Haematological effect of pulsed ultrasound in acute muscular inflammation in rats

Objective

To evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on the haematological dynamics of an acute inflammatory process after an iatrogenic muscular lesion.

Design

Controlled laboratory study.

Setting

Research laboratory.

Participants

Eighteen male Wistar rats (weight 350 to 450 g) were submitted to surgical incision in the biceps femoris muscle (approximately 50%), and subsequently subdivided into control (n = 9) and LIPUS (n = 9) groups.

Intervention

Ultrasound (1.0 MHz) was applied at the lesion site in the pulsed mode (2 ms on, 8 ms off) at 0.4 W/cm² for 3 minutes at 1, 8 and 24 hours post-surgery.

Main outcome measures

In these periods, blood was collected through venepuncture of the retro-orbital plexus and evaluated for different types of leukocytes and erythrocytes.

Results

LIPUS reduced the total leukocyte count at 1, 8 and 24 hours post-surgery (1 hour, control 9017.2 ± 481 × 10³/mm³ vs LIPUS 6189.8 ± 450 × 10³/mm³; 8 hours, control 8078.2 ± 501 × 10³/mm³ vs LIPUS 5371.3 ± 378 × 10³/mm³; 24 hours, control 8192.3 ± 646 × 10³/mm³ vs LIPUS 6059.1 ± 503 × 10³/mm³; P < 0.001). The monocyte count was reduced at 8 and 24 hours post-surgery (8 hours, control 815.5 ± 126 × 10³/mm³ vs LIPUS 375.4 ± 70 × 10³/mm³; 24 hours, control 875.3 ± 124 × 10³/mm³ vs LIPUS 564.7 ± 56 × 10³/mm³; P < 0.001). The number of segmented neutrophils was only reduced at 1 hour post-surgery (control 5033.1 ± 397 × 10³/mm³ vs LIPUS 3594.8 ± 191 × 10³/mm³; P = 0.006), and the lymphocyte count was only reduced at 8 hours post-surgery (control 4759.7 ± 459 × 10³/mm³ vs LIPUS 2584.1 ± 356 × 10³/mm³; P = 0.003). Changes were not observed in the concentrations of young neutrophils, polibocytes and erythrocytes.

Conclusion

LIPUS reduced aspects of the inflammatory process following an acute incisional muscular lesion.