Low-intensity pulsed ultrasound elevates blood pressure for shock

Abstract

Fluid replacement is the primary treatment for life-threatening shock but is challenging in harsh environments. This study explores low-intensity pulsed ultrasound (LIPUS) as a resuscitation strategy. Cervical LIPUS stimulation effectively elevated blood pressure in shocked rats. It also improved cerebral and multiorgan perfusion. Mechanistically, LIPUS activated pathways related to sympathetic nerve excitation and vascular smooth muscle contraction, increasing plasma catecholamines and stimulating blood pressure-regulating neural nuclei. Partial sympathetic nerve transection reduced LIPUS efficacy, while complete inhibition of these nuclei abolished the response. Preliminary clinical trials demonstrated LIPUS's ability to raise blood pressure in shock patients. The findings suggest that LIPUS enhances sympathetic nerve activity and activates blood pressure-regulating nuclei, offering a noninvasive, neuromodulation-based approach to shock treatment. This method holds potential for improving blood pressure and organ perfusion in shock patients, especially in resource-limited environments.

Fig. 1.. The schematic of the study.

(A) A diagram shows the elevation of BP through cervical LIPUS stimulation in both normotensive rats and rats with shock-induced BP. The study also explores the effects and potential mechanisms of LIPUS in raising BP through arterial monitoring, HRV analysis, plasma metabolomics analysis, and BOLD-fMRI. A small-scale self-control before-after clinical trial was performed to explore the clinical translational potential of LIPUS. (B) The timeline outlines the design and progression of animal experiments in the study.

Fig. 2.. Cervical LIPUS stimulation elevated BP in rats.

(A to C) BP monitoring data in Sprague-Dawley rats after cervical LIPUS stimulation with different spatial peak pulse average intensity (Isppa) of 1, 2, and 3 W/cm². (D to F) Effect of cervical LIPUS stimulation with different effective ultrasound intensities on BP and HR in Sprague-Dawley rats (n = 5; ns., not significant; HR: *P < 0.05; MAP: ^##P < 0.01, ^###P < 0.001). (G and H) Arterial BP monitoring data after cervical skin electrical stimulation and cervical skin thermal stimulation. (I and J) Statistical analysis of MAP and HR data after cervical skin electrical stimulation and cervical skin thermal stimulation (n = 5).

Fig. 3.. Cervical LIPUS stimulation increased BP in hemorrhagic shock rats.

(A) Representative BP monitoring data after stimulation in normal BP and hemorrhagic shock Sprague-Dawley rats. (B and C) Normal BP group (n = 9) and shock group (n = 8) statistical analysis of MAP and HR data (*P < 0.05; ^#P < 0.05, ^###P < 0.001). (D and E) Normal BP group (n = 9) and shock group (n = 8) HRV in the sympathetic/parasympathetic activity–related HFP, LFP, and LF/HF ratio statistical analysis. (F and G) Representative H&E-stained images of the cervical skin showed that LIPUS stimulation did not affect the superficial skin. (H and I) Representative H&E staining of SNs showed that LIPUS had no damage to the SNs. (J and K) Representative sections of the VN and the accompanying carotid artery (carotid lumen) stained with H&E suggest that LIPUS stimulation causes no damage to the VN.

Fig. 4.. Cervical LIPUS stimulation improved multiple organ perfusion in hemorrhagic shock rats.

(A) Representative cross-sectional echocardiography of control, shock, and shock + LIPUS group. (B) Representative color Doppler flow images of the renal artery and renal interlobar artery. (C) Representative cortical CBF images before and after the stimulation in the normal BP group and shock group were detected by laser speckle contrast imaging instrument. (D and E) Comparative analysis of the brain perfusion in the bilateral cortex ROIs of the normal BP group and the shock group.

Fig. 5.. Plasma metabolomics suggested differentially expressed metabolites and related signaling pathways after cervical LIPUS stimulation.

(A) OPLS-DA analysis showed the intergroup differences and intra-group variations of samples in the control group (n = 9), control + LIPUS group (n = 9), shock group (n = 8), and shock + LIPUS group (n = 8). (B) Ring heatmap showing the top 300 significant different metabolites between the control group, control + LIPUS group, shock group, and shock + LIPUS group. (C) The complex heatmap displays information on the relative expression levels of the top 50 significantly different metabolites among the control group (n = 9), control + LIPUS group (n = 9), shock group (n = 8), and shock + LIPUS group (n = 8). The heatmap includes relative expression values, mean relative values, P values, VIP values, and ontology classification information of the metabolites. (D) Volcano plot showing the differentially expressed metabolites in plasma before and after LIPUS stimulation in the shock group. (E) Top 30 metabolites with VIP values and their fold change in plasma before and after LIPUS stimulation in the shock group. (F) The functional clustering diagram of differential metabolites displays the top 30 pathways based on differential abundance (DA) scores (shock + LIPUS versus shock).

Fig. 6.. The level of catecholamine metabolites detected by plasma metabolomics after the shock rat received cervical LIPUS stimulation is related to the excitement of the SN.

(A) Catecholamine metabolites detected in plasma (n = 8; P < 0.01, P < 0.001; shock-LIPUS versus shock). (B) Correlation matrix of LFP, HFP, and LF/HF ratio (HRV), and the plasma epinephrine 3-sulfate and dopamine (catecholamine metabolites) of shock Sprague-Dawley rats (n = 8; **P < 0.001). (C) Representative BOLD-fMRI images indicate that LIPUS activates the hypothalamic nucleus associated with BP regulation, including OVLT, Pe, and SFO. (D to F) Paired t test statistical analysis of fALFF data from the three ROIs (OVLT, Pe, and SFO) before and after LIPUS stimulation (n = 5, *P < 0.05). (G) Flowchart of the sympathetic inhibition and SFO nucleotomy. (H) Representative T2WI images suggest that 6-OHDA injection successfully disrupted the SFO nuclei. (I and J) Cervical LIPUS stimulation had no significant effect on MAP or HR after inhibition of the SNs or SFO nucleotomy (n = 5).

Fig. 7.. Small-scale self-control before-after clinical trial showed that cervical LIPUS stimulation elevated BP in shock patients.

(A) BP in patients before and after LIPUS stimulation (n = 12 patients; prestimulation: 0 to 5 min, during stimulation: 5 to 10 min, poststimulation: 10 to 15 min). (B) Change in systolic and diastolic BPs of shock patients pre- and post-LIPUS stimulation (n = 12 patients; *P < 0.05). SBP: systolic blood pressure; DBP: diastolic blood pressure.