***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Atrial fibrillation is a frequently occurring arrhythmia after thoracic operations . Preventive strategies for this complication have been extensively evaluated after cardiac operations . METHODS We performed a prospect i ve , open r and omized study , comparing intravenous verapamil and placebo in 199 patients after pneumonectomy or lobectomy at the University Hospital of Leuven .  Verapamil was administered as a bolus of 10 mg over 2 minutes followed by a 30-minute infusion of 0.375 mg/min and then 0.125 mg/min for 3 days . The patients were continuously monitored in the postoperative intensive care unit . RESULTS Atrial fibrillation occurred in 15 % of the patients receiving placebo and in 8 % of the patients receiving verapamil ( difference not significant ) . The verapamil infusion was interrupted in 9 % of the patients because of bradycardia and in 14 % because of hypotension . CONCLUSIONS If tolerated , continuous intravenous verapamil infusion showed only a modest prophylactic efficacy for the occurrence of atrial fibrillation after lung operations . In the dose employed the verapamil infusion was accompanied with a high incidence of side effects necessitating interruption of the therapy We have studied the effect of verapamil on the incidence of ECG changes and right ventricular pressures ( RVP ) in 25 male patients ( aged 62 ( SD 9 ) yr ) undergoing thoracotomy in a  placebo-controlled double-blind trial . Verapamil 0.01 mg kg-1 h-1 ( n = 12 ) or saline ( n = 13 ) i.v . was started after surgery and continued on the first day after operation with oral verapamil 80 mg or placebo , 8-hourly . Haemodynamic data were collected before operation and on three days after operation with the patients breathing air and then 60 % oxygen ( FIO2 0.60 ) for 10 min . Atrial tachyarrhythmia ( AT ) ( 4/13 ) and new ischaemic ECG changes ( 3/13 ) occurred only in the control group ( P less than 0.05 ) . With an FI02 of 0.21 , systolic RVP increased by 54 % on the first two days after operation in the control group and by 13 % in the verapamil group ( P less than 0.02 ) . With an FIO2 of 0.60 for 10 min , systolic RVP decreased more in the control than in the verapamil group ( P less than 0.01 ) . In the control group , an increase in end-diastolic RVP ( P less than 0.001 ) and central venous pressure ( P less than 0.05 ) on the first day after operation was predictive of AT occurring on the second day OBJECTIVE The aim of this study was to assess the efficacy and safety of intravenous diltiazem to prevent myocardial ischemia during surgery on patients with ischemic heart disease undergoing non cardiac surgery under general anesthesia . PATIENTS AND METHOD Sixty patients scheduled for elective non cardiac surgery under general anesthesia were r and omly assigned to two groups to receive diltiazem or placebo under double blind conditions . After an intravenous dose of 0.15 mg/kg of diltiazem or an equivalent amount of placebo , an infusion of 3 micrograms/kg/min of diltiazem or placebo was begun and continued until three hours after surgery . Thirty minutes after starting the infusion , anesthesia was induced by 0.1 mg/kg diazepam , 3 micrograms/kg of fentanyl and 0.3 mg/kg of etomi date . Intubation followed administration of 0.6 mg/kg of atracurium . Anesthesia was maintained with N2O/O2 and halothane and was the same for both groups . DII and V5 leads were monitored on a Cardiowiss CM-8 ECG machine that allowed us to set the alarm when ST segment variations reached 1 mm above or below baseline . We analyzed the number , intensity and duration of ischemic episodes recorded , as well as hemodynamic variables and side effects . RESULTS Data for 46 patients were valid . At least one ischemic episode was experienced by 15 % of patients in the placebo group and 1 in the diltiazem group ( p < 0.05 ) . The episodes were related to increased systolic arterial pressure ( p = 0.04 ) . ST segment decreases were 1.1 to 3.6 mm ( 1.75 + /- 0.7 ) ( mean + /- SD ) and lasted between 1 and 45 minutes ( 11.62 + /- 13.26 ) ( mean + /- SD ) . No significant side effects were observed . CONCLUSIONS Intravenous diltiazem administered to patients with ischemic heart disease under general anesthesia for non cardiac surgery was effective in our study for preventing intraoperative ischemic episodes OBJECTIVES Observational studies have question ed the effectiveness of perioperative calcium channel blockers but failed to correct for