Pressure-volume curves with and without muscle paralysis in acute respiratory distress syndrome.

OBJECTIVE: Pressure-volume (PV) curves are recorded after induction of complete muscle paralysis, which may limit their clinical use. The feasibility of recording PV curves without paralysis has not been tested. In 19 patients with acute respiratory distress syndrome (ARDS) and no hemodynamic instability we prospectively evaluated whether PV curves can be safely and reliably recorded under deep sedation without neuromuscular blockade. METHODS: After standardized sedation (continuous infusion of midazolam and fentanyl) PV curves were recorded during apneic sedation, defined as absence of respiratory effort during a 6-s expiratory pause and during paralysis induced by cis-atracurium. MEASUREMENTS AND RESULTS: Agreement between PV curve parameters in the two conditions was evaluated. Curves were obtained from 10 cmH2O and from zero end-expiratory pressure in all patients under apneic sedation. In five patients propofol was given in addition to midazolam and fentanyl, and in two of them fluid resuscitation was needed. A strong agreement was found for respiratory system compliance and the lower inflection point and for chest wall compliance in the five patients whose esophageal pressure was measured. The variability of the measurements, however, should be taken into account in clinical practice. CONCLUSION: Neuromuscular blockade can be dispensed with when recording PV curves in many ARDS patients. Reliable PV curves can be obtained under anesthesia alone, with no serious adverse effects.

Relationship between pressure-volume curve and markers for collagen turn-over in early acute respiratory distress syndrome.

OBJECTIVE: In acute respiratory distress syndrome, the relationships between changes in the elastic behavior of the respiratory system and biological markers of extra-cellular matrix or surfactant turn-over could give some insights into its pathophysiological determinants. DESIGN AND MEASUREMENTS: In 17 patients with acute respiratory distress syndrome, we assessed the relationship between chord compliance measured on pressure-volume curves obtained at two levels of positive end-expiratory pressure (0 and 10[Symbol: see text]cm[Symbol: see text]H(2)O) and biological markers of collagen turn-over or surfactant degradation in bronchoalveolar lavage fluid obtained simultaneously in the early phase of the disease (first 4 days). MAIN RESULTS: The compliance of the respiratory system obtained from the pressure-volume curves was significantly correlated with markers for collagen turn-over (type III procollagen peptide and matrix metalloproteinase 2) and with markers of surfactant degradation (type-IIA secretory phospholipase A2). The correlations were stronger when the curve was traced from positive end-expiratory pressure, suggesting that this condition may improve the assessment of tissue mechanics. A logarithmic relationship best described the correlation between compliance and type III procollagen peptide, in agreement with a collagen-dependent model of maximal distension. The marker for surfactant degradation was associated with ongoing alveolar inflammation (cellularity of bronchoalveolar lavage fluid and tumor necrosis factor-alpha concentration). Interleukin-10, an anti-inflammatory mediator, showed no correlation with compliance. CONCLUSION: These preliminary data suggest that a severe reduction in compliance in the early phase of acute respiratory distress syndrome is associated with both collagen deposition and surfactant degradation.

Ventilator-associated pneumonia leading to acute lung injury after trauma: importance of Haemophilus influenzae.

