Computed tomography assessment of lung structure in patients undergoing cardiac surgery with cardiopulmonary bypass

Hypoxemia is a frequent complication after coronary artery bypass graft (CABG) with cardiopulmonary bypass (CPB), usually attributed to atelectasis. Using computed tomography (CT), we investigated postoperative pulmonary alterations and their impact on blood oxygenation. Eighteen non-hypoxemic patients (15 men and 3 women) with normal cardiac function scheduled for CABG under CPB were studied. Hemodynamic measurements and blood samples were obtained before surgery, after intubation, after CPB, at admission to the intensive care unit, and 12, 24, and 48 h after surgery. Pre- and postoperative volumetric thoracic CT scans were acquired under apnea conditions after a spontaneous expiration. Data were analyzed by the paired Student t-test and one-way repeated measures analysis of variance. Mean age was 63 ± 9 years. The PaO2/FiO2 ratio was significantly reduced after anesthesia induction, reaching its nadir after CPB and partially improving 12 h after surgery. Compared to preoperative CT, there was a 31% postoperative reduction in pulmonary gas volume (P < 0.001) while tissue volume increased by 19% (P < 0.001). Non-aerated lung increased by 253 ± 97 g (P < 0.001), from 3 to 27%, after surgery and poorly aerated lung by 72 ± 68 g (P < 0.001), from 24 to 27%, while normally aerated lung was reduced by 147 ± 119 g (P < 0.001), from 72 to 46%. No correlations (Pearson) were observed between PaO2/FiO2 ratio or shunt fraction at 24 h postoperatively and postoperative lung alterations. The data show that lung structure is profoundly modified after CABG with CPB. Taken together, multiple changes occurring in the lungs contribute to postoperative hypoxemia rather than atelectasis alone.

L-arginine reduces heart rate and improves hemodynamics in severe congestive heart failure

BACKGROUND

Stimulated endothelium-derived relaxing factor-mediated vasodilation and conduit artery distensibility are impaired in congestive heart failure (CHF). L-arginine could have a potentially beneficial role in CHF, acting through the nitric oxide (NO)-L-arginine pathway or by growth hormone increment.

HYPOTHESIS

This study was undertaken to investigate the effects of L-arginine on heart rate, hemodynamics, and left ventricular (LV) function in CHF.

METHODS

In seven patients (aged 39 +/- 8 years) with CHF, we obtained the following parameters using echocardiography and an LV Millar Mikro-Tip catheter simultaneously under four conditions: basal, during NO inhalation (40 ppm), in basal condition before L-arginine infusion, and after L-arginine intravenous infusion (mean dose 30.4 +/- 1.9 g).

RESULTS

Nitric oxide inhalation increased pulmonary capillary wedge pressure from 25 +/- 9 to 31 +/- 7 mmHg (p < 0.05), but did not change echocardiographic variables or LV contractility by elastance determination. L-arginine decreased heart rate (from 88 +/- 15 to 80 +/- 16 beats/min, p<0.005), mean systemic arterial pressure (from 84 +/- 17 to 70 +/- 18 mmHg, p < 0.007), and systemic vascular resistance (from 24 +/- 8 to 15 +/- 6 Wood units, p<0.003). L-arginine increased right atrial pressure (from 7 +/- 2 to 10 +/- 3 mmHg, p<0.04), cardiac output (from 3.4 +/- 0.7 to 4.1 +/- 0.8 l/min, p < 0.009), and stroke volume (from 40 +/- 9 to 54 +/- 14 ml, p < 0.008). The ratios of pulmonary vascular resistance to systemic vascular resistance at baseline and during NO inhalation were 0.09 and 0.075, respectively, and with L-arginine this increased from 0.09 to 0.12.

CONCLUSION

L-arginine exerted no effect on contractility; however, by acting on systemic vascular resistance it improved cardiac performance. L-arginine showed a negative chronotropic effect. The possible beneficial effect of L-arginine on reversing endothelial dysfunction in CHF without changing LV contractility should be the subject of further investigations.

