Minimize renal complications. Helping patients achieve good intravascular volume and osmolar status preoperatively will reduce their risk of renal complications. Other prophylactic measures: Minimize exposure to nephrotoxins (eg, nonsteroidal anti-inflammatory drugs or contrast media) to the extent possible. Consider evaluating the serum electrolyte and creatinine levels of patients with multiple risk factors to determine whether they can safely undergo surgery; some experts suggest preoperative urinalysis, as well.18
Patients with end-stage renal disease have very high perioperative morbidity.21 They are at increased risk for hyperkalemia, infection, hyper- and hypotension, bleeding, arrhythmias, and clotted fistulas, in descending order of incidence.18 Preoperative planning, including the need for dialysis before surgery, is necessary to manage these risks.
Cardiovascular surgery and acute kidney injury: Scoring the risk
A scoring system developed by Thakar et al20 is a valuable tool in assessing the likelihood that a patient requiring cardiovascular surgery will develop acute kidney injury (AKI).
To identify those at greatest risk, add 1 point for each of the following:
- female sex
- heart failure
- ejection fraction <35%
- chronic obstructive pulmonary disease (COPD)
- insulin-dependent diabetes
- history of prior cardiac surgery
- valve-only cardiac procedure scheduled
Add 2 points for each of the following:
- preoperative intra-aortic balloon pump (IABP)
- emergency surgery
- combined coronary artery bypass graft (CABG)/valve surgery scheduled
- other cardiac surgery (except CABG) scheduled
- creatinine level from 1.2 to 2.1 mg/dL
And add 5 points for a creatinine level >2.1 mg/dL.
Patients with a total score ≤5 have less than a 2% risk of developing AKI; those with scores between 6 and 8 have an 8% to 10% risk, and patients with scores >8 have more than a 20% risk for developing postoperative AKI.
Risk of postop infection: Focusing on the foreseeable
Postoperative infections, both at the surgical site and remote from the incision, are a significant cause of morbidity and mortality. Pneumonia is among the most prominent remote infections associated with surgery,22 and early ambulation, deep breathing exercises, and tight glycemic control can greatly decrease the risk.
Surgical site infection (SSI) remains an important concern, occurring in 37% of cases.23 Risk factors include hyperglycemia, malnutrition, perioperative steroid use, preexisting infections, tobacco smoking, peripheral vascular disease, advanced age, radiation therapy, blood transfusions, prolonged preoperative stay, preoperative shaving, hypothermia, hypoxia, length of operation, and postoperative incontinence.24 While many of these risk factors are dependent on interventions in the operating room and recovery room or during subsequent hospitalization, it is important to address foreseeable risks as part of the preoperative evaluation.
Glycemic control is crucial. Perhaps the most well-documented risk for SSI is hyperglycemia—a common problem among hospitalized patients.16 Hyperglycemia impairs leukocyte and complement function,25,26 thereby increasing risk of infectious complications. Tight glycemic control in the surgical patient, especially on the surgical intensive care unit, has been associated with improved outcomes.27
Identify the presence of diabetes in the preoperative consult note, and adjust the patient’s medication regimen as needed, to help him or her achieve optimal glycemic control. In some cases, it may be necessary to delay nonurgent surgery until the patient achieves adequate control.
Malnutrition is another risk factor for SSI. For patients who are undernourished or morbidly obese, checking serum albumin levels may be beneficial. Supplementation for 1 to 2 weeks prior to surgery may decrease the risk of infection for patients who are undernourished;28 for obese patients, weight loss is beneficial. Although significant preoperative weight loss may not be possible, it is important to list an elevated body mass index as a risk factor in the consultation note.
Corticosteroids, used to treat conditions such as COPD, inflammatory bowel disease, allergies, and autoimmune disorders, are another risk factor for perioperative infection. In addition to their effect on glycemic control, corticosteroids directly suppress the immune system. Whenever possible, they should be discontinued preoperatively. If this is not possible, call attention to the patient’s use of corticosteroids in the consultation note.
Preexisting infection presents the possibility of the spread of organisms to the surgical site and, whenever possible, surgery should be postponed until the infection resolves. If the patient has a history of prior infection or colonization with methicillin-resistant Staphylococcus aureus, be sure to include that in the consultation note, as well.
Leukocyte-containing blood product transfusions are associated with a 2-fold increase in some postop infectious complications.29-31 This is in addition to the well-known risk of bloodborne pathogens associated with transfusions, and is yet another reason to avoid perioperative transfusions whenever possible.