Of course it will help to publish in an anesthesiology related journal. Anesthesiology and Anesthesia and Analgesia are both good journals. Sub-specialty journals always have lower impact factors than general interest -- there's a smaller group reading, and fewer citations.
For example, I published in a journal with 9.7 impact factor -- which is great for my research career, but it was basic science -- occasionally I had an interviewer who was into research and asked me about it, but it was outside the area of expertise of a lot of my interviewers so only came up occasionally. For the purposes of residency interviews, something in an anesthesia journal probably would have been more helpful.
That said, I wouldn't start a research project with the idea of publishing in a specific journal -- do research for the experience of doing research, obtain some results, evaluate the quality and significance of your results -- then decide where you want to try publishing.