I gave her extra 1/8 tab of lasix and called the cardiologist. I wasn't sure if I should bring her in or how long to watch and wait. The vet said to watch and wait, give more lasix later, and call her in the morning. We gave extra lasix at bedtime. By late in the evening (before the bedtime dose) her breathing rate had returned to 9 breaths per 15 seconds.
This morning, Myrna is still tired but more alert, a bit more energy, and breathing well at around 8 breaths. I called the vet to give an update and she said that Myrna should from now on be given 1/4 lasix q 6 hrs. (every six hours.) So, for now that means giving an extra dose at bedtime which makes dosing lasix almost a perfect six hours. I might have to actually do on the clock six hours such as 6 a.m., noon, 6 p.m., midnight. The trick is when we start the med in the morning. Myrna hates taking meds in the a.m. and always hides. Getting her to swallow isn't the problem. Catching her, cajoling her, tricking her into being picked up is the problem. For as sick as she is, she is also the quickest cat in the house.