A COMPARISON OF INDIRECT BLOOD-PRESSURE MONITORING TECHNIQUES IN THE ANESTHETIZED CAT

Objective-To determine the accuracy of three indirect blood pressure m onitoring techniques (oscillometric technique [OS], Doppler [DOP], and optical plethysmography [OP] [blood pressure determined with a pulse oximeter waveform]) when compared with direct arterial pressure measur ement in cats. Study Design-Prospective study. Animal Population-Eight healthy (five female, three male), domestic short-hair cats, weighing 3.5 +/- 0.8 kg. Methods-Cats were anesthetized with isoflurane. The i nspired concentration of isoflurane was adjusted to produce mild hypot ension (80 to 100 mm Hg direct systolic), moderate hypotension (60 to 80 mm Hg direct systolic), and severe hypotension (<60 mm Hg direct sy stolic). Indirect pressure measurements were obtained from the thoraci c limb and compared with concurrent direct measurement using regressio n analysis and a modification of Bland and Altman's technique. Results -All three techniques underestimated systolic pressure. OS produced th e best prediction of systolic pressure with a bias +/- precision of -1 5.9 +/- 8.1 mm Hg. DOP and OP were relatively inaccurate with a bias /- precision of -25 +/- 7.4 mm Hg and -25 +/- 7.5 mm Hg. All three tec hniques correlated well with direct pressure with r values of 0.81, 0. 88, and 0.88 for OS, DOP, and OF. DOP and OP provided an accurate pred iction of direct mean arterial pressure with a bias +/- precision of - 0.8 +/- 6 mm Hg and 0.6 +/- 5.5 mm Hg. Correlation was good between DO P and mean arterial pressure with r = 0.89. Correlation was also good between OP and mean arterial pressure with r = 0.90. Conclusions-OS pr ovided the most accurate prediction of direct systolic pressure. DOP a nd OP provided a good prediction of mean arterial pressure in the cat. Clinical Relevance-All three of these techniques are useful for detec ting trends. Direct monitoring of blood pressure should be considered if accurate blood pressure measurement is required. (C)Copyright 1998 by The American College of Veterinary Surgeons.