Chronic substance use may influence outcomes in patients with cardiovascular disease. The prevalence and intensity of substance use varies widely in different countries and populations. There have been reports regarding patterns of substance use in Western countries; however, only limited information is available on this issue in the Iranian population. Ahmadi and Benrazavi1 conducted a study on the prevalence of substance use in Iranian patients with cardiovascular disease. They found the prevalence of cigarette smoking, opium use, and alcohol consumption to be 36.5%, 9.4%, and 8.3%, respectively. In another study by the same authors but in patients with renal pathology, they reported a prevalence of 35.5%, 14.0%, and 3.0% for the aforementioned substances.2 There are some reports that support the adverse effects of cigarette smoking; however, in cardiac surgery patients, there is not an obvious and clearly established relationship between chronic opium abuse or moderate alcohol consumption and an increase in early (in-hospital) postoperative morbidity and mortality. The aim of this study was to investigate the prevalence of substance use and its effects on postoperative morbidity and mortality among patients undergoing cardiac surgery in northwest Iran.
After obtaining IRB and ethics committee approval, written informed consent was obtained from the patients. We interviewed 600 adult (>18 yr) patients scheduled for elective coronary artery bypass graft (CABG) and cardiac valve surgery in a referral educational hospital in northwest Iran between July 2007 and October 2008. A structured questionnaire that included DSM-IV criteria (Appendix) for substance use and dependence was used.3 An individual was considered dependent if within a 12-mo period, repeated difficulties occurred in any 3 areas of functioning, including tolerance, withdrawal, use of larger amounts of opiates than intended, and continued use despite negative consequences. Patients who were not dependent but demonstrated repeated difficulties with the law, impaired ability to meet obligations, substance use in hazardous situations, or continued use despite negative consequences were considered abusers.4
Exclusion criteria included patients receiving mechanical ventilation, those with altered mental status, language barrier, and those unable to understand the study protocol. The intraoperative anesthetic technique and the postoperative sedation, analgesia, and intensive care unit (ICU) discharge protocols were similar in all patients.
Smoking status was categorized as nonsmoker, ex-smoker, and current smoker. Patients who had quit smoking within 8 wk of surgery were considered current smokers.3 Opium and alcohol use was divided into nonuser, abuser, and dependent.
Postoperative morbidity, length of ICU stay, length of hospital stay, and in-hospital mortality were compared between substance abusers and nonusers. There were 340 nonusers (nonsmokers, nonopium users, and nondrinkers) who were considered the control group. Postoperative complications included cardiac, pulmonary, and neurologic complications. Cardiac complications were defined as life-threatening arrhythmias; severe hemodynamic disturbances (variation in mean arterial blood pressure more than 30% from the baseline value measured by an indwelling arterial catheter); myocardial infarction, diagnosed by electrocardiographic criteria and by an increase of cardiac troponin I and myocardial creatine kinase-MB isoenzyme levels more than 5 times the upper limit of normal; use of 2 or more inotropes intraoperatively; and intraoperative need for intraaortic balloon pump. Respiratory complications were defined as pneumothorax (requiring chest tube placed urgently in the ICU), severe atelectasis, pneumonia, acute respiratory distress syndrome, and acute lung injury. Neurologic complications included delirium, agitation, dementia, coma, hallucinations, convulsions, depression, and cerebrovascular accident. In-hospital mortality included all postcardiac surgery deaths occurring within the same admission.
Collected data were analyzed with SPSS v.16.0 (SPSS, Chicago, IL) statistical package. Continuous variables were expressed as means and sd and were compared using one-way analysis of variance. Continuous variables with skewed distribution (not meeting normal distribution) were analyzed by Kruskal-Wallis H test. Categorical variables were analyzed by χ2 test. A P value of 0.05 or less was considered statistically significant.
Six hundred patients were included in the study. There were 404 (67.3%) males and 196 (32.7%) females. The mean age was 55.2 ± 13.3 yr (range 18–83 yr). Substance use (one or more substances, once or more in a lifetime) was reported by 43.6% of patients, which included 60.6% of males and only 8.6% of females. Patients' demographic and preoperative characteristics are summarized in Table 1. Each substance use was considered separately.
