Prognostic utility of a multibiomarker panel in patients with suspected myocardial infarction

Introduction

Rapid and accurate evaluation of patients presenting with suspected myocardial infarction (MI) to the emergency department (ED) is crucial due to strongly varying outcomes in these patients. Despite the routine use of circulating biomarkers, among which high-sensitivity cardiac troponin currently dictates diagnostic protocols in chest pain patients, it still remains unclear which biomarkers are of highest utility for prognostic purposes in this patient collective.

Purpose

We sought to investigate the prognostic utility of a multibiomarker panel with 29 different biomarkers in a contemporary cohort of patients with suspected MI by applying a dual analytical approach.

Methods

The multibiomarker panel was measured in stored blood samples that were collected directly at admission from 748 prospectively enrolled patients who presented with symptoms suggestive of MI to the ED of a German tertiary center between 2013 and 2017. The final diagnosis of all patients was adjudicated according to the 4th Universal Definition of MI. The investigated endpoint comprised incident major cardiovascular events (MACE) within 1 year after admission. MACE was defined as the composite of cardiovascular death, non-fatal MI (excluding index events), revascularization and cardiac rehospitalization. Log-transformed biomarkers were entered individually into an age-and sex-adjusted Cox regression model to explore the hazard ratio (HR) per one standard deviation increase (SD) for 1-year MACE in the overall cohort. The selection of optimal multimarker models, adjusted for age and sex, was performed using 1) stepwise backward selection via Akaike information criterion as the stopping rule, and 2) Least Absolute Shrinkage and Selection Operator (LASSO) with 5-fold cross-validation.

Results

Out of 748 patients with available multibiomarker panel, 138 (18.4%) were diagnosed with MI. Median age at admission was 64 (interquartile range [IQR] 50–75) years in the overall cohort, 63.1% were male. At 1 year of follow-up, 160 cases of incident MACE were documented. 16 of the investigated 29 biomarkers were significantly associated with 1-year MACE, amongst which NT-proBNP was the strongest predictor (HR per SD 1.74, 95% confidence interval [CI] 1.44–2.09, p<0.0001; Table 1). Using stepwise backward selection, three biomarkers including NT-proBNP, Apo A-I and Apo C-III remained in the final multivariable model (Figure 1). The LASSO approach confirmed NT-proBNP (HR per SD 1.24) and Apo A-I (HR per SD 0.98) as strong and independent predictors of 1-year MACE while Apo C-III was replaced with KIM-1 (HR per SD 1.06).

Conclusions

Among 29 biomarkers, numerous provide prognostic utility while NT-proBNP and Apo A-I emerged as the strongest independent predictors of 1-year MACE. Their routine assessment and integration into risk prediction models may improve personalized risk stratification in patients with symptoms suggestive of MI.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The BACC study was supported by the German Center for Cardiovascular Research, an unrestricted grant by Abbott Diagnostics, and Prevencio, which also partly covered the biomarker measurements.

C-Reactive Protein to Albumin Ratio offers superior risk prediction in patients undergoing mitral valve edge-to-edge repair: a comparison to established surgical risk scores

Background

The population of patients with relevant mitral regurgitation (MR) who stand to gain optimal benefit from mitral valve transcatheter edge-to-edge repair (TEER) remains to be determined. Prior to TEER, a heart-team approach with interdisciplinary decision-making is mandatory integrating both the patient profile and relevant co-morbidities. In addition, the application of established surgical risk scores is recommended by current guidelines. Whether alternative risk prediction is more suitable for this fragile patient cohort burdened with various co-morbidities has not been examined in detail. A simplified approach may be achieved by using the C-Reactive Protein to Albumin Ratio (CAR), but its value in TEER is unclear.

Methods

This single-center, retrospective study thought to determine long-term prognostic accuracy of different risk scores in patients with relevant MR undergoing TEER. For this analysis, 316 patients with a median follow-up time of 5.81 years were included. The primary outcome measure was defined as all-cause mortality. ROC analysis was conducted for the identification of the optimal CAR threshold, subsequently dichotomizing patients into two groups (CAR ≤0.4 and CAR >0.4) estimating their long-term event rate using the Kaplan-Meier method. In addition, we evaluated the prognostic value of CAR compared to two conventional surgical risk scores (logistic EuroSCORE and Society of Thoracic Surgeons [STS] risk score) using C-Index analysis.

Results

Among 316 high-risk patients undergoing TEER (mean age 75.6±8.2 years, 61.7% male, median logistic EuroSCORE 19.9% [11.7; 31.6], median STS Score 3.8% [2.2; 5.7]), 176 (55.7%) patients had a CAR value ≤0.4. Patients with an elevated CAR (>0.4) predominantly suffered from a higher burden of co-morbidities, such as peripheral artery disease (p=0.001), chronic obstructive pulmonary disease (p=0.044), and chronic kidney disease (p=0.015). Consequently, these patients had significantly higher logistic EuroSCORE and STS Score than patients with CAR ≤0.4 (logistic EuroSCORE p=0.002; STS Score p<0.001). Stratification according to the CAR threshold of 0.4 led to significant differences in the Cumulative Incidence curves (p<0.001). In addition, log-rank test revealed a superior risk stratification of the simplified CAR approach compared to established surgical risk scores (Figure 1). This effect consequently reflects in a higher adjusted C-Index for CAR (0.608) compared to logistic EuroSCORE (0.502; p<0.001) and STS Score (0.498; p<0.001).

Conclusions

Our data provide first evidence that alternative risk prediction using CAR allows for a feasible and easy-to-use risk prediction in a real-word TEER cohort presenting with advanced age, a high proportion of frailty and numerous co-morbidities. Alternative risk prediction in TEER patients should be investigated in more detail as the established surgical risk scores seem to demonstrate limited applicability in patients scheduled for TEER.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): University Medical Center Hamburg-Eppendorf, Hamburg, Germany

Outcomes of patients with severe mitral regurgitation treated with transcatheter mitral valve implantation or medical therapy

Funding Acknowledgements

Type of funding sources: None.

Background

Patients with severe mitral regurgitation (MR) unsuitable for standard therapy (i.e., open-heart surgery and transcatheter edge-to-edge repair [TEER]), often remain on medical therapy (MT) alone. Transcatheter mitral valve implantation (TMVI) may represent an alternative treatment option for these patients.

Purpose

We aimed to investigate differences in anatomical baseline characteristics and echocardiographic outcomes between MR patients unsuitable for standard therapy, that were either treated with TMVI or remained on MT.

Methods

Between 05/2016-02/2021, 121 high-risk patients with severe MR were evaluated for TMVI. Clinical, echocardiographic and functional outcomes between the subgroups of patients treated with TMVI and MT were compared. The primary combined endpoint was all-cause death or heart failure (HF) hospitalization at 1 year. Subgroup analyses were performed to define specific patient subsets favouring either TMVI or MT.

