Extracorporeal CO2 Removal in a Lung Lavage Induced Respiratory Distress Syndrome

Ten pigs with experimental respiratory distress syndrome were treated by extracorporeal CO2 removal (ECCO2-R) combined with low frequency positive pressure ventilation (LPPV). After lung damage had been induced by repeated lung lavages a PEEP trial was conducted in order to find the appropriate PEEP for the damaged lungs. This PEEP was then applied during the ECCO2-R/LPPV period. Blood gas values improved significantly on extracorporeal bypass within a short time (pre-bypass paO2: 54.2 ± 3.7 vs 168.5 ± 31.6 mmHg after 15 min on bypass, p < 0.001) and were kept constant during the next 4 hours. Minute ventilation (MV) was reduced from 4.01 ± 0.31 to 0.74 ± 0.07 l/min (p < 0.0001), FiO2 of the ventilator from 1.0 to 0.46 ± 0.08 (p < 0.0001) whereas FiO2 of the membrane lung (ML) was not changed significantly (FIO2ML 0.59 ± 0.07 vs 0.53 ± 0.06). During controlled mechanical ventilation (CMV), comparable adequate gas exchange was only achieved at a significantly higher mean airway pressure ([Formula: see text] vs 21.2 ± 0.47 cmH20, p < 0.0001). Hemodynamic variables did not change significantly during bypass time. ECCO2-R/LPPV driven by a simple renal perfusion system allows adequate gas exchange in experimental respiratory failure.

Mechanical Support of the Left Ventricle in Ischemia Induced Left Ventricular Failure: An Experimental Study

Objective

this study compares the hemodynamic effects of intraaortic balloon pumping (IABP), left ventricular assist device (LVAD), and extracorporeal membrane oxygenation (ECMO) in left ventricular failure in pigs.

Methods

In 29 pigs weighing 12 + 0.7 kg left ventricular failure was induced by ligating the left anterior descending coronary artery. Eight animals served as controls. Eight pigs were treated by IABP, seven by LVAD, and six by ECMO. The study period lasted four hours. Hemodynamic and oxygen transport/ uptake parameters were measured continuously or intermittently.

Results

Six animals of the ECMO and LVAD groups survived the 4 hour period, but only 3 and 4 animals of the IABP and control groups survived (p<0.05). Cardiac index decreased about 48% and 22% in the control and IABP groups (p<0.05), whereas there was only a slight decrease in the ECMO (9%) and LVAD (14%) groups. Oxygen delivery fell significantly in the control and IABP groups (p<0.05), compared with only a slight change in the LVAD and ECMO groups.

Conclusion

ECMO is the most effective system for temporary circulatory support in severe ventricular failure. LVAD maintains cardiac output when pulmonary blood flow is provided. IABP is less efficient in supporting the failing heart, especially in the presence of severe ventricular arrhythmias.

Activation of the Clotting System: Heparin-Coated versus Non Coated Systems for Extracorporeal Circulation

The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups.

Methods.

Eight pigs weighing 19.7 (± 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly.

Results.

The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups.

Conclusions.

The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.

Strategien zur Optimierung notärztlicher Kompetenz in der Flugrettung

PURPOSE

Preclinical emergency medical treatment necessitates a comprehensive interdisciplinary knowledge by the emergency physician as well as a high level of manual dexterity. The quality of treatment therefore depends on the level of education and continuous training in emergency medical techniques. Based on an evaluation of the frequency of life-saving interventions by a physician-staffed rescue helicopter system, strategies for in-hospital training of relevant skills are suggested.

MATERIAL AND METHODS

At the outset, 10 important areas of treatment (e.g. intubation, chest tube etc.) and their frequency in emergency medical services were defined as the standard to be attained by emergency physicians within 1 year. The selection of the areas of treatment was based to some extent on international recommendations. The actual frequencies of the prehospital interventions were compared to the required minimum numbers by retrospective analysis of the helicopter rescue database (NACA-X).

RESULTS

During the observation period of 1 year, 20 emergency physicians responded to 956 prehospital emergency calls. A life-threatening condition requiring an on-site intervention occurred in only 521 (54.5%) patients, so that the majority of physicians did not perform the required minimum number of interventions. In order to maintain their level of skill, the emergency physicians were required to undertake additional training at the local university hospital.

CONCLUSION

The frequency of on-site life-saving interventions in emergency medicine is insufficient to fulfill the quota necessary to maintain adequate training of emergency physicians. Only a link-up program at a hospital for primary care can ensure an adequate training level.

