Inhaled milrinone in cardiac surgical patients: a pilot randomized controlled trial of jet vs. mesh nebulization

Novel inhaled pulmonary vasodilators in adult cardiac surgery: a scoping review

PURPOSE

Pulmonary hypertension (PH) is a common cause of postoperative mortality in cardiac surgery that is commonly treated with conventional inhaled therapies, specifically nitric oxide and prostacyclin. Alternative therapies include inhaled milrinone and levosimendan, which are receiving more research interest and are increasing in clinical use as they may cut costs while allowing for easier administration. We sought to conduct a scoping review to appraise the evidence base for the use of these two novel inhaled vasodilators as an intervention for PH in cardiac surgery.

SOURCE

We searched Embase and MEDLINE for relevant articles from 1947 to 2022.

PRINCIPAL FINDINGS

We identified 17 studies including 969 patients. The included studies show that inhaled milrinone and levosimendan are selective pulmonary vasodilators with potential benefits ranging from ease of weaning from cardiopulmonary bypass to reduction in ventricular dysfunction. Nevertheless, high-quality data are limited, and study design and comparators are extremely heterogeneous, limiting the potential validity and generalizability of findings.

CONCLUSION

The findings of this scoping review suggest that milrinone and levosimendan may be effective alternatives to current inhaled therapies for cardiac dysfunction in the setting of PH. Nevertheless, randomized trials have focused on specific agents and consistent outcome measures are needed to better validate the early-stage promise of these agents.

STUDY REGISTRATION

Open Science Framework ( https://osf.io/z3k6f/ ); first posted 21 July 2022.

The perioperative use of inhaled prostacyclins in cardiac surgery: a systematic review and meta-analysis

PURPOSE

Perioperative pulmonary hypertension (PH) is an independent risk factor for morbidity and mortality in cardiac surgery. While inhaled prostacyclins (iPGI2s) are an established treatment of chronic PH, data on the efficacy of iPGI2s in perioperative PH are scarce.

METHODS

We searched PubMed, Embase, the Web of Science, CENTRAL, and the grey literature from inception until April 2021. We included randomized controlled trials investigating the use of iPGI2s in adult and pediatric patients undergoing cardiac surgery with an increased risk of perioperative right ventricle failure. We assessed the efficacy and safety of iPGI2s compared with placebo and other inhaled or intravenous vasodilators with random-effect meta-analyses. The primary outcome was mean pulmonary artery pressure (MPAP). Secondary outcomes included other hemodynamic parameters and mortality.

RESULTS

Thirteen studies were included, comprising 734 patients. Inhaled prostacyclins significantly decreased MPAP compared with placebo (standardized effect size, 0.46; 95% confidence interval [CI], 0.11 to 0.87; P = 0.01) and to intravenous vasodilators (1.26; 95% CI, 0.03 to 2.49; P = 0.045). Inhaled prostacyclins significantly improved the cardiac index compared with intravenous vasodilators (1.53; 95% CI, 0.50 to 2.57; P = 0.004). In contrast, mean arterial pressure was significantly lower in patients treated with iPGI2s vs placebo (-0.39; 95% CI, -0.62 to 0.16; P = 0.001), but higher than in patients treated with intravenous vasodilators (0.81; 95% CI, 0.29 to 1.33; P = 0.002). With respect to hemodynamics, iPGI2s had similar effects as other inhaled vasodilators. Mortality was not affected by iPGI2s.

CONCLUSION

The results of this systematic review and meta-analysis show that iPGI2s improved pulmonary hemodynamics with similar efficacy as other inhaled vasodilators, but caused a significant small decrease in arterial pressure when compared with placebo, indicating spill-over into the systemic circulation. These effects did not affect clinical outcomes.

STUDY REGISTRATION DATE

PROSPERO (CRD42021237991); registered 26 May 2021.

Comparison of the efficacy of inhaled versus infused milrinone in the management of persistent pulmonary hypertension of the newborn in resource-limited settings: A randomized clinical trial

BACKGROUND

The standard treatment for persistent pulmonary hypertension of the newborn (PPHN) is inhaled nitric oxide (iNO), which is not available in Iran. Consequently, other drugs, such as milrinone, are prescribed. So far, no study has investigated the effectiveness of inhaled milrinone in the management of PPHN. The present study aimed to improve the management of PPHN in the absence of iNO.

