Intravenous nifedipine for prevention of myocardial ischaemia after coronary revascularization

Radial Artery Graft Treatment With Phenoxybenzamine is Clinically Safe and May Reduce Perioperative Myocardial Injury

BACKGROUND

Phenoxybenzamine effectively reduces radial artery (RA) spasm in vitro, but clinical data supporting its use during coronary revascularization are lacking. Therefore, the purpose of this study was to evaluate the clinical safety and efficacy of RA treatment with phenoxybenzamine.

METHODS

Data were collected prospectively on 698 patients who underwent coronary artery bypass grafting with a RA between 1997 and 2005. Of these, 311 patients received RA grafts incubated in 2 mg/mL phenoxybenzamine for 15 minutes, and 387 patients received RA grafts treated with verapamil and nitroglycerin (VG solution). Demographic, operative, and postoperative data were compared retrospectively using multivariate regression techniques.

RESULTS

The incidence of perioperative myocardial events (defined as either low cardiac output syndrome or perioperative myocardial infarction) was significantly reduced in the phenoxybenzamine group (6.8% vs 11.9%, phenoxybenzamine vs VG solution; p = 0.03). Perioperative myocardial enzyme release, as measured by postoperative maximum creatine kinase, was also reduced in the phenoxybenzamine group (743.0 +/- 677.9 vs 937.2 +/- 1236.8 U/L, phenoxybenzamine vs VG solution; p = 0.014). After adjusting for patient and procedural factors, the use of phenoxybenzamine was independently associated with reductions in peak creatine kinase (by -343.0 +/- 136.7 U/L; p = 0.012) and peak troponin T level (by -0.50 +/- 0.19 ng/mL; p = 0.010). No differences in vasopressor support, length of stay, or other complications were observed.

CONCLUSIONS

Treatment of RA grafts with phenoxybenzamine was associated with a reduction in perioperative myocardial injury and adverse cardiac events in this study population. Investigations to further evaluate the potential benefits of phenoxybenzamine in randomized settings are warranted.

Calcium antagonists reduce cardiovascular complications after cardiac surgery: a meta-analysis

OBJECTIVES

We sought to determine the efficacy of calcium antagonists (CAs) in reducing death, myocardial infarction (MI), ischemia, and supraventricular tachyarrhythmia (SVT) after cardiac surgery.

BACKGROUND

Calcium antagonists may reduce complications after cardiac surgery-namely, death, MI, and renal failure. However, they are underused, possibly due to the results from previous observational studies.

METHODS

Both MEDLINE (1966 to December 2001) and EMBASE (1980 to December 2001) were searched, with supplementation by reference list searches. No language restrictions were applied. Included studies were randomized, controlled trials (RCTs) evaluating preoperative, intraoperative, or postoperative (first 48 h) CA use (intravenous or oral) during aortocoronary bypass or valve surgery. Studies were excluded if they exclusively recruited transplant recipients, individuals <18 years old, or patients with pre-existing SVT. Two reviewers independently evaluated study quality by using the Jadad score; a minimal score of 1/5 was required. Forty-one studies, encompassing 3,327 patients, were included. No studies assessed treatment exclusively with short-acting oral nifedipine. Treatment effects were calculated using the random-effects model. Heterogeneity was assessed using the Q test.

RESULTS

Calcium antagonists significantly reduced MI (odds ratio [OR] 0.58, 95% confidence interval [CI] 0.37 to 0.91; p = 0.02) and ischemia (OR 0.53, 95% CI 0.39 to 0.72; p < 0.001). Non-dihydropyridines significantly reduced SVT (OR 0.62, 95% CI 0.41 to 0.93; p = 0.02). Calcium antagonists were associated with trends toward decreased mortality during aortocoronary bypass (OR 0.66, 95% CI 0.26 to 1.70, p = 0.4).

CONCLUSIONS

Use of CAs during cardiac surgery significantly reduced rates of MI, ischemia, and SVT. Further study using large RCTs is justified.

