Objective

To evaluate the systemic cardiovascular effects of dose escalating administration of norepinephrine in healthy dogs anesthetized with isoflurane.

Study design

Experimental study.

Animals

A total of six adult laboratory Beagle dogs, 10.5 (9.2–12.0) kg [median (range)].

Methods

Each dog was anesthetized with isoflurane at an end-tidal concentration of 1.7%, mechanically ventilated and administered a continuous rate infusion of rocuronium (0.5 mg kg^–1 hour^–1). Each dog was administered incremental dose rates of norepinephrine (0.05, 0.125, 0.25, 0.5, 1.0 and 2.0 μg kg^–1 minute^–1), and each dose was infused for 15 minutes. Cardiovascular variables were recorded before administration and at the end of each infusion period.

Results

Norepinephrine infusion increased mean arterial pressure (MAP), cardiac output (CO) and oxygen delivery in a dose-dependent manner. Systemic vascular resistance did not significantly change during the experiment. Stroke volume increased at the lower dose rates and heart rate increased at the higher dose rates. Oxygen consumption and lactate concentrations did not significantly change during infusions.

Conclusions

In dogs anesthetized with isoflurane, norepinephrine increased MAP by increasing the CO. CO increased with a change in stroke volume at lower dose rates of norepinephrine. At higher dosage, heart rate also contributed to an increase in CO. Norepinephrine did not cause excessive vasoconstriction that interfered with the CO during this study.

Clinical relevance

Norepinephrine can be useful for treating hypotension in dogs anesthetized with isoflurane.

中文翻译：

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去甲肾上腺素剂量递增对异氟醚麻醉健康犬的心血管影响

客观的

评估去甲肾上腺素剂量递增给药对用异氟醚麻醉的健康犬的全身心血管影响。

学习规划

实验研究。

动物

总共六只成年实验室比格犬，10.5 (9.2–12.0) kg [中位数（范围）]。

方法

每只狗都用呼气末浓度为 1.7% 的异氟醚麻醉，机械通气并连续输注罗库溴铵（0.5 mg kg ^–1小时^–1）。每只狗以递增剂量率给药（0.05、0.125、0.25、0.5、1.0 和 2.0 μg kg ^–1分钟^–1），每个剂量输注 15 分钟。在给药前和每个输注期结束时记录心血管变量。

结果

去甲肾上腺素输注以剂量依赖性方式增加平均动脉压 (MAP)、心输出量 (CO) 和氧气输送。全身血管阻力在实验过程中没有显着变化。在较低剂量率下每搏量增加，而在较高剂量率下心率增加。在输注过程中，耗氧量和乳酸浓度没有显着变化。

结论

在用异氟醚麻醉的狗中，去甲肾上腺素通过增加 CO2 增加了 MAP。在较低剂量率的去甲肾上腺素下，CO 随着每搏输出量的变化而增加。在较高剂量下，心率也会导致 CO 增加。在本研究期间，去甲肾上腺素不会引起过度的血管收缩，从而干扰 CO。

临床相关性

去甲肾上腺素可用于治疗用异氟醚麻醉的狗的低血压。