Results

At baseline, there were no differences between the TMVI group (n = 38) and the MT group (n = 44) regarding age (all TMVI vs. MT: 77.0 years [IQR 72.9, 80.1] vs. 79.0 [IQR 76.0, 81.7], p = 0.13), gender (42.1% female vs. 56.8% female, p = 0.27) and estimated surgical risk (EuroSCORE II 4.4% [IQR 2.8, 13.6] vs. 6.4 [IQR 3.4, 10.1], p = 0.72). Patients undergoing TMVI were more frequently treated for secondary MR (68.4%), while primary MR was the most prevalent MR etiology in patients remaining on medical therapy (50.0%). Left ventricular (LV) end-diastolic diameters (LVEDD) were larger and LV ejection fraction (LVEF) was lower in the TMVI group (LVEDD 58.0mm [IQR 51.4, 65.0], LVEF 37.0% [IQR 31.4, 51.2]) compared to the MT group (LVEDD 52.0mm [IQR 46.2, 58.8], LVEF 54.5% [IQR 40.8, 60.0]) (p = 0.02 for LVEDD, p < 0.001 for LVEF). MR was effectively reduced to ≤ mild MR in all patients undergoing TMVI. In the MT group, MR remained severe in 90% of patients after 1 year. The primary composite endpoint occurred numerically more often in the MT group (72.2%) compared to the TMVI group (51.6%, p = 0.061). Regarding the primary endpoint, the subgroups of patients with LVEF 30-49% (HR 0.28 [95%-CI 0.11-0.67], p = 0.004), effective regurgitant orifice area (EROA) <0.4 cm2 (HR 0.30 [95%-CI 0.13-0.71], p = 0.006), tricuspid annular plane systolic excursion (TAPSE) ≥17mm (HR 0.27 [95%-CI 0.11-0.67], p = 0.005) and New York Heart Association functional class III (HR 0.38 [95%-CI 0.18-0.81], p = 0.012) were more likely to benefit from TMVI compared to MT.

Conclusions

In patients with severe MR unsuitable for standard therapy, TMVI represents a reasonable therapeutic alternative yielding effective elimination of MR. While most patients eligible for TMVI suffer from secondary MR, the majority of patients remaining on MT has primary MR. The primary endpoint occurred numerically, yet not statistically, more often in patients on MT. Baseline echocardiography was able to identify subgroups of patients with beneficial outcome after TMVI.

Non-invasive risk prediction based on right ventricular function in patients with pulmonary arterial hypertension

Background

Individual risk assessment in patients with pulmonary arterial hypertension (PAH) is fundamental to improve their outcome. Although right ventricular (RV) dysfunction is a major determinant of outcome in PAH, echocardiographic measures of RV function are poorly represented by current risk models.

Objective

The objective of this study was to identify echocardiographic measures of RV function, which are associated with adverse outcome and to develop a non-invasive, echocardiography-based risk score for PAH patients.

Methods

In 254 patients with PAH we analyzed functional status, laboratory results, pulmonary function and echocardiographic measures. Echocardiographic measures comprised RV chamber diameters, right atrial area, fractional area change (FAC), tricuspid annular plane systolic excursion (TAPSE), 2D RV strain and pericardial effusion. We used Cox regression models to assess the association with the composite endpoint of 5-year all-cause death or lung transplantation. The analyses included a conventional model using only guideline-recommended variables and a model adding significant echocardiographic measures. Based on the final multivariable model a point risk score was derived, indicating the association with the primary outcome.

Results

Median age was 65.5 years, 33.9% were females. During a median follow-up time of 4.18 years 74 patients died (n=63) or underwent lung transplantation (n=11). In univariable analyses low systolic blood pressure (Hazard ratio [HR] 0.99, 95% Confidence Interval [CI] 0.98,1.00), NYHA functional class IV (HR 3.23, 95% CI 1.48,7.07), 6-minute walk distance (HR 1.00, 95% CI 1.00,1.00), NT-proBNP concentrations (HR 1.00, 95% CI 1.00,1.00), renal impairment (HR 0.99, 95% CI 0.98,1.00), reduced diffusion capacity for carbon monoxide (HR 0.99, 95% CI 0.98,1.00), reduced TAPSE (HR 0.90, 95% CI 0.85,0.96) and reduced FAC (HR 0.97, 95% CI 0.94,1.00) were associated with the endpoint. A multivariable, conventional risk model, including NYHA functional class, 6-minute walk distance, NT-proBNP concentrations, pericardial effusion and right atrial area, resulted in a C-Index of 0.539. Adding TAPSE and FAC to this model improved the performance significantly (C-index 0.639, p-value 0.017). This model was translated to a 12-point score with the highest weighting assigned to TAPSE, FAC, pericardial effusion and 6-minute walk distance (Figure).

Conclusion

An easily applicable score integrating non-invasive, echocardiographic parameters of RV function improves prediction of adverse outcome in PAH patients.

Funding Acknowledgement

Type of funding sources: None. Risk prediction chart

Long-Term survival and functional status in patients with elevated mitral valve pressure gradient after transcatheter mitral valve repair

Background

A growing number of patients are currently treated for severe mitral regurgitation (MR) using a transcatheter mitral valve repair (TMVr). In clinical routine, the potential risk of elevated post-procedural mitral valve pressure gradient (MPG) may prohibit optimal MR reduction driven by the avoidance of additional clip implantations. Thus, the unfavorable impact on survival and functional outcome of increased MPG in patients undergoing TMVr is currently debatable.

Methods

In this single-center, prospective study, survival and functional outcome of 780 consecutive patients with severe MR undergoing TMVr between September 2008 and January 2020 were investigated. After exclusion of patients with unsuccessful procedure and those lost to follow-up, data of 676 patients with a median follow-up time of 5.26 (5.11, 5.51) years were analyzed. MPG was determined by transthoracic echocardiography at discharge and considered elevated in excess of 4.5 mmHg. Kaplan-Meier analysis as well as multivariable Cox regression models were performed for the impact on elevated MPG on 5-year outcomes for the subgroups of functional MR (FMR) and degenerative MR (DMR). The primary outcome measure was a combined endpoint of death or rehospitalization for congestive heart failure.

Results

Among 676 patients undergoing TMVr (mean age 74.6±8.5 years, 59.0% male, median STS Score 3.9 [interquartile range 2.5; 6.0]), 179 (26.4%) patients had elevated MPG >4.5 mmHg. FMR was present in 426 (63.0%) patients. In the overall patient cohort, Kaplan-Meier and Cox Regression analyses could not demonstrate significant differences for the combined endpoint (p=0.99). In contrast, subgroup analysis according to MR etiology indicated a significant adverse influence of elevated MPG on the combined endpoint as well as functional outcome in patients with DMR, but not with FMR (Figure 1). After adjustment, multivariate Cox Regression analysis showed an inferior prognosis in patients with DMR and elevated MVPG >4.5 mmHg (hazard ratio 1.79 [1.17, 2.72], p=0.0069, Figure 2).

Conclusions

TMVr-patients with DMR and measurable elevated post-procedural MVPG face an inferior prognosis and reduced functional outcomes compared to patients with FMR.

Funding Acknowledgement

Type of funding sources: None. Figure 1Figure 2

Accuracy and acute efficacy of a novel occlusion tool to guide cryoballoon-based pulmonary vein isolation

Background

Cryoballoon (CB)-based pulmonary vein isolation (PVI) currently requires to verify occlusion of each pulmonary vein (PV) using fluoroscopy and dye injection.

Objective

The current study evaluated whether the novel CB-occlusion tool integrated into the wide-band dielectric imaging system KODEX-EPD reliably verifies occlusion of PV according to a novel dye-injection based algorithm.

