Abstract

The elephant is the largest living land mammal and is in danger of extinction. The few literature citations involving blood pressure (BP) measurements have utilized direct arterial measurement of immobilized or stationary conditioned elephants.^2-5 These investigations determined that BP in the healthy elephant is generally higher than most other clinically normal mammals studied but similar to un-sedated domestic cattle and horses and increased in laterally recumbent elephants. This project was undertaken to compare cited direct arterial measurements to indirect oscillometric BP measurement of systolic, diastolic, and mean arterial pressure (MAP); and heart rate (HR) in four stationary, non-sedated African elephants.

Four female African elephants ranging in age from 28–38 years of age were used in this study. One elephant (E3) had a history of fetal retention of five years and bilateral scleral injection but was clinically normal in all other regards. The three remaining elephants had no significant clinical histories.

All four elephants were conditioned to present the tail for placement of a standard occlusive BP cuff (Cardell™, CAS Medical Systems, Inc. Branford, CT). Use of this indirect oscillometric unit has been compared with simultaneous direct arterial measurement in anesthetized African lions (Panthera leo) and an immobilized African elephant at the Kansas City Zoo. Blood pressure results in each animal study were virtually identical with both techniques.

The width of the cuff was approximately 40% the circumference of the tail (12 cm cuff on an average 27.5 cm tail circumference) of the elephant, in accordance with general recommendations for obtaining BP measurements in domestic animals.^1,6 Cuff placement was at the distal extent of the caudal tail fold. Three sets of BPs, heart rates, and respiratory rates were obtained on three different occasions in each elephant (Table 1). Each elephant was sampled at the same time of day and had not been exercised.

Table 1. Indirect oscillometric blood pressure measurements in African elephants (Loxodonta africana) (pressures in mm Hg, rates/min)

Blood pressure measurements obtained in three of the four elephants in this population compared favorably with reference ranges obtained invasively (direct arterial) in un-sedated African elephants.² In the elephant with scleral injection and retained fetal mummy (E3), overall BP measurements were higher (on average) than the other three elephants and ranges reported in a previous study of direct arterial pressures in un-sedated African elephants.² This may reflect a hypertensive state related to increased systemic vascular resistance associated with a retained calf. However, this elephant is the oldest of the four animals studied, and blood pressure parameters generally increase with age in humans and this may be the case with this elephant. Further investigation into the potential causes for a clinical hypertensive state in this elephant are being pursued.

The advantages of this technique are the non-invasive application, portability, and comparable results to direct arterial measurement. Disadvantages are that BP measurement can be altered by cuff size, placement, and movement. In this study, cuff placement and size was identical in all elephants, and the only movement was associated with masticatory efforts involved with positive food enrichment, eliminating two of the three variables. Additional elephants are being evaluated and refinement of BP measurement techniques are being completed to help define normal indirect oscillometric BP values in the African elephant.

Use of an indirect oscillometric measuring device for obtaining BP measurements in African elephants may prove to be an easily applied, valuable ancillary diagnostic tool when evaluating cardiovascular parameters without the need for sedation or immobilization.

Acknowledgments

The authors thank the Kansas City Zoo elephant care staff for their expertise in behavioral conditioning of the African elephants at the Kansas City zoo and the countless individuals and institutions striving to conserve the elephant.

Literature Cited

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6.  Valtonen MH, Eriksson LM. The effect of cuff width on accuracy of indirect measurement of blood pressure in dogs. Res Vet Sci. 1970;11:358–362.