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Biomedical subjects

P Magee

Publications and source records attributed to P Magee.

At least 19 recordsLinked to original sources
PubMed2001

Cannabinoid receptor agonist WIN 55,212-2 inhibits rat cortical dialysate gamma-aminobutyric acid levels.

The effects of the cannabinoid receptor agonist WIN 55,212-2 (0.1-5 mg/kg i.p.) on endogenous extracellular gamma-aminobutyric acid (GABA) levels in the cerebral cortex of the awake rat was investigated by using microdialysis. WIN 55,212-2 (1 and 5 mg/kg i.p.) was associated with a concentration-dependent decrease in dialysate GABA levels (-16% +/- 4% and -26% +/- 4% of basal values, respectively). The WIN 55,212-2 (5 mg/kg i.p.) induced-inhibition was counteracted by a dose (0.1 mg/kg i.p.) of the CB(1) receptor antagonist SR141716A, which by itself was without effect on cortical GABA levels. These findings suggest that cannabinoids decrease cortical GABA levels in vivo, an action that might underlie some of the cognitive and behavioral effects of acute exposure to marijuana.

Animals↗
PubMed2001

Underuse of coronary revascularization procedures in patients considered appropriate candidates for revascularization.

BACKGROUND: Ratings by an expert panel of the appropriateness of treatments may offer better guidance for clinical practice than the variable decisions of individual clinicians, yet there have been no prospective studies of clinical outcomes. We compared the clinical outcomes of patients treated medically after angiography with those of patients who underwent revascularization, within groups defined by ratings of the degree of appropriateness of revascularization in varying clinical circumstances. METHODS: This was a prospective study of consecutive patients undergoing coronary angiography at three London hospitals. Before patients were recruited, a nine-member expert panel rated the appropriateness of percutaneous transluminal coronary angioplasty (PTCA) and coronary-artery bypass grafting (CABG) on a nine-point scale (with 1 denoting highly inappropriate and 9 denoting highly appropriate) for specific clinical indications. These ratings were then applied to a population of patients with coronary artery disease. However, the patients were treated without regard to the ratings. A total of 2552 patients were followed for a median of 30 months after angiography. RESULTS: Of 908 patients with indications for which PTCA was rated appropriate (score, 7 to 9), 34 percent were treated medically; these patients were more likely to have angina at follow-up than those who underwent PTCA (odds ratio, 1.97; 95 percent confidence interval, 1.29 to 3.00). Of 1353 patients with indications for which CABG was considered appropriate, 26 percent were treated medically; they were more likely than those who underwent CABG to die or have a nonfatal myocardial infarction--the composite primary outcome (hazard ratio, 4.08; 95 percent confidence interval, 2.82 to 5.93)--and to have angina (odds ratio, 3.03; 95 percent confidence interval, 2.08 to 4.42). Furthermore, there was a graded relation between rating and outcome over the entire scale of appropriateness (P for linear trend=0.002). CONCLUSIONS: On the basis of the ratings of the expert panel, we identified substantial underuse of coronary revascularization among patients who were considered appropriate candidates for these procedures. Underuse was associated with adverse clinical outcomes.

Angina Pectoris↗
PubMed2001

Screening for carotid artery disease before cardiac surgery: is current clinical practice evidence based?

BACKGROUND: There is no clear consensus as to the correct screening procedure to identify patients undergoing cardiac surgery and who are at greatest risk of stroke because of the presence of significant carotid artery stenosis. Such screening is important because some patients benefit from combined carotid and cardiac surgery and, regardless of this, the information gained puts the cardiac surgeon in a position to provide an accurate assessment of surgical risk. Our objective was to examine current clinical practice of carotid artery investigation prior to urgent cardiac surgery and to review this illustrative practice in the context of the world literature. HYPOTHESIS: The study aimed to establish that current typical practice for screening cardiac surgical patients for carotid artery disease is illogical according to the evidence in the world literature. METHODS: The study consisted of a retrospective assessment of all patients undergoing urgent cardiac surgery and a Medline-derived literature review, and included all patients undergoing urgent cardiac surgery at a tertiary cardiothoracic center between January 1 and December 31, 1997. RESULTS: Of 529 patients undergoing urgent cardiac surgery, 44 (8%) were screened preoperatively by duplex Doppler ultrasonography for carotid disease. The indications for screening were asymptomatic carotid bruit in 24 patients, history of stroke or transient ischemic attack (TIA) in 12 patients, and neither stroke, TIA, or bruit in 7 patients. The tests were requested either by the attending cardiologists or by the cardiac surgeon to whom they were referred. One patient had already been diagnosed as having carotid artery disease in the past. Thirteen patients underwent additional carotid investigations. Eleven patients were demonstrated to have internal carotid artery stenosis > or = 60% and 3 patients underwent combined cardiac and carotid surgery. Review of the literature revealed the following groups to be at increased risk of future stroke unrelated to surgery, and of postoperative stroke: those with a history of stroke or TIA, those with carotid bruits, and, of importance, all patients with significant carotid stenosis. Recent data suggest that symptomatic patients and the elderly are at greatest risk. CONCLUSIONS: Only 8% of patients undergoing urgent cardiac surgery in a 1-year period were screened for carotid artery disease. We suggest that screening should definitely be performed in all patients with a history of stroke or TIA, all patients with a bruit, and all patients aged > 65 years. The literature suggests, however, that significant reductions in stroke rate could be achieved by screening the whole cardiac surgical population, although there is a paucity of data that are specifically pertinent to this patient subgroup. Further data are therefore required for the construction of a scientifically valid and medicolegally sound policy.

