[Negative-pressure pulmonary edema (NPPE)]. / Das pulmonale Negativdrucködem.

Negative-pressure pulmonary edema (NPPE) is a clinical entity of anaesthesiologic relevance, perioperatively caused by obstruction of the conductive airways (upper airway obstruction, UAO) due to laryngospasm in approx. 50% of the cases, its early recognition and treatment by the anaesthesist is mandatory. NPPE, also addressed as post-obstructive pulmonary edema (POPE) presents in most cases as a complex of symptoms with rapid onset, consisting of acute respiratory failure with dyspnea, tachypnea, and strained respiratory efforts. Additional signs are paradoxe ventilation, pink frothy sputum, stridor, and severe agitation. UAO produce extreme reduction of intrathoracic pressure during spontaneous ventilation, consecutively causing increase in venous return to the right ventricle and in intrathoracic blood volume, resulting in elevated hydrostatic pressures and interstitial transudation of fluids. Partially due to largely differing criteria used for diagnosis, opinions about incidence and prevalence of NPPE are unhomogenous in medical literature. It has been shown that generation of NPPE is not only limited to patients being intubated and ventilated, but occurs also in patients requiring higher fractions of oxygen.

The dependency of expiratory airway collapse on pump system and flow rate in liquid ventilated rabbits.

PURPOSE: To evaluate the influence of pump system and flow pattern on expiratory airway collapse (EAC) in total perfluorocarbon ventilation. - METHODS: Prospective, controlled, randomized animal trial for determination of (1) post-mortem changes by repeated expiration procedures (EP) with a constant flow piston pump (PP) before and after sacrifice (n = 8 rabbits), (2) differences between pump systems by subjecting animals to both PP and roller pump (RP) circuits for expiration (n = 16 rabbits). EP were performed using a servo-controlled shut-off at airway pressures < 25 cm H subset 2O randomly with either pump at different flows. - RESULTS: Expired volumes before and after sacrifice were not significantly different. PP and RP revealed identical mean flows, while significantly more liquid was drained using PP (p<0.05). Increasing differences towards higher flow rates indicated profound flow pulsatility in RP. - CONCLUSIONS: (1) post-mortem changes in expired volumes are not significant, (2) EAC is related to flow rate and pump system; (3) relationship between expiratory flow rate and drainable liquid volume is linear inverse; (4) PP provides higher drainage than RP. - SUMMARY STATEMENT: Expiratory airway collapse is related to flow rate and pump system, post mortem changes in expirable volumes are not significant. Relationship between expiratory flow rate and drainable liquid volume is linear inverse, piston pump expiration provides higher drainage volumes than roller pump expiration.

[Extracorporeal membrane oxygenation (ECMO) in adults]. / Extrakorporale Membranoxygenierung (ECMO) im Erwachsenenalter.

Despite ongoing discussions, ECMO (extracorporeal membrane oxygenation) has become an important part of treatment options in acute lung injury and ARDS (acute respiratory distress syndrome) even in adults. On the other hand, none of the two RCT (randomized controlled trial) studies resulted in reduced letality of the artificial lung therapy when compared to convention treatment. Both authors concluded, that ECMO is not recommended in ARDS. Meanwhile experience with ECMO in adults is extensive in various institutions worldwide, exceeding 1000 patients by the end of 2001. Growing experience and improved technical equipment reduce the rate of technical complications substantially. However, for different reasons ECMO incidence in adults is progressively decreasing in recent years. Inclusion and exclusion criteria vary among different ECMO centers. Potential reversibility of lung injury and persisting life-threatening gas exchange disorder under maximal conventional therapy are commonly seen as requirements for ECMO therapy. ECMO criteria are Murray lung injury score >3.5 (chest x-ray, PaO2/FiO2-index, static compliance Cstat, PEEP), Morel-classification >3 (chest x-ray, AaDO2/FiO2-index, Cstat, PEEP), AaDO2 >600mmHg, intrapulmonal shunt QS/QT >30%, and increase in extravascular lung water >15 ml/kg bodyweight. Commonly accepted absolute contraindications are (1) severely consuming disorders with poor prognosis, (2) CNS damage with poor prognosis, (3) advanced chronic lung disorders, and (4) progressive multiple organ failure. Relative contraindications are immunosuppresion, active bleeding, age over 60 years, and days on mechanical ventilation. In our experience, early contact to an ECMO reference center can optimise early identification of patients which benefit from ECMO, as well as treatment and transportation modalities, and improves outcome. Due to high technical and personal requirements and decreasing incidence in the adult sector, ECMO should be limited to a small number of reference centers with substantial experience in extracorporeal circulation.

Development and application of a double-piston configured, total-liquid ventilatory support device.

