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INFECTION CONCERNS OVER CAESAREAN RISE

January 2011

As rates of Caesarean section continue to rise, the numbers of mothersexperiencing surgical site infection (SSI) are also set to increase, warnsClaire Banks, a senior specialist registrar in obstetrics and gynaecology.LOUISE FRAMPTON reports.

Speaking at Ethicons annual symposium on surgical site infection, ClaireBanks, senior specialist registrar in obstetrics and gynaecology, West oScotland Deanery, NHS Education for Scotland, pointed out that the rate ofCaesarean sections (CS) in the UK has increased from just 9%, in 1980, toaround 25% in recent years the equivalent of 155,000 births per year. Ofthese CS births, 62,000 are elective procedures. However, the percentagevaries throughout the UK, with some private units recording rates as high as35%. This pales into insignificance compared to worldwide figures, howeverIn China the figure is 46% while, in some parts of Brazil, the figure reaches

almost 80%. This is despite the fact that the World Health Organizationrecommends that the rate should not be more than 10% to 15% i.e. the same rate as 30 years ago. Several factorscould be responsible for this rise, including a general increase in levels of obesity. A referral to an anaesthetist waspreviously made for a BMI of over 30, at booking, but as obesity has become more common, women are now only referredif they have a BMI greater than 40. Obesity is also associated with several other risks in pregnancy, including thedevelopment of conditions such as gestational diabetes, hypertension and pre-eclampsia. This may mean an increase inthe rates of induction of labour, which in turn leads to failed induction or failure to progress in labour, and these are twosignificant reasons given for performing a CS.

A mothers larger size can sometimes lead to a larger baby, but it may also result in growth restriction (although thesebabies are also common in women of lower socioeconomic class or smokers). Claire Banks explained that these babies donot tend to tolerate labour as well, leading to another main reason for CS (i.e. fetal distress). Other influential factorsinclude increasing maternal age, increased use of IVF and teenage pregnancies. Increasing maternal age and IVFpregnancies are not necessarily a problem, but among this group are women from the maternal request category. Thereis also an increased incidence of multiple births with IVF. Unfortunately, a significant number of our patients are also inthe teenage category i.e. the 14-16 age group. Although they usually want to avoid CS, sometimes their pelvis is just tooimmature to allow passage of the baby. Finally, repeat CS accounts for up to a quarter of all CS procedures performedand is perhaps the only variable that we may be able to do something about by encouraging women to have a trial ofvaginal delivery following previous CS. Claire Banks pointed out that, as many of these factors will prove difficult toinfluence, it is crucial that surgery is made as safe as possible, which includes reducing surgical site infection rates.

CS carries several potential complications, which are explained at the time of signing the consent form. Infection is themost common potential problem (4% to 6%), with readmission to hospital a close second (5%). However, the readmissionto hospital is invariably due to infection, so the two are, in fact, linked. Risk of haemorrhage requiring transfusion is low, asis trauma to the bladder or ureters, but the risk of thromboembolism is 3.6 times higher than those with a normaldelivery, she commented. She explained that, in terms of the symptoms associated with infection, discharge is commonand is usually the first thing that a woman will notice and complain of. Dehiscence is not uncommon, but usually happensafter release from hospital. Women do not usually have pyrexia or malaise with wound infection alone, and there is usuallysome other co-existing source of infection if this is the case. Abscesses are rare, she added, although wound haematomasoften precede either discharge from the wound or dehiscence.

Risks of wound infection

She went on to outline the risks of wound infection post CS and cited obesity as one of the biggest risk factors fordeveloping wound infection. Possible biological explanations are that: adipose tissue is relatively avascular; there is anincreased wound area, and also potentially poor penetration of prophylactic antibiotics in adipose tissue. In addition, wherethe transverse incision lies within a fold of skin, the area can become moist and provide an ideal environment in whichbacteria can grow. As around 20% of pregnant women are now classed as obese and around 50% of these will deliver byCS, this presents a major issue, she warned. Development of subcutaneous haematomas has also been shown to be animportant risk factor. A study carried out by Olsen et al in the US, in 1999-2001, looked at a total of 1,600 women whounderwent CS, and found that postoperative development of a haematoma was the strongest independent risk factor fordeveloping wound infection. It is unclear whether or not the use of electrocautery would decrease the rate of haematomaformation, and this may be something that requires closer examination, she suggested.

