Evaluation of end-tidal carbon dioxide as a predictor of return of spontaneous circulation in dogs and cats undergoing cardiopulmonary resuscitation

2024 RECOVER Guidelines: Monitoring. Evidence and knowledge gap analysis with treatment recommendations for small animal CPR

OBJECTIVE

To systematically review evidence on and devise treatment recommendations for patient monitoring before, during, and following CPR in dogs and cats, and to identify critical knowledge gaps.

DESIGN

Standardized, systematic evaluation of literature pertinent to peri-CPR monitoring following Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methodology. Prioritized questions were each reviewed by Evidence Evaluators, and findings were reconciled by Monitoring Domain Chairs and Reassessment Campaign on Veterinary Resuscitation (RECOVER) Co-Chairs to arrive at treatment recommendations commensurate to quality of evidence, risk:benefit relationship, and clinical feasibility. This process was implemented using an Evidence Profile Worksheet for each question that included an introduction, consensus on science, treatment recommendations, justification for these recommendations, and important knowledge gaps. A draft of these worksheets was distributed to veterinary professionals for comment for 4 weeks prior to finalization.

SETTING

Transdisciplinary, international collaboration in university, specialty, and emergency practice.

RESULTS

Thirteen questions pertaining to hemodynamic, respiratory, and metabolic monitoring practices for identification of cardiopulmonary arrest, quality of CPR, and postcardiac arrest care were examined, and 24 treatment recommendations were formulated. Of these, 5 recommendations pertained to aspects of end-tidal CO2 (ETco2) measurement. The recommendations were founded predominantly on very low quality of evidence, with some based on expert opinion.

CONCLUSIONS

The Monitoring Domain authors continue to support initiation of chest compressions without pulse palpation. We recommend multimodal monitoring of patients at risk of cardiopulmonary arrest, at risk of re-arrest, or under general anesthesia. This report highlights the utility of ETco2 monitoring to verify correct intubation, identify return of spontaneous circulation, evaluate quality of CPR, and guide basic life support measures. Treatment recommendations further suggest intra-arrest evaluation of electrolytes (ie, potassium and calcium), as these may inform outcome-relevant interventions.

Usability of EtCO2 values in the decision to terminate resuscitation by integrating them into the TOR rule (an extended TOR rule): A preliminary analysis

Objective

End tidal carbon dioxide (EtCO2) is measured to confirm the placement of an endotracheal tube and evaluate the efficacy of cardiopulmonary resuscitation (CPR), and as an assistive tool for terminating CPR. However, there are no highly accurate or definitive recommendations for its use when deciding on the termination of CPR. We aimed to merge EtCO2 values with existing termination of resuscitation (TOR) rules to obtain a more accurate combination for terminating resuscitation.

Methods

This observational, prospective study included non-traumatic adult patients who were admitted to a tertiary university hospital Emergency Medicine Department due to cardiac arrest. EtCO2 cutoff values (at 5, 10, and 20 min) were integrated into currently used TOR parameters (arrest was not witnessed, no bystander CPR was provided, no return of spontaneous circulation (ROSC) after full advanced life support care in the field, and no shock was delivered) and the extended TOR rule was created. These extended TOR rules were compared at three different times (5, 10, and 20 min) for specificity and positive predictive value for ROSC.

Results

We included a total of 86 cases. The cutoff value of EtCO2 from ROC analysis was 19.5, 23.5, and 20.5 mmHg at 5, 10, and 20 min, respectively. "The extended TOR rule created with the 20-min EtCO2 cutoff (20.5 mmHg) was the most accurate in detecting ROSC (-) patients. The specificity was 100% (95% CI 63.1-100.0) sensitivity was 20.0% (95% CI 9.1-35.7), positive predictive value was 100% and negative predictive value was 20.0% (95% CI 17.6-22.6) for ROSC (-) patients. The parameters of this rule were as follows: arrest was not witnessed, no bystander CPR was provided, no ROSC after full advanced life support care in the field, no shock was delivered, and EtCO2 value at 20 min of resuscitation <20.5 mmHg.

