GSC 2022: Heavier patients at greater risk of infection after spinal fusion surgery due to inadequate preoperative cefazolin dosing

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Heavier patients frequently receive an inadequate weight-based dose of preoperative cefazolin and as such have an increased risk of infection following spinal fusion surgery. This is according to the findings of a recent study, presented at Global Spine Congress (GSC) 2022 (1–4 June; Las Vegas, USA) by Mark Lambrechts (Rothman Orthopaedic Institute, Philadelphia, USA), and which also noted that two grams of prophylactic cefazolin significantly reduces the likelihood of infection during spinal fusion procedures.

The study—which won the Best E-poster Award at GSC 2022 and the results of which were also published in The Spine Journal—was intended to determine if perioperative cefazolin dosing affects the infection rate in spinal fusion surgery and also what the appropriate preoperative cefazolin dose based on patient weight is.

The study authors note that perioperative antibiotics “are critical in reducing the risk of postoperative spine infections” but that “currently, there is no global standardisation of weight-based perioperative cefazolin dosing in spine surgery, potentially leading to antibiotic under-utilisation with a resultant increase in the incidence of infections for patients undergoing elective spine fusion”.

Patients who were aged 18 or above undergoing posterior cervical or lumbar spinal fusion between 2000 to 2020 were identified from a single institution. Exclusion criteria included incomplete weight, inadequate perioperative data, a preoperative diagnosis of tumour and/or infection, patients receiving perioperative antibiotics other than cefazolin, and anterior cervical decompression and fusion procedures.

The patients were grouped based on dosing adequacy, with an adequate dose defined as 1g for 120kg. Univariate comparisons and multivariate regressions were used to determine the effect of an inadequate dose on infection rate. Patients were subsequently regrouped into cefazolin dose (grams) administered and a linear regression and receiver operating characteristic curve (ROC) were compiled to determine the probability of infection based on cefazolin dose and patient weight. Alpha was set at 0.05.

A total of 2,814 patients met the inclusion criteria and 101 infections (3.6%) were identified. The infection rate was significantly higher in the inadequate dose group (5.8% vs. 2.6%, p<0.001). Receiving an adequate dose of cefazolin was an independent predictor of decreased rate of infection (odds ratio (OR): 0.48, p<0.001).

On subgroup analysis, receiving an adequate dose of cefazolin was an independent predictor of decreased rate of infection in lumbar fusion (OR: 0.43, p=0.001), but not cervical fusion (OR: 0.45, p=0.055). Patients were subsequently regrouped into one, two, or three grams of cefazolin administered resulting in a 5.08%, 2.75%, and 30.8% infection rate, respectively (p<0.001).

Weight (β= 0.03, p<0.001) and two grams’ cefazolin (β= -1.52, p<0.001) were independent predictors of infection. The area under the curve and 95% confidence interval for one [0.834 (0.759-0.908)], two [0.572 (0.493-0.650)], and three [0.861 (0.646-0.999)] grams cefazolin.


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