Page 2398 - Cote clinical veterinary advisor dogs and cats 4th

Ventilation, Positive Pressure 1185

○ Under the influence of estrogens produced • Serum progesterone assay (p. 1375): often
by ovarian follicles, the vaginal epithelium used in conjunction with vaginoscopy; the
VetBooks.ir during proestrus. The vaginal mucosa of cells (p. 1183) indicate when to begin
undergoes hyperplasia and metaplasia
appearance of the mucosa and cornification
becomes edematous, swollen, and appears
measuring serum progesterone. Conversely,
smooth, round, and plump.
serve to corroborate hormonal findings
○ As the bitch advances into late proestrus visual inspection of the vaginal mucosa can
and estrus, declining concentrations of (luteinizing hormone and/or progesterone
serum estrogens result in a wrinkling and levels). During the fertile period in the bitch,
shrinking of the vaginal mucosal folds, the vaginal wall is characteristically crenulated
progressing to a markedly angulated and as a result of low and high blood levels of
crenulated outline during mid to late estrogen and progesterone, respectively.
estrus. VAGINOSCOPY Endoscopic view of the canine
Pearls vagina in midestrus.
Postprocedure • Vaginal procedures are best performed during
• Submission of samples proestrus and estrus. Procedures and Techniques
• Microscopic review of smears • When not in estrus, most bitches resent SUGGESTED READING
vaginal exams.
Alternatives and Their • Sedation may be required for uncooperative Lévy X. Videovaginoscopy of the canine vagina.
Relative Merits bitches, whether in estrus or not. Reprod Domest Anim 51(Suppl 1):31-36, 2016.
• Digital vaginal palpation: conveys the changes • A minute amount of petroleum jelly may AUTHOR: Carlos R.F. Pinto, MedVet, PhD, DACT
in texture of the vaginal mucosa and reveals facilitate the introduction of the vaginoscope EDITORS: Leah A. Cohn, DVM, PhD, DACVIM; Mark S.
vaginal strictures but is not as informative (and vaginal shunt whenever applicable) in Thompson, DVM, DABVP
as vaginoscopy. a patient resenting the procedure.

Ventilation, Positive Pressure

Difficulty level: ♦♦♦ ○ Animals with ventilatory failure and ○ Owner communication and highly trained
normal lung function (e.g., opioid or staff are essential.
Synonyms barbiturate overdose, certain toxins, ○ Manual PPV requires a person to con-
Artificial ventilation, assisted ventilation, mechan- tick paralysis, botulism) have the best tinually deliver manual breaths to the
ical ventilation, positive-pressure ventilation prognosis. Survival rates with respira- animal.
(PPV) tory failure are 20%-30%, and patients ○ Mechanical PPV involves a machine to
with ventilatory failure have a 50%-70% deliver breaths.
Overview and Goals survival rate. ○ Manual PPV is practical only for short-
• Maintain normal arterial oxygen (PaO 2 ) term use (up to several hours), whereas
and carbon dioxide (PaCO 2 ) pressure until Indications mechanical PPV is required for long-term
an underlying disease can be identified and Early intervention carries a better prognosis. care (>6-12 hours).
treated. • Ventilatory failure: PaCO 2 > 55 mm Hg and • Intubation
• Therapeutic targets (using the least aggressive pH < 7.3 ○ Animals can be ventilated via inflated
ventilator settings) ○ Some can be managed with short-term endotracheal or tracheostomy (p. 1166)
○ PaO 2 > 60 mm Hg (minimum, > 80 mm PPV (e.g., reversible opioid overdose). tubes.
Hg preferred) • Respiratory failure: PaO 2 < 60 mm Hg ○ Low-pressure, high-volume cuffs are
○ PaCO 2 35-50 mm Hg or SaO 2 < 90% despite supplemental preferred.
○ End-tidal CO 2 35-50 mm Hg oxygen ○ Endotracheal intubation is more common
○ Arterial oxygen saturation (SaO 2 ) > 90% ○ Often requires > 12 hours of PPV (familiarity, ease of procedure, minimal
(minimum, > 94% preferred) • Animals with sustained, extreme respiratory risk of tissue damage).
○ Measure PaO 2 and PaCO 2 with arterial distress: increased work of breathing ○ If PPV exceeds 24 hours or when heavy
blood gases (ABGs); measure end-tidal ○ Often requires > 12 hours of PPV sedation is not desired, tracheostomy may
CO 2 with capnometry (inserted between be preferred (allows some dogs to eat and
endotracheal tube and breathing device) Contraindications drink).
and SaO 2 with pulse oximetry (attached • Irreversible underlying disease • Sedation (IV, as needed; more common with
to the tongue). The PaO 2/FIO 2 ratio • Lack of trained personnel concurrent endotracheal intubation); options
is helpful in predicting prognosis and • If > 6-12 hours of PPV is anticipated, include
severity of the underlying disease. initiating manual PPV is questionable if ○ Pentobarbital 2 mg/kg boluses to effect
• Prognosis varies with underlying disease. mechanical PPV is not available. (up to 12 mg/kg) q 4-6h or as needed
○ A reasonable goal is to discharge 25%-40% • Not having a 24-hour, on-site trained techni- to maintain sedation
of mechanically ventilated cases. Survival cian (with the animal) and veterinarian ○ Fentanyl 5 mcg/kg boluses to effect up to
rates of dogs with PaO 2/FIO 2 less than 50 mcg/kg, then 5-7 mcg/kg/h constant-
200 mm Hg at 4 and 12 hours after Equipment, Anesthesia rate infusion (CRI) (can add diazepam)
initiation of positive-pressure ventilation • PPV requires intensive 24-hour monitoring ○ Propofol 2-8 mg/kg bolus to effect, then
(PPV) are 15% and 6%, respectively. and nursing care but can be lifesaving. 0.1-0.3 mg/kg/min CRI

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