Conclusions

Integration of EtCO2 values into the classically used TOR criteria increases the specificity to 100% without a significant decrease in sensitivity. These results need to be validated in larger groups before this rule is used clinically. EtCO2 seems to be a beneficial tool in establishing new TOR rules.

Reassessment Campaign on Veterinary Resuscitation (RECOVER) Initiative small animal CPR registry report 2016-2021

OBJECTIVE

To introduce the Reassessment Campaign on Veterinary Resuscitation (RECOVER) CPR registry and report cardiopulmonary arrest (CPA) and CPR event data collected to date.

DESIGN

International, multi-institutional veterinary CPR registry data report.

SETTING

Veterinary private practice and university teaching hospitals.

ANIMALS

Data from 514 dogs and 195 cats undergoing CPR entered in the RECOVER CPR registry between February 2016 and November 2021.

INTERVENTIONS

The RECOVER CPR registry is an online medical database created for standardized collection of hospital, animal, arrest, and outcome information on dogs and cats undergoing CPR. Data were collected according to the veterinary Utstein-style guidelines for standardized reporting of in-hospital CPR in dogs and cats. Case records were downloaded, duplicate and incomplete cases were removed, and summary descriptive data were reported.

MEASUREMENTS AND MAIN RESULTS

Sixteen hospitals in the United States, Europe, and Australia contributed data on 709 CPR events to the registry. One hundred and forty-two (28%) dogs and 58 (30%) cats attained return of spontaneous circulation (ROSC), 62 (12%) dogs and 25 (13%) cats had ROSC >20 minutes, and 14 (3%) dogs and 4 (2%) cats survived to hospital discharge. The reason for CPR discontinuation was reported as owner choice in 321 cases (63%). The most common suspected causes for CPA were respiratory failure (n = 142, 20%), heart failure (n = 86, 12%), and hemorrhage (n = 76, 11%).

CONCLUSION

The RECOVER CPR registry contains the first multicenter data set on small animal CPR. It confirms poor outcomes associated with CPA, emphasizing the need for large-sized studies to gain adequate information on characteristics associated with favorable outcomes.

Feline cardiopulmonary resuscitation: Getting the most out of all nine lives

PRACTICAL RELEVANCE

Cardiopulmonary arrest (CPA) can occur in any veterinary or animal care setting and is a particular risk in scenarios involving ill, injured or anesthetized patients. Education of all staff on the prevention and recognition of CPA, as well as the performance of cardiopulmonary resuscitation (CPR), is vital to influencing outcome.

EVIDENCE BASE

While there is a plethora of information regarding CPA and CPR in human medicine, there are comparably few studies in the veterinary literature. Many of the current veterinary guidelines are extrapolated from human medicine or studies based on animal models. Ongoing work is needed to tailor guidelines and recommendations to our domestic feline (and canine) patients in a clinical setting.

AIM

The aim of this article, which is intended for veterinarians in all areas of small animal practice, is to provide an evidence-based review of CPA and CPR in feline patients. The authors have drawn heavily on detailed recommendations published by the Reassessment Campaign on Veterinary Resuscitation (RECOVER) initiative - one of the few resources specific to the veterinary clinical setting - as well as reviewing the available peer-reviewed literature studies, in constructing this article. Among the topics discussed are recognizing and preventing CPA, staff training and clinic preparedness, basic life support and advanced life support interventions, and appropriate post-cardiac arrest care.

Modified volumetric capnography-derived parameter: A potentially stable indicator in monitoring cardiopulmonary resuscitation efficacy in a porcine model

AIM

We aimed to investigate whether the ability of the volumetric capnography-derived parameter, the volume of CO₂ eliminated per minute and per kg body weight (V'CO₂ kg^-1), in monitoring the quality of CPR and predicting the return of spontaneous circulation (ROSC) remains undisturbed by hyperventilation.

METHODS

This randomised crossover study included 12 male domestic pigs. After 4 min of untreated ventricular fibrillation, mechanical CPR was administered. Following 5-min washout periods, each animal underwent two sessions of experiments; four 5-min ventilation trials followed by advanced life support, consecutively in the two sessions.

