Preoperative cardiac risk management.

Approximately 100 million people undergo noncardiac surgery annually worldwide. It is estimated that around 3% of patients undergoing noncardiac surgery experience a major adverse cardiac event. Although cardiac events, like myocardial infarction, are major cause of perioperative morbidity or mortality, its true incidence is difficult to assess. The risk of perioperative cardiac complications depends mainly on two conditions: (1) identified risk factors, and (2) the type of the surgical procedure. On that basis, different scoring systems have been developed in order to accurately assess the perioperative cardiac risk and to improve the patient management. Importantly, patients with estimated high risk should be tested preoperatively by non-invasive cardiac imaging modalities. According to test results, they can proceed directly to planed surgery with the use of cardioprotective drugs (beta-blockers, statins, aspirin), or to myocardial revascularization prior to non-cardiac surgery. In this review, we discuss the role of clinical cardiac risk factors, laboratory measurements, additional non-invasive cardiac testing, and consequent strategies in perioperative management of patients undergoing noncardiac surgery.

Epidural analgesia is associated with improved health outcomes of surgical patients with chronic obstructive pulmonary disease.

BACKGROUND: Patients with chronic obstructive pulmonary disease (COPD) have increased postoperative morbidity and mortality. Epidural analgesia (EDA) improves postoperative outcome but may worsen postoperative lung function. It is unknown whether patients with COPD benefit from EDA. The objective of this study was to determine whether patients with COPD undergoing major abdominal surgery benefit from EDA in addition to general anesthesia. METHODS: This cohort study included 541 consecutive patients with COPD who underwent major abdominal surgery between 1995 and 2007 at a university medical center. Propensity scores estimating the probability of receiving EDA were used in multivariate correction. The primary outcome was postoperative pneumonia and 30-day mortality. RESULTS: There were 324 patients (60%) who received EDA in addition to general anesthesia. The incidence of postoperative pneumonia (16% vs. 11%; P = 0.08) and 30-day mortality (9% vs. 5%; P = 0.03) was lower in patients who received EDA. After correction EDA was associated with improved outcome for postoperative pneumonia (OR 0.5; 95% CI: 0.3-0.9; P = 0.03). The strongest preventive effect was seen in patients with the most severe type of COPD. CONCLUSION: This study provides evidence that in patients with COPD who are scheduled for major abdominal surgery, epidural analgesia decreases postoperative pulmonary complications.

Perioperative cardiac evaluation, monitoring, and risk reduction strategies in noncardiac surgery patients.

PURPOSE OF REVIEW: Cardiac complications after noncardiac surgery cause significant morbidity and mortality. This review will discuss recent developments in risk stratification, monitoring, and risk reduction strategies. RECENT FINDINGS: The addition of biomarkers for ischemia, left ventricular function, and atherosclerosis to classic cardiac risk factors improves the prediction of both short-term and long-term outcome after noncardiac surgery. Intraoperative monitoring, using continuous 12-lead ECG assessment and transesophageal echocardiography, may timely identify treatable myocardial ischemia and arrhythmias. A prudent perioperative beta-blocker and statin regimen can reduce cardiac complications and mortality without increasing the risk of stroke in intermediate to high-risk patients. The use of circulatory assist devices might improve outcomes after major surgery in patients with severely reduced left ventricular function. SUMMARY: Systematic preoperative assessment can identify patients at high risk of cardiac complications and guide the application of appropriate risk reduction strategies.

Influence of noninvasive cardiovascular imaging in primary prevention: systematic review and meta-analysis of randomized trials.

BACKGROUND: Despite extensive use in practice, the impact of noninvasive cardiovascular imaging in primary prevention remains unclear. METHODS: We searched for randomized trials that compared imaging with usual care and reported any of the following outcomes in a primary prevention setting: medication prescribing, lifestyle modification (including diet, exercise, or smoking cessation), angiography, or revascularization. RESULTS: Seven trials were included. Trials screened patients for inducible myocardial ischemia (2 trials), coronary calcification (3 trials), carotid atherosclerosis (1 trial), or left ventricular hypertrophy (1 trial). Imaging had no effect on medication prescribing overall (odds ratio [OR], 1.01; 95% confidence interval [CI], 0.76-1.33) or on provision of lipid-modifying agents (OR, 1.08; 95% CI, 0.58-2.01), antihypertensive drugs (OR, 1.05; 95% CI, 0.75-1.47), or antiplatelet agents (OR, 1.05; 95% CI, 0.84-1.32). Similarly, no effect was seen on dietary improvement (OR, 0.78; 95% CI, 0.22-2.85), physical activity (0.02 vs -0.08 point change for imaging vs control on a 5-point scale; P = .23), or smoking cessation (OR, 2.24; 95% CI, 0.97-5.19). Imaging was not associated with invasive angiography (OR, 1.26; 95% CI, 0.89-1.79). CONCLUSIONS: We found limited evidence suggesting that noninvasive cardiovascular imaging alters primary prevention efforts. However, given the imprecision of these results, further high-quality studies are needed.

