Objective—To compare sedative, analgesic, and cardiopulmonary
effects after IV administration of
medetomidine (20 µg/kg), medetomidine-hydromorphone
(20 µg of medetomidine/kg and 0.1 mg of
hydromorphone/kg), and medetomidine-butorphanol
(20 µg of medetomidine/kg and 0.2 mg of butorphanol
tartrate/kg) in dogs.
Animals—6 dogs healthy mixed-breed dogs.
Procedure—Instruments were surgically inserted, and
heart rate (HR), respiratory rate (RR), systolic arterial
pressure (SAP), mean arterial pressure (MAP), diastolic
arterial pressure (DAP), mean pulmonary arterial pressure
(MPAP), pulmonary capillary wedge pressure
(PCWP), central venous pressure (CVP), core body
temperature, and cardiac output (CO) were measured
0, 5, 10, 15, 30, 45, and 60 minutes after injection.
Cardiac index (CI), stroke volume (SV), stroke index (SI),
systemic vascular resistance (SVR), and pulmonary
vascular resistance (PVR) were calculated. Arterial
samples for blood gas analysis were collected 0, 15,
and 45 minutes after injection. Intensity of analgesia,
degree of sedation, and degree of muscle relaxation
were evaluated at aforementioned time points and 75,
90, 120, 150, 180, and 210 minutes after injection.
Results—Administration of medetomidine, medetomidine-hydromorphone, and medetomidine-butorphanol
was associated with increases in SAP, MAP, DAP,
MPAP, PCWP, CVP, SVR, PVR, core body temperature,
and PaCO2 and decreases in HR, CO, CI, SV, SI, RR, pH,
and PaO2. Clinically important differences were not
detected among treatments. Medetomidine-hydromorphone
and medetomidine-butorphanol provided a
longer duration of sedation and better quality of analgesia,
compared with medetomidine alone.
Conclusions and Clinical Relevance—Medetomidine-hydromorphone
or medetomidine-butorphanol is associated
with improved analgesia and sedation but has
cardiopulmonary effects comparable to those for
medetomidine alone. (Am J Vet Res 2004;65:931–937)
Objective—To determine cardiovascular effects of desflurane in mechanically ventilated calves.
Animals—8 healthy male calves.
Procedure—Calves were anesthetized by face mask administration of desflurane to permit instrumentation. Administration of desflurane was temporarily discontinued until mean arterial blood pressure increased to ≥ 100 mm Hg, at which time baseline cardiovascular values, pulmonary arterial temperature, end-tidal CO2 tension, and end-tidal desflurane concentration were recorded. Cardiac index and systemic and pulmonary vascular resistances were calculated. Arterial blood gas variables were measured and calculated. Mean end-tidal concentration of desflurane at this time was 3.4%. After collection of baseline values, administration of 10% end-tidal concentration of desflurane was resumed and calves were connected to a mechanical ventilator. Cardiovascular data were collected at 5, 10, 15, 30, and 45 minutes, whereas arterial blood gas data were collected at 15 and 45 minutes after collection of baseline data.
Results—Mean ± SD duration from beginning desflurane administration to intubation of the trachea was 151 ± 32.8 seconds. Relative to baseline, desflurane anesthesia was associated with a maximal decrease in arterial blood pressure of 35% and a decrease in systemic vascular resistance of 34%. Pulmonary arterial blood temperature was decreased from 15 through 45 minutes, compared with baseline values. There were no significant changes in other measured variables. All calves recovered from anesthesia without complications.
Conclusions and Clinical Relevance—Administration of desflurane for induction and maintenance of general anesthesia in calves was smooth, safe, and effective. Cardiopulmonary variables remained in reference ranges throughout the study period.
Objective—To determine the cardiovascular and respiratory
effects of water immersion in horses recovering
from general anesthesia.
Animals—6 healthy adult horses.
Procedure—Horses were anesthetized 3 times with
halothane and recovered from anesthesia while positioned
in lateral or sternal recumbency in a padded
recovery stall or while immersed in a hydropool.
Cardiovascular and pulmonary functions were monitored
before and during anesthesia and during recovery
until horses were standing. Measurements and
calculated variables included carotid and pulmonary
arterial blood pressures (ABP and PAP, respectively),
cardiac output, heart and respiratory rates, arterial
and mixed venous blood gases, minute ventilation,
end expiratory transpulmonary pressure (PendXes),
maximal change in transpulmonary pressure
(ΔPtpmax), total pulmonary resistance (RL), dynamic
compliance (Cdyn), and work of breathing ().
Results—Immersion in water during recovery from
general anesthesia resulted in values of ABP, PAP, PendXes, ΔPtpmax, RL, and that were significantly greater and values of Cdyn that were significantly less,
compared with values obtained during recovery in a padded stall. Mode of recovery had no significant
effect on any other measured or calculated variable.
Conclusions and Clinical Relevance—Differences in
pulmonary and cardiovascular function between horses
during recovery from anesthesia while immersed
in water and in a padded recovery stall were attributed
to the increased effort needed to overcome the
extrathoracic hydrostatic effects of immersion. The
combined effect of increased extrathoracic pressure
and PAP may contribute to an increased incidence of
pulmonary edema in horses during anesthetic recovery
in a hydropool. (Am J Vet Res 2001;62:1903–1910)
Objective—To compare effects of isoflurane and sevoflurane on intracranial pressure and cardiovascular variables at 1.0, 1.5, and 2.0 times the minimum alveolar concentration (MAC) in mechanically ventilated normocapnic dogs.
Animals—6 healthy male Beagles.
Procedures—The individual MAC was determined for each agent with an electrical stimulus. After a minimum of 1 week, anesthetic induction by use of a mask with one of the inhalation anesthetics selected randomly was followed by mechanical ventilation and instrumentation for measurement of intracranial pressure and cardiovascular variables. Heart rate; systolic, mean, and diastolic arterial blood pressures; central venous pressure; mean pulmonary arterial pressure; pulmonary artery occlusion pressure; cardiac output; intracranial pressure (ICP); core body temperature; end-tidal inhalation anesthetic and carbon dioxide concentration; and arterial blood gas values were measured after attaining equilibrium at 1.0, 1.5, and 2.0 MAC of each inhalation anesthetic. Cardiac index, systemic vascular resistance, pulmonary vascular resistance, and cerebral perfusion pressure (CPP) were calculated.
Results—Mean ICP did not differ within and between anesthetics at any MAC. Compared with equipotent concentrations of isoflurane, the CPP and mean values for systolic, mean, and diastolic arterial blood pressures were increased at 2.0 MAC for sevoflurane, whereas mean values for mean and diastolic arterial blood pressures and systemic vascular resistance were increased at 1.5 MAC for sevoflurane.
Conclusions and Clinical Relevance—Although ICP was similar in healthy normocapnic dogs, CPP was better maintained during 2.0 MAC for sevoflurane, compared with isoflurane.