Hi Maria,
It is difficult to deal with Anxiety when you are put under a lot of stress, but now, for your partner, you must be strong. I hope you have therapy/mental techniques/meds to help you cope, and you have to draw on every resource for your partner.
Re-assure him that his Anaesthetist and Surgeon are true professionals who will take the best care of him. Being scared is natural, but it is a damaging emotion which will hamper you both physically.
Draw on your love for each other to get you through these difficult days. Talk about your plans for when the op has been a success.
Don't let each other's fear and anxieties feed off each other - you have too much to look forward to. Take a breath.
Keep calm, good luck,

Dave.