Effect of predosing versus slow administration of propofol on the dose required for anaesthetic induction and on physiologic variables in healthy dogs

Comparison of hemodynamic effects of propofol or alfaxalone during induction in dogs

This randomized prospective clinical study aimed to compare the hemodynamic effects of propofol and alfaxalone for the induction of anesthesia in dogs. Thirty-one healthy dogs undergoing various procedures in a private referral center were premedicated with intramuscular acepromazine (0.015 mg/kg) and methadone (0.15 mg/kg). They then received 5 mg/kg of propofol over 30 s for induction, followed by a maintenance dose of 25 mg/kg/h (Group P), or 2 mg/kg of alfaxalone over 30 s for induction, followed by a continuous rate infusion of 10 mg/kg/h (Group A). Heart rate (HR), mean arterial pressure (MAP), and the velocity time integral (VTI) of the aortic blood flow using transthoracic echocardiography were measured before anesthetic induction and every 15 s for 180 s. Dogs not adequately anaesthetized for intubation were excluded from the hemodynamic evaluation. Events of hypotension (any MAP value lower than 60 mmHg) were also recorded. Statistical analyses utilized ANOVA for repeated measures, two-way repeated measures ANOVA, paired t-tests, or Wilcoxon signed rank-test as appropriate. Significance was set at p < 0.05. Two dogs in Group P (2/14) and 3 in Group A (3/17) were excluded from the study because the anesthesia plane was too light to allow intubation. Treatment P resulted in a significant decrease in MAP between 45 and 75 s during the induction period, with no significant variation in HR, VTI, and VTI*HR. In treatment A, HR increases between 60 and 105 s, VTI decreases at 150-180 s. Analysis between groups did not show any difference in MAP (p = 0.12), HR (p = 0.10), VTI (p = 0.22) and VTI*HR (p = 0.74). During induction, hypotension was detected in 3/12 (25%) dogs in Group P and 1/14 (8%) in Group A. In healthy premedicated dogs, propofol and alfaxalone induction produce similar hemodynamic variations. Propofol induction results in a short-term reduction in MAP, whereas alfaxalone induction preserves MAP and cardiac output by significantly increasing heart rate.

Effects of different rates of propofol with or without S-ketamine on ventricular function in healthy cats - a randomized study

Propofol is used for anesthetic induction in cats and procedural sedation in countries where alfaxalone is not available. Studies have reported propofol-related effects in echocardiography variables in dogs and humans. However, there is a lack of echocardiography studies investigating propofol-related effects on cats. This study aimed to use echocardiography to investigate echocardiographic changes in three protocols using propofol: propofol-slow (2 mg/kg/min, PS); propofol-fast (8 mg/kg/min, PF); propofol-ketamine (S-ketamine 2 mg/kg bolus followed by propofol 2 mg/kg/min; PK) in healthy premedicated (gabapentin-buprenorphine-acepromazine; 200 mg/cat, 0.4, and 0.1 mg/kg, respectively), non-intubated cats. Echocardiographic measurements were obtained at three time points: baseline (before the administration of propofol), end of propofol titration (end-point, T0), and 15 min after T0 (T15). Propofol at a lower rate continued from T0 to T15. Echocardiographic and physiological variables included fractional shortening (FS%), ejection fraction (EF%), HR, BP, and others. Propofol requirements at T0 for PF, PS, and PK groups were 5.0 ± 0.9, 3.8 ± 0.7, and 2.4 ± 0.5 mg/kg, respectively. EF% neither change over time nor between groups. PF and PK showed a reduction in FS% at T0 (47 ± 6 to 34 ± 6 and 42 ± 6 to 36 ± 5, respectively). BP reduced significantly in PF and PS groups (136 ± 26 to 105 ± 13 and 137 ± 22 to 115 ± 15 mmHg, respectively). It is unclear whether changes in echocardiography variables were of clinical relevance related to treatment groups or a result of within-group individual responses.

