Influence of underlying disease on the outcome of critically ill patients with acute renal failure

BACKGROUND AND OBJECTIVE

The development of acute renal failure (ARF) in critically ill patients is associated with an increase in hospital mortality. Recently, it was shown that starting renal replacement therapy early and using high-filtrate flow rates can improve the outcome, but this could not be confirmed in later investigations. Studying selected patient subgroups could provide a useful basis for patient selection in future trials evaluating the outcome of renal replacement therapies. We, therefore, investigated the impact of the underlying disease on the outcome of patients with ARF.

METHODS

We retrospectively analysed 306 patients with ARF who were treated with renal replacement therapy. Patients were classified according to six initial diagnosis groups: haemorrhagic shock, post-cardiac surgery, post-liver transplantation, trauma, severe sepsis and miscellaneous. Univariate and multivariate multiple logistic regression analysis was used to determine which factors influenced the outcome.

RESULTS

Underlying disease proved to be the only independent risk factor for mortality that was present at intensive care unit (ICU) admission (P = 0.047). Patients with severe sepsis had a significantly higher mortality rate (68%) than ARF patients as a whole (51%) (P = 0.02). Length of stay in the ICU, the use of catecholamines, the delay before ARF onset, and the correlation between APACHE II score and ICU length of stay proved to be additional independent predictors of outcome.

CONCLUSIONS

Patient selection and subgroup definition according to the underlying disease could augment the usefulness of future trials evaluating the outcome of ARF.

Nichtinvasive Bestimmung des Herzzeitvolumens bei beatmeten Patienten

OBJECTIVE

This study was performed to evaluate a new simplified rebreathing method to determine cardiac output (CO) in mechanically ventilated patients.

METHODS

Using a rebreathing system (AMIS 2001, Innovision, Dänemark), effective pulmonary blood flow (PBF) and oxygen consumption (V(radical)O2) were determined non-invasively in 40 patients. After estimation of arterial (CaO2) and capillary oxygen (CcO2) content from the results of an arterial blood gas analysis, intrapulmonary shunt was calculated as Q(s)/Q(t) = [CcO2CaO2] * PBF/V(radical)O(2). Cardiac output was determined by the rebreathing method as CO(rb) = PBF/(1- Q(s)/Q(t)). The cardiac output measured by thermodilution (CO(thd)) was used to determine reference values, which were calculated as mean value of CO(thd) and CO(rb). Intrapulmonary shunt calculated from arterial and mixed-venous blood gas analyses served as reference for the non-invasive determination. In addition, reproducibility of the new method was determined in 15 patients.

RESULTS

CO(thd) varied from 3.7-9.5 l/min (6.1 +/- 1.6 l/min; mean +/-SD). Bias and precision of CO(rb) determination accounted for 0.18 l/min (2.9%) and +/- 0.61 l/min (10%), respectively. Precision of intrapulmonary shunt measurement accounted for +/-2.1%. Reproducibility of the CO measurements accounted for 0.24 l/min or 3.9%.

CONCLUSION

The rebreathing system evaluated in the present study allows the noninvasive determination of cardiac output with rather high accuracy and good reproducibility. However, technical improvement and further investigation in patients with extremely high cardiac output and shunt values will be needed before its routine clinical use.

Non-invasive determination of effective pulmonary blood flow: evaluation of a simplified rebreathing method

PRIMARY OBJECTIVE

To evaluate a new technical approach to measuring effective pulmonary blood flow (PBF) in mechanically ventilated patients.

RESEARCH DESIGN

Prospective clinical study; evaluation of accuracy and reproducibility.

METHODS

Effective pulmonary blood flow was determined non-invasively in 32 mechanically ventilated patients by using a new rebreathing system (PBF(rb)). Cardiac output corrected for intrapulmonary shunt was taken as reference value (PBF(thd)). Bias, precision and reproducibility of the rebreathing method were calculated from duplicate measurements in each patient.

