Resistive index for kidney evaluation in normal and diseased cats

Effects of stone density on alteration in renal resistive index after extracorporeal shock wave lithotripsy for non-obstructed kidney stones

Aim The doppler-based renal resistive index is a recently proposed technique for measuring changes in renal perfusion and predicting acute kidney damage. The purpose of this study was to look at the influence of stone density on the renal resistive index (RI) after extracorporeal shock wave lithotripsy (ESWL) in patients with non-obstructed kidney stones. Material and Method Between May 2020 and July 2021, 48 consecutive patients with unilateral renal calculi of  20 mm were treated with ESWL monotherapy. The patients' non-contrast computed tomography (NCCT) images were processed and grouped into two groups using Hounsfield units (HU) (Group 1, n=27,  1000 HU; Group 2, n=21,  1000 HU). The same radiologist performed Doppler ultrasonography on all cases before, one hour, and one week following ESWL. Measurement of the RI taken in the remote region (at least 20 mm from the stones). Patient age, gender, BMI, stone laterality, stone size, and stone position were investigated as potential predictors. Results The average stone size for Group 1 was 11.7 ± 3.3 mm and 12.1 ± 2.8 mm for Group 2. The mean RI values before ESWL for Group 1 and Group 2 were 0.54 and 0.53, respectively. On comparing the pre-treatment data with the 1 hour after SWL, a statistically significant increase was recorded in the RI value for both groups. However, there was no significant difference in RI values between groups 1 and 2 1 hour and 1 week following lithotripsy therapy. After one week, the mean RI returned to pretreatment levels, according to a follow-up doppler investigation. There was no association between stone density and RI (p > 0.05). Conclusion Stone density is a significant independent predictor of ESWL outcome; however, high stone densities detected with NCCT were not associated with a significant change in RI. Post-ESWL therapy alterations are present and reversible one week after the treatment.

Evaluating feline lower urinary tract disease: Doppler ultrasound of the kidneys

OBJECTIVES

Ultrasonography is used in the evaluation of urinary disorders, and the resistivity index (RI) and pulsatility index (PI) have been successfully used to detect early hemodynamic changes in the course of kidney diseases in humans and dogs. The aim of this study was to investigate RI and PI in cats with feline lower urinary tract disease (FLUTD).

METHODS

Twenty-nine client-owned cats were selected and divided into a control group (CG; n = 10), a group of animals with obstructive FLUTD (OG; n = 11) and non-obstructive FLUTD (nOG; n = 8). Clinical, laboratory and ultrasound evaluations were performed in all cats.

RESULTS

RI and PI values for cats in the CG were below the upper limit of normal suggested in other studies, while cats with FLUTD showed significantly higher values in the assessment of RI (P = 0.027 and P = 0.034, respectively) and PI (P = 0.044 and P = 0.048, respectively) of the right and left kidneys.

CONCLUSIONS AND RELEVANCE

Alteration in renal blood flow was observed in cats with lower urinary tract disorders, even in the nOG group. To the best of our knowledge, this is the first report of renal blood flow changes related to non-obstructive FLUTD.

Evaluation of Renal Blood Flow in Dogs during Short-Term Human-Dose Epoprostenol Administration Using Pulsed Doppler and Contrast-Enhanced Ultrasonography

Simple Summary

Since there is a lack of information regarding how epoprostenol, a prostacyclin, affects canine renal blood flow (RBF), we investigated the effects of short-term administration of epoprostenol at human doses of 2, 5, and 10 ng/kg/min intravenously for 20 min on RBF in six healthy dogs under anesthesia. The effects of short-term administration were investigated. As the dose of epoprostenol increased, peak systolic and end diastolic velocities of the renal arteries, maximum and minimum venous flow velocities of the interlobular and renal veins, and heart rate all tended to increase. However, these increases were not significant. These results indicate that the administration of human doses of epoprostenol to dogs does not produce significant changes in renal or systemic circulation.