[Autocapture(TM) and Capture Management(TM) Current concepts in pacing threshold and output management]

Pacing threshold is not a stable value during the pacemaker's life. It is affected by many physiological, pharmacological and pathophysiological factors. A pacing system able to confirm capture and automatically adjust its output to the actual pacing threshold is highly desirable for a prolonged battery life and maximal patient safety. The Autocapture(TM) of St. Jude Medical and the Capture Management(TM) of Medtronic are currently available on the market. The key feature is the measurement of the evoked response (ER) signal by the pacemaker for capture confirmation. In case of loss of capture, the Autocapture(TM) System delivers a back up safety pulse of 4.5 Volt and 0.49 ms and starts a new threshold search. The pacemaker adapts its output to 0.3V/0.25V above the newly measured threshold. This system needs bipolar leads with low polarization for the first generation in Microny® and Regency® pacemakers; in the second generation with Affinity® and Integrity® pacemakers various bipolar leads are suitable. The Capture Management(TM) System of Medtronic, available in the Kappa® DR 700 series, performs a two point automatic threshold search once every day during rest. The output is determined by the programmed safety margin (nominal 1.5×voltage threshold). A backup pulse is only delivered during the threshold search. No special electrodes are necessary.    These functions were shown to work safely and efficaciously in multicenter trials to decrease the current consumption with a prolongation of battery life up to 142%. The patients safety was increased by identifying changes of the capture threshold over time and adjusting the pacing stimulus. The conventional safety margins of 100% might not be safe for all patients. We also learned much about lead maturation and lead instability by the possibility of continuous follow-up of threshold changes in a larger group of leads in order to identify the risk group of about 10% of patients with late threshold increase and lead instability.

[Lead stability in long-term follow-up of bipolar leads]

From 1990 to 1999, 2,853 ventricular and 1,084 atrial bipolar leads of various manufacturers (Medtronic, Biotronik, Vitatron, Ela, Pacesetter and Stöckert) were implanted during first implantations of pacemakers at the University of Graz, Dept. of Cardiac Surgery. Surgical complications with the need of reintervention were analyzed during a follow up period of up to 10 years. The overall lead-related complication rate for ventricular bipolar leads was 6.5% (187 of 2,853) and 5.3% (58 of 1,084) for atrial bipolar leads. Early complications within the first month were higher in the atrium (5.3% versus 2.2% in the ventricle), primarily due to dislocation, late complications were higher in the ventricle (4.3% versus 2% in the atrium) due to insulation problems and lead fracture. Insulation material had a marked influence with a higher failure rate in some leads with polyurethane insulation compared with silicone. Therefore we recommend a close follow-up of bipolar polyurethane leads by measurement of chronic impedance in order to assess insulation problems as early as possible.

The effect of positive end-expiratory pressure during partial liquid ventilation in acute lung injury in piglets

OBJECTIVES

To investigate the effects of positive end-expiratory pressure (PEEP) application during partial liquid ventilation (PLV) on gas exchange, lung mechanics, and hemodynamics in acute lung injury.

DESIGN

Prospective, randomized, experimental study.

SETTING

University research laboratory.

SUBJECTS

Six piglets weighing 7 to 12 kg.

INTERVENTIONS

After induction of anesthesia, tracheostomy, and controlled mechanical ventilation, animals were instrumented with two central venous catheters, a pulmonary artery catheter and two arterial catheters, and an ultrasonic flow probe around the pulmonary artery. Acute lung injury was induced by the infusion of oleic acid (0.08 mL/kg) and repeated lung lavage procedures with 0.9% sodium chloride (20 mL/kg). The protocol consisted of four different PEEP levels (0, 5, 10, and 15 cm H2O) randomly applied during PLV. The oxygenated and warmed perfluorocarbon liquid (30 mL/kg) was instilled into the trachea over 5 mins without changing the ventilator settings.

MEASUREMENTS AND MAIN RESULTS

Airway pressures, tidal volumes, dynamic and static pulmonary compliance, mean and expiratory airway resistances, and arterial blood gases were measured. In addition, dynamic pressure/volume loops were recorded. Hemodynamic monitoring included right atrial, mean pulmonary artery, pulmonary capillary wedge, and mean systemic arterial pressures and continuous flow recording at the pulmonary artery. The infusion of oleic acid combined with two to five lung lavage procedures induced a significant reduction in PaO2/FI(O2) from 485 +/- 28 torr (64 +/- 3.6 kPa) to 68 +/- 3.2 torr (9.0 +/- 0.4 kPa) (p < .01) and in static pulmonary compliance from 1.3 +/- 0.06 to 0.67 +/- 0.04 mL/cm H2O/kg (p < .01). During PLV, PaO2/FI(O2) increased significantly from 68 +/- 3.2 torr (8.9 +/- 0.4 kPa) to >200 torr (>26 kPa) (p < .01). The highest PaO2 values were observed during PLV with PEEP of 15 cm H2O. Deadspace ventilation was lower during PLV when PEEP levels of 10 to 15 cm H2O were applied. There were no differences in hemodynamic data during PLV with PEEP levels up to 10 cm H2O. However, PEEP levels of 15 cm H2O resulted in a significant decrease in cardiac output. Dynamic pressure/volume loops showed early inspiratory pressure spikes during PLV with PEEP levels of 0 and 5 cm H2O.

CONCLUSIONS

Partial liquid ventilation is a useful technique to improve oxygenation in severe acute lung injury. The application of PEEP during PLV further improves oxygenation and lung mechanics. PEEP levels of 10 cm H2O seem to be optimal to improve oxygenation and lung mechanics.