BACKGROUND: Ventilator-associated pneumonia is a clear risk factor for acute lung injury which has been poorly described in trauma patients. This prospective study was undertaken to estimate the incidence of such ventilator-associated pneumonia leading to acute lung injury, the risk factors, and the associated morbidity and mortality in a group of multiple trauma patients. METHODS: Trauma patients who were mechanically ventilated and survived at least 24 h were included. Ventilator-associated pneumonia was confirmed by a bacterial culture of a blind protected telescoping catheter with at least 10 colony-forming units/ml of at least one pathogen. Episodes of acute lung injury were prospectively recorded. RESULTS: Ventilator-associated pneumonia was documented in 78 patients of the 175 included (44%) and led to the development of ventilator-associated pneumonia acute lung injury in 18 patients (23%). The sole independent risk factor for ventilator-associated pneumonia leading to acute lung injury was the presence of Haemophilus influenzae (hazard ratio, 8.8; 95% confidence interval, 2.7-28.6). Eleven (61%) of the 18 patients with ventilator-associated pneumonia leading to acute lung injury had development of a ventilator-associated pneumonia recurrence, as compared with 20 (33%) of the 60 patients with ventilator-associated pneumonia alone (P = 0.03). Seven (39%) of the 18 trauma patients with ventilator-associated pneumonia leading to acute lung injury died, as compared with 9 (15%) of the 60 trauma patients with ventilator-associated pneumonia alone (P = 0.04). CONCLUSION: Acute lung injury complicated the course of 15% of ventilator-associated pneumonia in trauma patients. H. influenzae seemed to be one of the most frequent bacteria involved and the sole risk factor identified. Occurrence of ventilator-associated pneumonia leading to acute lung injury modified the prognosis of trauma patients.

Hemodynamic effects of portal triad clamping with and without pneumoperitoneum: an echocardiographic study.

The decrease of cardiac index observed during portal triad clamping (PTC) with and without pneumoperitoneum has been studied only with right heart catheterization. To better understand this decrease of cardiac index, we investigated the balance between the adequacy of preload and the ability of the heart to pump against an increased afterload, by using transesophageal echocardiography. Ten patients with PTC performed during laparoscopy and 10 with PTC performed during laparotomy were studied. Five minutes after PTC, the stroke volume, the left ventricular (LV) fractional area change (FAC), and the LV end-systolic wall stress (LVESWS) were measured as the conventional hemodynamic variables. Regional wall motion abnormalities (RWMA) were also recorded. In the laparotomy group, LV end-diastolic area decreased, and LVESWS did not increase significantly. FAC remained stable, and one patient developed RWMA. In the laparoscopic group, LV end-diastolic area remained stable, and LVESWS increased. FAC decreased significantly, and five patients developed RWMA. A decrease in preload was the main important change in the laparotomy group, and in the laparoscopic group a decrease in LV function was demonstrated that was likely a consequence of decreased LV preload and increased LV afterload. However, these did not necessitate stopping the procedure or releasing PTC in these study patients without cardiac disease.

Comparative effect of intraoperative propacetamol versus placebo on morphine consumption after elective reduction mammoplasty under remifentanil-based anesthesia: a randomized control trial [ISRCTN71723173].

BACKGROUND: Postoperative administration of paracetamol or its prodrug propacetamol has been shown to decrease pain with a morphine sparing effect. However, the effect of propacetamol administered intra-operatively on post-operative pain and early postoperative morphine consumption has not been clearly evaluated. In order to evaluate the effectiveness of analgesic protocols in the management of post-operative pain, a standardized anesthesia protocol without long-acting opioids is crucial. Thus, for ethical reasons, the surgical procedure under general anesthesia with remifentanil as the only intraoperative analgesic must be associated with a moderate predictable postoperative pain. METHODS: We were interested in determining the postoperative effect of propacetamol administered intraoperatively after intraoperative remifentanil. Thirty-six adult women undergoing mammoplasty with remifentanil-based anesthesia were randomly assigned to receive propacetamol 2 g or placebo one hour before the end of surgery. After remifentanil interruption and tracheal extubation in recovery room, pain was assessed and intravenous titrated morphine was given. The primary end-point was the cumulative dose of morphine administered in the recovery room. The secondary end-points were the pain score after tracheal extubation and one hour after, the delay for obtaining a Simplified Numerical Pain Scale (SNPS) less than 4, and the incidence of morphine side effects in the recovery room.For intergroup comparisons, categorical variables were compared using the chi-squared test and continuous variables were compared using the Student t test or Mann-Whitney U test, as appropriate. A p value less than 0.05 was considered as significant. RESULTS: In recovery room, morphine consumption was lower in the propacetamol group than in the placebo group (p = 0.01). Pain scores were similar in both groups after tracheal extubation and lower in the propacetamol group (p = 0.003) one hour after tracheal extubation. The time to reach a SNPS < 4 was significantly shorter in the propacetamol group (p = 0.02). The incidence of morphine related side effects did not differ between the two groups. CONCLUSIONS: Intraoperative propacetamol administration with remifentanil based-anesthesia improved significantly early postoperative pain by sparing morphine and shortening the delay to achieve pain relief.