Abstract

Prostacyclin is an in vivo bioactive substance that regulates renal blood flow (RBF). Information regarding how epoprostenol, a prostacyclin preparation, affects RBF in dogs is lacking. We investigated the effects of short-term epoprostenol administration on RBF in six healthy dogs under anesthesia by administering it intravenously at human doses—2, 5, and 10 ng/kg/min for 20 min. RBF was evaluated before and during epoprostenol administration using pulsed Doppler ultrasonography, and renal perfusion was evaluated using contrast-enhanced ultrasonography. Effects on renal and systemic circulation were evaluated by measuring systolic arterial, mean arterial, diastolic arterial, pulmonary arterial, mean right atrial, and pulmonary capillary wedge pressures; heart rate; and cardiac output. Kruskal–Wallis and Bonferroni multiple comparison tests and Spearman’s rank correlation coefficient were used for statistical analyses. As epoprostenol dosage increased, the peak systolic and end diastolic velocity of the renal artery, maximum and minimum venous flow velocities of the interlobular and renal veins, and heart rate all tended to increase, although not significantly. Our results indicate that human-dose epoprostenol administration in dogs does not cause significant changes in renal or systemic circulation. However, the human doses used may have been too low to produce a clinical effect in dogs.

Resistivity and pulsatility indexes in feline kidney disease: a systematic review

Doppler ultrasonography is used in the evaluation of hemodynamics, and the resistivity (RI) and pulsatility (PI) indexes provide information about resistance to blood flow within a vessel. This systematic review was carried out to evaluate renal RI and PI in clinically healthy and nonsedated cats and as well as their usefulness in the evaluation of kidney disease in cats. An electronic search in the PubMed, Scopus, and Web of Science databases was carried out using the terms "resistive index" or "resistivity index" or "pulsatility index;" "Doppler;" "renal" or "kidney;" and "cat" or "feline" in titles, abstracts, and keywords. Variables of interest related to experimental model features, research methods, and technical resources were extracted from the studies. The methodological quality was assessed with SYRCLE's risk of bias tool. Thus, 14 studies involving healthy and sick cats were selected. Interestingly, the upper limits estimated for both RI and PI varied among studies. The upper limits of renal RI for healthy cats varied between 0.64 and 0.72, while for PI, the values varied from 1.06 to 1.29. A limited number of studies evaluated cats with kidney disease. In most studies, RI values of kidneys with different conditions were significantly different from kidneys of healthy animals, indicating that RI values increase with kidney disease. The parameters body weight, heart rate, and age seem to influence the RI values. Standardized studies regarding its realization and description are still necessary to define normal values and analyze its applicability in the clinical diagnostic routine.

Evaluation of symmetric dimethylarginine and Doppler ultrasonography in the diagnosis of gentamicin-induced acute kidney injury in dogs

Acute kidney injury is a common problem in dogs and is associated with significant morbidity and mortality. So, the present study aimed to evaluate symmetric dimethylarginine (SDMA) and Doppler ultrasonography including resistive index (RI) in the diagnosis of acute kidney injury in dogs. Ten healthy mongrel dogs were injected with gentamicin sulfate 10% at the dose of 30 mg/kg body weight daily for 10 days for induction of acute kidney injury. Clinical, biochemical, ultrasonographic, and Doppler ultrasonographic examinations and urinalysis were performed for all dogs on 0 day before induction, on the 5th day, and on the 10th day of induction. The results of the current study showed significant increase in plasma level of SDMA, serum urea, creatinine, phosphorus, and potassium and a significant decrease in serum sodium, calcium, and chloride on the 5th day and 10th day of induction, and there was an increase in renal cortical echogenicity of the right and left kidney compared to adjacent liver and spleen, respectively. RI value showed a significant increase on the 5th day and 10th day of induction. The present study showed that SDMA is a sensitive and promising biomarker for diagnosis of acute kidney injury in dogs compared to routine biomarkers; also, the RI of Doppler ultrasonography is useful for early identifying acute kidney injury when the only observable change is an increase in cortical echogenicity.

Imaging techniques in Veterinary Medicine. Part I: Radiography and Ultrasonography

In Veterinary Medicine all the Imaging techniques are used and described but, due to organizational, managerial and, mostly, economical reasons, Radiography and Ultrasonography are the most used.

Veterinary Radiology teaching has a relatively small number of educational credits in the degree courses but, nowday, educational opportunities are remarkably increased thanks to a number of post-degree courses and masters, organized both by the universities and private veterinary associations. The relevance of Diagnostic Imaging is particularly true in Veterinary Medicine, in which Radiology could be considered “indispensable” for diagnosis, prognosis and follow up. Furthermore, it should not be forgotten that the diagnostic image represents a “document” and, has a relevant role in legal medical debats.