Exercise blood pressure response and perioperative complications after major vascular surgery.

OBJECTIVE: Earlier studies have shown that hypertensive or hypotensive blood pressure (BP) response during a preoperative treadmill exercise test in patients with peripheral arterial disease is associated with a two-fold increased risk of cardiovascular events and mortality. However, it is unknown if these patients also experience an increased perioperative complication risk at major vascular surgery. METHODS: In total 665 consecutive patients with peripheral arterial disease underwent elective major vascular surgery (carotid endarterectomy, abdominal aorta repair, or lower extremity revascularization). Perioperative complications (infection, myocardial infarction, angina pectoris, cardiac arrhythmia, heart failure, cerebrovascular accident or spinal cord ischemia, dialyses, amputation, thrombectomy, reoperation or death) were defined as occurring within 30 days after surgery and were collected using medical records. Hypertensive BP response was defined as a difference between exercise systolic BP and resting systolic BP of more than 55 mmHg. Hypotensive BP response was defined as a drop in exercise systolic BP below resting systolic BP. RESULTS: Patients with a hypertensive BP response during a preoperative exercise test (n = 66) showed a higher risk of early perioperative thrombectomy [hazard ratio (HR) 2.80 95% CI (1.24-6.33)] compared with patients with a normal BP response (n = 582). Patients with a hypotensive BP response (n = 18) showed an increased risk of perioperative myocardial infarction [HR 3.69 95% CI (1.08-12.64)] and cardiac complications [HR 2.90 95% CI (1.02-8.19)] compared with patients with a normal BP response. CONCLUSION: Patients with an abnormal BP response have more cardiovascular complications at elective major vascular surgery.

Effects of adherence to guidelines for the control of major cardiovascular risk factors on outcomes in the REduction of Atherothrombosis for Continued Health (REACH) Registry Europe.

OBJECTIVES: To examine the impact of cardiovascular risk factor control on 3-year cardiovascular event rates in patients with stable symptomatic atherothrombotic disease in Europe. METHODS: The REduction of Atherothrombosis for Continued Health (REACH) Registry recruited patients aged ≥45 years with established atherothrombotic disease or three or more risk factors, of whom 20 588 symptomatic patients from 18 European countries were analysed in this study at baseline and 12, 24 and 36 months. 'Good control' of cardiovascular risk factors was defined as three to five risk factors at target values of international guideline recommendations (systolic blood pressure <140 mm Hg, diastolic blood pressure <90 mm Hg, fasting glycaemia <110 mg/dl, total cholesterol <200 mg/dl, non-smoking). Independent predictors of 'good control' of major risk factors were assessed by multivariate analysis. RESULTS: Among symptomatic patients in the REACH Registry Europe (mean age 67 years, 70.6% male), 59.4% had good control of risk factors at baseline. Good risk factor control was associated with lower cardiovascular death/non-fatal stroke/non-fatal myocardial infarction (OR 0.76; 95% CI 0.69 to 0.83) and mortality (OR 0.89; 95% CI 0.79 to 0.99) at 36 months, compared with poor control. Independent predictors of good control of risk factors included residence in western versus eastern Europe (OR 1.29), high level of education (OR 1.16), established coronary artery disease (OR 1.18), treatment with one or more antithrombotic (OR 1.59) and one or more lipid-lowering agent (OR 1.16). CONCLUSIONS: In REACH, less than 60% of patients with stable atherothrombotic disease had good control of the five major cardiovascular risk factors. Improved risk factor control is associated with a positive impact on 3-year cardiovascular event rates and mortality.

