Antiischemic effects of nicardipine and nitroglycerin after coronary artery bypass grafting

Hyperinflation of Nitroprusside

Sodium nitroprusside (SNP) is a generically available and rapid-acting intravenous (IV) vasodilator that has been used clinically for decades. Prior to 2013, the cost of SNP was relatively low, and SNP was an affordable option for the treatment of acute hypertension. However, from 2013 to 2017, average wholesale prices for SNP rose to as high as $900 per vial, earning the drug its status as a "hyperinflation drug." Hyperinflation drugs such as SNP pose a significant challenge for pharmacy departments. A multidisciplinary effort involving stakeholders from many backgrounds, including pharmacists, physicians, and nurses, is key to developing an effective plan to address the problem. A therapeutic interchange, wherein a drug with similar efficacy is substituted for another, is often an appropriate strategy in this scenario. Fortunately, alternative drugs with a solid evidence base exist for the management of acute hypertension. The dihydropyridine calcium channel blockers, clevidipine and nicardipine, are IV titratable antihypertensive agents with favorable pharmacokinetic and safety profiles. Various studies indicate that clevidipine and nicardipine are effective alternatives to SNP for indications including hypertensive crisis and postoperative hypertension. Some hospitals have reported significant cost savings without adverse outcomes by substituting clevidipine or nicardipine for SNP. This article is intended to serve as a review of the evidence for clevidipine and nicardipine as potential substitutes for SNP and to provide strategies to successfully implement this therapeutic interchange.

Perioperative diltiazem or nitroglycerin in on-pump coronary artery bypass: A systematic review and network meta-analysis

Background

Arterial graft spasm is a severe complication after coronary artery bypass graft (CABG). Among numerous potential antispasmodic agents, systemic application of diltiazem and nitroglycerin had been investigated most frequently over the past three decades. However, it remains inconclusive if either or both agents could improve patient outcomes by preventing graft spasm when applied perioperatively, and, if so, which one would be a better choice. The current systematic review and network meta-analysis aims to summarize the data from all available randomized clinical trials of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing on-pump CABG in order to define and compare their roles in graft spasm prevention and their impacts on perioperative outcomes.

Methods

We searched Ovid Medline, PubMed, CINAHL, Google Scholar and Cochrane Center for randomized controlled trials that reported outcome effects of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing elective on-pump CABG. Conventional meta-analyses were conducted to evaluate the pairwise comparisons (diltiazem vs. placebo; nitroglycerin vs. placebo; diltiazem vs. nitroglycerin) on perioperative outcomes. Network meta-analyses were implemented to compare the three regimens through direct and indirect comparison.

Results

Twenty-seven studies involving 1,660 patients were included. Pairwise and network meta-analyses found no significant difference in mortality among the groups. There are four studies that reported blood flow measurements of internal mammary artery grafts intraoperatively after dissecting or immediately after distal anastomosis while patients were on continuous intravenous infusion of diltiazem and nitroglycerin. Although insufficient for data synthesis, the measured results from all four studies suggest that both diltiazem and nitroglycerin significantly increased blood flow of arterial grafts compared to placebo. For other perioperative outcomes, compared to diltiazem, patients that received nitroglycerin had higher odds of postoperative atrial fibrillation (OR = 2.67, 95% CI: 1.15 to 6.24) and higher peak serum cardiac enzymes. Patients that received placebo had higher odds of atrial fibrillation (OR = 3.00, 95% CI: 1.18 to 7.63) and lower odds of requiring inotrope support (OR = 0.19, 95% CI: 0.04 to 0.73) compared to diltiazem. Data from the network meta-analysis indicated that diltiazem had significantly lower odds of postoperative atrial fibrillation compared to nitroglycerin (OR = 0.39, 95% CI: 0.18 to 0.85). In fact, the rank from highest to lowest rates of postoperative atrial fibrillation was placebo>nitroglycerin>diltiazem. The rank from highest to lowest odds of requiring inotropic support is nitroglycerin> diltiazem>placebo. However, placebo had significantly higher odds of postoperative myocardial infarction than diltiazem (OR = 4.51, 95% CI: 1.34 to 15.25). The rank from highest to lowest odds of postoperative myocardial infarction, transient cardiac ischemic event and atrial fibrillation is placebo>nitroglycerin>diltiazem.