Partial liquid ventilation combined with kinetic therapy in acute respiratory failure in piglets

OBJECTIVE

To investigate the effect of the combination of kinetic therapy (KT) with partial liquid ventilation (PLV) on gas exchange, lung mechanics and hemodynamics in acute lung injury (ALI).

DESIGN

Prospective, randomized, controlled pilot study.

SETTING

University research laboratory.

SUBJECTS

Eleven piglets weighing 8.3+/-0.9 kg.

INTERVENTION

ALI was induced by the infusion of oleic acid (0.08 ml/kg) and repeated lung lavages with 0.9% NaCl (20 ml kg(-1)). Thereafter the animals were randomly assigned either for PLV or a combination of PLV with KT (PLV/KT). The dose of perfluorocarbon administered was 30 ml/kg, evaporative losses were substituted with 5 ml/kg per h.

MEASUREMENTS AND MAIN RESULTS

Airway pressures, tidal volumes, dynamic compliance (Cdyn), expiratory airway resistance and arterial blood gases were measured. Hemodynamic monitoring included right atrial, mean pulmonary artery, pulmonary capillary wedge and mean systemic arterial pressures, and continuous flow recording of the pulmonary artery. In both groups the induction of ALI significantly reduced PaO2/FIO2 Cdyn and cardiac output, and significantly increased pulmonary artery pressure. After the initiation of PLV there was a significant increase of PaO2/FIO2, and Cdyn, and a significant decrease of pulmonary artery pressure in both groups. Except the PaCO2, which showed significantly lower values in the PLV/KT group, no variables showed any differences between the two groups.

CONCLUSION

The additional use of KT did not show beneficial effects on oxygenation and lung mechanics during PLV. However, at constant minute ventilation PaCO2 levels were significantly lower during PLV/KT, indicating some positive influence on the ventilation/perfusion distribution within the lung. Extreme body positions during PLV/KT did not show any significant hemodynamic side effects.

Minimally invasive versus conventional aortic valve operations: a prospective study in 120 patients

BACKGROUND

Risk evaluation comparing the minimally invasive and standard aortic valve operations has not been studied.

METHODS

Four surgeons were randomly assigned to perform the minimally invasive (L-shaped sternotomy) (group 1) or the conventional (group 2) operation in 120 patients exclusively.

RESULTS

In both groups (n = 60) a CarboMedics prothesis was implanted in 90% of patients. There was no significant difference in the cross-clamping period (group 1, 60 minutes; range, 35 to 116 minutes), in the duration of extracorporal circulation (group 1, 84 minutes; range, 51 to 179 minutes) or in the time from skin-to-skin (group 1, 195 minutes; range, 145 to 466 minutes). Patients in group 1 were extubated earlier (p<0.001), the postoperative blood loss was less (p<0.001), and the need for analgesics was reduced (p<0.05). In 5 patients in group 1 a redo operation was required for bleeding (p>0.05), 3 patients in group 1 required a redo operation because of paravalvular leakage or endocarditis (p>0.05), the 30-day mortality rate was 1.6%. Overall the survival rate was 95% in group 1 and 97% in group 2 (mean follow-up, 294 days; range, 30 to 745 days).

CONCLUSION

The advantages of minimally invasive aortic valve operation include reduced trauma from incision and duration of ventilation, decreased blood loss and postoperative pain, the avoidance of groin cannulation, and a cosmetically attractive result. Simple equipment is used with a high degree of effectiveness and with no sacrifice of safety. Our study demonstrated the practicability and reliability of this new method.

The influence of different strategies on clinical outcome in patients undergoing total cavopulmonary connection

BACKGROUND

We report on results of a prospective clinical trial designed to demonstrate the influence of various strategies in "Total Cavopulmonary Connection" (TCPC) for palliative therapy of patients with "single ventricle" physiology.

METHODS

From 1989 to 1997, a total of 47 patients (mean age 4.8 +/- 3.6 years) underwent definitive TCPC at our unit. 31 patients (66%) underwent one-stage TCPC, in 16 patients (34%) we performed a two-stage modified Fontan operation; 21 patients had central fenestration (4 mm). Inhalative NO therapy in the immediate postoperative period was adopted in 1993.

RESULTS

Overall 5-year survival was 76.4%, after two-stage TCPC 87.5%, and 81.3% in patients undergoing fenestrated procedures. Two of three patients survived perioperative Fontan take-down. We lost 11 patients (nine early and two late deaths): three patients died primarily because of neurologic dysfunction and eight patients because of cardiac failures. Under perioperative NO therapy there was no early death. After a mean follow-up of 35.9 +/- 23.3 months, 76% of all patients were in NYHA I and 21 % in NYHA I-II. 89.7% had sinus rhythm. 42% of our patients suffered from temporary pleuropericardial effusions.

CONCLUSIONS

Definitive palliation with TCPC achieves acceptable clinical results. Two-stage repair, fenestration, and postoperative inhalative NO therapy - each have a positive influence on early and long-term survival.