Preoperative left ventricular dysfunction predisposes to postoperative acute kidney injury and long-term mortality.

BACKGROUND: Both preoperative left ventricular dysfunction (LVD) and acute kidney injury (AKI) in the postoperative period are independently associated with mortality. We evaluated the prevalence and prognostic implications of AKI in a cohort of vascular surgery patients. METHODS: Before vascular surgery, 1,158 patients were screened for LVD. Development of AKI, defined by RIFLE classification, was detected by serial serum creatinine measurements at days 1 to 3 after surgery. Primary end point was cardiovascular mortality during a median follow-up of 2.2 years (interquartile range [IQR] 1.0-4.0). RESULTS: LVD was present in 558 patients (48%), and 120 patients (10%) developed postoperative AKI. Subjects with LVD developed postoperative AKI more often than patients without LVD (8% vs. 13%, p=0.01). Patients were categorized as (i) no LVD, without AKI (n=551, 48%), (ii) LVD without AKI (n=487, 42%), (iii) no LVD, with AKI (n=49, 4%) and (iv) LVD with AKI (n=71/6%). Patients with LVD prior to surgery who developed postoperative AKI had the highest cardiovascular mortality risk (hazard ratio = 4.9; 95% confidence interval, 2.9-8.2). CONCLUSION: Patients with preoperatively LVD have an increased risk of developing AKI after vascular surgery. The occurrence of AKI in patients with LVD has an incremental predictive value toward cardiovascular mortality risk during long-term follow-up.

Prognostic value of troponin and creatine kinase muscle and brain isoenzyme measurement after noncardiac surgery: a systematic review and meta-analysis.

BACKGROUND: There is uncertainty regarding the prognostic value of troponin and creatine kinase muscle and brain isoenzyme measurements after noncardiac surgery. METHODS: The current study undertook a systematic review and meta-analysis. The study used six search strategies and included noncardiac surgery studies that provided data from a multivariable analysis assessing whether a postoperative troponin or creatine kinase muscle and brain isoenzyme measurement was an independent predictor of mortality or a major cardiovascular event. Independent investigators determined study eligibility and abstracted data in duplicate. RESULTS: Fourteen studies, enrolling 3,318 patients and 459 deaths, demonstrated that an increased troponin measurement after surgery was an independent predictor of mortality (odds ratio [OR] 3.4, 95% confidence interval [CI] 2.2-5.2), but there was substantial heterogeneity (I(2) = 56%). The independent prognostic capabilities of an increased troponin value after surgery in the 10 studies that assessed intermediate-term (≤ 12 months) mortality was an OR = 6.7 (95% CI 4.1-10.9, I(2) = 0%) and in the 4 studies that assessed long-term (more than 12 months) mortality was an OR = 1.8 (95% CI 1.4-2.3, I(2) = 0%; P < 0.001 for test of interaction). Four studies, including 1,165 patients and 202 deaths, demonstrated an independent association between an increased creatine kinase muscle and brain isoenzyme measurement after surgery and mortality (OR 2.5, 95% CI 1.5-4.0, I(2) = 4%). CONCLUSIONS: An increased troponin measurement after surgery is an independent predictor of mortality, particularly within the first year; limited data suggest an increased creatine kinase muscle and brain isoenzyme measurement also predicts subsequent mortality. Monitoring troponin measurements after noncardiac surgery may allow physicians to better risk stratify and manage their patients.

The influence of polyvascular disease on the obesity paradox in vascular surgery patients.

