Use of fine-wire electrodes for electromyographic evaluation of the external urethral sphincter during urethral pressure profilometry in male cats

Evaluation of urethral pressure profilometry (UPP) with simultaneous fine-wire electromyography of the external urethral sphincter (EUS) was conducted in 11 healthy adult male cats sedated with xylazine and ketamine. A 3.5-F urethral catheter with a closed end and two 1-mm side-ports was infused with sterile 0.9% NaCl solution at a rate of 2 to 3 ml/min. A fine-wire electromyographic (EMG) electrode was placed percutaneously into or near the external urethral sphincter prior to the onset of the UPP. The maximal urethral pressure achieved and functional profile length were recorded from UPP. Setting both catheter withdrawal rate and paper speed at 5 mm/s enabled the measurement of actual urethral length directly from UPP. Sphincter EMG activity was rated as slight (+), moderate (+ +), or intense (+ + +). All recordings were replicated once during each trial for 8 cats and trials were replicated 5 to 7 days later in 4 cats. Before catheterization, EMG activity of the external urethral sphincter was rated slight (+), whereas intense (+ + +) activity accompanied insertion. The activity evoked by movement of the catheter subsided, but intense EMG activity of the external urethral sphincter was recorded from onset to completion of catheter withdrawal in all cats in both trials. The mean maximal urethral pressure was 93.1 +/- 13.29 cm H2O. The mean function urethral length was 8.1 +/- 0.93 cm. Maximal urethral pressure or function profile length did not differ significantly between recordings within trials or between trials. Simultaneous recording of EMG activity and UPP of the external urethral sphincter was shown to be a simple, noninvasive technique for assessing neuromuscular and anatomic urethral function.     

Simultaneous cystometry and uroflowmetry for evaluation of micturition in two dogs

A recently developed urodynamic testing procedure was used to evaluate disorders of micturition in 2 dogs. The procedure simultaneously recorded intravesical pressure and urine flow during micturition. In an 11-year-old spayed female Sheltie that could not urinate normally, a micturition study demonstrated functional outflow obstruction of the urinary bladder. Although the urethra was patent, the urethral resistance factor, as calculated from pressure and flow data, was extremely high during voiding efforts. A urethral transitional cell carcinoma along with secondary infection, inflammation, and fibrosis were found to be responsible for the dog's problem. Ability to urinate was restored following removal of the affected portion of the urethra. In a 6-year-old spayed female Doberman Pinscher with urinary incontinence during sleep, a micturition study demonstrated urethral incompetence. During infusion of 0.9% NaCl solution into the bladder, the fluid flowed through the urethra before the detrusor muscle contracted, and urethral resistance during voiding was low. The dog's incontinence was responsive to estrogen administration.     

Effects of ketamine on electroencephalographic and autonomic arousal and segmental reflex responses in the cat

Objective To provide evidence concerning doses of ketamine that affect electroencephalographic (EEG) and autonomic signs of arousal during nociceptive stimulation. Study design Prospective psychophysical test in people. Single injection or progressively increasing infusions of ketamine in cats. Animals and people Seven people (20–60 years old) and three cats (3–5 kg) for EEG recording and six cats for EMG recordings. Methods In order to define innocuous and nociceptive stimulus intensities which could be applied to cats to evaluate arousal, psychophysical evaluations of sensations elicited by compression of the skin overlying phalangeal bones of the hand were obtained from human subjects. Then, following administration of ketamine, recordings of EEG frequency and of autonomic responses (heart rate, respiratory rate and arterial blood pressure) were obtained before and during stimulation of the tails of cats at pressures identified by human observers as either innocuous or nociceptive. Observations of withdrawal reflexes of the hindlimbs following interdigital skin stimulation were interposed between recording periods. In separate sessions, stretch reflex activity was assessed during awake and anesthetic conditions by recording electromyographic activity from soleus muscles and resistive force to dorsiflexion of the tibiotarsal joint. Results There were no changes in either total EEG (0.5–30.0 Hz), low‐frequency (0.6–7.5 Hz) or high‐frequency (7.5–30.0 Hz) power produced by nociceptive stimulation for a period of 18–24 minutes following an intramuscular bolus dose of ketamine (33.0 mg kg^?1), although withdrawal reflexes were present. Thereafter, nociceptive stimulation produced EEG arousal responses in the low‐frequency and total power range and increased systolic blood pressure and respiration rate. In tests after intravenous infusion of ketamine (10.0–22.2 mg kg^?1 hour^?1), total and low‐frequency EEG power and autonomic responses to nociceptive stimulation were eliminated. Organized motor responses were never elicited during IV infusion, but withdrawal reflexes were observed at each dosage. Also, stretch reflexes were shown by quantitative analysis to be retained at all doses of ketamine infusion. Conclusions and clinical relevance These results show that testing of withdrawal reflexes does not reveal the adequacy of ketamine anesthesia. Segmental stretch and withdrawal reflexes are preserved and can be investigated during infusion of ketamine at doses that eliminate arousal from brief periods of nociceptive stimulation.     