Methods

Consecutive patients suffering from symptomatic atrial fibrillation (AF) underwent CB-based PVI using the KODEX-EPD and the novel occlusion-tool (group I). To confirm accurate display of the PVs, selective PV-angiography was performed in the first half of the patients of group I (group Ia) in addition to a three-dimensional left atrial (LA) map using a spiral mapping catheter (Achieve, SMC1, Medtronic, MN, USA). PV-angiographies were waived for the following patients (group Ib). Procedural duration and radiation exposure were compared to a control group of patients undergoing conventional CB-based PVI.

Results

CB-based PVI was successful in 50/50 patients of group I (mean age 63±11 years, 18 paroxysmal (36%)) and 25/25 patients of group II (66±10 years, 9 paroxysmal (60%)). Concordance of PV-occlusion as assessed by either PV-occlusion-angiography or KODEX-EPD, was documented in 237/272 (87%) occlusion-analyses among 198 PVs (95% for left superior PV, 93% for left inferior PV, 86% for right inferior PV and 77% for right superior PV).

In the final evaluation phase (group Ib) LA fluoroscopy times and dose area products were comparable to the conventional CB-ablation group (10.5±5 vs 8.8±4 minutes (p=0.23) and 403±425 vs 321±202 cGycm2 (p=0.44), whereas the amount of dye could be significantly reduced (group Ib: 31±10 ml vs group II: 70±20 ml, p<0.0001).

Conclusion

The novel KODEX-EPD PV-occlusion tool allows for accurate PV-occlusion assessment in the majority of PVs and a high acute success rate. The system has the potential to reduce dye and radiation exposure. This should be evaluated in controlled clinical trials.

Funding Acknowledgement

Type of funding sources: None.

Multibiomarker model to discriminate Type 1 and Type 2 myocardial infarction

Background

The discrimination of patients with type 1 myocardial infarction (T1MI) from patients with type 2 MI (T2MI) is often challenging in the emergency department. Earlier we presented a discrimination model, which based on clinical variables, as well as on troponin concentrations. In the present analyses we sought to investigate the discriminative power of 28 biomarkers in patients with T1MI and T2MI.

Methods

Patients presenting to the emergency department with symptoms suggestive of MI were recruited. The final diagnosis of all patients was adjudicated by two physicians in a blinded fashion and based on the fourth universal definition of MI. For the present analyses only patients with T1MI and T2MI were used. In total 28 biomarkers were measured in blood samples collected directly at admission. A multivariable logistic regression model for T1MI vs T2MI as the dependent variable was used and the predictors were chosen via backward step-down selection.

Results

In total 138 patients (107 T1MI and 31 T2MI) were available for the analyses. The median age of the study population was 65 years and 66.7% were males. Hypertension was present in 77.4% and dyslipidemia in 41.3%. In the multivariable model four biomarkers (apolipoprotein A-II, n-terminal prohormone of brain natriuretic peptide, copeptin and high-sensitivity troponin I) were significant discriminators between T1MI and T2MI (Table 1). Internal validation of the model via bootstrap shows a for overoptimism corrected area under the curve of 0.82.

Conclusion

Using a multibiomarker approach discrimination between T1MI and T2MI could be improved. External validation of our findings is warranted.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Research fellowship by the Deutsche Forschungsgemeinschaft

Presentation characteristics, use of treatments and outcomes in patients with ischaemic vs. non-ischaemic cardiogenic shock

Aim

Evidence on non-ischaemic cardiogenic shock (CS) is scarce. The aim of this study was to investigate differences in presentation characteristics, use of treatments and outcomes in patients with ischaemic vs. non-ischaemic CS.

Methods

Patients with CS admitted to a tertiary care hospital between October 2009 and October 2017 were identified and stratified as ischaemic CS/non-ischaemic CS based on the presence/absence of acute myocardial infarction. Missing data was handled by chained equation multiple imputation. Logistic and Cox regression models were fitted to investigate the association of non-ischaemic CS with presentation characteristics (adjusted for all baseline variables), and use of treatments as well as30-day in-hospital mortality (adjusted for relevant confounders including age, sex, prior cardiac arrest, haemodynamics, pH and lactate).

Results

A total of 978 patients were enrolled in this study; median age was 70 (interquartile range 58, 79) years and 70% were male. 505 patients (43%) had non-ischaemic CS. Patients with non-ischaemic CS were more likely younger and female; were less likely to be active smokers or to have diabetes, but more likely to have chronic renal disease and history of myocardial infarction; and were more likely to present with unfavourable haemodynamics and with mechanical ventilation. Regarding use of treatments, patients with non-ischaemic CS were more likely to be treated with catecholamines [odds ratio (OR) 1.58, 95% confidence interval (CI) 1.11–2.27, p0.01], but less likely to be treated with extracorporeal membrane oxygenation (OR 0.66, 95% CI 0.48–0.92, p=0.02) or percutaneous left ventricular assist devices (OR 0.51, 0.35–0.74, p<0.01). Unadjusted survival probabilities in patients with non-ischaemic vs. ischaemic CS were 36% (95% CI 32–42%) vs. 39% (95% CI 35–45%). After adjustment for multiple relevant confounders, non-ischaemic CS was associated with a significant increase in the risk of 30-day in-hospital mortality (hazard ratio 1.30, 95% CI 1.09–1.55, p<0.01, Figure 1).

Conclusion

In this large study, non-ischaemic CS accounted for almost 50% of all CS cases. Non-ischaemic CS was not only associated with relevant differences in presentation characteristics and use of treatments, but also with a worse prognosis. These findings highlight the need for effective treatment strategies for patients with non-ischaemic CS.

Figure 1

Funding Acknowledgement

Type of funding source: None

Discrimination of myocardial infarction and myocardial injury using a multibiomarker approach

Background

In the Universal Definition of Myocardial Infarction (MI) myocardial injury was introduced as a specific diagnosis in patients with elevated troponin concentrations, but without evidence of acute myocardial ischemia. However, their differentiation within the acute setting might be challenging. Therefore, we sought to investigate a multibiomarker panel in these patients and determine the discriminative capacity to differentiation MI from myocardial injury.

Methods

We use a cohorts of acute patients presenting to the emergency department. All final diagnoses were adjudicated by two physicians in a blinded fashion and based on the fourth universal definition of MI. In case of disagreement a third physician referred. For the present analyses only patients diagnosed with MI or myocardial injury were used. A panel of 28 biomarkers was measured in blood samples collected directly at admission. Spearman correlations were calculated. A multivariable logistic regression model using MI as the dependent variable was used and the predictors were chosen via backward step-back selection. Odds ratios (OR) were calculated for each predictor.

Results

We included 359 patients; 138 were diagnosed as having MI and 221 has having myocardial injury. The median age of the study population was 73 years and 59.1% were males. Hypertension was diagnosed in 80.4%, dyslipidemia in 45.4% and diabetes in 19.0%.The biomarker panel showed a wide range of correlations (Figure 1). In the multivariable model five logarithmized biomarkers (N-terminal prohormone of brain natriuretic peptide [OR 0.62], pulmonary and activation-regulated chemokine [OR 0.51], tumor-necrosis-factor-receptor 2 [OR 2.22], copeptin [OR 1.59] and high-sensitivity troponin I [OR 1.80]) were significant discriminators between MI and myocardial injury. Internal validation of the model via bootstrap shows a for overoptimism corrected area under the curve of 0.84.

Conclusion

In the multivariable model five biomarkers were discriminators between MI and myocardial injury.