Forty-two percent of all patients smoked cigarettes (58.9% of males and 7.6% of females). Considering all categories, 97 patients (16.1%) were current smokers, whereas 156 (26.0%) were ex-smokers and 347 (57.9%) were nonsmokers. The incidence of hypertension and diabetes mellitus (DM) was lower among current smokers than in the other 2 groups (P = 0.045 and P = 0.006, respectively). The mean weight and height were lowest in the nonsmokers (mostly women). The mean left ventricular ejection fraction was lower in smokers than in nonsmokers (Table 1). Mean pack-years of smoking was 25.7 ± 18 yr.
The incidence of opium abuse and dependence (as defined by DSM-IV criteria) was 42 of 600 (7.0%) and 30 of 600 (5.0%), respectively. In our study, all drug dependents and abusers had only used opium, and there were no reports of any other drug use (i.e., heroin or cocaine). Inhalation was the most common route of use (63.7%), followed by oral (36.3%); there were no cases of IV opium use. Fifty-three percent (16 of 30) of opium dependents and 69% (29 of 42) of opium abusers inhaled the drug. In total, 70 men (11.7%) and 2 women (0.3%) were current users or had a history of opium use. There were no statistically significant differences in frequency of hypertension, DM, and low ejection fraction between opium users and nonusers. The mean weight and height were lower in nonusers (Table 1). Intraoperatively, opium-dependent patients received upper limits of routine doses of opioids for maintenance of anesthesia. With the exception of 2 patients, all opium-dependent patients requested their oral opium doses during their ICU stay.
The incidence of alcohol consumption was 8.1% (49 of 600), which was only found in males, and included alcohol abuse in 45 (7.5%) and dependence in 4 patients (0.6%). None of those with dependence had DM; however, compared with nonusers, the incidence of DM was significantly lower in alcohol users (Table 1).
In this study, there were no patients who had a mixed dependence of all 3 substances (cigarettes, opium, and alcohol) simultaneously, but 12 patients (2%) reported having used all 3 substances in the past. Forty-three patients (7.1%) had smoked cigarettes and also had abused opium, and 25 patients (4.2%) had smoked cigarettes and consumed alcohol simultaneously. There were 340 nonusers (nonsmokers, nonopium users, and nondrinkers) who were considered the control group for comparing postoperative morbidity and in-hospital mortality with the substance abusers group (Tables 2–4).
Morbidity and Mortality
In-hospital mortality and early postoperative morbidity in each group are summarized in Tables 2–4. The frequency of cardiac complications was 21 of 97 (21.6%) in current smokers, 32 of 156 (20.5%) in ex-smokers, and 96 of 340 (28.2%) in nonsubstance users, with no statistically significant difference among groups. With respect to smoking status, there were no statistically significant differences in the frequency of respiratory complications (24.7%, 17.9%, and 26.8% in current smokers, ex-smokers, and control group, respectively). Cardiac complications occurred in 8 of 30 of opium dependents (26.6%), 7 of 42 of opium abusers (16.6%), and 96 of 340 of nonsubstance users (28.2%) (P = 0.310). There was no statistically significant difference in the frequency of respiratory complications; these were 5 of 30 in opium dependents (13.3%), 9 of 42 in opium abusers (21.4%), and 91 of 340 in nonusers (26.8%). In general, cigarette smoking, use of opium, and alcohol consumption had no statistically significant effects on the rate of early postoperative complications or death in this patient population (Tables 2–4).
The majority of our patients (475 of 600; 79.2%) underwent CABG surgery and only 96 patients (16%) underwent valvular repairs (aortic, mitral, and tricuspid). The type of operation did not affect the incidence of postoperative complications.
We also compared morbidity and mortality rates in men among current smoker, ex-smoker, and substance nonuser subgroups. The postoperative respiratory complication rate was statistically significantly higher in current smokers [29 of 92 (31.5%)] than in ex-smokers [24 of 146 (16.4%)] and nonsmokers [30 of 161 (18.6%)]. Although the in-hospital mortality rate was higher in current smokers (4 of 92; 4.3%) than ex-smokers (3 of 146; 2.1%) and substance nonusers (4 of 161; 2.5%), this difference did not reach statistical significance. Also, in males, there were no statistically significant differences in morbidity and mortality rates among opium dependents, abusers, and substance nonusers (control group in men).
