Urinary tract infection
This is a common and costly HCAI just as SSI is. The risk factors for post- operative urinary infections are:
presence of neoplasm •
urinary obstruction/urinary stasis •
presence of urinary catheter •
presence of urinary stent •
urinary calculi and other underlying disease. •
The defi nition of a lower urinary tract infection (UTI) depends on symp- toms (not present with a urethral catheter in place) of ‘cystitis’ – i.e. frequency, dysuria, haematuria. An MSU may show sterile pyuria but it needs a bacteriuria of 105 organisms/ml to be diagnostic. Lower numbers
of bacteria may represent commensals. In the presence of signifi cant UTI, bacteraemia may follow instrumentation and antibiotics should be given prophylactically and as treatment, particularly when patients have a pros- thesis or replaced heart valve. All Trusts have antibiotic protocols for this, which are based on current national guidelines and local bacterial sensi- tivity patterns, and should be followed. Upper urinary tract infection can follow ascending infection or bacteraemia. It is more likely to present with high pyrexia (~40°C) and rigors.
The organisms causing UTIs are mostly aerobic Gram-negative bacilli: principally E. coli, but also Proteus and Pseudomonas spp. (the latter can be an unwanted colonizing organism prevalent on urology wards and ITUs). Staphylococci may colonize the lower urinary tract when there is a catheter and Candida spp. may appear after prolonged catheterization, particularly after prolonged antibiotic use. Urinary tract infections are a common cause of post-operative pyrexia.
Treatment involves the use of large-volume fl uid therapy to ensure an adequate diuresis and appropriate antibiotics, preferably chosen from the results of culture and sensitivities. Underlying obstructive and other disease should be attended to, with early removal of catheters and stents when possible.
Resistance is another growing problem with the rise of extended spectrum B lactamases arising in many of the coliform organisms that cause UTIs, particularly in secondary care ( b see Chapter 18, Complications of urological surgery, p.347).
Respiratory tract infection
The alveolar–capillary interface, and ventilation–perfusion balance, is a delicate one. Post-operative respiratory tract infections (RTIs) can be anticipated in patients with restricted airways: where lung volumes are reduced but patients have a reasonable one-second forced expira- tory volume – FEV1 (such as fi brosing alveolitis, chest wall disease, after
pneumonectomy, and pneumoconiosis); and in obstructive airways disease with a reduced FEV1 of <70% (those patients with chronic bronchitis,
37
URINARY AND RESPIRATORY INFECTIONS
spirometry – an FEV1 of <1 litre is particularly poor. Arterial blood gases
identify the ‘pink puffer’ with a low PaCO2 and the ‘blue bloater’ with a
high PaCO2 (cor pulmonale and right ventricular failure). Pre-operative
physiotherapy and choice of the time for surgery when respiratory func- tion is optimized may reduce post-operative respiratory tract infection. Cessation of smoking at least 4–6 weeks prior to surgery results in an improvement in respiratory function and less viscid bronchial secretions.
Atelectasis during the fi rst 24–48 hours is recognized as poor basal air entry, dullness to percussion, and extra sounds. It is a common cause of early post-operative pyrexia and responds to good pain relief and physiotherapy. Chronic obstructive pulmonary disease may become acute, with an increase of pathogens such as Haemophilus spp. and Pneumococci. Progression to bronchopneumonia can be prevented with physiotherapy and appropriate antibiotics. Aspiration leads to profound pneumonitis, which may progress to lobar pneumonia or lung abscess without bronchial lavage and respiratory support. Pneumonias involving aerobic Gram-negative bacilli are common after prolonged ventilation on ITU and are related to sepsis and MODS, including ARDS. Ventilation may be required if physiotherapy, antibiotics, and aids to breathing fail.
Resistance is being seen in the Enterococci (vancomycin resistance, VRE, and other glycopeptide resistance, GRE), which are causes of ventilator associated pneumonia (VAP). This is in addition to increasing resistance being seen in ‘conventional’ respiratory pathogens such as Streptococcus
pneumoniae. ( b Also see Post-operative pyrexia, p.40 and Respiratory
compromise in sepsis, p.49, and Chapter 11, Complications after cardiothoracic surgery, p.231.)
Post-operative peritonitis
Post-operative peritonitis may follow an anastomotic leak after oesopha- geal, rectal, colonic, pancreatic, or biliary surgery; or it may follow inad- equate source control at emergency operations for community-acquired peritonitis (perforated peptic ulcer, pancreatitis, perforated appendix, gallbladder, or colonic pathology).
Post-operative ileus associated with peritonitis may be diffi cult to differentiate from obstruction during the early post-operative days. There is now evidence that giving early enteral feeding helps to prevent intestinal mucosal atrophy with resulting intestinal colonization and translocation to mesenteric lymph nodes and the promotion of sepsis. Certainly, attention should be given to nutrition whilst determining the cause of an ileus/ obstruction and assessing whether re-laparotomy is necessary. Gastric and small bowel ileus is treated with decompression. Enteral nutrition can be provided by nasojejunal feeding or direct jejunal feeding using a jejunostomy that has been placed at the primary operation.
Enteral feeding is always preferable to total intravenous parenteral nutrition, which carries the risk of complications of insertion as well as a major risk of infection and further sepsis. Water, electrolyte, and acid– base balance can usually be managed using a peripheral IV line ( b see Chapter 5, Complications of nutrition, p.99).
Signs of SIRS and MODS need to be monitored and early appropriate organ support instituted if necessary; in particular, signs of acute tubular necrosis associated with hypovolaemia, ARDS, and the need for
38
CHAPTER 2Infection
cardiovascular support with fl uids and inotropic support. ( b See SIRS, sepsis, MODS, and organ failure, p.46.)
Antibiotics need to be considered, but complications of resistance (MRSA, multiple-resistant coagulase-negative Staphylococci, and vancomycin- resistant Enterococci), emergence (fungal infection, Clostridium diffi cile enteritis), toxicity, and allergy need to be taken into account. A second line of antibiotics, agreed by protocol, should be used to empirically cover the spectrum of likely organisms. This may either be monotherapy (using, for example, a carbapenem such as imipenem or meropenem) or combination therapy (such as piperaeillin-tazobactam and metronidazole), but not with the same antibiotics used to treat the peritonitis that led to the fi rst operation.
Second look operations to exclude an abdominal cause of sepsis, such as a pelvic or subphrenic abscess or a suspected anastomotic leak, should be made on demand rather than on a routine basis. Although percutaneous drainage using imaging control may be appropriate, it cannot substitute peritoneal lavage with exteriorization of bowel ends after an anastomotic leak. The development of abdominal compartment syndrome should always be considered with the need for laparostomy ( b see Chapter 9, Complications of gastrointestinal surgery, p.159).