I suspect that the query is logically incorrect. Since you have declared the variable @Descricao but not assigned any value to it.
declare @Descricao as varchar(200)
select top 1 lt.txtDescricao
from gpv_promocoes p
inner join GPV_Log l
on p.codPromocao = l.cod_objeto
inner join GPV_Log_Tipo lt
on lt.cod_tipolog = l.cod_tipolog
where p.codPromocao = @codPromocao and lt.txtDescricao = @Descricao
--Ramesh