La. Civ. Code art. 3062
The modification or amendment of the principal obligation, or the impairment of real security held for it, by the creditor, in any material manner and without the consent of the surety, has the following effects.
An ordinary suretyship is extinguished.
A commercial suretyship is extinguished to the extent the surety is prejudiced by the action of the creditor, unless the principal obligation is one other than for the payment of money, and the surety should have contemplated that the creditor might take such action in the ordinary course of performance of the obligation. The creditor has the burden of proving that the surety has not been prejudiced or that the extent of the prejudice is less than the full amount of the surety's obligation.
La. C.C. § 3062