A little bit of swelling and pain in the hand during infusion is because the input fluid stimulates the endothelium of the blood vessel, resulting in inflammation of the endothelium and causing increased permeability of the infused vein, and the fluid in the vein penetrates into the interstitial space of the tissues, which will trigger swelling and pain in the hand, but it will be relieved soon with the prolongation of time. If symptoms persist for a long time, you can elevate the affected arm at rest to promote venous return, or use drugs such as Hilotropin to apply topically to improve symptoms. If symptoms remain severe, oral non-steroidal anti-inflammatory drugs such as ibuprofen or diclofenac sodium can be taken, as well as oral decongestants to promote the absorption of edema and reduce inflammation and pain.