Pre‐operative transthoracic echocardiography in ambulatory surgery—A cross‐sectional study

Cardiac disease and aberrations in central volume status are risk factors for perioperative complications, and should be identified prior to surgery. This study investigated the benefit of transthoracic echocardiography (TTE) for pre‐operative identification of cardiac disease and hypovolemia in ambulatory surgery.

patients at risk. 9,10 Clinical evaluation of a patient's hemodynamic state may be unreliable due to inadequate/incomplete history, lack of medical records, time constraints as well as complicating comorbidities. Consequently, anesthesiologists are frequently required to proceed to surgery without up-to-date hemodynamic information.
Pre-operative transthoracic echocardiography (TTE) enables an individualized anesthesia management by establishing current central volume status (eu/hypo/hypervolemia) as well as cardiac disease prior to surgery 11,12 ). Pre-operative TTE has been demonstrated to contribute valuable hemodynamic information for perioperative management in emergency surgery, 13 major non-cardiac surgery, 14,15 bariatric, 16,17 and thoracic surgery 18 with suspected cardiac disease.
To our knowledge, the value of pre-operative TTE has not been previously evaluated in an ambulatory setting, hence the prevalence of previously unknown cardiac disease and aberrations in central volume status immediately prior to surgery is unclear. Thus, the aim of this study was to quantify the number of patients with cardiac disease and/or pre-operative low level of venous return at the day of surgery.

| Ethics
Ethical approval (Dnr 2016/316-31) was provided by the Regional Ethical Board in Umeå (Sweden) and written informed, signed consent was obtained from all individuals participating in the study. The study was reg-

| Study population
One hundred and thirty individuals, ≥18 years of age, with a body mass index <35 kg/m 2 , scheduled for ambulatory surgery (breast cancer, thyroidal, or gastrointestinal surgery) were consecutively assessed for eligibility for the study. The first patient every study day was excluded due to surgery flow (n = 30). After enrollment and signed consent (n = 100), four individuals were excluded due to a poor TTE-acquisition quality. Thus, the statistical analysis was conducted on 96 individuals. The study logistics are summarized in

| Study protocol
Transthoracic echocardiography was performed on all patients at the pre-operative day-care unit, within 2 hours before anesthesia induction. Standard over-night 6 hours minimum fasting and clear fluids were allowed until 2 hours before surgery. Patient history, current medications, and standard pre-operative laboratory tests were collected from the medical records. Patient history, with focus on exercise tolerance, history of dyspnea, and/or orthopnea, was gathered. Non-invasive blood pressure was measured in supine position with a proper-sized cuff. A venous cannula was placed in a forearm and standard blood samples, in addition to those for biomarkers of myocardial damage (high-sensitive troponin I) and

Editorial Comment
In this prospective cohort study, patients undergoing ambulatory surgery received a thorough transthoracic echocardiography pre-operatively. The study found that a quarter of all patients screened had an echocardiographic finding that might negatively influence hemodynamics. While it is unlikely that all of these findings increased the risk of harm in ambulatory surgery with minimum volume shifts, the findings still should encourage anesthesiologists to consider doing a focused pre-operative echocardiographic examination in patients at risk for adverse outcomes.

F I G U R E 1
The study flow diagram and pre-operative measures. Abbreviations: *, The first patient every study day was excluded due to the surgery flow; TTE, transthoracic echocardiography; tropHS, high-sensitive troponin; Nt-proBNP, N-terminal prohormone of brain natriuretic peptide; NYHA, New York Heart Association functional classification dysfunction (N-terminal prohormone of brain natriuretic peptide, Nt-proBNP), were collected. Revised cardiac risk index (RCRI) and classification according to the New York Heart Association (NYHA) Functional Classification were defined for each patient.

| Echocardiographic protocol
All measurements were performed by a sonographer (LL) and a clinical cardiac physiologist/anesthesiologist (TM) accordingly to current guidelines. 19,20 Heart function was classified using current recom-  (Table 2).

| Statistics
The sample size of the study was calculated to a minimum of 93 sub- Levene's test was applied for equality of variances and the Student's t test was used for comparisons of mean values. P < .05 were considered statistically significant.

| Inter-and intra-observation variability
Reproducibility of echocardiographic data was assessed by reanalysis of 13 randomly selected cases. These cases were chosen for TA B L E 1 Overall patient characteristics, comorbidities with preoperative diagnosis, and regular medications (n = 96) Nt-proBNP (ng L −1 ) 300 ± 510

| RE SULTS
Ninety-six individuals, with a mean age of 63.5 ± 12.3 years (range 26-85) and body mass index 27.0 ± 4.3 kg/m 2 , were scheduled for ambulatory breast cancer surgery (61), reconstructive (plastic) surgery (4), thyroidal surgery (16), or minor abdominal surgery (15). In breast cancer surgery, two patients received pre-operative chemotherapy. No pre-operative radiotherapy was applied. One third of the study population was over 70 years old, and 84/96 were women. Patient characteristics and comorbidities are summarized in Table 1 and differences between male and female patients are reported in Table 4.

| Previously known cardiac dysfunction
Based on medical records of the last 5 years before surgery, 14 patients had a diagnosis of heart failure (HF). Ten of these were defined as HFrEF and one as a RV failure, while for the remaining three cases the type of HF was not mentioned.    (7) Combination of hypovolemia and decreased compliance of LV a 23/96 (24) Abbreviations: eRAP, estimation of right ventricular pressure based on inferior vena cava measurements; HFmrEF, heart failure with moderately reduced ejection fraction; HFpEF, heart failure with preserved ejection fraction; HFrEF, heart failure with reduced ejection fraction; LV, left ventricle; RV, right ventricle. a Decreased compliance of LV by definition: restrictive and/or pseudo-normalization.  Tables 2, 3, and 4.

