What you describe, including improvement with Combivent® Inhalation Aerosol (ipratropium bromide and albuterol sulfate), suggests that you may have cough variant asthma; that is, asthma with cough rather than wheeze as the main symptom. This asthma may or may not be related to the anesthesia administered 18 years ago but that is of no consequence. You should seek evaluation for asthma, by your doctor or by a lung specialist also known as a pulmonologist. There are more potent medicines than those in Combivent® Inhalation Aerosol (ipratropium bromide and albuterol sulfate). It is conceivable that your cough could be relieved completely.
Good luck.