Psalm 88 is a Messianic Psalm, but in indirect ways.  Because the Psalm contains the words of the anointed King, it contains the words of Christ. The utter isolation and anguish of the Psalm is the utter isolation and anguish of Jesus.  No matter how low we go, we’ll still find Jesus, lower still, holding us up.

The Psalm also questions whether Yahweh can be praised in the grave, by the shades that populate Sheol.  That question is left unanswered here, but the gospel answers it.  Because Jesus has descended to the grave, because He has become Lord of death, the dead do praise Him.