Effect of prehabilitation-related DIETary protein intake on Quality of Recovery after elective cardiac surgery (DIETQoR) study: protocol of a randomised controlled trial

INTRODUCTION

Protein malnutrition is associated with higher risks of postoperative complications, mortality, prolonged postoperative stays in hospital, slower physical and mental recovery after surgery and lower subsequent health-related quality of life. To reduce the risk of postoperative morbidity and mortality, nutritional prehabilitation programmes have been developed recently to build up patient's nutritional reserve to withstand the stress of surgery. The intervention involves nutritional screening and counselling, and increasing dietary protein intake in protein-malnourished patients in the several weeks before surgery. However, there are few well-conducted preoperative studies to examine the effect of increasing dietary protein intake on the quality of recovery of malnourished patients after elective cardiac surgery.

METHOD AND ANALYSIS

This randomised controlled trial of malnourished patients undergoing major elective cardiac surgery will compare the quality of postoperative recovery in patients with or without nutritional prehabilitation. One hundred and thirty-two patients will be randomised to receive nutritional prehabilitation (target-adjusted whey protein powder supplementation and an individualised 1 hour session/week counselling by a dietician 1 month before operation date) or standard care (no nutritional prehabilitation). Primary outcomes will be the quality of recovery after surgery (15-item Quality of Recovery) on the third postoperative day. Secondary outcomes will include days (alive and) at home within 30 days, changes in the WHO Disability Assessment Schedule 2.0, changes in health-related quality of life (EQ-5D) and Cardiac Postoperative Morbidity Survey. An outcomes assessor will be blinded to the treatment allocation. Appropriate univariate analyses, generalised estimating equations and multiple regressions will be performed for intention-to-treat and per-protocol analyses.

ETHICS AND DISSEMINATION

The Joint CUHK-NTEC Clinical Research Ethics Committee approved the study protocol (CREC Ref. No.: 2021.703 T). The findings will be presented at scientific meetings, peer-reviewed journals and to study participants.

TRIAL REGISTRATION NUMBER

ChiCTR2200057463.

Hepatorenal dysfunction predicts operative mortality after triple valve surgery: Utility of MELD-Na

BACKGROUND

Despite significant advancements in operative techniques and myocardial protection, triple valve surgery (TVS) remains a formidable operation with a relatively high in-hospital mortality. We evaluated the prognostic value of Model for End-stage Liver Disease score including sodium (MELD-Na) for mortality after TVS and its predictive value when incorporated in the EuroSCORE risk model.

METHODS

We performed a retrospective cohort study of 61 consecutive patients who underwent TVS from November 2005 to June 2016. Demographics, clinical, biochemical, and operative data were collected and analyzed.

RESULTS

Median follow-up duration was 8.0 years. The majority (70.5%) of patients suffered from rheumatic heart disease and underwent mechanical double valve replacement with tricuspid valve repair. There were six operative deaths (9.84%), with the most common cause of death being multiorgan failure (83.3%). In 26.2% of the cohort, the MELD-Na score was moderately elevated at 9 to 15. A small fraction (4.9%) had a severely elevated MELD-Na greater than 15. Patients with a MELD-Na greater than 9 had a higher unadjusted rate of operative mortality, prolonged ventilation, need for dialysis and acute liver failure after TVS. Hierarchical logistic regression was performed using logistic EuroSCORE as the base model. After risk adjustment, each point of MELD-Na score increase was associated with 1.405 times increase in odds of operative mortality. The regression analysis was repeated by incorporating individual components of the MELD-Na score, including bilirubin, sodium, and albumin. All three biochemical parameters were significantly associated with operative mortality CONCLUSION: MELD-Na score as a quantifier of hepatorenal dysfunction is sensitive and specific for operative mortality after triple valve surgery.

Effect of preparative rehabilitation on recovery after cardiac surgery: A systematic review

BACKGROUND

Physical prehabilitation (preparative rehabilitation) programs may have beneficial effects on enhancing physical strength and functional status before surgery, but their effects on postoperative recovery are unclear.

OBJECTIVES

This systematic review investigated the effectiveness of physical prehabilitation programs before cardiac surgery on postoperative recovery and other perioperative outcomes.

METHODS

We searched for reports of randomised controlled trials of any prehabilitation programs that included physical activity or an exercise training component in adults undergoing elective cardiac surgery, published in any language, from six bibliographic databases (last search on June 20, 2019). We assessed trials for risk of bias, overall certainty of evidence and quality of intervention reporting using the Cochrane Risk of Bias Assessment Tool, GRADE system and the Template for Intervention Description and Replication checklist and guide, respectively.

RESULTS

All 7 studies (726 participants) were at high risk of bias because of lack of blinding. The quality of prehabilitation reporting was moderate because program adherence was rarely assessed. The timing of prehabilitation ranged from 5 days to 16 weeks before surgery and from face-to-face exercise prescription to telephone counselling and monitoring. We found uncertain effects of prehabilitation on postoperative clinical outcomes (among the many outcomes assessed): perioperative mortality (Peto odds ratio 1.30, 95% confidence interval [CI] 0.28 to 5.95; I²=0%; low-certainty evidence) and postoperative atrial fibrillation (relative risk 0.75, 95% CI 0.38 to 1.46; I²=50%; very low-certainty evidence). However, prehabilitation may improve postoperative functional capacity and slightly shorten the hospital stay (mean difference -0.66 days, 95% CI -1.29 to -0.03; I²=45%; low-certainty evidence).

CONCLUSION

Despite the high heterogeneity among physical prehabilitation trials and the uncertainty regarding robust clinical outcomes, physical prehabilitation before cardiac surgery seems to enhance selected postoperative functional performance measures and slightly reduce the hospital length of stay after cardiac surgery.

Pocket-Size Mobile Echocardiographic Screening of Thoracic Aortic Aneurysms in Hypertensive Patients

BACKGROUND

Patients with hypertension may develop a thoracic aortic aneurysm (TAA) that can be asymptomatic but potentially life-threatening. We sought to assess the prevalence of asymptomatic TAA among hypertensive patients with a point-of-care screening program using pocket-size mobile echocardiographic (PME) devices.

