The Role of Platelets in Malarial Acute Lung Injury and Acute Respiratory Distress Syndrome: A World of Possibilities.

In recent decades our understanding of platelets’ role in immune response has increased. Traditionally platelets were considered as bleeding-stopping and thrombosis-causing cells. In recent years the platelets’ role in malarial innate and adaptive immune responses is being recognized. Platelets play critical role in pathogenesis of malaria infection leading to variety of outcomes. It is being realized that platelets play dual role in case of malaria (i) by preventing early stage exponential growth of parasitemia (ii) promoting exaggerated immune responses later. Platelets role in pathogenesis of severe and cerebral malaria has been widely studied. However their role in malaria related acute lung injury and respiratory distress has gained less attention. Recently the presence of active megakaryocytes and proplatelets have been explained in human lungs. Simultaneously, the platelets role in pathogenesis of acute lung injury and respiratory distress (ALI/ARDS) was also recognized. This gives a hint that there is a possible association of platelets with malaria related respiratory diseases as well. ALI/ARDS are characterized by lung edema due to increased permeability of the alveolar-capillary barrier and subsequent impairment of arterial oxygenation. In this review we have attempted to establish the importance of role of platelets in malaria related acute lungs injury and malaria acute respiratory distress syndrome and try to explain the underlying mechanism of this process. In ALI/ARDS, including those caused by malaria, platelets participate sequestration to the vascular bundle facilitating the recruitment of immune cells viz. neutrophils. Additionally, they secrete or induce the secretion of chemokines that result into vascular damage.

Clinical Meaning of Early Oxygenation Improvement in Severe Acute Respiratory Distress Syndrome under Prolonged Prone Positioning

BACKGROUND/AIMS: Ventilating patients with acute respiratory distress syndrome (ARDS) in the prone position has been shown to improve arterial oxygenation, but prolonged prone positioning frequently requires continuous deep sedation, which may be harmful to patients. We evaluated the meaning of early gas exchange in patients with severe ARDS under prolonged (> or = 12 hours) prone positioning. METHODS: We retrospectively studied 96 patients (mean age, 60.1 +/- 15.6 years; 75% men) with severe ARDS (PaO2/FiO2 or = 20 mmHg and decreases in PaCO2 of > or = 1 mmHg, respectively, 8 to 12 hours after first placement in the prone position. RESULTS: The mean duration of prone positioning was 78.5 +/- 61.2 hours, and the 28-day mortality rate after MICU admission was 56.3%. No significant difference in clinical characteristics was observed between PaO2 and PaCO2 responders and non-responders. The PaO2 responders after prone positioning showed an improved 28-day outcome, compared with non-responders by Kaplan-Meier survival estimates (p < 0.05 by the log-rank test), but the PaCO2 responders did not. CONCLUSIONS: Our results suggest that the early oxygenation improvement after prone positioning might be associated with an improved 28-day outcome and may be an indicator to maintain prolonged prone positioning in patients with severe ARDS.

Ajuste a la ventilación mecánica guiado por curvas presión-volumen de flujo lento en pacientes con síndrome de distress respiratorio agudo e injuria pulmonar aguda / Mechanical ventilatory parameters guided by the low flow pressure-volume curve in patients with acute lung injury/acute respiratory distress syndrome