Interaction of L-arginine and phosphodiesterase inhibitors in vasodilation of the porcine internal mammary artery

We tested the hypothesis that L-arginine (the substrate for nitric oxide production)-combined with amrinone, milrinone (Type III phosphodiesterase [PDE] inhibitors), zaprinast, or sildenafil (Type V PDE inhibitors)-would vasodilate synergistically. Internal mammary artery segments were excised from anesthetized swine, divided into rings, and suspended in a tissue bath at 37 degrees C. Force of contraction was measured during dose-response testing of combinations of L-arginine and amrinone, milrinone, zaprinast, or sildenafil. Amrinone and milrinone were additive to L-arginine. N(G)-methyl-L-arginine (L-NMA) inhibited the effects of milrinone but not amrinone. The effective concentration of amrinone eliciting 50% relaxation (EC(50)) was 3.8E-05M (n = 6) when given alone and 4. 4E-05M (n = 6) with L-NMA. Milrinone had EC(50) = 6.0E-06M alone (n = 6) and 2.8E-05M (n = 6) with L-NMA. Zaprinast (EC(50) = 6.5E-05M, n = 6) and sildenafil (EC(30) = 1.8E-05M, n = 6) were synergistic with L-arginine. L-NMA blocked their effects, increasing the EC(50) for zaprinast to 9.9E-03M and the EC(30) for sildenafil to 6.1E+02M. In conclusion, L-arginine is additive to the vasodilation of the type III PDE inhibitors, amrinone and milrinone, but synergistic with the type V PDE inhibitors, zaprinast and sildenafil.

IMPLICATIONS

Amrinone and milrinone, Type III cAMP-dependent phosphodiesterase inhibitors, are additive to L-arginine-dependent vasodilation. Zaprinast and sildenafil, Type V cGMP-dependent phosphodiesterase inhibitors, are synergistic with L-arginine.

Effects of nicardipine and nitroglycerin on perioperative myocardial ischemia in patients undergoing coronary artery bypass surgery

Perioperative myocardial ischemic episodes are predictive of adverse cardiac outcomes after coronary artery bypass surgery. We compared the efficacy of continuous infusions of nicardipine (group NIC) and nitroglycerin (group NTG) in reducing the frequency and severity of myocardial ischemic episodes. Patients received either a nicardipine infusion, 0.7 to 1.4 microg/kg/min (n = 30), nitroglycerin infusion, 0.5 to 1 microg/kg/min (n = 30), or neither medication (group C; n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes were considered as ST segment depressions or elevations of 1 mm or greater from baseline, each at J + 60 milliseconds and lasting 1 minute or greater, using a two-channel Holter monitor. Only nicardipine significantly decreased the duration (3.2 +/- 1.2 min/h) and the area under the ST time curve (AUC; 5.7 +/- 15.7 AUC/h) of 1-mm or greater myocardial ischemic episodes compared with group C (17.2 +/- 5.6 min/h and 30.1 +/- 49 AUC/h, respectively) during the intraoperative postbypass period. A trend toward lower frequency, duration, and area under the ST time curve of myocardial ischemic episodes was observed in group NIC compared with group NTG. Cardiac indices and mixed venous oxygen saturations were significantly greater, whereas systemic pressures were less in group NIC compared with group NTG for the same period. These results suggest that nicardipine, but not nitroglycerin, decreased the duration and area under the ST time curve of myocardial ischemic episodes shortly after coronary revascularization. Larger studies are required to verify the efficacy of nicardipine in reducing the severity of myocardial ischemia during cardiac surgery.

Antiischemic effects of nicardipine and nitroglycerin after coronary artery bypass grafting

BACKGROUND

We assessed the efficacy of a continuous infusion of nicardipine and nitroglycerin in reducing the incidence and severity of perioperative myocardial ischemia during elective coronary artery bypass grafting procedures in a prospective, randomized, controlled study.