A micromethod for quantitation of debrisoquine and 4-hydroxydebrisoquine in urine by liquid chromatography

We describe a new simple, selective and sensitive micromethod based on HPLC and fluorescence detection to measure debrisoquine (D) and 4-hydroxydebrisoquine (4-OHD) in urine for the investigation of xenobiotic metabolism by debrisoquine hydroxylase (CYP2D6). Four hundred microl of urine was required for the analysis of D and 4-OHD. Peaks were eluted at 8.3 min (4-OHD), 14.0 min (D) and 16.6 min for the internal standard, metoprolol (20 microg/ml). The 5-microm CN-reverse-phase column (Shimpack, 250 x 4.6 mm) was eluted with a mobile phase consisting of 0.25 M acetate buffer, pH 5.0, and acetonitrile (9:1, v/v) at 0.7 ml/min with detection at lambdaexcitation = 210 nm and lambdaemission = 290 nm. The method, validated on the basis of measurements of spiked urine, presented 3 ng/ml (D) and 6 ng/ml (4-OHD) sensitivity, 390-6240 ng/ml (D) and 750-12000 ng/ml (4-OHD) linearity, and 5.7/8.2% (D) and 5.3/8.2% (4-OHD) intra/interassay precision. The method was validated using urine of a healthy Caucasian volunteer who received one 10-mg tablet of Declinax(R), po, in the morning after an overnight fast. Urine samples (diuresis of 4 or 6 h) were collected from zero to 24 h. The urinary excretion of D and 4-OHD, Fel (0-24 h), i.e., fraction of dose administered and excreted into urine, was 6.4% and 31.9%, respectively. The hydroxylation capacity index reported as metabolic ratio was 0.18 (D/4-OHD) for the person investigated and can be compared to reference limits of >12.5 for poor metabolizers (PM) and <12.5 for extensive metabolizers (EM). In parallel, the recovery ratio (RR), another hydroxylation capacity index, was 0.85 (4-OHD: SigmaD + 4-OHD) versus reference limits of RR <0.12 for PM and RR >0. 12 for EM. The healthy volunteer was considered to be an extensive metabolizer on the basis of the debrisoquine test.

Heart transplantation in neonates and children. Intermediate-term results

OBJECTIVE

To assess intermediate-term outcome in children who have undergone orthotopic heart transplantation.

METHODS

We carried out a longitudinal and prospective study between October '92 and June '99 comprising 20 patients with ages ranging from 12 days to 7 years (mean of 2.8 years). We employed a double immunosuppression protocol with cyclosporine and azathioprine and induction therapy with polyclonal antithymocyte serum. Survival and complications resulting from the immunosuppression protocol were analyzed.

RESULTS

The double immunosuppression protocol and the induction therapy with polyclonal antithymocyte serum resulted in an actuarial survival curve of 90% and 78.2% at 1 and 6 years, respectively, with a mean follow-up period of 3.6 years. One patient died due to acute rejection 40 days after transplantation; another patient died 2 years after transplantation due to lymphoproliferative disorder; a third patient died because of primary failure of the graft; and a fourth patient died due to bronchopneumonia. The major complications were as follows: acute rejection, infection, nephrotoxicity, and systemic hypertension. The means of rejection and infection episodes per patient were 2.9 and 3.4, respectively. After one year of transplantation, a slight reduction in the creatinine clearance and systemic hypertension were observed in 7 (38.9%) patients.

CONCLUSION

Heart transplantation made life possible for those patients with complex congenital heart diseases and cardiomyopathies in refractory congestive heart failure constituting a therapeutical option for this group of patients in the terminal phase.