METHODS

We prospectively performed transthoracic aortic ultrasound using a PME device on patients attending our hypertension clinics between June 2016 and July 2018. The echo examinations were performed by a research fellow to obtain aortic diameter measurements including the aortic sinus, sinotubular junction, ascending aorta, aortic arch, and descending thoracic aorta through various standard echo views. Images were stored on the PME and transferred to a desktop computer for measurements and further statistical analysis.

RESULTS

During the study period 1529 hypertensive patients (mean age, 62 years [range, 30-85]; 824 men) were recruited. The prevalence of TAA (defined as maximum aortic diameter ≥ 4.5 cm and/or >50% larger than the diameter of the adjacent normal aorta) in our study population was 7.5% (115/1529). Multiple logistic regression analysis identified male gender (odds ratio, 2.120; P < .001) and older age (odds ratio, 1.031; P < .001) as independent factors associated with TAA.

CONCLUSIONS

Silent TAA is common among hypertensive patients in Hong Kong. We found the PME device to be effective in detecting TAA in a clinic setting. Such an approach may be useful for early detection of TAA among at-risk patients, allowing aggressive blood pressure control and early surgical intervention to prevent catastrophic complications.

Effect of preoperative education and ICU tour on patient and family satisfaction and anxiety in the intensive care unit after elective cardiac surgery: a randomised controlled trial

BACKGROUND

Preoperative education may help participants to psychologically prepare themselves for surgery, but the outcomes of such preparation have rarely been assessed in patients requiring postoperative care in the intensive care unit (ICU) as well as in family members.

OBJECTIVE

To assess the effect of a preoperative multifaceted education intervention on patient and family satisfaction levels in the ICU and measures of perioperative patients' anxiety and depression.

TRIAL DESIGN

Single-centre, two-armed, parallel, superiority, randomised controlled trial. Healthcare professionals in ICU and outcome assessor were blinded to treatment allocation.

PARTICIPANTS

100 elective coronary artery bypass grafting±valve surgery patients and their family members.

INTERVENTIONS

Preoperative education comprising of a video and ICU tour in addition to standard care (treatment), versus standard care (control).

OUTCOMES

Patient and family satisfaction levels with ICU using validated PS-ICU23 and FS-ICU24 questionnaires (0-100), respectively; change in perioperative anxiety and depression scores between 1 day presurgery and 3 days postsurgery.

RESULTS

Among 100 (50 treatment, 50 control) patients and 98 (49 treatment, 49 control) family members, 94 (48 treatment, 46 control) patients and 94 (47 treatment, 47 control) family members completed the trial. Preoperative education was associated with higher overall patient (mean difference (MD) 6.7, 95% CI 0.2 to 13.2) and family (MD 10.0, 95% CI 3.8 to 16.3) satisfaction scores. There was a weak association between preoperative education and a reduction in patient's anxiety scores over time (MD -1.7, 95% CI -3.5 to 0.0). However, there was no evidence of a treatment effect on patient's depression scores over time (MD -0.6, 95% CI -2.3 to 1.2).

CONCLUSION

Providing comprehensive preoperative information about ICU to elective cardiac surgical patients improved patient and family satisfaction levels and may decrease patients' anxiety levels.

TRIAL REGISTRATION NUMBER

ChiCTR-IOR-15006971.

PREhabilitation for improving QUality of recovery after ELective cardiac surgery (PREQUEL) study: protocol of a randomised controlled trial

INTRODUCTION

Frailty is a multidimensional syndrome in which multiple small physiological deficits accumulate gradually, resulting in a loss of physiological reserve and adaptability, putting a patient that is exposed to a stressor at a higher risk of adverse outcomes. Both pre-frailty and frailty are associated with poor patient outcomes and higher healthcare costs. The effect of a prehabilitation programme and standard care on the quality of recovery in pre-frail and frail patients undergoing elective cardiac surgery will be compared.

METHOD AND ANALYSIS

A single-centre, superiority, stratified randomised controlled trial with a blinded outcome assessment and intention-to-treat analysis. Pre-frail and frail patients awaiting elective coronary artery bypass graft, with or without valvular repair/replacement, will be recruited. 164 participants will be randomly assigned to either prehabilitation (intervention) or standard care (no intervention) groups. The prehabilitation group will attend two sessions/week of structured exercise (aerobic and resistance) training, supervised by a physiotherapist, for 6-10 weeks before surgery with early health promotion advice in addition to standard care. The standard care group will receive the usual routine care (no prehabilitation). Frailty will be assessed at baseline, hospital admission and at 1 and 3 months after surgery. The primary outcomes will be participants' perceived quality of recovery (15-item Quality of Recovery questionnaire) after surgery (day 3), days at home within 30 days of surgery and the changes in WHO Disability Assessment Schedule 2.0 score between baseline and at 1 and 3 months after surgery. Secondary outcomes will include major adverse cardiac and cerebrovascular events, psychological distress levels, health-related quality of life and healthcare costs.

ETHICS AND DISSEMINATION

The Joint CUHK-NTEC Clinical Research Ethics Committee approved the study protocol (CREC Ref. No. 2017.696 T). The findings will be presented at scientific meetings, in peer-reviewed journals and to study participants.

TRIAL REGISTRATION NUMBER

ChiCTR1800016098; Pre-results.

Effect of motor subtypes of delirium in the intensive care unit on fast-track failure after cardiac surgery

OBJECTIVE

The purpose of the study was to evaluate the association between motor subtypes of postoperative delirium in the intensive care unit and fast-track failure (a composite outcome of prolonged stay in the intensive care unit >48 hours, intensive care unit readmission, and 30-day mortality) after cardiac surgery.

METHODS

This was a secondary analysis of a prospective cohort study of 600 consecutive adults undergoing cardiac surgery at a university hospital in Hong Kong (July 2013 to July 2015). The motor subtypes of delirium were classified using the Richmond Agitation Sedation Score and Confusion Assessment Method intensive care unit assessments performed by trained bedside nurses. A generalized estimating equation was used to estimate a common relative risk of fast-track failure associated with motor subtypes.

