Extracorporeal cardiopulmonary resuscitation in out-of-hospital cardiac arrest: a registry study

Aims

Out-of-hospital cardiac arrest (OHCA) without return of spontaneous circulation (ROSC) despite conventional resuscitation is common and has poor outcomes. Adding extracorporeal membrane oxygenation (ECMO) to cardiopulmonary resuscitation (extracorporeal-CPR) is increasingly used in an attempt to improve outcomes.

Methods and results

We analysed a prospective registry of 13 191 OHCAs in the Paris region from May 2011 to January 2018. We compared survival at hospital discharge with and without extracorporeal-CPR and identified factors associated with survival in patients given extracorporeal-CPR. Survival was 8% in 525 patients given extracorporeal-CPR and 9% in 12 666 patients given conventional-CPR (P = 0.91). By adjusted multivariate analysis, extracorporeal-CPR was not associated with hospital survival [odds ratio (OR), 1.3; 95% confidence interval (95% CI), 0.8–2.1; P = 0.24]. By conditional logistic regression with matching on a propensity score (including age, sex, occurrence at home, bystander CPR, initial rhythm, collapse-to-CPR time, duration of resuscitation, and ROSC), similar results were found (OR, 0.8; 95% CI, 0.5–1.3; P = 0.41). In the extracorporeal-CPR group, factors associated with hospital survival were initial shockable rhythm (OR, 3.9; 95% CI, 1.5–10.3; P = 0.005), transient ROSC before ECMO (OR, 2.3; 95% CI, 1.1–4.7; P = 0.03), and prehospital ECMO implantation (OR, 2.9; 95% CI, 1.5–5.9; P = 0.002).

Conclusions

In a population-based registry, 4% of OHCAs were treated with extracorporeal-CPR, which was not associated with increased hospital survival. Early ECMO implantation may improve outcomes. The initial rhythm and ROSC may help select patients for extracorporeal-CPR.

Experts' opinion on management of hemodynamics in ARDS patients: focus on the effects of mechanical ventilation

RATIONALE

Acute respiratory distress syndrome (ARDS) is frequently associated with hemodynamic instability which appears as the main factor associated with mortality. Shock is driven by pulmonary hypertension, deleterious effects of mechanical ventilation (MV) on right ventricular (RV) function, and associated-sepsis. Hemodynamic effects of ventilation are due to changes in pleural pressure (Ppl) and changes in transpulmonary pressure (TP). TP affects RV afterload, whereas changes in Ppl affect venous return. Tidal forces and positive end-expiratory pressure (PEEP) increase pulmonary vascular resistance (PVR) in direct proportion to their effects on mean airway pressure (mPaw). The acutely injured lung has a reduced capacity to accommodate flowing blood and increases of blood flow accentuate fluid filtration. The dynamics of vascular pressure may contribute to ventilator-induced injury (VILI). In order to optimize perfusion, improve gas exchange, and minimize VILI risk, monitoring hemodynamics is important.

RESULTS

During passive ventilation pulse pressure variations are a predictor of fluid responsiveness when conditions to ensure its validity are observed, but may also reflect afterload effects of MV. Central venous pressure can be helpful to monitor the response of RV function to treatment. Echocardiography is suitable to visualize the RV and to detect acute cor pulmonale (ACP), which occurs in 20-25 % of cases. Inserting a pulmonary artery catheter may be useful to measure/calculate pulmonary artery pressure, pulmonary and systemic vascular resistance, and cardiac output. These last two indexes may be misleading, however, in cases of West zones 2 or 1 and tricuspid regurgitation associated with RV dilatation. Transpulmonary thermodilution may be useful to evaluate extravascular lung water and the pulmonary vascular permeability index. To ensure adequate intravascular volume is the first goal of hemodynamic support in patients with shock. The benefit and risk balance of fluid expansion has to be carefully evaluated since it may improve systemic perfusion but also may decrease ventilator-free days, increase pulmonary edema, and promote RV failure. ACP can be prevented or treated by applying RV protective MV (low driving pressure, limited hypercapnia, PEEP adapted to lung recruitability) and by prone positioning. In cases of shock that do not respond to intravascular fluid administration, norepinephrine infusion and vasodilators inhalation may improve RV function. Extracorporeal membrane oxygenation (ECMO) has the potential to be the cause of, as well as a remedy for, hemodynamic problems. Continuous thermodilution-based and pulse contour analysis-based cardiac output monitoring are not recommended in patients treated with ECMO, since the results are frequently inaccurate. Extracorporeal CO2 removal, which could have the capability to reduce hypercapnia/acidosis-induced ACP, cannot currently be recommended because of the lack of sufficient data.

The role of beta-blockers in septic patients

β-blockers are widely used to treat cardiovascular diseases and in the peri-operative period in selected patients. The main benefit in terms of morbidity and/or mortality of their use is believed to be linked to specific effects on myocardial oxygen supply/demand balance, to anti-arrhythmic effects and anti-inflammatory effects. Use of β-blockers in severe sepsis is still under debate and if any, their appropriate indications remain unclear. In this article, we analyze the recent literature addressing the metabolic, immuno-modulatory and hemodynamic effects of non cardio-selective and of cardio-selective β-blockers in experimental and human sepsis in order to help clarifying the potential place of these drugs in patients with severe sepsis. From this analysis, it appears that β-adrenoceptor blocking agents may represent a therapeutic approach in patients with severe sepsis, in whom catecholaminergic hyperactivity including excessive tachycardia is supposed to play an aggravating role. However, many questions about effectiveness, safety and cardio-selectivity of the drugs and about the appropriate target population remain partially unanswered. Recently, esmolol, a short-time acting β1-adrenoceptor blocker titrated to decrease heart rate below 95 beats/min was shown to exert beneficial effects in a monocentric randomized clinical trial including selected septic patients. Further large multicenter randomized trials are required to confirm the potential benefit of such a therapy in patients with severe sepsis.

Pulse pressure variation and ARDS

Fluid management is a crucial issue in patients with acute respiratory distress syndrome (ARDS). Assessment of preload responsiveness should help to define the best fluid strategy. Arterial pulse pressure variation (PPV), which represents the amplitude of the respiratory changes in arterial pulse pressure, is considered as a marker of preload responsiveness in patients mechanically ventilated and fully adapted to their ventilator. The good ability of PPV to predict fluid responsiveness has been confirmed in various clinical situations (sepsis, operative and post-operative periods). However, there are a number of limits of using PPV (e.g., spontaneous breathing activity, cardiac arrhythmias, low tidal volume ventilation, low lung compliance), which are particularly important in ARDS. Clinical studies have confirmed the poor reliability of PPV in predicting fluid responsiveness in patients with ARDS, ventilated according to the currently recommended lung protective strategy. Although a PPV >10-12% still keeps its good predictive value, a lower PPV (<10%) is far to guarantee fluid unresponsiveness since many false-negative cases can be encountered in this setting. Thus, performance of alternative preload responsiveness tests such as passive leg raising or end-expiratory occlusion tests, is necessary when low PPV values are measured. This review addresses the meaning of PPV, its conditions of use and its limits in ARDS patients.