In this first part, Radiography and Ultrasonography are described.

Evaluation of the diagnostic value of the renal resistive index as a marker of the subclinical development of cardiorenal syndrome in MMVD dogs

Introduction:

Myxomatous mitral valve disease (MMVD) in dogs inevitably causes renal dysfunction. These interactions are known as the cardiorenal syndrome (CRS). The main aims of the study were to evaluate whether renal resistive index (RRI) may be useful as a non-invasive marker in subclinical stage of kidney injury in dogs with MMVD and to compare RRI with SDMA and Cyst C.

Methods:

Forty-four dogs were divided into two groups: control—15 healthy dogs and the heart group—29 dogs with MMVD (ACVIM class Cc). Study protocol included: anamnesis, clinical examination, electrocardiography, echocardiography, chest radiography, abdominal ultrasonography with measurements of the renal resistive index (RRI), urine, and blood analysis.

Results:

The RRI in the heart group was significantly higher 0.725 ± 0.035 versus control group 0.665 ± 0.028 (p < 0.00085). The RRI cut-off point in dogs with stable chronic heart failure (CHF) under 8 years is 0.775, in older 0.64. RRI was similar in MMVD dogs treated with ACE-I + furosemide and dogs treated ACE-I + torasemide + pimobendan + spironolactone. There was no correlation between RRI and SDMA or Cyst C.

Conclusion:

RRI is more sensitive than creatinine, SDMA and Cyst C to reveal kidney injury in MMVD dogs class Cc younger than 8 years.

Transabdominal Renal Doppler Ultrasound in Healthy Adult Holstein-Friesian Cows: A Pilot Study

Simple Summary

Knowledge of the physiological renal blood flow in cattle is essential for interpretation of Doppler ultrasound. In this paper, we describe a protocol for obtaining the renal Doppler parameters resistive index (RI) and pulsatility index (PI) in a systematic ultrasound evaluation of the kidney in cattle and provide preliminary reference values for healthy adult Holstein-Friesian cows.

Abstract

There is a notable lack of reference values for the renal resistive indices in the bovine kidney. Ultrasound (US) Doppler evaluation of these indices is a powerful, non-invasive technique for assessing, monitoring and diagnosing renal diseases in humans and other animals (e.g., small animals and horses). The aims of the present study were to establish a protocol for renal Doppler US in adult healthy Holstein-Friesian cows and to provide reference values for the renal resistive index (RI) and pulsatility index (PI). In cattle, the right kidney is always visible through a right abdominal window. Nevertheless, the left kidney is rarely accessible by transabdominal ultrasound. Doppler evaluation of the kidneys via a transabdominal approach is possible when accessible, but measurements can only be made in the larger vessels at the renal hilum. Normal RI and PI values were respectively 0.49 ± 0.07 and 0.70 ± 0.15 for the right kidney and 0.53 ± 0.05 and 0.79 ± 0.11 for the left kidney. We suggest an upper cut-off value for the RI of 0.63 and for the PI of 1.00 in healthy Holstein-Friesian cows. This is the first report describing normal values for the renal RI and PI in cattle that may be useful in future studies for characterizing different bovine pathologies that affect the renal parenchyma.

Changes in Renal Resistive Index Values in Healthy Puppies during the First Months of Life

The purpose of this study is to establish renal resistive index (RRI) of normal kidneys in puppies aged from newborn to 20 weeks of age and to determine the age at which RRI reaches adult dog values. Six healthy adult intact beagles and six puppies from 1 day after birth to 20 weeks of age were used. In the adult dogs, the ultrasonographic scans were performed once, and in the puppies, the ultrasonographic studies were performed on the first day after birth and at 1, 2, 3, 4, 6, 8, 12, 16, and 20 weeks of age. RRI was obtained at the interlobular and arcuate arteries in each kidney. There were no statistical differences between the RRI values obtained between the right and left kidney nor between intrarenal arteries (interlobar and arcuate). The RRI was the highest during the first weeks of life, after which it declined gradually with increasing age reaching adult dog values at 12 weeks of age. In conclusion, the normal mean RRI is age dependent in dogs. Twelve weeks can be regarded as the age at which adult mean RRI criteria can be applied to puppies.