Conclusion

Compared to nitroglycerin and placebo, perioperative continuous intravenous infusion of diltiazem had stronger protective effects against postoperative ischemic cardiac injuries and atrial fibrillation although patients may need more inotropic support. The increased blood flow from diltiazem use in arterial grafts may potentially contribute to the drug’s outcome benefits.

Sodium Nitroprusside as a Hyperinflation Drug and Therapeutic Alternatives

Sodium nitroprusside (SNP) is a generically available and rapid-acting intravenous (IV) vasodilator that has been used clinically for decades. Prior to 2013, the cost of SNP was relatively low, and SNP was an affordable option for the treatment of acute hypertension. However, from 2013 to 2017, average wholesale prices for SNP rose to as high as US$900 per vial, earning the drug its status as a "hyperinflation drug." Hyperinflation drugs pose a significant challenge for pharmacy departments. A multidisciplinary effort involving stakeholders from many backgrounds, including pharmacists, physicians, and nurses, is key to developing an effective cost containment strategy. A therapeutic interchange, wherein a drug with similar efficacy is substituted for another, is often an appropriate strategy to address rising drug costs. Fortunately, alternative drugs with a solid evidence base exist for the management of acute hypertension. The dihydropyridine calcium channel blockers, clevidipine and nicardipine, are IV titratable antihypertensive agents with favorable pharmacokinetic and safety profiles. Various studies indicate that clevidipine and nicardipine are effective alternatives to SNP for indications including hypertensive crisis and postoperative hypertension. Some hospitals have reported significant cost savings without adverse outcomes by substituting clevidipine or nicardipine for SNP. This article is intended to serve as a review of the evidence for clevidipine and nicardipine as potential substitutes for SNP and to provide strategies to successfully implement this therapeutic interchange.

Efficacy of prophylactic doses of intravenous nitroglycerin in preventing myocardial ischemia under general anesthesia: A systematic review and meta-analysis with trial sequential analysis

STUDY OBJECTIVE

To evaluate the efficacy of intravenous nitroglycerin (TNG) in preventing intraoperative myocardial ischemia (MI) under general anesthesia. Moreover, we analyzed the hemodynamic changes in heart rate (HR), mean blood pressure (MBP), and pulmonary capillary wedge pressure (PCWP) associated with TNG administration both before and after the induction of anesthesia.

DESIGN

Meta-analysis.

SETTING

Operating room, cardiac surgery or non-cardiac surgery, all surgeries were elective measurements. We performed a computerized search of articles on PubMed, Scopus, and the Cochrane Central Register of Controlled Trials. Meta-analysis was performed using Review Manager. The data from the individual trials were combined using a random-effects model to calculate either the pooled relative risk (RR) or the weighted mean difference (WMD) with 95% confidence interval (CI). We conducted trial sequential analysis (TSA). The primary outcome was the incidence of MI and the secondary outcomes were hemodynamic changes (HR, MBP, and PCWP).

MAIN RESULTS

Using electronic databases, we selected 10 trials with a total of 353 patients for our review. Prophylactic intravenous TNG did not significantly decrease the incidence of MI (RR=0.61; CI, 0.33 to 1.13; P=0.12; I²=55). TSA corrected the CI to 0.05 to 7.39 and showed that 9.5% of the required information size was achieved. In terms of hemodynamic changes, intravenous TNG significantly reduced MBP in comparison with the placebo (MBP pre-induction: WMD=-7.27; 95% CI -14.2 to -0.33; P=0.04; I²=97%; MBP post-induction: WMD=-5.13; 95% CI -9.17 to -1.09; P=0.01; I²=73%).

CONCLUSIONS

Our analyses showed that prophylactic intravenous TNG does not reduce the incidence of intraoperative MI. Moreover, TSA suggests that further studies are necessary to confirm the results (GRADE: very low). Prophylactic doses of intravenous TNG significantly reduced the MBP both pre and post anesthesia induction (GRADE: very low).

