What are the implications of low creatinine levels on surgical outcomes?

From the Guidelines

Low creatinine levels before surgery can potentially impact surgical outcomes and should be evaluated carefully, as they may indicate decreased muscle mass, malnutrition, liver disease, or pregnancy rather than improved kidney function. Patients with low creatinine often have poorer surgical outcomes due to underlying frailty, reduced physiological reserve, and impaired wound healing 1. Before surgery, patients with low creatinine should undergo nutritional assessment and possibly receive protein supplementation (1.2-1.5 g/kg/day) for 1-2 weeks preoperatively if time allows. Some key points to consider in the management of patients with low creatinine levels before surgery include:

• Surgeons may need to modify anesthetic dosing since many medications are cleared by the kidneys, and low creatinine can mask early kidney dysfunction 1.
• During the perioperative period, careful fluid management is essential, with balanced crystalloid solutions preferred over normal saline to maintain adequate hydration without volume overload.
• Postoperatively, these patients require vigilant monitoring for complications, particularly infection and delayed wound healing. The connection between low creatinine and poorer outcomes stems from its reflection of reduced muscle mass and overall frailty, which diminishes the body's ability to withstand surgical stress and recover effectively 1. It is also important to note that reduced kidney function is an independent risk factor for adverse post-operative cardiovascular outcomes including MI, stroke, and progression of heart failure, and estimated creatinine clearance provides a more accurate assessment of renal function than serum creatinine alone 1. Therefore, a comprehensive preoperative evaluation, including assessment of renal function and nutritional status, is crucial to optimize outcomes in patients with low creatinine levels undergoing surgery.

From the Research

Low Creatinine and Surgery Outcomes

• Low preoperative serum creatinine is associated with poor outcomes after nonemergent inpatient surgery, with increased odds of mortality and major complications 2.
• A study of 1,809,576 patients found that 27.8% of males and 23.5% of females had low preoperative serum creatinine, and those with low creatinine had higher odds of mortality and major complications 2.
• The association between low creatinine and poor surgical outcomes persists even among patients with mildly low albumin and for those with creatinine values measured 8 to 30 days preoperatively 2.

Preoperative Renal Function and Surgery Outcomes

• Minimal changes in preoperative renal function are associated with a substantial increase in the risk of mortality and morbidity following cardiac surgery 3.
• Preoperative estimated creatinine clearance is a stronger predictor of postoperative renal failure and hospital morbidity than preoperative serum creatinine 4.
• Effective strategies for nephroprotection are crucial for the handling of patients with chronic kidney disease (CKD) in the perioperative setting to prevent complications and to avoid the progression of CKD 5.

Creatinine Clearance and Surgery Outcomes

• Calculating creatinine clearance as an alternative measure to serum creatinine may give a better estimation of postoperative renal function in patients undergoing coronary artery bypass grafting 6.
• Patients with occult renal insufficiency (serum creatinine ≤1.1 mg/dL and creatinine clearance ≤60 mL/min) are at higher risk for mortality and prolonged hospital stay compared to those with normal renal function 6.
• The preoperative calculation of creatinine clearance is recommended to identify higher-risk patients requiring special intensive care 6.