The effects of positive end-expiratory pressure on respiratory system mechanics and hemodynamics in postoperative cardiac surgery patients

We prospectively evaluated the effects of positive end-expiratory pressure (PEEP) on the respiratory mechanical properties and hemodynamics of 10 postoperative adult cardiac patients undergoing mechanical ventilation while still anesthetized and paralyzed. The respiratory mechanics was evaluated by the inflation inspiratory occlusion method and hemodynamics by conventional methods. Each patient was randomized to a different level of PEEP (5, 10 and 15 cmH2O), while zero end-expiratory pressure (ZEEP) was established as control. PEEP of 15-min duration was applied at 20-min intervals. The frequency dependence of resistance and the viscoelastic properties and elastance of the respiratory system were evaluated together with hemodynamic and respiratory indexes. We observed a significant decrease in total airway resistance (13.12 +/- 0.79 cmH2O l-1 s-1 at ZEEP, 11.94 +/- 0.55 cmH2O l-1 s-1 (P<0.0197) at 5 cmH2O of PEEP, 11.42 +/- 0.71 cmH2O l-1 s-1 (P<0.0255) at 10 cmH2O of PEEP, and 10.32 +/- 0.57 cmH2O l-1 s-1 (P<0.0002) at 15 cmH2O of PEEP). The elastance (Ers; cmH2O/l) was not significantly modified by PEEP from zero (23.49 +/- 1.21) to 5 cmH2O (21.89 +/- 0.70). However, a significant decrease (P<0.0003) at 10 cmH2O PEEP (18.86 +/- 1.13), as well as (P<0.0001) at 15 cmH2O (18.41 +/- 0.82) was observed after PEEP application. Volume dependence of viscoelastic properties showed a slight but not significant tendency to increase with PEEP. The significant decreases in cardiac index (l min-1 m-2) due to PEEP increments (3.90 +/- 0.22 at ZEEP, 3.43 +/- 0.17 (P<0. 0260) at 5 cmH2O of PEEP, 3.31 +/- 0.22 (P<0.0260) at 10 cmH2O of PEEP, and 3.10 +/- 0.22 (P<0.0113) at 15 cmH2O of PEEP) were compensated for by an increase in arterial oxygen content owing to shunt fraction reduction (%) from 22.26 +/- 2.28 at ZEEP to 11.66 +/- 1.24 at PEEP of 15 cmH2O (P<0.0007). We conclude that increments in PEEP resulted in a reduction of both airway resistance and respiratory elastance. These results could reflect improvement in respiratory mechanics. However, due to possible hemodynamic instability, PEEP should be carefully applied to postoperative cardiac patients.

Thermal filament continuous thermodilution cardiac output delayed response limits its value during acute hemodynamic instability

BACKGROUND

It has been suggested that measurement of continuous cardiac output (CCO) is an advancement in the management of critically ill patients. Our objective was to determine the accuracy of CCO during the rapid hemodynamic changes induced by hemorrhage and resuscitation.

METHODS

In 12 anesthetized dogs (20.2+/-0.9 kg), pulmonary artery blood flow, our "gold standard" cardiac output, was measured with an sonographic flowprobe, whereas CCO, intermittent bolus cardiac output (ICO), and mixed venous oxygen saturation were measured with a thermodilution fiberoptic pulmonary artery catheter with a thermal filament. A graded hemorrhage (20 mL/min) was produced to a mean arterial pressure of 40 mm Hg, which was maintained at this level for 30 minutes. Total shed blood volume (701+/-53 mL) was retransfused at a rate of 40 mL/min, over 30 minutes, after which a massive hemorrhage (100 mL/min) was produced over 10 minutes.

RESULTS

Hemorrhage induced significant decreases in mean arterial pressure, mixed venous oxygen saturation, and oxygen delivery, which were all restored during early resuscitation. However, CCO showed a delayed response after hemorrhage and resuscitation, compared with pulmonary blood flow, throughout the study (r = 0.549), matching only at baseline and at the end of both graded hemorrhage and resuscitation periods. There was a good correlation between ICO and pulmonary artery blood flow (r = 0.964) and no significant differences between them throughout the study.

CONCLUSION

CCO has a delayed response during acute hemodynamic changes induced by hemorrhage and resuscitation. When sudden changes in mean arterial pressure or in mixed venous oxygen saturation are detected, cardiac output must be estimated by the standard bolus thermodilution technique, not by CCO.

[Hemodynamic evaluation and clinical outcome of children with severe dilated cardiomyopathy eligible for heart transplantation]

PURPOSE

To evaluate hemodynamic parameters and clinical outcome of children with severe cardiomyopathy who are candidates for heart transplantation.