RESULTS

The incidences of hypoactive, hyperactive, and mixed motor subtypes were 4.3% (n = 26), 4.0% (n = 24), and 5.5% (n = 33), respectively. Fast-track failure occurred in 88 patients (14.7%). There was an association between delirium (all subtypes) and fast-track failure (P = .048); hyperactive delirium (relative risk, 1.95; 95% confidence interval, 0.96-3.94); hypoactive delirium (relative risk, 2.79; 95% confidence interval, 1.34-5.84); and mixed delirium (relative risk, 2.55; 95% confidence interval, 1.11-5.88). Hypoactive and mixed subtypes were associated with prolonged intensive care unit stay (both P = .001).

CONCLUSIONS

Patients with pure hypoactive delirium had a similar risk of developing fast-track failure as other motor subtypes. Differentiation of motor subtypes is unlikely to be clinically important for prognostication of fast-track failure. However, because delirium is associated with poor outcomes, potential treatment strategies should address all subtypes equally.

Activation of PERK branch of ER stress mediates homocysteine-induced BKCa channel dysfunction in coronary artery via FoxO3a-dependent regulation of atrogin-1

The molecular mechanism of endoplasmic reticulum (ER) stress in vascular pathophysiology remains inadequately understood. We studied the role of ER stress in homocysteine-induced impairment of coronary dilator function, with uncovering the molecular basis of the effect of ER stress on smooth muscle large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels. The vasodilatory function of BK_Ca channels was studied in a myograph using endothelium-denuded porcine small coronary arteries. Primary cultured porcine coronary artery smooth muscle cells were used for mRNA and protein measurements and current recording of BK_Ca channels. Homocysteine inhibited vasorelaxant response to the BK_Cachannel opener NS1619, lowered BK_Ca β1 subunit protein level and suppressed BK_Ca current. Inhibition of ER stress restored BK_Ca β1 protein level and NS1619-evoked vasorelaxation. Selective blockade of the PKR-like ER kinase (PERK) yielded similarly efficient restoration of BK_Ca β1, preserving BK_Ca current and BK_Ca-mediated vasorelaxation. The restoration of BK_Ca β1 by PERK inhibition was associated with reduced atrogin-1 expression and decreased nuclear localization of forkhead box O transcription factor 3a (FoxO3a). Silencing of atrogin-1 prevented homocysteine-induced BK_Ca β1 loss and silencing of FoxO3a prevented atrogin-1 upregulation induced by homocysteine, accompanied by preservation of BK_Ca β1 protein level and BK_Ca current. ER stress mediates homocysteine-induced BK_Ca channel inhibition in coronary arteries. Activation of FoxO3a by PERK branch underlies the ER stress-mediated BK_Ca inhibition through a mechanism involving ubiquitin ligase-enhanced degradation of the channel β1 subunit.

Risk prediction models for delirium in the intensive care unit after cardiac surgery: a systematic review and independent external validation

Numerous risk prediction models are available for predicting delirium after cardiac surgery, but few have been directly compared with one another or been validated in an independent data set. We conducted a systematic review to identify validated risk prediction models of delirium (using the Confusion Assessment Method-Intensive Care Unit tool) after cardiac surgery and assessed the transportability of the risk prediction models on a prospective cohort of 600 consecutive patients undergoing cardiac surgery at a university hospital in Hong Kong from July 2013 to July 2015. The discrimination (c-statistic), calibration (GiViTI calibration belt), and clinical usefulness (decision curve analysis) of the risk prediction models were examined in a stepwise manner. Three published high-quality intensive care unit delirium risk prediction models (n=5939) were identified: Katznelson, the original PRE-DELIRIC, and the international recalibrated PRE-DELIRIC model. Delirium occurred in 83 patients (13.8%, 95% CI: 11.2-16.9%). After updating the intercept and regression coefficients in the Katznelson model, there was fair discrimination (0.62, 95% CI: 0.58-0.66) and good calibration. As the original PRE-DELIRIC model was already validated externally and recalibrated in six countries, we performed a logistic calibration on the recalibrated model and found acceptable discrimination (0.75, 95% CI: 0.72-0.79) and good calibration. Decision curve analysis demonstrated that the recalibrated PRE-DELIRIC risk model was marginally more clinically useful than the Katznelson model. Current models predict delirium risk in the intensive care unit after cardiac surgery with only fair to moderate accuracy and are insufficient for routine clinical use.

Patient and family satisfaction levels in the intensive care unit after elective cardiac surgery: study protocol for a randomised controlled trial of a preoperative patient education intervention

INTRODUCTION

Patients and their families are understandably anxious about the risk of complications and unfamiliar experiences following cardiac surgery. Providing information about postoperative care in the intensive care unit (ICU) to patients and families may lead to lower anxiety levels, and increased satisfaction with healthcare. The objectives of this study are to evaluate the effectiveness of preoperative patient education provided for patients undergoing elective cardiac surgery.

METHODS AND ANALYSIS

100 patients undergoing elective coronary artery bypass graft, with or without valve replacement surgery, will be recruited into a 2-group, parallel, superiority, double-blinded randomised controlled trial. Participants will be randomised to either preoperative patient education comprising of a video and ICU tour with standard care (intervention) or standard education (control). The primary outcome measures are the satisfaction levels of patients and family members with ICU care and decision-making in the ICU. The secondary outcome measures are patient anxiety and depression levels before and after surgery.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the Joint Chinese University of Hong Kong-New Territories East Cluster Clinical Research Ethics Committee (reference number CREC 2015.308). The findings will be presented at conferences and published in peer-reviewed journals. Study participants will receive a 1-page plain language summary of results.

TRIAL REGISTRATION NUMBER

ChiCTR-IOR-15006971.

