Page 617 - Cote clinical veterinary advisor dogs and cats 4th

280 Dystocia

Formulas for Predicting Gestational Age and Days Before Parturition
VetBooks.ir Gestational Age in Dogs (± 3 Days)* Gestational Age in Cats (± 2 Days)*
Less Than 40 Days
†
CRL = 0.2423 × GA − 4.2165
GA = (6 × GSD) + 20
GA = (3 × CRL) + 27
Greater Than 40 Days †
GA = (15 × HD) + 20 GA = 25 × HD + 3
GA = (7 × BD) + 29 GA = 11 × BD + 21
GA = (6 × HD) + (3 × BD) + 30
Days Before Parturition ‡
DBP = 65 − GA DBP = 61 − GA
DYSTOCIA Uterine contractions are being
*Gestational age (GA) is based on days after the luteinizing hormone (LH) surge in the dog and days after breeding in the cat. recorded from this prepartum bitch using veterinary
† Gestational sac diameter (GSD), crown-rump length (CRL), head diameter (HD), and body diameter (BD) measurements are in centimeters. tocodynamometry.
‡ Number of days before parturition (DBP) is based on 65 ± 1 days after the LH surge in the dog and 61 days after breeding in the cat.
Modified from Nyland TG, et al: Small animal diagnostic ultrasound, ed 2, Philadelphia, 2002, Saunders.
• Minimize fetal stress; neonatal death (fading ○ Although most dams are eucalcemic, ○ Elevation of the bitch’s forequarters can
puppy/kitten) during the first week of life the benefit of calcium administration assist in manipulation of the fetus in the
is related to stress during labor and the on myometrial contractility is still seen, birth canal.
immediate postpartum period. suggesting a cellular or subcellular effect.
• Avoid fetal or maternal mortality. • Oxytocin Chronic Treatment
• Preserve the reproductive capacity of a ○ Give 10-15 minutes after administration Medical therapy for dystocia, based on the
valuable dam. of calcium if delivery has not occurred. administration of calcium gluconate and
• Ovariohysterectomy at the time of cesarean ○ The administration of oxytocin increases oxytocin, can be directed and tailored based
section is not advised unless indicated by the frequency of uterine contractions, on the results of tocodynamometry.
the condition of the uterus (necrotic, whereas the administration of calcium
hemorrhagic) because surgery/anesthesia increases their strength. Drug Interactions
is prolonged, hypovolemia is exacerbated, ○ Oxytocin (10 USP units/mL) is most Calcium is given before oxytocin in most cases,
and lactation without estrogen can be effective at mini doses: start with 0.25 improving contractile strength before increasing
problematic. units/dose SQ or IM to a maximal dose frequency of contractions.
of 4 units per bitch or 1 unit per queen.
Acute General Treatment IV oxytocin is not advised in the bitch Possible Complications
• Supportive: intravenous (IV) balanced or queen. • Hypercalcemia-induced arrhythmias can
electrolyte solution with 5% dextrose if ○ The frequency of oxytocin administration result if calcium gluconate is given intrave-
appropriate (dam is often hypovolemic, is dictated by the labor pattern, and it is nously at too rapid a rate.
dehydrated, or hypoglycemic) generally not given more frequently than • Fetal hypoxia secondary to placental compres-
• Evaluate indications for medical therapy every 30-60 minutes. sion during uterine contractions induced
(p. 1415). ○ Uterine contractions compromise placental by parenteral oxytocin administration,
○ Without tocodynamometry, evaluation blood flow and cause fetal hypoxia. Exces- particularly if given inappropriately (e.g.,
of fetal heart rates before and after sive contractions (due to uterine hyperto- too early in labor, when fetal obstruction
administration of calcium gluconate nicity, overdosage of oxytocin, obstruction) is present, if uterine torsion is present, too
and oxytocin is important. Worsening can compromise fetal survival. Uterine frequently) or at excessive doses
bradycardia dictates surgical intervention. relaxation between contractions allows • Uterine rupture, with fetal and maternal
• Calcium: calcium gluconate 10% solution normal placental blood flow to resume. morbidity and mortality if ecbolic agents
(≈10 g/100 mL solution, or 0.465 mEq ○ Absolute contraindications to oxytocin (oxytocin) are given excessively, inap-
2+
Ca /mL) therapy: fetal obstruction in any part of propriately (too early in labor, when fetal
○ Give first (before oxytocin); even if the uterus or birth canal, uterine torsion, obstruction is present, if uterine torsion
eucalcemic (see below) uterine laceration or rupture. is present, too frequently, too rapidly),
○ Given SQ at 1 mL/4.5 kg (10 lb) body • Persistence of a fetus in the birth canal or when the uterine wall is compromised
weight as indicated by the strength of beyond 5-10 minutes warrants assisted or torn
uterine contractions, usually not more delivery.
frequently than every 4-6 hours during ○ Placental separation and the potential for Recommended Monitoring
the second stage of labor. CAUTION: fetal hypoxemia are likely. • Progression of labor with viable neonates
large volumes of calcium gluconate ○ CAUTION: Traction applied to a fetus delivered
given subcutaneously may cause local retained in the birth canal must be very • Using real-time transabdominal ultrasonog-
irritation or even skin necrosis; doses > gentle to avoid fetal trauma. raphy or a fetal Doppler, fetal heart rates
6 mL should be divided. More concen- ○ Traction is advised only if the veterinarian should be > 180-200 beats/min with only
trated forms of calcium gluconate are not can position his/her fingers around the transient decelerations.
advised. fetal shoulders or hips for gentle traction • Sustained fetal heart rates < 180 beats/min
○ Intravenous use: generally unnecessary in a downward direction along the plane are associated with fetal distress.
unless systemic signs of severe hypocal- of the vagina and vestibule. • Continued uterine monitoring using
cemia are present; see Hypocalcemia, ○ Lubrication delivered by a red rubber tocodynamometry, showing continuation
(p. 515) for signs of hypocalcemia and catheter and water-soluble lubricant jelly and progression of appropriate contractile
intravenous calcium gluconate doses. can be helpful. strength and frequency

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