Patients with or at risk for heart disease who take the anti-hypertensive drug clonidine before non-cardiac surgery can significantly reduce the risk of complications and death due to inadequate blood flow to the heart, according to a study by UCSF researchers at the San Francisco Veterans Affairs Medical Center.
The findings add a second drug to the list of inexpensive preventive measures available to these patients before non-cardiac surgery. In 1998 the same UCSF/SFVAMC researchers identified the beta blocker atenolol as an effective preventive measure for this patient group. The clonidine research is reported in the August 2004 issue of the journal Anesthesiology.
"In the earlier study we found an inexpensive way to reduce the incidence of death due to surgery. Now we have found another drug to do the same thing," said lead researcher Dr. Arthur Wallace, UCSF associate professor of anesthesia and perioperative care and staff anesthesiologist at the SFVAMC.
The clonidine study focused on 190 male patients scheduled to undergo non-cardiac surgery who had been diagnosed with coronary artery disease or had at least two of five risk factors for cardiac disease: age 60 or older, hypertension, smoking within a year, cholesterol of 240 or greater or diabetes. Scheduled surgeries included orthopedic, head and neck, abdominal and others.
Of the patients, 125 received a .2 mg oral tablet of clonidine the night before surgery, a transdermal patch of clonidine the night before surgery and a .2 mg tablet one hour before surgery. A control group of 65 received placebos. After follow-ups of three days, 14 days, 30 days and two years, the clonidine group showed a death rate of 1 percent compared to 6 percent for the placebo group. After two years, the death rate of the clonidine group was 15 percent compared to 29 percent for the placebo group.
Patients were monitored for episodes of blocked blood flow using Holter electrocardiogram recorders--before, on the day of, and up to seven days after surgery. They also received electrocardiograms to measure the heartbeat every day for the first seven days after surgery and whenever necessary due to shortness of breath, chest pain or loss of consciousness. Blood pressure was recorded continuously from one hour before surgery to one hour following surgery, and blood samples were analyzed for presence of heart enzymes and clonidine concentrations.
Researchers found that patients who had received clonidine showed no evidence of myocardial ischemiac events (inadequate blood flow to the heart) before surgery compared to 5 percent for those who had received placebos.
On the day of surgery and up to three days after surgery only 14 percent of clonidine patients experienced such events, compared to 31 percent for placebo patients. After 30 days, one (.8 percent) of the clonidine patients had died compared to four (6.2 percent) of placebo patients. In a two-year follow up, 19 (15 percent) of the clonidine group had died compared to 19 (29 percent) of the placebo group.