Effects of positive end-expiratory pressure and body position on pulmonary blood flow redistribution in mechanically ventilated normal pigs.

STUDY OBJECTIVES: To assess the respective effects of position and positive end-expiratory pressure (PEEP) on the distribution of regional pulmonary blood flow (PBF). DESIGN: Prospective randomized animal study. SETTING: Animal research facility in a university hospital. PARTICIPANTS: Normal pigs that were tracheostomized, anesthetized, and mechanically ventilated. INTERVENTIONS: PBF was measured in seven pigs in the supine position (SP) and the prone position (PP) at both zero end-expiratory pressure (ZEEP) and 10 cm H(2)O of PEEP. The regional PBF was assessed by the radioactive microsphere method. The lungs from each pig were sliced into 90 samples. The heterogeneity of PBF was estimated from its coefficient of variation. MEASUREMENTS AND RESULTS: The lung samples had a mean (+/- SD) weight of 1.60 +/- 0.39 g. Changing position from SP to PP at ZEEP redistributed PBF toward the anterior, superior, and peripheral regions and did not significantly reduce the coefficient of variation for regional PBF (reduction, 44.7 +/- 7% to 42.2 +/- 8%). Changing from the SP to PP position at PEEP induced a similar, but more marked, redistribution of PBF and a significant reduction in the coefficient of variation from 53 +/- 13% to 30.4 +/- 7% (p < 0.001). In the SP, PEEP redistributed PBF toward the posterior, inferior, and central regions without changing the heterogeneity of PBF. In the PP, PEEP had little effect on the PBF redistribution but significantly reduced the coefficient of variation of PBF from 42.2 +/- 8% to 30.4 +/- 7% (p < 0.05). CONCLUSIONS: Pigs in the PP had altered gravitational dependence of PBF compared to that observed when pigs were in the SP. This effect was enhanced by using a PEEP of 10 cm H(2)O.

Comparison of PET with radioactive microspheres to assess pulmonary blood flow.

UNLABELLED: Microsphere technique is the reference for assessment of pulmonary blood flow (PBF) but is destructive; PET, however, can determine PBF noninvasively. Comparisons of these 2 methods are scanty. Our study aimed at comparing these 2 techniques using a mathematic model taking into account the right ventricle in determining the transit time of a tracer through lung tissue. METHODS: Ten normal pigs were investigated at baseline, during dobutamine infusion, and during 10 cm H(2)O of positive end-expiratory pressure. Under each condition, PBF was successively measured with PET (PET-PBF) and radioactive microspheres (MS-PBF). For PET-PBF, 2 mCi (74 MBq) (15)O-labeled water were injected intravenously over 20 s and PET scanning was performed for 10 min. The input function was determined noninvasively from PET and invasively from mixed venous blood withdrawals. PET-PBF was computed using a mathematic model taking into account the right ventricle in determining the transit time of the tracer through lung tissue. For MS-PBF, 1 given isotope was injected under a given condition. PET-PBF and MS-PBF for 5 lung regions were compared. RESULTS: PET-PBF significantly correlated with MS-PBF both over all experimental points (PET-PBF = 0.79. MS-PBF + 1,538; r = 0.79; P < 0.001) and in separate lung regions. Invasive and noninvasive input functions also correlated significantly (r = 0.90; P < 0.001). Simulations stressed the crucial role of the right ventricle to the transit time of tracer through lung tissue in the determination of PET-PBF. CONCLUSION: PBF can accurately be assessed using PET and a mathematic model taking into account the right ventricle in determining the transit time of a tracer through lung tissue. Noninvasive determination of the input function of the right ventricle is accurate and can readily be used for clinical applications.