Final answer:
To code the patient's hospital record correctly, the coder must use the version of ICD-9-CM updated on October 1, 2011.
Step-by-step explanation:
In this scenario, the coder must use the version of ICD-9-CM updated on October 1, 2011. The reason for this is that the patient was discharged on October 5, 2011, which falls after the September 30, 2011, cutoff date for the previous version of ICD-9-CM. The version updated on October 1, 2011, would include any changes or revisions made up to that date, ensuring accurate coding for the patient's record.