Complications related to less-invasive haemodynamic monitoring

BACKGROUND

The aim of this study was to evaluate the type and incidence of complications during insertion, maintenance, and withdrawal of central arterial catheters used for transpulmonary thermodilution haemodynamic monitoring (PiCCO™).

METHODS

We conducted a prospective, observational, multicentre study in 14 European intensive care units (six countries). A total of 514 consecutive patients in whom haemodynamic monitoring by PiCCO™ was indicated were studied.

RESULTS

Five hundred and fourteen PiCCO catheters (475 in femoral, 26 in radial, nine in axillary, and four in brachial arteries) were inserted. Arterial access was obtained on the first attempt in 86.4% of the patients. Minor problems such as oozing after insertion (3.3%) or removal of the catheter (3.5%) were observed, but no episodes of serious bleeding (more than 50 ml) were recorded. Small local haematomas were observed after insertion (4.5%) and after removal (1.2%) of the catheter. These complications were not more frequent in patients with coagulation abnormalities. The incidence of site inflammation and catheter-related infection was 2% and 0.78%, respectively. Other complications such as ischaemia (0.4%), pulse loss (0.4%), or femoral artery thrombosis (0.2%) were rare, transient, and all resolved with catheter removal or embolectomy, respectively.

CONCLUSIONS

In this series of patients, central arterial catheters used for PiCCO™ monitoring were demonstrated to be a safe alternative for advanced haemodynamic monitoring.

Meaning of arterio-venous PCO2 difference in circulatory shock

The arterovenous difference in carbon dioxide tension (DeltaPCO2) can be calculated after simultaneous sampling of arterial blood (PaCO2) and of mixed venous blood from the distal of a pulmonary artery catheter (PvCO2). Under physiological conditions, DeltaPCO2 ranges from 2 to 5 mmHg. The DeltaPCO2 depends on carbon dioxide and cardiac output by a complex fashion. In this article, we detail the influence of these factors on DeltaPCO2 in normoxic conditions and in hypoxic conditions. We bring evidence that DeltaPCO2 cannot serve as a marker of tissue hypoxia contrary to what was initially thought. However, DeltaPCO2 can be considered as a marker of the adequacy of venous blood flow (i.e. cardiac output) to remove the total CO2 produced by the peripheral tissues. In this regard, the knowledge of DeltaPCO2 should help the clinicians for the decision of giving therapy aimed at increasing cardiac output.

Rapid and beneficial hemodynamic effects of activated protein C in septic shock patients

OBJECTIVE

Because recombinant human activated protein C (rhAPC) reduces NO production during sepsis, it could improve the vascular tone. We tested whether rhAPC reduces the dose of norepinephrine required to maintain mean arterial pressure (MAP) in septic shock patients.

DESIGN AND SETTING

Retrospective study in intensive care unit of two university hospitals.

PATIENTS

Twenty-two septic shock patients with at least two organ failures were retrospectively investigated for MAP and the required dose of norepinephrine before and 24 h after rhAPC administration. A control group of 22 septic shock patients with at least two organ failures who did not receive rhAPC was matched on age, SAPS II, MAP, and norepinephrine dose at the time of the theoretical start of rhAPC.

MEASUREMENTS AND RESULTS

The MAP remained stable and similar in the two groups (86+/-16 vs. 89+/-9 mmHg at 24 h). The required dose of norepinephrine increased in the control group (+38%, from -41% to +38%) but decreased in the treated group (-33%, from -74% to +11%).

CONCLUSIONS

rhAPC rapidly improved the vascular tone in septic shock patients as assessed by a decrease in the norepinephrine dose required to maintain arterial pressure.

[Mechanical ventilation-related variability of stroke volume. Clinical evaluation and therapeutic implications]

Mechanical ventilation induces cyclic changes in left ventricular stroke volume. These variations are mainly related to the expiratory decrease in left ventricular preload following the inspiratory decrease in right ventricular filling and ejection. Therefore, the magnitude of the respiratory changes in left ventricular stroke volume reflect the sensitivity of the heart to the cyclic changes in preload induced by mechanical insufflation. At the bedside, the respiratory changes in left ventricular stroke volume can be assessed by the analysis of the arterial pressure (arterial catheter) or aortic blood velocity (echocardiography) wave forms. The respiratory changes in arterial pressure and in aortic blood velocity have been shown to be accurate predictors of fluid responsiveness and of the hemodynamic effects of positive end-expiratory pressure.

Effects of tidal volume reduction in acute respiratory distress syndrome on gastric mucosal perfusion

OBJECTIVE

This study was conducted with the aim of testing the effects of a reduction in tidal volume (V(T)) on gastric mucosal perfusion using laser-Doppler flowmetry in patients with acute respiratory distress syndrome (ARDS).

DESIGN

It was designed as a prospective study.

PATIENTS

Seventeen patients with ARDS were enrolled in the study. All patients were mechanically ventilated in volume-controlled mode. Before the start of the protocol, V(T) was set at 9 ml/kg body weight.

INTERVENTION

V(T) was reduced to 6 ml/kg body weight.

MEASUREMENTS AND RESULTS

Measurements of systemic hemodynamic parameters and gastric mucosal blood flow (GMBF) were obtained before and after reduction of V(T). Cardiac index, heaart rate and pulmonary arterial pressure increased significantly after V(T) reduction. The increase in cardiac output was observed in all patients. However, despite a mean 25% increase in cardiac output after V(T) reduction, no significant increase in mean GMBF was observed, and individual GMBF responses were heterogeneous.

CONCLUSION

V(T) reduction in patients with ARDS, despite resulting in an increase in cardiac output, did not change gastric mucosal perfusion. The heterogeneity in the individual response of GMBF to V(T) reduction could be due to opposite direct (i.e., local vasodilatory effect) and indirect (i.e., global sympathetic stimulation) effects of hypercapnia on gut vessels.

Respiratory changes in aortic blood velocity as an indicator of fluid responsiveness in ventilated patients with septic shock

STUDY OBJECTIVE

To investigate whether the respiratory changes in peak velocity (Vpeak) of aortic blood flow could be related to the effects of volume expansion on cardiac index.

DESIGN

Prospective clinical study.

SETTING

Medical ICUs of a university hospital (20 beds) and of a nonuniversity hospital (15 beds).

PATIENTS

Nineteen sedated septic shock patients who were receiving mechanical ventilation and who had preserved left ventricular (LV) systolic function.

INTERVENTION

Volume expansion.