RESULTS

Different ventilation types had no significant impact on V'CO₂ kg^-1 or haemodynamics. However, PETCO₂ was significantly affected by the ventilation type and coronary perfusion pressure (P < 0.05). The means ± standard deviations of PETCO₂ decreased linearly with an increase in the respiratory rate (RR) (P < 0.05). The PETCO₂ decreased from 20.42 ± 9.51 to 16.16 ± 5.07 (P < 0.05) as the tidal volume increased from 10 to 20 mL min^-1. No significant differences in V'CO₂ kg^-1 were observed between the three RR levels of ventilation types (P = 0.274). Post hoc analysis demonstrated a significant difference between the highest value of V'CO₂ kg^-1 in double tidal volume hyperventilation and normal ventilation and triple respiratory rate hyperventilation (P < 0.05). The AUC for V'CO₂ kg^-1 and PETCO₂ in discriminating between survivors and non-survivors was 0.80 and 0.71, respectively.

CONCLUSIONS

V'CO₂ kg^-1 performs better than PETCO₂ in monitoring the quality of CPR during hyperventilation. In predicting ROSC during variations in a ventilation state, V'CO₂ kg^-1 has good predictive ability.

Prospective Evaluation of Cardiopulmonary Resuscitation Performed in Dogs and Cats According to the RECOVER Guidelines. Part 2: Patient Outcomes and CPR Practice Since Guideline Implementation

Cardiopulmonary resuscitation (CPR) outcomes have not been prospectively described since implementation of the Reassessment Campaign on Veterinary Resuscitation (RECOVER) guidelines. This study aimed to prospectively describe CPR outcomes and document arrest variables in dogs and cats at a U.S. veterinary teaching hospital since implementation of the RECOVER guidelines using the 2016 veterinary Utstein-style CPR reporting guidelines. One-hundred and seventy-two dogs and 47 cats that experienced cardiopulmonary arrest (CPA) underwent CPR following implementation of the RECOVER guidelines and were prospectively included. Supervising clinicians completed a data form for CPR events immediately following completion of CPR from December 2013 to June 2018. Seventy-five (44%) dogs and 26 (55%) cats attained return of spontaneous circulation (ROSC), 45 dogs (26%) and 16 cats (34%) had ROSC ≥ 20 min, 13 dogs (8%) and 10 cats (21%) were alive 24 h after CPR, and 12 dogs (7%) and 9 cats (19%) survived to hospital discharge. The most common cause of death in animals with ROSC ≥ 20 min was euthanasia. Patient outcomes were not significantly different since publication of the RECOVER guidelines except for a higher feline survival to hospital discharge rate. Dogs (p = 0.02) but not cats with initial shockable rhythms had increased rates of ROSC while the development of a shockable rhythm during CPR efforts was not associated with ROSC (p = 0.30). In closed chest CPR an end-tidal carbon dioxide (EtCO₂) value of >16.5 mmHg was associated with a 75% sensitivity and 64% specificity for achieving ROSC. Since publication of the RECOVER guidelines, CPR practice did not clinically significantly change at our institution and no improvement of already high ROSC rates was noted. The percentage of cats surviving to hospital discharge was higher than previously reported and the reason for this improvement is not evident with these results. Euthanasia remains a major confounding factor in assessing intermediate and long-term CPR outcomes in dogs and cats.

Prospective Evaluation of Cardiopulmonary Resuscitation Performed in Dogs and Cats According to the RECOVER Guidelines. Part 1: Prognostic Factors According to Utstein-Style Reporting