selection biases . We therefore performed a prospect i ve observational cohort study of the effects of calcium channel blockers on cardiac surgical  mortality . A propensity score technique was used for risk adjustment . METHODS We identified 6619 patients who underwent nontransplant cardiac surgery at the Toronto General Hospital ( Toronto , Ontario , Canada ) between May 1999 and December 2001 . Propensity scores for calcium channel blocker use were constructed for the entire sample and for the subgroup ( n = 5222 ) that underwent coronary artery bypass grafting . The calcium channel blocker adjusted odds ratio for in-hospital mortality after cardiac surgery was determined by using multiple logistic regression and propensity matched-pairs analyses . A subgroup analysis was performed for patients who underwent coronary artery bypass grafting :  the calcium channel blocker adjusted odds ratio for mortality was determined by using propensity score matched-pairs analyses . RESULTS Calcium channel blockers were associated with significantly reduced cardiac surgical mortality after adjustment with both multiple logistic regression ( odds ratio , 0.56 ; 95 % confidence interval , 0.33 - 0.94 ; P = .028 ) and propensity score matched-pairs analyses ( odds ratio , 0.56 ; 95 % confidence interval , 0.32 - 0.98 ; P = .042 ) . Calcium channel blockers were also associated with reduced mortality ( odds ratio , 0.48 ; 95 % confidence interval , 0.23 - 0.98 ; P = .044 ) among patients who underwent coronary artery bypass grafting . CONCLUSIONS After adjustment for baseline differences , calcium channel blockers were associated with significantly reduced mortality after cardiac surgery . This benefit also extends to the subgroup that underwent coronary artery bypass grafting . A large r and omized controlled trial of perioperative calcium channel blockers is therefore warranted This double-blind r and omized trial assessed the effect of adding an intravenous continuous infusion of ketorolac to a patient-controlled analgesia ( PCA ) morphine regimen on analgesia , heart rate , arterial blood pressure , and postoperative myocardial ischemia .  Patients having elective total hip or knee replacement were r and omized to receive ketorolac 30 mg bolus , followed by an infusion of 5 mg/h for 24 h or placebo . All patients had access to PCA morphine ( 20 micro g/kg bolus , with a lockout of 6 min ) . Patients were monitored for pain visual analog scale , blood pressure , heart rate , and ST segment depression via a continuous Holter monitor . ST depression of 1 mm 60 ms after the J point was considered significant if it lasted more than 1 min . There was no difference in demographics , risk factors , or cardiac medications between the groups . Ketorolac-treated patients had significantly better pain control at 2 , 6 , and 24 h. There was significant  morphine  sparing at all times after 3 h. There was no difference in the number of ischemic events between the groups . The ischemic episodes of the patients who received ketorolac occurred at slower heart rates ( 97 + /- 15 vs 114 + /- 16 bpm , P = 0.001 ) than those of patients in the placebo group . The duration of ST depression was shorter in ketorolac-treated patients ( 24 + /- 35 vs 76 + /- 95 min , P < 0.05 ) . All ST depressions were clinical ly silent . Logistic regression of factors predicting ischemia included the use of calcium channel blockers and low pain score . These results suggest that analgesia with ketorolac reduces the duration of ischemic episodes in the first 24 h postoperatively . ( Anesth Analg 1997;84:715 - 22 A double-blind study was performed on 50 elderly patients undergoing hip-replacement surgery under general anaesthesia ; 26 were given  nifedipine  and the remaining 24 placebo to determine effects on the continuously monitored ( Holter ) ECG during the 4 peri-operative days . Drugs were only administered during the latter 3 days of the observation period . Surgery was performed on the morning of the 3rd day . A striking feature was the high incidence of arrhythmias in both groups of patients , a finding previously documented in both ' normal ' and elderly people . A decrease in ST-segment changes was expected in the nifedipine-treated patients . An unexpected finding , therefore , was the lack of protection against cardiac ischaemic changes in the nifedipine-treated patients compared with the placebo patients . Interpretation of the ST segment as seen in the Holter-monitored ECG remains controversial . We have no clear explanation for the lack of protection against ischaemic changes . The effects of profound vasodilatation produced by nifedipine in elderly patients subjected to major surgery , general anaesthesia including administration of enflurane , and a variable amount of blood loss in the postoperative period may be important factors . In conclusion , one should perhaps be cautious of nifedipine administration under these circumstances Supraventricular arrhythmia after noncardiac surgery is common [ 1 , 2 ] . Much of the data on the epidemiology and consequences of perioperative supraventricular arrhythmia in patients undergoing noncardiac surgery were collected before recent advances in anesthetic and monitoring techniques were made [ 3 ] . This clinical syndrome may have been influenced by such trends as the aging of the general population and the increased use of -blockers and calcium-channel blockers . To test the hypothesis that supraventricular arrhythmia remains a frequent event that is associated with major adverse outcomes after surgery , we studied a consecutive sample of 4181 patients who underwent major , nonemergency , noncardiac procedures and were in sinus rhythm at the preoperative evaluation . Our findings provide insight into the contemporary epidemiology and natural history of perioperative supraventricular arrhythmia . Methods Patients All patients 50 years of age or older who underwent major , nonemergency , noncardiac procedures at Brigham and Women 's Hospital , Boston , Massachusetts , from 18 July 1989 to 28 February 1994 were eligible for the study . Major noncardiac procedures were defined as those associated with an expected length of stay of 2 or more days . Procedures were electively scheduled or were done during inpatient admissions . The Brigham and Women 's Hospital Human Research Committee approved the enrollment and clinical data collection protocol s. Patients were included in this analysis if they were in sinus rhythm at the preoperative evaluation . Of the 4315 consecutive patients enrolled in the overall study , 4181 ( 97 % ) met this criterion and constituted the study sample for this analysis . Data Collection The data collection protocol is described elsewhere ( [ 4 ] ; Lee TH , Marcantonio ER , Mangione CM , Thomas EJ , Cook EF , Sugarbaker DJ , et al. Derivation and prospect i ve validation of a simple index for prediction of cardiac risk of major noncardiac surgery . In preparation ) . In brief , patients who provided informed consent for the full study protocol had preoperative evaluations done by study personnel , who used a structured data form . These evaluations included detailed medical histories , physical examinations , and laboratory testing . Intraoperative data were obtained from anesthesia flow sheets and surgeons ' notes . For patients who did not have this evaluation because they could not be approached or because they refused to participate in the interview portion of the study , clinical data were obtained from the structured evaluation performed by the anesthesiologist noted in the medical record . This data source was also used to obtain American Society of Anesthesiologists ( ASA ) classifications for all patients . Consenting patients agreed to postoperative sampling of creatine kinase . If total creatine kinase levels were elevated , creatine kinase-MB levels were measured immediately after surgery , at 8 p.m. on the evening of surgery , and on the next two mornings . For other enrolled patients , creatine kinase-MB testing was done according to the physician 's orders . Electrocardiography was performed in the recovery room and 1 , 3 , and 5 days after surgery if the patient remained hospitalized . Study personnel review ed charts daily for the occurrence of complications . Classification of Outcome The perioperative period was divided into two parts : the intraoperative period , which ended at the patient 's departure from the operating room , and the postoperative period . A perioperative supraventricular arrhythmia was diagnosed whenever a patient was noted by his or her physicians or by the study 's research personnel to have new onset of atrial fibrillation , atrial flutter , paroxysmal atrial tachycardia , multifocal atrial t 
    Output:
    
In subgroup analyses , diltiazem significantly reduced ischemia , SVT , death/MI , and MMEs .
This meta- analysis shows CCBs significantly reduced ischemia , SVT , and combined end-points in the setting of noncardiac surgery .