Can stress and anxiety cause bouts of tachycardia lasting hours? went to er only finding sinus tach that went away after taking ativan (lorazepam) and saline drip

Possibly: It is good that you went to the ER for eval. It is also good that these symptoms seem to improve with a drug for relaxing people and fluids for hydration. I've answered similar questions here. Generally it is not normal to have prolonged sinus tachycardia- I suggest you see a cardiologist, and consider endocrine causes of tachycardia. Thyroid particulary. Siggest you reduce your stress. Be well!