Outcome:

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: Survival to Discharge, No evidence identified

0

NA

Outcome: Favorable Neurologic Outcome, No evidence identified

0

NA

Outcome: Oxygenation, No evidence identified

0

NA

Outcome: PaCO2, No evidence identified

0

NA

Outcome: Hospital Length of Stay, No evidence identified

0

NA

Outcome: Histopathologic Damage, No evidence identified

0

NA

Introduction

Heart rate (HR) is an important vital sign used to determine both the need for and the response to resuscitation measures at birth in people.( Wyckoff et al, 2020) Bradycardia in newborns results from hypoxia through a combination of vagal and non-vagal mechanisms.( Giussiani, 1993) Transitional newborn cats and dogs that both remain bradycardic and are not adequately breathing despite initial resuscitation steps will require PPV to support clearance of lung fluid, establishment of functional residual capacity and improvement of oxygenation and ventilation.( Bruckner and Schmoelzer, 2021) The current recommendation in human newborn resuscitation is based on expert opinion and is to institute positive pressure ventilation (PPV) when HR is <100 beats/min or the newborn is gasping or apneic.( Wyckoff et al, 2020) On the other hand, PPV adds technical complexity to the resuscitation procedure, and can be challenging in dogs and cats because they are multiparous species with the potential for several newborns requiring resuscitation concurrently. A HR cut-off that is too high might unnecessarily divert resuscitation efforts from other newborns in need, while a cut-off that is too low could delay administration of critical PPV and negatively impact outcome.

Consensus on science

We found no relevant evidence addressing this PICO question for any of the outcomes.

Treatment recommendation

We recommend initiating PPV in non-vigorous newborn dogs and cats with cleared upper airways that are bradycardic (strong recommendation, expert opinion).

We suggest using a heart rate below 120 beats/minute as the threshold for initiating PPV in non-vigorous newborn dogs and cats with cleared upper airways (weak recommendation, expert opinion).

We recommend starting PPV as early as possible in non-vigorous dogs and cats that are gasping or are apneic, regardless of the heart rate (strong recommendation, expert opinion).

Justification of treatment recommendation

All newborns are expected to experience hypoxia during transition. In newborn full-term infants, the median initial SpO2 value at 1 minute after birth was found to be 65% and the majority of newborns did not surpass an SpO2 of >90% until 10 minutes after birth. (Badurdeen, 2022) Consequently, a low HR is commonly present immediately after birth. In babies, the average HR 2 seconds after birth was around 120 beats/min and highly variable, but increased to 149+/-33 beats/minute within the first 40 seconds of birth.( Linde 2016) Groppetti and colleagues reported an average HR in puppies at birth (n=94) as 129+/-50 beats/min that increases to 210+/-21 beats/min over the first 24 hours (Groppetti, 2010). Apgar scores developed for puppies indicate a HR of at least 180 beats/min as normal; however, the first Apgar scores are typically taken within the first 5 minutes and not immediately after birth.( Batista 2014; Veronesi, 2016) Thus, we believe that a low HR immediately after birth is of little concern if the newborn puppy or kitten is vigorous (i.e., breathing, crying and with good muscle tone) and the HR is expected to increase markedly over the next 1-2 minutes. However, in animals that are non-vigorous (i.e., low or absent muscle tone, apneic, or gasping) a low HR indicates the need for PPV as early as possible within the first minute after birth. As we were unable to identify any evidence to support a specific HR cut-off for initiation of PPV, the committee decided based on the high normal HR in fully transitioned puppies or kittens to set the HR threshold at 120 beats/min. Regardless of HR, the committee acknowledges that delivery of effective ventilation is a critical support measure for animals with inadequate transition. We therefore recommend PPV be initiated within the first minute after birth in apneic or gasping newborns independent of the HR if clearing the airway and tactile stimulation do not immediately lead to a response. With effective PPV a gradual increase in HR over 15 - 60 seconds may be expected. (Espinoza, 2019)

Knowledge gaps

The HR below which to institute PPV in newborn dogs and cats with hypoxia-related bradycardia is not known but is difficult to study as it likely changes with the time that elapsed since birth. Thus, it would be first important to fully describe the time course of HR change in normally transitioning puppies and kittens from the moment of birth and over the first few minutes, ideally capturing these HRs in 10-second steps. In addition, the temporal course of HR in response to early PPV in newborn dogs and cats and its impact on outcome have not been described.