METHODS

In this randomized clinical trial, neonates with PPHN, admitted to the neonatal intensive care unit of Hazrat Ali-Asghar and Akbar-Abadi hospitals, were treated with intravenous dopamine infusion and randomly divided into two groups, receiving milrinone through inhalation or infusion rout. The neonates were evaluated by Doppler echocardiography, clinical examinations, and oxygen demand test. The neonates were also evaluated for the clinical symptoms and mortality in the follow-up.

RESULTS

A total of 31 infants, with a median age of 2 days (interquartile range = 4), were included in this study. There was a significant decrease in the peak systolic and mean pulmonary arterial pressure in both inhalation and infusion groups following milrinone administration, with no significant difference between the groups (p = 0.584 and p = 0.147, respectively). There was no significant difference between the two groups regarding the mean systolic blood pressure before and after treatment. Additionally, diastolic blood pressure was significantly lower in the infusion group after treatment (p = 0.020); however, the amount of reduction was not significantly different between the groups (p = 0.928). Overall, 83.9% of the participants achieved full recovery, 75% of whom were in the infusion group and 93.3% in the inhalation group (p = 0.186).

CONCLUSION

Milrinone inhalation can have similar effects to milrinone infusion as an adjunct treatment in the management of PPHN. Also, infusion and inhalation of milrinone showed similar safety.

Inhaled milrinone in cardiac surgical patients: pharmacokinetic and pharmacodynamic exploration

Mean arterial pressure to mean pulmonary arterial pressure ratio (mAP/mPAP) has been identified as a strong predictor of perioperative complications in cardiac surgery. We therefore investigated the pharmacokinetic/pharmacodynamic (PK/PD) relationship of inhaled milrinone in these patients using this ratio (R) as a PD marker. Following approval by the ethics and research committee and informed consent, we performed the following experiment. Before initiation of cardiopulmonary bypass in 28 pulmonary hypertensive patients scheduled for cardiac surgery, milrinone (5 mg) was nebulized, plasma concentrations measured (up to 10 h) and compartmental PK analysis carried out. Baseline (R₀) and peak (R_max) ratios as well as magnitude of peak response (∆_Rmax-R0) were measured. During inhalation, individual area under effect-time (AUEC) and plasma concentration-time (AUC) curves were correlated. Potential relationships between PD markers and difficult separation from bypass (DSB) were explored. In this study, we observed that milrinone peak concentrations (41-189 ng ml^-1) and Δ_Rmax-R0 (- 0.12-1.5) were obtained at the end of inhalation (10-30 min). Mean PK parameters agreed with intravenous milrinone published data after correction for the estimated inhaled dose. Paired comparisons yielded a statistically significant increase between R₀ and R_max (mean difference, 0.58: 95% CI 0.43-0.73; P < 0.001). Individual AUEC correlated with AUC (r = 0.3890, r² = 0.1513; P = 0.045); significance increased after exclusion of non-responders (r = 4787, r² = 0.2292; P = 0.024). Individual AUEC correlated with ∆R_max-R0 (r = 5973, r² = 0.3568; P = 0.001). Both ∆R_max-R0 (P = 0.009) and CPB duration (P < 0.001) were identified as predictors of DSB. In conclusion, both magnitude of peak response of the mAP/mPAP ratio and CPB duration were associated with DSB.

Pulmonary Vasodilator Response of Combined Inhaled Epoprostenol and Inhaled Milrinone in Cardiac Surgical Patients

BACKGROUND

Pulmonary hypertension (PH) and right ventricular (RV) dysfunction are major complications in cardiac surgery. Intraoperative management of patients at high risk of RV failure should aim to reduce RV afterload and optimize RV filling pressures, while avoiding systemic hypotension, to facilitate weaning from cardiopulmonary bypass (CPB). Inhaled epoprostenol and inhaled milrinone (iE&iM) administered in combination before CPB may represent an effective strategy to facilitate separation from CPB and reduce requirements for intravenous inotropes during cardiac surgery. Our primary objective was to report the rate of positive pulmonary vasodilator response to iE&iM and, second, how it relates to perioperative outcomes in cardiac surgery.

