Cut it out sooner than later

1 June 2014

Heading into surgery, does it make much difference if you delay quitting smoking just another week…

CLINICAL BOTTOMLINE:

Quitting more than four weeks before surgery more than halves the risk of complications. Quitting less than four weeks before surgery does not reduce complications.

CLINICAL SCENARIO:

You need to determine what advice is given to patients about quitting smoking before surgery – a key question is when to set the quit date before surgery.

QUESTION:

Among adults having surgery, does pre-operative smoking cessation reduce the risk of complications compared with not quitting?

SEARCH STRATEGY:

PubMed clinical queries (broad): smoking cessation AND post-operative.

CITATION:

Mills E, Eyawo O, Lockhart I, et al. Smoking cessation reduces postoperative complications: a systematic review and meta-analysis, Am J Med 2011;124:144-54.

STUDY SUMMARY:

Systematic review of trials and observational studies testing the effect of smoking cessation on post-operative complications. Inclusion criteria were:

type of study was randomised controlled trials and observational studies; patients were not clearly specified, but could be assumed to be patients undergoing any type of surgery;

intervention was not clearly defined but could be assumed to be smoking cessation;

outcomes end included total complications (primary outcome) and any wound healing, pulmonary or respiratory complications, all-cause mortality, and all cause length of hospital stay (secondary outcomes).

If a study reported a distinct type (or types) of complications, but not total complications, the distinct types were not combined for the systematic review. 847 titles were screened, 75 were retrieved for further review trials, and 30 studies included. Six studies were randomised controlled trials, which are the focus of this critical appraisal tool (CAT) article.

VALIDITY:

The search strategy was specified and involved electronic searches of databases including Medline, EMBASE, Cochrane CENTRAL, AMED, CINAHL, TOXNET, and the Web of Science. No language, sex, or age restrictions applied. Also searched were bibliographies of previous reviews and health technology assessments as well as databases of full text journals – e.g. Science Direct and Ingenta . The researchers used modified Cochrane risk of bias tool and included assessment of randomisation sequence generation, allocation concealment, blinding, intention-to-treat, descriptions of loss to follow up, and sources of funding. Data entered by the two researchers into electronic form and where data differed, differences were resolved by discussion and third party arbitration. Publication bias was not examined. Reasonably high quality review of moderate quality studies.

RESULTS:

Six trials involving 552 participants were included covering patients that received hernia repairs, laporoscopic cholecystectomies, joint replacements, colorectal, urologic, ORL, or gynaecological surgery. Most trials involved the evaluation of a smoking cessation intervention several weeks prior to surgery. One trial compared buproprion with placebo and one trial compared nicotine patch applied on day of surgery. Four trials reported sequence generation and allocation concealment; five trials were blinded; all trials used intention-to-treat analysis and one trial had greater than 20 per cent loss to follow up. All trials were funded publicly with pharmac providing the drugs. Smoking cessation almost halved total complication rates (table), shorter term cessation (< 4 weeks) and less intensive interventions are less effective than longer term cessation (> 4 weeks) and more intensive intervention.

 

Table. Results with 95% confidence intervals (95%CI).

 Outcome

N

RR (95%CI)

Heterogeneity

 Total complications

552

0.59 (0.41 to 0.85)

I2 = 14%

 Short term cessation

Not presented

0.92 (0.53 to 1.60)

I2 = 0%

 Longer term cessation

Not presented

0.45 (0.30 to 0.68)

I2 = 0%

 Less intensive

Not presented

0.78 (0.34 to 1.80)

I2 = 0%

More intensive

 More intensive

Not presented

0.55 (0.31 to 0.98)

I2 = 61%

 

COMMENTS:

Results contrast with observational evidence that suggests a lesser effect on total complications.

Only observational studies provided evidence for effect of smoking cessation on pulmonary complications, wound complications, length of stay and mortality. 

Reviewer: Dr Andrew Jull, Associate Professor, School of Nursing, University of Auckland, Nurse Advisor, Quality and Safety, Auckland District Health Board.