12 April 2017

Birthing Emergencies

Summarized from "Emergency Interception During Parturition in the Dog and Cat," Frances O. Smith, Vet Clin Small Anim 42(2012): 489-499

There are 3 stages of birthing:
Stage 1: uterine contractions and cervical dilation -- usually 6-12 hrs, but maybe up to 36 hrs.  Queen is restless, may pant, refuses food, nests
Stage 2: fetal expulsion -- usually 4 to 16 hrs, with occasionally upto 42 hrs.
Stage 3: placental expulsion -- usually each placenta is passed within 15 minutes of the fetus

Dystocia (difficult birth) occurs 3.3% to 5.8% in feline births.  Clinical signs include:
-- pregnant queen >71 days after breeding
-- straining for 1 hr continuously before delivering
-- green or black vaginal discharge before delivery
-- resting over 3 hrs between births
-- delivery of stillborn
-- protrusion of fetal membranes for over 15 minutes without delivery of fetus
-- vaginal hemorrhage
-- weak or distressed queen

Causes of dystocia can be divided between problems with the queen and problems with the fetuses.  67.1% are of maternal origin and 29.7% are of fetal origin.  [and no the numbers don't add up, but I didn't write the article!]

Fetal causes:
-- malpresentation (the most common fetal problem) -- 70% of kittens are born head first, and while butt-first is not abnormal in cats, it does increase the risk of death.
-- fetal abnormalities
-- fetal death
-- fetal oversize
-- anasarcous fetuses (fluid filled fetuses)

Maternal causes:
-- uterine inertia (the most common maternal problem) -- Primary inertia, the queen has little to no contractions and does not reach Stage 2.  Partial primary, the queen reaches Stage 2 but the contractions are too weak to expel a fetus.  Secondary inertia arises from anatomic problems.  The uterus may become exhausted in the case of obstructed birth canal.
-- pelvic fracture
-- uterine torsion -- Abdomen is very painful with a racing heart beat.
-- vaginal abnormalities such as bands
-- malnutrition
-- parasites

Medical management
If the queen has not been in labor too long, the cervix is dilated, fetal size is appropriate, and the fetal heart rate is normal, then the use of drugs may help.  Drugs should NOT be used in cases of obstruction or when more than 1 fetus remains in utero due to uterine fatigue. 
-- oxytocin increases the frequency and quality of contractions.  Doses range from 2 to 4 U IM, with a recommended dose of 0.5 to 2 U.  The author spcifies an initial dose of 0.1 U/kg, with a repeat dose after 30 minutes, and no further use after that.  (Oxytocin will cause placental separation and lead to fetal distress.)
-- calcium increases the contractions but "in the queen, calcium use is controversial, due to the very strong uterine contractions seen when it is administered".  [I'm planning on looking into this frther.]

Mechanical management
In the case of malpositioning, it is possible to use sterile lubricant and fingers to rotate and extract the fetus.  Otherwise an episiotomy is possible, but with the complication of scarring and increased risks for future pregnancies.

Surgical management
60-80% of all dystocias result in surgery.  Fetal heartrates below 150 beats/min require immediate surgery, and 150-170 should be monitored closely as surgery is prepared for.  The author does not recommend an ovariohysterectomy at the time of a ceasarean, unless the uterus is damaged, due to risk of hemorrhage and loss of fluids. [skipped all the discussion of anesthetics and surgery as this is not a DIY project, hopefully]

The accompanying flowchart shows neonatal resuscitation.  While it is for neonates after a ceasarean, much of it does apply to normally born kittens too.

11 April 2017

Feline Gestation

Summarized from "Current Advances in Gestation and Parturition in Cats and Dogs", Catherine G. Lamm, Chelsea L. Makloski, Vet. Clinics Sm Animal 42(2012) 445-456

In cats, the normal gestation range is given as 52-74 days, depending on the breed.  As cats are induced ovulators, the luteinizing hormone only surges 24-40 hrs after copulation.  If the copulation is not observed, it is difficult to determine when ovulation occurs.

After 5 days (post breeding) the fertilized ovum enters the uterus with the outer layer (zona pelucida) being shed 10-12 days after breeding.  Implantation occurs at 12-13 days.  Heart beats can be detected at 16 to 25 days.

Pregnancy diagnosis can be made by palpation for the gestational sacs 21-25 days post breeding.  After 35 days, however, the sacs flatten and palpation becomes more difficult.

Ultrasound is the most sensitive and reliable method of pregnancy detection.  With skilled technicians, fetal structures can be detected 11-17 days post breeding.  It is less reliable to determine the number of fetuses.  Heart rates can be monitored from day 25 onwards, and should be greater than 193 beats/min.  Fetal movement can be observed at 28 days.  After 40 days, the gestational age can be estimated using the foloowing two formulas:

Age = (25 x head diameter cms) + 3
Age = (11 x body diameter cms) +21

Mineralization occurs at 38-40 days.  Xrays can then be used to determine the number of fetuses.  Once mineralization begins, age of the fetuses can be estimated as seen in the table.

Use of hormones to determine pregnancy is dependent on the hormone.  Progesterone is not reliable.  Relaxin is specific to pregnancy as early as about 25 days.  Prolactin is not reliable as it will spike in pseudopregnant animals.

Unlike in dogs, queens need a slow increase in calories beginning at 14 days.

Queens may have normocytic, normochromic anemia as well as mild neutrophilia.  Other changes in bloodwork include decrease in proteins, increase in lactate dehydrogenase, increase in cholesterol, and decrease in creatinine. 

For high risk pregnancies, monitoring of progesterone levels should be used.  If a decrease in progesterone level is seen, females can enter pre-term labor, which may be stopped with exogenous progesterone or terbutaline.

Termination of pregnancies can be done either by spaying or, if fertility needs to be maintained, by using a variety of compounds such as estradiol cypionate.