METHODS

Twenty four children aged from 4 months to 10 years and 8 months (mean 3.7 +/- 2.5 years) from February 1992 to May 1996, were submitted to hemodynamic study and the following parameters were measured: cardiac output, mean pulmonary artery pressure (MPAP) and capillary wedge pressure. The pulmonary vascular resistance index (PVRI) and transpulmonary pressure gradient (TGP) were calculated.

RESULTS

Ten (41.6%) children were transplanted (group A), 5 (20.8%) are still waiting heart transplantation (group B) and 9 (37.6%) died (group C). The mean age of the B and C group were significantly different. The PVRI, MPAP and TPG were significant lower in group A than group C (p = 0.01; p = 0.044 and p = 0.023 respectively).

CONCLUSION

The profile of the hemodynamic parameters of children with severe dilated cardiomyopathy was compatible with the clinical findings. The age was the only difference comparing groups B and C. PVRI, MPAP and TPG were significant factors between group A and C. The older the patient, the worse was the prognosis.

Effects of inhaled nitric oxide on respiratory system mechanics, hemodynamics, and gas exchange after cardiac surgery

OBJECTIVE

To evaluate the hemodynamic and respiratory effects of inhaled nitric oxide (NO) in postoperative cardiac patients.

DESIGN

A prospective evaluation.

SETTING

A university hospital intensive care unit.

PARTICIPANTS

Fourteen adults with pulmonary hypertension, studied postoperatively.

INTERVENTIONS

60 minutes of NO inhalation (20 ppm).

MEASUREMENTS AND MAIN RESULTS

Respiratory mechanics were analyzed by inflating the relaxed respiratory system with constant flow, followed by rapid airway occlusion at end-inflation, which was maintained until a plateau in tracheal pressure was obtained. Gas exchange and hemodynamics were evaluated by conventional means. The data were studied using the analysis of variance for repeated measures. Minimum airway resistance (Rmin) increased significantly from 8.87+/-3.24 cm H2O/L x s to 9.69 +/-3.22 cm H2O/L x s at the end of NO inhalation and remained elevated after NO was discontinued. A selective vasodilator effect on pulmonary vasculature was observed in the pulmonary-systemic vascular resistance ratio, which decreased from 0.18+/-0.11 to 0.13+/-0.08 at the end of inhalation and returned to baseline values after gas suspension. No significant alterations in oxygenation were observed.

CONCLUSION

The effects of NO as a powerful and useful vasodilator agent were confirmed. However, it is important to be aware that the effects observed on respiratory mechanics may interfere with the final response of the respiratory system to NO.

Nitric oxide inhalation reduces pulmonary tidal volume during exercise in severe chronic heart failure

Multiple mechanisms have been proposed to explain the hyperventilation and the limited exercise capacity in congestive heart failure (CHF) including increased intrapulmonary pressures, total pulmonary resistance, and airway abnormalities. We investigated the hypothesis that inhalation of nitric oxide could influence the maximum exercise capacity and excessive ventilatory response to exercise in CHF. Fifteen patients in CHF (mean age 48 +/- 12 years) underwent a control and a nitric oxide inhalation progressive treadmill exercise test with 30 ppm. We determined the maximum oxygen consumptiom (peak VO2), CO2 production (VCO2), minute pulmonary ventilation (VE), respiratory rate, tidal volume (VT), ventilatory equivalent for oxygen (VE/VO2), ventilatory equivalent for carbon dioxide (VE/VCO2), estimated physiologic dead space/tidal volume ratio (VD/VT), VE/VCO2 slope, heart rate, systemic arterial pressure, VE/exercise time slope, and VT/exercise time slope during every incremental exercise. Mean maximum exercise values of heart rate, systolic systemic arterial pressure, diastolic systemic arterial pressure, VD/VT, respiratory rate, peak VO2, VO2/heart rate, VE/CO2, and maximum exercise time were unchanged by inhalation of nitric oxide. There was a strong trend toward reduction of VE/VO2 from 53 +/- 15 to 47 +/- 12 (p = 0.051) and in maximum VE from 58 +/- 21 to 48 +/- 17 L x min(-1) (p = 0.059). Maximum VT decreased from 1639 +/- 556 to 1406 +/- 479 ml (p = 0.04). The VE/VCO2 slope was reduced from 43 +/- 12 to 35 +/- 8 (p = 0.018). Two patients had signs of pulmonary congestion during peak exercise or the recovery period with inhalation of nitric oxide. The VE/exercise time slope and VT/exercise time slope during incremental exercise were reduced by inhalation of nitric oxide, demonstrating a statistically significant minor increase in VE and VT. Inhalation of nitric oxide attenuated the excessive increase in VT response to exercise in CHF. The L-arginine-nitric oxide pathway may be involved in mechanisms contributing to hyperventilation during exercise in CHF.

