Dear nitric oxide increases the pain crisis noticed in sickle cell patients especially in crisis stage because the level of nitric oxide is elevated. In the management the level should be controlled.

these URLs articles explain nicely the role of nitric oxide

Article Sickle cell disease and nitric oxide: A paradigm shift?

http://www.bloodjournal.org/content/112/11/sci-48?sso-checked=true

https://www.eurekalert.org/pub_releases/2014-03/mcog-llo032014.php

Some useful links:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2199240/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3460398/

https://clinicaltrials.gov/ct2/show/NCT00009581

https://www.sciencedirect.com/science/art

Please have a look at this similar RG discussion thread.

https://www.researchgate.net/post/What_is_the_role_of_Nitric_Oxide_in_Sickle_Cell_disease_Management