Clinical Features and Management of Selected Hypertensive Emergencies

A hypertensive emergency, defined as an elevated blood pressure with evidence of acute target organ damage, can manifest in many forms, including neurological, cardiac, renal, and obstetric. After diagnosis, effective parenteral antihypertensive therapy (typically, nitroprusside starting at 0.5 microg/kg/min, but some physicians prefer fenoldopam or nicardipine) should be given in the hospital. In general, blood pressure should be reduced about 10% during the first hour and another 15% gradually over 2-3 more hours. The exception is aortic dissection, for which treatment includes a b blocker, and the target is systolic blood pressure <120 mm Hg after 20 minutes. Oral antihypertensive therapy can usually be instituted after 6-12 hours of parenteral therapy. Consideration should be given to secondary causes of hypertension after transfer from the intensive care unit. Because of advances in antihypertensive therapy and management, "malignant hypertension" should be malignant no longer.

Nicardipine versus nitroprusside for deliberate hypotension during idiopathic scoliosis repair

STUDY OBJECTIVE

To compare coagulation, blood loss, and transfusion requirements between patients receiving nicardipine and nitroprusside for deliberate hypotension during idiopathic scoliosis repair.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PATIENTS

51 ASA physical status I patients presenting for spine fusion for idiopathic adolescent scoliosis.

INTERVENTIONS

Patients were randomized to two groups to receive nicardipine or nitroprusside to maintain mean arterial pressure (MAP) between 55 and 65 mmHg.

MEASUREMENTS

Blood loss, blood transfusions, and coagulation studies (thromboelastogram and platelet aggregation) before starting vasodilator, 30 minutes and 90 minutes after starting vasodilator, and 30 minutes after stopping vasodilator, were all recorded.

MAIN RESULTS

There was no difference between the groups in blood loss [nicardipine = 1,129 cc (893 to 1,480), nitroprusside = 960 cc (704 to 1,473)] and only one patient required a nonautologous transfusion. There were no differences in prothrombin time (pT, partial thromboplastin time (pTT), platelet count, or platelet aggregation between groups. There were more episodes of severe hypotension (MAP <45 mmHg) in the nitroprusside group (0% vs. 28%, p = 0.0175). On average, patients in the nicardipine group spent 21 minutes less in the recovery room than did the nitroprusside group (p = 0.043).

CONCLUSIONS

Nitroprusside's effect on platelet aggregation produces no increase in blood loss compared with nicardipine. Nicardipine causes less transient severe hypotension than nitroprusside, although both drugs are acceptable choices for obtaining the goals of deliberate hypotension.

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.

Midterm results of complete arterial revascularization in more than 1,000 patients using an internal thoracic artery/radial artery T graft

OBJECTIVE

To report the authors' 7-year experience with the internal thoracic artery/radial artery (ITA/RA) T graft as the only conduits for myocardial revascularization in two- and three-vessel disease.

SUMMARY BACKGROUND DATA

One and two arterial conduits provide increasing survival benefit for coronary grafting and reduce the need for reintervention. Exclusive use of arterial conduits may provide further benefit.

METHODS

From October 1993 to November 2000, 1,020 patients underwent complete arterial revascularization with the ITA/RA T graft. The authors focus on the 909 having initial bypass, with a mean age of 60 and 20% age 70 or older. The incidence of triple-vessel disease was 73%, female gender 28%, diabetes mellitus 27%, peripheral vascular disease 11%, cerebrovascular disease 10%, and chronic obstructive pulmonary disease 6%; ejection fraction was less than 35% in 11%. Perioperative data were collected prospectively. Follow-up information was obtained at a mean of 35.4 months (range 1-88) and was 95% complete.

RESULTS

There were seven (0.08%) deaths within 30 days of surgery. The incidence of perioperative infarction was 3.3%, low cardiac output 2.7%, stroke 2.2%, reoperation for bleeding 3.8%, and deep sternal infection 0.8%. The actuarial survival rate was 90% at 5 years, freedom from infarction was 94%, freedom from catheterization was 83%, and freedom from reintervention (angioplasty or reoperation) was 93%.

CONCLUSION

The ITA/RA T graft for complete arterial revascularization is associated with a low rate of perioperative death and complications and 5-year survival and freedom from reintervention values consistent with other revascularization strategies.

Occurrence of myocardial ischemia immediately after coronary revascularization using radial arterial conduits

OBJECTIVE

To assess the incidence of myocardial ischemia in patients receiving radial arterial and left internal thoracic arterial conduits (RA+LITA) during the postrevascularization period.

DESIGN

Nonrandomized observational sequential cohort.

SETTING

University hospital.

