Objective—To compare 3 types of noxious stimuli
applied to various anatomic areas of anesthetized
dogs and rabbits for determination of the minimum
alveolar concentration (MAC).
Animals—10 dogs and 10 rabbits.
Procedure—Dogs were anesthetized with isoflurane
and halothane in a randomized order. Rabbits were
anesthetized with isoflurane. The MAC was determined
by skin incision on the lateral aspect of the
chest; clamping of the tail, paw of the forelimb, and
paw of the hind limb; and application of electrical current
to the oral mucosa (dogs only), forelimb, and hind
limb. The MAC was the end-tidal concentration midway
between the value permitting and preventing
purposeful movement in response to noxious stimuli.
Results—In dogs, mean ± SEM MAC for isoflurane
was 1.27 ± 0.05% for clamping stimuli, 1.36 ± 0.04%
for oral electrical stimulation, 1.35 ± 0.04% for electrical
stimulation to the limbs, and 1.01 ± 0.07% for surgical
incision. The MAC for halothane was 0.97 ±
0.03% for tail clamping, 0.96 ± 0.03% for clamping of
the limbs, 1.04 ± 0.03% for electrical stimulation, and
0.75 ± 0.06% for surgical incision. In rabbits, MAC for
isoflurane was 2.08 ± 0.02% for clamping stimuli,
2.04 ± 0.02% for electrical stimulation, and 0.90 ±
0.02% for surgical incision. The MAC for surgical incision
was significantly lower than values for the other
methods in both species.
Conclusions and Clinical Relevance—Use of electrical
current and clamping techniques resulted in similar
MAC values. Surgical incision underestimated
MAC values in dogs and rabbits. (Am J Vet Res
Objective—To compare cardiac output (CO) measured by use of the partial carbon dioxide rebreathing method (NICO) or lithium dilution method (LiDCO) in anesthetized foals.
Sample Population—Data reported in 2 other studies for 18 neonatal foals that weighed 32 to 61 kg.
Procedures—Foals were anesthetized and instrumented to measure direct blood pressure, heart rate, arterial blood gases, end-tidal isoflurane and carbon dioxide concentrations, and CO. Various COs were achieved by administration of dobutamine, norepinephrine, vasopressin, phenylephrine, and isoflurane to allow comparisons between LiDCO and NICO methods. Measurements were obtained in duplicate or triplicate. We allowed 2 minutes between measurements for LiDCO and 3 minutes for NICO after achieving a stable hemodynamic plane for at least 10 to 15 minutes at each CO.
Results—217 comparisons were made. Correlation (r = 0.77) was good between the 2 methods for all determinations. Mean ± SD measurements of cardiac index for all comparisons with the LiDCO and NICO methods were 138 ± 62 mL/kg/min (range, 40 to 381 mL/kg/min) and 154 ± 55 mL/kg/min (range, 54 to 358 mL/kg/min), respectively. Mean difference (bias) between LiDCO and NICO measurements was −17.3 mL/kg/min with a precision (1.96 × SD) of 114 mL/kg/min (range, −131.3 to 96.7). Mean of the differences of LiDCO and NICO measurements was 4.37 + (0.87 × NICO value).
Conclusions and Clinical Relevance—The NICO method is a viable, noninvasive method for determination of CO in neonatal foals with normal respiratory function. It compares well with the more invasive LiDCO method.