Theodore Velissaris

A prospective randomized study to evaluate splanchnic hypoxia during beating-heart and conventional coronary revascularization

OBJECTIVE Cardiopulmonary bypass (CPB) is associated with gut mucosal hypoxia, which may contribute to gastrointestinal complications. We examined gastric mucosal oxygenation together with whole-body oxygen flux in low-risk patients undergoing coronary artery bypass grafting (CABG) with and without CPB. METHODS Fifty-four patients undergoing primary CABG by the same surgeon were randomized into either on-pump (ONCAB, n=27) or off-pump (OPCAB, n=27) groups. The ONCAB group underwent mild hypothermic (35 degrees C) pulsatile CPB with arterial line filtration. Each patient underwent perioperative monitoring with continuous tonometry and cardiac output devices. Gastric intramucosal pH (pHi), gastric-arterial carbon dioxide partial pressure difference (CO(2) gap), whole-body oxygen delivery (DO(2)) and consumption (VO(2)) and whole-body oxygen extraction fraction were measured at sequential time-points intraoperatively and up to 6 h postoperatively. Anaesthetic management was standardized. RESULTS Both groups had similar demographic makeup and extent of revascularization (ONCAB 2.6+/-0.9 grafts versus OPCAB 2.5+/-0.8 grafts; P=0.55). The ONCAB group had a mean (+/-SD) CPB time of 62+/-25 min and aortic cross-clamp time of 32+/-11 min. In both groups there was a similar and progressive drop in pHi intraoperatively. Postoperatively, there was a gradual separation between the groups with ONCAB patients showing no further decline in pHi, while further deterioration was observed in the OPCAB group up to 6 h postoperatively. There was a significant difference between the groups over time (P=0.03). There was a corresponding progressive rise in CO(2) gap perioperatively in both groups, with ONCAB patients demonstrating superior preservation of gastric mucosal oxygenation in the early postoperative period. Global oxygen utilization measurements showed superior DO(2) and VO(2) in the OPCAB group throughout the study. CONCLUSIONS Despite superior global oxygen flux associated with beating-heart revascularization, gastric mucosal hypoxia occurred to similar extents in both groups with worsening trends for the OPCAB patients postoperatively. The splanchnic pathophysiology during beating-heart revascularization should be further explored.

A prospective randomized study to evaluate stress response during beating-heart and conventional coronary revascularization

BACKGROUND Cardiopulmonary bypass (CPB) is associated with a systemic stress hormonal response, which can lead to changes in hemodynamics and organ perfusion. We examined perioperative stress hormone release in low-risk patients undergoing coronary artery bypass grafting with and without cardiopulmonary bypass. METHODS Fifty-two patients undergoing primary coronary artery bypass grafting by the same surgeon were randomly assigned into either on-pump (n = 26) or off-pump (n = 26) groups. The on-pump coronary artery bypass grafting group underwent mildly hypothermic (35 degrees C) pulsatile cardiopulmonary bypass with arterial line filtration. Arterial blood samples were collected preoperatively, at the end of operation, and at 1, 6, and 24 hours postoperatively. Plasma levels of vasopressin and cortisol were measured using radioimmunoassay. Anesthetic management was standardized. RESULTS Both groups had similar demographic makeup and extent of revascularization (on-pump coronary artery bypass grafting, 2.8 +/- 1.0 grafts versus off-pump coronary artery bypass grafting, 2.4 +/- 0.9 grafts; p = 0.20). No mortality or major morbidity was observed and there were no crossovers. The cardiopulmonary bypass and aortic cross-clamp times in the on-pump coronary artery bypass grafting group were 63 +/- 24 and 33 +/- 11 minutes, respectively. In both groups there was a similar and significant rise in cortisol and vasopressin levels in the early postoperative phase, with a partial recovery toward baseline values observed at 24 hours postoperatively. Repeated measures analysis of covariance showed no significant difference between the groups with time for both hormones (cortisol, p = 0.40; vasopressin, p = 0.30). CONCLUSIONS Despite the avoidance of cardiopulmonary bypass, off-pump coronary artery bypass grafting surgery triggers a systemic stress hormone response that is comparable to conventional surgical revascularization. The neurohormonal environment during beating-heart surgery should be further explored.