METHODS

Patients received either nicardipine infusion (0.7 to 1.4 microg x kg(-1) x min(-1); n = 30) or nitroglycerin (0.5 to 1 microg x kg(-1) x min(-1); n = 30) or neither medication (n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes (MIE) were considered to have occurred with ST-segment depressions or elevations of at least 1 mm and at least 2 mm (for both depressions or elevations), each at J + 60 ms and lasting at least 1 minute, using a two-channel Holter monitor.

RESULTS

Only nicardipine significantly decreased the duration (p = 0.02) of the 1-mm or greater minutes per hour (3.2 +/- 1.2 minutes per hour) and eliminated the number (p = 0.02) of the 2-mm or greater minutes per hour (zero minutes per hour) when compared with control patients (17.2 +/- 5.6 minutes per hour and 0.17 minutes per hour, respectively) during the intraoperative postbypass period.

CONCLUSIONS

Our results suggest that nicardipine lessened the severity of myocardial ischemia shortly after coronary revascularization and could be considered as an alternative to standard antiischemic therapy.

DA1-receptor stimulation by fenoldopam in the treatment of postcardiac surgical hypertension

BACKGROUND

Besides adequate analgesia, sedation and ventilation, postcardiac surgical hypertension has to be treated frequently with vasoactive drugs to avoid possible complications. In this study the hemodynamic effects of the DA1-receptor agonist fenoldopam (F) are compared to those of the Ca-channel antagonist nifedipine (N).

METHODS

Postoperatively, 64 CABG-patients with a mean arterial pressure (MAP) of more than 105 mmHg over 10 min were investigated. Patients with compromised ventricular function, insufficient surgical repair, arrhythmia or an ECG unable to detect myocardial ischemia were excluded. The study drugs (initial dosage: F: 0.8; N: 0.3 micrograms.kg-1.min-1) were given continuously via a central venous catheter to reduce and to maintain the MAP between 80 and 95 mmHg. Hemodynamic parameters were determined using thermodilution technique.

RESULTS

A significant reduction of the MAP (F: from 121 +/- 11 to 83 +/- 4, N: from 119 +/- 8 to 82 +/- 9 mmHg) and of the calculated systemic vascular resistance (SVR) (F: 2110 +/- 500 to 970 +/- 200, N:1980 +/- 660 to 1020 +/- 300 dyn.s.cm-5) were noted in both groups, whereby in the F group the therapeutic goal could be achieved more quickly with the dosage regimen chosen. As a result, a marked increase of heart rate, cardiac index and stroke volume index could be observed, which was more pronounced due to the initially stronger decrease of SVR with F. There was also a stronger decrease of pulmonary vascular resistance in the F group, but the indices of right ventricular function did not differ between the groups.

CONCLUSION

Fenoldopam seems to be an efficient alternative to nifedipine, especially because of its more rapid onset of action.

Con: intraoperative myocardial ischemia is not benign

The principal importance of intraoperative ischemia is its consistent association with adverse outcome. In coronary artery surgery the finding of prebypass ischemia is an important predictor, and postbypass ischemia is a critical predictor of adverse outcome. One in three patients with postbypass ischemia will suffer an adverse outcome in CABG. Furthermore, prevention of postbypass ischemia may improve outcome in CABG. Clearly, intraoperative ischemia in CABG surgery is an ominous sign that should be regarded with the utmost concern by anesthesiologists. In noncardiac surgery, intraoperative ischemia also indicates about a one in three chance of adverse outcome. Although it is less sensitive than postoperative ischemia, it may have superior positive predictive power and specificity. Most importantly, intraoperative monitoring for ischemia is currently available to most patients, whereas extended postoperative monitoring is not. The finding of intraoperative ischemia defines a high-risk group of patients who may merit special monitoring and treatment. To regard intraoperative ischemia as benign would be inconsistent with available information.