Spearman correlations

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Research fellowship by the Deutsche Forschungsgemeinschaft

Selective inhibition of guanylate cyclase prevents impairment of hypoxic pulmonary vasoconstriction in endotoxemic mice

Nitric oxide (NO) may cause sepsis-induced impairment of hypoxic pulmonary vasoconstriction (HPV). Although NO exerts many of its actions by activating soluble guanylate cyclase (sGC), there are several cGC-independent mechanisms that may lead to NO-induced vasodilation during endotoxemia. We investigated the role of sGC for the regulation of HPV during lipopolysaccharide (LPS) induced endotoxemia using 1H-(1,2,4)oxadiazole(4,3-alpha)quinoxaline-1-one (ODQ), a specific inhibitor of sGC, in isolated, perfused, and ventilated mouse lungs. Without ODQ, lungs from LPS-challenged mice constricted significantly less in response to hypoxia as compared to lungs from mice not treated with LPS (26 +/- 27% vs. 134 +/- 37%, respectively, p < 0.05). 20 mg/kg ODQ, but not 2 mg/kg or 10 mg/kg, restored the blunted HPV response in LPS-challenged mice as compared to mice not challenged with LPS (80+/-14 % vs. 98+/-21 %). ODQ had no effect on baseline perfusion pressures under normoxic conditions. Analysis of pulmonary vascular P-Q relationships suggested that the restoration of pulmonary vascular response to hypoxia by ODQ is associated with a restoration of pulmonary vascular properties during normoxia. Our data show in a murine model that specific inhibition of sGC may be a new approach to restore HPV during endotoxemia.

Worsening of long-term myocardial function after successful pharmacological pretreatment with cyclosporine

Pretreatment with cyclosporine (CsA) decreases infarct size 24h after myocardial ischemia/reperfusion (I/R). The goal of this study was to determine effects of CsA pretreatment on long-term cardiac function after I/R-injury. Rats were randomly assigned to group-1: vehicle-only, group-2: CsA-5mg/kg/day, and group-3: CsA-12.5mg/kg/day given orally for three days prior to I/R-injury (30 min of left anterior descending coronary artery occlusion). Post-I/R survival and cardiac function were evaluated 14 days after I/R-injury by echocardiography and invasive hemodynamic measurements. Rats with I/R-injury showed increased left ventricular pressure (LVEDP) compared to rats without I/R-injury (p<0.005). Although CsA initially decreased infarct size, no differences of LVEDP were seen 14 days after I/R-injury (vehicle: 21.2+/-8.9 mmHg, CsA-5mg/kg/day: 21.5+/-0.7 mmHg, CsA-12.5mg/kg/day: 20.5+/-9.4 mmHg). Ejection fraction and fractional shortening were decreased compared to baseline, but showed no differences between groups. On day 14, a dose-dependent increase in left ventricular end diastolic diameter was seen (p<0.001). CsA pretreatment was associated with a dose-dependent decrease in post-I/R-survival (vehicle: 56%, CsA-5mg/kg/day: 32%, CsA-12.5mg/kg/day: 16%; p=0.017). CsA pretreatment did not improve long-term cardiac function despite decreased infarct size 24h after I/R-injury, but increased post-I/R mortality significantly. Poor cardiac function after CsA pretreatment might be caused by left ventricular dilation.

[Hydrofluoric acid burns. A rare chemical emergency situation]

Burns caused by hydrofluoric acid can be life-threatening. Of special significance is the often underestimated local and sometimes delayed deep action of the highly diffusible free fluoride ions and the accompanying systemic toxicity. The specific antidote calcium gluconate can be topically applied, injected into tissue or infused intra-arterially. Because of the extreme danger of systemic toxicity even after seemingly trivial injuries, monitoring in the intensive care station, especially by measuring the calcium concentration in blood and electrocardiography, and therapy is recommended.

[Can lung protective ventilation methods modify outcome?--A critical review]

A large body of experimental and clinical work leaves no room for doubt that mechanical ventilation can contribute to the progression of a lung disease or, in the worst case, produce acute pulmonary damage. The pathophysiological processes involved have been described as barotrauma, volutrauma, atelectrauma and biotrauma. In response, a socalled lung-protective ventilation strategy has been proposed, especially for patients with acute respiratory distress syndrome (ARDS). Such an approach seeks to apply limited airway pressures, small tidal volumes and appropriate levels of positive end-expiratory pressures even if, as a consequence, non-physiological gas exchange values (i.e. elevated PaCO2-levels) need to be tolerated. A recent large prospective randomized trial demonstrated reduced mortality rates using such a strategy. To support lung-protective ventilation in ARDS patients, an array of therapeutic measures has been proposed, including meticulous attention to fluid and transfusion management, prone position, extracorporeal membrane oxygenation (ECMO), inhalation of nitric oxide, implementation of spontaneous breathing, partial liquid ventilation and tracheal gas insufflation. Of these, only prone positioning has become part of routine clinical management, while ECMO is applied in selected cases only. Unfortunately, thus far, none of these measures has passed the litmus test of a randomized controlled trial. Recent large prospective observational studies, however, suggest that only an optimized concert of therapeutic interventions, but not a single measure alone, may improve the outcome of ARDS patients.

[Imported tropical malaria after a sojourn in Kenya. Serious consequences of neglected chemoprophylaxis and delayed diagnosis]

HISTORY AND ADMISSION FINDINGS

A 56-year-old man was admitted to the hospital 11 days after returning from Kenya because of recurrent fever attacks. The patient had not taken malaria chemoprophylaxis and had previously received symptomatic treatment for suspected viral infection by his general practitioner. Physical findings on admission included enlargement of liver and spleen, marked dehydration and a body temperature of 40.1 degrees C.

INVESTIGATIONS

Initial chest radiography showed no abnormalities. Thick and thin blood smears were positive for Plasmodium falciparum. Initial parasitemia was 0.5 per thousand.

TREATMENT AND COURSE

Despite immediate quinine therapy including loading dose and intensive care treatment complicated malaria with multiorgan failure developed. The patient required mechanical ventilation, high-dose catecholamine treatment and hemodialysis for several days. The course of parasitemia peaked on treatment day 2 at a level of 31.1 per thousand.

CONCLUSION

Our case shows serious consequences and important complications of Plasmodium falciparum malaria in a patient without chemoprophylaxis and with delayed diagnosis. Fever following a stay in the tropics requires immediate testing for malaria infection.

Inhibition of lung phosphodiesterase improves responsiveness to inhaled nitric oxide in isolated-perfused lungs from rats challenged with endotoxin

OBJECTIVES

To investigate the ability of phosphodiesterase (PDE) selective inhibitors to improve responsiveness to inhaled nitric oxide (NO) in isolated-perfused lungs of rats pretreated with endotoxin/lipopolysaccharide (LPS).

DESIGN AND SETTING

Prospective, controlled animal study in the animal research facility of a university hospital.

INTERVENTIONS

Sixteen hours after adult Sprague-Dawley rats were injected intraperitoneally with 0.4 mg/ kg E. coli 0111:B4 LPS administration, lungs were isolated and perfused, and the thromboxane mimetic U46619 was employed to increase the mean pulmonary artery pressure by 5-7 mmHg. The lungs were then ventilated with or without 0.4 ppm NO, and erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA; PDE type 2 inhibitor), milrinone (PDE type 3 inhibitor), or zaprinast (inhibitor of PDE types 5 and 9) were added to the perfusate.

