# Safety of blood reinfusion drains after local infiltration analgesia in total joint replacement

## TL;DR

This study shows that reinfusing shed blood after joint replacement surgery is generally safe, but patients with lower BMI undergoing hip surgery may face higher risks of drug toxicity.

## Contribution

The study provides new evidence on levobupivacaine levels in shed blood after joint replacement and identifies BMI and surgery type as risk factors for toxicity.

## Key findings

- Levobupivacaine levels in shed blood were below toxicity thresholds at 2 and 5 hours post-surgery.
- THA patients had significantly higher levobupivacaine concentrations than TKA patients.
- Patients with lower BMI had higher drug levels and lower blood volume needed for toxicity.

## Abstract

Local infiltration analgesia (LIA) is frequently administered to patient undergoing joint replacement surgical procedures. The aim of the present research was to verify the safety of collected shed blood to be reinfused postoperatively, by measuring levobupivacaine levels in drainage blood in patients undergoing LIA during knee replacement surgery.

24 patients who underwent total knee arthroplasty (TKA) and 12 scheduled for total hip arthroplasty (THA) who received intraoperative LIA were considered. Blood samples were collected from shed blood which was present in drainage 2 and 5 hours after surgery and serum was analysed by liquid chromatography-tandem mass spectrometry.

At 2 hours postoperatively, the median levobupivacaine serum concentration in the collected shed blood was 1.2 mg/L (SD: 4.2) for TKA and 17.13 mg/L (SD: 24.4) for THA. At 5 hours, levobupivacaine concentration was 1.84 mg/L (SD: 2.2) for TKA and 17.5 mg/L (SD: 25.2) for THA. Higher values of average serum levobupivacaine concentration were reported in drains collected from patients who had undergone THA compared to TKA (p<0.001). BMI significantly influenced levels of serum drug, that resulted to be higher in patients with BMI<25 (p= 0.01).

Levobupivacaine from collected shed blood that would have been returned to the patient, was below toxicity level at 2 and 5 hours after LIA during total joint replacement. The average serum levobupivacaine concentration was found to be higher in drains taken from THA patients than TKA patients. Patients with lower BMI demonstrated the highest levels of levobupivacaine in shed blood and a lower blood volume needed for central nervous system toxicity. Therefore, in patients with a lower BMI undergoing THA, anaesthetic dosage should be reduced or autotransfusion should be avoided to prevent potential risks of toxicity.

The online version contains supplementary material available at 10.1186/s12891-024-07261-z.