MAIN RESULTS

The mean difference between PBF(rb) and PBF(thd) was - 0.67 +/- 0.83 l min(-1). The mean difference between duplicate measurements with the rebreathing system was 0.16 +/- 0.36 l min(-1). However, the accuracy of the rebreathing system tended to decrease in patients with PBF levels greater than 6 l min(-1).

CONCLUSIONS

The new device appears to be reliable for determination of PBF values below 6 l min(-1). With this limitation, the present method may be used as a trend-indicator of PBF in mechanically ventilated patients.

Patient data management systems in critical care

Electronic patient data management systems (PDMS) were clinically used for the first time in the 1970s. Their purpose was to automatically document vital parameters sampled by monitors and to replace handwritten medical files. Because of the continuous development of computer technology, however, demands on PDMS have increased immensely. PDMS are currently expected to assist clinicians at every level of intensive care, i.e., at the strategic level of physicians' orders and prescriptions, at the operational level, and at the administrative level. In 1994, a PDMS (CareVue; Agilent Technologies) was installed and further developed in the anesthesiologic intensive care unit of the university hospital in Tübingen. The goals of this article were to describe the current demands on PDMS, to communicate our experiences in implementing a PDMS, to list the costs of purchasing and maintaining the system, and to report on the acceptance among physicians and nursing personnel. This article may assist new users in planning for, purchasing, and implementing a PDMS.

ICP measurement control: laboratory test of 7 types of intracranial pressure transducers

Intracranial pressure (ICP) monitoring has become an important parameter in the assessment of comatose patients, with raised intracranial pressure. The transducers in use have to fulfill the criteria of measurement accuracy, practicability and cost-effectiveness. However, these requirements are not always met in clinical practice. The need for ongoing quality control through independent laboratories remains. We have developed a laboratory set-up for the evaluation of intracranial pressure probes. Seven different types of currently used transducers have been tested for measurement accuracy. Under in vitro conditions 3 parameters were assessed: measurement accuracy, a 24 h drift and 10 day drifts. Tests for measurement accuracy were performed at increasing pressure levels of up to 80 mmHg. They were repeated 10 times per probe. This test allowed the simultaneous assessment of 5 different ICP probes. Drift was evaluated for 24 h and 10 days, at 6 pressure levels between 0 and 50 mmHg. Seven different types of ICP probes were tested (HanniSet, Camino, Codman, Spiegelberg, Medex, Epidyn and Gaeltec). Measurement accuracy was best with HanniSet probes. The maximum errors with this transducer were 3 mmHg. Camino and Codman showed similar results. Spiegelberg had slightly larger deviations. With Epidyn and Gaeltec the highest error were noted, up to 10 mmHg in the high pressure range. The 24 h drift was lowest with HanniSet (0.2 mmHg) and Camino (0.8 mmHg). The largest drifts were seen with Medex, Spiegelberg and Gaeltec (1.8 mmHg). Ten day drift was lowest with HanniSet (0.1 mmHg/day) and Codman (0.2 mmHg/day). The highest long-term drifts were found with Epidyn and Gaeltec (1.5 mmHg/day). Drift did not exhibit a linear pattern. After an initial rise in drift during the first 24-72 h, it decreased slowly during the next 7 days. Most ICP probes revealed measurement inaccuracy and drift. These results emphasize the necessity for ongoing evaluations of ICP probes. Therefore, tests for quality assurance are essential to establish a consistent standard of proficiency of ICP transducers.

Implementation of an interactive computer-assisted infection monitoring program at the bedside

A new computer-assisted infection monitoring (CAI) software program has been developed for use in an intensive-care unit (ICU). By means of an interactive dialogue with physicians at the bedside, infection diagnoses and therapeutic decisions were recorded prospectively during a 3-month test period. By linking epidemiological data with information about therapeutic decisions, CAI could assess the quality of the therapeutic decisions. Antibiotics chosen empirically before the availability of any culture results, matched the antibiotic susceptibility patterns of the subsequently identified pathogens in 74% of the cases. Therapy chosen in collaboration with the computer after the pathogen was known, but before sensitivity results were available, corresponded with the eventual antibiograms of the microorganisms in 90% of the cases. Data analysis by CAI allowed us to assess critically the diagnostic and therapeutic habits in our ICU. Using the query-by-example method, CAI automatically calculated device-associated infection rates.