| Central volume status
Overall, in this non-selected ambulatory surgery cohort, we found previously unknown pathologies with a potential impact on perioperative hemodynamic stability in 23/96 (24%) individuals.
These findings were severe hypovolemia (n = 16) in addition to the obstructive structural valve and myocardial pathologies mentioned above (n = 7). Based on these cases, the number needed to treat (NNT), that is efficacy of pre-operative TTE, to identify one potential major hemodynamic concern was 4.2. In addition, the NNTs for low level of venous return, significant LV compliance problems (restrictive diastolic function or pseudo-normalization), and HF were, respectively, 2.2, 12.5, 1.8, and 2.5.

| D ISCUSS I ON
In this unselected cohort with ambulatory surgical patients, we identified a substantial number of previously unknown cases of cardiac disease, especially in patients over 65 years of age. Low MET was found to correlate with LV dysfunction. In addition, individuals with low MET were elderly. Further, a high prevalence of asymptomatic LV dysfunction, also at an increased perioperative risk 7,8 , was observed at 40-65 years of age. Valuable information on central volume status was obtained for all patients, and almost one half was hypovolemic. Transthoracic echocardiographic screening of IVCmax and collapsibility index (respiratory dynamics of IVC) seems to be useful perioperatively. In the recent study by Zhang et al, 23 both IVCmax and collapsibility index were found be good predictors for perioperative hypotension after anesthesia induction indicating that pre-operative volume depletion may exist. Systolic as well as diastolic LV dysfunction are well-recognized risk factors for perioperative adverse outcome, and should be identified prior to surgery. 4,5,7,24 Aortic stenosis, a common disease in the elderly population, is also a major risk factor and may be missed by clinical examination. 25 RV myocardial performance index a 0.6 ± 0.2 0.5 ± 0.1 0.6 ± 0.2 P = .009 Abbreviations: E/e', transmitral E-velocity e´-velocity ratio; HFpEF, heart failure with preserved ejection fraction; LV, left ventricle; Nt-proBNP, N-terminal prohormone of brain natriuretic peptide; RV, right ventricle. a Tissue Doppler-derived right ventricular myocardial performance index. b Fischer exact test was applied due to low number of patients in the group "age <65". (n < 5).

TA B L E 3
Characteristics, hemodynamic, and echocardiographic findings (number of cases or mean values ± SD), overall and in individuals under and over 65 years of age enables an individualized anesthesia management, and may play a key role in minimizing perioperative complications. 29 Nonetheless, at present, the use of TTE in pre-operative clinical praxis is not a routine approach, and clear indications are lacking. The 2014 ESC/ ESA guidelines on cardiovascular assessment in non-cardiac surgery do not recommend routine pre-operative TTE on asymptomatic patients. 6 Further, a large retrospective cohort study found that pre-operative TTE within 6 months of surgery was not associated with a reduction in mortality or length of hospital stay. 30 However, a TTE performed months before surgery, although this allows for cardiac optimization, does not provide up-to-date information regarding volume status at the day of surgery. Anesthesiologist-performed TTE seems to predict cardiac events and provide information affecting clinical decision making, 14 but the benefit regarding patient outcome is still unclear. Nevertheless, in recent meta-analysis exploring the use of perioperative ultrasound, TTE is expected to increase perioperative safety and cut complication rates. 31 Due to future challenges of the cardiovascular epidemic and an aging population, a paradigm shift regarding pre-operative risk assessment should be considered. 3,6 Even short episodes of intraoperative hypotension are associated with worsened surgical outcome, 28

| Limitations
This study has several limitations. First, the generalizability of the study results is limited due to the large proportion of women.
However, the cohort is unselected, and the results implicate that in populations similar to this, pre-operative cardiovascular assessment with TTE is reasonable. In this observational study, the selection bias was minimized. The study protocol was impossible to apply on the first patient of every study day (overall 30 individuals) due to the ambulatory surgery time schedule. Thereafter, a strict consecutive enrollment was conducted and, thus, the sample can be considered truly random (Figure 1). A standard fasting time (6 hours minimum) and clear fluids were allowed until 2 hours before surgery.
However, actual fasting time and/or intake of clear fluids were not registered. This may have had an impact on the results. The echocardiographic protocol was comprehensive and may not be realistic to implement in clinical praxis. A screening protocol (extended point-of-care assessment) focusing on essential hemodynamic data may be preferable.

| Educational suggestions
Ultrasound has become one of the most powerful and feasible imaging techniques in medicine. Theoretical knowledge and practical skills in at least point-of-care ultrasound should be achieved early in the career of a medical provider. 34 Even more comprehensive approaches have been described recently. 35 Certificated training programs should be integrated as a default part of relevant residency programs, and perhaps already in undergraduate medical education.
Implementation of the use of ultrasound early in the medical career could increase the understanding of anatomical concepts and hemodynamics in anesthesia and intensive care, and thus contribute to patient safety. 6,36-38

| CON CLUS ION
In this ambulatory surgical cohort, a high prevalence of pre-operative LV dysfunction and aberrations in volume status was observed. The results demonstrate that pre-operative TTE contributed valuable hemodynamic information. The standard pre-operative assessment for this cohort might need to be revised.

AUTH O R CO NTR I B UTI O N S
Tomi Myrberg: This author contributed to the study design, data collection and analysis, and preparation of the article. Ylva Stenberg: This author contributed to analysis of data, study design, and preparation of the article. Linnea Lindelöf: This author helped to data collection and preparation of the article. Magnus Hultin: This author contributed to study design, interpretation of data, and preparation of the article.

DATA AVA I L A B I L I T Y S TAT E M E N T
The SPSS data files regarding this manuscript are available from the corresponding author on reasonable request.