MEASUREMENTS AND RESULTS

In the presence of EHNA (12.5, 25, 50 microM) the vasodilator response to inhaled NO was not greater than in its absence (0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg vs. 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg, respectively). In the presence of milrinone (125, 250, 500 nM), the vasodilator response to inhaled NO was also not improved. In contrast, zaprinast (3.7, 7.4, 14.8 microM) augmented the pulmonary vasodilatory effect of inhaled NO in lungs from LPS-pretreated rats from 0.25 +/- 0.25, 0.5 +/- 0.25, 0.75 +/- 0.25 mmHg to 0.75 +/- 0.25, 1.5 +/- 0.5, 1.75 +/- 0.75 mmHg, respectively (p < 0.05).

CONCLUSIONS

Our results demonstrate that inhibition of pulmonary PDE enzyme activity with zaprinast increases vasodilator responsiveness to inhaled NO in lungs obtained from rats 16 h after LPS challenge.

Effects of oxygen and nitric oxide inhalation in a porcine model of recurrent microembolism

BACKGROUND

Inhalation of nitric oxide (iNO) has been proposed for the treatment of acute pulmonary embolism. The present study evaluates the effects of oxygen (O2) and nitric oxide inhalation in a porcine model of sustained pulmonary hypertension induced by recurrent pulmonary microembolism.

METHODS

Twelve pigs were embolized under general anesthesia with 300-microm microspheres intravenously three times over a period of seven weeks. Five pigs served as untreated controls. Hemodynamic and gas exchange responses to 100% oxygen and 40 ppm NO inhalation, and their combination (O2+iNO) were measured seven days after the last embolization.

RESULTS

Recurrent microembolism caused sustained pulmonary hypertension (pulmonary vascular resistance index; PVRI 408 +/- 57 dyn x s x cm(-5) x m(-2)) as compared to the control group (PVRI 143 +/- 20 dyn x s x cm(-5) m(-2); P<0.05). PVRI was significantly reduced by O2, iNO, and O2+iNO inhalation by 29 +/- 3, 28 +/- 4, and 32 +/- 3%, respectively.

CONCLUSION

We conclude that both O2 and iNO are selective pulmonary vasodilators in a porcine model of sustained pulmonary hypertension following recurrent pulmonary microembolism and, therefore, may be useful in the treatment not only in the acute phase of pulmonary embolism but also later in the time course of the disease.

Exhaled nitric oxide production by nitric oxide synthase-deficient mice

Nitric oxide (NO) is produced in the nasal cavities, airways, and lungs and is exhaled by normal animals and humans. Although increased exhaled NO concentrations in airway inflammation have been associated with increased airway expression of nitric oxide synthase 2 (NOS 2), it is uncertain which NOS isoform is responsible for baseline levels of exhaled NO. We therefore studied wild-type mice and mice with a congenital deficiency of NOS 1, NOS 2, or NOS 3. By studying a closed chamber in which the exhaled gas of a group of mice was collected, gaseous NO production rates were measured. Wild-type mice exhaled 362 +/- 35 x 10(-15) mol g(-1) min(-1) NO (mean +/- SE, n = 16 groups of five mice), NOS 1-deficient mice exhaled 592 +/- 74 x 10(-15) mol g(-1) min(-1) NO (n = 15 groups, p < 0.05 versus wild-type and NOS 2-deficient mice), NOS 2-deficient mice 330 +/- 74 x 10(-15) mol g(-1) min(-1) NO (n = 14 groups) and NOS 3-deficient mice 766 +/- 101 x 10(-15) mol g(-1) min(-1) NO (n = 16 groups, p < 0.001 versus wild-type and NOS 2-deficient mice). Pharmacological NOS inhibition with L-NAME decreased (p < 0.05) the exhaled NO production rate of wild-type and NOS 3-deficient but not of NOS 2-deficient mice. L-Arginine administration increased exhaled NO production rate in all but NOS 2-deficient mice. Absence of NOS 1 or 3 is associated with increased murine exhaled NO production rates. Since NOS 2-deficient mice were the only genotype to lack substrate- and inhibitor-regulated changes of NO exhalation, we suggest that NOS 2 is an important isoform contributing to exhaled NO exhalation in healthy mice.

Nitric oxide inhalation decreases pulmonary artery remodeling in the injured lungs of rat pups

Vascular injury causes the muscularization of peripheral pulmonary arteries, which is more pronounced in the infant than in the adult lung. Although inhaled NO gas attenuates pulmonary artery remodeling in hypoxic rats, whether or not it protects the lung by mitigating vasoconstriction is unknown. This investigation tested whether inhaled NO decreases the muscularization of injured pulmonary arteries in rat pups by modulating vascular tone. One week after monocrotaline administration, the percentage of muscularized rat pup lung arteries was increased by >3-fold. Nevertheless, monocrotaline exposure did not cause right ventricular hypertrophy, pulmonary hypertension, or vasoconstriction. In addition, it did not increase the expression of markers of inflammation (interleukin-1beta, intercellular adhesion molecule-1, and E-selectin) or of platelet-mediated thrombosis (GPIbalpha). Continuous inhalation of 20 ppm NO gas prevented the neomuscularization of the pulmonary arteries in pups with lung injury. Moreover, a 3-fold increase in cell proliferation and 30% decrease in cell numbers in pulmonary arteries caused by monocrotaline exposure was prevented by NO inhalation. These data indicate that inhaled NO protects infants against pulmonary remodeling induced by lung injury by mechanisms that are independent of pulmonary tone, inflammation, or thrombosis.

Sildenafil is a pulmonary vasodilator in awake lambs with acute pulmonary hypertension

BACKGROUND

Phosphodiesterase type 5 (PDE5) hydrolyzes cyclic guanosine monophosphate in the lung, thereby modulating nitric oxide (NO)/cyclic guanosine monophosphate-mediated pulmonary vasodilation. Inhibitors of PDE5 have been proposed for the treatment of pulmonary hypertension. In this study, we examined the pulmonary and systemic vasodilator properties of sildenafil, a novel selective PDE5 inhibitor, which has been approved for the treatment of erectile dysfunction.

METHODS

In an awake lamb model of acute pulmonary hypertension induced by an intravenous infusion of the thromboxane analog U46619, we measured the effects of 12.5, 25, and 50 mg sildenafil administered via a nasogastric tube on pulmonary and systemic hemodynamics (n = 5). We also compared the effects of sildenafil (n = 7) and zaprinast (n = 5), a second PDE5 inhibitor, on the pulmonary vasodilator effects of 2.5, 10, and 40 parts per million inhaled NO. Finally, we examined the effect of infusing intravenous l-NAME (an inhibitor of endogenous NO production) on pulmonary vasodilation induced by 50 mg sildenafil (n = 6).

RESULTS

Cumulative doses of sildenafil (12.5, 25, and 50 mg) decreased the pulmonary artery pressure 21%, 28%, and 42%, respectively, and the pulmonary vascular resistance 19%, 23%, and 45%, respectively. Systemic arterial pressure decreased 12% only after the maximum cumulative sildenafil dose. Neither sildenafil nor zaprinast augmented the ability of inhaled NO to dilate the pulmonary vasculature. Zaprinast, but not sildenafil, markedly prolonged the duration of pulmonary vasodilation after NO inhalation was discontinued. Infusion of l-NAME abolished sildenafil-induced pulmonary vasodilation.

