Hello
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Once the sheath in the groin is removed the patient has to lay on his back for 8 hours from the point of time of removal of sheath. For cardiac catheterisation the sheath can be removed immediately after the procedure. So id the procedure is done during morning hours then he till evening he has to lay on his back. After evening he can sleep as he wishes. If done in evening then he has to lay on back overnight.
Feel free to discuss further,
Regards
Dr Vivek Mahajan
DM Cardiology