Effects of inhaled nitric oxide during permissive hypercapnia in acute respiratory failure in piglets

OBJECTIVE

To look for the effects of inhaled nitric oxide on oxygenation and pulmonary hemodynamics during acute hypercapnia in acute respiratory failure.

DESIGN

Prospective, randomized, experimental study.

SETTING

University research laboratory.

SUBJECTS

Ten piglets, weighing 9 to 13 kg.

INTERVENTIONS

Acute respiratory failure was induced by oleic acid infusion and repeated lung lavages with 0.9% sodium chloride. The protocol consisted of three randomly assigned periods with different PaCO2 levels. Tidal volume was reduced to induce hypercapnia. Inspiratory time was prolonged to achieve similar mean airway pressures. During permissive hypercapnia, pH was not corrected. At each PaCO2 period, the animals were ventilated with inhaled nitric oxide of 10 parts per million and without nitric oxide inhalation.

MEASUREMENTS AND MAIN RESULTS

Continuous hemodynamic monitoring included right atrial, mean pulmonary arterial, and mean systemic arterial pressures, arterial and mixed venous oxygen saturations, and continuous flow recording at the pulmonary artery. In addition, airway pressures, tidal volumes, dynamic lung compliance and airway resistance, end-tidal CO2 concentrations, and arterial and mixed venous blood gases were measured. Data were obtained at baseline and after lung injury, at normocapnia, at two levels of hypercapnia with and without nitric oxide inhalation. Acute hypercapnia resulted in a significant decrease in blood pH and a significant increase in mean pulmonary arterial pressure. There was no significant change in PaO2 during normocapnia and hypercapnia. Inhaled nitric oxide significantly decreased the mean pulmonary arterial pressure during both hypercapnic periods. It significantly improved oxygenation during both normocapnia and hypercapnia.

CONCLUSIONS

Acute hypercapnia resulted in a significant increase in pulmonary arterial pressure without influencing oxygenation and cardiac output. Inhaled nitric oxide significantly reduced the pulmonary hypertension induced by acute permissive hypercapnia but did not influence the flow through the pulmonary artery. Inhaled nitric oxide significantly improved oxygenation in this model of acute lung injury during normocapnia and acute hypercapnia.

Inhaled nitric oxide in infants and children after open heart surgery

OBJECTIVE

To assess the effects of inhaled nitric oxide (NO) on oxygenation and pulmonary circulation in infants and children with critical pulmonary perfusion and/or hypoxemia after open heart surgery.

STUDY

A prospective case series report.

SETTING

A multidisciplinary pediatric intensive care unit in a University hospital

PATIENTS

From June 1993 to March 1996 37 pediatric patients after open heart surgery were treated with inhaled NO. Their mean age was 2.9+/-0.6 years, their mean body weight 12.6+/-1.8 kg.

METHODS

Inhaled NO was applied using a microprocessor controlled delivery system which continuously measured NO and NO2 by the chemilumniscence method. Monitoring included ECG, continuous pulse oximetry (SaO2), arterial (AP), central venous (CVP) and left atrial (LAP) pressures and in 8 patients a pulmonary artery (PAP) pressure. Inhaled NO was started at an SaO2 <90% with a fraction of inspired oxygen concentration (FiO2) >0.7, at a mean pulmonary artery pressure (MPAP) >50% of the mean arterial pressure (MAP), and in patients after Fontan-procedure at a CVP-LAP pressure gradient >10 mmHg.

RESULTS

The mean dose of inhaled NO was 3.7+/-0.3 ppm and the mean duration was 112+/-14.7 hours. For the whole group SaO2 increased from 79.6+/-2.3 to 90.1+/-1.5% (p<0.01) within 20 minutes of NO-inhalation. Inhaled NO significantly decreased the MPAP from 47.8+/-4 to 27.5+/-2.3 mmHg (p<0.01) in 8 patients with postoperative pulmonary hypertension and significantly decreased the transpulmonary pressure (CVP-LAP) from 14.3+/-0.8 to 7.3+/-0.9 mmHg (p<0.01) in 16 patients after Glenn- or Fontan-procedure.

CONCLUSIONS

Inhaled NO is very effective to decrease pulmonary artery pressure, to improve oxygenation, and to improve Fontan-circulation in infants and children after open heart surgery.

Venous thrombosis in and after extracorporeal membrane oxygenation: detection and follow-up by color Doppler sonography

The purpose of our study was to evaluate thrombosis of venous vessels during and after extracorporeal membrane oxygenation (ECMO) using color Doppler sonography. We prospectively performed serial color Doppler sonography investigations in 30 ECMO patients [age: newborn to 3 years, male:female = 20:10, venoarterial (VA) ECMO = 18, venovenous (VV) ECMO = 12]. During ECMO obstruction and/or thrombosis of the superior vena cava (SVC) was observed in 2 neonates on VA ECMO. Furthermore, a thrombotic clot from an initially open duct of Arantii with partial portal vein thrombosis, reaching into the inferior vena cava (IVC), occurred despite adequate heparinization. After ECMO, late septic SVC thrombus occurred in one neonate. IVC thrombus was observed in two pediatric VV ECMO patients. The overall incidence of venous clots was 20 % (6 of 30). Routine color Doppler sonography monitoring of vessels in children on and after ECMO was found to be useful for early detection of venous thrombosis. It enabled consequent administration of appropriate therapy as well as follow-up after decannulation and reconstruction.