Cellular and molecular mechanisms of endothelial ischemia/reperfusion injury: perspectives and implications for postischemic myocardial protection

Ischemia/reperfusion (I/R) injury is a major cause of myocardial damage. Despite continuous efforts, minimizing I/R injury still represents a great challenge in standard medical treatments of ischemic heart disease, i.e., thrombolytic therapy, primary percutaneous coronary intervention, and coronary arterial bypass grafting. Development of effective interventions and strategies to prevent or reduce myocardial I/R injury is therefore of great clinical significance. Endothelial dysfunction plays a significant role in myocardial I/R injury, which renders endothelial cells an attractive target for postischemic myocardial protection. The rapidly evolving knowledge of the mechanisms of endothelial I/R injury helps broaden perspective for future development of novel strategies targeting endothelium for alleviating myocardial I/R damage. This review provides a comprehensive summary of the cellular and molecular mechanisms of endothelial I/R injury. Current perspectives and future directions for developing endothelium targeting therapeutics for postischemic myocardial protection are further discussed.

A randomized controlled trial of 2 protocols for weaning cardiac surgical patients receiving adaptive support ventilation

PURPOSE

This study aims to compare the effectiveness of weaning with adaptive support ventilation (ASV) incorporating progressively reduced or constant target minute ventilation in the protocol in postoperative care after cardiac surgery.

MATERIAL AND METHODS

A randomized controlled unblinded study of 52 patients after elective coronary artery bypass surgery was carried out to determine whether a protocol incorporating a decremental target minute ventilation (DTMV) results in more rapid weaning of patients ventilated in ASV mode compared to a protocol incorporating a constant target minute ventilation.

RESULTS

Median duration of mechanical ventilation (145 vs 309 minutes; P = .001) and intubation (225 vs 423 minutes; P = .005) were significantly shorter in the DTMV group. There was no difference in adverse effects (42% vs 46%) or mortality (0% vs 0%) between the 2 groups.

CONCLUSIONS

Use of a DTMV protocol for postoperative ventilation of cardiac surgical patients in ASV mode results in a shorter duration of ventilation and intubation without evidence of increased risk of adverse effects.

NO and EDHF pathways in pulmonary arteries and veins are impaired in COPD patients

We investigated endothelial function of both pulmonary arteries and veins in patients with chronic obstructive pulmonary disease (COPD) of varying severity in regard to the role of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF). Lung tissues were obtained from patients undergoing lobectomy or pneumonectomy. Patients were grouped to control, moderate COPD, and severe COPD according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines. Pulmonary arteries and veins were studied for endothelium-dependent relaxations. NO concentration was measured by electrochemical method. Protein expressions of eNOS and phosphorylated eNOS were determined by Western-blot. Endothelium-dependent relaxation was more significant in pulmonary arteries than in veins. The vasorelaxation was decreased in patients of moderate COPD and further decreased in severe COPD. The severity of endothelial dysfunction in both pulmonary arteries and veins correlated with the degree of airflow obstruction. COPD patients exhibited reduced endothelial NO production, decreased eNOS protein expression and decreased eNOS phosphorylation. The EDHF component was abolished in the pulmonary vasculature of patients with severe COPD. NO and EDHF pathways are both involved in the regulation of vascular tone in human pulmonary arteries and veins. Both pathways are impaired in COPD patients and the severity of the impairment increases with the progress of the disease. Downregulation of eNOS expression and inhibition of eNOS activation underlie the reduction of NO in COPD patients.

AVE3085, an enhancer of endothelial nitric oxide synthase, restores endothelial function and reduces blood pressure in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Nitric oxide (NO) plays an important role in endothelial function, and impaired NO production is involved in hypertension. Therefore, compounds that regulate endothelial NO synthase (eNOS) may be of therapeutic benefit. A novel, low molecular weight compound AVE3085 is a recently developed compound with the ability to enhance eNOS transcription. The present study investigated the effects of AVE3085 in endothelial dysfunction associated with hypertension.

EXPERIMENTAL APPROACH

Spontaneously hypertensive rats (SHRs) were treated with AVE 3085 (10 mg·kg·day(-1) , orally) for 4 weeks. Isometric force measurement was performed on rings of isolated aortae in organ baths. Protein expression of eNOS, phosphorylated-eNOS and nitrotyrosine in the aortae were examined by Western blotting. mRNA for eNOS in rat aortae were examined by reverse-transcriptase polymerase chain reaction (RT-PCR).

KEY RESULTS

AVE3085 greatly improved endothelium-dependent relaxations in the aortae of SHRs. This functional change was accompanied by up-regulated expression of eNOS protein and mRNA, enhanced eNOS phosphorylation and decreased formation of nitrotyrosine. Furthermore, AVE3085 treatment reduced the blood pressure in SHR without affecting that of hypertensive eNOS(-/-) mice.

CONCLUSIONS AND IMPLICATIONS

The eNOS-transcription enhancer AVE3085 restored impaired endothelial function in a hypertensive model. The present study provides a solid basis for the potential development of eNOS-targeting drugs to restore down-regulated eNOS, as a new strategy in hypertension.

4-Methylnitrosamino-1-3-pyridyl-1-butanone (NNK) promotes lung cancer cell survival by stimulating thromboxane A2 and its receptor

The role of thromboxane A(2) (TxA(2)) in smoking-associated lung cancer is poorly understood. This study was conducted to study the role of TxA(2) in smoking carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-promoted cell survival and growth in human lung cancer cells. We found that NNK increased TxA(2) synthase (TxAS) expression and thromboxane B(2) (TxB(2)) generation in cultured lung cancer cells, the result of which was supported by the increased level of TxAS in lung cancer tissues of smokers. Both TxAS-specific inhibitor furegrelate and TxA(2) receptor antagonist SQ29548 completely blocked NNK-mediated cell survival and growth via inducting apoptosis. TxA(2) receptor agonist U46619 reconstituted a near-full survival and growth response to NNK when TxAS was inhibited, affirming the role of TxA(2) receptor in NNK-mediated cell survival and growth. Suppression of cyclic adenosine monophosphate response element binding protein (CREB) activity by its small interference RNA blocked the effect of NNK. Phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) also had a positive role. Altogether, our results have revealed that NNK stimulates TxA(2) synthesis and activates its receptor in lung cancer cells. The increased TxA(2) may then activate CREB through PI3K/Akt and extracellular ERK pathways, thereby contributing to the NNK-promoted survival and growth of lung cancer cells.