New aspects of pulmonary mechanics: "slowly" distensible compartments of the respiratory system, identified by a PEEP step maneuver

OBJECTIVE

The aims of the present study were 1) to evaluate a method for identification of "slowly" distensible compartments of the respiratory system (rs), which are characterized by long mechanical time constants (RC) and 2) to identify "slowly" distensible rs-compartments in mechanically ventilated patients.

DESIGN

Prospective study on a physical lung model.

SETTING

Intensive Care Unit, University Hospital, Tübingen.

PATIENTS AND PARTICIPANTS

19 patients with severe lung injury (acute respiratory distress syndrome, ARDS) and on 10 patients with mild lung injury.

MEASUREMENTS AND RESULTS

Positive end-expiratory pressure (PEEP)-increasing and -decreasing steps of about 5 cmH2O were applied and the breath-by-breath differences of inspiratory and expiratory volumes (delta V) were measured. The sequence of delta Vs were analyzed in terms of volume change in the "fast" compartment (Vfast), the "slow" compartment (Vslow), total change in lung volume (delta VL) and mechanical time constant of the slow compartment (RCslow). Thirty-eight measurements in a lung model revealed a good correlation between the preset Vslow/delta VL and Vslow/delta VL measured: r2 = 0.91. The Vslow/delta VL measured amounted to 0.94 +/- 0.15 of Vslow/delta VL in the lung model. RCslow measured was 0.92 +/- 0.43 of the RCslow reference. Starting from a PEEP level of 11 cmH2O PEEP-increasing and PEEP-decreasing steps were applied to the mechanically ventilated patients. Three out of ten patients with mild lung injury (30%) and 7/19 patients with ARDS (36.8%) revealed "slowly" distensible rs-compartments in a PEEP-increasing step, whereas 15/19 ARDS patients and 1/10 patients with mild lung injury showed "slowly" distensible rs-compartments in a PEEP-decreasing step (78.9% vs 10%, P < 0.002, chi-square test).

CONCLUSIONS

The gas distribution properties of the respiratory system can be easily studied by a PEEP-step maneuver. The relative contribution of the "slow" units to the total increase of lung volume following a PEEP step could be adequately assessed. "Slowly" distensible rs-compartments could be detected in patients with severe and mild lung injury, however significantly more ARDS patients revealed "slow" rs-compartments in PEEP-decreasing steps. The influence of "slowly" distensible rs-compartments on pulmonary gas exchange is unknown and has yet to be studied.

[First aid and prognosis following drowning accidents. Results of a retrospective study of 115 cases]

OBJECTIVE AND STUDY DESIGN

In 115 cases of submersion the initial findings of the rescue team, the patients status in the emergency room and the course of clinical treatment were analyzed retrospectively.

RESULTS

Submersion accidents happened preferably in February, March and in the summertime from May to August. Most of the accidents took place in public waters or public baths (85.2%). Children below 10 years of age were involved in 34.8% of the submersion accidents. 57 patients were near drowned and 58 patients were drowned. The prognosis of patients with detectable heartbeat at the site of the accident depends on the primary pulmonary lesion. If respiratory insufficiency is recognized early and treated aggressively by intubation and mechanical ventilation with PEEP, these patients have an excellent prognosis. Only one patient with detectable heartbeat died, typically, after delayed treatment of respiratory failure. 55 patients recovered completely; one patient was suffering from a lesion of the n. medianus. Contrariwise, the prognosis of patients without detectable heartbeat is mainly determined by the consequences of hypoxaemia and is, overall, poor. Though resuscitation succeeds in 50% of submersion victims, only one out of four successfully resuscitated patients survived with little or no neurologic damage. Severe hypothermia may improve the prognosis of submersion victims.