METHODS

This is a retrospective cohort study of consecutive patients with PH or RV dysfunction undergoing on-pump cardiac surgery at the Montreal Heart Institute from July 2013 to December 2018 (n = 128). iE&iM treatment was administered using an ultrasonic mesh nebulizer before the initiation of CPB. Demographic and baseline clinical data, as well as hemodynamic, intraoperative, and echocardiographic data, were collected using electronic records. An increase of 20% in the mean arterial pressure (MAP) to mean pulmonary artery pressure (MPAP) ratio was used to indicate a positive response to iE&iM.

RESULTS

In this cohort, 77.3% of patients were responders to iE&iM treatment. Baseline systolic pulmonary artery pressure (SPAP) (odds ratio [OR], 1.63; 95% confidence interval [CI], 1.24-2.16 per 5 mm Hg; P = .0006) was found to be a predictor of pulmonary vasodilator response, while a European System for Cardiac Operative Risk Evaluation (EuroSCORE II) score >6.5% was a predictor of nonresponse to treatment (≤6.5% vs >6.5% [reference]: OR, 5.19; 95% CI, 1.84-14.66; P = .002). Severity of PH was associated with a positive response to treatment, where a higher proportion of responders had MPAP values >30 mm Hg (42.4% responders vs 24.1% nonresponders; P = .0237) and SPAP values >55 mm Hg (17.2% vs 3.4%; P = .0037). Easier separation from CPB was also associated with response to iE&iM treatment (69.7% vs 58.6%; P = .0181). A higher proportion of nonresponders had a very difficult separation from CPB and required intravenous inotropic drug support compared to responders, for whom easy separation from CPB was more frequent. Use of intravenous inotropes after CPB was lower in responders to treatment (8.1% vs 27.6%; P = .0052).

CONCLUSIONS

A positive pulmonary vasodilator response to treatment with a combination of iE&iM before initiation of CPB was observed in 77% of patients. Higher baseline SPAP was an independent predictor of pulmonary vasodilator response, while EuroSCORE II >6.5% was a predictor of nonresponse to treatment.

Inhaled Epoprostenol and Milrinone Effect on Right Ventricular Pressure Waveform Monitoring

BACKGROUND

Pulmonary hypertension (PH) and right ventricular (RV) dysfunction are major complications in cardiac surgery. This study aimed to evaluate the change in RV pressure waveform in patients receiving a combination of inhaled epoprostenol and inhaled milrinone (iE&iM) before cardiopulmonary bypass (CPB) and to assess the safety of this approach with a matched case-control group.

METHODS

A prospective single-centre cohort study of adult patients undergoing cardiac surgery administered iE&iM through an ultrasonic mesh nebulizer. RV pressure waveform monitoring was obtained by continuously transducing the RV port of the pulmonary artery (PA) catheter.

RESULTS

The final analysis included 26 patients receiving iE&iM. There was a significant drop in mean PA pressure (MPAP) (-4.8 ± 8.7, P = 0.010), systolic PA pressure (SPAP) (-8.2 ± 12.8, P = 0.003), RV end-diastolic pressure (RVEDP) (-2.1 ± 2.8, P < 0.001) and RV diastolic pressure gradient (RVDPG) (-1.7 ± 1.4, P < 0.001) after 17 ± 9 minutes of iE&iM administration. Patients also had a significant increase in RV outflow tract (RVOT) gradient (3.7 ± 4.7, P < 0.001), RV maximal rate of pressure rise during early systole (dP/dt max) (68.3 ± 144.7, P = 0.024), and left ventricular (LV) dP/dt max (66.4 ± 90.1, P < 0.001). Change in RVOT gradient was only observed in those with a positive pulmonary vasodilator response to treatment. Treatment with iE&iM did not present adverse effects when compared with a matched case-control group.

CONCLUSIONS

Coadministration of iE&iM in cardiac surgery patients presenting with PH or signs of RV dysfunction is a safe and effective treatment approach in improving RV function. Appearance of a transient increase in RVOT gradient after iE&iM could be useful to predict response to treatment.