Peri-operative blood transfusion increases length of hospital stay and number of postoperative complications in non-cardiac surgical patients

OBJECTIVES

To test the hypothesis that blood transfusion alone was a significant risk factor for in-hospital morbidity in non-cardiac patients.

DESIGN

Propensity analysis.

SETTING

University teaching hospital, Hong Kong.

PATIENTS

Consecutive non-cardiac patients seen in our department from 2006 to early 2009 who underwent a major procedure under general or spinal anaesthesia were included. Propensity analysis was performed to neutralise the confounding effects of preoperative variables and identify the true effects of transfusions on surgical outcomes.

MAIN OUTCOME MEASURES

Receipt of intra-operative and postoperative blood transfusion was established and the difference in proportions between patients who did and did not receive donor blood tested for mortality, overall morbidity, individual complications, and number of adverse events.

RESULTS

Transfused patients were significantly older and sicker, more likely to be male, to have lower haemoglobin values and undergo longer and more emergency surgical procedures than those not receiving a transfusion. Blood transfusion was predictive of length of postoperative hospital stay and number of complications before discharge. The amount of transfused blood was predictive of in-hospital mortality, with an odds ratio of 1.4 for each unit of blood received. The risk of a surgical wound infection was almost doubled when the patient had received a blood transfusion.

CONCLUSION

After controlling for the factors associated with an increased likelihood for receiving a blood transfusion, the actual transfusion was predictive of a slower and more eventful postoperative recovery with associated costs to both the patient and health services.

Effect of fetal anaemia on myocardial ischaemia-reperfusion injury and coronary vasoreactivity in adult sheep

AIMS

We investigated whether chronic fetal anaemia affects myocardial infarct in adulthood and elicits functional modifications in adult coronary vasoreactivity.

METHODS

Seven-month-old sheep that were made anaemic in utero and transfused to normal haematocrit before birth were studied. Infarct size was determined by tetrazolium after 1-h ischaemia (occlusion of the mid of left anterior descending artery) and 2-h reperfusion. The dose-response to vasoconstrictors and vasodilators was assessed in small resistance coronary arteries.

RESULTS

There were no significant differences between the animals previously subjected to in utero anaemia and the control animals regarding the percentage infarct size and the area-at-risk to the left ventricle. The ventricular function (dP/dt) was preserved. The percentage infarct size of the area-at-risk (70.7 +/- 3.5%) was larger than that in the controls (49.8 +/- 4.5%) (P = 0.006). The vascular responses were not altered. Endothelium-dependent relaxation to bradykinin (96.0 +/- 2.6% vs. 98.8 +/- 1.0%) was not affected by PGI(2) inhibitor (94.6 +/- 2.6% vs. 98.5 +/- 1.0%) but significantly reduced by the inhibition of nitric oxide (NO) in both anaemic (P < 0.05) and control (P < 0.001) groups with a significant right shift of EC(50) (P < 0.01). The non-NO-non-PGI(2)-mediated relaxation was slightly potentiated in anaemic animals.

CONCLUSIONS

Exposing fetal sheep to in utero anaemia in late gestation for 3 weeks may increase the susceptibility of adult hearts to ischaemia-reperfusion injury without major alterations in coronary vasomotor responsiveness. The impact of in utero anaemia at earlier period of pregnancy and on the earlier or later life of the adult is yet to be further investigated.

Haem oxygenase-1 plays a central role in NNK-mediated lung carcinogenesis

The tobacco-specific nitrosamine, 4-(N-methyl-N-nitrosoamino)-1-(3-pyridyl)-1-butanone (NNK), is a potent lung cancer inducer. However, how NNK induces lung cancer is still largely unknown. Haem oxygenase (HO)-1 was evaluated in 30 pairs of lung cancer tumour samples and matched nontumour tissues from patients with a history of cigarette smoking. Expression of HO-1, p21(Cip1/Waf1/Cid1) (p21), B-cell lymphoma (Bcl)-2 family members, mitogen-activated protein kinase and nuclear factor (NF)-kappaB was also studied in lung cancer cells treated with NNK. The levels of HO-1 and p21 were significantly increased in lung tumour tissues. There was a positive relationship between these two proteins in the tumour. NNK stimulated lung cell proliferation and elevated the levels of HO-1, p21, inhibitor of apoptosis protein (c-IAP)2 and Bcl-2, but downregulated Bad. These effects of NNK were blocked by zinc protoporphyrin-XII, an HO-1 inhibitor. The NNK-mediated expression of HO-1 was governed by NF-kappaB and extracellular signal-regulated kinase 1/2, since blocking either of these prevented the stimulatory effect of NNK on HO-1, as well as molecules downstream of HO-1, such as p21, c-IAP2, Bcl-2 and Bad. In conclusion, haem oxygenase-1 plays a central role in NNK-mediated cell proliferation by promoting the expression of p21(Cip1/Waf1/Cid1), inhibitor of apoptosis protein 2 and B-cell lymphoma-2 but inhibiting the activity of Bad. Nuclear factor-kappaB and extracellular signal-regulated kinase 1/2 function upstream of haem oxygenase-1. Therefore, haem oxygenase-1 is likely to be a potential target in the treatment of smoking-related lung cancer.

Repair of aortic valve prolapse: experience with 44 patients*1

OBJECTIVES

In regurgitant tricuspid aortic valves, cusp prolapse may be isolated or associated with dilatation of the proximal aorta. Newly appearing cusp prolapse can also appear after an aortic valve sparing operation (AVSO) and be responsible for residual aortic regurgitation. In this report, we describe our experience in repairing prolapsing aortic cusps in 44 patients with aortic regurgitation.

METHODS

Between 1996 and 2003, 260 patients had aortic valve repair or valve sparing procedures in our department. All patients had peri-operative TEE. Prolapse of one or more of the aortic cusps was identified by TEE and confirmed by careful surgical inspection before and after valve sparing surgery. Forty-four patients with cusp prolapse were identified. Fifteen had an isolated prolapse, with a normal root (group I), 18 had cusp prolapse associated with dilatation of the proximal aorta (group IIa), and 11 had a newly appearing prolapse after AVSO (group IIb). Correction of the prolapsing cusp was achieved by either free edge plication, triangular resection or resuspension with PTFE. This procedure was associated with an aortic annuloplasty in group I, and with AVSO in groups II and III.