Traumatic sternal fracture: outcome following admission to a Thoracic Surgical Unit

INTRODUCTION We reviewed our experience of the in-hospital management and early follow-up of patients admitted with a traumatic sternal fracture to a Thoracic Surgical Unit. PATIENTS AND METHODS Over a 7-year period, 73 consecutive patients (51 males) with a median age of 51 (range 17-84) years were admitted through the Emergency Department with an acute traumatic sternal fracture. The patients were hospitalised for cardiorespiratory monitoring, pain control and physiotherapy. Outpatient follow-up occurred 6 weeks after discharge. RESULTS The median hospital stay was 2 days (range 1-15 days). Sixty-four patients (88%) did not require parenteral analgesia or any other procedure that would necessitate admission to hospital. Three patients (4%) with severely displaced fractures and complex co-morbidities required surgical correction. Follow-up revealed no significant complications. CONCLUSIONS Admission to hospital is not necessary for every patient sustaining a sternal fracture and should be reserved for those with high-impact trauma, severely displaced fractures, significant associated injuries, complex analgesic requirements, important co-morbidities or inadequate domestic support.

Thyroid function during coronary surgery with and without cardiopulmonary bypass

OBJECTIVE Cardiopulmonary bypass (CPB) is associated with thyroid hormone changes consistent with euthyroid sick syndrome. Similar changes have been observed after general surgical operations. Thyroid hormone changes and their association with global oxygen consumption were studied in low-risk patients undergoing coronary artery bypass grafting (CABG) with and without CPB. METHODS Fifty-two patients undergoing primary CABG by the same surgeon were randomised into either on-pump (ONCAB, n=26) or off-pump (OPCAB, n=26) groups. Thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3) levels were measured at sequential time-points using chemiluminescence assays. Global oxygen consumption was measured at sequential time-points using a continuous cardiac output Swan-Ganz catheter. RESULTS In both groups TSH and fT4 remained within normal range throughout the study. There was a similar and progressive decline in fT3 levels with no significant difference between the groups over time (p=0.42). Mean fT3 levels at 24h were below the normal range and significantly lower than baseline values (ONCAB, 3.3+/-0.69 pmol/L vs 5.1+/-0.41 pmol/L, p<0.001; OPCAB, 3.3+/-0.51 pmol/L vs 5.0+/-0.46 pmol/L, p<0.001). There was a significant inverse relationship between fT3 levels and global oxygen consumption. CONCLUSIONS Off-pump surgery is associated with thyroid hormone changes similar to conventional surgical revascularisation. The data suggest that further studies into T3 administration during OPCAB may be warranted.

A saphenous vein graft aneurysm with fistula development to the right atrium: Surgical management of a rare bypass graft complication

A patient presented late following coronary artery bypass surgery with recurrent angina. Investigations revealed a saphenous vein graft aneurysm, which subsequently formed a fistula with the right atrium. This was managed by surgical excision and repair followed by regraft of the run-off territory. Intraoperatively, the left internal mammary artery, a patent graft to the left anterior descending artery, was isolated from the circulation during aortic cross-clamping by preoperative placement of a percutaneous balloon catheter within this graft. Surgery was successful and the patient was discharged symptom-free one week later.

Transventricular cannulation of the aorta: a useful technique in acute aortic dissection

A 39-year-old morbidly obese man suffered type-A acute aortic dissection. At operation, both external iliac and common femoral arteries were thrombosed. Transventricular cannulation of the ascending aorta provided the only means of maintaining adequate flow on cardiopulmonary bypass (CPB) to support an unusually high body mass index. This method of arterial cannulation for CPB was initially described in paediatric patients. We review the application of this technique in the adult population.

Carbamazepine-related hyponatremia following cardiopulmonary bypass.

Abstract A 67‐year‐old man on long‐term carbamazepine therapy underwent elective coronary artery bypass grafting. Following an initially uncomplicated recovery, he developed symptomatic hyponatremia. The symptoms and biochemical abnormality improved after gradual discontinuation of carbamazepine. We discuss the association between carbamazepine and hyponatremia and the causes of hyponatremia after cardiopulmonary bypass. Surgeons should consider stopping carbamazepine before operations with cardiopulmonary bypass. (J Card Surg 2003;18:155‐157)

Mitral valve replacement in severely calcified mitral valve annulus: a 10-year experience

