The study evaluated the cumulative effects of repeated general anesthesia (GA) in dogs with cancer, specifically monitoring intra-anesthetic complications and serum cardiac troponin I (cTnI), a sensitive biomarker for myocardial injury.
The trial involved 12 client-owned dogs with various cancers, including one case of metastatic hemangiosarcoma. All dogs required 10 to 20 daily anesthesia sessions for radiation therapy. The researchers prospectively tracked cardiovascular events like bradycardia and hypotension and measured cTnI levels at baseline and after every five anesthetic episodes.
Key findings from the study revealed a trend toward improved cardiovascular stability over time. Comparing the first five to the last five anesthesia sessions, the incidence of bradycardia decreased from 58.3% to 43.8%, and hypotension dropped from 28.3% to 16.3%. Most notably, cTnI concentrations remained stable or even declined throughout the treatment period. No dogs died or were euthanized during the treatment protocol.
The anesthetic protocol, which primarily used sevoflurane and opioids, was reported to be well-tolerated. The need for supportive drugs like anticholinergics decreased over time, while fluid bolus administration increased, suggesting an adaptive and refined approach by the anesthesiologists. The study also highlighted that three dogs with elevated baseline cTnI—including one with confirmed heart disease and metastatic hemangiosarcoma—saw their cTnI levels decrease during the course of treatment.
The study had limitations, including its small sample size and observational design. The heterogeneity in tumor types and the fact that some dogs underwent additional minor procedures during anesthesia were also noted. Despite this, the study provides novel and compelling data on the safety of repeated anesthetic events in a high-risk patient population.
The results challenge the assumption that multiple anesthetics inherently carry cumulative cardiovascular risk. The findings support owner-informed decision-making, providing evidence that concerns over repeated anesthesia should not be a primary barrier to pursuing advanced treatments like radiation therapy. Future studies with larger cohorts are planned to further validate these encouraging results.
