How silent is perioperative myocardial ischemia? A hemodynamic, electrocardiographic, and biochemical study in patients undergoing coronary artery bypass graft surgery

OBJECTIVE: To analyze the relationship among Holter electrocardiogram (ECG) recordings, hemodynamic measurements indicative of global myocardial oxygen balance, and serum cardiac troponin I concentrations (cTnI) in the early postoperative period after coronary artery bypass graft (CABG) surgery. DESIGN: Prospective observational study. SETTING: University teaching hospital. PARTICIPANTS: Thirty patients undergoing CABG surgery. INTERVENTIONS: ECG measurements consisted of Holter and standard ECG recordings. Hemodynamic measurements included heart rate, systolic and diastolic blood pressure (SBP, DBP), pulmonary capillary wedge pressure, and cardiac index (CI). Derived indices included tension time index (TTI), rate-pressure product, pressure work index (PWI), and endocardial viability ratio (EVR). Serial measurements of cTnI concentrations were measured postoperatively; the area under the cTnI concentration time curve was calculated for each patient (AUC cTnI). MEASUREMENTS AND MAIN RESULTS: Episodes of myocardial ischemia were associated with small but significant rises in SBP (p = 0.01), DBP (p = 0.001), and TTI (p = 0.005) compared with periods without ischemia in the same patients. Serum cTnI concentrations 24 hours after cardiopulmonary bypass (p = 0.03) and AUCcTnI (p = 0.01) values were greater in patients who developed ECG myocardial ischemia compared with patients who did not. CONCLUSIONS: The small changes in hemodynamics seen, although statistically significant, are unlikely to be the primary cause of the ischemia. They more likely reflect an independent process that causes or occurs as a result of ischemic episodes. Ischemic episodes detected by the Holter monitor are associated with significant release of cardiac troponin from the myocardium.     

Preoperative laser therapy in a patient with resectable bronchogenic carcinoma and severe coronary artery disease.

A 67 year old man with severe coronary artery disease was found to have a resectable bronchogenic carcinoma. Myocardial revascularisation and lung resection were considered to be unduly hazardous as either separate or combined operations. Preoperative laser therapy, however, enabled the two procedures to be performed in greater safety in the most appropriate sequence.     

High frequency jet ventilation and gas trapping

We have compared three types of high frequency jet ventilation (HFJV) with conventional positive pressure ventilation in patients recovering from elective coronary artery bypass surgery. Twelve patients were allocated randomly to receive HFJV at ventilatory frequencies of 60, 100, 150 and 200 bpm from a standard jet ventilator at either the proximal or distal airway (HFJV.p and HFJV.d), or from a valveless high frequency jet ventilator acting as a pneumatic piston (VPP). Trapped gas volume (Vtr), cardiac index (CI) and right ventricular ejection fraction (RVEF) were measured. Vtr was related to the type of HFJV used (P < 0.05) and ventilatory frequency (P < 0.05). CI decreased with increasing rate of HFJV (P < 0.05) and there were significant differences between the three types of HFJV (P < 0.05). RVEF showed a linear relationship with ventilatory frequency (P < 0.05) decreasing most with the VPP. The decrease in RVEF was associated with an increase in right ventricular end-systolic volume (P < 0.05) suggesting that an increase in right ventricular afterload was the cause. The same three types of HFJV were compared using a lung model with variable values of compliance and resistance, to assess the impact of lung mechanics on gas trapping (Vtr, ml). Lung model compliance (C) was set at 50 or 25 ml cm H2O-1 and resistance (R) at 5 or 20 cm H2O litre-1 s, where values of 50 and 5, respectively, are normal. Vtr increased with ventilatory frequency for all types of jet ventilation (P < 0.05), varying with the type of jet ventilation used (P < 0.05).      

Recombinant human antithrombin III restores heparin responsiveness and decreases activation of coagulation in heparin-resistant patients during cardiopulmonary bypass

OBJECTIVES: We sought to evaluate the efficacy of recombinant human antithrombin III for restoration of heparin responsiveness in heparin-resistant patients scheduled for cardiac surgery. METHODS: This was a multicenter, randomized, double-blind, placebo-controlled study in heparin-resistant patients undergoing elective cardiac surgery. Patients were considered heparin resistant if the activated clotting time was less than 480 seconds after 400 U/kg heparin. Fifty-two heparin-resistant patients were randomized into 2 cohorts. One cohort received a single bolus (75 U/kg) of recombinant human antithrombin III (n = 28), and the other, the placebo group (n = 24), received a normal saline bolus. If the activated clotting time remained less than 480 seconds, this was defined as treatment failure, and 2 units of fresh frozen plasma were transfused. Patients were monitored for adverse events during hospitalization. RESULTS: Six (21%) of the patients in the recombinant human antithrombin III group received fresh frozen plasma transfusions compared with 22 (92%) of the placebo-treated patients ( P < .001). Two units of fresh frozen plasma did not restore heparin responsiveness. There was no increased incidence of adverse events associated with recombinant human antithrombin III administration. Postoperative 24-hour chest tube bleeding was not different in the 2 groups. Surrogate measures of hemostatic activation suggested that there was less activation of the hemostatic system during cardiopulmonary bypass in the recombinant human antithrombin III group. CONCLUSION: Treatment with recombinant human antithrombin III in a dose of 75 U/kg is effective in restoring heparin responsiveness and promoting therapeutic anticoagulation for cardiopulmonary bypass in the majority of heparin-resistant patients. Two units of fresh frozen plasma were insufficient to restore heparin responsiveness. There was no apparent increase in bleeding associated with recombinant human antithrombin III.     