Activation of the clotting system: heparin-coated versus non coated systems for extracorporeal circulation

The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups.

METHODS

Eight pigs weighing 19.7 (+/- 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly

RESULTS

The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups.

CONCLUSIONS

The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.

[Accessory mitral valve tissue as a rare cause of subaortic stenosis and valvular aortic insufficiency]

An unusual case of subaortic stenosis and aortic regurgitation caused by accessory mitral valve tissue in a 10 year old boy is reported. Two-dimensional and Doppler echocardiography revealed the characteristic feature of a mobile, parachute-like mass in the left ventricular outflow tract pro-lapsing into the aortic valve during systole and, thus, producing a systolic pressure gradient of 70 mm Hg between the left ventricle and aorta and causing mild aortic regurgitation. The accessory valve tissue was completely excised via an aortotomy without injury to the normal mitral and aortic valves. Two dimensional echocardiography provides excellent morphological information about the relationship between the accessory mitral valve tissue and the mitral and aortic valves, respectively. Accurate preoperative evaluation by two-dimensional echocardiography facilitates the successful surgical management of this rare condition.

Assessment of lung function in neonates during extracorporeal membrane oxygenation

We report our experience with pulmonary function testing in 11 out of 22 full-term neonates with severe respiratory failure, treated at the ECMO center Graz (Austria) during the period from 1990 to 1995. Altogether 17 out of 22 patients survived ECMO and all of them were successfully weaned from ECMO. Pulmonary function was assessed by monitoring expiratory tidal volume on the ventilator and estimating respiratory system compliance from the ratio tidal volume/(PIP-PEEP). In addition, compliance, and functional residual capacity were measured using a computerized pulmonary function system (PEDS). Compliance (mean +/- SD) decreased markedly after 24 hours of ECMO, compared with baseline values (0.20 +/- 0.12 vs 0.12 +/- 0.13 ml/cmH2O/kg) and was significantly higher (0.43 +/- 0.14 ml/cmH2O/kg, p < 0.01) before ECMO stop. When tidal volumes increased continuously ECMO blood flow could be decreased, indicating lung recovery. Most patients had a tidal volume of > 7 ml/kg prior to decannulation. Functional residual capacity and corresponding dynamic compliance, measured in 5 patients, ranged from 18.6 to 29.6 ml/kg and 0.49 to 0.57 ml/cmH2O/kg at this time. Functional residual capacity (mean +/- SD) increased significantly when surfactant was administered to promote weaning from ECMO (8.28 +/- 0.9 vs 19.0 +/- 1.0 ml/kg, p < 0.01). We conclude that the assessment of lung function has improved our understanding of pulmonary recovery during ECMO. Its clinical significance in determining the optimum time of weaning from ECMO needs further evaluation.

Inhaled nitric oxide in patients with critical pulmonary perfusion after Fontan-type procedures and bidirectional Glenn anastomosis

OBJECTIVE

The aim of this study was to evaluate the effects of inhaled nitric oxide in patients with critical pulmonary perfusion after Fontan-type procedures and bidirectional Glenn anastomosis.

METHODS

Inhaled nitric oxide (mean 4.1 +/- 0.7 ppm, 1.5 to 10 ppm) was administered in 13 patients (mean age 5.6 +/- 1.6 years, 1.5 to 17 years) with critical pulmonary perfusion (central venous pressure > 20 mm Hg or transpulmonary pressure gradient > 10 mm Hg) in the early postoperative period after total cavopulmonary connection (n = 9) or after bidirectional Glenn anastomosis (n = 4).

RESULTS

In patients after total cavopulmonary connection inhaled nitric oxide therapy decreased central venous pressure by 15.3% +/- 1.4% (p = 0.0001) and transpulmonary pressure gradient by 42% +/- 8% (p = 0.0008) and increased mean systemic arterial and left atrial pressures by 12% +/- 3.6% (p = 0.011) and 28% +/- 8% (p = 0.007), respectively. Arterial and venous oxygen saturations improved by 8.2% +/- 1% (p = 0.005) and 14% +/- 4.3% (p = 0.03), respectively. In patients after bidirectional Glenn anastomosis inhaled nitric oxide therapy resulted in a decrease of central venous pressure by 22% +/- 1% and of the transpulmonary pressure gradient by 55% +/- 6% and improved arterial and venous oxygen saturations by 37% +/- 29% and 11% +/- 3%, respectively. Mean systemic arterial and left atrial pressures remained nearly unchanged. No toxic side effect was observed in any patient.

