Haemodynamic Tolerance of Patients Following Cardiac Surgery Receiving Vasoactive Medication in Upright Positioning.

Abstract

Introduction: Patients undergoing cardiac surgery require post-operative management in the Intensive Care Unit (ICU). Mobilising patients in the ICU has been shown to have many beneficial effects such as increasing muscle strength and increasing health-related quality of life. As a part of routine management, patients following cardiac surgery are mobilised in ICU if they are considered haemodynamically stable. However, haemodynamic compromise is common after cardiac surgery, often manifesting as hypotension and reduced cardiac output. As a result these patients may require administration of vasoactive medication while they remain in ICU. Therefore, it can be difficult to know when it may be safe to mobilise patients following cardiac surgery who are receiving vasoactive medication. There is no consensus among ICU experts regarding when it is safe to commence exercise with patients who are receiving vasoactive medication. Concerns may exist about haemodynamic instability that could potentially be exacerbated with upright positioning or mobility. Objectives: The primary aim of this study was to measure the effect of exercise in upright positioning on haemodynamic parameters of patients following cardiac surgery receiving vasoactive therapy. The secondary aims were to clarify what level of vasoactive medication may allow safe exercise, and determine the incidence of adverse events. Haemodynamic parameters that were measured included heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP), systolic and diastolic blood pressure (BP), cardiac output (CO), cardiac index (CI), stroke volume (SV), and peripheral oxygen saturation (SpO2). Methods: This was a prospective, single-centre, cohort study conducted in an adult ICU of a tertiary, cardiothoracic university-affiliated hospital in Australia. Ethical clearance and site-specific approval from the Prince Charles Hospital was obtained prior to data collection (HREC 17/QPCH/31). Ethical clearance was also obtained from Griffith University (GU Ref No: 2917/186). Eligible participants were recruited from August 2017 to May 2018. The Flotrac-Vigileo™ system was used to obtain haemodynamic measurements. Subjects were positioned from supine, high sitting, sitting on the edge of the bed, standing, marching on the spot and then returned to supine where they remained for 5 minutes. Subjects remained in these positions for one minute. A between-within repeated measures ANOVA was conducted to compare haemodynamic variables over various positions and interactions with positions*dose of low versus medium to high levels of vasoactive medication. Results: Twenty participants were recruited; 16 (80%) male; mean age of 65.9 (10.6) years, with 6 (30%) receiving low dose vasoactive medication and 14 (70%) receiving a moderate to high dose. Upright positioning caused statistically significant increases in MAP (p=0.018), diastolic BP (p=0.008), and RR (p=0.049). At an individual level, clinically significant changes in CO, CI, SV, systolic BP, HR and SpO2 were observed. There was no significant interaction between position and dose of vasoactive medication. One minor adverse event occurred in a participant on low dose Dopamine. This was a transient decrease in MAP, and led to no clinically significant consequences. Conclusions: Upright positioning led to no clinically significant consequences in this study population. The findings suggest that vasoactive medication alone should not be considered a contraindication to upright positioning in patients following cardiac surgery, and should be explored with a larger sample size.