Doppler evaluation of renal resistivity index in healthy conscious horses and donkeys

The renal resistive index (RRI) is used as a measurement of downstream resistance in arteries. The aim of this study was to assess the RRI of the arcuate arteries by pulsed-wave Doppler ultrasonography in healthy conscious horses and donkeys, and to verify any differences related to age, breed, bodyweight (BW) or body condition (BCS). Thirty-three healthy conscious horses and nine donkeys had their systolic and diastolic flow velocities at the level of the arcuate arteries estimated by pulsed-wave Doppler ultrasound, and the RRI was calculated. The relationship of RRI with age, breed (Trotters vs. other breeds), bodyweight (BW), and body condition score (BCS) were evaluated. PW Doppler evaluation of RRI was successfully applied in most of the horses, but to date not in the donkeys. In horses, median RRI values for the right kidney (0.58±0.006) were statistically higher than for the left (0.51±0.006). For the donkeys the values were comparable. There was no significant difference in RRI between horses younger or older than 15 years, and between breeds in horses. No correlation with age, BW or BCS was found in either horses or donkeys.

Ultrasonographic measurement of the renal resistive index in the cynomolgus monkey (Macaca fascicularis) under conscious and ketamine-immobilized conditions

Measurement of the renal resistive index (RRI) is one of the standard diagnostic procedures for assessing kidney disability clinically. This method is expected to be used for the same purpose in many kinds of animals, including monkeys utilized in conventional toxicology studies. To establish a practical RRI measurement procedure in cynomolgus monkeys (Macaca fascicularis), RRI was measured by ultrasonography in the spine position in conscious and ketamine-immobilized monkeys. The RRI of conscious monkeys and ketamine-immobilized monkeys could be measured consistently without excessive abdominal or thoracic movement. Consequently, the variability of the RRI in conscious monkeys was comparable to that in ketamine-anesthetized monkeys. No sex difference in RRI was noted between the two conditions. The mean values and SD of the RRI of 48 healthy monkeys (n=24/sex) were 0.55 ± 0.07 and 0.50 ± 0.05, under conscious and ketamine-immobilized conditions, respectively. The RRI of ketamine-immobilized monkeys was significantly lower than that of conscious monkeys, correlating with the decreased blood pressure and heart rate. In a monkey model of cisplatin-induced acute renal injury, which was characterized histopathologically by minimal to mild renal tubular necrosis and regeneration, the RRI was increased beyond the cut off value (mean + 2SD, 0.68) associated with the progression of renal pathogenesis. The present results suggest that ultrasonographic measurement of the RRI in conscious monkeys would be a useful tool in conventional toxicology studies evaluating drug-induced renal injury.

An assessment of the utility and repeatability of the renal resistive index in horses

The aim of this study was to establish the value of the renal resistive index (RI) of intrarenal arteries in healthy warmblood non-racing horses of different ages to assess the influence of physiologic factors and repeatability of measurement. The kidney ultrasonography examination was performed in three age groups: 15 foals, 15 adults and 15 elderly horses. The procedure was performed in unsedated standing animals. RI values were measured using pulsed-wave Doppler at the medial part of each kidney in the intrarenal arteries. To evaluate repeatability, all measurements were repeated two hours after the first examination. Statistical analysis of the relationship between groups was carried out using Fisher’s test. The relationship between the RI value and the physiological parameters was evaluated using linear regression. Repeatability of measurements was determined based on the Bland-Altman plot. The mean RI value in the studied horses was 0.48 ± 0.05 in the left kidney and 0.49 ± 0.05 in the right kidney. There were no statistically significant differences between the RI values in foals and adult horses. The elderly horses had a significantly higher RI value. Pulse pressure was the only physiological parameter affecting the RI value. The repeatability coefficient was 0.089 for the right kidney and 0.09 for the left kidney. The presented result suggest that elderly healthy horses have higher RI values than younger animals, which should be taken into account in clinical practice. The arterial pulse pressure should also be considered when interpreting RI values. The measurements have high repeatability, but in the authors’ opinion, this procedure is time consuming and requires experience.