MEASUREMENTS AND RESULTS

Analysis of aortic blood flow by transesophageal echocardiography allowed beat-to-beat measurement of Vpeak before and after volume expansion. Maximum values of Vpeak (Vpeakmax) and minimum values of Vpeak (Vpeakmin) were determined over one respiratory cycle. The respiratory changes in Vpeak (Delta Vpeak) were calculated as the difference between Vpeakmax and Vpeakmin divided by the mean of the two values and were expressed as a percentage. The indexed LV end-diastolic area (EDAI) and cardiac index were obtained at the end of the expiratory period. The volume expansion-induced increase in cardiac index was > or = 15% in 10 patients (responders) and < 15% in 9 patients (nonresponders). Before volume expansion, Delta Vpeak was higher in responders than in nonresponders (20 +/- 6% vs 10 +/- 3%; p < 0.01), while EDAI was not significantly different between the two groups (9.7 +/- 3.7 vs 9.7 +/- 2.4 cm(2)/m(2)). Before volume expansion, a Delta Vpeak threshold value of 12% allowed discrimination between responders and nonresponders with a sensitivity of 100% and a specificity of 89%. Volume expansion-induced changes in cardiac index closely correlated with the Delta Vpeak before volume expansion (r(2) = 0.83; p < 0.001).

CONCLUSION

Analysis of respiratory changes in aortic blood velocity is an accurate method for predicting the hemodynamic effects of volume expansion in septic shock patients receiving mechanical ventilation who have preserved LV systolic function.

Extending inspiratory time in acute respiratory distress syndrome

OBJECTIVE

To assess the short-term effects of extending inspiratory time by lengthening end-inspiratory pause (EIP) without inducing a clinically significant increase in intrinsic positive end-expiratory pressure (PEEPi) in patients with acute respiratory distress syndrome (ARDS).

DESIGN

Controlled, randomized, crossover study.

SETTING

Two medical intensive care units of university hospitals.

PATIENTS

Sixteen patients with early (< or =48 hrs) ARDS.

INTERVENTION

We applied two durations of EIP (0.2 secs and extended) each for 1 hr while keeping all the following ventilatory parameters constant: FIO2, total PEEP (PEEPtot = applied PEEP + PEEPi), tidal volume, inspiratory flow, and respiratory rate. The duration of extended EIP was titrated to avoid an increase of PEEPi of > or =1 cm H2O.

MEASUREMENTS AND MAIN RESULTS

Despite an increase in mean airway pressure (20.6 +/- 2.3 vs. 17.6 +/- 2.1 cm H2O, p < .01), extended EIP did not significantly improve PaO2 (93 +/- 21 vs. 86 +/-16 torr [12.40 +/- 2.80 vs. 11.46 +/- 2.13 kPa] with 0.2 secs EIP, NS). However, although the difference in PaO2 between the two EIP durations was <20 torr (<2.66 kPa) in 14 patients, two patients exhibited a >40 torr (>5.33 kPa) increase in PaO2 with extended EIP. Extended EIP decreased PaCO2 (62 +/- 13 vs. 67 +/- 13 torr [8.26 +/- 1.73 vs. 8.93 +/- 1.73 kPa] with 0.2 secs EIP, p < .01), which resulted in a higher pH (7.22 +/- 0.10 vs. 7.19 +/- 0.09 with 0.2 secs EIP, p < .01) and contributed to a slight increase in arterial hemoglobin saturation (94 +/- 3 vs. 93 +/- 3% with 0.2 EIP, p < .01). No significant difference in hemodynamics was observed.

CONCLUSION

In patients with ARDS, extending EIP without inducing a clinically significant increase in PEEPi does not consistently improve arterial oxygenation but enhances CO2 elimination.

Estimating cardiac filling pressure in mechanically ventilated patients with hyperinflation

OBJECTIVE

When positive end-expiratory pressure (PEEP) is applied, the intracavitary left ventricular end-diastolic pressure (LVEDP) exceeds the LV filling pressure because pericardial pressure exceeds 0 at end-expiration. Under those conditions, the LV filling pressure is itself better reflected by the transmural LVEDP (tLVEDP) (LVEDP minus pericardial pressure). By extension, end-expiratory pulmonary artery occlusion pressure (eePAOP), as an estimate of end-expiratory LVEDP, overestimates LV filling pressure when pericardial pressure is >0, because it occurs when PEEP is present. We hypothesized that LV filling pressure could be measured from eePAOP by also knowing the proportional transmission of alveolar pressure to pulmonary vessels calculated as index of transmission = (end-inspiratory PAOP--eePAOP)/(plateau pressure--total PEEP). We calculated transmural pulmonary artery occlusion pressure (tPAOP) with this equation: tPAOP = eePAOP--(index of transmission x total PEEP). We compared tPAOP with airway disconnection nadir PAOP measured during rapid airway disconnection in subjects undergoing PEEP with and without evidence of dynamic pulmonary hyperinflation.

DESIGN

Prospective study.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

We studied 107 patients mechanically ventilated with PEEP for acute respiratory failure. Patients without dynamic pulmonary hyperinflation (group A; n = 58) were analyzed separately from patients with dynamic pulmonary hyperinflation (group B; n = 49).

INTERVENTION

Transient airway disconnection.

MEASUREMENTS AND MAIN RESULTS

In group A, tPAOP (8.5+/-6.0 mm Hg) and nadir PAOP (8.6+/-6.0 mm Hg) did not differ from each other but were lower than eePAOP (12.4+/-5.6 mm Hg; p < .05). The agreement between tPAOP and nadir PAOP was good (bias, 0.15 mm Hg; limits of agreement, -1.5-1.8 mm Hg). In group B, tPAOP (9.7+/-5.4 mm Hg) was lower than both nadir PAOP and eePAOP (12.1+/-5.4 and 13.9+/-5.2 mm Hg, respectively; p < .05 for both comparisons). The agreement between tPAOP and nadir PAOP was poor (bias, 2.3 mm Hg; limits of agreement, -0.2-4.8 mm Hg).

CONCLUSIONS

Indexing the transmission of proportional alveolar pressure to PAOP in the estimation of LV filling pressure is equivalent to the nadir method in patients without dynamic pulmonary hyperinflation and may be more reliable than the nadir PAOP method in patients with dynamic pulmonary hyperinflation.