CONCLUSION

Inhaled nitric oxide may play an important role in the management of transient critical pulmonary perfusion caused by reactive elevated pulmonary vascular resistance in the early postoperative period after Fontan-type operations and bidirectional Glenn anastomosis.

Partial liquid ventilation combined with inhaled nitric oxide in acute respiratory failure with pulmonary hypertension in piglets

This study was a prospective, randomized, controlled design to evaluate gas exchange, lung mechanics, and pulmonary hemodynamics during partial liquid ventilation (PLV) combined with inhaled nitric oxide (NO) in acute respiratory failure (ARF) with pulmonary hypertension (PH). ARF with PH was induced in 12 piglets weighing 9.7-13.7 kg by repeated lung lavages and the continuous infusion of the stable endoperoxane analog of thromboxane. Thereafter the animals were randomly assigned either for PLV or conventional mechanical ventilation (CMV) at a fractional concentration of inspired O2 (Fio2) of 1.0. Perfluorocarbon (PFC) liquid (30 mL kg-1) was instilled into the endotracheal tube over 5 min followed by 5 mL kg-1h-1. All animals were treated with different concentrations of NO (1-10-20 ppm) inhaled in random order. Continuous monitoring included ECG, right atrial (Pra), mean pulmonary artery (Ppa), pulmonary capillary (Ppc'), and mean arterial (Pa) pressures, arteria oxygen saturation, and mixed venous oxygen saturation measurements. During PLV Pao2/Fio2 increased significantly from 8.2 +/- 0.4 kPa to 34.8 +/- 5.1 kPa (p < 0.01), whereas Pao2/FiO2 remained constant at 9.5 +/- 0.4 kPa during CMV. The infusion of the endoperoxane analog resulted in a sudden decrease of Pao2/Fio2 from 34.8 +/- 5.1 kPa to 14.1 +/- 0.4 kPa (p < 0.01) in the PLV group and from 9.5 +/- 0.4 kPa to 6.9 +/- 0.2 kPa (p < 0.05) in the control group. Inhaled NO significantly improved oxygenation in both groups (Pao2/Fio2: 45.7 +/- 5.3 kPa during PLV and 25.9 +/- 4.7 kPa during CMV). During inhalation of NO mean Ppa decreased significantly from 7.8 +/- 0.26 kPa to 4.2 +/- 0.26 kPa (p < 0.01) in the PLV group and from 7.4 +/- 0.26 kPa to 5.1 +/- 0.13 kPa (p < 0.01) in the control group. As documented in the literature PLV significantly improves oxygenation and lung mechanics in severe ARF. In addition, when ARF is associated with severe PH, the combined treatment of PLV and inhaled NO improves pulmonary hemodynamics resulting in better oxygenation.

Concomitant procedures in the small versus standard aortic root

BACKGROUND AND AIMS OF THE STUDY

Aortic valve replacement (AVR) in the small aortic root (SAR) has always been a severe challenge with an uncertain surgical outcome. The purpose of this study was to assess the surgical and clinical performance of 19 mm and 21 mm CarboMedics valves (CPHV) based on a review of valve-related morbidity and mortality over a period of six years.

METHODS

A total of 361 patients undergoing aortic valve replacement (AVR) with the CPHV between January 1989 and August 1995 was subdivided and studied. (i) Group A patients (n = 137) received 19 mm or 21 mm prostheses; subgroup AI (n = 85) underwent isolated AVR and subgroup AII (n = 52) underwent AVR with associated cardiac procedures. (ii) Group B patients (n = 224) were given 23 mm or larger prostheses; subgroup BI (n = 147) underwent isolated AVR and subgroup BII (n = 77) underwent AVR with concomitant cardiac procedures.

RESULTS

Hospital mortality was group A 7.3% versus group B 4.9%. Cumulative survival after six years was 83.7% in AI and 76.9% in AII versus 72.1% in BI and 77.4% in BII. There were no significant statistical differences between the subgroups concerning cardiac mortality. Thromboembolic events occurred with a linearized rate of 1.41%/pty in group A versus 1.03%/pty in group B, the incidence of anticoagulant-related major hemorrhage was 1.41%/pty in group A versus 1.20%/pty in group B and that of periprosthetic leakage 1.69%/pty in group A versus 1.89%/pty in group B.

CONCLUSION

Our results demonstrate that this bileaflet prosthesis is highly efficient in patients with small aortic roots undergoing AVR with or without associated procedures.

Activation of the clotting system during extracorporeal membrane oxygenation in term newborn infants

OBJECTIVES

To determine the degree of clotting activation that occurs with the usual anticoagulation regimen with systemic heparinization.

METHODS

To allow a standardized comparison of the patients, this study focused on the first 48 hours of extracorporeal membrane oxygenation (ECMO) in term newborn infants. The ECMO perfusion circuit consisted of a roller pump, silicone membrane lungs, and silicone rubber tubing. Coagulation was controlled routinely by measuring prothrombin time, fibrinogen, antithrombin III, and reptilase time. Platelet counts, activated clotting time, and heparin concentration were controlled regularly. The following specific activation markers of the clotting system were measured: prothrombin activation fragment 1 + 2(F1+2), thrombin-antithrombin III complexes, and D-dimer. Measurements were done before the start of ECMO, after 5 minutes, and at hours 1, 2, 3, 4, 6, 12, 24 and 48.