CONCLUSION

Thus, there are no useful parameters that would accurately predict the individual course of a submersion victim.

A simple method to estimate functional residual capacity in mechanically ventilated patients

OBJECTIVE

The aim of the present study was to evaluate a simplified method for FRC measurement.

DESIGN

Accuracy and precision of the method were assessed in a physical lung model; reproducibility was tested in 10 mechanically ventilated patients. In each patient FRC was measured at three PEEP levels.

SETTING

Post-operative intensive care unit in a university hospital.

MEASUREMENTS AND RESULTS

Gas flow, CO2 concentration, and O2 concentration were measured during in- and expiration by pneumotachography, a mainstream capnometer and a sidestream O2-analyser. For FRC-measurement inspiratory O2 concentration was changed by 30%. FRC was determined as mean value of a N2 washout and N2 washin procedure. Evaluation of this method in a lung model shows a good correlation between FRC set in the lung model and FRC measured (FRC measured = 1.028*FRG model + 22.92 ml; r2 = 0.957; n = 30). The mean difference was 4.4% of FRC-reference (range -8.4% to +21.7%). Duplicate determinations in 10 mechanically ventilated patients differed by an average of -2.7% (range -30.1% to +27.3%).

CONCLUSION

Our results suggest that the proposed method can be used in daily clinical work.

Pulmonary venodilation by isoflurane improves gas exchange during Escherichia coli bacteremia

OBJECTIVE

To determine how isoflurance affects the longitudinal distribution of pulmonary vascular resistance and pulmonary gas exchange during Escherichia coli bacteremia.

DESIGN

Prospective, controlled study with open-label assignment of animals to two groups.

SETTING

Laboratory.

SUBJECTS

Goehingen minipigs.

INTERVENTIONS

Induction of acute respiratory failure by a 4-hr infusion of live E. coli bacteria in 12 animals; six animals anesthetized with methohexital/piritramide; six animals anesthetized with isoflurane. The control group consisted of four animals that received the same surgical procedure, but no E. coli infusion. Two animals were anesthetized with methohexital/piritramide and two with isoflurane, respectively.

MEASUREMENTS AND MAIN RESULTS

Cardiac output and pressures were measured by means of an arterial catheter, Swan-Ganz catheter, and a left atrial catheter. Effective pulmonary capillary pressure was evaluated graphically from a pulmonary artery occlusion pressure decay. Arterial-alveolar PO2 ratio was calculated to evaluate pulmonary function. Measurements were performed before and after 1, 2, and 3.5 hrs of E. coli infusion. Statistical significance was tested with analysis of variance (ANOVA). E. coli infusion caused hypodynamic shock, an increase in pre- and postcapillary pulmonary vascular resistance and respiratory failure. Postcapillary pressure gradient and effective pulmonary capillary pressure were lower in the isoflurane-group. Methohexital-anesthetized animals developed pulmonary dysfunction after 1 hr of bacteremia, whereas isoflurane-anesthetized animals developed pulmonary dysfunction after 3.5 hrs of E. coli infusion (significantly different, ANOVA, p < .05). There were no significant changes in the sham group.

CONCLUSIONS

Isoflurane is a pulmonary venodilator. During lethal E. coli infusion, it ameliorates the increase in pulmonary capillary pressure and preserves pulmonary function until vascular permeability increases.

[Longitudinal distribution of pulmonary vascular resistance in patients with acute respiratory insufficiency]