BACKGROUND: Obesity is a risk factor for atherosclerosis, a polyvascular process associated with reduced survival. In nonvascular surgery populations, a paradox between body mass index (BMI) and survival is described. This paradox includes reduced survival in underweight patients, whereas overweight and obese patients have a survival benefit. No clear explanation for this paradox has been given. Therefore, we evaluated the presence of the obesity paradox in vascular surgery patients and the influence of polyvascular disease on the obesity paradox. METHODS: In this retrospective study, 2933 consecutive patients were classified according to their preoperative BMI (kg/m(2)) and screened for polyvascular disease and cardiovascular risk factors before surgery. In addition, medication use at the time of discharge was noted. Outcome was all-cause mortality during a median follow-up of 6.0 years (interquartile range, 2-9 years). RESULTS: BMI (kg/m(2)) groups included 68 (2.3%) underweight (BMI <18.5), 1379 (47.0%) normal (BMI 18.5-24.9, reference), 1175 (40.0%) overweight (BMI 25-29.9), and 311 (10.7%) obese (BMI ≥ 30) patients. No direct interaction between BMI, polyvascular disease, and long-term outcome was observed. Underweight was an independent predictor of mortality (hazard ratio, 1.65; 95% confidence interval, 1.22-2.22). In contrast, overweight protected for all-cause mortality (hazard ratio, 0.79; 95% confidence interval, 0.700-0.89). Cardioprotective medication usage in underweight patients was the lowest (P < .001), although treatment targets for risk factors were equally achieved within all treated groups. CONCLUSION: Overweight patients referred for vascular surgery were characterized by an increased incidence of polyvascular disease and required more extensive medical treatment for cardiovascular risk factors at discharge. Long-term follow-up showed a paradox of reduced mortality in overweight patients.

Usefulness of repeated N-terminal pro-B-type natriuretic peptide measurements as incremental predictor for long-term cardiovascular outcome after vascular surgery.

Plasma N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) levels improve preoperative cardiac risk stratification in vascular surgery patients. However, single preoperative measurements of NT-pro-BNP cannot take into account the hemodynamic stress caused by anesthesia and surgery. Therefore, the aim of the present study was to assess the incremental predictive value of changes in NT-pro-BNP during the perioperative period for long-term cardiac mortality. Detailed cardiac histories, rest left ventricular echocardiography, and NT-pro-BNP levels were obtained in 144 patients before vascular surgery and before discharge. The study end point was the occurrence of cardiovascular death during a median follow-up period of 13 months (interquartile range 5 to 20). Preoperatively, the median NT-pro-BNP level in the study population was 314 pg/ml (interquartile range 136 to 1,351), which increased to a median level of 1,505 pg/ml (interquartile range 404 to 6,453) before discharge. During the follow-up period, 29 patients (20%) died, 27 (93%) from cardiovascular causes. The median difference in NT-pro-BNP in the survivors was 665 pg/ml, compared to 5,336 pg/ml in the patients who died (p = 0.01). Multivariate Cox regression analyses, adjusted for cardiac history and cardiovascular risk factors (age, angina pectoris, myocardial infarction, stroke, diabetes mellitus, renal dysfunction, body mass index, type of surgery and the left ventricular ejection fraction), demonstrated that the difference in NT-pro-BNP level between pre- and postoperative measurement was the strongest independent predictor of cardiac outcome (hazard ratio 3.06, 95% confidence interval 1.36 to 6.91). In conclusion, the change in NT-pro-BNP, indicated by repeated measurements before surgery and before discharge is the strongest predictor of cardiac outcomes in patients who undergo vascular surgery.

Sudden death during follow-up after new-onset ventricular tachycardia in vascular surgery patients.

BACKGROUND: Vascular surgery patients are at increased risk for late sudden cardiac death. Identification of patients at risk during surgery offers the opportunity for focused therapy. METHODS: We monitored 483 vascular surgery patients who had no documented history of arrhythmias to identify perioperative new-onset ventricular tachyarrhythmia (VT) and myocardial ischemia using a continuous electrocardiographic (ECG) device for 72 hours. Cardiac risk factors, left ventricular ejection fraction (LVEF), medical therapy, inflammation status, and perioperative ischemia in relation to arrhythmia were noted in all patients. During follow-up, event-based outcomes analysis was used to describe survival. RESULTS: New-onset perioperative VT was detected in 33 patients (6.8%). A higher percentage of patients experiencing perioperative VT had reduced LVEF preoperatively than those without VT (24% vs 12%; P = .04). Additionally, fewer patients experiencing VT were receiving statins than those without (70% vs 85%; P = .02). Patients experiencing VT had a higher incidence of myocardial ischemia (30% vs 18%; P = .10). Perioperative VT was preceded by ischemia in only 60% of the cases. The overall cohort survival was 83% at 24-month follow-up (interquartile range [IQR], 1.1-1.3). Sudden cardiac death free survival among patients experiencing VT was less than in those without (79% vs 92%; P = .02). After adjusting for gender, cardiac risk factors, and type of surgery, new-onset perioperative VT was associated with sudden cardiac death (hazard ratio [HR], 2.6; 95% confidence interval [CI], 1.1-5.8). CONCLUSION: Perioperative VT is likely to be associated with late sudden cardiac death and decreased survival. Continuous perioperative ECG is an effective method to identify VT and may allow improved management of these patients.