Venoarterial CO(2) difference during regional ischemic or hypoxic hypoxia

To test the role of blood flow in tissue hypoxia-related increased veno-arterial PCO(2) difference (DeltaPCO(2)), we decreased O(2) delivery (&Ddot;O(2)) by either decreasing flow [ischemic hypoxia (IH)] or arterial PO(2) [hypoxic hypoxia (HH)] in an in situ, vascularly isolated, innervated dog hindlimb perfused with a pump-membrane oxygenator system. Twelve anesthetized and ventilated dogs were studied, with systemic hemodynamics maintained within normal range. In the IH group (n = 6), hindlimb DO(2) was progressively lowered every 15 min by decreasing pump-controlled flow from 60 to 10 ml. kg(-1). min(-1), with arterial PO(2) constant at 100 Torr. In the HH group (n = 6), hindlimb DO(2) was progressively lowered every 15 min by decreasing PO(2) from 100 to 15 Torr, when flow was constant at 60 ml. kg(-1). min(-1). Limb DO(2), O(2) uptake (VO(2)), and DeltaPCO(2) were obtained every 15 min. Below the critical DO(2), VO(2) decreased, indicating dysoxia, and O(2) extraction ratio (VO(2)/DO(2)) rose continuously and similarly in both groups, reaching a maximal value of approximately 90%. DeltaPCO(2) significantly increased in IH but never differed from baseline in HH. We conclude that absence of increased DeltaPCO(2) does not preclude the presence of tissue dysoxia and that decreased flow is a major determinant in increased DeltaPCO(2).

Relation between respiratory changes in arterial pulse pressure and fluid responsiveness in septic patients with acute circulatory failure

In mechanically ventilated patients with acute circulatory failure related to sepsis, we investigated whether the respiratory changes in arterial pressure could be related to the effects of volume expansion (VE) on cardiac index (CI). Forty patients instrumented with indwelling systemic and pulmonary artery catheters were studied before and after VE. Maximal and minimal values of pulse pressure (Pp(max) and Pp(min)) and systolic pressure (Ps(max) and Ps(min)) were determined over one respiratory cycle. The respiratory changes in pulse pressure (DeltaPp) were calculated as the difference between Pp(max) and Pp(min) divided by the mean of the two values and were expressed as a percentage. The respiratory changes in systolic pressure (DeltaPs) were calculated using a similar formula. The VE-induced increase in CI was >/= 15% in 16 patients (responders) and < 15% in 24 patients (nonresponders). Before VE, DeltaPp (24 +/- 9 versus 7 +/- 3%, p < 0.001) and DeltaPs (15 +/- 5 versus 6 +/- 3%, p < 0.001) were higher in responders than in nonresponders. Receiver operating characteristic (ROC) curves analysis showed that DeltaPp was a more accurate indicator of fluid responsiveness than DeltaPs. Before VE, a DeltaPp value of 13% allowed discrimination between responders and nonresponders with a sensitivity of 94% and a specificity of 96%. VE-induced changes in CI closely correlated with DeltaPp before volume expansion (r(2) = 0. 85, p < 0.001). VE decreased DeltaPp from 14 +/- 10 to 7 +/- 5% (p < 0.001) and VE-induced changes in DeltaPp correlated with VE-induced changes in CI (r(2) = 0.72, p < 0.001). It was concluded that in mechanically ventilated patients with acute circulatory failure related to sepsis, analysis of DeltaPp is a simple method for predicting and assessing the hemodynamic effects of VE, and that DeltaPp is a more reliable indicator of fluid responsiveness than DeltaPs.

Using heart-lung interactions to assess fluid responsiveness during mechanical ventilation

According to the Frank-Starling relationship, a patient is a 'responder' to volume expansion only if both ventricles are preload dependent. Mechanical ventilation induces cyclic changes in left ventricular (LV) stroke volume, which are mainly related to the expiratory decrease in LV preload due to the inspiratory decrease in right ventricular (RV) filling and ejection. In the present review, we detail the mechanisms by which mechanical ventilation should result in greater cyclic changes in LV stroke volume when both ventricles are 'preload dependent'. We also address recent clinical data demonstrating that respiratory changes in arterial pulse (or systolic) pressure and in Doppler aortic velocity (as surrogates of respiratory changes in LV stroke volume) can be used to detect biventricular preload dependence, and hence fluid responsiveness in critically ill patients.

Association of TNF2, a TNF-alpha promoter polymorphism, with septic shock susceptibility and mortality: a multicenter study

CONTEXT

Tumor necrosis factor alpha (TNF-alpha) is believed to be a cytokine central to pathogenesis of septic shock. TNF2, a polymorphism within the TNF-alpha gene promoter, has been associated with enhanced TNF-alpha production and negative outcome in some severe infections.

OBJECTIVES

To investigate the frequency of the TNF2 allele in patients with septic shock and to determine whether the allele is associated with the occurrence and outcome of septic shock.

DESIGN

Multicenter case-control study conducted from March 1996 to June 1997.

SETTING

Seven medical intensive care units in university hospitals.

SUBJECTS

Eighty-nine patients with septic shock and 87 healthy unrelated blood donors.

MAIN OUTCOME MEASURES

Frequency of the TNF2 allele among patients with septic shock and among those who died and the level of corresponding TNF-alpha concentrations.

RESULTS

Mortality among patients with septic shock was 54%, consistent with the predicted mortality from the Simplified Acute Physiologic Score (SAPS II) value. The polymorphism frequencies of the controls and the patients with septic shock differed only at the TNF2 allele (39% vs 18% in the septic shock and control groups, respectively, P =.002). Among the septic shock patients, TNF2 polymorphism frequency was significantly greater among those who had died (52% vs 24% in the survival group, P =.008). Concentrations of TNF-alpha were higher in 68% and 52% with the TNF2 and TNF1 polymorphisms, respectively, but their median values (48 pg/mL vs 29 pg/mL) were not statistically different (P = .31). After controlling for age and the probability of death, derived by the SAPS II score, multiple logistic regression analysis showed that, for the same rank of SAPS II value, patients with the TNF2 allele had a 3.7-fold risk of death (95% confidence interval, 1.37-10.24).

CONCLUSION

The TNF2 allele is strongly associated with susceptibility to septic shock and death due to septic shock.

Effects of epinephrine, norepinephrine, or the combination of norepinephrine and dobutamine on gastric mucosa in septic shock

OBJECTIVES

To compare in the same patient with septic shock, respective effects of epinephrine, norepinephrine, and the combination of norepinephrine and dobutamine (5 microg/kg/min) on systemic hemodynamic parameters and gastric mucosal perfusion using gastric tonometry and laser-Doppler flowmetry techniques.

DESIGN

Prospective, controlled, randomized, crossover study.

SETTING

University hospital intensive care unit.

PATIENTS

Twelve patients with septic shock.

INTERVENTIONS

Each patient received in a random succession epinephrine, norepinephrine, and norepinephrine plus dobutamine. Dosages of epinephrine and norepinephrine were adjusted to achieve a mean arterial pressure between 70 and 80 mm Hg. A laser-Doppler probe and a tonometer were introduced into the gastric lumen.

MEASUREMENTS AND MAIN RESULTS

The increase in gastric mucosal perfusion detected by laser-Doppler flowmetry was higher with epinephrine and the combination of norepinephrine and dobutamine than with norepinephrine alone (p < .05). In addition, the ratio of gastric mucosal perfusion (local oxygen delivery) to systemic oxygen delivery was increased after norepinephrine plus dobutamine as compared with norepinephrine alone and epinephrine (p< .05). Although values of intramucosal pH and gastroarterial PCO2 tended to be higher with norepinephrine plus dobutamine compared with those obtained with norepinephrine and epinephrine, differences were not statistically significant.