In this study, the prevalence of substance use was high in cardiac surgery patients, especially in males. Cigarette smoking was the most prevalent (42.1%) form of substance use among cardiac surgery patients referred to our hospital in northwest Iran. Opium use was not uncommon (12.0%) in these patients, but alcohol consumption was infrequent (8.1%). With the exception of postoperative pulmonary complications, which were higher in active smoker men, abuse of cigarettes, opium, and alcohol had no apparent effect on early postoperative complications and in-hospital mortality rate in our patients.
Prevalence of Substance Use
Reports indicate that the frequency of substance use varies greatly in different populations.5,6 The prevalence of cigarette smoking in patients undergoing surgery as reported by Ahmadi and Benrazavi7 in 2002 was 38.5%. The incidence of cigarette smoking in Iranian men and women is reported to be 26% and 3.8%, respectively.1 This is much less than what is reported from the neighboring country, Turkey, where it is reported that 59.4% of males and 18.9% of females smoke cigarettes.* Kasliwal et al.5 in 2006 reported the prevalence of smoking to be 39.6% (9.4% current and 30.2% ex-smokers) among Indian patients undergoing CABG (44.1% in males and 5.1% in females). In another study conducted by Utley et al.8 in 1996 in South Carolina, the prevalence of smoking among CABG patients was 37.5% (47.9% in men and 20.0% in women). Ashraf et al.6 in 2004 reported a high prevalence of smoking (75.5%) in CABG patients in Liverpool (UK); the majority, 60.6%, were ex-smokers and 14.9% were current smokers.
In our study, the frequency of cigarette smoking was 42.1% (58.9% in males and 7.6% in females). The prevalence of smoking in men in our study was similar to other published reports; however, women in our study smoked much less compared with other countries.
In Iran, the most frequently abused substance is opium (96.9%), whereas other drugs such as heroin and cocaine are used much less frequently. Inhalation is the most common route of self-administration (52.7%), followed by oral (45.0%) and injection (2.3%).† In our study, all of the drug dependents and abusers were using opium, and there were no cases of other drug use (i.e., heroin or cocaine). We observed that the route of opium abuse was similar to that reported by Abdollahi.† In 1978, the rate of opium dependence in northern Iran was reported to be 7.0%.9 More recent studies have shown a prevalence of 7.3% and 11.5% in general surgical and cardiac surgery patients, respectively.7† In 2003, Misra et al.10 reported that the national average of illicit drug use in the United States was 6.9%; it was 5.7% overall in the state of Louisiana, and 6.2% in patients undergoing CABG surgery. In contrast, the incidence of opium use in Australia was only 4.9%.11 In a United Nations world drug report from 2008, approximately 4.9% of people aged 15–64 yr had used drugs.‡ In our patients, opium use (12.0%) was about twice that reported from Western countries. This difference most likely can be explained by the long borders with Afghanistan, which is the largest source of cultivation and traffic of illicit drugs in the world.§
In our study, the incidence of alcohol consumption was 8.1% in cardiac surgery patients. Ahmadi and Benrazavi7 in 2002 showed the prevalence of alcohol use to be 9.4% in Iranian patients undergoing surgery. Attar et al. reported 9.6% (8.9% men and 0.7% women) of hospitalized patients in Iran were current alcohol users and 25.4% (22.8% men and 2.6% women) had a history of alcohol consumption.∥ As a comparison, the incidence of alcohol consumption in Australian automobile drivers was 29.1%.11
Mukamal et al.12,13 in 2 separate studies reported a frequency of alcohol consumption of 43.7% and 45.8% in patients undergoing CABG in Boston in 2006. We found less alcohol consumption in our patients in comparison with similar studies in Western countries. This may be attributable to religious and legal prohibition of alcohol consumption in Iran.