RESULTS

Post-operative TEE showed AR trivial or grade I regurgitation. At a mean of 23 months follow-up, one patient with recurrent regurgitation required an aortic valve replacement with a homograft. All remaining patients were in NYHA class I or II. Echocardiography confirmed the durability of the valve repair.

CONCLUSIONS

Among the common causes of aortic regurgitation, isolated cusp prolapse is frequent and is amenable to surgical repair with excellent mid-term results. In particular, in patents who are potential candidates for AVSO, identification and correction of an associated prolapse, either pre-existing or secondary to the AVSO procedure, may further extend the indications for this technique, increase its success rates and improve its long-term outcome.

Clinical and angiographic outcome of different surgical strategies of bilateral internal mammary artery grafting

Long-term survival, relief of angina, and prevention of myocardial infarction after coronary revascularization are related to the preoperative status of the patient, progression of coronary artery atherosclerosis, and the patency of the conduits used. The increased use of the internal mammary artery for coronary grafting depends upon the accumulation of data on superior late patency compared with venous conduits. These data have supported the simultaneous use of both left and right internal mammary arteries with reported improved late survival. However, controversy still surrounds the clinical and angiographic outcomes of some of the surgical strategies of bilateral internal mammary artery grafting. This review examines a range of surgical strategies of bilateral internal mammary artery grafting and their mid- and long-term clinical and angiographic outcomes. From the available data, careful preoperative selection of patients is paramount. Clinical and angiographic outcome of bilateral internal mammary grafting is superior to single internal mammary grafting with supplemental vein grafts when pedicled, sequential, or free aorto-coronary internal mammary artery is used. Further studies are needed to evaluate the midterm and long-term clinical and angiographic outcomes of complex strategies such as Y or T procedures.

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

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.

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.

Reconstruction of the ascending aorta and aortic root: experience in 45 consecutive patients

BACKGROUND

Patients with aneurysms of the ascending aorta or aortic root may have associated aortic insufficiency (AI). We reviewed our experience with aortic root remodeling and reconstruction of the sino-tubular junction.

METHODS

Forty-five patients were operated on between July 1995 and September 1998. Transesophageal echocardiography showed AI grade III or IV in 15 patients. Twenty-seven patients had replacement of all three sinuses, 10 of one or two sinuses. Reconstruction of the sino-tubular junction alone was performed in 8 patients.

RESULTS

There was one death at 28 days. Perioperative transesophageal echocardiography showed no or discrete AI in all patients. There has been one aortic valve replacement at day 4 postoperatively for cusp repair failure. Transesophageal echocardiography in 40 patients at a mean time of 12.5 months showed no progression of AI in 38 patients, and a grade II in 2. Clinical follow-up averaged 14.5 months. There have been three late, not procedure-related deaths. Thirty-six patients are in New York Heart Association functional class I. There have been no cases of endocarditis.

CONCLUSIONS

Aortic remodeling is successful in eliminating AI in patients with aortic root disease with minimal mortality and morbidity. Early echocardiography (1 year) has shown no progression of AI in 95% of cases.

Predictors of atrial fibrillation after conventional and beating heart coronary surgery: A prospective, randomized study

BACKGROUND

Atrial fibrillation (AF) increases the morbidity of CABG. The pathophysiology is uncertain, and its prevention remains suboptimal. This prospective, randomized study was designed to define the role of cardiopulmonary bypass (CPB) and cardioplegic arrest in the pathogenesis of this complication.

METHODS AND RESULTS

Two hundred patients were prospectively randomized to (1) on-pump conventional surgery [(100 patients, 79 men, mean age 63 (40 to 77) years)] with normothermic CPB and cardioplegic arrest of the heart or (2) off-pump surgery [(100 patients, 82 men, mean age 63 (38 to 86) years)] on the beating heart. Heart rate and rhythm were continuously monitored with an automated arrhythmia detector during the first 72 hours after surgery. Thereafter, routine clinical observation was performed and continuous monitoring restarted in the case of arrhythmia. The association of perioperative factors with AF was investigated by univariate analysis. Significant variables were then included into a stepwise logistic regression model to ascertain their independent influence on the occurrence of AF. There were no significant baseline differences between groups. Thirty-nine patients in the on-pump group and 8 patients in the off-pump group had postoperative sustained AF (P:=0.001). Univariate analysis showed that CPB inclusive of cardioplegic arrest, postoperative inotropic support, intubation time, chest infection, and hospital length of stay were predictors of AF (all P:<0.05). However, stepwise multivariate regression analysis identified CPB inclusive of cardioplegic arrest as the only independent predictor of postoperative AF (OR 7.4; CI 3.4 to 17.9).

CONCLUSIONS

CPB inclusive of cardioplegic arrest is the main independent predictor of postoperative AF in patients undergoing coronary revascularization.

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.

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

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.

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

On-pump versus off-pump coronary revascularization: evaluation of renal function

BACKGROUND

Coronary revascularization with cardiopulmonary bypass has the potential risk of renal dysfunction related to the nonphysiologic nature of cardiopulmonary bypass. Recently, there has been a revival of interest in performing myocardial revascularization on the beating heart and we investigated whether this prevents renal compromise.

METHODS

A prospective, randomized, controlled trial was performed in 50 patients (45 males, mean age 61+/-3.7 years) undergoing elective coronary artery bypass grafting. Patients were randomly assigned to conventional revascularization with cardiopulmonary bypass (on pump) or beating heart revascularization (off pump). Glomerular and tubular function were assessed up to 48 hours postoperatively.

RESULTS

There were no deaths, myocardial infarctions or acute renal failure in either group. Glomerular filtration as assessed by creatinine clearance and the urinary microalbumin/creatinine ratio was significantly worse in the on pump group (p < 0.0004 and 0.0083, respectively). Renal tubular function was also impaired in the on pump group as assessed by increased N-acetyl glucosaminidase activity (p < 0.0272).