RESULTS

All seven term infants had excessively high levels of clotting activation markers within the first 2 hours of ECMO: F1+2, 11.6(+/- O.9) nmol/L (mean +/- SEM); thrombin-antithrombin, 920(+/- 2.2) microg/L; D-dimer, 15.522(+/- 3.689) ng/L. During the next 46 hours of ECMO, F1+2 and thrombin-antithrombin III complexes decreased from those high values, whereas D-dimer did not. The increase of activation markers was accompanied by low fibrinogen, low platelet counts. and prolongation of reptilase time.

CONCLUSIONS

These findings fit the pattern of consumptive coagulopathy during neonatal ECMO, especially in the first 24 hours.

Inhaled nitric oxide versus inhaled prostacyclin and intravenous versus inhaled prostacyclin in acute respiratory failure with pulmonary hypertension in piglets

This study was a prospective, randomized design to compare oxygenation and pulmonary hemodynamics between inhaled nitric oxide (NO) and inhaled prostacyclin (PGI2), and between inhaled and i.v. PGI2 in acute respiratory failure with pulmonary hypertension. Acute respiratory failure with pulmonary hypertension was induced in 12 piglets weighing 9-12 kg by repeated lung lavages and a continuous infusion of the stable endoperoxane analogue of thromboxane. Thereafter the animals were randomly assigned either for NO or PGI2 application. All animals were treated with different concentrations of NO or different doses of PGI2 applied i.v. and inhaled in random order. Continuous monitoring included ECG, central venous pressure (CVP), mean pulmonary artery pressure (MPAP), mean arterial pressure (MAP), arterial oxygen saturation (SaO2), and mixed venous oxygen saturation (SvO2) measurements. NO inhalation of 10 ppm resulted in a significant increase in PaO2/fraction of inspired oxygen (FiO2) from 7.8 +/- 1.34 kPa to 46.1 +/- 9.7 kPa. MPAP decreased significantly from 5.1 +/- 0.26 kPa to 3.7 +/- 0.26 kPa during inhaled NO of 40 ppm; i.v. infusion of PGI2 slightly increased oxygenation parameters. A significant increase in PaO2/FiO2 up to 32.4 +/- 3.1 kPa was observed during PGI2 aerosol delivery (p < 0.01); i.v. PGI2 decreased MAP from 11.5 +/- 0.39 kPa to 9.8 +/- 0.66 kPa (p < 0.05) and MPAP from 5.8 +/- 0.53 kPa to 4.5 +/- 0.66 kPa, respectively (p < 0.05). PGI2 aerosol delivery significantly decreased the MPAP to 3.7 +/- 0.53 kPa (p < 0.05) without influencing the MAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous blood density measurements and volume changes during extracorporeal circulation in patients undergoing cardiac surgery

The changes of blood volume and transcapillary fluid shifts during extracorporeal circulation (ECC) was examined using continuous measurements of blood density by the mechanical oscillator technique. Sixteen patients (1 female, 15 male) with a mean age of 61.4 years (+/- 7.6 years, 47-70 years) undergoing coronary artery bypass surgery were included in this study. The equipment for continuous measurement of the blood density (DPRT by Paar/Austria) was installed at the arterial line of the heart-lung bypass. Higher-precision discrete measurements of some parameters used the DMA 55 equipment produced by the Paar company. Measurements were taken at 37 degrees C. In 11 patients the transcapillary volume loss (difference of total volume between beginning and end of ECC) during heart-lung bypass (mean observation period of 55 min (+/- 16 min, 28-82 min) was found to be 870 ml/m2 body surface area (BSA) (+/- 360 ml, 290-1560 ml/m2) by the dilution method using the priming solution at the beginning and 500 ml lactated Ringer's solution added at the end of the ECC. The calculated volume shift using the "double density method", which takes into account blood density, plasma density, and hematocrit, amounted to 830 ml/m2 BSA (+/- 200 ml, 450-1210 ml/m2). The density of the transcapillary volume loss into the interstitial layer was calculated and found to be 1.0026 g/ml (+/- 0.0017 g/ml, 1.0003-1.0063 g/ml). A significant difference of transcapillary volume shift correlated with the administered catecholamine (dopamine, dobutamine) dosage postoperatively. Without catecholamine this difference was 260 ml/m2 BSA, with 3 microns/kg/min dopamine it rose to > 500 ml/m2 BSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Sonographically guided cannula positioning for extracorporeal membrane oxygenation

Drainage problems due to catheter malpositioning are acutely life-threatening in patients undergoing extracorporeal membrane oxygenation. In order to reduce these complications we introduced sonographically guided catheter positioning. We compare the outcome in a group of patients with blind cannula positioning to that in a group with sonographically guided catheter positioning. Our results show that neonates and young infants especially are at high risk of drainage problems due to catheter malposition and that their outcome could be markedly improved by introducing sonographically guided cannula insertion.

