Does pentobarbital anesthesia depress left ventricular contractility in dogs?

Area of Science:

• Cardiovascular Physiology
• Anesthesiology

Background:

• Previous studies suggested pentobarbital sodium (NP) depresses left ventricular (LV) contractility.
• These studies measured LV contractility at extremely high serum concentrations of NP shortly after administration.

Purpose of the Study:

• To compare LV contractility in dogs under awake and anesthetized conditions with pentobarbital sodium.
• To investigate the effects of NP on LV contractility at a therapeutic concentration (approximately 25 mg/l).

Main Methods:

• In vivo study in 13 dogs with implanted ultrasonic crystal and pressure transducers in the LV.
• Measurements of LV contractility (ejection fraction, end-systolic pressure-volume relationship) were taken 1 hour post-NP administration.
• In vitro canine right ventricular trabecular preparation was used to assess direct myocardial effects.

Main Results:

• No decrease in LV contractility was observed in vivo during NP anesthesia, even with prior beta-adrenergic blockade (propranolol).
• The in vitro preparation showed only a minimal decrease in isometric tension at the studied NP concentrations.
• LV contractility remained stable at NP serum concentrations of approximately 25 mg/l.

Conclusions:

• Pentobarbital sodium anesthesia does not depress LV contractility at serum concentrations of approximately 25 mg/l.
• The findings challenge previous assumptions about NP's cardiodepressant effects at clinically relevant levels.