Acute effect of sildenafil on central hemodynamics in mechanically ventilated patients with WHO group III pulmonary hypertension and right ventricular failure necessitating administration of dobutamine

[Acute right heart failure on the intensive care unit : Pathophysiology, monitoring and management]

Right ventricular heart failure is a frequent and serious but often undetected and complex clinical challenge on the intensive care unit. The commonest causes include acute decompensation of pulmonary hypertension, pulmonary embolism, sepsis, acute respiratory distress, and cardiothoracic surgery. The gold standard of bedside diagnosis is a combination of clinical symptoms, biochemical markers (NT-proBNP) and echocardiography. For the purposes of hemodynamic monitoring and treatment management, the indication to place a pulmonary artery catheter should be made generously. The major components of management include treating the underlying disease and triggering factors, reducing pulmonary vascular resistance, increasing contractility, volume optimization, and maintenance of adequate perfusion. Mechanical circulatory support should be considered before irreversible end-organ failure develops.

Dose–Response Head-to-Head Comparison of Inodilators Dobutamine, Milrinone, and Levosimendan in Chronic Experimental Pulmonary Hypertension

The choice of inodilator drug in the acute management of patients with pulmonary hypertension (PH) having right ventricular (RV) failure remains unsettled and challenging. Comprehensive experimental evaluations may provide further insight and fundamental translational research clues to support inodilator selection and clinical trial design. Our aim was to compare acute dose–response hemodynamic effects of inodilators dobutamine (DOB), milrinone (MIL), and levosimendan (LEV) in chronic experimental PH. Seven-week-old male Wistar rats were randomly injected with 60 mg·kg−1 monocrotaline (MCT) or vehicle (Ctrl, n = 7) and underwent systemic and pulmonary artery (PA) pressure and RV pressure–volume (PV) hemodynamic evaluation under halogenate anesthesia 24 to 30 days after injection. The MCT-injected animals (n = 7 each) randomly received dose–response infusions of DOB (1, 3, 6 and 12 μg·kg−1·min−1), MIL (MIL: 1, 3, 6 and 12 μg·kg−1·min−1), or LEV (0.3, 0.6, 1.2 and 2.4 μg·kg−1·min−1). Load-independent indexes were obtained by inferior vena cava occlusion at baseline and after the last dose. All inodilators increased RV ejection fraction, preload recruitable stroke work, and ventricular–vascular coupling without jeopardizing perfusion pressure. Dobutamine raised heart rate and PA pressure. Only LEV increased cardiac index and decreased PA elastance and pulmonary vascular resistance (PVR). Moreover, only LEV downward-shifted the end-diastolic PV relationship, thereby improving RV compliance. Adding sildenafil to LEV further decreased PVR. Levosimendan had beneficial acute systolic and diastolic functional effects in experimental chronic PH and RV afterload compared to DOB and MIL. It should be further tested in clinical trials enrolling patients with PH in the perioperative and critical care settings.

Management of right ventricular dysfunction in the perioperative setting

PURPOSE OF REVIEW

This review summarizes the approach to and recent developments in the treatment of acute right ventricular dysfunction and failure in the perioperative setting. Right ventricular failure, defined as the inability to deliver sufficient blood flow through the pulmonary circulation at normal central venous pressure, is a common problem in the perioperative setting and is associated with an increased mortality. The failure of the right ventricle is caused by reduced right ventricular contractility or an increased right ventricular afterload or both.

RECENT FINDINGS

Management of acute right ventricular failure continues to be challenging because of the poor understanding of the pathophysiology, difficulties in diagnosing, the absence of guidelines, and limited therapeutic options. Recent research efforts have led to an improved understanding of the underlying mechanisms and have established a reasonable therapeutic framework.

SUMMARY

Right ventricular dysfunction may cause venous congestion and systemic hypoperfusion. After identifying right ventricular dysfunction, the primary goal is to correct reversible causes of excessive load or reduced right-ventricular contractility. If the underlying abnormalities cannot be reversed, diuretic, vasodilator, or inotropic therapy may be required.

A new framework for interpreting the outcomes of imperfectly blinded controlled clinical trials

It is well known that the outcome of an intervention is affected both by the inherent effects of the intervention and the patient's expectations. For this reason in comparative clinical trials an effort is made to conceal the nature of the administered intervention from the participants in the trial i.e. to blind the trial. Yet, in practice perfect blinding is impossible to ensure or even verify post hoc. The current clinical standard is to follow up the trial with an auxiliary questionnaire, which allows trial participants to express in closed form their belief concerning the intervention, i.e. trial group assignment (treatment or control). Auxiliary questionnaire responses are then used to compute the extent of blinding in the trial in the form of a blinding index. If the estimated extent of blinding exceeds a particular threshold the trial is deemed sufficiently blinded; otherwise, the strength of evidence of the trial is brought into question. This may necessitate that the trial is repeated. In this paper we make several contributions. Firstly, we identify a series of problems of the aforesaid clinical practice and discuss them in context of the most commonly used blinding indexes. Secondly, we formulate a novel approach for handling imperfectly blinded trials. We adopt a feedback questionnaire of the same form as that which is currently in use, but interpret the collected data using a novel statistical method, significantly different from that proposed in the previous work. Unlike the previously proposed approaches, our method is void of any ad hoc free parameters and robust to small changes in the participants' feedback responses. Our method also does not discard any data and is not predicated on any strong assumptions used to interpret participants' feedback. The key idea behind the present method is that it is meaningful to compare only the corresponding treatment and control participant sub-groups, that is, sub-groups matched by their auxiliary responses. A series of experiments on simulated trials is used to demonstrate the effectiveness of the proposed approach and its superiority over those currently in use.