Objective

To characterize the cardiovascular effects of increasing dosages of norepinephrine (NE) in healthy isoflurane-anesthetized rabbits.

Study design

Prospective experimental study.

Animals

A total of nine female ovariohysterectomized New Zealand White rabbits weighing 3.4 ± 0.2 kg (mean ± standard deviation).

Methods

Rabbits were premedicated intramuscularly with buprenorphine (0.05 mg kg^–1) and midazolam (0.5 mg kg^–1). Anesthesia was induced with intravenous propofol and maintained with a 1.1 × minimum alveolar concentration of isoflurane for this species to induce hypotension. Rabbits were administered NE infusions at three doses: low, 0.1 μg kg^–1 minute^–1; medium, 0.5 μg kg^–1 minute^–1; and high doses, 1 μg kg^–1 minute^–1 for 10 minutes each in that order. Cardiovascular variables including heart rate (HR), cardiac output (CO) by lithium dilution technique and systolic (SAP), mean (MAP) and diastolic (DAP) invasive arterial blood pressures measured in the auricular artery were recorded at baseline, 10 minutes after the start of the infusion of each NE treatment and 10 minutes after NE was discontinued. A linear mixed model and a type III anova with Tukey’s post hoc comparison was performed (p < 0.05).

Results

Significant increases in SAP (28% and 90%), MAP (27% and 90%) and DAP (33% and 97%) were measured with medium and high dose treatments, respectively (p < 0.001), with no changes in CO. HR decreased and stroke volume increased significantly with high dose treatment (by 17% and 15%, respectively; p < 0.05). No arrhythmias were noticed with NE treatments.

Conclusions and clinical relevance

The infusion of NE at 0.5–1.0 μg kg^–1 minute^–1 is a potentially effective treatment for hypotension in healthy isoflurane-anesthetized New Zealand White rabbits.

中文翻译：

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去甲肾上腺素剂量增加对健康的异氟烷麻醉的新西兰白兔的心血管作用。

目的

表征在健康的异氟烷麻醉的兔子中增加去甲肾上腺素（NE）的心血管作用。

学习规划

前瞻性实验研究。

动物

总共9只雌性经卵巢子宫切除的雌性新西兰白兔，体重3.4±0.2 kg（平均±标准偏差）。

方法

用丁丙诺啡（0.05 mg kg ^–1）和咪达唑仑（0.5 mg kg ^–1）进行肌肉内药物治疗。静脉内使用异丙酚诱导麻醉，并维持最低1.1倍的异氟醚肺泡浓度，以使该物种引起低血压。兔子接受三剂NE输注：低剂量0.1μgkg ^–1分钟^–1；中等，0.5μgkg ^–1分钟^–1；高剂量，1μgkg ^–1分钟^–1依次按10分钟进行。在基线后10分钟后，记录在心律动脉中测量的心血管变量，包括心率（HR），通过锂稀释技术的心输出量（CO）和收缩压（SAP），平均值（MAP）和舒张压（DAP）侵入动脉血压在开始每次NE治疗后以及中止NE后10分钟。进行了线性混合模型和具有Tukey事后比较的III型方差分析（p <0.05）。

结果

中剂量和高剂量治疗分别测量到SAP（28％和90％），MAP（27％和90％）和DAP（33％和97％）显着增加（p <0.001），CO不变高剂量治疗后，HR降低，中风量显着增加（分别降低了17％和15％；p <0.05）。NE治疗未发现心律不齐。

结论与临床意义

在健康的异氟烷麻醉下的新西兰白兔中，以0.5–1.0μgkg ^–1分钟^–1的速度输注NE是降低血压的潜在有效方法。