CONCLUSIONS

Sildenafil is a selective pulmonary vasodilator in an ovine model of acute pulmonary hypertension. Sildenafil induces pulmonary vasodilation via a NO-dependent mechanism. In contrast to zaprinast, sildenafil did not prolong the pulmonary vasodilator action of inhaled NO.

Right ventricular upregulation of the Ca(2+) binding protein S100A1 in chronic pulmonary hypertension

The Ca(2+) binding protein S100A1 increases the Ca(2+) release from the sarcoplasmatic reticulum by interacting with the ryanodine receptor. In order to understand whether this effect might be operative in the early course of hypertrophy, when myocardium is able to meet increased workload, we investigated the expression of S100A1 in a model of moderate right ventricular hypertrophy. The pulmonary arteries of nine pigs were embolised three times with Sephadex G-50. After 70 days, all pigs showed a moderate pulmonary hypertension. Right ventricular tissue of embolised animals showed a significant increase of connective tissue and enlargement of myocyte diameters. In controls, we found a differential expression of S100A1 with significantly lower S100A1 protein levels in right ventricular compared to left ventricular tissue. In pulmonary hypertension, S100A1 expression increased significantly in hypertrophied right ventricles while it was unchanged in left ventricular tissue. No change was observed in the expression of SERCA2a and phospholamban. Our data show, for the first time, that moderate pressure overload results in an upregulation of S100A1. This may reflect an adaptive response of myocardial Ca(2+) homeostasis to a higher workload.

Randomized, placebo-controlled, blinded and cross-matched study on the antiplatelet effect of inhaled nitric oxide in healthy volunteers

The platelet inhibitory effect of 0-40 ppm inhaled nitric oxide (NO) was investigated in healthy men and women. In both groups, ADP-and collagen-induced platelet aggregation was significantly inhibited 20 (T20) and 40 min (T40) after the beginning of inhalation of 5, 10, and 40 ppm. Moreover, in both men and women, the in vitro bleeding time was significantly prolonged at T20 and T40 during inhalation of 40 ppm. Inhalation of NO also inhibited P-selectin expression at 5, 10, and 40 ppm and fibrinogen binding to the GPIIb/IIIa-receptor at 40 ppm. In conclusion, in healthy volunteers, the platelet inhibitory effect of inhaled NO was not dose-related, since it was significant at 5 and 10 ppm but did not increase during the administration of higher NO concentrations. In addition, gender-related differences were only observed in ADP-induced platelet aggregation at 10 ppm and in bleeding time prolongation at 40 ppm.

Congenital NOS2 deficiency protects mice from LPS-induced hyporesponsiveness to inhaled nitric oxide

BACKGROUND

In animal models, endotoxin (lipopolysaccharide) challenge impairs the pulmonary vasodilator response to inhaled nitric oxide (NO). This impairment is prevented by treatment with inhibitors of NO synthase 2 (NOS2), including glucocorticoids and L-arginine analogs. However, because these inhibitors are not specific for NOS2, the role of this enzyme in the impairment of NO responsiveness by lipopolysaccharide remains incompletely defined.

METHODS

To investigate the role of NOS2 in the development of lipopolysaccharide-induced impairment of NO responsiveness, the authors measured the vasodilator response to inhalation of 0.4, 4, and 40 ppm NO in isolated, perfused, and ventilated lungs obtained from lipopolysaccharide-pretreated (50 mg/kg intraperitoneally 16 h before lung perfusion) and untreated wild-type and NOS2-deficient mice. The authors also evaluated the effects of breathing NO for 16 h on pulmonary vascular responsiveness during subsequent ventilation with NO.

RESULTS

In wild-type mice, lipopolysaccharide challenge impaired the pulmonary vasodilator response to 0.4 and 4 ppm NO (reduced 79% and 45%, respectively, P < 0.001), but not to 40 ppm. In contrast, lipopolysaccharide administration did not impair the vasodilator response to inhaled NO in NOS2-deficient mice. Breathing 20 ppm NO for 16 h decreased the vasodilator response to subsequent ventilation with NO in lipopolysaccharide-pretreated NOS2-deficient mice, but not in lipopolysaccharide-pretreated wild-type, untreated NOS2-deficient or untreated wild-type mice.

CONCLUSIONS

In response to endotoxin challenge, NO, either endogenously produced by NOS2 in wild-type mice or added to the air inhaled by NOS2-deficient mice, is necessary to impair vascular responsiveness to inhaled NO. Prolonged NO breathing, without endotoxin, does not impair vasodilation in response to subsequent NO inhalation. These results suggest that NO, plus other lipopolysaccharide-induced products, are necessary to impair responsiveness to inhaled NO in a murine sepsis model.

Trypsin and activation of circulating trypsinogen contribute to pancreatitis-associated lung injury

Pancreatic proteases are secreted in acute pancreatitis, but their contribution to associated lung injury is unclear. Applying models of mild edematous (intravenous caerulein) and severe necrotizing (intraductal glycodeoxycholic acid) pancreatitis in rats, we showed that both trypsinogen and trypsin concentrations in peripheral blood, as well as lung injury, correlate with the severity of the disease. To isolate the potential contribution of proteases to lung injury, trypsin or trypsinogen was injected into healthy rats or trypsinogen secreted in caerulein pancreatitis was activated by intravenous enterokinase. Pulmonary injury induced by protease infusions was dose dependent and was ameliorated by neutrophil depletion. Trypsinogen activation worsened lung injury in mild pancreatitis. In vitro incubation of leukocytes with trypsinogen showed that stimulated leukocytes can convert trypsinogen to trypsin. In conclusion, this study demonstrates that the occurrence and severity of pancreatitis-associated lung injury (PALI) corresponds to the levels of circulating trypsinogen and its activation to trypsin. Neutrophils are involved in both protease activation and development of pulmonary injury.

Selective vasodilation by nitric oxide inhalation during sustained pulmonary hypertension following recurrent microembolism in pigs

PURPOSE

This study establishes a new model of sustained pulmonary hypertension induced by recurrent microembolism in pigs and evaluates the effects of nitric oxide (NO) inhalation in this model.

MATERIALS AND METHODS

Fourteen pigs were embolized under general anesthesia with 300-microm microspheres intravenously three times over a period of 7 weeks. Four pigs served as untreated controls. Hemodynamic and gas exchange measurements were performed on days 1 and 7 after the last embolization.

RESULTS

Recurrent microembolism caused sustained pulmonary hypertension (mean pulmonary artery pressure [MPAP] 26 +/- 2 and 18 +/- 1 mm Hg on days 1 and 7, respectively) compared with the control group (MPAP 13 +/- 1 mm Hg each for days 1 and 7; P < .05, respectively). Right heart hypertrophy was present at autopsy as indicated by an increase in minimal myocyte diameter. Inhaled NO (5 and 40 parts per million [ppm]) was administered on days 1 and 7. On both days, inhaled NO significantly reduced MPAP and pulmonary vascular resistance without affecting systemic hemodynamics. There were no differences in responses to 5 and 40 ppm inhaled NO.

CONCLUSION

We conclude that recurrent microembolization in pigs provides a reliable model of sustained pulmonary hypertension. In this model inhaled NO is a selective pulmonary vasodilator, indicating that active vasoconstriction significantly contributes to sustained pulmonary hypertension after recurrent microembolism.