Cardiac Surgical Procedures↗
PubMed1999

Rating the appropriateness of coronary angiography, coronary angioplasty and coronary artery bypass grafting: the ACRE study. Appropriateness of Coronary Revascularisation study.

BACKGROUND: Previous studies investigating the appropriateness of invasive management of coronary disease had not reported the internal consistency of their ratings and may now be out of date. The aim of this study was to measure the influence of clinical factors on contemporary ratings of the appropriateness of coronary angiography, percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft (CABG) in the Appropriateness of Coronary Revascularisation (ACRE) study. METHODS: The Delphi-RAND technique was used, in which an expert panel (four cardiologists, three cardiothoracic surgeons, a general physician and a general practitioner), meeting in 1995, rated mutually exclusive indications (n = 2178 for angiography, n = 995 for PTCA and n = 984 for CABG). The main outcome measures were the appropriateness category (inappropriate, uncertain or appropriate) for each of the three procedures and treatment preference. RESULTS: For revascularization, the strongest determinant of inappropriateness was coronary anatomy. The odds ratio (OR) for inappropriate PTCA was 10.6 (95 per cent confidence interval (CI) 4.8-23.5) for the effect of left main stem or three-vessel disease versus single-vessel disease, and for CABG it was 0.06 (95 per cent CI 0.03-0.15). The number of diseased vessels was strongly related to preference for medical, PTCA or CABG treatment (p for linear trend <0.001). Mild versus severe anginal symptoms were associated with inappropriate angiography (OR 2.0 (95 per cent CI 0.9-9.8), although this effect was stronger when only the cardiologists' ratings were considered (OR 10.1 (95 per cent CI 2.4-42.6)). CONCLUSION: These are the first UK ratings of appropriateness covering all three procedures. The associations with clinical factors provide evidence of the internal consistency of these ratings. Prospective validation of these ratings against clinical outcomes is under way in the ACRE study.

Aged↗
PubMed1997

Coronary artery bypass graft surgery in dialysis patients.

OBJECTIVE: To examine the short term results and long term survival of patients on long term dialysis undergoing coronary artery bypass graft surgery. METHODS: A retrospective analysis of 19 patients on established dialysis who underwent coronary revascularisation between 1983 and 1995; 14 patients (73%) had class IV angina and five (25%) had unstable angina requiring heparin and nitrate infusions before surgery. RESULTS: The 30 day mortality was 5%. Follow up was completed in the remaining 18 patients. The mean follow up time was 34 months (range eight to 61). During the follow up period four patients died of cardiac causes. The actuarial survival at one, two, and three years was 87%, 78%, and 59%, respectively. The overall functional status was significantly improved compared to preoperative levels, with a mean Karnofsky score of 76% (p < 0.01) at three years. CONCLUSIONS: Coronary artery bypass graft surgery can be performed with increased but acceptable morbidity and mortality in chronic dialysis patients. It results in considerable improvement in symptoms and functional status. However, long term survival is limited and this requires further investigation.

Adult↗
PubMed1997

Mediastinitis in patients undergoing cardiopulmonary bypass: risk analysis and midterm results.