PARTICIPANTS

Thirty adult patients, scheduled for elective coronary artery bypass graft surgery with RA+LITA, compared with 30 patients who received saphenous vein graft and left internal thoracic arterial conduits.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Myocardial ischemic episodes were defined as reversible ST-segment depressions or elevations >or=1 mm and >or=2 mm at J +60 msec and lasting >or=1 minute using 2-channel Holter monitoring. During the post-cardiopulmonary bypass period, a significantly higher number of patients with >or=2 mm ischemic episodes (21.7%; p = 0.015) and higher number of >or=2 mm ischemic episodes per hour (0.19 +/- 0.4 episodes/hr; p = 0.03) were observed in the radial artery group versus the comparison group (0% of patients and 0 episodes/hr). During the postoperative period (24 hours), a significantly longer duration of >or=2 mm ischemic episodes was observed in the radial artery group (24 +/- 33 minutes v 8.4 +/- 21 minutes; p = 0.046). Radial artery graft, preoperative calcium antagonists, and pulmonary arterial mean pressure were independent predictors of the duration and area under the ST-segment curve of >or=2 mm ischemic episodes during the postoperative period.

CONCLUSION

There is an association between the use of the radial artery graft and the incidence and severity of >or=2 mm postrevascularization ischemic episodes.

Nicardipine versus nitroprusside for breakthrough hypertension following carotid endarterectomy

STUDY OBJECTIVE

To evaluate the effectiveness of nicardipine and nitroprusside for breakthrough hypertension following carotid endarterectomy.

DESIGN

Prospective, randomized, double-blind, controlled effectiveness trial.

SETTING

University-based surgical intensive care unit.

PATIENTS

60 ASA physical status I, II, III, and IV patients experiencing breakthrough hypertension at the time of admission to the intensive care unit (ICU).

INTERVENTIONS

Patients received either nicardipine (n = 29) and placebo or nitroprusside (n = 31) and placebo for up to 6 hours postoperatively. Loading doses of nicardipine were provided, but placebo was used as a load for patients randomized to nitroprusside.

MEASUREMENTS AND MAIN RESULTS

Rapidity and variability of blood pressure (BP) control were assessed. During the first 10 minutes, 83% of nicardipine patients compared to 23% of nitroprusside-treated patients, achieved BP control (p < 0.01). Following initial control, 12 nicardipine- and 24 nitroprusside-treated patients required additional titration of their infusions to maintain blood pressure within the targeted range (p < 0.05). No patient suffered a stroke, myocardial infarction, or was returned to the operating room (OR) for bleeding.

CONCLUSIONS

Nicardipine administration produced more rapid BP control, most likely related to the administration of a loading dose. In addition to more rapid control, nicardipine-treated patients had less variability in BP and required significantly fewer additional interventions. Although no patient suffered a major event during this study, this study was not powered sufficiently to assess safety.

Prophylactic nitroglycerin did not reduce myocardial ischemia during accelerated recovery management of coronary artery bypass graft surgery patients

OBJECTIVE

To evaluate the use of a high dose of nitroglycerin (NTG) for prophylaxis against myocardial ischemia and infarction in patients undergoing coronary artery bypass graft (CABG) surgery with accelerated recovery.

DESIGN

Prospective, double-blind, placebo-controlled randomized study.

SETTING

A university-based medical center.

PARTICIPANTS

Forty adult patients presenting for elective CABG surgery.

INTERVENTIONS

Forty patients were divided into 2 blinded study groups. Twenty patients received 2 microg/kg/min of NTG starting before induction of anesthesia and continuing for 6 hours after extubation in the intensive care unit. The placebo group (n = 20) received normal saline during this same interval.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, incidence and severity of myocardial ischemia, and myocardial infarction rates were determined. There were no differences in hemodynamic parameters between groups. The incidence of ischemia was approximately 35% in each group. Myocardial infarction (as determined by elevated creatine kinase-MB fraction, troponin I, and electrocardiogram criteria) was 10% in the placebo group and 5% in the NTG group (p = 0.234).

CONCLUSIONS

This study shows a high incidence of myocardial ischemia and infarction in patients presenting for CABG surgery with an accelerated recovery management scheme. NTG was well tolerated clinically; however, it was not found to be protective against myocardial ischemia or infarction in this setting.