Sustained pulmonary hypertension and right ventricular hypertrophy after chronic hypoxia in mice with congenital deficiency of nitric oxide synthase 3

Chronic hypoxia induces pulmonary hypertension and right ventricular (RV) hypertrophy. Nitric oxide (NO) has been proposed to modulate the pulmonary vascular response to hypoxia. We investigated the effects of congenital deficiency of endothelial NO synthase (NOS3) on the pulmonary vascular responses to breathing 11% oxygen for 3-6 wk. After 3 wk of hypoxia, RV systolic pressure was greater in NOS3-deficient than in wild-type mice (35+/-2 vs 28+/-1 mmHg, x+/-SE, P < 0.001). Pulmonary artery pressure (PPA) and incremental total pulmonary vascular resistance (RPI) were greater in NOS3-deficient than in wild-type mice (PPA 22+/-1 vs 19+/-1 mmHg, P < 0.05 and RPI 92+/-11 vs 55+/-5 mmHg.min.gram.ml-1, P < 0.05). Morphometry revealed that the proportion of muscularized small pulmonary vessels was almost fourfold greater in NOS3-deficient mice than in wild-type mice. After 6 wk of hypoxia, the increase of RV free wall thickness, measured by transesophageal echocardiography, and of RV weight/body weight ratio were more marked in NOS3-deficient mice than in wild-type mice (RV wall thickness 0.67+/-0.05 vs 0.48+/-0.02 mm, P < 0.01 and RV weight/body weight ratio 2.1+/-0.2 vs 1.6+/-0.1 mg. gram-1, P < 0.05). RV hypertrophy produced by chronic hypoxia was prevented by breathing 20 parts per million NO in both genotypes of mice. These results suggest that congenital NOS3 deficiency enhances hypoxic pulmonary vascular remodeling and hypertension, and RV hypertrophy, and that NO production by NOS3 is vital to counterbalance pulmonary vasoconstriction caused by chronic hypoxic stress.

Reduction in nitrogen dioxide concentration by soda lime preparations during simulated nitric oxide inhalation

Nitrogen dioxide is formed during delivery of inhaled nitric oxide for the treatment of patients with pulmonary hypertension. Soda lime has been shown to absorb nitrogen dioxide. We tested three different commercially available soda lime preparations (Sodasorb, Drägersorb 800 and Sofnolime) for their efficacy in absorbing nitrogen dioxide and nitric oxide during simulated nitric oxide inhalation. All soda lime preparation absorbed nitrogen dioxide (15%, 24% and 34%, respectively). To test if this difference could be attributed to the potassium hydroxide (KOH) content of the different preparations, two other preparations with a higher (3.0% and 7.3% w/w, respectively) KOH content were tested and we found an increase in nitrogen dioxide removal up to 47% and 46%, respectively. We conclude that soda lime absorbed nitrogen dioxide during nitric oxide inhalation. This effect seemed to be moderate under simulated clinical conditions, but increased using soda lime with a higher KOH content. Nevertheless, we recommend continuous monitoring of inspired nitrogen dioxide concentration during clinical inhalation of nitric oxide.

Inhaled nitric oxide inhibits platelet aggregation after pulmonary embolism in pigs

BACKGROUND

Inhaled nitric oxide (NO) is reported to prolong bleeding time in animals and humans and to inhibit platelet aggregation in persons with acute respiratory distress syndrome. In pulmonary embolism (PE), inhibition of platelet aggregation appears useful because further thrombus formation may lead to right ventricular dysfunction that results in circulatory failure. In the present study, the effect of inhaled NO on platelet aggregation after acute massive PE was investigated.

METHODS

After acute massive PE was induced in 25 anesthetized pigs by injecting microspheres, 5, 20, 40, and 80 parts per million inhaled NO were administered stepwise for 10 min each in 11 animals (NO group). In the control group (n = 14). NO was not administered. Adenosine diphosphate-induced initial and maximal platelet aggregation were measured before PE (10), immediately after induction of PE (PE), at the end of each 10-min NO inhalation interval (t10-t40), and 15 min after cessation of NO inhalation (t55) in the NO group, and at corresponding times in the control group, respectively.

RESULTS

Two animals in the control group and one in the NO group died within 10 min after PE induction and were excluded from analysis. Peaking at t40 and t55, respectively, initial (-13 +/- 6%; P < 0.05) and maximal (+44 +/- 17%; P < 0.05) platelet aggregation increased significantly after PE in the control group. In contrast, NO administration after PE led to a significant decrease in initial (maximum decrease, -9 +/- 3% at t40; P < 0.05) and maximal (maximum decrease, -15 +/- 7% at t30; P < 0.05) platelet aggregation. In the NO group, platelet aggregation had returned to baseline levels again at t55. In addition, NO administration significantly decreased mean pulmonary artery pressure and significantly increased end-tidal carbon dioxide concentration and mean systemic blood pressure.

CONCLUSIONS

Inhaled NO has a systemic and rapidly reversible inhibitory effect on platelet aggregation after acute massive PE in pigs. This may be beneficial in treating acute massive PE.

Inhaled nitric oxide selectively decreases pulmonary artery pressure and pulmonary vascular resistance following acute massive pulmonary microembolism in piglets

Acute massive pulmonary embolism increases pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR), which may lead to early right ventricular failure and subsequent cardiocirculatory deterioration. Inhaled nitric oxide (NO) selectively dilates pulmonary vessels in vivo. Thus, inhaled NO may be useful in preventing cardiocirculatory deterioration following pulmonary embolism. We investigated the effects of inhaled NO in the acute phase of massive pulmonary microembolism in 10 anesthetized and mechanically ventilated piglets (body weight, 18 +/- 2 kg). Microspheres of 300-microns diameter were injected i.v. in an amount sufficient to initially increase mean PAP to 45 mm Hg. Forty-five minutes after pulmonary embolization, the pretreatment control values were recorded. Thereafter, the piglets inhaled 40 ppm NO, and subsequently 80 ppm NO. When 40 ppm NO was inhaled, there was a significant decrease in systolic PAP (-10.3%; 44.5 +/- 2.2 to 39.9 +/- 2.4 mm Hg; p < 0.05) and mean PAP (-9.4%; 32.9 +/- 1.3 to 29.8 +/- 1.3 mm Hg; p < 0.05). PVR was changed by -13.6% (p = 0.07). Administration of 80 ppm NO resulted in a significant decrease in systolic PAP (-12.6%; to 38.9 +/- 1.9 mm Hg; p < 0.05), mean PAP (-11.9%; to 29.0 +/- 1.4 mm Hg; p < 0.05), and PVR (-19.4%; p < 0.05) compared with pretreatment values. Discontinuation of NO inhalation was associated with an immediate return to pretreatment values. Systemic hemodynamics and the arterial and mixed venous oxygen concentrations remained unchanged. We conclude that inhaled NO following acute massive pulmonary microembolism selectively decreases PAP and PVR without influencing systemic hemodynamics in piglets.