Timing of pre-operative Beta-blocker treatment in vascular surgery patients: influence on post-operative outcome.

OBJECTIVES: This study evaluated timing of ß-blocker initiation before surgery and its relationship with: 1) pre-operative heart rate and high-sensitivity C-reactive-protein (hs-CRP) levels; and 2) post-operative outcome. BACKGROUND: Perioperative guidelines recommend ß-blocker initiation days to weeks before surgery, on the basis of expert opinions. METHODS: In 940 vascular surgery patients, pre-operative heart rate and hs-CRP levels were recorded, next to timing of ß-blocker initiation before surgery (0 to 1, >1 to 4, >4 weeks). Pre- and post-operative troponin-T measurements and electrocardiograms were performed routinely. End points were 30-day cardiac events (composite of myocardial infarction and cardiac mortality) and long-term mortality. Multivariate regression analyses, adjusted for cardiac risk factors, evaluated the relation between duration of ß-blocker treatment and outcome. RESULTS: The ß-blockers were initiated 0 to 1, >1 to 4, and >4 weeks before surgery in 158 (17%), 393 (42%), and 389 (41%) patients, respectively. Median heart rate at baseline was 74 (±17) beats/min, 70 (±16) beats/min, and 66 (±15) beats/min (p < 0.001; comparing treatment initiation >1 with <1 week pre-operatively), and hs-CRP was 4.9 (±7.5) mg/l, 4.1 (±.6.0) mg/l, and 4.5 (±6.3) mg/l (p = 0.782), respectively. Treatment initiated >1 to 4 or >4 weeks before surgery was associated with a lower incidence of 30-day cardiac events (odds ratio: 0.46, 95% confidence interval [CI]: 0.27 to 0.76, odds ratio: 0.48, 95% CI: 0.29 to 0.79) and long-term mortality (hazard ratio: 0.52, 95% CI: 0.21 to 0.67, hazard ratio: 0.50, 95% CI: 0.25 to 0.71) compared with treatment initiated <1 week pre-operatively. CONCLUSIONS: Our results indicate that ß-blocker treatment initiated >1 week before surgery is associated with lower pre-operative heart rate and improved outcome, compared with treatment initiated <1 week pre-operatively. No reduction of median hs-CRP levels was observed in patients receiving ß-blocker treatment >1 week compared with patients in whom treatment was initiated between 0 and 1 week before surgery.

Screening value of N-terminal pro-B-type natriuretic peptide as a predictor of perioperative cardiac events after noncardiac surgery.

Preoperative cardiac risk assessment is the cornerstone of rationale perioperative management that guides invasive surgical interventions. In addition to clinical risk factors, a simple screening biomarker would be useful for identifying those surgical patients who might benefit from additional cardiac testing or therapeutic interventions. Preoperative plasma levels of N-terminal pro-B-type natriuretic peptide (NT-proBNP) are predictors of cardiac events after noncardiac surgery. NT–proBNP is synthesized in the ventricular myocardium in response to ventricular wall stress. To further increase the diagnostic accuracy of NT-proBNP for preoperative screening, it is important to identify confounding factors that influence NT-proBNP levels and their interaction with identifying risks for adverse cardiac events. Moreover, until now the available data from previous studies has been unable to consistently recognize the optimal discriminatory threshold for NT-proBNP. Currently, the ongoing DECREASE-VI study is conducted to evaluate whether current preoperative risk stratification can be improved by incorporating NT-proBNP measurements.

The efficacy and safety of clopidogrel in vascular surgery patients with immediate postoperative asymptomatic troponin T release for the prevention of late cardiac events: Rationale and design of the Dutch Echocardiographic Cardiac Risk Evaluation Applying Stress Echo-VII (DECREASE-VII) trial.