Respiratory system mechanics in patients treated with isotonic or hypertonic NaCl solutions

Twenty-one patients who underwent elective surgery for coronary artery bypass were studied right after chest wall closure. They were anesthetized, paralyzed, and artificially ventilated with a constant-flow ventilator. Airflow, changes in lung volume, and tracheal pressure were measured. Respiratory system resistance (Rrs,max) was partitioned into its homogeneous (Rrs,min) and uneven (Rrs,u) components. Respiratory system elastance (Ers) was also measured. The subjects were randomly divided into two groups injected with test solutions just after chest wall closure: eleven patients received isotonic saline (0.9% NaCl solution), whereas the remaining ten were injected with hypertonic saline (7.5% NaCl solution). In all patients, mechanical parameters were measured at six different times: just before infusion, at 5 and 10 min (end of infusion); and at 15, 20, and 25 min after beginning of injection. No statistically significant differences were observed in respiratory system mechanical parameters between groups or between different times within each group. Our data suggest that hypertonic saline infusion does not result in significant changes in respiratory system mechanics in patients submitted to coronary artery bypass.

Flow and volume dependence of respiratory system mechanics during constant flow ventilation in normal subjects and in adult respiratory distress syndrome

Seven control subjects and seven patients with adult respiratory distress syndrome (ARDS) were artificially ventilated and flow, volume, and tracheal pressure were monitored. Respiratory system resistance (Rrs,max) was partitioned into its homogeneous (Rrs,min) and uneven (Rrs,u) components. Respiratory system elastance (Ers) was also measured. In both groups Ers did not vary with different inspiratory flows and volumes, but was significantly higher in ARDS. With increasing volume (isoflow maneuvers), Rrs,max and Rrs,u increased but Rrs,min remained unaltered in ARDS. In control patients, however, resistances did not vary but Rrs,max and Rrs,u were smaller and Rrs,min equaled their corresponding values in ARDS. Hence, stress relaxation seems to be increased in ARDS. During isovolume maneuvers Rrs,max and Rrs,u decreased with increasing flows (both groups), although they were significantly higher in ARDS. Rrs,min was not modified by different flows and was similar in both groups. Thus, pendelluft is also increased in ARDS. In conclusion, the mechanical profile of ARDS is characterized by increased Ers and Rrs,max, the latter being secondary to augmented mechanical unevenness within the system.

[Bilateral diaphragmatic paralysis in the immediate postoperative period after cardiac surgery]

A 56 years old man was submitted to an aortic replacement with mechanical prosthesis and to saphenous vein graft to the right coronary artery. He developed respiratory insufficiency after surgery which was finally related to bilateral diaphragmatic paralysis whose diagnosis was confirmed through thorax ultrasonography. The patient remained under ventilatory assistance with positive pressure for 75 days. The introduction of thorax ventilatory negative pressure (VNP), jacket type, allowed the tracheostomy closure. The patient gradually recovered his spontaneous breathing and was discharged after 90 days with instructions to use VNP at night. He returned to his normal professional activities, without auxiliary respiratory support, 40 days after his discharge.

