Malcolm J. Underwood

Inflammatory response after coronary revascularization with or without cardiopulmonary bypass

BACKGROUND We sought to investigate the effect of multiple coronary artery bypass grafting (CABG) with or without cardiopulmonary bypass (CPB) on the perioperative inflammatory response. METHODS Sixty patients undergoing CABG were randomly assigned to one of two groups: (A) on pump with conventional CPB and cardioplegic arrest, and (B) off pump on the beating heart. Serum samples were collected for estimation of neutrophil elastase, interleukin 8 (IL-8), C3a, and C5a preoperatively and at 1, 4, 12, and 24 hours postoperatively. Furthermore, white blood cell (WBC), neutrophil, and monocyte counts were carried out preoperatively and at 1, 12, 36 and 60 hours postoperatively. Overall incidence of infection and perioperative clinical outcome were also recorded. RESULTS The groups were similar in terms of age, weight, gender ratio, extent of coronary disease, left ventricular function, and number of grafts per patient. Neutrophil elastase concentration peaked early after CPB in the on-pump group, with a decline with time. Repeated-measures analysis of variance between groups and comparisons at each time point (modified Bonferroni) showed elastase concentrations were significantly higher in the on-pump than the off-pump group (both p < 0.0001). IL-8 increased significantly after surgery in the on-pump group, with no decline during the observation period (p = 0.01 vs off pump). C3a and C5a rose early after surgery in both groups when compared with baseline values. Postoperative WBC, neutrophil, and monocyte counts were significantly higher in the on-pump than the off-pump group (p < 0.01). Finally, the incidence of postoperative overall infections was significantly higher in the on-pump group (p < 0.0001 vs off pump). CONCLUSIONS CABG on the beating heart is associated with a significant reduction in inflammatory response and postoperative infection when compared with conventional revascularization with CPB and cardioplegic arrest.

Economic outcome of off-pump coronary artery bypass surgery: a prospective randomized study

BACKGROUND Emphasis on cost containment in coronary artery bypass surgery is becoming increasingly important in modern hospital management. The revival of interest in off-pump (beating heart) coronary artery bypass surgery may influence the economic outcome. This study examines these effects. METHODS Two hundred patients undergoing first-time coronary artery bypass surgery were prospectively randomized to either conventional cardiopulmonary bypass and cardioplegic arrest or off-pump surgery. Variable and fixed direct costs were obtained for each group during operative and postoperative care. The data were analyzed using parametric methods. RESULTS There was no difference between the groups with respect to pre- and intraoperative patient variables. Off-pump surgery was significantly less costly than conventional on-pump surgery with respect to operating materials, bed occupancy, and transfusion requirements (total mean cost per patient: on pump,

Serum S-100 protein release and neuropsychologic outcome during coronary revascularization on the beating heart: a prospective randomized study

3,731.6+/-1,169.7 vs off-pump,

Prevention of spinal cord ischaemia during descending thoracic and thoracoabdominal aortic surgery

2,615.13+/-953.6; p < 0.001). Morbidity was significantly higher in the on-pump group, which was reflected in an increased cost. CONCLUSIONS Off-pump revascularization offers a safe, cost-effective alternative to conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest.

Off-pump coronary operations can be safely taught to cardiothoracic trainees

OBJECTIVES Our purpose was to establish whether coronary revascularization on the beating heart without cardiopulmonary bypass is less harmful to the brain than conventional surgery with cardiopulmonary bypass as indicated by measures of cognitive function or by changes in serum concentrations of S-100 protein, a recognized biochemical marker of cerebral injury. METHODS We conducted a prospective randomized trial in which the assessors of the outcome measures were blind to the treatment received. Sixty patients without known neurologic abnormality, undergoing coronary revascularization, were prospectively randomized to 1 of 2 groups: (1) cardiopulmonary bypass (32 degrees C-34 degrees C) and cardioplegic arrest (on pump) with intermittent antegrade warm blood cardioplegia or (2) surgery on the beating heart (off pump). Neuropsychologic performance was assessed before and 12 weeks after the operation. Serum S-100 protein concentration was measured at intervals up to 24 hours after the operation. RESULTS The groups had similar preoperative characteristics. There were no deaths or major neurologic complications in either group, nor was there any difference between groups in the chosen index of neurologic deterioration. Serum S-100 protein concentrations were higher in the on-pump group at 30 minutes, but any such difference between groups had disappeared 4 hours later. The extent of the changes in S-100 protein was unrelated to the index of neuropsychologic deterioration. CONCLUSIONS The changes in S-100 protein concentration suggest that the brain and/or blood-brain barrier may be more adversely affected during coronary artery surgery with cardiopulmonary bypass than during surgery on the beating heart, but that this may not be reflected in detectable neuropsychologic deterioration at 12 weeks.