Effective pulmonary capillary pressure (Pc) is a major factor determining transvascular fluid filtration in the lung. It may easily be estimated from the pressure decay after rapid pulmonary artery occlusion. If Pc is known, the longitudinal distribution of pulmonary vascular resistance (PVR) can be evaluated. The present study was performed to address the following questions: (a) whether the severity of acute lung injury influences Pc and the longitudinal distribution of PVR; and (b) whether pulmonary artery occlusion (PAOP) or wedge pressure represents effective Pc during acute respiratory failure. PATIENTS AND METHODS. The investigation was performed in 45 mechanically ventilated patients. According to Murray's criteria 13 patients showed no lung injury, 19 had mild to moderate lung injury, and 13 had severe lung injury (adult respiratory distress syndrome, ARDS). As described by Holloway, effective Pc was evaluated from the pressure decay after rapid occlusion of the pulmonary artery (Figs. 1 and 2). The precapillary pressure gradient was determined as the difference between mean pulmonary artery pressure and Pc, the postcapillary pressure gradient as the difference between Pc and PAOP. Three measurements were performed and Pc determined as their mean value. The Kruskal-Wallis test and Mann-Whitney U test were performed to check statistically significant differences between groups. A Bonferroni correction was performed for multiple testing; P < 0.05 was accepted. RESULTS. Effective Pc was significantly different between patients with severe lung injury (20 +/- 3 mm Hg) and patients with mild to moderate lung injury (16 +/- 3 mm Hg), and between the latter group and patients without lung injury (12 +/- 3 mm Hg). The postcapillary pressure gradient and the relative amount of pulmonary venous vascular resistance, as well, were significantly influenced by the severity of the lung injury. In patients with ARDS the postcapillary pressure gradient was 4 +/- 1 mm Hg, whereas in patients with mild to moderate and without lung injury the postcapillary pressure gradients were 3 +/- 1 mm Hg and 2 +/- 1 mm Hg, respectively. Two ARDS patients had a postcapillary pressure gradient of 7 mm Hg (Pc 22 mm Hg and 19 mm Hg, PAOP 15 mm Hg and 12 mm Hg). One patient with severe lung injury had a postcapillary pressure gradient of 9 mm Hg (Pc 22 mm Hg, PAOP 13 mm Hg). In patients with severe lung injury 28 +/- 7% of the PVR was located in the postcapillary vascular system, whereas in patients with mild to moderate and without lung injury 22 +/- 7% and 16 +/- 6% of PVR was located in the pulmonary venous system. CONCLUSIONS. The longitudinal distribution of PVR is influenced by the severity of lung injury. PAOP, therefore, may not represent changes in Pc in patients with acute respiratory failure. The routine use of Pc measurement, however, can not be recommended until it has proven more useful than determination of PAOP when managing critically ill patients.

[Capnometry in pediatric anesthesia. The effect of the measurement site and respiratory rate]

OBJECTIVE

To evaluate the influences of site of measurement, respiratory rate, and tidal volume on end-tidal PCO2 measurement in children ventilated with a non-rebreathing system.

SETTING

Paediatric surgical patients of a university hospital.

PATIENTS

Thirty-one children scheduled for major abdominal or urogenital surgery; weight varying between 2.2 and 9.8 kg.

INTERVENTIONS AND METHODS

During a relative steady-state situation, end-tidal carbon dioxide partial pressure (PetCO2) was measured at the proximal and distal ends of the endotracheal tube by a sidestream analyser (Datex, Normocap) and between the proximal end of the tube and the Y-piece of the ventilator by a mainstream analyser (Hewlett Packard, HP14265A). PetCO2 was corrected for water vapor and calculated as partial pressure at a barometric pressure of 760 mmHg. At the same time, capillary blood was taken for blood gas analysis. The capillary-end-tidal PCO2 gradient [dPCO2(cap-et)] was computed to compare the three capnometric methods. Statistical analysis was performed with the Friedmann test. Correlations were calculated by means of the least-square fitting method and significance of the correlation was checked with the F-test.

RESULTS

dPCO2 (cap-et) did not differ significantly in children with more than 6 kg body weight. In patients less than 6 kg, however, the three capnometric methods revealed significantly different dPCO2 (cap-et) values (P less than 0.01): dPCO2 (cap-et) was 3.0 +/- 4.7 mmHg at the distal end of the endotracheal tube, 5.8 +/- 4.6 mmHg at the proximal end, and 8.7 +/- 4.6 mmHg between the proximal sidestream connector and the Y-piece of the ventilator. There was no correlation between tidal volume and dPCO2 (cap-et) (Fig. 1), however, a significant relation was found between respiratory rate and dPCO2 (cap-et) (Fig. 2) and between respiratory rate and the PCO2 difference between the distal and proximal ends of the endotracheal tube (Fig. 3).