Effects of medetomidine on intra-renal arteries resistive and pulsatility indices in clinically normal adult domestic shorthair cats

The aim of this study was to determine the effects of intramuscular injection of medetomidine on intra-renal arteries resistive and pulsatility indices by duplex Doppler ultrasonography in clinically normal adult domestic shorthair cats. For this purpose, twenty-six neutered adult healthy domestic shorthair cats (13 females and 13 males) were evaluated. B-mode, color Doppler and pulsed wave Doppler ultrasonography of right and left kidneys were performed to record the resistive index (RI) and pulsatility index (PI) of intra-renal arteries. To minimize statistical errors, the mean RI and PI were determined for each kidney by averaging three waveforms from the intra-renal arteries. Twenty-four hr later, the cats were sedated by 0.04 mg kg-1 intramuscular administration of medetomidine. All the Doppler measurements were repeated 15 min after drug administration. Mean ± standard deviation )SD( of PI and RI of the intra-renal arteries before administration of intramuscular medetomidine were 1.03 ± 0.08 and 0.61 ± 0.02, respectively. Fifteen min after medetomidine administration, the mean ± SD of PI and RI values were 1.04 ± 0.08 and 0.61 ± 0.02, respectively. Significant differences were not detected in mean PI and RI values before and 15 min after drug administration. Our findings showed that intramuscular administration of medetomidine does not cause significant hemodynamic changes in the intra-renal arteries after 15 min.

Influence of ageing on quantitative contrast-enhanced ultrasound of the kidneys in healthy cats

The degenerative effects of ageing on the kidneys have been extensively studied in humans. However, only recently interest has been focused on renal ageing in veterinary medicine. Contrast-enhanced ultrasound allows non-invasive evaluation of renal perfusion in conscious cats. Renal perfusion parameters were obtained in 43 healthy cats aged 1-16 years old, and the cats were divided in four age categories: 1-3 years, 3-6 years, 6-10 years and over 10 years. Routine renal parameters as serum creatinine, serum urea, urine-specific gravity, urinary protein:creatinine ratio and systolic blood pressure were also measured. No significant differences in any of the perfusion parameters were observed among the different age categories. A trend towards a lower peak enhancement and wash-in area under the curve with increasing age, suggestive for a lower blood volume, was detected when comparing the cats over 10 years old with the cats of 1-3 years old. Additionally, no significant age-effect was observed for the serum and urine parameters, whereas a higher blood pressure was observed in healthy cats over 10 years old.

Contrast-Enhanced Ultrasound Examination for the Assessment of Renal Perfusion in Cats with Chronic Kidney Disease

Background

Contrast‐enhanced ultrasound examination (CEUS) is a functional imaging technique allowing noninvasive assessment of tissue perfusion. Studies in humans show that the technique holds great potential to be used in the diagnosis of chronic kidney disease (CKD). However, data in veterinary medicine are currently lacking.

Objectives

To evaluate renal perfusion using CEUS in cats with CKD.

Animals

Fourteen client‐owned cats with CKD and 43 healthy control cats.

Methods

Prospective case‐controlled clinical trial using CEUS to evaluate renal perfusion in cats with CKD compared to healthy control cats. Time‐intensity curves were created, and perfusion parameters were calculated using off‐line software. A linear mixed model was used to examine differences between perfusion parameters of cats with CKD and healthy cats.

Results

In cats with CKD, longer time to peak and shorter mean transit times were observed for the renal cortex. In contrast, a shorter time to peak and rise time were seen for the renal medulla. The findings for the renal cortex indicate decreased blood velocity and shorter total duration of enhancement, likely caused by increased vascular resistance in CKD. Increased blood velocity in the renal medulla has not been described before and may be because of a different response to regulatory factors in cortex and medulla.

Conclusions and Clinical Importance

Contrast‐enhanced ultrasound examination was capable of detecting perfusion changes in cats with CKD. Further research is warranted to assess the diagnostic capabilities of CEUS in early stage of the disease process.

Ultrasonographically determined renal values and comparisons to serum biochemistry renal variables in aged semi-captive cheetahs (Acinonyx jubatus)

Background

Cheetahs in captivity have a high prevalence of chronic renal diseases. We ultrasonographically evaluated the renal volumes, a variety of renal dimensions, interarcuate artery resistive indices (RI) as well as aortic diameters and the length of the ventral aspect of the 6th lumbar vertebrae in 27 aged semi-captive anesthetized cheetahs. Renal size, dimensions and ratios were compared to urine specific gravity, serum creatinine and urea values.

