Evidence-Based Parameters for Intervention in Canine welping

[malernee]

Evidence-Based Parameters for Intervention in Canine Parturition
Australian College of Veterinary Scientists Science Week 2003
Patrick Kenny, BVSc
West Chermside Veterinary Clinic
Stafford Heights, Qld, Australia

Dystocia can be simply defined as abnormal labour or parturition. In many circumstances, however, it can be difficult to differentiate dystocia from eutocia (normal parturition) due to the large variation in what can be considered as normal progression of labour. Hence it can be a challenging task for the clinician in many whelpings to assess whether parturition is progressing normally, whether intervention in necessary, and what the most appropriate form of intervention would be (manipulation, medical, or surgical). Collecting a detailed pre-parturient history and investigating the health of the bitch and the viability of the pups facilitates early decision making, which should lead to earlier and more appropriate interventions and better outcomes. Recent investigations have looked into the endocrine events surrounding parturition, assessing fetal distress using trans-abdominal ultrasound, and the use of tocodynamometry to monitor uterine activity in the bitch.

Gestation length is an inaccurate indicator of impending parturition when measured as the interval between breeding date and parturition due to the considerable variability of this parameter in the dog (57-72 Days). A recent study has investigated serum concentrations of Progesterone (P4) and 15-dihydroPGF2α (a metabolite of PGF2α) in the periparturient period, noting that sudden decreases in P4 and increases in 15-dihydroPGF2α concentrations in the 24 hours prior to parturition would make these two hormones accurate indicators of imminent parturition. This study also found no significant pre-partum decrease in body temperature, questioning the validity of seeking a drop in temperature to herald impending whelping. It did, however, find a statistically significant increase in body temperature beginning 12 hours post partum. Therefore, clinically, any significant increase in body temperature at term gestation without signs of fetal expulsion could signify a problem in the process of parturition.

Ultrasound has a distinct advantage over other imaging modalities in the pregnant bitch in its ability to assess fetal distress. This is most commonly done by measuring fetal heart rate (HR), averaging 220bpm immediately pre-partum. Various authors define fetal stress at varying depressions of HR, however there have been no studies correlating fetal heart rates with outcomes. A recent study has correlated fetal heart rates with ultrasonographic observations of bowel movements. Meconium in the amniotic fluid is used to determine fetal distress in humans, monkeys and sheep, and is necessarily preceded by bowel movements. The study defined HR >220bpm as normal, HR of 180-220bpm as mild fetal distress, and HR<180bpm as severe fetal di, and the use of tocodynamometry to monitor uterine activity in the bitch.

Gestation length is an inaccurate indicator of impending parturition when measured as the interval between breeding date and parturition due to the considerable variability of this parameter in the dog (57-72 Days). A recent study has investigated serum concentrations of Progesterone (P4) and 15-dihydroPGF2α (a metabolite of PGF2α) in the periparturient period, noting that sudden decreases in P4 and increases in 15-dihydroPGF2α concentrations in the 24 hours prior to parturition would make these two hormones accurate indicators of imminent parturition. This study also found no significant pre-partum decrease in body temperature, questioning the validity of seeking a drop in temperature to herald impending whelping. It did, however, find a statistically significant increase in body temperature beginning 12 hours post partum. Therefore, clinically, any significant increase in body temperature at term gestation without signs of fetal expulsion could signify a problem in the process of parturition.

Ultrasound has a distinct advantage over other imaging modalities in the pregnant bitch in its ability to assess fetal distress. This is most commonly done by measuring fetal heart rate (HR), averaging 220bpm immediately pre-partum. Various authors define fetal stress at varying depressions of HR, however there have been no studies correlating fetal heart rates with outcomes. A recent study has correlated fetal heart rates with ultrasonographic observations of bowel movements. Meconium in the amniotic fluid is used to determine fetal distress in humans, monkeys and sheep, and is necessarily preceded by bowel movements. The study defined HR >220bpm as normal, HR of 180-220bpm as mild fetal distress, and HR<180bpm as severe fetal distress. Bowel movements were observed in 40% of pups in the group with mild distress, and 100% of pups with severe distress as defined by heart rate. The study concluded that bowel movements were a reliable indicator of fetal distress in dogs.

Tocodynamometry allows objective assessment of uterine activity and can differentiate normal patterns of contraction, abnormal patterns of contraction and uterine inertia. It may be used in combination with Doppler fetal heart rate monitoring to measure fetal distress and quality of labour simultaneously. A correlation has been shown between length and quality of labour and fetal viability in humans, this presumably being the case in the dog. Intra-partum monitoring of human pregnancies at term has been credited for dramatic reductions in morbidity and mortality.

References

1. Barber JA: Parturition and Dystocia. In: Kustritz MVR (ed): Small Animal Theriogenology. St. Louis, Butterworth-Heinemann, 241-281 (2003).

2. Veronesi MC, Battocchio M, Marinelli, L, Faustini M, Kindahl H, Cairoli F: Correlations Among Body Temperature, Plasma Progesterone, Cortisol and Prostaglandin F2α of the Periparturient Bitch. J. Vet. Med. A 49, 264-268 (2002).

3. Verstegen JP, Silva DM, Onclin K, Donnay I: Echocardiographic Study of Heart Rate in Dog and Cat Fetuses in Utero. Journal of Reproduction and Fertility Supplement. 47, 175-180 (1993).

4. Zone MA, Wanke MM: Diagnosis of Canine Fetal Health by Ultrasonography. Journal of Reproduction and Fertility Supplement. 57, 215-219 (2001).

5. Davidson AP: Uterine and Fetal Monitoring in the Bitch. Vet Clin North Am (Small Anim Pract) 31:305-313 (2001).

Speaker Information
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Patrick Kenny, BVSc
West Chermside Veterinary Clinic
Stafford Heights, Qld, Australia