Partial pressure of end-tidal CO2sampled via an intranasal catheter as a substitute for partial pressure of arterial CO2in dogs

An investigation of the effects of intratesticular alfaxalone and lidocaine during castration in piglets

OBJECTIVE

To determine whether intratesticular injection of an alfaxalone-lidocaine combination can induce anesthesia and provide a rapid recovery in piglets undergoing surgical castration.

STUDY DESIGN

Randomized experimental study.

ANIMALS

A group of 30 male piglets, aged 2-10 days, weighing 1.3-4.6 kg.

METHODS

Animals were randomly divided into three equal groups for intratesticular administration of alfaxalone + lidocaine: high dose (group HD; 8 mg kg^-1 + 2.5 mg kg^-1), medium dose (group MD; 6 mg kg^-1 + 2 mg kg^-1) and low dose (group LD; 4 mg kg^-1 + 1.5 mg kg^-1). Induction and recovery times, movement and vocalization were recorded. Pulse rate (PR), oxygen saturation, respiratory rate (f_R), rectal temperature, blood pressure and end-tidal carbon dioxide were recorded until recovery.

RESULTS

Induction time did not differ significantly among groups (p = 0.19); mean time of 2.2, 3.3 and 3.7 minutes for HD, MD and LD, respectively. Recovery time to sternal recumbency was significantly faster in LD compared with HD and MD (p = 0.005). Time to standing was mean 34.1, 31.6 and 29.6 minutes for HD, MD and LD, respectively (p = 0.58). Incidences of movement and vocalization during the castration procedure were decreased in HD and MD compared with LD, but were not statistically different. There were no differences in the physiologic data among the groups except for PR, which decreased in all three groups (p < 0.05), and f_R, which increased in MD and LD (p < 0.05).

CONCLUSIONS AND CLINICAL RELEVANCE

The alfaxalone-lidocaine combinations investigated in this study induced deep sedation in all piglets. Physiologic data remained within clinically acceptable ranges, suggesting that this drug combination by intratesticular injection prior to castration in neonatal piglets is well tolerated. The authors recommend the alfaxalone (6 mg kg^-1) + lidocaine (2 mg kg^-1) dose.

Agreement between values for arterial and end-tidal partial pressures of carbon dioxide in spontaneously breathing, critically ill dogs

OBJECTIVE

To determine agreement between arterial partial pressures of carbon dioxide (PaCO(2)) and end-tidal partial pressures of carbon dioxide (PETCO(2)) measured with a nasal catheter in spontaneously breathing, critically ill dogs.

DESIGN

Validation study.

ANIMALS

26 client-owned dogs admitted to an intensive care unit for various conditions.

PROCEDURES

PaCO(2) was measured with a commercial blood gas analyzer, and PETCO(2) was measured with a sidestream capnograph attached to a nasal catheter. Measurements were obtained twice (ie, with and without supplemental oxygen). Paired values were compared by means of the Pearson correlation method. Level of agreement was assessed by means of the Bland-Altman method.

RESULTS

Mean difference between PaCO(2) and PETCO(2) when dogs did not receive supplemental oxygen (mean +/- SD, 3.95 +/- 4.92 mm Hg) was significantly lower than mean difference when dogs did receive supplemental oxygen (6.87 +/- 6.42 mm Hg). Mean difference in dogs with a condition affecting the respiratory system (8.55 +/- 5.43 mm Hg) was significantly higher than mean difference in dogs without respiratory tract disease (3.28 +/- 3.23 mm Hg). There was a significant linear correlation and good agreement between measured values of PaCO(2) and PETCO(2). Catheter size, ventilatory status, and outcome were not significantly associated with mean difference between PaCO(2) and PETCO(2).

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that nasal capnography is a clinically relevant method of estimating PaCO(2) in spontaneously breathing, critically ill dogs, but that values should be interpreted with caution in dogs receiving supplemental oxygen and in dogs with conditions affecting the respiratory system.