CONCLUSIONS

For the same mean arterial pressure in patients with septic shock, our study showed that administration of epinephrine increased gastric mucosal perfusion more than norepinephrine administration alone. Addition of dobutamine (5 microg/kg/ min) to norepinephrine improved gastric mucosal perfusion. This result could be explained by a vasodilating effect of dobutamine on gastric mucosal microcirculation.

Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP

In ventilated patients with acute lung injury (ALI) we investigated whether respiratory changes in arterial pulse pressure (DeltaPP) could be related to the effects of PEEP and fluid loading (FL) on cardiac index (CI). Measurements were performed before and after application of a PEEP (10 cm H2O) in 14 patients. When the PEEP-induced decrease in CI was > 10% (six patients), measurements were also performed after FL. Maximal (PPmax) and minimal (PPmin) values of pulse pressure were determined over one respiratory cycle and DeltaPP was calculated: DeltaPP (%) = 100 x ((PPmax - PPmin)/ ([PPmax + PPmin]/2)). PEEP decreased CI from 4.2 +/- 1.1 to 3.8 +/- 1.3 L/min/m2 (p < 0.01) and increased DeltaPP from 9 +/- 7 to 16 +/- 13% (p < 0.01). The PEEP-induced changes in CI correlated with DeltaPP on ZEEP (r = -0.91, p < 0.001) and with the PEEP-induced increase in DeltaPP (r = -0.79, p < 0.001). FL increased CI from 3.5 +/- 1.1 to 4.2 +/- 0.9 L/min/m2 (p < 0.05) and decreased DeltaPP from 27 +/- 13 to 14 +/- 9% (p < 0.05). The FL-induced changes in CI correlated with DeltaPP before FL (r = 0.97, p < 0.01) and with the FL-induced decrease in DeltaPP (r = -0.85, p < 0.05). In ventilated patients with ALI, DeltaPP may be useful in predicting and assessing the hemodynamic effects of PEEP and FL.

Hemodynamic effects of fluid loading in acute massive pulmonary embolism

OBJECTIVE

To assess the hemodynamic effects of fluid loading in patients with acute circulatory failure caused by acute massive pulmonary embolism (AMPE).

DESIGN

Prospective study.

SETTING

Respiratory critical care unit of a university hospital.

PATIENTS

Thirteen patients free of previous cardiopulmonary disease with angiographically proven AMPE (Miller index = 24 +/- 1), with acute circulatory failure defined by a cardiac index (CI) lower than 2.5 L/min/m2.

INTERVENTION

Infusion of 500 mL of dextran 40 over 20 mins.

MEASUREMENTS AND MAIN RESULTS

Fluid loading induced a substantial increase in right atrial pressure from 9 +/- 1 mm Hg to 17 +/- 1 mm Hg and in right ventricular end-diastolic volume index from 123 +/- 14 mL/m2 to 150 +/- 11 mL/m2 (p < .05 for both comparisons). The increase in right ventricular preload was associated with an increase in Cl from 1.6 +/- 0.1 to 2.0 +/- 0.1 L/min/m2 (p < .05), whereas right ventricular ejection fraction (15 +/- 3% at baseline vs. 16 +/- 3% after fluid loading) and total pulmonary vascular resistance index (1689 +/- 187 dyne x sec/cm5 x m2 at baseline vs. 1492 +/- 166 dyne x sec/ cm5 x m2 after fluid loading) remained unchanged. The increase in Cl induced by fluid loading was inversely correlated to baseline right ventricular end-diastolic volume index (r = -.89 ; p< .05).

CONCLUSIONS

These results suggest that fluid loading can improve hemodynamic status in patients with acute circulatory failure caused by AMPE.

Effects of catecholamines on the pulmonary venous bed in sheep

OBJECTIVE

To assess the effects of various catecholaminergic agents on pulmonary venous tone.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Physiology laboratory of a university hospital.

SUBJECTS

Thirty anesthetized, mechanically ventilated adult sheep.

INTERVENTIONS

Four groups of six animals received 1-hr infusions of norepinephrine (0.5 microg/kg/min), epinephrine (0.5 microg/kg/ min), dopamine (10 microg/kg/min), or dobutamine (10 microg/kg/min).

MEASUREMENTS AND MAIN RESULTS

A 7-Fr pulmonary artery catheter was placed in a proximal location to measure cardiac output and pressure in a large pulmonary vein (Ppw) after balloon inflation. Another catheter wedged in a small pulmonary artery measured pressure in a small pulmonary vein (Pdw). A third catheter measured left atrial pressure (PLA ). This method was able to detect the pulmonary venoconstrictive effects of histamine in a separate group of six animals. Pdw-PLA increased from a mean of 2.0+/-1.7 to 3.0+/-1.5 (SD) cm H2O (p < .01), 2.3+/-1.6 to 4.4+/-1.3 cm H2O (p < .01), and 1.7+/-1.0 to 3.5+/-2.2 cm H2O (p < .05) with norepinephrine, epinephrine, and dopamine, respectively. All of these drugs increased Pdw-Ppw, but only norepinephrine and epinephrine increased Ppw-PLA . No change in either pressure difference was observed with dobutamine. Elevation of cardiac output alone could not account for these findings since the increase in cardiac output induced by fluid infusion did not change the pressure differences.

CONCLUSION

Norepinephrine, epinephrine, and dopamine at doses commonly used in humans increase pulmonary venous tone in sheep.

Value of the venous-arterial PCO2 gradient to reflect the oxygen supply to demand in humans: effects of dobutamine

OBJECTIVE

To test the value of venous-arterial PCO2 gradient (deltaPCO2) measurements to reflect the adequacy of cardiac index (CI) to oxygen demand in patients submitted to rapid changes of CI and oxygen demand.

DESIGN

Prospective, comparative study.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

Ten patients with congestive heart failure exhibiting low baseline CI (< or =2.5 L/min/m2) but no evidence of global tissue hypoxia, as attested by the absence of clinical signs of shock and by normal blood lactate concentrations.

INTERVENTIONS

Infusion of incremental doses of dobutamine: 0 (D0), 5 (D5), 10 (D10), and 15 (D15) microg/kg/min.

