined at the proximal end of the endotracheal tube represents only a mean value of different PEEPi values of various lung regions. Increasing external PEEP only partially alters this mean value due to an effect on PEEPi values lower than external PEEP. The PEEPi values measured by the EVITA respirator compared with classical end-expiratory occlusion with an external valve were nearly identical. Unfortunately, PEEPi measurement of the EVITA can only be performed during controlled and not during assisting (PSV, BIPAP etc.) ventilation. Optimal respirator settings require a knowledge of PEEPi (i.e., adaption of external PEEP for lowering the work of breathing in COPD patients or prolongation of the expiratory phase to avoid unwanted side effects of an occult PEEPi on the circulation). Since mo

Aged↗
PubMed1994

[Fulminating E. coli sepsis in Fournier's gangrene].

Fournier's gangrene is a necrotising soft-tissue infection of the scrotum and perineal region caused by gram-negative and gram-positive Enterobacteriaceae. The disease is characterised by its unique appearance, its speed of onset, and its high mortality. CASE REPORT. A 26-year-old male presented to the emergency room complaining of a painful, tremendously swollen scrotum and penis (Fig. 1) that had developed within the past 24 h. Later, slurred speech, pallor, and hypotension were recognised, leading to the patient's admission to the intensive care unit. Suspecting a severe internal haemorrhage, vigorous volume therapy was started using crystalloids and colloids until blood and fresh frozen plasma were available. One hour later, septic shock was presumed and therapy augmented by IV antibiotics, tracheal intubation, and mechanical ventilation. Despite all efforts, the patients condition deteriorated rapidly and he died a few hours later due to multiple organ failure in septic shock. Postmortem, a perforated external hemorrhoidal node was found to be the primary focus of sepsis. Microbiologic cultures revealed Escherichia coli in blood and tissue samples. DISCUSSION. Fournier's gangrene is a rare disease; nevertheless, its clinical picture has to be recognised immediately in order to provide appropriate treatment in time. It occurs predominantly in males after minor trauma, colorectal or urological disease, and perineal or abdominal surgery. Fournier's gangrene usually begins with itching and pain in the scrotal region followed by swelling and dark-blueish discolouration of the scrotum and penis, occasionally including the lower abdominal wall. Fever and chills are usually present. The illness progresses to severe prostation and septic shock with a mortality of 20%-50%. Tissue cultures mostly reveal E. coli, gram-positive enterococci, Pseudomonas, Proteus, and various anaerobes. The treatment should include immediate radical surgical debridement, i.v. administration of broad-spectrum antibiotics, and cardiopulmonary support. CONCLUSION. The dramatic course of Fournier's gangrene requires early recognition, extensive surgical debridement, as well as intensive care treatment in order to prevent irreversible septic shock.

Adult↗
PubMed1994

[Total intravenous anesthesia with methohexital-alfentanil or propofol-alfentanil in hypogastric laparotomy. Clinical aspects and the effects of stress reaction].

Total intravenous anaesthesia (TIVA) using a combination of a hypnotic and an analgesic agent is gaining increasing popularity as an alternative to balanced anaesthesia with volatile anaesthetics for abdominal surgery. Among the required characteristics of the drugs used in this technique are a good correlation between dose, plasma concentrations, and effect as well as rapid elimination from the circulation, allowing close control of anaesthetic depth. Two hypnotic drugs with similar pharmacokinetic and pharmacodynamic profiles are propofol and methohexitone, both of which can be employed as a component of a TIVA technique. Two TIVA combinations utilising either of these drugs with alfentanil were tested against isoflurane-nitrous oxide in a balanced regimen. METHODS. Twenty-seven healthy women undergoing hysterectomy for non-malignant diseases participated in the study after having given written consent. They were randomly allocated to receive either isoflurane (Iso), methohexital-alfentanil (M-A), or propofol-alfentanil (P-A). Blood samples for determination of cortisol, prolactin, catecholamines, glucose, lactate, non-esterified fatty acids, and pharmacon concentrations were drawn repeatedly from before induction until 360 min after surgery. Anaesthesia was induced in group Iso with fentanyl 0.1 mg and M 1.5 mg.kg-1 and maintained with Iso-N2O. In the TIVA groups M or P was given in a two-step infusion to load peripheral compartments and then maintain plasma concentrations within the hypnotic range. A was given as a continuous infusion in an identical dose (0.1 mg.kg-1 initial, 0.125 mg.kg-1.h-1 maintenance) in both groups. If signs of insufficient depth of anaesthesia occurred (heart rate or systolic blood pressure > 25% above baseline), then first A (0.5-1 mg), and if that was ineffective, then 50 mg hypnotic was administered. The A infusion was stopped 30 min before the end of surgery, and Iso or the hypnotic was stopped at skin closure. Recovery time was the time until the patients were able to give their birth date after stopping the Iso or hypnotic. RESULTS. The three groups were comparable with regard to age, weight, and duration of surgery. The total doses of M and P were 1,357 +/- 125 mg (mean +/- SEM) and 1,315 +/- 121 mg, respectively, and the total A doses were 20.7 +/- 2.5 mg (M-A) and 23.4 +/- 3.5 (P-A). The peak plasma concentrations were P 10.6 +/- 1.5 micrograms.ml-1 and M 12.4 +/- 2.6 micrograms.ml-1. At the end of surgery the P concentrations were in the projected range while those of M were somewhat lower than expected (P 3.7 +/- 0.4 microgram.ml-1; M 3.5 +/- 0.6 microgram.ml-1). Three patients each in the P-A and M-A groups required supplementary A injections. Five patients in the P-A group required additional bolus injections of the hypnotic as compared to 2 in the M-A group. The median recovery times were Iso 15 min, M-A 50 min, and P-A 25 min (P < 0.05). The incidence of shivering was Iso 3/9, M-A 5/9, and P-A 0/9 (P < 0.05); vomiting occurred with equal frequency in all groups (Iso 33%, M-A 33%, P-A 22%). The patients were somewhat more restless in group M-A. Systolic blood pressure dropped in a similar manner in all groups after induction of anaesthesia (Iso -31%, M-A -37%, P-A -36%) but recovered during surgery. The intraoperative response of cortisol (Iso + 216%, M-A +92%, P-A +43%) and catecholamines (noradrenaline Iso +56%, M-A +30%, P-A -21%) was lower in the TIVA groups, whereas prolactin increased after induction in all groups. Plasma concentrations of glucose, lactate, and fatty acids were lower in the TIVA groups than in the Iso group intraoperatively, but increased to comparable postoperative levels. CONCLUSIONS. Both TIVA regimens are acceptable alternatives to balanced anaesthesia with Iso N2O. (ABSTRACT TRUNCATED)