Decline in research publications from the United Kingdom in anaesthesia journals from 1997 to 2006

We undertook this survey to identify the trend in the published output of original research in anaesthesia emanating from the United Kingdom (UK) in a 10-year period from 1997 to 2006, inclusive. We examined seven major anaesthetic journals for each of the 10 years, and four other specialist journals for the years 1997, 2000, 2003 and 2006. We included papers on experimental research, randomised controlled clinical trials, large observational studies and case series, formal equipment and apparatus assessments, but we excluded editorials, comments, reviews including systematic reviews, special articles, small case series and case reports, questionnaire surveys of clinical practice and correspondence. We found a highly significant reduction in published research output from the UK in the period under study (% change per year; −5.7 (95% CI −7.4 to −4.0), a trend which was significantly different (p   < 0.001) from the trend of changes in research publications worldwide (−1.0% change per year; 95% CI −1.7 to 0.0). We discuss the implications of these findings for UK anaesthesia research strategy.     

Systemic pattern of free radical generation during coronary bypass surgery.

Diffuse impairment of ventricular function after cardiac surgery may be related to the generation during reperfusion of the myocardium of free radicals derived from oxygen. Fifteen patients undergoing elective coronary bypass surgery were studied by previously described assays for peroxidised lipids and for isomerised lipids which were used as indices of free radical activity. Serial blood samples were obtained from systemic arterial, mixed venous, and coronary sinus catheters before, during, and after the ischaemic period. The patients underwent coronary artery surgery on cardiopulmonary bypass with a membrane oxygenator, relative hypothermia 30-34 degrees C, and intermittent cross-clamping of the aorta. During the ischaemic periods there were no significant changes in the indices of free radical activity. During the reperfusion phase there was a significant increase in free radical indices in arterial and mixed venous blood. A small rise in free radical indices in coronary venous blood was not statistically significant. These data indicate that free radical activity is increased in patients shortly after the cessation of cardiopulmonary bypass. The pattern of distribution between the different sampling sites suggests that much of the observed increase in isomerised and peroxidised lipids originates from tissues other than the myocardium.     

Comparison of clevidipine with sodium nitroprusside in the control of blood pressure after coronary artery surgery

BACKGROUND AND OBJECTIVE: We set out to compare the efficacy of clevidipine and sodium nitroprusside infusions in the control of blood pressure and the haemodynamic changes they produce in hypertensive patients after operation for elective coronary bypass grafting. METHODS: Thirty patients were randomly allocated to receive either clevidipine or sodium nitroprusside after their mean arterial pressure (MAP) had reached > 90 mmHg for at least 10 min in the postoperative period. The MAP was continuously measured and related to time. Thus, the efficacy of the drugs in controlling arterial pressure could be inversely related to the total area under the MAP-time curve outside a target MAP range of 70-80 mmHg normalized per hour (AUC(MAP) mmHg min h(-1)). Haemodynamic variables and the number of dose-rate adjustments required to maintain MAP were also studied. RESULTS: There was no statistically significant difference in the efficacy (AUC(MAP) mmHg min h(-1)) of clevidipine (106 +/- 25 mmHg min h(-1)) compared with sodium nitroprusside (101 +/- 28 mmHg min h(-1)). Nor was any significant difference found in the total number of dose adjustments required to control MAP within the target range. The heart rate in patients receiving clevidipine increased less than in those given sodium nitroprusside. Stroke volume, central venous pressure and pulmonary artery pressure were significantly reduced upon administration of sodium nitroprusside but not of clevidipine. CONCLUSIONS: There was no significant difference between clevidipine and sodium nitroprusside in their efficacy in controlling MAP. The haemodynamic changes, including tachycardia, were less pronounced with clevidipine than with sodium nitroprusside.     

The impact of age on 6-month survival in patients with cardiovascular risk factors undergoing elective non-cardiac surgery

An increasing number of patients aged>or=70 years are presenting for elective non-cardiac surgery. We undertook this study to: (i) compare the nature and distribution of cardiovascular disease (CVD) risk factors in an at risk population of patients aged>or=70 years undergoing elective surgery compared with a younger at risk cohort; and (ii) identify the impact of age and other risk factors on 6-month survival. We conducted a prospective observational study of patients undergoing elective non-cardiac surgery. A total of 1622 patients aged>or=40 years with recognised surgical or patient-specific risk factors for CVD were identified. The patients were divided into two groups; group 1 (aged: 40-69 years) and group 2 (aged>or=70 years). Logistic regression was used to identify the factors associated with 6-month mortality. Odds ratios (OR) and 95% confidence interval (CI) are presented. In hospital, mortality was similar in both groups. However, 6-month mortality in those aged>or=70 years was significantly higher (p=0.001). Cardiovascular symptoms were significantly more common in group 2 (p<0.001) as were cardiovascular-related deaths (p=0.04) at 6 months follow-up. Preoperative cardiovascular preventative therapy was under prescribed in the elderly cohort. Factors independently associated with 6-month mortality were aged>or=70 (OR=3.57, 95% CI: 2.22-5.73), angina (OR=2.0, 95% CI: 1.26-3.20), renal impairment (OR=2.39, 95% CI: 1.17-4.89) also operation type and duration. Despite similar in-hospital mortality, those aged>or=70 years had significantly higher 6-month mortality than the younger surgical cohort. Cardiovascular deaths were significantly higher in patients aged>or=70 years. Effective identification and the management of cardiovascular risk factors may improve 6-month survival.