MEASUREMENTS AND MAIN RESULTS

The CI increased by a linear fashion from D0 (1.6+/-0.1 L/min/m2) to D15 (2.4+/-0.2 L/min/m2) (p< .05). The mixed venous oxygen saturation (SVO2) increased from D0 (49+/-2%) to D10 (61+/-2%) (p < .05) and remained unchanged from D10 to D15 (60+/-2%). The oxygen extraction ratio (O2 ER) and the deltaPCO2 decreased from D0 (48+/-2% and 9+/-1 torr [1.2+/-0.3 kPa], respectively) to D10 (36+/-2% and 5+/-1 torr [0.7+/-0.1 kPa], respectively) (p < .05 for both comparisons) and remained unchanged from D10 to D15 (36+/-2% and 6+/-1 torr [0.8+/-0.1 kPa], respectively). The biphasic courses of SVO2, O2 ER, and deltaPCO2 were related to the course of oxygen consumption that remained constant from D0 (113+/-9 mL/min/m2) to D10 (112+/-8 mL/min/m2) and significantly increased from D10 to D15 (127+/-10 mL/min/m2) (p <.05).

CONCLUSIONS

deltaPCO2 can be reliably used at the bedside for informing on the adequacy of CI with respect to a given metabolic condition, and particularly for detecting changes in oxygen demand (e.g., the changes accompanying drug-induced changes in CI). In this regard, deltaPCO2, together with O2 ER and SVO2, can help to assess the adequacy of CI to global oxygen demand.

Relation between dicrotic notch and mean pulmonary artery pressure studied by using a Swan-Ganz catheter in critically ill patients

OBJECTIVE

It has been recently shown that there is a match between dicrotic notch and mean pulmonary artery (PA) pressures in spontaneously breathing patients studied by means of high-fidelity pressure catheters. The aim of the study was to analyze the relation between mean PA pressure and PA pressure at the incisura by using a Swan-Ganz catheter in critically ill, mechanically ventilated patients.

MEASUREMENTS AND RESULTS

Fluid-filled PA pressures were obtained over four ventilatory cycles in 32 consecutive, mechanically ventilated patients in the intensive care unit. We measured mean PA pressure and dicrotic notch pressure. We also calculated the widely used approximation of mean PA pressure (mean PAPapprox = diastolic + 1/3 pulse pressure). Cardiac output was measured in triplicate by using the thermodilution technique. Dicrotic notch was clearly identified in 30 of 32 patients. Mean PA pressure (32.1 +/- 10.2 mm Hg) and PA dicrotic notch pressure (31.8 +/- 10.4 mm Hg) were linearly related (r = 0.989, p < 0.001). Agreement between dicrotic notch and mean PA pressures was suggested (mean difference +/- SD = -0.3 +/- 1.5 mm Hg). Similar agreement was found between mean PAPapprox and mean PA pressure (mean difference +/- SD = -0.7 +/- 0.8 mm Hg; p = 0.20).

CONCLUSION

By using a Swan-Ganz catheter we found that dicrotic notch pressure equalled mean PA pressure in the critically ill, mechanically ventilated patients studied. This indicated that right-sided ejection was completed at a PA pressure equal to mean PA pressure in these patients.

Inverse ratio ventilation (I/E = 2/1) in acute respiratory distress syndrome: a six-hour controlled study

To assess the cardiorespiratory effects of a prolonged application of inverse ratio ventilation (IRV), we compared IRV (I/E = 2) with conventional ventilation (CV) (I/E = 0.5), applied for 6 h each in a randomized order, with constant tidal volume (VT) and total positive end-expiratory pressure (PEEP(tot)) in eight patients with acute respiratory distress syndrome (ARDS). After 1 h, IRV resulted in a lower peak inspiratory pressure (PIP) (28.2 +/- 1.5 versus 35.6 +/- 1.7 cm H2O, p < 0.05), an unchanged plateau pressure, and a higher mean airway pressure (MAP) (17.8 +/- 0.8 versus 15.6 +/- 0.5 cm H2O, p < 0.05) than CV. No significant difference in Pa(O2) and shunt fraction (QS/QT) was observed (83 +/- 7 mm Hg and 40 +/- 4% in CV versus 92 +/- 14 mm Hg and 35 +/- 3% in IRV, respectively). The Pa(CO2) was lower in IRV (48 +/- 3 versus 55 +/- 5 mm Hg, p < 0.05). Cardiac index (CI) and oxygen delivery (D(O2)) were lower in IRV (3.7 +/- 0.4 L/min/m2 and 500 +/- 61 ml/min/m2 versus 4.6 +/- 0.5 L/min/m2 and 617 +/- 80 ml/min/m2, respectively, p = 0.05 for both). Regardless of the considered parameter, no significant difference was observed between results after 1, 2, 4, and 6 h in each mode. We conclude that IRV at a ratio that results in a significant intrinsic PEEP does not improve Pa(O2), enhances CO2 elimination, decreases cardiac output (CO), and does not exert any time-dependent effect.

Elastic energy as an index of right ventricular filling

BACKGROUND

Right ventricle (RV) preload assessment remains controversial because the complexity of RV geometry is an obstacle to wall stress modeling. We developed a method to evaluate end-diastolic RV elastic energy (EL), a variable that integrates all the stretching effects of venous return and that can be easily estimated at the bedside from the area under the diastolic RV pressure-volume curve. The purpose of this study was to compare the clinical utility of EL and of the two conventional variables used to assess RV filling, ie, right atrial pressure (Pra) and RV end-diastolic volume (EDV).

METHOD

We studied 26 postoperative patients who required a rapid fluid challenge. Energetics were evaluated by constructing the RV pressure-volume loop at the bedside using right heart catheterization with RV ejection fraction (EF) derivation. Correlations between RV filling and RV performance (ejection and mechanical efficiency) were studied. RV filling indexes were Pra, EDV, and EL. Indexes of RV ejection were stroke volume (SV), RV stroke work (RVSW), mechanical energy expenditure during ejection (EM), and total energy expenditure of contraction (ET). Indexes of RV mechanical efficiency were EF and the EM/ET ratio.

RESULTS

Three important results were obtained. First, among RV ejection indexes, those that correlated best with RV filling indexes were EM and ET. Second, we found significant linear relationships between improved RV filling, as assessed by changes in EDV and EL, and improved RV ejection, as assessed by changes in SV, RVSW, EM, or ET. Third, changes in EDV and EL also predicted improved mechanical efficiency, as assessed by changes in EF and EM/ET. In, all situations, changes in EL yielded the strongest correlations.

CONCLUSIONS

Derivation of EL is simple and appears to be the best clinical means of assessing Starling's law of the heart for the RV.

