Dear Neha,
It appears that you need to revisit the fundamentals of HR Management. The second sentence of your post reads "This year we are going to give performance appraisal to Employees in the month of..." Please note that employers do not "give" performance appraisal to the employees but it is "conducted".
Instead of "salary hike", have you used the term "performance appraisal"? By reading your post, one gets a feel of that. If yes then it is important for you to refurbish the HR terminology. Yes, the salary hike is generally followed by the performance appraisal. Now whether the salary hike takes place or not, PA has to be conducted. It is a routine HR process like monthly disbursement of the payment and wages and there is no escape from it. While the payment is disbursed monthly, the PA may be conducted quarterly, half-yearly or yearly.
As HR professionals if you have captured the feelings of the senior management personnel on the consequences of not giving the salary hike then you are expected to convey their feelings to the top boss. To remove the apprehensions of the few senior employees, your top boss may call a meeting of all HODs and convey what is expected to happen in the month of April. Let the communication pass downward in the respective department. Timely communication could avoid misunderstanding if any.
Thanks,
Dinesh Divekar