NOSOCOMIAL PNEUMONIA AFTER CARDIAC SURGERY WITH CADIOPULMONARY BYPASS. Nosocomial
pneumonia (NP) is one of the most common complications of cardiac surgery with
cardiopulmonary bypass (CPB), its frequency according to various sources ranges from 2 to
10% . This complication is accompanied by higher mortality (0.7-4% in patients without
pneumonia vs. 25.1-28.2% in patients with pneumonia) , prolonged hospital stay and
increased economic costs. In the retrospective analysis of medical histories of patients
operated on CPB for 2020, 2021 and 2022, 3 main risk factors for the development of NP in
the postoperative period were identified: time of CPB ≥ 96 minutes, duration of
mechanical ventilation ≥ 14 hours, and the presence of atrial fibrillation (AF) before
surgery. STUDY NATURE In relation to medical procedures, this study is observational. The
examination and treatment of patients will be carried out in accordance with the approved
standards of medical care for the respective diseases. In this study, no experimental or
unregistered (not approved for use) medical or diagnostic procedures on the territory of
the Russian Federation will be carried out. STUDY TYPE Single-center, prospective,
double-blind, randomized, controlled, parallel group study. STUDY OBJECTIVES PRIMARY
OBJECTIVE OF THE STUDY To test the hypothesis that inhalation of NO 200 ppm prevents the
development of NP in patients after cardiac surgery under CPB and has a positive effect
on the structural and functional state of the external respiration.
SECONDARY OBJECTIVES OF THE STUDY
To test the hypothesis that inhalation of NO 200 ppm twice a day for 30 minutes for
5 days is safe for patients.
To test the hypothesis that prophylactic inhalation of NO 200 ppm twice a day for 30
minutes increases the duration of manifestation of nosocomial pneumonia (in case of
its development) after cardiac surgery under CPB.
To test the hypothesis that prophylactic inhalation of NO 200 ppm twice a day for 30
minutes reduces the time of resolution of NP (in case of its development) after
cardiac surgery under CPB.
To assess the differences in pulmonary function according to the 6-minute walk test
(6MWT), spirometry and ergospirometry and their dynamics in the main and control
groups.
To assess the morphological picture of the lungs and its dynamics according to lung
ultrasound in the main and control groups.
To compare the level of acute phase reactants and their dynamics in the main and
control groups.
To compare plasma levels of surfactant proteins SP-D and sRAGE and their dynamics in
the main and control groups.
RATIONALE FOR RANDOMIZATION There is currently no convincing evidence of benefits or
harms of NO inhalation as part of the prevention of NP after cardiac surgery with CPB.
Thus, there is no reason to believe that randomization to study groups creates additional
risks / benefits for patients. Nevertheless, regardless of the results of randomization,
the decision on the possibility of prophylactic NO inhalation after cardiac surgery in
each case will be made by a special medical commission consisting of a cardiac surgeon,
anesthesiologist and cardiologist, immediately after the patient is enrolled in the
study.
PATIENT RANDOMIZATION Patients eligible for this study will be randomized to the
intervention group (NO group) and Control group in a 1: 1 ratio according to the
randomization sequence generated by a computer program with random numbers by 80 people
in each group. Patients will be randomized immediately after screening and signing the
informed consent. Patients in both groups will not receive NO outside of the study
protocol until discharged from the hospital. Patient randomization will be performed by a
non-blinded NO delivery investigator who is not involved in the clinical management of
the patient and the evaluation of treatment outcomes. Patients in the intervention group
will receive inhaled NO therapy at a dose of 200 ppm 2 times a day for 5 days or until
pneumonia is detected. In the control group, instead of inhaled NO therapy, patients will
receive "Sham treatment": similar equipment and observation protocol during the
intervention will be used as in the main group, but NO will not be added to the delivered
gas mixture. BLINDING The gas supply systems will look the same for patients of both NO
group and Control group. Patients, treating physicians, investigators and other
professionals involved in the interpretation of the results will not be aware of the
nature of the therapy until the end of the study. The investigating doctor who is
responsible for the delivery and monitoring of the investigated gas will remain unblinded
and will be responsible for blinding the gas delivery systems, monitoring and securing
the delivery, and maintaining the randomization codes. Randomization codes will be sealed
in sequentially numbered opaque envelopes. The sequential envelope numbers will serve as
randomization numbers that will be recorded in patient's case report form (CRF) and used
when necessary, for example, to treat complications. DOSAGE REGIMEN AND DURATION OF
THERAPY When choosing the dose and timing of NO exposure, clinicians should be guided by
2 basic principles:
The dose of NO used and its exposure time must be safe for patients;
The dose of NO used and its exposure time must be sufficient to provide potential
preventive effects. NO dosing guidelines for the prevention of pneumonia after
cardiac surgery with CPB have not currently been developed, however, there is
extensive data from experimental and clinical studies indicating the potential
efficacy of a gas concentration of 200 ppm and an exposure time of 30 minutes, which