Scoping review of quality of anesthetic induction and recovery scales used for dogs

OBJECTIVE

To compare, describe and assess the level of validation of all instruments measuring quality of induction and recovery from anesthesia in dogs.

DATABASES USED

A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University Library website and Google Scholar. The phrases 'induction scoring systems dogs', 'recovery scoring systems dogs', 'anesthetic induction score dogs', and 'anesthetic recovery score dogs' were used for searches using the 'best match search' function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020.

CONCLUSIONS

A thoroughly tested and validated scale for measuring the quality of induction and recovery does not exist in the current veterinary literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. It is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for psychometric validation and reliability.

Influence of doxapram and intermittent 10% carbon dioxide inspiration on cardiovascular and laryngeal functions in anesthetized dogs

OBJECTIVE

To compare the effects of two doses of doxapram intravenous injection and carbon dioxide inhalation on the cardiovascular and laryngeal functions of anesthetized hounds.

STUDY DESIGN

Experimental study.

ANIMALS

Six healthy adult dogs.

METHODS

In a Latin-square design, the mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously. The inspiratory normalized glottic gap areas (iNGGA) were measured before and after each stimulation with 0.55 mg/kg of doxapram (L-DOX), 2.2 mg/kg of doxapram (H-DOX), or 90 s of inhalation of 10% carbon dioxide in oxygen (I-CO₂ ). The stimulations were tested in duplicate or triplicate. Video clips of the laryngeal movement were scored by board-certified surgeons masked to the treatment.

RESULTS

The MABP increased with L-DOX and H-DOX up to 81% (both p < .001 compared to I-CO₂ ), and persisted during the other stimulations (both p < .001). An intermittent tachycardic effect of up to 79% increase in HR was observed with doxapram. The HR following H-DOX was higher than L-DOX and I-CO₂ (both p < .016). Neither hypertension nor tachycardia was observed with I-CO₂ . The iNGGA increased with all treatments (p < .001). The iNGGA was greater with H-DOX than L-DOX and I-CO₂ (both p < .007). All treatments received higher scores (all p < .001) with acceptable inter- and intra-observers Krippendorff's alphas.

CONCLUSION

All treatments were effective respiratory stimulants in anesthetized dogs; however, doxapram caused hypertension and tachycardia.

CLINICAL SIGNIFICANCE

Carbon dioxide inhalation might improve arytenoid motion without cardiovascular effects in dogs during clinical airway examinations.

Effects of a priming dose of alfaxalone on the total anesthetic induction dose for and cardiorespiratory function of sedated healthy cats

OBJECTIVE

To investigate the effects of a priming dose of alfaxalone on the total anesthetic induction dose for and cardiorespiratory function of sedated healthy cats.

ANIMALS

8 healthy adult cats.

PROCEDURES

For this crossover study, cats were sedated with dexmedetomidine and methadone administered IM. Cats next received a priming induction dose of alfaxalone (0.25 mg/kg, IV) or saline (0.9% NaCl) solution (0.025 mL/kg, IV) over 60 seconds and then an induction dose of alfaxalone (0.5 mg/kg/min, IV) until orotracheal intubation was achieved. Cardiorespiratory variables were recorded at baseline (immediately prior to priming agent administration), immediately after priming agent administration, after orotracheal intubation, and every 2 minutes until extubation. The total induction dose of alfaxalone was compared between the 2 priming agents.

RESULTS

Mean ± SD total anesthetic induction dose of alfaxalone was significantly lower when cats received a priming dose of alfaxalone (0.98 ± 0.28 mg/kg), compared with when cats received a priming dose of saline solution (1.41 ± 0.17 mg/kg). Mean arterial blood pressure was significantly higher when alfaxalone was used as the priming dose. No cats became apneic or had a hemoglobin oxygen saturation of < 90%. Expired volume per minute was not significantly different between the 2 priming agents.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of a priming dose of alfaxalone to healthy sedated cats reduced the total dose of alfaxalone needed to achieve orotracheal intubation, maintained mean arterial blood pressure, and did not adversely impact the measured respiratory variables.