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.

Technology III: in-line vaporizer with reflector.

As the clinical advantages of vapor anesthesia (VA) for sedation of patients in ICU become more apparent, the ergonomics, economy and safety issues need to be better addressed. Here we describe the use of a new commercial digital in-line anesthetic vaporizer that can be attached to the inspiratory limb of a ventilator. If used with a simple, and easily assembled secondary circuit and anesthetic reflector, the circuit remains remote from the patient, the VA consumption approaches a physical minimum, VA level is controlled and monitored, and the tidal volume size is not limited.

High volatile anaesthetic conservation with a digital in-line vaporizer and a reflector.

BACKGROUND: A volatile anaesthetic (VA) reflector can reduce VA consumption (VAC) at the cost of fine control of its delivery and CO2 accumulation. A digital in-line vaporizer and a second CO2 absorber circumvent both of these limitations. We hypothesized that the combination of a VA reflector with an in-line vaporizer would yield substantial VA conservation, independent of fresh gas flow (FGF) in a circle circuit, and provide fine control of inspired VA concentrations. METHOD: Prospective observational study on six Yorkshire pigs. A secondary anaesthetic circuit consisting of a Y-piece with 2 one-way valves, an in-line vaporizer and a CO2 absorber in the inspiratory limb was connected to the patient's side of the VA reflector. The other side was connected to the Y-piece of a circle anaesthetic circuit. In six pigs, an inspired concentration of sevoflurane of 2.5% was maintained by the in-line vaporizer. We measured VAC at FGF of 1, 4 and 10 l/min. RESULTS: With the secondary circuit, VAC was 55% less than with the circle system alone at FGF 1 l/min, and independent of FGF over the range of 1-10 l/min. Insertion of a CO2 absorber in the secondary circuit reduced Pet CO2 by 1.3-2.0 kpa (10-15 mmHg). CONCLUSION: A secondary circuit with reflector and in-line vaporizer provides highly efficient anaesthetic delivery, independent of FGF. A second CO2 absorber was necessary to scavenge the CO2 reflected by the anaesthetic reflector. This secondary circuit may turn any open circuit ventilator into an anaesthetic delivery unit.

Structural and congenital heart disease interventions: the role of three-dimensional printing.

Advances in catheter-based interventions in structural and congenital heart disease have mandated an increased demand for three-dimensional (3D) visualisation of complex cardiac anatomy. Despite progress in 3D imaging modalities, the pre- and periprocedural visualisation of spatial anatomy is relegated to two-dimensional flat screen representations. 3D printing is an evolving technology based on the concept of additive manufacturing, where computerised digital surface renders are converted into physical models. Printed models replicate complex structures in tangible forms that cardiovascular physicians and surgeons can use for education, preprocedural planning and device testing. In this review we discuss the different steps of the 3D printing process, which include image acquisition, segmentation, printing methods and materials. We also examine the expanded applications of 3D printing in the catheter-based treatment of adult patients with structural and congenital heart disease while highlighting the current limitations of this technology in terms of segmentation, model accuracy and dynamic capabilities. Furthermore, we provide information on the resources needed to establish a hospital-based 3D printing laboratory.

Simulation-based teaching versus point-of-care teaching for identification of basic transoesophageal echocardiography views: a prospective randomised study.

In recent years, the use of transoesophageal echocardiography has increased in anaesthesia and intensive care. We explored the impact of two different teaching methods on the ability of echocardiography-naïve subjects to identify cardiac anatomy associated with the 20 standard transoesophageal echocardiography imaging planes, and assessed trainees' satisfaction with these methods of training. Fifty-two subjects were randomly assigned to one of two groups: a simulation-based and a theatre-based teaching group. Subjects undertook video-based tests comprised of 20 multiple choice questions on echocardiography views before and after receiving echocardiography teaching. Subjects in simulation- and theatre-based teaching groups scored 40% (30-40 [20-50])% and 35% (30-40 [15-55])% in the pre-test, respectively (p = 0.52). Following echocardiography teaching, subjects within both groups improved upon their pre-test knowledge (p < 0.001). Subjects in the simulation-based teaching group significantly outperformed their theatre-based group counterparts in the post-intervention test (p = 0.0002).

Diastolic dysfunction, cardiopulmonary bypass, and atrial fibrillation after coronary artery bypass graft surgery.

BACKGROUND: Atrial fibrillation (AF) is a common complication after coronary artery bypass graft (CABG) surgery, and is associated with increased morbidity, mortality, and utilization of healthcare resources. Diastolic dysfunction (DD) causes a range of changes in left atrial structure and function that may predispose patients to increased risk of AF. We hypothesized that patients with either new or worsened grade of DD after cardiopulmonary bypass (CPB) would have higher prevalence of AF after CABG surgery. The current study sought to determine an association between the dynamic changes in diastolic function during the perioperative period and postoperative AF in patients undergoing CABG surgery. METHODS: A total of 109 patients undergoing elective CABG surgery were assessed for the presence of DD before and after CPB. All patients were monitored for the development of AF after surgery for the entire hospital stay. RESULTS: DD was present in 89 (81%) and 91 (83%) patients before and after CPB. Thirty-four (31%) patients had either new or worsened grade of DD after CPB. Postoperative AF was present in 30 (27.5%) patients, including 15 (44%) patients with either new or worsened DD, and 15 (20%) patients with either unchanged or improved DD (P=0.009). Independent predictors of postoperative AF included age ≥65 yr [odds ratio (OR) 4.207, 95% confidence interval (CI) 1.527, 11.588], and new or worsened DD (OR 4.145, 95% CI 1.519, 11.356). CONCLUSIONS: New or worsened DD after CABG surgery is associated with an increased incidence of postoperative AF. CLINICAL TRIAL REGISTRATION: http://www.clinicaltrials.gov; unique identifier NCT00188903.

The impact of internet and simulation-based training on transoesophageal echocardiography learning in anaesthetic trainees: a prospective randomised study.

With the increasing role of transoesophageal echocardiography in clinical fields other than cardiac surgery, we decided to assess the efficacy of multi-modular echocardiography learning in echo-naïve anaesthetic trainees. Twenty-eight trainees undertook a pre-test to ascertain basic echocardiography knowledge, following which the study subjects were randomly assigned to two groups: learning via traditional methods such as review of guidelines and other literature (non-internet group); and learning via an internet-based echocardiography resource (internet group). After this, subjects in both groups underwent simulation-based echocardiography training. More tests were then conducted after a review of the respective educational resources and simulation sessions. Mean (SD) scores of subjects in the non-internet group were 28 (10)%, 44 (10)% and 63 (5)% in the pre-test, post-intervention test and post-simulation test, respectively, whereas those in the internet group scored 29 (8)%, 59 (10)%, (p = 0.001) and 72 (8)%, p = 0.005, respectively. The use of internet- and simulation-based learning methods led to a significant improvement in knowledge of transoesophageal echocardiography by anaesthetic trainees. The impact of simulation-based training was greater in the group who did not use the internet-based resource. We conclude that internet- and simulation-based learning methods both improve transoesophageal echocardiography knowledge in echo-naïve anaesthetic trainees.