Get columns from NEW when execute update on postgresql

I need know if determide fields are into result of update execution, e.g.

IF NEW.niveope is null THEN
    _new_nivope := 0;
ELSE
    _new_nivope := NEW.nivope;
END IF;

When I execute:

EXPLAIN ANALYZE UPDATE operador SET cad_apoio_co=0 where id=5;

I get the result message: ERRO: registro "new" não tem campo "niveope" or something like ERROR: "new" not have "niveope"

Are possible validate if "NEW" contains or not a especific field before use it?

Thanks