CONCLUSIONS

Even in a non-rebreathing system, capnometry is influenced by the site of measurement. In small children with body weight below 6 kg, analysis of an endotracheal sample may provide the best PetCO2 values. In our opinion, dPCO2 (cap-et) in the present investigation was not caused by rebreathing or by pendelluft (a significant correlation between dPCO2 (cap-et) and tidal volume would then have been expected), but was mainly due to ventilation-perfusion mismatch. This may result from high respiratory rates causing inadequate ventilation of lung regions with long time-constants.

[Amrinone for cardiovascular therapy in hypodynamic septic patients?]

Pulmonary hypertension, systemic vasodilation and the supply dependency of oxygen uptake are the major problems associated with sepsis. Thus, the goal of haemodynamic therapy in septic patients is an increase in cardiac output large enough to permit adequate tissue oxygenation. The purpose of this study was to establish whether the additional use of the phosphodiesterase inhibitor amrinone is useful in hypodynamic septic patients with inadequate tissue perfusion. Nine patients who had developed the clinical signs of sepsis (temperature greater than 38.5 degrees C, leukocytosis greater than 15,000/mm3, thrombopenia less than 100,000/mm3 or a drop in platelet count greater than 30%, cardiovascular shock) were given amrinone 30 micrograms.kg-1.min-1 for one hour. All patients showed mixed venous oxygen saturations below 70% and oxygen extraction rates above 30%, despite maximum catecholamine therapy. Haemodynamic parameters were measured with the help of a pulmonary artery catheter. Statistical significance was checked using the Wilcoxon signed-ranks test. During amrinone application cardiac index increased significantly from 4.6.1.81.min-1.m-2 to 5.6 +/- 1.81.min-1.m-2 (p less than 0.01), while central venous pressure was kept constant by volume supply. Mean pulmonary artery pressure remained nearly unchanged, whereas mean arterial pressure dropped significantly from 91 +/- 13 mmHg to 75 +/- 8 mmHg (p less than 0.01). The oxygen supply rose during administration of amrinone by an average of 17%, which led to a rise in oxygen uptake. Independence of oxygen uptake from oxygen supply, however, could not be attained. In septic patients, amrinone increases cardiac output via pulmonary vasodilation. However, pronounced systemic vasodilation lowers arterial blood pressure, enhancing the risk of myocardial ischaemia.

[Risk indicators in coronary surgery]

We examined the perioperative course of 1013 patients who had undergone coronary surgery between 1984 and 1987, to identify preoperative examination findings which are suitable as risk indicators in coronary surgery. The features we paid attention to were: anamnestic data, parameters of coronary disease, haemodynamic parameters and accompanying illnesses. We considered a perioperative course as complicated when systolic blood pressure dropped to 80 mmHg or less for longer than 15 min, when reconnection to the heart-lung-machine was necessary, when an intra-aortal balloon counterpulsation was required, when the patient had to have mechanical ventilation for longer than 24 h, when resuscitation took place, or when the patient died in the hospital. The Chi-square test was used for statistical analysis. Very good risk indicators (p less than 0.001) were: age greater than 60 y, resuscitation history, more than two bypass grafts, SvO2 70%, ejection fraction less than 50% and cardiac index less than 2.5 l/min*m2. Good risk indicators (p less than 0.001) were: functional capacity less than 50 watts, more than one previous myocardial infarction and LVEDP greater than 20 mmHg. LCA-stenosis, arterial hypertension with diastolic blood pressure values above 100 mmHg, and obstructive airway disease were identified as suitable risk indicators (p less than 0.05). The following findings were combined with significantly increased mortality: female sex, age over 60 years, two or more previous myocardial infarctions, history of resuscitation, mixed venous oxygen saturation below 70% and the need for three or more bypass grafts for complete revascularisation.