Expiratory mechanics before and after uncomplicated heart surgery

In 12 mechanically ventilated anesthetized paralyzed patients undergoing cardiac surgery for either coronary bypass or for correcting valvular dysfunction volume, airflow, tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastance and resistance were partitioned into their lung and chest wall components throughout tidal relaxed expiration. Measurements were performed prior to thoracotomy and just after rib cage closure. Before surgery, patients with valvular disease had significantly higher respiratory system and lung elastances and resistances than those with ischemic heart disease. After surgery, patients with valvular disease showed a decrease in respiratory system and lung resistances. Surgery strikingly modified chest wall resistive properties in both groups. Postoperatively, the mechanical properties of the respiratory system were very similar in valvular and ischemic patients.

Pre- and postoperative inspiratory mechanics in ischemic and valvular heart disease

In 12 mechanically-ventilated, anesthetized, paralyzed patients undergoing cardiac surgery for either coronary bypass (six subjects) or to correct valvular disfunctions, volume, airflow, tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastance and resistance were partitioned into lung and chest wall components. Resistances were further split into homogeneous and uneven elements. Measurements were performed prior to thoracotomy and just after rib cage closure. Before surgery, valvular patients had significantly higher elastances and uneven resistances of the respiratory system and lung than those with ischemic heart disease. Postoperatively, the patients presented with an increase in respiratory system and lung elastances, a decrease in pulmonary resistance, and a rise in chest wall resistance. Surgically induced mechanical changes were similar in ischemic and valvular patients.

Heart transplantation in patients with Chagas' disease cardiomyopathy

Among 26 heart transplant patients, four had Chagas' disease cardiomyopathy. They were male patients, aged 28 to 43 years; three were in New York Heart Association class IV, and one was in class II but with refractory arrhythmias. The immunosuppressive protocol was cyclosporine and steroids in the first patient, and cyclosporine, azathioprine, and steroids in the last patient. Three patients had one or more rejection episodes, and one had none. One patient had a lymphoproliferative intestinal disease. Three patients had a new acute phase of Chagas' disease in postoperative days 59, 81, and 420, with fever, skin lesions, and myocarditis. The Trypanosoma cruzi was found in skin lesions in all three patients and in the myocardial biopsy in two patients. The laboratory tests did not show the expected results for the acute phase. All the alterations were reversed by specific therapy in a few days. One patient died on postoperative day 197 from rejection, and the immunosuppression was diminished because of the lymphoproliferative disease; the others were well 107, 160, and 500 days after the transplantation. The conclusions were as follows: (1) It seems that steroid pulse therapy predisposes the patient to a new acute phase of Chagas' disease. (2) Clinical presentation and laboratory test results of the acute phase are not the usual. (3) Specific drug therapy reverses all the alterations of this acute phase in a few days. (4) Although additional care is necessary and specific complications are expected, heart transplantation can be done with good results in patients with Chagas' cardiomyopathy.

Hemodynamic effects of hypertonic sodium chloride during surgical treatment of aortic aneurysms

Thoracoabdominal aortic surgery with aortic clamping is normally associated with major volemic shifts when the clamp is removed. This study compares the hemodynamic effects of hypertonic (HS) and isotonic (IS) solutions of sodium chloride (NaCl) infusions on the severe hypotension which follows aortic unclamping. Five consecutive patients received HS, and five received IS immediately after aortic unclamping. Blood loss, diuresis, and blood and crystalloid infusions were monitored throughout the operation. Blood gases, and pH, and hematocrit, hemoglobin, and plasma electrolyte levels were controlled during and 24 hours after surgery. Systemic arterial pressure, pulmonary arterial and wedge pressures, cardiac output, and systemic and pulmonary vascular resistance were monitored at the start of the operation, during aortic clamping, immediately after unclamping, immediately after HS or IS NaCl infusion and at the end of the operation. Patients who received HS NaCl exhibited higher pulmonary arterial and wedge pressures, higher cardiac index, and lower systemic and pulmonary vascular resistances immediately after the infusion. These patients required less volume transfusion than patients who received IS NaCl, despite slightly higher blood losses. It is concluded that HS NaCl is useful for the treatment of human hemorrhagic shock.