[Hemodynamic management of septic shock. From a global approach to a gastrointestinal approach]

Oxygen uptake and increased metabolic requirements are characteristic of the acute state resulting from septic shock. One therapeutic approach to improving hemodynamics is to increase oxygen delivery in an attempt to overcome tissue oxygen debt. Recent randomized trials have suggested that systematically increasing oxygen supply is not necessarily the ideal strategy. It might be better, for each patient, to reach an optimal oxygen supply. This requires identification of parameters capable of indicating the optimal level, a rather difficult task. Currently, focus has been placed on the importance of the splanchnic circulation in severe septic shock. Hypoxia resulting from hypoperfusion of the intestinal mucosa occurs early in sepsis and could, via intermediary bacterial and/or endotoxinic translocation, maintain the septic syndrome and favor development of multiple organ failure. Since the drugs used to restore hemodynamics have vasoactive properties, measuring their effect on relevant indicators of splanchnic perfusion and oxygenation such as PCO2 or pH within the gastric mucosa using tonometric gastric probes might be a means of determining optimal oxygen level. With this approach, it would be possible to avoid sacrifying the perfusion of the gastrointestinal mucosa by using drugs which appear to favor the microcirculation in this territory.

Global energetic failure in brain-dead patients

The objective of this prospective, clinical study of consecutive patients was to test the hypothesis of a global energetic failure in brain-dead patients by analyzing indices of peripheral oxygenation during brain-dead resuscitation. Subjects comprised 24 subjects with brain death criteria from a multidisciplinary intensive care unit. The causes of brain death were multiple: severe traumatic head injury, cerebrovascular event, cerebral anoxia, primary brain tumor, and gunshot wound to the head. Interventions used were radial and pulmonary artery catheterization. Hemodynamic and gasometric parameters and blood lactate levels were measured immediately after the diagnosis of brain death (T0) and 4 hr later (T4), while patients were receiving a therapeutic protocol (fluids, vasopressive drugs) adjusted to reach a mean arterial pressure of 75 mmHg. In 18 of our 24 patients, a blood lactate level > or = 2 mmol/L (mean +/- SD: 4 +/- 2 mmol/L) associated with an increased mean lactate to pyruvate ratio (14.4 +/- 3.2) was observed at T0, while oxygen delivery (DO2) was high (533 +/- 208 ml/min/m2) and mean arterial pressure was 76 +/- 21 mmHg. Patients were subdivided into two groups according to changes in DO2 from T0 to T4: group D comprised 14 patients (10 with hyperlactatemia and 4 with normal lactate) in whom DO2 and oxygen consumption (VO2) simultaneously decreased from T0 to T4 without significant change in lactate level; group I comprised 10 patients (8 with hyperlactatemia and 2 with normal lactate) in whom DO2 and VO2 simultaneously increased, while the blood lactate level decreased significantly from 3.5 +/- 2.5 mmol/L at T0 to 2.1 +/- 1.0 mmol/L at T4 (P < 0.05). Our results indicate that the brain-dead state was frequently associated with a global energetic failure probably due to a cellular oxygen deficit, despite blood pressure within the normal range. This energetic failure, because it is associated with high levels of DO2, could result from a defect in peripheral oxygen extraction. Aggressive therapy, achieved by producing a further increase in DO2, may reduce this global tissue oxygen deficit.

Spontaneous pneumothorax. Comparison of thoracic drainage vs immediate or delayed needle aspiration

In the first part of this study, 61 patients admitted for the first episode or the first recurrence of a spontaneous pneumothorax (SP) were randomly treated with thoracic drainage (TD; 28 patients) or with simple needle aspiration (NA; 33 patients). Success rate of therapy was significantly higher with TD than with NA (93%, CI 84 to 100 vs 67%, CI 51 to 83; p = 0.01). Hospital stay was similar between the two groups (7 +/- 4.6 vs 7 +/- 5.6 days), mainly because NA was delayed by 72 h in 26 patients. Recurrence rates at 3 months were 29% (CI 11 to 47%) after TD, and 14% (CI 0 to 29%) after NA (p > 0.20, NS). In the second part of the study, an additional population of 35 patients was treated by immediate NA, with a success rate of 68.5% (CI 53.5 to 83.5%), and a recurrence rate at 3 months of 30% (CI 10 to 50%). Taken together, our results indicate that NA may be proposed as a first-line treatment of SP, with a successful result in two thirds of patients and recurrence in one fifth of patients. In patients who do not heal with NA, a combined risk of TD failure and short-term recurrence of 50% may be an incentive for undelayed surgical procedures.

Left ventricular function during weaning of patients with chronic obstructive pulmonary disease

OBJECTIVE

Determine the evolution of left ventricular ejection fraction during weaning.

DESIGN

Prospective study.

SETTING

Intensive care unit of a university teaching hospital.

PATIENTS AND PARTICIPANTS

12 consecutive mechanically ventilated patients, without documented coronary artery disease, suffering from acute exacerbation of chronic obstructive pulmonary disease and able to be weaned.

MEASUREMENTS AND RESULTS

Left ventricular ejection fraction was determined during mechanical ventilation, inspiratory pressure support (10 cmH2O) and spontaneous ventilation with constant inspiratory oxygen fraction using technetium 99m radionuclide angiography. Spontaneous ventilation induced a significant decrease in left ventricular ejection fraction from 54.5 +/- 12.4 to 47.0 +/- 13% (p < 0.01). Inspiratory pressure support induced a slight but non-significant decrease in left ventricular ejection fraction from 55.0 +/- 12.1 to 50.3 +/- 12.4%. Left ventricular ejection fraction was homogeneously reduced by spontaneous ventilation without patent regional wall motion abnormalities of the left ventricle. Myocardial 201thallium imaging performed 15 min after weaning showed a normal perfusion in the left ventricle anterior and posterior free wall.

CONCLUSION

Weaning of patients suffering from chronic obstructive pulmonary disease without coronary artery disease induced a significant reduction in left ventricular ejection fraction. The non significant decrease in left ventricular ejection fraction observed with inspiratory pressure support suggested that our results might be explained by a weaning induced increase in afterload.

Cardiorespiratory effects of pressure-controlled ventilation with and without inverse ratio in the adult respiratory distress syndrome

To assess the cardiorespiratory effects of pressure-controlled ventilation (PCV) and pressure-controlled inverse ratio ventilation (PC-IRV), we compared pressure-controlled ventilation with an inspiratory-to-expiratory time ratio (I/E) of 1/2 (PCV) and of 2/1 (PC-IRV) to volume-controlled ventilation (VCV) with an I/E of 1/2 in 10 patients suffering from the adult respiratory distress syndrome. In all modes, the inspiratory oxygen fraction, tidal volume, respiratory rate, and total positive end-expiratory pressure (PEEPt = applied PEEP + intrinsic PEEP) were kept constant. Each ventilatory mode was applied for 1 h in a randomized order. No significant differences in PaO2 were observed among the three modes. The PaCO2 was lower (p < 0.05) in PC-IRV (39 +/- 4 mm Hg) than in PCV (43 +/- 5 mm Hg) and in VCV (45 +/- 5 mm Hg). The peak airway pressure was significantly lower in PC-IRV than in PCV (p < 0.05) and in PCV than in VCV (p < 0.05), but plateau pressure was not different in the 3 modes. The mean airway pressure (mPaw) was significantly higher (p < 0.05) in PC-IRV (21.4 +/- 0.7 cm H2O) than in PCV (17.1 +/- 0.7 cm H2O) and VCV (16.4 +/- 0.5 cm H2O). As a consequence of this increased mPaw, PC-IRV induced a decrease in cardiac index (CI) (3.3 +/- 0.2 vs 3.7 +/- 0.2 L/min/m2 in VCV; p < 0.05) and hence in oxygen delivery (DO2) (424 +/- 28 vs 469 +/- 38 ml/min/m2 in VCV; p < 0.05). Our results suggest that neither PCV nor PC-IRV bring any benefit over VCV in terms of arterial oxygenation. Moreover, the increase in mPaw induced by PC-IRV may be deleterious to the CI and DO2.