Factors associated with positive cardiopulmonary resuscitation (CPR) outcomes defined according to the veterinary Utstein-style CPR reporting guidelines have not been described since implementation of the Reassessment Campaign on Veterinary Resuscitation (RECOVER) CPR clinical guidelines in 2012. The aims of this study were to assess factors associated with positive CPR outcomes at a U.S. veterinary teaching hospital, to re-evaluate these factors since implementation of the RECOVER guidelines compared to reported factors prior to their publication, and to identify potential additional factors since guideline publication. One-hundred and seventy-two dogs and 47 cats that experienced cardiopulmonary arrest (CPA) and had CPR performed were prospectively included in this observational study. Supervising clinicians were asked to complete a data form on CPR events immediately following completion of CPR efforts. Multivariable logistic regression was used to evaluate the effect of twenty hospital, animal, and arrest variables on the three patient outcomes “any return of spontaneous circulation (ROSC),” “sustained ROSC,” and survival to hospital discharge. Cats had significantly higher odds to achieve any ROSC [OR (95%CI) 2.72 (1.12–6.61), p = 0.028] and survive to hospital discharge than dogs [OR (95%CI) 4.87 (1.52–15.58), p = 0.008]. Patients had significantly lower odds of achieving any ROSC if CPA occurred during nighttime hours [OR (95%CI) nighttime = 0.52 (0.27–0.98), p = 0.043], and higher odds if CPA was witnessed [OR (95%CI) 3.45 (1.57–7.55), p = 0.002], if less people were involved in CPR efforts [OR (95%CI) 0.8 (0.66–0.96), p = 0.016], if pulses were palpable during CPR [OR (95%CI) 9.27 (4.16–20.63), p < 0.0005], and if an IV catheter was already in place at the time of CPA [OR (95%CI) 5.07 (2.12–12.07), p = 0.0003]. Odds for survival to hospital discharge were significantly higher if less people were involved in CPR efforts [OR (95%CI) 0.65 (0.46–0.91), p = 0.013] and for patients of the anesthesia service [OR (95%CI) 14.82 (3.91–56.17), p = 0.00007]. Overall, factors associated with improved CPR outcomes have remained similar since incorporation of RECOVER guidelines into daily practice. Witnessed CPA events and high-quality CPR interventions were associated with positive patient outcomes, emphasizing the importance of timely recognition and initiation of CPR efforts. An optimal CPR team size has yet to be determined.

The Compliance of Current Small Animal CPR Practice With RECOVER Guidelines: An Internet-Based Survey

In 2012 the Reassessment Campaign on Veterinary Resuscitation (RECOVER) published evidence-based treatment recommendations for dogs and cats with cardiopulmonary arrest (CPA), to optimize the clinical practice of small animal CPR and positively impact outcomes. Six years after the release of these guidelines, we aimed to determine the compliance of small animal veterinary CPR practices with these RECOVER guidelines. To identify current CPR practices in clinically active small animal veterinarians and their awareness of the RECOVER guidelines, we conducted an internet-based survey. Survey invitations were disseminated internationally via veterinary professional organizations and their social media outlets. Questions explored respondent demographics, CPR preparedness, BLS and ALS techniques and awareness of RECOVER guidelines. Responding small animal veterinarians (n = 770) in clinical practice were grouped by level of expertise: board-certified specialists (BCS, n = 216) and residents (RES, n = 69) in anesthesia or emergency and critical care, practitioners in emergency (GPE, n = 299) or general practice (GPG, n = 186). Large disparities in preparedness measures, BLS and ALS techniques emerged among levels of expertise. Only 32% (95% CI: 29–36%) of respondents complied with BLS practice guidelines, varying from 49% (95% CI: 42–55%) of BCS to 15% (95% CI: 10–20%) of GPG. While incompliances in BCS, RES, and GPE were predominantly due to knowledge gaps, GPG compliance was further compromised by limitations in the resuscitation environment (e.g., defibrillator availability, team size). Those aware of RECOVER guidelines (100% of BCS and RES; 77% of GPE; 35% of GPG) were more likely to comply with recommended preparedness (OR = 2.4; 95% CI: 1.2–4.8), BLS (OR = 4.5; 95% CI: 2.4–9.1), and ALS techniques (OR = 7.8; 95% CI: 2.4–9.1) independent of age, gender, region of practice or level of expertise. We conclude that awareness of RECOVER guidelines is high in specialists and residents, but incomplete among general practitioners. This awareness positively influenced compliance with CPR guidelines, but CPR practices continue to be variable and largely not in agreement with guidelines. A widely accessible educational strategy is required to broadly improve compliance with best practices in small animal CPR.