BACKGROUND: Major vascular surgery patients are at high risk for developing asymptomatic perioperative myocardial ischemia reflected by a postoperative troponin release without the presence of chest pain or electrocardiographic abnormalities. Long-term prognosis is severely compromised and characterized by an increased risk of long-term mortality and cardiovascular events. Current guidelines on perioperative care recommend single antiplatelet therapy with aspirin as prophylaxis for cardiovascular events. However, as perioperative surgical stress results in a prolonged hypercoagulable state, the postoperative addition of clopidogrel to aspirin within 7 days after perioperative asymptomatic cardiac ischemia could provide improved effective prevention for cardiovascular events. STUDY DESIGN: DECREASE-VII is a phase III, randomized, double-blind, placebo-controlled, multicenter clinical trial designed to evaluate the efficacy and safety of early postoperative dual antiplatelet therapy (aspirin and clopidogrel) for the prevention of cardiovascular events after major vascular surgery. Eligible patients undergoing a major vascular surgery (abdominal aorta or lower extremity vascular surgery) who developed perioperative asymptomatic troponin release are randomized 1:1 to clopidogrel or placebo (300-mg loading dose, followed by 75 mg daily) in addition to standard medical treatment with aspirin. The primary efficacy end point is the composite of cardiovascular death, stroke, or severe ischemia of the coronary or peripheral arterial circulation leading to an intervention. The evaluation of long-term safety includes bleeding defined by TIMI criteria. Recruitment began early 2010. The trial will continue until 750 patients are included and followed for at least 12 months. SUMMARY: DECREASE-VII is evaluating whether early postoperative dual antiplatelet therapy for patients developing asymptomatic cardiac ischemia after vascular surgery reduces cardiovascular events with a favorable safety profile.

Influence of left ventricular dysfunction (diastolic versus systolic) on long-term prognosis in patients with versus without diabetes mellitus having elective peripheral arterial surgery.

Diabetes mellitus (DM) and left ventricular dysfunction (LVD) are often coexistent and invariably associated with increased mortality. Data on long-term prognosis of "isolated" diastolic LVD in diabetics are lacking; therefore, we evaluated these prognostic implications in patients with peripheral arterial disease (PAD) and DM. Using echocardiography, 1321 patients were screened for diastolic, systolic (ejection fraction <50%) or combined LVD. Diastolic LVD was diagnosed based on the ratio of early rapid filling to late filling due to atrial contraction, pulmonary vein flow, and deceleration time. Patients using glucose-lowering drugs or insulin or with a fasting glucose level >6.1 mmol/L were diagnosed with DM. The primary end point was occurrence of cardiovascular death during a mean follow-up of 2.5 +/- 1.9 years. In the total population, DM was diagnosed in 518 patients (39%), and diastolic, systolic, or combined LVD was present in 356 patients (27%), 102 patients (8%), or 156 patients (12%), respectively. In diabetic patients, diastolic and systolic LVDs were associated with increased cardiovascular mortality (hazard ratio 1.8, 95% confidence interval 1.03 to 3.03; hazard ratio 3.1, 95% confidence interval 1.46 to 6.38). In nondiabetic patients, the same association between diastolic or systolic LVD and outcome was observed (hazard ratio 2.2, 95% confidence interval 1.30 to 3.74; hazard ratio 3.9, 95% confidence interval 2.00 to 7.52). Combined systolic and diastolic LVD had the worst prognosis. In conclusion, diabetic patients with PAD have an increased prevalence of isolated systolic and combined LVD. In patients with PAD the presence of isolated diastolic, systolic, or combined LVD was independently and equally associated with increased cardiovascular mortality, irrespective of the concomitant presence of DM.

European Society of Cardiology 2009 guidelines for preoperative cardiac risk assessment and perioperative cardiac management in noncardiac surgery: key messages for clinical practice.

Patients undergoing noncardiac surgery are at risk of adverse perioperative and long-term outcome. When considering a patient for noncardiac surgery, a careful preoperative clinical risk evaluation and subsequent risk-reduction strategies are essential to reduce postoperative complications. To assist physicians with decision making, clinical guidelines are developed. The aim of clinical guidelines is to improve patient care by providing recommendations about appropriate healthcare in specific circumstances. Development of clinical guidelines is an important component in improving the quality of care. By translating the best available scientific evidence into specific recommendations, guidelines can serve as a useful tool to achieve effective and efficient patient care. In 2009, the first European Society of Cardiology guidelines on perioperative care were developed. This decisionmaking process integrates clinical markers, early coronary evaluation, functional capacity, and the type of surgery involved.