###HUMAN: what is the dose of sodium bicarbonate that is first prescribed to patient 10811 since 05/2103?, ###ASSISTANT: SELECT prescriptions.dose_val_rx FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 10811) AND prescriptions.drug = 'sodium bicarbonate' AND STRFTIME('%y-%m', prescriptions.startdate) >= '2103-05' ORDER BY prescriptions.startdate LIMIT 1