Automated electrocardiograph ST segment trending monitors: accuracy in detecting myocardial ischemia

Perioperative management of a patient with left ventricular dysfunction and anomalous coronary arteries

Anesthetic management of patients with coronary artery disease undergoing noncardiac surgery is quite challenging. Such patients are at increased risk of perioperative cardiac complications and death. We report an illustrative case of a 62-year-old male with ischemic heart disease and anomalous coronary arteries for obstructed paraumbilical hernia repair.

Transfusion strategy: impact of haemodynamics and the challenge of haemodilution

Blood transfusion is associated with increased morbidity and mortality and numerous reports have emphasised the need for reduction. Following this there is increased attention to the concept of patient blood management. However, bleeding is relatively common following cardiac surgery and is further enhanced by the continued antiplatelet therapy policy. Another important issue is that cardiopulmonary bypass leads to haemodilution and a potential blood loss. The basic role of blood is oxygen transport to the organs. The determining factors of oxygen delivery are cardiac output, haemoglobin, and saturation. If oxygen delivery/consumption is out of balance, the compensation mechanisms are simple, as a decrease in one factor results in an increase in one or two other factors. Patients with coexisting cardiac diseases may be of particular risk, but studies indicate that patients with coexisting cardiac diseases tolerate moderate anaemia and may even benefit from a restrictive transfusion regimen. Further it has been shown that patients with reduced left ventricular function are able to compensate with increased cardiac output in response to bleeding and haemodilution if normovolaemia is maintained. In conclusion the evidence supports that each institution establishes its own patient blood management strategy to both conserve blood products and maximise outcome.

Cardioprotective effect of sevoflurane in patients with coronary artery disease undergoing vascular surgery

OBJECTIVES

The present study was conducted to evaluate the cardioprotective effect of sevoflurane compared with propofol in patients with coronary artery disease (CAD) undergoing peripheral vascular surgery; and to address the question whether a volatile anesthetic might improve cardiac outcome in these patients.

METHODS

One hundred twenty-six patients scheduled for elective peripheral vascular surgery were prospectively randomized to receive either sevoflurane inhalation anesthesia or total intravenous anesthesia. ST-segment monitoring was performed continuously during intra- and post-operative 48 h periods. The number of ischemic events and the cumulative duration of ischemia in each patient were recorded. Blood was sampled in all patients for the determination of cTnI. Samples were obtained before the induction of anesthesia, on admission to the ICU, and at 6, 12, 24, and 48 h after admission to the intensive care unit (ICU). Patients were followed-up during their hospital stay for any adverse cardiac events.

RESULTS

The incidence of ischemia were comparable among the groups [16 (25%) patients in sevoflurane group vs 24 (39%) patients in propofol group; P=0.126]. Duration, cumulative duration, and magnitude of ST-segment depression of ischemic events in each patient were significantly less in sevoflurane group (P=0.008, 0.048, 0.038, respectively). cTnI levels of the overall population were significantly less in sevoflurane group vs propofol group (P values <0.0001) from 6 h postoperative and onward. Meanwhile, cTnI levels at 6, 12, 24, and 48 h after admission to the ICU in patients who presented with ischemic electrocardiographic (ECG) changes were significantly lower in sevoflurane group than in the propofol group (P<0.0001, <0.0001, <0.0001, 0.0003). None of the patients presented with unstable angina, myocardial infarction, congestive heart failure, or serious arrhythmia either during ICU or hospital stay.

CONCLUSION

Patients with CAD receiving sevoflurane for peripheral vascular surgery had significantly lower release of cardiac troponin I at 6 h postoperatively and lasting for 48 h than patients receiving propofol for the same procedure with significant decrease in duration, cumulative duration of ischemic events, and degree of ST depression in each patient.

Does intraoperative evaluation of left ventricular contractile reserve predict myocardial viability? A clinical study using dobutamine stress echocardiography in patients undergoing coronary artery bypass graft surgery

To determine the contractile reserve of the left ventricle during reperfusion as a predictor of myocardial viability in patients undergoing coronary artery bypass graft surgery, we measured the response of left ventricular regional wall motion and thickening by using dobutamine stress echocardiography (DSE) after myocardial revascularization. All patients were monitored with radial and pulmonary arterial catheters, transesophageal echocardiography, standard five-lead clinical electrocardiography, and three-channel Holter electrocardiography. Immediately after separation from cardiopulmonary bypass, dobutamine was administered IV starting at 5 microg. kg(-1). min(-1), with increases in rate every 3 min to 10, 20, 30, and 40 microg. kg(-1). min(-1). Within 1 wk after surgery, resting and redistribution thallium-201 myocardial perfusion imaging (thallium studies) was performed to assess the relationship between the intraoperative contractile response and myocardial viability. One-hundred patients completed DSE up to 10 microg. kg(-1). min(-1), and 85 patients received the larger escalating doses of the DSE. Seventy-two patients had postoperative thallium studies. At the completion of the small-dose dobutamine infusion, 689 (97.7%) of 705 segments had a normal response (improvement), and 16 segments (2.3%) had a positive response (deterioration). During large-dose dobutamine infusion, 577 (95.8%) of 602 segments had a normal response, and 25 segments (4.2%) had a positive response. Myocardial segments that had a positive response during large-dose DSE (48%) were more likely to be considered as nonviable on postoperative thallium studies compared with segments that had a normal response (14.7%) (P < 0.00001). By using thallium studies as the reference standard, the sensitivity of DSE was low (31% and 48% for small- and large-dose DSE, respectively) in predicting nonviable myocardium. However, the specificity was higher (86% and 85% for small- and large-dose DSE, respectively). In a separate analysis of patients who developed new regional wall motion abnormalities (RWMA) in the early intraoperative reperfusion period, 15 (75%) of 20 abnormally contracting myocardial segments had normal postoperative thallium studies. Our results demonstrate that a normal response to DSE is highly specific for viable myocardium; however, a positive response to DSE has low sensitivity in predicting nonviable myocardium. The majority of new postbypass regional wall motion abnormalities appear to be related to stunned myocardium.