Hemodynamic effects of different modes of mechanical ventilation in acute cardiac and pulmonary failure: an experimental study

OBJECTIVE

To determine the hemodynamic effects of four different modes of mechanical ventilation in an animal model of acute cardiac and pulmonary failure.

DESIGN

Prospective, randomized, crossover design.

SETTING

University research laboratory.

SUBJECTS

Twelve piglets weighing 10 to 16 kg.

INTERVENTIONS

The experimental protocol consisted of three stable 30-min periods: when ventricular and pulmonary functions were normal (control), after the induction of acute cardiac failure by the administration of a beta-adrenergic receptor blocker, and after pulmonary failure induced by repeated lung lavage. Modes of mechanical ventilation included controlled mechanical ventilation, high-frequency oscillation, synchronized high-frequency jet ventilation, and external negative pressure oscillation combined with pressure support ventilation. Each mode of respiratory support was randomly and sequentially applied to each animal with the assessment of cardiopulmonary function at the end of each period.

MEASUREMENTS AND MAIN RESULTS

Continuous monitoring included electrocardiogram, right atrial, left ventricular end-diastolic, pulmonary arterial, intrathoracic aortic, arterial, esophageal, and transpulmonary pressures and arterial and mixed venous oxygen saturation measurements. In addition, cardiac output using the thermodilution technique was measured intermittently. Whereas in the control period cardiac index was significantly (p < .05) higher during synchronized high-frequency jet ventilation (193 +/- 19.3 mL/kg/min) than during controlled mechanical ventilation (151 +/- 12.1 mL/kg/min) and high-frequency oscillation (151 +/- 18.1 mL/kg/min), there was no significant hemodynamic difference between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. In the pulmonary failure period, transpulmonary pressure was significantly higher during high-frequency oscillation (7.1 +/- 1.6 mm Hg) than during controlled mechanical ventilation (5.6 +/- 0.6 mm Hg), high-frequency ventilation (4.1 +/- 0.4 mm Hg), and external negative pressure oscillation combined with pressure support ventilation (5.3 +/- 0.5 mm Hg).

CONCLUSIONS

Synchronized high-frequency ventilation improves cardiac performance in control conditions. No hemodynamic difference is present between the four modes of mechanical ventilation in the cardiac and pulmonary failure periods. External negative pressure oscillation combined with pressure support ventilation has moderate hemodynamic advantages over controlled mechanical ventilation and high-frequency oscillation in different clinical settings, but it also results in a deterioration of pulmonary gas exchange during the pulmonary failure period.

Proximal and tracheal airway pressures during different modes of mechanical ventilation: an animal model study

OBJECTIVE

To determine the differences between the mean proximal and tracheal airway pressures during 3 different modes of mechanical ventilation (MV) in an animal model of acute cardiac failure (CF) and respiratory failure (RF).

DESIGN

Prospective, randomized, cross-over design.

SETTING

University research laboratory.

SUBJECTS

Twelve young pigs weighing 10-16 kg.

INTERVENTIONS

The experimental protocol consisted of 3 stable 30 min conditions: when ventricular and pulmonary function was normal (control), after the induction of acute cardiac failure by a beta-blocking agent and after respiratory failure induced by repeated lung lavages. Modes of MV included controlled mechanical ventilation (CMV), high-frequency oscillation (HFO), and high-frequency jet ventilation (HFJV).

MEASUREMENTS AND RESULTS

The tracheal mean airway pressure (P(aw)) was measured at the distal port of the Hi-lo jet tube using an air-filled pressure transducer. The mean transpulmonary P(aw) increased significantly from 0.41 +/- 0.14 kPa during the control period to 1.15 +/- 0.17 kPa (P < 0.0001) during the RF period. In all study periods both the proximal and tracheal P(aw) were lowest during HFJV. There was no difference between the proximal and tracheal P(aw) during CMV and HFJV throughout the protocol. In the cardiac and respiratory failure periods the proximal P(aw) (CF, 1.45 +/- 0.08 kPa; RF, 3.13 +/- 0.27 kPa) was significantly higher than the tracheal P(aw) (CF, 1.04 +/- 0.09 kPa, P < 0.01; RF, 2.18 +/- 0.3 kPa, P < 0.01) with HFO. When ventilated by HFO, the mean external oscillatory amplitude was 4.33 +/- 0.14 kPa and the intratracheal oscillatory amplitude was only 0.49 +/- 0.06 kPa (P < 0.0001).

CONCLUSION

HFJV provides adequate respiratory support at lower P(aw) than CMV and HFO. Proximal P(aw) closely reflects tracheal P(aw) during CMV and HFJV. However, with HFO great pressure differences between the proximal and tracheal airways are evident. Therefore, additional intratracheal airway pressure monitoring seems to be very useful for optimizing ventilator settings during HFO.