Sim, é possível ter mais de um parâmetro de saída. Aqui está um exemplo que eu uso para chamar um procedimento armazenado Oracle em c#:
OracleParameter op = null;
OracleDataReader dr = null;
/* custom code here. Yours would look a little different */
OracleCommand cmd = (OracleCommand) this.FactoryCache.Connection.CreateCommand();
cmd.CommandText = "pkg_prov_index.getNextPanel";
cmd.CommandType = CommandType.StoredProcedure;
op = new OracleParameter("pCurrentPanelId", OracleType.VarChar);
op.Direction = ParameterDirection.Input;
op.Value = masterProviderIndex.CurrentPanelId;
cmd.Parameters.Add(op);
op = new OracleParameter("pRefCursor", OracleType.Cursor);
op.Direction = ParameterDirection.Output;
cmd.Parameters.Add(op);
op = new OracleParameter("pReturnCode", OracleType.Number);
op.Direction = ParameterDirection.Output;
op.Size = 5;
cmd.Parameters.Add(op);
op = new OracleParameter("pReturnMessage", OracleType.VarChar);
op.Direction = ParameterDirection.Output;
op.Size = 4000;
cmd.Parameters.Add(op);
cmd.ExecuteNonQuery();
returnCode = Convert.ToInt16(cmd.Parameters[2].Value);
returnMessage = cmd.Parameters[3].Value.ToString();
dr = (OracleDataReader) cmd.Parameters[1].Value;
while (dr.Read()) {
}