Adult↗
PubMed1994

[Inverse fick's principle in comparison to measurements of oxygen consumption in respiratory gases. Does intrapulmonary oxygen uptake account for differences shown by different system methods?].

Automated measurements of respiratory gas exchange recently became available for the determination of oxygen uptake (VO2) in critically ill patients. Whereas these metabolic gas monitoring systems (MBM) are assumed to measure total body VO2, the reversed Fick method in principle excludes intrapulmonary VO2. Previous clinical reports comparing VO2 measured by the reversed Fick principle (VO2Fick) with VO2 measured by MBM (VO2MBM) found that VO2MBM was significantly greater than VO2Fick. It was suggested that these differences between methods represent VO2 of pulmonary and bronchial tissue, as intrapulmonary VO2 had been estimated to account for 15% of total body VO2 in dogs with experimental pneumonia. The objective of this study was to compare VO2Fick with VO2MBM in patients with and without pneumonia and to assess the reproducibility of both methods in critically ill patients. METHOD. With institutional approval nine critically ill patients with acute pneumonia were studied under controlled mechanical ventilation. The diagnosis of pneumonia was based on respective changes of chest X-rays, body temperature > 38 degrees C, and WBC counts > 12,000/mm3. Inspiratory oxygen fractions (FIO2) ranged from 0.3 to 0.6; all patients routinely received opioids and hypnotics. Complete muscle relaxation was achieved during the periods of measurement to avoid sudden changes in VO2 due to shivering or involuntary movements. Arterial and pulmonary-arterial blood samples were drawn simultaneously after aspiration of the sevenfold catheter dead space. Measurements of haemoglobin concentration (Hb), fractional oxygen saturation (SO2), and O2 partial pressure (PO2) were performed by use of a calibrated haemoximeter and blood gas analyser, respectively; 2 x 5 thermodilution measurements of cardiac output (CO) were spread randomly over the respiratory cycle for each determination of VO2Fick. To minimise systematic errors of CO measurements, the CO computer was calibrated in an extracorporeal flow model using an electromagnetic flowmeter. Calculations of VO2Fick were based on an oxygen binding capacity of 1.39 ml/g Hb. Simultaneous measurements of VO2MBM were obtained by use of a Datex Deltatrac MBM that had been validated in vitro with a gas dilution model of respiratory gas exchange. Calibration of the MBM was performed prior to each measurement. Gas supply of the respirator was provided by an external high-precision mixing device to reduce errors in VO2 measurements that may arise from short-term oscillations in FIO2. All patients with pneumonia were studied on three consecutive days; thus, measurements from 27 days could be analysed. On each day two sets of measurements were performed at an interval of 60 min to assess the reproducibility of differences between methods. During each set of measurements duplicate blood samples were drawn twice, before and after thermodilution measurements of CO, to evaluate the short-term repeatability of VO2Fick. The beginning and the end of each set of measurements were marked in the computer record of the MBM to assess the respective repeatability of VO2MBM. Fifty control measurements were performed in ten patients undergoing major neurosurgical procedures. None of these patients exhibited signs of pulmonary infection. Except for the number of repeated measures, all VO2 measurements were obtained in the same way as in the study group. Descriptive statistical analysis was performed according to Bland and Altman; comparisons between methods were done by multivariate analysis of variance for repeated measures. RESULTS. Neither in the study group nor in the control group could a significant difference between methods be demonstrated. In patients with pneumonia the mean difference between methods (VO2Fick-VO2MBM) was 15.2 ml/min (4.2%); the double standard deviation of differences (2 SD) was 59.2 ml/min (19.2%).