Results

There were minimal differences for all values between left and right kidneys. Mean kidney length was 65.1 mm (range 55.2–76.9) with left kidney length ratios to L6 length being 1.60 (range 1.27–2.06) and to the aortic diameter 7.69 (range 4.54–10.72). Significant correlations between left renal length as well as length:L6 ratio to creatinine values were found ((r − 0.66) and (r − 0.60) respectively). The mean RI values of the different sedation/anesthetic protocols ranged from 0.46–0.55.

Conclusions

Left renal length and L6 ventral vertebral body length as well as left kidney RI values should be routinely measured in all cheetah abdominal ultrasound examinations. These measurements, together with serum creatinine, urea and urine specific gravity values may be relatively sensitive indicators of early renal pathology in the absence of gross ultrasonographic changes.

Pilot study to evaluate the potential use of the renal resistive index as a preliminary diagnostic tool for chronic kidney disease in cats

Objectives Chronic kidney disease (CKD) is the most common renal pathology diagnosed in geriatric cats, and its prevalence increases with age. The arterial resistive index (RI) is important when evaluating vascular resistance and compliance, and can be applied in the kidney (renal RI [RRI]), allowing the evaluation of its vascular haemodynamics. The present study aimed to: (1) investigate in cats with CKD the relationships between the RRI and the following parameters: age, sex, body weight, plasmatic creatinine, blood urea nitrogen, potassium, urine specific gravity, urine protein:creatinine ratio and systolic arterial pressure; and (2) evaluate the potential use of the RRI as a preliminary diagnostic tool in cats with CKD. Methods The present study involved 24 cats of both sexes. Six were healthy cats (control group [CG]) and 18 had CKD, but did not have any concomitant diseases and were not being treated with any medications (study group [SG]). For RRI measurement we used colour Doppler ultrasound (CDUS). Results RRI differed significantly between the CG and SG ( P <0.01) and was higher in the SG. A statistically significant correlation was only achieved between the RRI and the body weight of the patients and it was negative. A strong and positive correlation was noted between the mean RRI of both kidneys (r = 0.66). Receiver-operating curve analysis allowed us to establish an admissible cut-off for the RRI value of 0.639 for a preliminary diagnosis of CKD for both kidneys. Conclusions and relevance No differences were found for the RRI between the left and right kidneys, suggesting that evaluation of only one kidney is sufficient to provide an estimate of the RRI value for both organs. RRI measurement, which can be achieved with CDUS, is an easy-to-use diagnostic tool that, with a cut-off value of 0.639 for both kidneys, is useful in establishing a preliminary diagnosis of CKD.

KETAMINE-MEDETOMIDINE AND KETAMINE-MEDETOMIDINE-MIDAZOLAM ANESTHESIA IN CAPTIVE CHEETAHS (ACINONYX JUBATUS)-COMPARISON OF BLOOD PRESSURE AND KIDNEY BLOOD FLOW

Six clinically healthy captive cheetahs ( Acinonyx jubatus ) were anesthetized twice using two different drug combinations to investigate if blood pressure and kidney blood flow are affected by medetomidine dosage. Protocol KM (2.0 mg/kg ketamine and 0.05 mg/kg medetomidine) was compared with protocol KMM (2.0 mg/kg ketamine, 0.02 mg/kg medetomidine, and 0.1 mg/kg midazolam). Heart rate (HR), respiratory rate (RR), body temperature, end-tidal carbon dioxide pressure (ETCO₂), and anesthetic depth were monitored every 10 min. Noninvasive mean (MAP), systolic (SAP), and diastolic (DAP) arterial blood pressure were measured, and Duplex Doppler ultrasonography was performed on the kidneys. The mean arterial resistive index (RI) was determined and the pulse pressure index (PPI) was calculated, as indicators for kidney blood flow. There were no significant differences in induction and recovery times. MAP was significantly higher with KM than KMM at 35 min, and in both protocols decreased significantly after atipamezole administration. DAP was significantly higher at 25 and 35 min in animals anesthetized with KM; it also decreased significantly with both protocols after atipamezole administration. The PPI was significantly lower throughout the procedure with KM, and with both protocols increased significantly after atipamezole administration. Both the higher blood pressure and the reduced PPI with KM were likely a direct effect of the higher medetomidine dosage, and these findings indicate that lower medetomidine dosages might reduce hypertension and lead to a better PPI in cheetah immobilization.