Arterial hemodynamics and cardiac effects of enoximone, dobutamine, and their combination in severe heart failure

The acute systemic and regional hemodynamic effects of dobutamine (5, 10, and 15 micrograms/kg/min intravenously), of enoximone (1, 1.5, and 2 mg/kg intravenously), and of the dobutamine-enoximone combination were compared in eight patients with severe congestive heart failure. Dobutamine and enoximone similarly and dose-dependently increased cardiac index and decreased systemic vascular resistance, right atrial pressure, and mean capillary wedge pressure. Dobutamine, but not enoximone, increased heart rate after 10 and 15 micrograms/kg/min. The combination of the two drugs caused a greater increase in cardiac index and a greater decrease in total peripheral resistance than did each drug alone. In the forearm vascular bed, brachial blood flow and brachial artery diameter were increased by enoximone significantly and dose-dependently and by dobutamine only at 5 micrograms/kg/min. Finally, the combination of the two drugs increased brachial blood flow but not brachial artery diameter to a larger extent than enoximone alone. Hepatosplanchnic and renal blood flows were not altered by any of the treatments. These results indicate that (1) enoximone exerts a significantly greater muscular vasodilator action than dobutamine; (2) the dobutamine-enoximone combination potentiates the systemic and brachial vasodilator effects of each drug; and (3) high doses of dobutamine (10 and 15 micrograms/kg/min) improve hemodynamics through their positive inotropic and chronotropic effects, whereas at low doses (5 micrograms/kg/min) a peripheral vasodilation also contributes.

Cardiac index vs oxygen-derived parameters for rational use of dobutamine in patients with congestive heart failure

In patients with congestive heart failure (CHF), catecholaminergic agents may exert thermogenic effects that limit their beneficial effects in terms of global tissue oxygenation. Oxygen extraction ratio (O2ER) or mixed venous blood saturation (SvO2) might take into account better than cardiac index (CI) the resultant effect of such agents on peripheral oxygenation. We tested this hypothesis in a series of 20 patients with severe CHF and normal blood lactate levels undergoing pulmonary artery catheterization and receiving incremental doses of dobutamine: 0 (Do), 5 (D5), 10 (D10), and 15 micrograms/kg/min (D15). A significant dose-effect relationship (p < 0.01) was found between dose of dobutamine and CI (CI = 0.06 dose + 1.82). By contrast, no dose-effect relationship was observed between dobutamine dose and either O2ER or SvO2. Indeed, a biphasic profile was observed for O2ER and SvO2. From D0 to D10, O2ER decreased (from 45 +/- 6 to 35 +/- 7 percent) and SvO2 increased (from 52 +/- 7 to 62 +/- 7 percent). From D10 to D15, no further change was observed for both parameters. This latter finding was related to a significant increase in VO2 at D15 (p < 0.01). In these normolactatemic patients with unchanged VO2 from D0 to D10 while DO2 linearly increased (from D0 to D15), the increase in VO2 at D15 was probably due to an increase in oxygen demand induced by the drug. Our results suggest that dobutamine at a dose of 15 micrograms/kg/min can induce an increase in O2 demand that might offset the improvement in CI. Thus, in patients with CHF, oxygen-derived parameters such as O2ER and SvO2 should be more appropriate than CI to assess the efficacy of dobutamine.

Effects of cardiovascular drugs on oxygen consumption/oxygen delivery relationship in patients with congestive heart failure

The oxygen consumption (VO2)/oxygen delivery (DO2) relationship was analyzed in ten patients with severe congestive heart failure (CHF) and normal blood lactate levels. First dobutamine and then enoximone, after a washout period, were administered to each patient to increase cardiac output by at least 15 percent. Similar increases in DO2 were obtained with both drugs: from 285 +/- 46 to 393 +/- 87 ml/min/m2 for dobutamine, and from 285 +/- 54 to 392 +/- 99 ml/min/m2 for enoximone. However, while VO2 did not change (132 +/- 24 vs 132 +/- 21 ml/min/m2) (VO2/DO2 independency) with a dobutamine infusion (mean dose of 10 +/- 2 micrograms/kg/min), a significant increase in VO2 from 134 +/- 22 to 157 +/- 21 ml/min/m2 was observed with a bolus infusion of enoximone (mean dose of 1.7 +/- 0.5 mg/kg). These results, observed in patients with CHF without patent oxygen debt, suggest that an artefactual VO2/DO2 dependency might be induced by the cardiovascular drug used to elevate DO2, probably because of a drug-induced oxygen demand increase.

Bedside evaluation of the resistance of large and medium pulmonary veins in various lung diseases

To evaluate the contribution of large and medium pulmonary veins to the total pulmonary vascular resistance in various human lung diseases, we compared in 64 patients the pulmonary arterial proximal wedge pressure (Ppw), obtained when the balloon of a 7F pulmonary artery catheter was inflated with 1.5 ml air, with the distal wedge pressure (Pdw), obtained after the tip of the catheter was advanced until wedged in a small artery without balloon inflation. Ppw, reflecting the pressure in a large pulmonary vein, approximates the left atrial pressure, whereas Pdw reflects the pressure in a smaller pulmonary vein. Pdw was greater than Ppw in all 64 patients. The Pdw-Ppw gradient was 1.1 +/- 0.5 mmHg in nine patients with normal lungs and was significantly higher in 13 patients with chronic congestive heart failure (3.8 +/- 0.8 mmHg, P less than 0.01) and in 22 patients with adult respiratory distress syndrome (3.8 +/- 0.8 mmHg; P less than 0.01), but not in 20 patients with chronic obstructive pulmonary disease (1.8 +/- 0.7 mmHg). The distribution of the pulmonary vascular resistance was clearly different among the four groups. The fraction of the total pulmonary vascular resistance attributable to large and medium pulmonary veins was significantly increased (P less than 0.01) in adult respiratory distress syndrome (27.5 +/- 12%) and cardiac patients (27.5 +/- 9%) compared with patients with chronic obstructive pulmonary disease (13 +/- 5%) and normal lungs (13.5 +/- 6%).(ABSTRACT TRUNCATED AT 250 WORDS)