Antibiotic prophylaxis in surgery. (SIGN Guideline No 104)

Antibiotic prophylAxis in surgery
6.4.2 BlooD loSS, FluID REPlACEMENT AND ANTIBIoTIC PRoPHYlAxIS
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Serum antibiotic concentrations are reduced by blood loss and fluid replacement, especially
in the first hour of surgery when drug levels are high. 49,164,165
The precise effects of blood loss and fluid replacement are difficult to predict and will depend
upon the particular antibiotic used, the time and rate of blood loss and fluid replacement.
A small pharmacokinetic analysis of cloxacillin levels in children undergoing major facial
and neck surgery showed that the associated massive blood loss led to serum cloxacillin
concentrations below therapeutic levels for significant proportions of surgery. 49
In a small prospective study of 11 adults undergoing elective surgical spinal instrumentation
procedures with an expected large blood loss there was a significant correlation between blood
loss and tissue cefazolin concentration. Where there was significant blood loss (>1,500 ml)
and the surgery lasted over three hours the tissue concentration of cefazolin fell below the
minimum inhibitory concentration. 166
;
;
In the event of major intraoperative blood loss in adults (>1,500 ml) additional dosage
of prophylactic antibiotic should be considered after fluid replacement.
In the event of major intraoperative blood loss in children (25 ml/kg) additional dosage
of prophylactic antibiotic should be considered after fluid replacement.
6.5 route of ADministrAtion
Systemic antibiotic prophylaxis, typically given by the parenteral intravenous route (Iv), has
historically proven to be a reliable and effective prophylaxis against SSI in all types of surgery.
;
Prophylactic antibiotics for surgical procedures should be administered intravenously.
6.5.1 oRAl ADMINISTRATIoN
Serum and tissue concentrations after oral administration are determined in part by the rate
of absorption, which varies between individuals. There is relatively little evidence about the
effectiveness of orally administered antibiotic prophylaxis. A further problem is that often the
correct time of administration is difficult to guarantee in practice, because, for example, it occurs
outwith the theatre environment.
Administration of fluoroquinolones by the oral route achieves comparable serum and tissue
levels to antibiotic prophylaxis via the Iv route. 127,167-175
Intensive antibiotic use and in particular fluoroquinolones and cephalosporins contributes
significantly to the two major antibiotic resistance issues that confront hospitals today, namely
MRSA and C. diff. 174-178 In any patient known to be carrying MRSA it is unwise to prescribe
these agents, as this may lead to overgrowth of MRSA and higher subsequent risk of infection.
Similarly, as short a course of prophylactic antibiotic as possible will keep the risk of symptomatic
C. diff to a minimum.
6.5.2 ToPICAl ADMINISTRATIoN
high-risk surgery
There is evidence that supplementary application of resorbable gentamicin-impregnated collagen
fleeces after abdominoperineal excision of rectal cancer 179 or gentamicin-collagen implant
between the two halves of the sternum after cardiac surgery, may minimise wound infection
after surgery. 180,181
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