Real-time instrument tracking is a crucial requirement for various computer-assisted interventions. To overcome problems such as specular reflection and motion blur, we propose a novel method that takes advantage of the interdependency between localization and segmentation of the surgical tool. In particular, we reformulate the 2D pose estimation as a heatmap regression and thereby enable a robust, concurrent regression of both tasks via deep learning. Throughout experimental results, we demonstrate that this modeling leads to a significantly better performance than directly regressing the tool position and that our method outperforms the state-of-the-art on a Retinal Microsurgery benchmark and the MICCAI EndoVis Challenge 2015.