Objective—To characterize respiratory reflexes elicited
by nasal administration of sevoflurane (Sevo),
isoflurane (Iso), or halothane (Hal) in anesthetized
Animals—8 healthy Beagles.
Procedure—A permanent tracheostomy was created
in each dog. Two to 3 weeks later, dogs were anesthetized
by IV administration of thiopental and α-chloralose.
Nasal passages were isolated such that
inhalant anesthetics could be administered to the
nasal passages while the dogs were breathing 100%
O2 via the tracheostomy. Respiratory reflexes in
response to administration of each anesthetic at 1.2
and 2.4 times the minimum alveolar concentration
(MAC) and the full vaporizer setting (5%) were recorded.
Reflexes in response to administration of 5% of
each anesthetic also were recorded following administration
of lidocaine to the nasal passages.
Results—Nasal administration of Sevo, Iso, and Hal
induced an immediate ventilatory response characterized
by a dose-dependent increase in expiratory time
and a resulting decrease in expired volume per unit of
time. All anesthetics had a significant effect, but for
Sevo, the changes were smaller in magnitude.
Responses to administration of each anesthetic were
attenuated by administration of lidocaine to the nasal
Conclusions and Clinical Relevance—Nasal administration
of Sevo at concentrations generally used for
mask induction of anesthesia induced milder reflex
inhibition of breathing, presumably via afferent neurons
in the nasal passages, than that of Iso or Hal.
Respiratory reflexes attributable to stimulation of the
nasal passages may contribute to speed of onset and
could promote a smoother induction with Sevo, compared
with Iso or Hal. (Am J Vet Res 2001;62:311–319)
To evaluate the influence of manual ventilation-controlled respiration on right ventricular (RV) pressure-volume loop–derived and echocardiographic variables in dogs.
8 healthy, anesthetized Beagles.
In a prospective experimental study, pressure-volume catheters were percutaneously inserted into the right ventricle of each dog, and manual ventilation was performed; RV pressure-volume loop (hemodynamic) data and conventional echocardiographic variables were assessed. Two-dimensional speckle tracking echocardiography–derived RV strain (RVS) and RV systolic strain rate (RVSR) were obtained with RV free wall–only analysis (free wall) and RV global analysis (RVGA; interventricular septum). Variables were compared between end-inspiratory and end-expiratory phases of respiration by statistical methods. Multiple regression analysis was used to assess associations between selected hemodynamic and echocardiographic variables.
The RV pressure significantly increased, and RV volume, stroke volume, tricuspid annular plane systolic excursion, RV fractional area change, peak myocardial systolic velocity of the lateral tricuspid annulus, and RV free wall only–assessed RVS and RVSR significantly decreased in the inspiratory phase, compared with the expiratory phase. There were no significant differences in end-systolic elastance or RVGA-assessed RVS or RVSR between respiratory phases. The RVGA-assessed RVSR was significantly associated with stroke volume and end-systolic elastance.
CONCLUSIONS AND CLINICAL RELEVANCE
Specific RV echocardiographic variables were significantly affected by respiration. In contrast, RVS and RVSR determined with RVGA were not affected by respiration and were associated with hemodynamic indicators of RV contractility.