A randomised controlled feasibility trial of a clinical protocol to manage hypotension during major non-cardiac surgery.

Intra-operative hypotension is a risk factor for postoperative morbidity and mortality. Minimally invasive monitors that derive other haemodynamic parameters, such as stroke volume, may better inform the management of hypotension. As a prelude to a multicentre randomised controlled trial, we conducted a single-centre feasibility trial of a protocol to treat hypotension as informed by minimally invasive haemodynamic monitoring during non-cardiac surgery. We recruited adults aged ≥40 years with cardiovascular risk factors who underwent non-cardiac surgery requiring invasive arterial pressure monitoring. Participants were randomly allocated to usual care, or a clinical protocol informed by an arterial waveform contour analysis monitor. Participants, outcome assessors, clinicians outside operating theatres and analysts were blinded to treatment allocation. Feasibility was evaluated based on: consent rate; recruitment rate; structured feedback from anaesthesia providers; and between-group differences in blood pressure, processes-of-care and outcomes. The consent rate among eligible patients was 33%, with 30 participants randomly allocated to the protocol and 30 to usual care. Anaesthesia providers rated the protocol to be feasible and acceptable. The protocol was associated with reduced fluid balance and hypotension exposure in the peri-operative setting. Postoperative complications included: acute myocardial injury in 18 (30%); acute kidney injury in 17 (28%); and surgical site infection in 7 (12%). The severity of complications was rated as moderate or severe in 25 (42%) participants. In summary, this single-centre study confirmed the feasibility of a multicentre trial to assess the efficacy and safety of a physiologically guided treatment protocol for intra-operative hypotension based on minimally invasive haemodynamic monitors.

Association Between Three-Dimensional Left Ventricular Outflow Tract Area and Gradients After Myectomy in Hypertrophic Obstructive Cardiomyopathy.

OBJECTIVE: Determine whether the intraoperative three-dimensional left ventricular outflow tract cross-sectional area may be inversely correlated with pressure gradients as a determinant of surgical success after septal myectomy in hypertrophic cardiomyopathy patients. DESIGN: Perioperative data were obtained by retrospective review. SETTING: Toronto General Hospital, University of Toronto, Toronto, Canada, a tertiary hospital. PARTICIPANTS: The study comprised 67 patients with hypertrophic obstructive cardiomyopathy. INTERVENTIONS: Transthoracic and intraoperative transesophageal echocardiographic assessment of pressure gradients. Transesophageal measurement of the three-dimensional left ventricular outflow tract cross-sectional area. MEASUREMENTS AND MAIN RESULTS: The smallest left ventricular outflow tract area increased on average 1.883 cm2 (98.3%) after septal myectomy. There was a significant correlation between the increase in the area and the transesophageal pressure gradients (r = -0.32; p = 0.01) after myectomy, but none with postoperative transthoracic gradients at rest (r = -0.10; p = 0.42). Postoperative transesophageal and transthoracic gradients were significantly correlated (r = 0.26; p = 0.04). The best risk factors to predict high residual gradients were preoperative transesophageal gradient >97 mmHg, postoperative transesophageal area <3.16 cm2, and moderate or more residual transesophageal mitral regurgitation (specificity 89%, 81%, and 78%, respectively). CONCLUSIONS: Three-dimensional left ventricular outflow tract area measurements with transesophageal echocardiography after myectomy correlated fairly well with postoperative transesophageal pressure gradients. Patients with residual transthoracic elevated gradients after surgery at follow-up had a smaller transesophageal area and higher transesophageal pressure gradients immediately after the procedure. However, transesophageal pressure gradients after myectomy correlated poorly with follow-up transthoracic gradients at rest.