OBJECTIVES Severe calcification in the mitral valve annulus is a challenging problem during mitral valve surgery. We describe our experience with mitral valve replacement in severely calcified mitral valve without decalcification of the annulus. METHODS Between April 2001 and July 2011, 61 patients underwent mitral valve replacement with severe mitral annulus calcification without decalcification of the annulus. This retrospective study was performed to assess the surgical and the long‐term postoperative outcomes in this group. RESULTS The mean age of the patients was 75.2 ± 9.2 years. Twenty‐four patients (53%) were in New York Heart Association Class III/IV. Twenty‐six patients (58%) had good left ventricular function. Mean logistic EuroSCORE was 8.75. Isolated mitral valve replacement was performed in 12 patients (27%). Coronary artery bypass grafting was done in 13 patients (29%). In‐hospital mortality was 4.9% (3 patients). Postoperative morbidity included re‐exploration for bleeding in 3 patients (7%) and transient renal impairment in 10 patients (22%). Three patients required intra‐aortic balloon pump (7%) for low cardiac output syndrome. Seven patients (16%) required permanent pacemaker, and 1 patient (2%) had thromboembolic event. The 1‐year survival was 93.3%, and the 5‐year survival was 78.8%. The mean echocardiography follow‐up was 40 months. There was no paravalvular leak detected in any patient in the long‐term follow‐up. None of the patients had valve‐related reoperation. CONCLUSIONS Mitral valve replacement without annular decalcification in severely calcified mitral valve annulus is a safe and an effective approach and has good long‐term outcome.

Early Prosthetic Valve Failure in a Patient with Rheumatoid Arthritis

Abstract  Heart lesions in patients with rheumatoid arthritis (RA) are well documented in literature; however, in the majority of cases these are incidental findings at postmortem. Most patients do not require cardiac surgical intervention unless they develop complications such as significant valvular regurgitation. Patients with RA often require orthopedic operations and therefore a bioprosthetic valve replacement is normally advocated to avoid problems related to anticoagulation. We report a case of a 64‐year‐old woman with seropositive RA who had undergone bioprosthetic aortic valve replacement three years previously. She re‐presented with early prosthetic valve failure due to accelerated degeneration and calcification. This was treated successfully with redo replacement with a mechanical prosthesis. Here, we discuss our experience and debate the various valve choices available that should be considered in patients with rheumatoid disease.

Haemodynamic changes during off-pump surgery

We read with great interest the article by Do et al. [1] on haemodynamic changes during off-pump coronary artery bypass surgery (OPCAB). A continuous cardiac output (CCO) Swan–Ganz catheter was used to assess cardiac output changes during distal anastomoses. One of the major limitations of thermodilution CCO catheters is that they do not provide continuous, real-time information. They provide intermittent measurements and it has been shown that the in vitro response time of a change in cardiac output is between 5 and 15 min [2]. Therefore the readings are accurate only in situations of haemodynamic stability, which cannot generally be assumed during cardiac manipulation and coronary grafting in OPCAB, especially when no intracoronary shunts are used. The period of distal anastomoses in OPCAB represents a dynamic period of continuous and very rapid haemodynamic changes. During that period administration of inotropes or vasoconstrictors is often required, as documented in the study by Do et al. Therefore, one of the continuous, real-time cardiac output monitoring techniques, such as the epiaortic ultrasonic probe or the LiDCO/PulseCO system, would be more valuable to track haemodynamic changes in OPCAB. The authors observed significant falls of the mean arterial pressure (MAP) and relative preservation of the cardiac index during grafting of the obtuse marginal (OM) and posterior descending (PDA) coronary arteries. This is contrary to findings from previous studies, which demonstrate that during cardiac manipulation MAP is better preserved than the cardiac output due to compensatory vasoconstriction [3,4]. The authors give us no information on systemic vascular resistance changes, although one would expect compensatory changes, especially as nearly half the patients received vasopressors during the OM and PDA anastomoses. The cardiac index changes were assessed in a subgroup of ten patients, while MAP changes were measured in the entire cohort of 55 patients. It would therefore be useful to know whether the subgroup of ten patients was representative of the entire sample, particularly in terms of left ventricular function. Moreover, during cardiac elevation in OPCAB there is considerable compression and distortion of the right cardiac chambers [5]. This may lead to tricuspid regurgitation, which would render thermodilution measurements of the cardiac output falsely high. It would be useful to know whether the tricuspid valve function was assessed during the TOE examination which was undertaken in six patients in this study or whether the authors have previously assessed valvular function with their technique for cardiac elevation. Studies on haemodynamic changes during OPCAB are essential and will enable us to develop superior techniques of performing beating-heart surgery. However, the use of thermodilution catheters for cardiac output monitoring has important methodological limitations. We urge future investigators to use real-time cardiac output monitoring for evaluation of dynamic haemodynamic alterations during OPCAB. Real-time cardiac output monitoring will enable tracking of haemodynamic changes, facilitating dynamic therapeutic interventions to optimize cardiac performance.