CONCLUSIONS

These results suggest that off pump coronary revascularization offers a superior renal protection when compared with conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest in first time coronary bypass patients.

Recycling of arterial grafts during reoperative coronary artery operations

BACKGROUND

To overcome problems of lack of conduit and to maximize the number of arterial anastomoses in coronary reoperations we reused previously placed arterial grafts.

METHODS

Sixteen patients were identified from February 1994 to July 1997. Mean age was 62.8 years (range, 44 to 75 years). Fifteen (94%) were in Canadian Cardiovascular Society angina class III or IV. The mean interval from primary to secondary operation was 8.5 years (range, 3 to 12 years). Eleven patients had a patent internal mammary artery graft used as the recipient for a proximal Y anastomosis. In 3 cases an arterial graft was reimplanted distally on the same coronary vessel and in 2 onto different coronary vessels. One patient had a combination of these techniques. Five patients required venous conduit.

RESULTS

There were no deaths. Mean length of intensive care stay was 69 hours (range, 24 to 144) and mean hospital stay was 14 days (range, 10 to 28 days). All patients were discharged home. Follow-up averages 13 months (range, 2 to 43 months). Twelve patients (75%) are now in Canadian Cardiovascular Society angina class I and 3 (19%) in class II.

CONCLUSIONS

Reusing arterial conduits during coronary reoperations is possible with minimal in-hospital morbidity and satisfactory results in terms of freedom from angina. Using these techniques can help overcome the problems of inadequate conduit and maximize the number of arterial anastomoses that can be made per patient.

Biomaterials and cardiovascular devices

In the field of cardiovascular surgery there is presently a lack of biomaterials possessing essential characteristics of the native tissue or organ which is to be replaced. This paper describes various biomaterials that have been introduced into the circulatory system and the complex reactions that subsequently occur. The risk of infection is also discussed as well as prevention and treatment regimes that can be used. Examples of future biomaterial development are outlined in an attempt to achieve biocompatibility.

Use of the right gastroepiploic artery as a coronary artery bypass graft in 307 patients

From October 1988 to October 1995 the right gastroepiploic artery was used as a conduit for coronary surgery in 307 patients. Their average age was 56.5 years (range 25-75) and 274 patients (89%) were male. Twenty-six cases (8.5%) were re-operations and 58 patients (19%) were operated upon on an urgent or semi-urgent basis. Target coronary vessels were the right coronary artery and its branches in 280 cases (91.4%), the circumflex artery in 25 cases (8%) and the left anterior descending artery in two cases. The right gastroepiploic artery was used as an in situ graft in 303 cases (98.7%) and as a free graft in 4 (1.3%). A total of 291 patients (94.8%) also received at least one mammary artery graft: both mammary arteries were used in 167 patients (54.4%). An average of 3.6 distal anastomoses were made per patient, three of them with arterial grafts. Eleven (3.2%) right gastroepiploic artery grafts were doubled with saphenous vein intraoperatively because of persistent myocardial ischemia. In-hospital mortality was 1.6% (five patients). Perioperative myocardial infarction occurred in twelve patients (3.9%). Follow-up now averages 26 months (range 6-88). There have been five late deaths (1.6%). A total of 265 (89.2%) patients are angina free. Of the total, 145 patients have been investigated with a maximal-stress test coupled with scintigraphy: residual myocardial ischemia was found in 10 patients, right gastroepiploic artery was related in three. Ninety-six patients have undergone angiographic restudy at a mean of 12 months (range 8-88) postoperatively. Patency of the right gastroepiploic artery grafts was 91.8%. This study confirms that the right gastroepiploic artery can be used as a conduit for coronary artery bypass surgery with minimal mortality or morbidity. Mid-term patency rates and clinical outcome are encouraging.

The lima success story--whither other arterial grafts--are vein grafts obsolete?

The long-term benefit of myocardial revascularisation depends largely upon the continued patency of bypass grafts, but the long-term patency of vein grafts is poor. To improve the results of myocardial revascularisation, either measures to increase the patency of saphenous vein grafts or alternative conduits are required. Use of the left internal mammary artery as a graft is known to increase survival, and this has prompted wider use of other arterial grafts in the expectation that they will further enhance the long-term results of coronary artery bypass. This policy is based upon sound theory, but convincing evidence that it improves survival is lacking. Meanwhile, advances in the understanding of the pathology of vein graft occlusion have given rise to new methods of increasing vein graft patency. While these techniques are, as yet, only experimental, if translated into clinical practice, the places of arterial and venous grafts may require further assessment.

Arterial and venous conduits for coronary artery bypass. A current review

Poor long-term patency of saphenous vein grafts limits the long-term success of the coronary artery bypass operation. If this is to be improved, either measures that increase the patency of saphenous vein grafts or alternative conduits are required. The benefits of using the left internal mammary artery as a pedicled graft to the left anterior descending coronary artery have prompted increasing use of arterial grafts to further improve outcome. Concurrently advances in the understanding of the pathological processes underlying saphenous vein graft occlusion raise the possibility of improving vein graft patency. In this paper we review the problem of vein graft occlusion and possible solutions, the theoretical benefits of arterial grafts and the clinical results associated with their use.

The cerebral function monitor (CFM) is a useful addition to a bilateral carotid artery, vein graft model

Following human coronary artery bypass surgery, vein graft occlusion is a major cause of morbidity and mortality. An agent is required which will reduce the incidence of early graft thrombosis without causing systemic bleeding. To assess the efficacy of such agents a suitable experimental vein-graft model is required. A porcine, unilateral saphenous vein-carotid artery bypass graft model has been described previously, although to assess the effect of locally applied anticoagulant drugs, insertion of grafts bilaterally would be advantageous, allowing treated and control grafts to be implanted in the same animal which would then act as its own control. Pigs are reported as having an excellent collateral cerebral circulation and hence in theory, would be suitable animals to use as a bilateral carotid vein-graft model. This paper describes the occurrence of serious neurological complications during the development of such a model and suggests that by using a cerebral function monitor, detection of critical reductions in cerebral perfusion can be made early and remedial action take.