Effect of intraluminal application of tissue-type plasminogen activator on the fibrinolytic activity of experimental vein grafts

Surgery of the descending and thoracoabdominal aorta has been associated with post-operative paraparesis or paraplegia. Different strategies, which can be operative or non-operative, have been developed to minimise the incidence of neurological complications after aortic surgery. This review serves to summarise the current practice of spinal cord protection during surgery of the descending thoracoabdominal aortic surgery. The pathophysiology of spinal cord ischaemia will also be explained. The incidence of spinal cord ischaemia and subsequent neurological complications was associated with (1) the duration and severity of ischaemia, (2) failure to establish spinal cord supply and (3) reperfusion injury. The blood supply of the spinal cord has been extensively studied and the significance of the artery of Adamkiewicz (ASA) being recognised. This helps us to understand the pathophysiology of spinal cord ischaemia during descending and thoracoabdominal aortic operation. Techniques of monitoring of spinal cord function using evoked potential have been developed. Preoperative identification of ASA facilitates the identification of critical intercostal vessels for reimplantation, resulting in re-establishment of spinal cord blood flow. Different surgical techniques have been developed to reduce the duration of ischaemia and this includes the latest transluminal techniques. Severity of ischaemia can be minimised by the use of CSF drainage, hypothermia, partial bypass and the use of adjunctive pharmacological therapy. Reperfusion injury can be reduced with the use of anti-oxidant therapy. The aetiology of neurological complications after descending and thoracoabdominal aortic surgery has been well described and attempts have been made to minimise this incidence based on our knowledge of the pathophysiology of spinal cord ischaemia. However, our understanding of the development and prevention of these complications require further investigation in the clinical setting before surgery on descending and thoracoabdominal aorta to be performed with negligible occurrence of these disabling neurological problems.

Hybrid Antegrade Thoracic Aortic Stenting via a Temporary Ascending Aortic Graft Conduit for a Patient with Poor Peripheral Vascular Access

BACKGROUND Off-pump coronary artery bypass (OPCAB) operations are evolving rapidly and becoming established in many cardiothoracic centers. For the technique to be widely applicable, teaching methods must be developed for surgical trainees. Early and midterm clinical outcomes of OPCAB performed at our institution by trainees as first operators under supervision were compared to those obtained in patients operated on by consultants. METHODS Analysis was undertaken on data prospectively inserted in the Patient Analysis & Tracking System. Of the 559 OPCAB operations performed between January 1997 and May 2000, 124 (22%) were carried out by a supervised trainee and 435 (78%) by a consultant. RESULTS There was no difference in age, sex, angina class, New York Heart Association functional class, or operative priority and extent of coronary artery disease in the two groups. More patients operated on by consultants had a history of congestive heart failure requiring medical therapy, significantly lower ejection fraction, and higher Parsonnet score compared with patients operated on by trainees. Early and midterm clinical results, in terms of morbidity and mortality, were similar in patients operated on by trainees or by consultants. CONCLUSIONS Our data show no differences in early and midterm clinical outcome for patients undergoing OPCAB operations performed either by consultants or by trainees under supervision. The improvements in exposure and stabilization techniques, as well as the use of intracoronary shunts, have made it possible and safe to teach trainees off-pump multivessel coronary artery revascularization.

Acute Aortic Syndrome

OBJECTIVE The aim was to quantify the effect of intraluminally applied tissue-type plasminogen activator (tPA) on the fibrinolytic activity of experimental vein grafts and assess the effect of pretreatment of the vein on early platelet and thrombus formation using histological techniques. METHODS A pig model of bilateral saphenous venin-carotid artery grafts was used. In each animal one side of the neck was grafted using vein distended to 230 mm Hg and pretreated with tPA (1 mg.ml-1) for a period of 15 min before grafting (treated graft). The perfused in situ for 2 h after implantation and before analysis. Changes in local fibrinolytic activity were quantified using fibrin plate techniques and specific chromogenic assays for tPA and urokinase (uPA) in tissue extract (n = 6 animals). Histological assessment was made using light and scanning microscopy (n = 4 animals). RESULTS Surgical preparation and distention significantly reduced the fibrinolytic activity of pig saphenous vein in terms of areas of lysis produced on fibrin plates (P < 0.05), tPA activity (P < 0.05), and uPA activity (P < 0.05). Pretreatment of distended vein with tPA before grafting significantly enhanced its fibrinolytic activity after 2 h perfusion compared to control (untreated) grafts, as assessed by areas of lysis on fibrin plates (P < 0.05) and specific tPA activity (P < 0.05). Treated grafts also showed qualitatively less platelet and thrombus formation on histological examination. CONCLUSIONS Pretreatment of surgically harvested vein by intraluminal application of tPA before grafting enhances its fibrinolytic activity after exposure to 2 h perfusion in vivo. This technique requires further investigation to validate its potential as a means of providing local anticoagulation to veins implanted as arterial grafts thereby reducing the incidence of early graft thrombosis.

Autogenous arterial grafts for coronary bypass surgery: current status and future perspectives.

In patients with poor peripheral vascular access, thoracic aortic stenting procedures can be technically very challenging. Antegrade aortic stent deployments during concomitant open ascending and arch procedures are well described, but the issue of long endovascular catheters and wires may make such an approach difficult and awkward. We describe a novel hybrid method involving a temporary graft conduit to the ascending aorta which is brought caudal toward the foot of the table to facilitate antegrade deployment of the thoracic stent graft.

Complex Reoperative Thoracic Aortic Surgery

Abstract The acute aortic syndrome consists of a spectrum of pathologies characterized by disruption in the integrity of the aortic wall, which may be associated with complications including ischemia, rupture, and death [1]. It comprises classical aortic dissection, intramural hematoma (IMH), penetrating aortic ulcer (PAU), acute aneurysm expansion, and traumatic aortic transection. Among these entities, aortic dissection is the commonest and entails significant morbidity and mortality if not appropriately treated. The emergence of advanced diagnostics and imaging along with advances in surgical technique and the rapidly expanding field of endovascular treatment mean we have a better understanding of the pathophysiology, natural history, and management of acute aortic syndrome, resulting in improved clinical outcomes. In this chapter, we review the epidemiology, pathophysiology, and clinical management of acute aortic syndrome, with particular emphasis on dissection, IMH, and PAU.