Background: Mechanical ventilation may contribute to lung injury and then enhance systemic inflammation. Optimal ventilatory parameters such as tidal volume (V T) and positive end expiratory pressure (PEEP) can be determined using different methods. Low flow pressure volume (P/V-LF) curve is a useful tool to assess the respiratory system mechanics and set ventilatory parameters. Aim: To set V T and PEEP according P/V-LF curve analysis and evaluate its effects on gas exchange and hemodynamic parameters. Materials and methods: Twenty seven patients underwent P/V-LF within the first 72 hours of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). P/V-LF curves were obtained from the ventilator and both lower and upper inflexion points determined. Gas exchange and hemodynamic parameters were measured before and after modifying ventilator settings guided by P/V-LF curves. Results: Ventilatory parameters set according P/V-LF curve, led to a rise of PEEP and reduction of V T: 11.6±2.8 to 14.1±2.1 cm H2O, and 9.7±2.4 to 8.8±2.2 mL/kg (p <0.01). Arterial to inspired oxygen fraction ratio increased from 158.0±66 to 188.5±68.5 (p <0.01), and oxygenation index was reduced, 13.7±8.2 to 12.3±7.2 (p <0.05). Cardiac output and oxygen delivery index (IDO2) were not modified. Demographic data, gas exchange improvement and respiratory system mechanics showed no significant difference between patients with extra-pulmonary and pulmonary ALI/ARDS. There was no evidence of significant adverse events related with this technique. Conclusion: P/V-LF curves information allowed us to adjust ventilatory parameters and optimize gas exchange without detrimental effects on oxygen delivery in mechanically ventilated ALI/ARDS patients.

Plasma soluble intercellular adhesion molecule-1 (sICAM-1) in pediatric ARDS during high frequency oscillatory ventilation: a predictor of mortality.

Soluble intercellular adhesion molecule-1 (sICAM-1), an important adhesion molecule that mediates leukocyte-endothelial interaction, has been identified as a marker for the outcome of acute respiratory tract infection. We postulate that plasma ICAM-1 may be a valuable marker for both biological and clinical severity of acute respiratory distress syndrome (ARDS). Sixteen pediatric patients (> 1 month and < 15 years of age) diagnosed with ARDS were recruited from the Pediatric Intensive Care Unit at King Chulalongkorn Memorial University Hospital, Bangkok. The patients were randomized to receive either high frequency oscillatory ventilation (HFOV) or conventional mechanical ventilation. Plasma sICAM-1 was measured by enzyme linked immunosorbent assay (ELISA) on days 1, 3, 5 and 7 of ARDS. Plasma sICAM-1 levels in survivors and non-survivors of the HFOV and conventional treatment groups were compared. Nine and 7 patients constituted the control group receiving conventional treatment and HFOV group, respectively. Overall nine patients survived. The patients in the HFOV group had a better chance of survival compared to the controls (71% versus 31.5%), but it was not statistically significant (p = 0.2). The overall mortality was 45.7%. The mean plasma sICAM-1 levels (n = 13/16) were significantly elevated among non-survival patients as compared to survival patients at all time points, which indicates that an unfavorable outcome in ARDS is related to the degree of epithelial and endothelial alveolar cell injury. The elevation of plasma slCAM-1 on day 3 provided the best predictor of mortality (likelihood ratio 11.9, p < 0.001). It was concluded that HFOV facilitated a potentially better outcome compared to conventional treatment and it was associated with less lung injuries evidenced by lower plasma sICAM-1.

The Role of the Lactate Dehydrogenase and the Effect of Prone Position during Ventilator-induced Lung Injury

To examine the impact of lactate dehydrogenase (LDH) as an early marker of ventilator-induced lung injury (VILI) and the effect of prone position during the VILI, we ventilated 28 normal white rabbits (10 supine, 10 prone, 8 controls) for 6 hr or until PaO2/FIO2 ratio was<200 mmHg. We applied an identical injurious ventilatory pattern (peak inspiratory pressure of 35 cmH2O with a PEEP of 3 cmH2O, I:E ratio of 1:2, and FIO2 of 0.40) in the supine and prone group. VILI was assessed by oxygenation, gravimetric analysis and histologic grading. Serum levels of LDH progressively increased significantly during the VILI (supine and prone groups) as compared with controls. There was a significant negative correlation between oxygenation and LDH levels (r=-0.619, p<0.001). Wet weight/dry weight ratios (WW/DW) and histologic scores for dependent regions were significantly higher in the supine than the prone group. There were no differences in WW/DW and histologic scores for nondependent regions between the supine and prone group. These findings suggest that serum LDH levels might be an early marker of severity of lung injury. The prone position resulted in a less severe and more homogenous distribution of VILI.

