B-type natriuretic peptide predicts postoperative cardiac events and mortality after elective open abdominal aortic aneurysm repair.

OBJECTIVE: The aim of this study was to determine if a single preoperative B-type natriuretic peptide (BNP) level correlated with perioperative cardiac events, cardiac death, and all-cause mortality in elective open abdominal aortic aneurysm (AAA) repair in the short term, intermediate term, and long term. METHODS: A prospective, 2-year multicenter observational cohort study in the three vascular units in Glasgow was performed. All patients who were admitted for elective open AAA repair were recruited. Preoperative BNP levels were performed and batch analyzed at the end of the study. Postoperative screening for cardiac events (nonfatal myocardial infarction and cardiac death) was performed at 2, 5, and 30 days. Follow-up for all-cause mortality was sustained to a minimum of 3 years, where possible. RESULTS: A total of 106 of 111 patients were recruited. Median BNP concentrations were higher in the 16 patients (15%) with immediate postoperative cardiac events (P = .001) and the five with cardiac death (P = .043). Area under the receiver-operating characteristic (AUC) curve analysis indicated BNP concentrations of 99.5 pg/mL best predicted cardiac events (AUC, 0.927), and 448 pg/mL predicted cardiac death (AUC, 0.963). BNP also predicted all-cause mortality in the short-term (P = .028), intermediate-term (P < .001), and long-term (P < .001) postoperative periods. CONCLUSIONS: Preoperative serum BNP concentration predicted postoperative cardiac events, cardiac death, and all-cause mortality in patients undergoing elective open AAA repair on short-term, intermediate-term, and long-term follow-up on an individual basis with greater accuracy than currently available risk prediction tools.

Pharmacokinetics and tissue penetration of vancomycin continuous infusion as prophylaxis for vascular surgery.

OBJECTIVES: To determine the tissue penetration of vancomycin into perivascular fat and arterial wall during a continuous infusion of vancomycin, given as prophylaxis for vascular surgery. PATIENTS AND METHODS: Patients undergoing arterial reconstruction requiring antibiotic prophylaxis were included. Patients received a loading infusion of vancomycin the evening prior to surgery followed by a continuous 24 h infusion, calculated according to renal function. Three peri-operative serum samples and intra-operative perivascular fat and arterial wall samples were collected for vancomycin assay. RESULTS: Twenty-eight patients were included. Three serum samples were obtained from all patients, fat samples were available from 27 (96.4%) patients and vessel wall samples were available from 23 (82.1%) patients. Serum vancomycin concentrations were maintained within a relatively narrow range, while fat and arterial wall concentrations were highly variable. CONCLUSIONS: This study has shown that prophylactic administration of vancomycin with a loading infusion followed by a continuous infusion before and during vascular surgery achieves serum and vascular tissue concentrations that are above the MICs for most common organisms implicated in post-operative graft infection. However, penetration into perivascular fat tissues is poor.

Vancomycin continuous infusion as prophylaxis for vascular surgery.

Prosthetic graft infection is a devastating complication of vascular surgery that occurs in 3%-5% of clean prosthetic procedures. Staphylococci are the most frequently isolated pathogens, and thus surgical prophylaxis regimens often include vancomycin. However, the efficacy of these regimens in ensuring a required concentration of antibiotic is uncertain. This study aimed to determine if a continuous vancomycin infusion regimen administered perioperatively as surgical prophylaxis for vascular procedures maintained an adequate serum concentration. Thirty-four consecutive patients undergoing a vascular procedure requiring a prosthetic graft or patch were given vancomycin prophylaxis. Each patient received a loading dose calculated according to body weight 12 hours before surgery. A 24-hour continuous infusion was then started, based on calculated creatinine clearance. Serum vancomycin concentrations were checked on induction of anesthesia, 2 hours postoperatively, and at the end of the infusion. Perioperative fluid administration and blood loss were recorded. An estimated creatinine clearance was repeated on the second postoperative day. Of the 34 patients recruited, 7 did not have the anticipated procedure and 6 patients had incomplete sample collection. Twenty-one patients with complete sample collection were analyzed. The target concentration (10-25 mg/L) was achieved in 81% of all samples. All patients achieved the target concentration at 1 or more time points. The regimen employed provided appropriate concentrations at the time of intervention. No potentially toxic concentrations or adverse reactions to vancomycin were encountered. Vancomycin given as a continuous infusion delivers adequate serum concentration. Long-term graft infection rates are needed to show a clinical effect.

Cardiopulmonary responses to treadmill and cycle ergometry exercise in patients with peripheral vascular disease.

BACKGROUND: Peripheral arterial disease (PAD) presenting as intermittent claudication (IC) is routinely assessed as the distance or time walked to the onset of pain, which often occurs before significant cardiopulmonary stress and is subject to confounding factors such as increased body mass and altered gait. Thus, where exercise-induced cardiovascular stress is desirable, such as in cardiac stress testing or clinical trials, an alternative modality of exercise is required. Cycling will circumvent several of the associated problems of treadmill walking and may provide an alternative preferable method of exercise, although there is limited information on the physiologic response of patients with PAD to cycling. This study compared the peak cardiorespiratory responses and the repeatability of cycling and treadmill exercise in patients with PAD. METHODS: Ten men (mean age, 54 +/- 10 years) with stable IC completed two incremental exercise tests to the limit of tolerance on a treadmill and a cycle ergometer after familiarization with the outcome measures of exercise duration, work performed, respiratory gas exchange variables using continuous breath-by-breath measurement, heart rate, and ratings of perceived pain. RESULTS: Both methods of exercise assessment revealed high reproducibility in terms of absolute claudication time (treadmill, r = 0.95; cycle, r = 0.91), time to volitional fatigue (treadmill, r = 0.96; cycle, r = 0.91), and cardiopulmonary exercise responses such as the lactate threshold (treadmill, r = 0.95; cycle, r = 0.94), peak heart rate (treadmill, r = 0.94; cycle, r = 0.96), and peak oxygen uptake (treadmill, r = 0.98; cycle, r = 0.87). Cycling induced significantly higher cardiopulmonary responses (peak heart rate, peak carbon dioxide output, peak minute ventilation, and respiratory exchange ratio) than treadmill exercise. There was no difference in time to volitional fatigue or in absolute claudication time between exercise modalities. CONCLUSION: These results demonstrate that exercise testing using cycling offers an alternative method of cardiopulmonary testing for patients with IC that is equally reliable and reproducible to treadmill walking. Cycling may be preferable to treadmill exercise because it induces greater cardiopulmonary and metabolic responses and is better tolerated by patients.