OBJECTIVE: Perfluorocarbon liquid ventilation has been shown to enhance pulmonary mechanics and gas exchange in the setting of respiratory failure. To optimize the total liquid ventilation process, we developed a volume-limited, time-cycled liquid ventilatory support, consisting of an electrically actuated, microprocessor-controlled, double-cylinder, piston pump with two separate limbs for active inspiration and expiration. DESIGN: Prospective, controlled, animal laboratory study, involving sequential application of conventional gas ventilation, partial ventilation (PLV), and total liquid ventilation (TLV). SETTING: Research facility at a university medical center. SUBJECTS: A total of 12 normal adult New Zealand rabbits weighing 3.25+/-0.1 kg. INTERVENTIONS: Anesthestized rabbits were supported with gas ventilation for 30 mins (respiratory rate, 20 cycles/min; peak inspiratory pressure, 15 cm H2O; end-expiratory pressure, 5 cm H2O), then PLV was established with perflubron (12 mL/kg). After 15 mins, TLV was instituted (tidal volume, 18 mL/kg; respiratory rate, 7 cycles/min; inspiratory/expiratory ratio, 1:2 cycles/min). After 4 hrs of TLV, PLV was re-established. MEASUREMENTS AND MAIN RESULTS: Of 12 animals, nine survived the 4-hr TLV period. During TLV, mean values +/- SEM were as follows: PaO2, 363+/-30 torr; PaCO2, 39+/-1.5 torr; pH, 7.39+/-0.01; static peak inspiratory pressure, 13.2+/-0.2 cm H2O; static endexpiratory pressure, 5.5+/-0.1 cm H2O. No significant changes were observed. When compared with gas ventilation and PLV, significant increases occurred in mean arterial pressure (62.4+/-3.5 torr vs. 74.0+/-1.2 torr) and central venous pressure (5.6+/-0.7 cm H2O vs. 7.8+/-0.2 cm H2O) (p < .05). CONCLUSIONS: Total liquid ventilation can be performed successfully utilizing piston pumps with active expiration. Considering the enhanced flow profiles, this device configuration provides advantages over others.

Reduced platelet activation and thrombosis in extracorporeal circuits coated with nitric oxide release polymers.

OBJECTIVE: To determine whether the use of nitric oxide (NO)-releasing polymers coated onto the inner surface of extracorporeal circuits can reduce platelet consumption and activation in the absence of systemic heparinization using a rabbit model of venovenous extracorporeal circulation. DESIGN: Prospective, controlled trial. SETTING: Research laboratory at an academic medical institution. SUBJECTS: New Zealand White Rabbits. INTERVENTIONS: Anesthetized, tracheotomized, and ventilated New Zealand White rabbits were injected with freshly prepared, 111In(oxine)3 labeled single donor platelets through the external jugular vein. After baseline measurements, these animals were placed on venovenous extracorporeal circulation through a 1-m control circuit or NO test circuit for 4 hrs at a blood flow rate of 109-118 mL/min via roller pump. Four groups were studied: systemically heparinized control circuits, systemically heparinized NO test circuits, nonheparinized control circuits, and nonheparinized NO test circuits. Platelet counts, fibrinogen levels, and plasma free indium levels were measured hourly. Circuits were rinsed and retained for gamma counting after the 4-hr run or when the circuit clotted. Four animals, one from each group, did not receive radiolabeled platelets so that the circuits could be preserved for scanning electron microscopic examination after the 4-hr study. MEASUREMENTS AND MAIN RESULTS: Platelet consumption was significantly reduced in both the heparinized and nonheparinized NO test groups when compared with the controls (p < .0001 and p < .0004, respectively). Platelet adhesion to the extracorporeal circuits was significantly reduced in the nonheparinized test circuits when compared with the controls (p < .05). Scanning electron microscopic examination of the circuits revealed that in the absence of heparin and in the presence of a NO-releasing surface, platelets retained their spherical nonactivated shape. CONCLUSIONS: The incorporation of NO into the surface of extracorporeal circuits reduces platelet consumption and eliminates the need for systemic heparinization in a rabbit model of extracorporeal circulation.

Effect of blood flow rate on thrombogenesis in a rabbit extracorporeal circulation model.

Blood flow is believed to affect the thrombogenicity of extracorporeal circulation (ECC). The purpose of this study was to look at the relationship between blood flow and thrombogenicity in a rabbit model of ECC. Rabbits were anesthetized and systematically heparinized. Bilateral jugular cannulation was performed, and the animals were placed on venovenous ECC. The circuits were composed of 1 m of 1/4 inch size surgical grade polyvinylchloride (PVC) tubing. ECC was maintained for 4 hours. Three experimental groups were studied: a high flow group (n=7; flow rate: 30 ml/min/Kg), low flow group (n=7; flow rate: 10 ml/mg/Kg), and no ECC group (n=7). Platelet count, fibrinogen concentration, PaO2/FiO2, and postmortem findings were evaluated. Platelet consumption was higher with high flow, and fibrinogen consumption was higher with low flow.