BACKGROUND: Deep sternal wound infection (mediastinitis) occurred in 21 out of 4043 consecutive patients who underwent a cardiopulmonary bypass procedure (incidence of 0.4%). METHODS: Clinical characteristics of patients who developed mediastinitis (group I) were compared to those of patients who had no mediastinal infection (group II). RESULTS: Hospital mortality was significantly higher in group I (14% vs 3.8%) (p<0.001). Mean hospital stay was longer in group I (36 days vs 7 days) (p<0.001). Multivariate analysis identified the following variables as significant risk factors for developing postoperative mediastinitis: diabetes; relative risk (RR)=3.02, 95% confidence limits (CL)=1.68-5.45, resternotomy for bleeding: RR=5.43, CL=1.85-15.92, associated leg wound infections; RR=16.55, CL=5.32-51.49, the need for 3 or more units of blood transfusion; RR=2.48, CL=1.82-3.39, obesity; RR 4.96, CL 2-12.25. Group I patients were categorised according to a recently proposed classification for mediastinitis (reference 1). Type I (n=17), mediastinitis presenting within 2 weeks following surgery in the absence of risk factors. Type II (n=2), mediastinitis presenting at 2-6 weeks following surgery in the absence of risk factors. Type IIIA (n=2), mediastinitis type I in the presence of one or more risk factor(s). Wound debridement and closed mediastinal irrigation was performed in 19 patients; 15 cases with type I, 2 with type II, and 2 with type IIIA. Primary closure without irrigation was performed in 2 type I patients. The primary intervention failed in 3 patients, two of whom died. A third patient died 4 weeks after an apparently successful treatment of type I mediastinitis. Midterm follow-up (mean of 18 months) of 18 patients showed that 16 patients were alive and well, there was one late death, and one patient had chronic wound pain. CONCLUSION: Diabetes, obesity, associated leg-wound infection, and the need for repeated blood transfusions are associated with high risk of mediastinitis. Closed mediastinal irrigation for mediastinitis type I can yield satisfactory functional and cosmetic midterm results.

Aged↗
PubMed1996

Emergency thoracotomy for thoracic trauma in the accident and emergency department: indications and outcome.

To assess the efficacy of emergency thoracotomy performed for thoracic trauma in the accident and emergency department, a retrospective analysis of patients who underwent this procedure and were brought to hospital by the Helicopter Emergency Medical Service was carried out. Between 1991 and 1994, 16 patients had emergency thoracotomy performed in the accident department. Twelve patients had sustained blunt trauma and four patients had sustained penetrating injuries. Three patients first assessed at the scene and 11 patients on arrival at the emergency department had Glasgow Coma Scores < 3. Eight thoracotomies were performed by the cardiothoracic team and eight by the trauma team. There was one survivor in this group; he had been stabbed at multiple sites and emergency thoracotomy was required to control bleeding from an intercostal vessel. Our results demonstrate experience of one of the first phase Level One trauma centres in the United Kingdom. From our small series, we believe that selection criteria for emergency thoracotomy in trauma patients need to be revised. From this series and a review of the literature, patients with penetrating injuries, vital signs at the scene and those with a high index of suspicion for tamponade seem to benefit most from thoracotomy in the emergency setting.

Adolescent↗
PubMed1994

Lack of cardioprotective efficacy of allopurinol in coronary artery surgery.

OBJECTIVE: To examine the cardioprotective efficacy of allopurinol in patients undergoing elective coronary artery surgery. DESIGN: Prospective randomised trial. SETTING: London teaching hospital. PATIENTS: Twenty patients with at least moderately good left ventricular function undergoing elective coronary artery surgery and requiring at least two bypass grafts. INTERVENTIONS: Patients were randomised to receive allopurinol (1200 mg in two divided doses) or to act as controls. MAIN OUTCOME MEASURE: The primary determinant of the efficacy of myocardial protection was serial measurement (preoperatively and subsequently at one, six, 24, and 72 hours after the end of cardiopulmonary bypass) of cardiac troponin T (cTnT) a highly sensitive and specific marker of myocardial damage. Additional evidence was provided by serial measurement of the MB-isoenzyme of creatine kinase (CK-MB) and myoglobin, ECG changes, and clinical outcome. RESULTS: There was no significant difference in age, ejection fraction, number of grafts, bypass times, or cross clamp times between the two groups. In both groups there was a highly significant (p < 0.01) rise in cTnT, CK-MB, and myoglobin. Peak concentrations were reached between one (CK-MB and myoglobin) and six hours (cTnT) after the end of cardiopulmonary bypass. At 72 hours cTnT concentrations were six times higher than baseline concentrations whereas CK-MB and myoglobin were approximately double baseline concentrations. There was no significant difference in cTnT, CK-MB, or myoglobin between the allopurinol and control groups at any time. There was no diagnostic ECG evidence of perioperative infarction in any patient. CONCLUSION: Unlike previous reports this study did not show that allopurinol had a cardioprotective effect in patients with good left ventricular function undergoing elective coronary artery surgery.

Allopurinol↗
PubMed1994

Intermittent ischaemic arrest and cardioplegia in coronary artery surgery: coming full circle?