Comparison of Nebulized Versus Intravenous Milrinone on Reducing Pulmonary Arterial Pressure in Patients with Pulmonary Hypertension Candidate for Open-cardiac Surgery: A Double-Blind Randomized Clinical Trial

Background

Regardless of the cause, pulmonary hypertension can increase patient complications and mortality. This study compared the effect of nebulized versus intravenous (IV) milrinone on reducing pulmonary arterial pressure in patients with pulmonary hypertension candidates for open-cardiac surgery.

Methods

This double-blind, randomized clinical trial was performed on 32 patients undergoing elective on-pump cardiac surgery during January 2021-January 2022 in the Cardiac Operating Room of Golestan Hospital, Ahvaz, Iran. Patients were randomly divided into test groups nebulize milrinone (N = 16) and IV milrinone (N = 16). The medication was administered after the cross-clamp of the aorta opening. The outcome variables included hemodynamic data, cardiac output, cardiac index, stroke volume, mean arterial pressure (MAP), central venous pressure, mean pulmonary artery pressure (mPAP), systemic vascular resistance, pulmonary vascular resistance, MAP/mPAP ratio, time until extubation, duration of hospitalization in the Intensive Care Unit (ICU), and duration of hospital stay.

Results

In the nebulized group, MAP and MAP/mPAP were significantly higher than in the IV milrinone group (P = 0.09 and P < 0.0001, respectively). The time of extubation (P = 0.001), duration of hospitalization in the ICU (P = 0.009), and duration of hospital stay (P = 0.026) in the nebulized milrinone group were significantly shorter than in the IV milrinone group.

Conclusions

Nebulized milrinone administration before weaning off cardiopulmonary bypass (CPB) can be accelerated and facilitate weaning off CPB. Moreover, despite maintaining MAP, nebulized milrinone significantly reduces mPAP. According to the results of this study, nebulized milrinone is recommended in patients undergoing cardiac surgery with pulmonary hypertension.

Inhaled Milrinone via HFNC as a Postextubation Cardiopulmonary Elixir: Case Series and Review of Literature

Pulmonary hypertension (PH) often complicates perioperative course following pediatric cardiac surgery, often presenting unique challenges to the attending cardiac anesthesiologist. Apart from difficult weaning from cardiopulmonary bypass, PH can often compound weaning from mechanical ventilation in this postoperative subset. From pathophysiological standpoint, the former can be attributed to concurrent detrimental cardiopulmonary consequences of PH as a multisystemic syndrome. Therefore, with an objective to address the affected systems, that is, cardiac and pulmonary simultaneously, we report combined use of inhaled milrinone (a pulmonary vasodilator) through high-frequency nasal cannula (oxygen reservoir and continuous positive airway pressure delivery device), purported to complement each other's mechanism of action in the management of PH, thereby hastening postoperative recovery. This article additionally presents a nuanced perspective on the advantages of combining the aforementioned therapies and hence proposing the same as a possible “postoperative cardiopulmonary elixir.”

Inhaled Milrinone via HFNC as a Postextubation Cardiopulmonary Elixir: Case Series and Review of Literature

Pulmonary hypertension (PH) often complicates perioperative course following pediatric cardiac surgery, often presenting unique challenges to the attending cardiac anesthesiologist. Apart from difficult weaning from cardiopulmonary bypass, PH can often compound weaning from mechanical ventilation in this postoperative subset. From pathophysiological standpoint, the former can be attributed to concurrent detrimental cardiopulmonary consequences of PH as a multisystemic syndrome. Therefore, with an objective to address the affected systems, that is, cardiac and pulmonary simultaneously, we report combined use of inhaled milrinone (a pulmonary vasodilator) through high-frequency nasal cannula (oxygen reservoir and continuous positive airway pressure delivery device), purported to complement each other's mechanism of action in the management of PH, thereby hastening postoperative recovery. The article additionally presents a nuanced perspective on the advantages of combining the aforementioned therapies and hence proposing the same as a possible “postoperative cardiopulmonary elixir.”