Other potential risk factors have been examined in an Australian study by Webster, in 2008. This was a prospective studyof 1,500 women who underwent CS and showed an infection rate of 9%. The factors that had statistical significance in the

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development of infection were the number of vaginal examinations performed (if in labour), the category of the surgeon,and the length of the operation. Previous wound infection was also found in over half of those affected. However, electiveprocedures had a lower rate than emergencies. Infection has, in some studies, been shown to occur more frequently withhigh pre-operative blood glucose levels. Therefore, it is perhaps surprising that there does not appear to be an increasedrisk with maternal diabetes. This may be due to the fact that pregnant women generally have tight glycaemic control,commented Claire Banks. She went on to examine the role of surgical techniques which have an impact on the rate ofwound infection. For example, the issue of adhesive drapes were looked at in two RCTs by Ward et al in 2001, and anearlier study by Cordtz et al. Both examined their use as an isolated intervention in the prevention of wound infection postCS, but did not find any difference in the rates of infection. With regards to type of incision i.e. longitudinal or transverse,the NICE guidelines quote 10 RCTs all of which concluded that there was no difference in the incidence of woundinfection. This was also confirmed by the previously mentioned Australian study by Webster in 2008.

Claire Banks highlighted the fact that there have been no studies, to date, regarding instruments for incision during CSand the data available relates to general surgical procedures. However, this has indicated that there is no difference in therates of wound infection if one scalpel is used solely for the skin, and a further scalpel for deeper layers. No difference wasalso found when comparing entry with a scalpel or electrocautery. She added that, regarding use of different materials ormethods of closing sheath, there is currently no available evidence for CS. Research may be required, therefore, usingnewer materials, to see if there is any difference. There may be some benefit in closing the subcutaneous layer if it ismore than 2 cm deep. Despite this, practice varies widely, with 42% of obstetricians never closing it, 21% always closingit, 8% only closing it if the layer is thin (to prevent tethering of the scar to the sheath), and 28% closing if the layer isthick. Clearly, there is no consensus and this could be an area where following NICE guidelines could be beneficial, shecommented. Five RCTs looked at the routine use of superficial wound drains and, from this, NICE guidance has advisedthat they should not be routinely used, as they do not decrease the incidence of either wound haematoma or infection.Method of skin closure remains contentious, with conflicting evidence. However, a Glasgow-based study, by Johnson et al,found that the use of staples doubled the risk of wound infection.

Antibiotics

One of the most important factors influencing the development of wound infection is use of antibiotics. A Cochranedatabase review by Smaill, which looked at 86 studies involving over 13,000 women, showed that the use of prophylacticantibiotics at the time of CS substantially reduced the risk of infection, by up to 70%. It has also been shown that a singledose regime is as effective as multiple doses, and that there is no difference between the use of either a 1st, 2nd or 3rdgeneration cephalosporin. Timing also appears to be very important, with a study by Owens et al (2004), involving over9,000 women, showing that administration of antibiotics prior to skin incision, as opposed to after cord clampingdecreased the rate of wound infection although it is uncertain whether this timing has effects on the baby, such as oralthrush.

In fact, studies suggest that antibiotics have the potential to significantly reduce the cost burden associated with suchinfections. A study carried out in the UK, in 1989, by Mugford et al, found there was an additional extra cost of 716 perpatient if wound infection occurred. By extrapolating data, it was calculated that the use of prophylactic antibiotics foreveryone undergoing CS would reduce the cost of care by between 1,300 and 3,900 per 100 CS. A saving of between13 and 39 per operation may not seem much, but if we multiply that by the number of procedures performed annually

in the UK, that would lead to an average saving of between 2 m and 6 m per year for the NHS, Claire Banks pointedout. Ultimately, the consequences of surgical site infection for mothers can be far reaching and costly, as Claire Bankshighlighted. The physical effects include a prolonged recovery time and, on average, a longer hospital stay of an extra twodays, but the social impact also needs consideration.

The resulting scars can be unsightly and affect the womans self confidence long term sometimes even necessitatingfurther surgery for cosmesis. In addition, infection can affect the bonding process, as mothers may find it difficult and veryuncomfortable to hold or pick up their baby. This, in turn, can affect breastfeeding. Reminding the audience of the humanimpact, she commented: This is meant to be a special time for a woman and her family, and unfortunately woundinfection can turn it into a memorable time for all the wrong reasons.

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