Table 2.

Histology Injury Scoring System (HISS) for Hypoxic-induced Muscle Injury

Morphological Changes	Categories
Interstitial edema	0. No significant increase 1. Minimal 2. Intermediate 3. Severe/diffuse
Inflammation	0. Not significant 1. Minimal 2. Intermediate 3. Diffuse
Variation in shape and size of myocytes	0. Homogeneous 1. Mild heterogeneous 2. Intermediate heterogeneous 3. Severe heterogeneous
Damaged muscle fibers*	0.0–5 myocytes/10 HPF (20× magnification) 1.6–20 myocytes/10 HPF (20× magnification) 2.21–50 myocytes/10 HPF (20× magnification) 3.>51 myocytes/10 HPF (20× magnification)
Total score	0–4 No/minimal degeneration 5–7 Intermediate degeneration 8–12 Severe degeneration

*Damaged muscle fibers: a sum of necrotic, hypoxic and phagocytic myocytes