Injury characteristics and hemodynamics associated with guideline-compliant CPR in a pediatric porcine cardiac arrest model

Proportional Versus Fixed Chest Compression Depth for Guideline-Compliant Resuscitation of Infant Asphyxial Cardiac Arrest

OBJECTIVES

Current guidelines for parameters of the delivery of chest compressions (CC) for infants and children are largely consensus based. Of the two recommended depth targets - 1.5 inches and 1/3 anterior-posterior chest diameter (APD) - it is unclear whether these have equal potential for injury. In previous experiments, our group showed in an animal model of pediatric asphyxial out-of-hospital cardiac arrest (OHCA; modeling ∼ 7 year-old children) that 1/3 APD resulted in significantly deeper CC and a higher likelihood of life-threatening injury. We sought to examine and compare injury characteristics of CC delivered at 1.5 inches or 1/3 APD in an infant model of asphyxial OHCA.

METHODS

Swine were sedated, anesthetized, paralyzed, intubated through direct laryngoscopy, and then mechanically ventilated (10 ml/kg, FiO2:21%). APD was measured and confirmed by two investigators via a sliding T-square at the xiphoid. After instrumentation for vital signs monitoring, and while still anesthetized, the endotracheal tube was manually occluded to induce asphyxia, and occlusion was maintained for 9 min. Animals were then randomized to receive CC with a depth of 1.5 inches (Group 1) or 1/3 APD (Group 2), both with a rate of 100 per minute. Advanced life support drugs were administered at 13 min, and defibrillation at 14 min. Resuscitation continued until return of spontaneous circulation (ROSC) or 20 min of failed resuscitation. Survivors were sacrificed with KCl after 20 min of observation. Veterinary staff conducted necropsy to assay lung injury, rib fracture, hemothorax, airway bleeding, great vessel dissection, and heart/liver/spleen contusion. Injury characteristics were summarized and compared via Chi-Squared test or Mann-Whitney U-test using an alpha = 0.05.

RESULTS

A total of 36 animals were included for analysis (Group 1: 18; Group 2: 18). Mean (SD) APD overall was 5.58 (0.23) inches, yielding a mean 1/3 APD depth of 1.86 inches. APD did not differ between groups. ROSC rates did not differ between groups. No injury characteristics differed significantly between groups.

CONCLUSIONS

In an swine model of infant asphyxial OHCA and resuscitation considering 1/3 APD or 1.5 inches, neither CC depth strategy was associated with increased injury.

Chest Compression Depth Targets in Critically Ill Infants and Children Measured With a Laser Distance Meter: Single-Center Retrospective Study From Japan, 2019-2022

OBJECTIVES

Current resuscitation guidelines recommend target chest compression depth (CCd) of approximately 4cm for infants and 5cm for children. Previous reports based on chest CT suggest these recommended CCd targets might be too deep for younger children. Our aim was to examine measurements of anterior-posterior chest diameter (APd) with a laser distance meter and calculate CCd targets in critically ill infants and children.

DESIGN

A retrospective descriptive study.

SETTING

Single-center PICU, using data from May 2019 to May 2022.

PATIENTS

All critically ill children admitted to PICU and under 8 years old were eligible to be included in the retrospective cohort.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The chest APd measurements using a laser distance meter are part of our usual practice on the PICU. Target CCd and the over-compression threshold CCd for each age group was calculated as 1/3 and 1/2 of APd, respectively. In 555 patients, the median (interquartile range) of the calculated target CCd for each age group was: 2.7 cm (2.5-2.9 cm), 2.9 cm (2.7-3.2 cm), 3.2 cm (3-3.5 cm), 3.4 cm (3.2-3.6 cm), 3.4 cm (3.2-3.6 cm), 3.6 cm (3.4-3.8 cm), 3.6 cm (3.4-4 cm), and 4 cm (3.5-4.2 cm), for 0, 2, 3-5, 6-8, 9-11, 12-17, 18-23, 24 to less than 60, and 60 to less than 96 months, respectively. Using guideline-recommended absolute CCd targets, 4 cm for infants and 5 cm for children, 49% of infants between 0 and 2 months, and 45.5% of children between 12 and 17 months would be over-compressed during cardiopulmonary resuscitation.

CONCLUSIONS

In our cohort, the 1/3 CCd targets calculated from APd measured by laser meter were shallower than the guideline-recommended CCd. Further studies including evaluating hemodynamics during cardiopulmonary resuscitation with these shallower CCd targets are needed.

Ventricular fibrillation waveform properties influenced by thoracic impedance guided chest compressions in a porcine model

BACKGROUND AND OBJECTIVE

Quantitative measures extracted from ventricular fibrillation (VF) waveform reflect the metabolic state of the myocardium and are associated with survival outcome. The quality of delivered chest compressions during cardiopulmonary resuscitation are also linked with survival. The aim of this research is to explore the viability and effectiveness of a thoracic impedance (TI) based chest compression (CC) guidance system to control CC depth within individual subjects and influence VF waveform properties.

METHODS

This porcine investigation includes an analysis of two protocols. CC were delivered in 2 min episodes at a constant rate of 110 CC min-1. Subject-specific CC depth was controlled using a TI-thresholding system where CC were performed according to the amplitude (ZRMS, 0.125 to 1.250 Ω) of a band-passed TI signal (ZCC). Protocol A was a retrospective analysis of a 12-porcine study to characterise the response of two VF waveform metrics: amplitude spectrum area (AMSA) and mean slope (MS), to varying CC quality. Protocol B was a prospective 12-porcine study to determine if changes in VF waveform metrics, due to CC quality, were associated with defibrillation outcome.

RESULTS

Protocol A: A directly proportional relationship was observed between ZRMS and CC depth applied within each subject (r = 0.90; p <0.001). A positive relationship was observed between ZRMS and both AMSA (p <0.001) and MS (p <0.001), where greater TI thresholds were associated with greater waveform metrics.

PROTOCOL B

MS was associated with return of circulation following defibrillation (odds ratio = 2.657; p = 0.043).

CONCLUSION

TI-thresholding was an effective way to control CC depth within-subjects. Compressions applied according to higher TI thresholds evoked an increase in AMSA and MS. The response in MS due to deeper CC resulted in a greater incidence of ROSC compared to shallow chest compressions.

Preclinical Efficacy and Selectivity of Vaccines Targeting Fentanyl, Alfentanil, Sufentanil, and Acetylfentanyl in Rats

The ongoing public health emergency of opioid use disorders (OUD) and overdose in the United States is largely driven by fentanyl and its related analogues and has resulted in over 75 673 deaths in 2021. Immunotherapeutics such as vaccines have been investigated as a potential interventional strategy complementary to current pharmacotherapies to reduce the incidence of OUD and opioid-related overdose. Given the importance of targeting structurally distinct fentanyl analogues, this study compared a previously established lead conjugate vaccine (F₁-CRM) to a series of novel vaccines incorporating haptens derived from alfentanil and acetylfentanyl (F_{8, 9a, 9b, 10}), and evaluated their efficacy against drug-induced pharmacological effects in rats. While no vaccine tested provided significant protection against alfentanil, lead formulations were effective in reducing antinociception, respiratory depression, and bradycardia elicited by fentanyl, sufentanil, and acetylfentanyl. Compared with control, vaccination with F₁-CRM also reduced drug levels in the brain of rats challenged with lethal doses of fentanyl. These data further support investigation of F₁-CRM as a candidate vaccine against fentanyl and selected analogues.