Study Design

Reduced Quality Factors

0 = no serious, - = serious,

- - = very serious

Positive Quality Factors

0 = none, + = one, ++ = multiple

Dichotomous Outcome Summary

Non-Dichotomous Outcome Summary

Brief description

Overall Quality

High, moderate, low,
very low, none

No of studies

Study Type

RoB

Indirectness

Imprecision

Inconsistency

Large Effect

Dose-Response

Confounder

# Intervention with Outcome

# Control with Outcome

RR (95% CI)

Outcome: Favorable neurologic outcome

0

N/A

Outcome: Survival to discharge

1

OBS

0

- -

0

0

+

+

0

Human clinical study - modeling depicted a decrease in survival to hospital discharge of 14% for every 5-second increase in perishock pause interval up to 50 seconds.

Low

1

EXP

0

- -

-

0

+

0

0

In a rodent model of ventricular fibrillation longer perishock pauses were associated with lower 24-h (but not 48-h) survival

Very low

Outcome: ROSC

2

OBS

0

- -

0

0

+

0

0

In two human observational studies of ventricular fibrillation, both found that longer peri-shock pauses were associated with decreased odds of ROSC.

Very low

2

EXP

0

- -

-

0

+

+

0

In a rodent and swine model of ventricular fibrillation longer perishock pauses were associated with lower rates of ROSC

Low

Introduction

Maintaining high quality chest compressions (CCs) is considered essential for successful CPR but interruptions to CCs are required to perform ECG rhythm checks, defibrillation, and other clinical interventions. Pauses in CCs can lead to reductions in coronary and cerebral blood flow and lead to worse survival outcomes from CPR.1 The current human CPR guidelines emphasize minimizing the hands-off time and limiting peri-shock pauses to less than 10 seconds.2 There were no specific recommendations for duration of pause in CCs in the previous veterinary guidelines.3

Consensus on science

For the most critical outcome of Favorable neurologic outcome, we identified no studies that address the PICO question.

Outcome 2: Survival to discharge

For the critical outcome of Survival to discharge, we found 1 observational study and 1 experimental study that address the PICO question. In the observational study in people, (Low quality of evidence, downgraded for very serious indirectness, upgraded for large magnitude of effect and for dose-response effect) that addresses the PICO question.4 Using log-linear modeling, this study in people with OHCA and a shockable rhythm showed a decrease in survival to hospital discharge of 14% for every 5-second increase in length of peri-shock pause up to 50 seconds.4 In an experimental rodent study (Very low quality of evidence, downgraded for very serious indirectness and serious imprecision, upgraded for large magnitude of effect), 25 rats underwent 4 minutes of fibrillatory arrest followed by 6 minutes of precordial compressions. Compressions were stopped and followed by a 0-,10-, 20-, 30-, or 40-second pause before electrical defibrillation. Survival to 24 hours was 80% for rats with immediate defibrillation, 40% for those with a 10-second pause prior to defibrillation, and 0% (P< 0.05 compared to immediate defibrillation) for those with 20-, 30-, or 40-second pauses prior to defibrillation; no significant difference in 48-hour survival was found among groups.5

Outcome 3: ROSC

For the critical outcome of ROSC, we identified 2 observational and 2 experimental studies that address the PICO question. The 2 observational studies were in adult people experiencing OHCA with shockable rhythms4,6 (very low quality of evidence, downgraded for very serious indirectness, upgraded for large magnitude of effect). In 35 adult people experiencing ventricular fibrillation, multivariate logistic regression analysis showed an adjusted odds ratio (95% CI) for ROSC of 13.07 (3.42–49.94) with a pre-shock interval of < 3 seconds and post shock interval of < 6 seconds (total pause < 9 seconds) compared to a total pause of ≥ 9 seconds.6 Using log-linear modeling, another study in 815 people with OHCA and a shockable rhythm showed the odds ratio (95% CI) of ROSC was 0.52 (0.27–0.97) with a peri-shock pause of ≥ 40 seconds compared to a peri-shock pause of < 20 seconds.4 Two experimental studies were identified, one in rodents and one in swine5,7 (low quality of evidence, downgraded for very serious indirectness and serious imprecision, upgraded for large magnitude of effect and for dose-response effect). In one study, 25 rats underwent 4 minutes of fibrillatory arrest followed by 6 minutes of precordial compressions. Compressions were stopped and followed by a 0-, 10-, 20-, 30-, or 40-second pause before electrical defibrillation. Following defibrillation, ROSC was achieved in 100%, 60%, 60%, 20% (P< 0.05 compared to immediate defibrillation) and 0% (P< 0.01 compared to immediate defibrillation) animals, respectively.5 In an experimental study including 60 pigs with a fibrillatory arrest model, a peri-shock pause in compressions of 40 seconds was associated with significantly worse ROSC than was a peri-shock pause between 0 and 20 seconds.7

Evidence (some available in 1965) was not summarized for Outcome 4: Surrogate markers of perfusion because of the evidence available for the more critical outcomes above.

Treatment recommendation

We recommend minimizing pauses between compression cycles (< 10 seconds) in dogs and cats during CPR.(strong recommendation, low quality of evidence)

Justification of treatment recommendation

Evidence in multiple species in different settings show that the longer duration of pause in CCs, the less likely to achieve Survival or ROSC. It should be noted that all available data are in ventricular fibrillation arrest scenarios; however, the physiology occurring during pauses that would worsen outcome is likely similar regardless of ECG diagnosis and support minimizing pause duration. In addition, higher CC fractions during CPR (i.e., minimizing hands-off time - not specifically addressed in this PICO question) have been associated with improved outcomes.8 Minimizing pause duration increases CC fraction, which lends additional support to the treatment recommendation.

Knowledge gaps

The ideal CC pause duration during which to evaluate the ECG during CPR in dogs and cats is unknown.