# Comparison of metabolic rates of ropivacaine in cerebrospinal fluid as inferred from plasma concentrations between elderly patients and young patients

## TL;DR

This study compares how elderly and young patients metabolize ropivacaine in cerebrospinal fluid, finding slower metabolism in the elderly.

## Contribution

The study provides new insights into age-related differences in local anesthetic metabolism in cerebrospinal fluid.

## Key findings

- Elderly patients metabolize ropivacaine more slowly in cerebrospinal fluid compared to young patients.
- Hyaluronic acid levels are significantly higher in the cerebrospinal fluid of elderly patients.
- Ropivacaine anesthesia lasts longer in elderly patients, suggesting a need for reduced dosing.

## Abstract

With the aging of human society, more and more elderly patients have to undergo surgery and anesthesia. Clinical observations have indicated from time to time that spinal anesthesia in the elderly appears to last longer than in young people, although there is limited research in this area and the mechanism is unclear at present time. This research work is expected to help understand the decline of local anesthetic metabolism in cerebrospinal fluid of elderly patients so as to help them with precise anesthesia and rapid rehabilitation.

Twenty patients with spinal anesthesia in orthopedic lower limb surgery were selected to study the rate of drug metabolism in cerebrospinal fluid in two age groups, i.e.,18–30 years old and 75–90 years old. Ropivacaine in peripheral blood is used as a probe to reflect the speed of drug metabolism in cerebrospinal fluid. The contents of total Aβ protein and hyaluronic acid in the cerebrospinal fluid were investigated as well.

The equivalent dose of ropivacaine anesthetizes the elderly group for a longer time. The metabolism rate of ropivacaine in an elderly patient was slower than that of a young patient. No significant difference in total Aβ protein between the two groups was observed while hyaluronic acid in the elderly group was significantly higher than that in the young group.

This study shows that the dose of ropivacaine should be reduced when used for anesthesia in elderly patients. The cumulation of ropivacaine and HA appears to imitate the degeneration of central lymphatic circulation metabolism in elderly people.