Cooperative non-orthogonal multiple access (C-NOMA) has been gradually discussed in the ultra-reliable and low-latency communication (URLLC) scenarios. The recent research indicates that when optimizing blocklength, selection combining the re-transmission packet cannot sufficiently exploit the potential of C-NOMA. To tackle this problem, we propose a packet re-management framework to transmit different packets through direct and relay links, therefore, propose an energy-efficient transmission scheme. By investigating power consumption of unequal-blocklength non-orthogonal multiple access with appropriate successive interference cancelation order, we jointly optimize blocklength, power, and re-managed packet size to minimize the power consumption, under URLLC requirements and the maximum power constraint. Simulation results verify that the proposed scheme can reduce power consumption.