Inhaled pulmonary vasodilators: a narrative review

Pulmonary hypertension (PH) is a severe disease that affects people of all ages. It can occur as an idiopathic disorder at birth or as part of a variety of cardiovascular and pulmonary disorders. Inhaled pulmonary vasodilators (IPV) can reduce pulmonary vascular resistance (PVR) and improve RV function with minimal systemic effects. IPV includes inhaled nitric oxide (iNO), inhaled aerosolized prostacyclin, or analogs, including epoprostenol, iloprost, treprostinil, and other vasodilators. In addition to pulmonary vasodilating effects, IPV can also be used to improve oxygenation, reduce inflammation, and protect cell. Off-label use of IPV is common in daily clinical practice. However, evidence supporting the inhalational administration of these medications is limited, inconclusive, and controversial regarding their safety and efficacy. We conducted a search for relevant papers published up to May 2020 in four databases: PubMed, Google Scholar, EMBASE and Web of Science. This review demonstrates that the clinical using and updated evidence of IPV. iNO is widely used in neonates, pediatrics, and adults with different cardiopulmonary diseases. The limitations of iNO include high cost, flat dose-response, risk of significant rebound PH after withdrawal, and the requirement of complex technology for monitoring. The literature suggests that inhaled aerosolized epoprostenol, iloprost, treprostinil and others such as milrinone and levosimendan may be similar to iNO. More research of IPV is needed to determine acceptable inclusion criteria, long-term outcomes, and management strategies including time, dose, and duration.

Inhaled versus intravenous milrinone in mitral stenosis with pulmonary hypertension

OBJECTIVE

To evaluate and compare the hemodynamic effects of intraoperative intravenous milrinone versus inhalational milrinone at two timepoints in patients with severe pulmonary hypertension undergoing mitral valve surgery.

METHODS

A prospective observational study was performed in 100 patients with severe rheumatic mitral stenosis (with/without regurgitation) and right ventricular systolic pressure > 50 mm Hg. They were divided into two groups based on the strategy used to reduce pulmonary hypertension. Fifty patients had inhalational milrinone after sternotomy until initiation of cardiopulmonary bypass and after release of the aortic crossclamp until weaning off cardiopulmonary bypass. The other 50 patients received an intravenous loading dose of milrinone 50 µg·kg^-1 over 10 min on release of the aortic crossclamp. Both groups received intravenous milrinone 0.5 µg·kg^-1 during weaning from cardiopulmonary bypass. Hemodynamic data were evaluated at the 3 timepoints.

RESULTS

Pulmonary artery pressures, central venous pressure, and pulmonary capillary wedge pressure decreased significantly in the inhalational milrinone group compared to the intravenous milrinone group. Systemic vascular resistance index and cardiac index were significantly higher and pulmonary vascular resistance index was significantly lower in the inhalational milrinone group. The mean arterial pressure-to-mean pulmonary artery pressure ratio was significantly lower in the intravenous milrinone group. Tricuspid annular plane systolic excursion and right ventricular fractional area change were increased significantly in the inhalational milrinone group.

CONCLUSION

Intraoperative inhalational milrinone before and after cardiopulmonary bypass is safe, easy to administer, and results in significant improvements in right ventricular hemodynamics, right ventricular function, and systemic hemodynamics.

In Vitro Evaluation of a Vibrating-Mesh Nebulizer Repeatedly Use over 28 Days

This in vitro study evaluates the performance of a disposable vibrating-mesh nebulizer when used for 28 days. A lung model was used to simulate the breathing pattern of an adult with chronic obstructive pulmonary disease. The vibrating-mesh nebulizer was used for three treatments/day over 28 days without cleaning after each test. Results showed that the inhaled drug dose was similar during four weeks of use (p = 0.157), with 16.73 ± 4.46% at baseline and 15.29 ± 2.45%, 16.21 ± 2.21%, 17.56 ± 1.98%, and 17.13 ± 1.81%, after the first, second, third, and fourth weeks, respectively. The particle size distribution, residual drug volume, and nebulization time remained similar across four weeks of use (p = 0.110, p = 0.763, and p = 0.573, respectively). Mesh was inspected using optical microscopy and showed that approximately 50% of mesh pores were obscured after 84 runs, and light penetration through the aperture plate was significantly reduced after the 21st use (p < 0.001) with no correlation to nebulizer performance. We conclude that the vibrating-mesh nebulizer delivered doses of salbutamol solution effectively over four weeks without cleaning after each use even though the patency and clarity of the aperture plate were reduced by the first week of use.