Different effect of inhaled nitric oxide on yucatan micropig with and without congenital ventricular septal defect

A strain of Yucatan micropigs is known to have heritable ventricular septal defects (VSDs) and thus may develop overflow pulmonary hypertension. Since inhaled nitric oxide (NO) selectively dilates pulmonary vessels, we determined its hemodynamic and co-agulatory effects in this new animal model. Eight Yucatan micropigs were anesthetized with midazolam, piritramide (a synthetic opioid) and vecuronium bromide. The presence and the size of the VSD were determined by using transesophageal color flow Doppler echocardiography. Four animals showed VSDs of 1-2 mm size. Inhaled NO was then administered with increasing inspired concentrations of 0, 5, 10, 20, 40, 80 and again 0 ppm NO for 10-min periods. NO inhalation did not affect heart rate, right cardiac output, mean arterial pressure, pulmonary arterial wedge pressure, or central venous pressure. Inhaled NO in animals with proven VSDs decreased pulmonary artery pressure (PAP) in a dose dependent manner; 5 ppm NO reduced mean PAP from 25 +/- 2.3 mm Hg to 18 +/- 0.8 mm Hg (p < 0.05), while pulmonary vascular resistance (PVR) decreased from 954 +/- 143 dyn.cm. s-5 to 661 +/- 88 dyn.cm.s-5 (p < 0.01) at the same dose. The maximum reduction in mean PAP and PVR occurred when 80 ppm NO was inhaled. Yucatan micropigs without VSDs did not respond hemodynamically to NO inhalation. Methemoglobin levels remained unchanged during the entire study. Platelet function was assessed according to the method of BREDDIN and BORN (BORN 1962). Initial aggregation and slope were affected when NO inhalation commenced. Yucatan micropigs with VSDs may represent a suitable model for further research of the in vivo effects of inhaled NO.

[Effect of resorption of Purisole (mannitol/sorbitol solution) as a distention medium in hysteroscopic operations on cardiovascular and laboratory parameters and energy metabolism--a prospective non-randomized observational study]

This paper reports on an open explorative study on the absorption of the electrolytfree distension medium Purisole (Mannitol-Sorbitol solution) during hysteroscopic procedures and its effects on laboratory and cardiovascular parameters. Intra- and postoperative levels of mannitol and sorbitol in urine were also measured to determine elimination of both components. The study population consisted of 84 patients aged 22-62 years. 54 women underwent ablative (resection of submucous fibroids, endometrial ablation, septum resection), 30 patients non-ablative operative hysteroscopic procedures (synechiolysis, hysteroscopic proximal tubal catheterisation). The duration of operations was between 23-48 minutes. Ethanol was added to the Purisole solution for determination of resorption. In 57 cases 1% ethanol in Purisole was used as irrigating fluid. In 27 cases 2% ethanol was added to the distension fluid. A median slight encrease of central venous pressure was noted during the procedures. 18 women had an intraoperative hyponatriaemia (only 4 patients < 130 mmmol/1). For the 15 patients, in which ethanol absorption was noted, fluid resorption was calculated on the basis of blood alcohol concentration (median 850 ml). Resorption was below the determination threshold in the other 69 women. Urine examination showed intra- and postoperatively increased concentrations of sorbitol and mannitol. Fluid overload and intraoperative cardiovascular complications did not occur in our patients.

[In vitro study of the formation of NO2 in inhalation of nitrogen monoxide]

OBJECTIVE

Nitric oxide (NO), an endogenous endothelium-derived relaxing factor, produces profound relaxation of vascular smooth muscle. Thus, inhaled NO is a potent and selective pulmonary vasodilator that may be useful for treatment of pulmonary hypertension of different aetiologies. However, the main danger of NO inhalation is spontaneous formation of toxic nitrogen dioxide (NO2) if NO is added to an oxygen-containing gas mixture. This chemical reaction depends on the time available for the oxidation and the concentration of NO and oxygen. The aim of this study was to assess in vitro the spontaneous formation of NO2 during administration of various NO concentrations with a ventilator. A modified ventilator system is described which can deliver NO within clinically relevant concentrations avoiding excessive formation of toxic NO2.

METHODS

The system was evaluated using an artificial lung. NO and NO2 concentrations were measured by chemiluminescence at the proximal and distal end of the inspiratory limb. In-vitro NO2 formation was assessed during administration of 10, 20, 40, 80 ppm NO while ventilating with an FiO2 of 0.25, 0.5 and 0.75, an inspiratory minute volume of 5, 7.5 and 10 l/min (IMV) and a respiratory rate of 12/min.

RESULTS

NO2 concentration correlated with increasing FiO2 and NO concentration and was inversely correlated to IMV. While ventilating with 5-40 ppm NO, an FiO2 of 0.25-0.75 and an IMV of 10 l per minute, the NO2 formation was measured to be less than 0.2 ppm and thus not clinically relevant. During administration of 80 ppm NO the NO2 formation increased to 0.3-0.6 ppm.

CONCLUSION

We conclude that for patients safety concentrations less than 80 ppm of inhaled NO should be used with this ventilator system. In addition, online monitoring of the NO2 concentration in the inspiratory limb should always be performed.

Influence of age on outcome of mechanically ventilated patients in an intensive care unit

OBJECTIVE

To assess the influence of age on the outcome of patients receiving prolonged mechanical ventilation.

DESIGN

Retrospective study.

SETTING

Intensive care unit.

PATIENTS

A total of 1,141 patients in our ICU during a 32-month period. A total of 536 patients required mechanical ventilation. After exclusion of 171 patients ventilated for less than 24 hrs after surgery, 365 patients were investigated.

MEASUREMENTS AND MAIN RESULTS

Two hundred sixty-six (73%) patients were aged less than 70 yrs; 99 (27%) patients were greater than or equal to 70 yrs. There was no significant difference in mortality rate between the younger and the older age groups. There was no significant influence of other important factors, such as severity of illness, duration of mechanical ventilation, or length of ICU stay. The only factor showing a significant influence on patient outcome was the reason for mechanical ventilation. There were more survivors in the group being ventilated because of ventilatory insufficiency than in the group with oxygenation impairment (57.8% vs. 23.9%, p less than .001).

CONCLUSION

An influence of age on the outcome of mechanically ventilated patients in the ICU could not be ascertained in this study.

[Thymomas (author's transl)]

Immunological investigations concerning pathological autoantibodies and defects of humoral immunity were performed in 7 patients with thymomas, 5 of which showed invasive growth. The number of B and T lymphocytes in blood was determined at the same time using membrane markers as well as blood lymphocyte stimulation with phytohaemagglutinine. Two of the 3 patients with auto-antibodies against striated muscles or nuclei showed the clinical signs of accompanying disease (myasthenia gravis, lupus erythematodes). A humoral immunodisturbance with IgM deficiency was demonstrable in one patient and was accompanied by clinical symptoms. Lymphopenia with decreased numbers and functional disturbance of T and B lymphocytes could be shown in the majority of patients. Immunological investigations simplify proof of accompanying diseases in thymomas. These represent an important prognostic criterium in the same way as does invasive growth.

Crosslinked insulins: preparation, properties, and application

Crosslinked insulins have proved to be valuable for structure-function studies and as proinsulin models. In the first part of the paper, a short review of the literature on analytical investigations, the preparation of A1-B1- and A1-B29-crosslinked derivatives, their biological activities in vivo and in vitro, and CD-spectral properties is given. The results of reduction/reoxidation studies with insulin derivatives containing irreversible and cleavable crosslinks are summarized. In the second part, new A1-B29-crosslinked monomers and 3 symmetrical dimers, linked between A1-A'1, B1-B'1 and B29-B'29, are described, as well as some results of tritium-labelling and of enzymatic degradation experiments with A1-B29-linked insulins.