Effect of Substance Use on Outcome
Many studies have suggested a higher morbidity and mortality rate among smokers than nonsmokers after cardiac surgery.6,14,15 For example, Arabaci et al.14 in 2003 showed that smokers had a pulmonary complication rate almost twice that of nonsmokers. According to Al-Sarraf et al.,15 smoking increases the risk of postoperative pulmonary complications after CABG but does not affect the overall short-term mortality after the procedure. In contrast, Ashraf et al.6 reported that current smokers, but not ex-smokers, were more likely to develop respiratory complications than nonsmokers after CABG. Utley et al.8 showed no increase in postoperative pulmonary failure, myocardial infarction, renal failure, infection, and operative death in smokers in comparison with nonsmokers undergoing CABG. Our study showed more early postoperative pulmonary complications in men who smoke but not in women. However, this study revealed no statistically significant increase in cardiac complications and in-hospital mortality after cardiac surgery between smokers and nonsmokers.
Safaei16 reported that readmission for cardiovascular problems after CABG occurred significantly more often in opiate users than nonusers in Iran. Misra et al.10 showed that perioperative complications and death rates were not significantly different in opiate users and nonusers, but they suggested that current illicit drug use is a significant predictor of cardiovascular complications in the first 6 mo after CABG. Our study also showed no effect of chronic oral opium abuse or dependency on in-hospital morbidity and mortality after cardiac surgery.
Although the ingestion of a moderate amount of ethanol (3–9 drinks/wk) appears to be associated with a reduced risk of cardiovascular disease,12,17 the consumption of excessive amounts has deleterious effects on cardiovascular outcome.17,18 Shaper and Wannmethee17 reported that, compared with occasional drinking, regular alcohol consumption in men with established coronary heart disease was not associated with any significant benefit or deleterious effect for cardiovascular disease or all-cause mortality. Mukamal et al.12 showed no statistically significant difference between alcohol drinkers and nondrinkers in atherosclerotic progression in CABG after 5-yr follow-up. We did not find any difference in postoperative complications between alcohol users and nonusers. However, the number of alcoholic patients (49 of 600) in our study was likely too small to reach statistical significance.
We found that the rate of complications was similar between patients with substance abuse disorders and those without. One explanation could be the limited sample size (n = 600) in our study, in which 45 patients (7.4%) were abusing alcohol, and only 4 patients (0.7%) were alcohol dependent. Likewise, 42 patients (7.0%) were opium abusers, and 30 patients (5.0%) were opium dependent. The wide range of postoperative complications (6%–26%) in these small subgroups very likely is a reflection of the lack of statistical power necessary to detect significant differences (Tables 2–4).
Clearly, most of substance dependents and users in our setting were male (Table 1). We compared postoperative complications and in-hospital mortality rates in men among current smoker, ex-smoker, and substance nonuser subgroups. In men, the postoperative respiratory complication rate was statistically significantly higher in current smokers. The in-hospital mortality rate was somewhat higher in current smokers than ex-smokers and substance nonusers, but this difference was not statistically significant (P = 0.076). On the other hand, in-hospital mortality and perioperative morbidity after CABG has remained, on average, 2 times higher in women compared with men.19
In cardiac surgery patients in northwest Iran, the prevalence of cigarette smoking is relatively low (very low in women), as is alcohol use, compared with Western countries; however, opium use is twice as prevalent. Our study showed that cigarette smoking is a risk factor in increasing early postoperative pulmonary complications in cardiac surgery patients in men, but not in women. Additionally, opium use is not protective, nor is it a risk factor for short-term complications in these patients.
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APPENDIX: DATA COLLECTION QUESTIONNAIRE
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‡Reuters. FACTBOX-Key data from United Nation World Drug Report 2008. Available at: http://www.reuters.com/assets/ticker2. Accessed February 3, 2008.
§United Nations Office on Drugs and Crime. Available at: www.unode.org/unodc/en/data-and-analysis/WDR-2008.html. Accessed February 3, 2008.
∥Attar HR, Ebrahimi AA, Isfahani MN. Alcohol consumption in Iranian hospitalized Patients. Andeesheh va Raftar 2004;10:122–9.