Pulmonary artery occlusion-left atrial pressure gradient: an important factor in determining pulmonary venous vascular resistance in acute pulmonary failure

OBJECTIVE

To determine whether pulmonary artery occlusion pressure (PAOP) accurately reflects left atrial pressure (LAP) in acute pulmonary failure.

DESIGN

Sham-controlled laboratory investigation on Goettingen minipigs.

INTERVENTIONS

Induction of acute respiratory failure by a 4-hr infusion of live Escherichia coli bacteria in 11 animals; two animals served as the control group. Anesthesia was obtained with methohexital/piritramide and pancuronium bromide.

MEASUREMENTS AND MAIN RESULTS

Cardiac output and pressures were measured by means of femoral artery, pulmonary artery, and left atrial catheters. Arterial-alveolar Po2 ratio was calculated to evaluate pulmonary function. Measurements were obtained before and after 1 and 2 hr of the E. coli infusion. Statistical significance was tested with analysis of variance. E. coli infusion caused the hypodynamic shock and respiratory failure. The PAOP-LAP gradient was -0.3 +/- 1.6 mm Hg before bacteremia and increased significantly (p less than .001) to 2.9 +/- 1.8 and 3.4 +/- 2.0 mm Hg after 1 and 2 hr of bacteremia, respectively. No significant changes occurred in the sham group.

CONCLUSIONS

A PAOP-LAP gradient may develop during acute respiratory failure. Therefore, pulmonary venous vascular resistance may be underestimated if its determination is based on PAOP. An increase in bronchial to pulmonary blood flow and pulmonary venoconstriction are discussed as hypothetical causes of a PAOP-LAP gradient during acute respiratory failure.

Pulmonary capillary pressure and gas exchange after E. coli bacteremia in pigs

In 9 Goettingen minipigs we studied the effect of E. coli bacteremia on effective pulmonary capillary pressure and the longitudinal distribution of pulmonary vascular resistance. Precapillary pressure gradient (dPa) was calculated as the difference between mean pulmonary artery pressure (MPP) and effective pulmonary capillary pressure (Pc) (dPa = MPP-Pc), postcapillary pressure gradient (dPv) as the difference between Pc and left atrial pressure (dPv = Pc-LAP). The disturbance of pulmonary gas exchange was quantified by the AaDO2 quotient 1-PaO2/PAO2. Live E. coli infusion resulted in hypodynamic circulatory failure. Cardiac index fell from 3.7 +/- 0.81 . min-1.m-2 to 2.2 +/- 0.71 .min-1.m-2 after bacteremia lasting for 3.5 h. Simultaneously venous pulmonary vascular resistance rose from 25% of total pulmonary vascular resistance before to 32% after 3.5 h bacteremia, thus raising Pc from 11 mmHg to 16 mmHg. The degree of respiratory insufficiency was correlated with changes of MPP, dPa and dPv: 1-PaO2/PAO2 = 0.2 + 0.035.dPv (r = 0.829). Our results show, that the longitudinal distribution of pulmonary vascular resistance changes during septicemia, thus raising Pc. This may be an important factor in the genesis of septic pulmonary failure.

[Lung inflation or mechanical ventilation in extracorporeal circulation?]

