instruction: tell me the maximum hospital cost if there is a s/p thrombectomy since 6 years ago?
response: SELECT MAX(t1.c1) FROM (SELECT SUM(cost.cost) AS c1 FROM cost WHERE cost.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.patientunitstayid IN (SELECT diagnosis.patientunitstayid FROM diagnosis WHERE diagnosis.diagnosisname = 's/p thrombectomy')) AND DATETIME(cost.chargetime) >= DATETIME(CURRENT_TIME(), '-6 year') GROUP BY cost.patienthealthsystemstayid) AS t1