Blood Gas Analysis↗
PubMed1994

Effect of anaesthesia on the cytokine responses to abdominal surgery.

Plasma concentrations of interleukins, particularly IL-6, increase after trauma and surgery. We have undertaken this study to see if the choice of anaesthetic directly or indirectly influences cytokine release. Twenty women (ASA I-II, aged 26-60 yr) undergoing elective hysterectomy for non-malignant disease were allocated randomly to receive either inhalation anaesthesia with isoflurane and nitrous oxide (group 1), or total i.v. anaesthesia with alfentanil and propofol (group 2). Blood samples for measurement of interleukins IL-1 beta and IL-6, and cortisol and prolactin concentrations were obtained at intervals from before induction to 6 h after surgery. IL-1 beta concentrations did not change during the study. IL-6 increased significantly in both groups (P < 0.05). The IL-6 increase in group 1 began earlier than in group 2. Median IL-6 concentrations were greater in group 1 (median 62 (range 0-214) pg ml-1 vs 46 (0-220) pg ml-1) (P < 0.01). Cortisol concentrations increased more rapidly and reached greater maximum concentrations in group 1. Prolactin concentrations increased immediately and to the same degree after induction in both groups, but were greater in group 2 after operation. We conclude that anaesthesia with alfentanil and propofol diminished release of IL-6 in response to abdominal surgery compared with isoflurane and that this reduction was an effect of alfentanil.

Adult↗
PubMed1994

A ventilator with an integrated gas-exchange monitoring function.

OBJECTIVE: To evaluate in the laboratory a new ventilator with a built-in monitoring function for gas exchange. DESIGN: Prospective laboratory evaluation of a new mechanical ventilator. SETTING: Gas exchange was simulated by injecting nitrogen and CO2 at a respiratory exchange ratio close to 1. SUBJECTS: Different settings of controlled-mode ventilation were simulated by the gas-injection model, which permitted an independent adjustment of variables. INTERVENTIONS: The influence of respiratory variables on oxygen consumption (VO2) and the CO2 production (VCO2) agreement with a reference method was investigated. MEASUREMENTS AND MAIN RESULTS: Independent variables, which may influence the accuracy and precision of the tested device, were adjusted systematically within the following ranges and resulted in 71 different combinations: FIO2 0.21 to 0.59; FIO2-mixed FEO2 0.02 to 0.05; mixed FECO2 0.02 to 0.05; inspiratory flow rate 25 to 120 L/min; inspiratory minute volume 4200 to 11,200 mL/min; tidal volume 420 to 1120 mL; respiratory rate 6 to 16 breaths/min; airway pressure 5 to 30 cm H2O. The resulting range for both VO2 and VCO2 was 140 to 390 mL/min. For each test situation, two reference measurements were taken by mass spectrometry and wet gas spirometry. Twelve measurements were taken by the gas-exchange measurement function of the tested ventilator. The two-fold standard deviation (SD) for repeated measurement differences was chosen to quantify the repeatability within each method. This repeatability coefficient gave 5.9 (4.7) mL/min for VO2 (VCO2) within the gas-exchange measurement function, compared with 3.6 (3.1) mL/min within the reference method measurements. The mean intermethod difference (test monitor--reference method) for VCO2 over all test situations was 4.1 +/- 10.7 (2 SD)%. The respective mean VO2 difference was 7.8 +/- 12.2 (2 SD)%. Eliminating test situations with inspiratory flow rates < 50 L/min (remaining n = 46) reduced the mean VO2 difference and variability by one third to 5.4 +/- 8.0 (2 SD)%. CONCLUSIONS: Assuming that limits of agreement for intermethod differences of +/- 20% are clinically acceptable, the VCO2 measurement indicates an acceptable accuracy and precision under controlled ventilation. The respective agreement for the VO2 measurement is lower, but still within the acceptable range. The systematic difference of the VO2 and the VCO2 is mainly influenced by a +8% bias in the inspiratory minute volume measurement, which seems especially susceptible to ventilator settings with inspiratory flow rates of < 50 L/min. An improvement of the minute volume detection would be desirable.

Analysis of Variance↗
PubMed1994

A rational basis for the measurement of free phenytoin concentration in critically ill trauma patients.

Phenytoin binding to serum proteins and factors influencing protein binding were investigated in 38 critically ill trauma patients. In 24% of these patients, the free fraction of phenytoin was < or = 10%, whereas in 76%, the free phenytoin fraction was increased > 10%--up to 24%. Nonantiepileptic comedication, sex, or age had no influence on phenytoin binding in any of the 38 patients. Elevated free phenytoin fraction was found in those with hypoalbuminemia and hepatic and renal impairments. In these patients, the free phenytoin fraction should be measured routinely.

Adolescent↗