Changes in "inflammatory" mediators and total body water during extra-corporeal membrane oxygenation (ECMO). A preliminary study

We studied six patients (5 paediatric, 1 neonate) treated with ECMO to quantify changes in inflammatory mediators (neutrophil elastase (NE), free radical activity (FR), interleukin 8 (IL8)) and total body water (TBW). Blood samples were taken before instigation of ECMO, 4, 12, 24 hours post-ECMO and daily for six days. FR activity was quantified using the oxidised IgG FI/UV ration. NE and IL8 levels were measured by ELISA. TBW was assessed by electrical bioimpedance. Statistical analysis was made using repeated measures analysis of variance and modified t-test where appropriate. Results are presented as mean +/- standard error of the mean. FR activity increased 4 hours after instigation of ECMO (IgG FI/UV 32.1 +/- 3.2 from 24.1 +/- 3.0 p = 0.005) and remained elevated. NE also increased by 4 hours (94.8 micrograms/L +/- 8.9 to 678 micrograms/L +/- 153.4, p = 0.005) but returned to pre-ECMO values by day 6. IL8 levels rose after ECMO (from 98 pg/ml +/- 39, to 24 pg/ml +/- 117.4) although no statistical difference was noted over time due to the large variation between subjects (p = 0.009). TBW (% pre-ECMO body weight) fell by 24 hours (from 118.6 +/- 12.6 to 96.5 +/- 8.2 p = 0.0004). This study demonstrated that ECMO stimulates an 'inflammatory' response to extracorporeal perfusion (increased FR, NE) but despite this, results in a reduction in total body water. The complex relationship between the inflammatory response to prolonged extracorporeal perfusion and its effect on tissue oedema merits further investigation.

Quality of life following infragenicular bypass and lower limb amputation

AIMS

To objectively assess the quality of life after femorodistal bypass and compare this to quality of life achieved following primary limb amputation.

DESIGN

Retrospective review.

SETTING

Leicester Royal Infirmary, U.K., 1988-1993.

METHODS

A self-assessment postal questionnaire containing scales measuring emotional disorder, social functioning and mobility was sent to 112 patients who had previously undergone femorodistal bypass (n = 86) or primary limb amputation (n = 26).

RESULTS

Further analysis demonstrated that a secondary procedure (PTA or graft revision) to maintain graft patency did not adversely affect quality of life. Additionally, patients undergoing secondary amputation after graft failure had an identical quality of life to those undergoing primary amputation.

CONCLUSIONS

These data illustrate that the quality of life after successful femorodistal bypass is higher than after primary or secondary amputation. To attain the maximum quality of life in patients with critical ischaemia, femorodistal bypass should be performed wherever feasible.

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

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.

Changes in vessel wall plasminogen activator activity and smooth muscle cell proliferation and activation after arterial injury

OBJECTIVES

The aim was to examine changes in vessel wall fibrinolytic activity following angioplasty and to assess any relationship to changes in smooth muscle cell proliferation and activation.

METHODS

Balloon angioplasty was performed to the iliac arteries of New Zealand White rabbits and vessel wall changes assessed at 2 h, 1 d, 7 d, 14 d, and 1 month postprocedure. Tissue-type (tPA) and urokinase-type (uPA) plasminogen activator activity was assessed using chromogenic substrate assays, while smooth muscle cell proliferation and activation was monitored using expression of proliferating cell nuclear antigen (PCNA) and of basic fibroblast growth factor (bFGF) respectively.

RESULTS

Intimal thickening progressively increased up to 1 month. uPA activity increased at 2 h [1.94(SEM 0.19) v 1.59(0.05) U.mg-1 tissue for control vessels, P = 0.03], remained increased at 24 h, but by 7 d had decreased to below control levels and remained low. In contrast, tPA activity fell significantly at 2 h [0.9(0.3) v 1.96(0.13) micrograms.mg-1 tissue for control vessels, P = 0.03], remained low at 24 h, but by 7 d had reverted back to control levels [2.19(0.39) micrograms.mg-1]. PCNA positivity of the media increased at day 1, reached maximum on day 7 [16.9(5.1)% positively staining cells] before returning to baseline by 1 month. PCNA positivity of the intima first evident at day 7 [0.7(0.3)%], reached a maximum at day 14 [4.1(0.4)%]. bFGF expression increased early at 2 h [mean(SE) positively staining cells: 15.7(5.3)% v 11.2(4.8)% for control vessels] and continued to increase, reaching a maximum in the media at day 7 [59(8.6)%] and in the intima at day 14 [57.5(5.7)%].

CONCLUSIONS

Balloon injury produced an initial fall in tPA and rise in uPA activity. tPA increased back to control levels by 7 d, while uPA fell to below control levels at 7 d and 1 month. This would be compatible with a mechanism whereby acute injury suppressed tPA and upregulated uPA activity, with increased tPA activity acting as a marker for vessel repair.

Assessment of myointimal cellular kinetics in a model of angioplasty by means of proliferating cell nuclear antigen expression

A detailed temporal assessment of cellular proliferation was carried out by means of immunostaining for proliferating cell nuclear antigen in a normolipemic rabbit model of balloon angioplasty to the iliac arteries. Assessment was made at 30 minutes, 2 hours, 1 day, 3 days, 7 days, 14 days, 1 month and 3 months after the procedure. Intimal hyperplasia was first noted at day 3; a prominent layer was formed by day 14. Cellular proliferation in the vessel media was observed as early as day 1 (percentage of positive-staining cells 0.5% +/- 0.2%), reaching a maximum by day 7 (16.9% +/- 5.1%) before returning to baseline levels by 1 month (0.2% +/- 0.02%); in the intima, cellular proliferation was first noted at day 7 (0.7% +/- 0.3%) and reached a maximum at day 14 (4.1% +/- 0.4%) before returning to baseline levels at 1 month (0.3% +/- 0.1%). Use of proliferating cell nuclear antigen expression in this model of angioplasty provided a simple and reproducible method of assessing cellular proliferation after vascular injury and may prove useful for monitoring the effects, in experimental models, of agents for reducing myointimal hyperplasia.