Tobacco smoking, high body mass index and the outcome after surgery : the role of intervention

Abstract

The negative effects of smoking and obesity on public health are well-known. Despite this knowledge, the smoking-attributable morbidity and mortality is estimated to rise rapidly in the forthcoming years, and obesity has become an emerging worldwide epidemic. In the field of surgery, smokers and the obese constitute important risk groups, prone to develop postoperative complications, ranging from impaired wound healing to deadly cardiovascular and pulmonary events. Abstinence is known to halt the negative effects of smoking. However, the effect of preoperative smoking cessation on postoperative outcomes has only been investigated in a few randomised clinical trials, with differing results. Therefore, the efficacy remains uncertain. Similarly, interventions to reduce weight exist, but the effect of weight reduction on the outcome after planned surgery has not been investigated. The main focus of this thesis was to study the effect of preoperative smoking cessation on the risk of postoperative complications. A secondary aim was to shed light on the magnitude of impact that obesity has on the development of postoperative complications in elective surgery.

Using the large nation-wide Swedish Construction Workers Cohort, the effect of smoking on the risk of postoperative complications in patients undergoing elective total hip replacement (THR) or open appendectomy (OA) was evaluated. By record linkage, 3,309 male construction workers, who underwent THR between 1971 and 2002, were identified. After controlling for confounders, heavy smoking (>40 pack-years) increased the risk of systemic complications by 121% (Odds ratio (OR) =2.21, 95% Confidence Interval [CI]: 1.28 - 3.82) compared to never-smoking. Being obese (≥30 kg/m2) increased this risk by 58% (OR=1.58, 95% CI: 1.06 - 2.35) compared to those of normal weight (18.0-24.9 kg/m2) and also prolonged hospital stay. Neither smoking nor obesity was significantly associated with increased risk of local complications.

There was no effect of smoking on the risk of implant dislocation up to eight years after THR. However, high weight increased the risk of implant dislocation within three years after surgery. Overweight (BMI ≥25 kg/m2) increased this risk by 150% (Hazard ratio (HR) = 2.5, 95% CI: 1.1 - 5.5) and obesity increased this risk by 270% (HR = 3.7, 95% CI: 1.5 - 9.3) compared to those of normal weight.

By record linkage, 6,676 male construction workers who underwent OA for acute appendicitis between 1971 and 2004 were identified. Current smokers with more than 10 pack-years of smoking had 29% (RR= 1.29; 95 % CI: 1.11 - 1.50) increased risk of perforated appendicitis (PA) compared to never-smokers. Moreover, in patients with non-perforated appendicitis, current smoking with more than 10 pack-years (RR= 1.51; 95% CI: 1.03 - 2.22) and obesity (RR=2.60; 95% CI: 1.71 - 3.95) were significantly associated with increased risk of overall complications compared to never-smokers and those of normal weight, respectively. There was no significant association between obesity, smoking and overall complications in patients with PA. This was probably due to the high baseline complication frequency, which reduced the risk difference between the subgroups.

In a smoking cessation intervention, 117 patients undergoing elective orthopaedic and general surgery were randomised to intervention (N=55) or control (N=62). Between March 2004 and December 2006, 102 patients, 48 in the intervention group and 52 in control group completed the trial. The intervention group underwent an intensive smoking cessation programme, on average 4 (2 - 7) weeks before surgery, with weekly meetings or phone calls, and was provided with free nicotine replacement therapy. The control group received standard care. According to intention to treat analysis, the risk of postoperative complications was reduced from 30/62 (48%) in the control group to 17/55 (31%) in the intervention group, resulting in a 37% (RR=0.63, 95% CI: 0.40 - 1.02) relative risk reduction. Based on this clinical effect, it was concluded that preoperative smoking cessation, initiated as late as four weeks before surgery, could efficiently be used to reduce the risk of postoperative complications after elective orthopaedic and general surgery.