Biomedical Engineering Reference
In-Depth Information
steps should be taken to place a percutaneous gastrostomy
(PEG) tube before trismus becomes so severe as to not
allow passage of an endoscope. PEG tubes are preferred for
long-term nutritional support because they allow the normal
diet to be fed after the addition of water. Since oropha-
ryngeal muscle function may be compromised in tetanus,
administration directly into the stomach without the need to
pass a tube through the oropharynx is an additional benefit
of using a PEG tube. The section “Gastric dilatation” above
provides more detail on PEG tube use and maintenance.
Hydration is maintained by intravenous or subcutaneous
fluid therapy. Recumbent animals require padded cages and
frequent turning to avoid pressure point necrosis and the
formation of decubital ulcers.
Tetanus is a nonimmunizing disease so multiple
episodes are possible unless animals are vaccinated.
Routine immunization with tetanus toxoid is protective.
Transplacental transfer of antibodies from vaccinated
mothers to infants is documented in humans.
Multiparity may also predispose animals to dystocia,
especially in species where single births are the norm.
The challenge of early detection of dystocia in
nonhuman primates relates to housing conditions and
environment as well as their ability to delay labor and
hide signs of distress until late in the disease process.
Nonhuman primates housed in pairs or small groups in
indoor housing are more easily observed for dystocia
than those housed in large outdoor enclosures and in
free-range naturalistic environments. In these environ-
ments it may not be until the situation has progressed to
a critical stage that signs of dystocia become apparent,
even to the most experienced observer. It is due to these
factors that nonhuman primates presenting with dystocia
are often in critical condition and require immediate
treatment.
Clinical Signs
Clinical signs of dystocia include depression, weakness,
restlessness, and abnormal fetal position, which may be
observed as a tail or limb in the pelvic canal. Vaginal
discharge may be observed if the amniotic membranes have
ruptured. In later stages, animals may be recumbent,
experiencing abdominal muscle contractions, or may be
atonic. Most nonhuman primate species give birth at night
and have the ability to delay labor for several hours if they
feel threatened. Therefore, any female that is in labor during
daylight hours should be observed closely or examined for
signs of dystocia since daylight parturition may indicate
prolonged or abnormal labor that started the previous night.
Dystocia
New World monkeys are especially susceptible to
dystocia due to fetal size relative to maternal size.
l
Because most species give birth at night, any female that
is in labor during daylight hours should be observed
closely for signs of dystocia.
l
Diagnosis consists of a thorough physical examination
that includes visual inspection of the pelvic canal sup-
plemented by radiography and/or ultrasound.
l
Supportive therapy consisting of intravenous fluids
should be provided to the dam concurrently with
procedures to assist in the birth of the fetus, which may
include administration of subcutaneous calcium gluco-
nate 10% and oxytocin.
l
Diagnostics
The early recognition and treatment of dystocia is critical to
minimize possible life-threatening complications to the
fetus and/or dam. If dystocia is suspected, a thorough
physical examination should be performed that includes
visual inspection of the pelvic canal for abnormal fetal
presentation. Vaginal specula designed for use in humans
may be used for medium and large nonhuman primate
species while nasal specula can be used for smaller species.
The use of a lubricated speculum and adequate light source
increases the visibility of the vaginal vault and cervix.
Radiography and ultrasound examinations provide infor-
mation about fetal size, positioning, and the number of
fetuses present. In addition, fetal death may be indicated by
the presence of gas, overlapping skull bones, or abnormal
position (
Plunkett, 2000
). For full-term deliveries, because
the fetus is large, radiography is more useful to determine
overall fetal position when compared with ultrasonography.
Ultrasonography is a valuable tool for the examination and
assessment of the health of the fetus during delivery.
Measurement of fetal heartbeat can provide information
about fetal health and distress. Ultrasonography is also
The majority of dystocia cases eventually result
in
l
caesarean section.
Awareness for the potential for dystocia should be
increased during the birth season.
l
Etiology/Risk Factors/Transmission/Species
Dystocia, which is defined as difficult labor and delivery,
has been reported in prosimians, New World monkeys, Old
World monkeys, and great apes. New World monkeys are
especially susceptible to dystocia due to fetal size relative
to maternal size (
Hill, 1969; Norton et al., 2005; van
Lonkhuijzen et al., 2007; Schlabritz-Loutsevitch et al.,
2008
). Risk factors for dystocia include abnormal size and
position of the fetus, abnormal maternal pelvis shape as
affected by prior trauma, metabolic bone disease,
dysfunctional uterine action, cervical or vaginal stricture,
and macrosomal anomalies such as gestational diabetes,
hydrocephalus, and fetal hydrops (
Ford et al., 1998
).