will be implemented in the study. The safety of using NO for humans in doses of
160-200 ppm for 15-30 minutes 2 to 5 times a day has been demonstrated in a number
of clinical studies, including in pregnant women and newborns. The absence of toxic
effects of NO at a dose of 200 ppm has been proven on cultured skin fibroblasts,
monocytes, macrophages and pulmonary epithelium. Most researchers emphasize the
efficacy of intermittent multiple high-dose (160-200 ppm) NO therapy with an average
duration of each inhalation for 30 minutes. NO DELIVERY After screening and signing
the informed consent, patients will be randomized into one of the study groups: a
control group with sham treatment and a study group, in which participants will
receive inhalation of NO 200 ppm for 30 minutes twice a day for 5 days after
extubation and transfer from the intensive care unit. NO delivery will be carried
out using a semi-open circuit. The source of NO is the certified device, which
synthesizes NO from atmospheric air using the method of plasma-chemical synthesis
directly during therapy. The supply line for the studied gas is built into the
supply line for the carrier gas (atmospheric air), the flow of which is provided by
a compressor with a maximum flow of 18 l/min, which can be adjusted. The carrier gas
flow and NO synthesis rate will be adjusted automatically so that the NO
concentration is up to 200 ppm. Next, the gas mixture enters a 3-liter reservoir
bag, from where the patient actively breathes it in. To separate the inspiratory and
expiratory parts, inhalation and exhalation valves are provided in the circuit. To
create an air tight seal with the circuit and patient's airways, correct sized air
cushion anesthesia masks will be used. Gas is continuously sampled from the proximal
end of the inspiratory part of the circuit to determine the concentration of NO and
NO2 in it. MetHb levels during NO inhalation will be estimated continuously using a
peripheral pulse oximeter with fractional saturation capability. During NO therapy,
MetHb levels will be maintained at <5%. NO undergoes a chemical reaction to form
NO2, which is an extremely toxic gas and can cause airway inflammation and lung
tissue injury. This study regulates the control and maintenance of inhaled NO2
levels below 3 ppm. During NO therapy, vital functions and safety will be assessed
immediately before the initiation of the session, after 15 minutes of NO and after
its completion (Heart Rate, Blood Pressure, Respiratory Rate, Oxygen Saturation,
MetHb). In addition, as part of the exploratory endpoint study, exhaled NO levels
will be measured immediately before and after inhalation, 10 and 20 minutes after
the end of inhalation. Patients from the control group will undergo sham-treatment,
the algorithm of which is similar to inhalation in the main group, but NO will not
be added to the gas mixture. SUMMARY OF KNOWN AND POTENTIAL RISKS AND BENEFITS OF
NO-THERAPY NO undergoes a chemical reaction to form NO2. NO2 is an extremely toxic
gas that can cause airway inflammation and lung tissue injury. Protocols in use
today require that inhaled NO2 levels should be maintained below 3 ppm during NO
therapy. The rate of NO2 formation depends on the concentration of NO and O2 in the
inhaled gas-air mixture. This fact is important: sources with high concentrations of
NO should be avoided; NO and inspiratory fraction of O2 (FiO2) should be used in the
minimum clinically acceptable doses. During bench tests of the delivery system, NO2
concentration did not exceed 3 ppm when 200 ppm NO was supplied against the
background of FiO2 = 100% (due to the use of a chemical sorbent), however, the
minimum sufficient inspiratory fraction of O2 will be used when carrying out the
study. NO oxidizes hemoglobin (Hb) (Fe+2) to form (MetHb) (Fe+3), which is unable to
transport and release oxygen into the tissue and, as a result, can cause tissue
hypoxia. Cyanosis is observed when MetHb levels approach 15-20%. The Institutional
Review Board for this study recommended monitoring and maintaining MetHb levels
below 5% of total hemoglobin concentration. MetHb levels will be continuously
monitored using a peripheral pulse oximeter with the ability to measure fractional
saturation (non-invasive pulse co-oximetry). If MetHb levels exceed 5% of the total
Hb concentration, NO delivery will be stopped. An increase in MetHb levels > 30% as
a critical incident in the study requires intravenous administration of methylene
blue in 0.1-0.2 ml/kg of 1% solution (1-2 mg/kg). After half of the patients are
recruited and preliminary statistical analysis is completed, a report on possible
complications associated with the potentially negative effects of NO will be
submitted. OBSERVATION PERIOD Monitoring of patients and registration of study data
will be carried out until discharge from the hospital. The expected length of
hospital stay after uncomplicated cardiac surgery will be approximately 2 weeks. If
complications occur during the perioperative period, patients will be monitored
until the event resolves/stabilizes. TERMINATION OR SUSPENSION OF THE CLINICAL STUDY
The study will be terminated at the initiative of the study sponsor if, based on the
results of an interim analysis or current monitoring, the risk of adverse outcomes
in the NO-therapy group clinically or statistically significantly exceeds the
similar risk in the control group..
Individual patient's participation in the study will be terminated prematurely in
accordance with the following criteria:
Patient decision (withdrawal of informed consent).
Increased MetHb> 5% of hemoglobin level;
Increase in NO2 level> 3 ppm;
Intolerance to the proposed modality of therapy.