Extracorporeal circulation (ECC), with its shock-like pulmonary perfusion, leads to pathomorphologic and functional pulmonary changes, the postperfusion syndrome. This study investigated the effects of different types of ventilation during ECC on postoperative pulmonary function and the resulting pulmonary blood gas changes. METHOD. Thirty patients scheduled for aortocoronary bypass surgery were studied. Patients with pre-operative left ventricular end-diastolic pressures exceeding 15 mmHg or signs of right ventricular failure, pulmonary hypertension, or pre-existing pulmonary disease were excluded. The patients were randomly assigned to one of the following three groups: Group 1 (n = 10): static pulmonary inflation during ECC, PEEP 5-10 cm H2O, F1O2 1.0; Group 2 (n = 10): low-frequency ventilation during ECC, rate 10/min, PEEP 5 cm 5H2O, F1O2 1.0; Group 3 (n = 10): medium-frequency ventilation during ECC, rate 120/min, PEEP 5 cm 5H2O, F1O2 1.0. The measurements were made under relative steady-state conditions before the start of surgery and postoperatively after an equilibrium phase of at least 15 min. During ECC using a bubble oxygenator (Bentley BOS 10 S) in moderate hypothermia, blood was aspirated from the pulmonary artery during inflation of the wedge balloon and blood gases were analyzed. Postoperative changes in pulmonary function were evaluated by venous admixture (QVA/Qt); changes in pulmonary vascular resistance after ECC were determined using the pulmonary pressure-flow relationship. RESULTS. In group 1, QVA/Qt rose significantly from 9.6 +/- 2.9% preoperatively to 13.6 +/- 3.5% postoperatively (P less than 0.05, t-test for paired samples). In groups 2 and 3, postoperative QVA/Qt was significantly lower than preoperative QVA/Qt (P less than 0.05; group 2: preoperative 11.9 +/- 3.5%, postoperative 8.1 +/- 2.6%; group 3: preoperative 11.9 +/- 3.0%, postoperative 7.8 +/- 3.2%; Fig. 1). The postoperative pulmonary pressure-flow relationship changed similarly in all three groups (Fig. 2). During ECC, blood aspirated from the pulmonary artery during inflation of the wedge balloon was fully oxygenated with a hematocrit approximating that of arterial blood. In ventilated patients, pO2 during ECC was higher in pulmonary arterial blood than in arterial blood. Pulmonary ventilation during ECC did not lead to pulmonary arterial alkalosis. CONCLUSIONS. Pulmonary ventilation during ECC can prevent a post-operative increase in venous admixture. ECC-related pulmonary vascular changes were not affected by ventilation. Middle-frequency ventilation offers no advantage over low-frequency ventilation during ECC, except that the operating field is more quiet.

Acute blood pressure increase during the perioperative period

Hypertensive reactions occur frequently in the perioperative setting. Perioperative blood pressure elevation is generally amenable to treatment in previously normotensive patients. Alterations in cerebral autoregulation and myocardial performance in chronic hypertension limit the compensatory range available to cope with perioperative blood pressure changes. In cardiovascular or cerebrally compromised patients, the pathophysiology of underlying disease must therefore be taken into account. In the cerebrally compromised patient with space-occupying lesions and even merely locally impaired cerebral autoregulation, any blood pressure increase may reduce cerebral perfusion pressure and cause further cerebral impairment. Furthermore, vasodilation of cerebral vessels must be avoided to prevent further increase in intracranial pressure with reduction of cerebral perfusion. In chronically hypertensive patients, sufficient preoperative antihypertensive therapy is essential to avoid acute perioperative blood pressure elevation. Before antihypertensive pharmacologic therapy is begun, it is essential to rule out all correctable secondary causes of hypertension, particularly impairment of ventilation and oxygen supply. When pharmacologic antihypertensive therapy is necessary, vasodilators (e.g., calcium entry blockers) may be administered to chronically hypertensive patients. If elevated intracranial pressure is the underlying cause of hypertension, cerebral vasodilation must be avoided and only centrally acting antihypertensive agents such as urapidil should be used for management.

[Virus-specific IgM proof with routine serologic methods (author's transl)]

By the use of a specific immunosorption to insoluble adsorbentia (controlled-pore glass, polystyrene particles) the separation of IgM and IgG is performed in serum specimens, which originate from patients presenting several virus infections (mumps, measles, cytomegalovirus, herpes simplex), for the virus-specific IgM proof with routine serologic methods (CFT, HIT, NT). The results are in a good agreement to them seen in the demonstration of significant titer rises to assure the diagnosis of acute mumps and measles infections by HIT rapidly. While the new technique is also successfully applied for the determination of neutralizing IgM and IgA antibodies to HSV, no sufficient results are available to detect CMV specific IgM antibodies by CFT compared to other methods (IFT, ELISA).