Procedure does not run in codeigniter

Question

function renovarEmprestimos($matricula, $livro){
$this->db = $this->load->database('biblioteca', TRUE);
$query = $this->db->query("EXEC J_renovarlivroweb '$matricula', '$livro', '1' ");
//$this->db->last_query();
return $query->result();
}

My function was functional but now I can no longer perform EXEC by calling the function. However, if you call $this->db->last_query(); and put EXEC in the sql base works right. How can I run this exec by calling the function?