Acute Chest Syndrome

The purpose of this study is to determine whether a single infusion of tocilizumab is effective in reducing the time to successful weaning from both supplemental oxygen and any respiratory support, in pediatric and adult patients with sickle cell disease (SCD) during acute chest syndrome (ACS).

Feasibility and reliability of ultrasound in the inpatient hematology setting.

The investigators are evaluating the role of a low dose of tocilizumab in treating acute chest syndrome in patients with sickle cell disease. Tocilizumab inhibits interleukin-6 (IL-6) receptors and is used to treat rheumatoid arthritis and severe cytokine release syndrome, which can be seen with chimeric antigen receptor T-cell (CAR-T) therapy, and it is also authorized for treatment of COVID-19. Since IL-6 levels are elevated in the sputum of patients with acute chest syndrome, the investigators are hopeful that this will be an effective strategy. The investigators will be looking at how a low dose of tocilizumab affects oxygen status, clinical outcomes, and laboratory markers in patients admitted to the hospital with acute chest syndrome.

Background: Sickle cell disease is a genetic disorder of haemoglobin (which carries oxygen in red blood cells). The shape of sickle cell-patients' red blood cells is abnormal. Thus, red blood cells can be blocked in small vessels, responsible for painful crises due to a lack of downstream circulation. These crisis (acute vaso-occlusive crisis) require strong treatment based on morphine, and often require intensive care.However, treatment is often insufficiently effective. Patient can also experiment acute chest syndrome, a complication of vaso-occlusive crisis, which can be responsible for respiratory failure. In addition, patients with sickle cell disease frequently have kidney damage called sickle cell nephropathy, which in the early stages of the disease is responsible for renal hyperfiltration, meaning that the kidneys filter the blood more than necessary, with faster elimination of drugs. For example, it is known that higher doses of antibiotics must be used in these patients than in the general population for the same effectiveness. The hypothesis of the study is that morphine, a drug eliminated by kidneys, is underdosed in patients with sickle cell disease, which is responsible for the difficulties in achieving sufficient analgesia. Objective: To determine the glomerular filtration rate threshold for which it is necessary to prescribe higher doses of morphine in sickle cell patients with vaso-occlusive crisis. Methods: inclusion of 100 patients admitted to intensive care for an acute vaso-occlusive crisis or acute chest syndrome and receiving morphine. Within 24 hours of study inclusion, four morphine dosages will be performed, in parallel with a precise determination of the glomerular filtration rate by measuring the elimination rate of a tracer, 100% eliminated by the kidneys and injected at the start of the study. This tracer is iohexol, a contrast agent commonly used in radiology. Morphine underdosage will be interpretated regarding glomerular filtration rate. The effectiveness of analgesia and the amount of analgesics required will be also be analyzed. Outlook: At the end of this study, the investigators will be able to offer adapted doses of morphine for sickle cell patients in crisis, adapted to glomerular filtration rate, in the aim of personalizing analgesia.

Acute chest syndrome (ACS) is the leading cause of admission to intensive care and the leading cause of death in patients with sickle cell disease. Irrespective of the cause of ACS, there is an heterogeneity in pulmonary ventilation/perfusion ratios, leading to worsening of the disease. Efficiency of awake prone positioning (APP) in acute respiratory failure (ARF) was particularly highlighted during the COVID-19 pandemic. Several physiological factors contribute to this benefit including an improvement in ventilatory drive and gas exchange. The investigator hypothesize that APP could lead to clinical improvement in ACS in terms of oxygenation and ventilatory drive, by improving the heterogeneity of ventilation

Sickle cell disease (SCD) is characterized by recurrent vaso-occlusive pain crisis (VOC), which may evolve to acute chest syndrome (ACS), the most common cause of death among adult patients with SCD. Currently, there is no etiologic treatment to abort ACS. Therefore, management of ACS mostly involve a symptomatic approach including in routine, and as per recommendations, hydration, analgesics, supplemental oxygen, and transfusion. The polymerisation of sickle haemoglobin (HbS) is one major feature in the pathogenesis of vaso-occlusion. Current guidelines recommend red blood cell exchange transfusion (REX) in patients with severe ACS in order to improve oxygenation and reduce HbS concentration to blunt sickling. REX is often preferred over simple transfusion in this setting because it rapidly reduces HbS without raising final haematocrit. There are currently two methods for REX: manual (with sequential phlebotomies and transfusions) or automated (erythrocytapheresis). The former allows a sober use of red blood cell packs, while the latter achieves haematological targets (HbS and haematocrit) quickly and more consistently, but requires a special equipment and trained staff. As a result of inflammation and intravascular hemolysis, the plasma of patients with ACS may also contain several components that promote vaso-occlusion, lung injury and organ failure, including cytokines (e.g., IL-6), free haemoglobin and free haem. Conversely, it is depleted in haptoglobin and hemopexin, which normally bind to and clear cell-free haemoglobin. The addition of therapeutic plasma exchange to erythrocytapheresis during automated REX may therefore have a dual beneficial effect in patients with overt intravascular hemolysis: i) deplete the inflammatory mediators and products of hemolysis; ii) replete haptoglobin and hemopexin. REX modalities (automated vs manual) have not been tested during ACS. The hypothesis is that early-goal directed automated REX may accelerate the resolution of severe ACS as compared to manual REX.