OBJECTIVE: To compare the cardioprotective efficacy of cold crystalloid cardioplegia and intermittent ischaemic arrest in patients undergoing elective coronary artery surgery. DESIGN: Prospective randomised trial. SETTING: London teaching hospital. SUBJECTS: 20 patients with at least moderately good left ventricular function undergoing elective coronary artery surgery by one experienced surgeon and needing at least two bypass grafts. INTERVENTIONS: Patients were randomised to cold crystalloid cardioplegia or intermittent ischaemic arrest. MAIN OUTCOME MEASURES: The primary determinant of the efficacy of myocardial protection was serial measurement (before and at 1, 6, 24, and 72 hours after the end of cardiopulmonary bypass) of cardiac troponin T (cTnT), a highly sensitive and specific marker of myocardial damage. RESULTS: There was no significant difference in age, ejection fraction, number of grafts, bypass times, or cross clamp times between the two groups. One patient in the cardioplegia group had a perioperative infarct and was excluded from further study. In both groups there was a significant increase in cTnT, with peak concentrations being reached 6 hours after the end of cardiopulmonary bypass and remaining significantly high at 72 hours. At 6 hours the median (75% interquartile range) concentrations of cTnT were similar in both groups (1.8 (1.0-3.6) micrograms/l for cardioplegia v 1.9 (1.0-3.5) micrograms/l for intermittent ischaemic arrest). CONCLUSION: This trial shows that intermittent ischaemic arrest, even without systemic cooling or venting of the left ventricle, provides a similar level of myocardial protection to cardioplegia in patients with moderate left ventricular function and short ischaemic times.

Coronary Artery Bypass↗
PubMed1994

Emergency surgical revascularisation for coronary angioplasty complications.

OBJECTIVES: To evaluate trends in referrals for emergency operations after percutaneous transluminal coronary angioplasty (PTCA) complications; to analyse morbidity and mortality and assess the influence of PTCA backup on elective surgery. DESIGN: A retrospective analysis of patients requiring emergency surgical revascularisation within 24 hours of percutaneous transluminal coronary angioplasty. PATIENTS: Between January 1980 and December 1990, 75 patients requiring emergency surgery within 24 hours of percutaneous transluminal coronary angioplasty. SETTING: A tertiary referral centre and postgraduate teaching hospital. RESULTS: 57 patients (76%) were men, the mean age was 55 (range 29-73) years, and 30 (40%) had had a previous myocardial infarction. Before PTCA, 68 (91%) had severe angina, 59 (79%) had multivessel disease, and six (8%) had a left ventricular ejection fraction of less than 40%. A mean of 2.1 grafts (range one to five) were performed; the internal mammary artery was used in only one patient. The operative mortality was 9% and inhospital mortality was 17%. There was a need for cardiac massage until bypass was established in 19 patients (25%): this was the most important outcome determinant (P = 0.0051) and was more common in those patients with multivessel disease (P = 0.0449) and in women (P = 0.0388). In 10 of the 19 cases a vacant operating theatre was unavailable, the operation being performed in the catheter laboratory or anaesthetic room. These 19 patients had an operative mortality of 32% and inhospital mortality of 47%, compared with 2% and 7% respectively for the 56 patients who awaited the next available operating theatre. Complications included myocardial infarction, 19 patients (25%); arrhythmias, 10 patients (3%); and gross neurological event, two patients (3%). The mean intensive care unit stay was 2.6 days (range 1 to 33 days) and the mean duration of hospital admission was 13 days (range 5-40 days). CONCLUSIONS: Patients undergoing emergency surgery after PTCA complications have a substantially increased inhospital mortality and morbidity. PTCA in this unit continues to require surgical cover. Delays in operating on stable patients in centres which operate a "next available theatre" backup policy may not differ from some units performing PTCA with offsite cover for PTCA complications. Particularly in the presence of multivessel disease, however, PTCA complications may be associated with the need for "crash" bypass and such patients are unlikely to survive hospital transfer. The proportion of patients requiring "crash" bypass has increased during the period reviewed because of the extent of disease in the emergency surgical group increased. These results indicate that surgery should not be denied to these patients.

Adult↗
PubMed1992

Wenckebach type heart block following spinal anaesthesia for caesarean section.

A case is described of complete heart block during spinal anaesthesia for Caesarean section in a fit 23 yr-old-woman. This developed shortly after the institution of the block, with the height of the block below T5 and in the absence of hypotension. The patient was resuscitated successfully with vagolytic and alpha-agonist drugs. A Wenckebach block persisted for a short period postoperatively. The importance of instituting monitoring before the beginning of anaesthesia and the immediate availability of atropine and alpha-agonists before the initiation of spinal anaesthesia is stressed.

Adult↗