Ian Ryder

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

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.

Haemodynamic changes during beating heart coronary surgery with the ‘Bristol Technique’

OBJECTIVES Optimal exposure and stabilization of the target coronary vessel is essential to allow the construction of a precise coronary anastomosis during off pump coronary surgery. However, this might be achieved at the expense of significant haemodynamic deterioration, particularly while grafting the circumflex and the posterior descending coronary arteries. The present study was designed to assess the haemodynamic changes with the beating heart positioned for grafting the three main coronaries. METHODS Twenty-nine consecutive patients (21 male, mean age 62.6+/-7.1 years) undergoing off pump coronary surgery were enrolled in the study. Three different surgical settings of exposure and stabilization were used according to the site of anastomosis: left anterior descending (LAD - set-up 1; n=29), posterior descending (PDA - set-up 2; n=15), and circumflex (Cx - set-up 3; n=21) coronary arteries. Haemodynamic measurements were recorded before any cardiac manipulation (baseline) in set-ups 1, 2 and 3, and immediately after the completion of each distal anastomosis with the heart returned to its anatomical position. RESULTS There were no marked changes in heart rate (HR) and systemic mean arterial pressure during the construction of the anastomoses for any of the three surgical settings. Set-up 1 (LAD) showed a decrease of 15.5% in stroke volume (SV) and an increase of 9% in pulmonary capillary wedge pressure (PCWP) compared to baseline (both P<0.05), with all the other haemodynamic parameters remaining unchanged. Set-up 2 (PDA) showed a marked decrease in SV and cardiac index (CI), and an increase in central venous pressure (CVP) when compared to baseline (all P<0.05). The most extensive changes were observed in set-up 3 (Cx) with a considerable reduction in SV and CI, and an increase in CVP, PCWP, pulmonary arterial pressure, and systemic vascular resistance index (all P<0.05). These haemodynamic changes were transient and totally recovered after the heart was returned to its anatomical position. CONCLUSIONS Exposure and stabilization of the three main coronary arteries during beating heart surgery does not produce any appreciable change in systemic blood pressure and HR. The haemodynamic deterioration observed during the construction of the circumflex and posterior descending coronary arteries distal anastomoses is transient and well tolerated with no adverse clinical events.

Thoracic Epidural Anesthesia Improves Early Outcomes in Patients Undergoing Off-pump Coronary Artery Bypass Surgery: A Prospective, Randomized, Controlled Trial

Background:The aim of this two-center, open, randomized, controlled trial was to evaluate the impact of thoracic epidural anesthesia on early clinical outcomes in patients undergoing off-pump coronary artery bypass surgery. Methods:Two hundred and twenty-six patients were randomized to either general anesthesia plus epidural (GAE) (n = 109) or general anesthesia only (GA) (n = 117). The primary outcome was length of postoperative hospital stay. Secondary outcomes were: arrhythmia, inotropic support, intubation time, perioperative myocardial infarction, neurologic events, intensive care stay, pain scores, and analgesia requirement. Results:Baseline characteristics were similar in the two groups. One patient died in the GAE group. Median postoperative stay was significantly reduced in the GAE, compared with the GA, group (5 days, interquartile range [5–6] vs. 6 days, interquartile range [5–7], hazard ratio = 1.39, 95% CI [1.06–1.82]; P = 0.017). The incidence of arrhythmias and the median intubation time were both significantly lower in the GAE, compared with the GA, group (odds ratio = 0.41, 95% CI [0.22–0.78], P = 0.006 and hazard ratio = 1.73, 95% CI [1.31–2.27], P < 0.001, respectively). Patients in the GAE group were more likely to need vasoconstrictors intraoperatively than in the GA group (odds ratio = 2.50, 95% CI [1.22–5.12]; P = 0.012). The GAE, compared with GA, group reported significantly lower levels of impairment for all pain domains and reduced morphine usage (odds ratio = 0.07, 95% CI [0.03–0.17]; P < 0.001). Conclusion:In patients undergoing off-pump coronary artery bypass surgery, the addition of thoracic epidural to general anesthesia significantly reduces the incidence of postoperative arrhythmias and improves pain control and overall quality of recovery, allowing earlier extubation and hospital discharge.

Case 1—1997 Diagnosis and management of dynamic hyperinflation during lung transplantation

A 22-year-old, 40-kg man with end-stage infective lung disease secondary to cystic fibrosis, presented for bilateral sequential lung transplantation (BSLTx). He had chronic hypercapneic respiratory failure with cor pulmonale and was dependent on home oxygen therapy. He had been admitted to the hospital 3 days earlier with a severe exacerbation of his condition. His preoperative values were as follows: hemoglobin 13.3 g/dL; arterial blood gases (room air) pH 7.36, arterial oxygen tension (Pao2) 50 mmHg, arterial carbon dioxide tension (Paco2) 72 mmHg, bicarbonate 41 mmol/L; and pulmonary function testing (forced vital capacity 1.76 L [37% predicted], forced expriatory volume in 1 second 0.84 [20% predicted], midexpiratory flow rate 0.21 L/s [4% predicted]). Other monitors included chest x-ray (gross cystic bronchiectasis with patchy consolidation), electrocardiogram (sinus rhythm and right-axis deviation), transthoracic echocardiogram (normal left ventricular function, mild right ventricular enlargement, and mild tricuspid regurgitation), and gated cardiac blood pool scan (at rest) (left ventricular ejection fraction 43%, right ventricular ejection fraction 40%). The patient was premedicated with temazepam and 0.3 M of sodium citrate and was transferred to the operating room with oxygen administered by face mask. A midthoracic epidural catheter and intravascular catheters were inserted with local anesthesia, although no epidural agents were used until after the procedure, and routine invasive monitoring was established. A low-dose dopamine infusion, 3 pg/kg/min, was then commenced to optimize renal blood flow, and methylprednisolone, 500 rag, was slowly administered.