Oxido nítrico inhalado: una modalidad en el tratamiento de SIRPA / Inhaled nitric oxide: a modality in the treatment of adult respiratory distress syndrome (ARDS)

Presentamos el caso de un paciente con síndrome de insuficiencia respiratoria progresiva del adulto (SIRPA) refractario a manejo ventilatorio convencional, el cual dentro de sus parámetros hemodinámicos mostraba hipertensión pulmonar grave e incremento del cortocircuito intrapulmonar. Se manejó con oxido nítrico inhalado con lo cual presentó mejoría en la hipertensión pulmonar, cortocircuito intrapulmonar e intercambio gaseoso. Se revisa la literatura recomendaciones en relación al uso de oxido nítrico en el paciente con SIRPA

Mejoría de la función respiratoria con una técnica de apertura pulmonar (AP) / Improvement of respiratory function with a technique of open lung

Objetivo: La ventilación mecánica (VM) ha demostrado ser una terapeútica útil en pacientes con compromiso de la función respiratoria. Son múltiples las complicaciones asociadas a los modos convencionales de VM. Están en desarrollo técnicas para disminuir la incidencia de efectos adversos. El objetivo del trabajo es evaluar la técnica ventilatoria denominada APERTURA PULMONAR (AP). (Open Lung Concept. Intens Care Med. 18:319-321, 1992). Pacientes y métodos: Se incorporaron en forma prospectiva y randomizada los pacientes que requirieron VM. Se usaron Siemmens Servo 300 y 900C. Se utilizaron tres modos ventilatorios: Presión Control (PC), Volumen Control (VC), y AP (con parámetros iniciales VT 7-10 ml/kg, PEEP/Presión Inspiratoria Pico (PIP) de 5/25, e incrementos progresivos de 5 cm H20 hasta alcanzar 15/60 e inmediato descenso, posteriormente éste grupo fue ventilado en modo PC con los parámetros de PEEP/PIP de 5-10/25-30, VT 7-10 ml/kg, I:E de 1:1.3, con frec. resp. entre 10-15. La AP se repitió según criterio del equipo médico. Se usó la escala de Murray al ingreso para estratificar las muestras. Se efectuaron registros seriados de monitoreo respiratorio y gasométrico. Se compararon los valores de Pao2/Fio2 entre los diferentes modos ventilatorios. Resultados: Ingresaron 42 pacientes. Se efectuaron 505 monitoreos. En la tabla se observan las comparaciones de los valores de las Pao2/Fio2 generales entre los grupos y las Pao2/Fio2 según horas de VM y según valor de Murray. Conclusiones: el modo AP tuvo mejores índices de oxigenación, siendo más evidente con el transcurso del tiempo y en los pacientes con mayor injuria pulmonar

Inverse ratio ventilation in adult respiratory distress syndrome: an experimental study in dogs regarding gasometric and hemodynamic aspects

Cardiorespiratory values were measured in 14 mongrel dogs with adult respiratory distress syndrome (ARDS), before and following the pressure controlled inverse ratio ventilation (IRV) at an inspiratory to expiratory ratio of 2:1. After the administration of oleic acid, the dogs developed metabolic acidosis, arterial hypoxemia, decreased compliance and cardiac index. There were no significant changes in any hemodynamic or arterial blood gases with the institution of inverse ratio ventilation. We concluded that the IRV with I:E of 2:1 and respiratory ratio of 12 bpm did not improve the arterial blood gases in ARDS. We speculate that to get better oxygenation in this model of mechanical ventilation we'll need increase the respiratory ratio to decrease the expiratory time and provoke the intrinsic positive end expiration pressure (PEEP).