Urodynamic testing in the diagnosis of small animal micturition disorders

Urodynamic testing provides a quantitative assessment of the function of the small animal lower urinary tract. Most commonly these techniques are utilized to assess urethral tone (urethral pressure profile or UPP) and bladder detrusor muscle function (cystometrogram or CMG). A UPP may be indicated in cases of canine and feline micturition disorders. Examples include suspected primary sphincter mechanism incontinence (PSMI), ureteral ectopia, other congenital abnormalities, suspected neurological disorders, and mechanical or functional urethral obstruction. A UPP can be performed effectively utilizing human dedicated equipment. A CMG may be indicated to assess detrusor function in all of the above cases as well as cases of suspected atonic or infiltrated urinary bladder. This procedure can also be performed using the same human equipment. These tests are useful not only in providing an accurate diagnosis, but also in providing a sensitive prognostic indicator for clinical outcome of micturition disorders with and without pharmacological or surgical therapy. A leak pressure point may also be established in dogs with urinary incontinence, and may be even more sensitive than a UPP to predict clinical incontinence in some cases.     

Pathophysiology,Clinical Importance,and Management of Neurogenic Lower Urinary Tract Dysfunction Caused by Suprasacral Spinal Cord Injury

Management of persistent lower urinary tract dysfunction resulting from severe thoracolumbar spinal cord injury can be challenging. Severe suprasacral spinal cord injury releases the spinal cord segmental micturition reflex from supraspinal modulation and increases nerve growth factor concentration in the bladder wall, lumbosacral spinal cord, and dorsal root ganglion, which subsequently activates hypermechanosensitive C‐fiber bladder wall afferents. Hyperexcitability of bladder afferents and detrusor overactivity can cause urine leaking during the storage phase. During urine voiding, the loss of supraspinal control that normally coordinates detrusor contraction with sphincter relaxation can lead to spinal cord segmental reflex‐mediated simultaneous detrusor and sphincter contractions or detrusor‐sphincter dyssynergia, resulting in inefficient urine voiding and high residual volume. These disease‐associated changes can impact on the quality of life and life expectancy of spinal‐injured animals. Here, we discuss the pathophysiology and management considerations of lower urinary tract dysfunction as the result of severe, acute, suprasacral spinal cord injury. In addition, drawing from experimental, preclinical, and clinical medicine, we introduce some treatment options for neurogenic lower urinary tract dysfunction that are designed to: (1) prevent urine leakage arising because of detrusor overactivity during bladder filling, (2) preserve upper urinary tract integrity and function by reducing intravesical pressure and subsequent vesicoureteral reflux, and (3) prevent urinary tract and systemic complications by treating and preventing urinary tract infections.     

Diuretic effects of fenoldopam in healthy cats

Objective: To determine the effect of fenoldopam infusion on urine output, sodium excretion, creatinine clearance, and indirect blood pressure in healthy cats. Design: Prospective study. Setting: Veterinary medical teaching hospital. Animals: Eight purpose‐bred cats, 2–4 years old. Interventions: None. Measurements: Urine output was measured hourly for 12 hours before and after fenoldopam administration. Sodium excretion, modified creatinine clearance, and fractional sodium excretion were measured before and following fenoldopam administration. Urine specific gravity, central venous pressure, and systolic blood pressure were measured every 4 hours during the experiment. Main results: Compared with pre‐infusion values, urine output, sodium excretion, and fractional excretion of sodium increased significantly 6 hours after initiation of fenoldopam infusion. This increase was sustained throughout the observation period. The modified creatinine clearance decreased significantly following 2 hours of fenoldopam infusion, but increased significantly by 6 hours after infusion, the time of peak urine output. Changes in urine specific gravity mirrored changes in fractional sodium excretion, whereas the central venous pressure mirrored changes in modified creatinine clearance. The diuretic effect in cats was prevented when a dopamine receptor blocking agent was administered before fenoldopam infusion. Conclusion: Fenoldopam at a dose of 0.5 μg/kg/min induces diuresis in cats in a delayed manner. This increase appears to be due, in part, to dopamine receptor‐induced natriuresis. Changes in glomerular filtration rate may also occur.     

Results of analyses and bacterial cultures of urine specimens obtained from clinically normal cats by three methods

Six urine specimens were obtained from each of 6 male and 6 female cats in a 3-week period. The first and last specimens from each cat were obtained by cystocentesis, 2 were obtained by urethral catheterization, and 2 were caught during voiding stimulated by manual bladder compression. Quantitative urine cultures did not reveal bacteriuria in specimens obtained by cystocentesis, and urinary tract infection did not develop during the study. Bacteria were found in 3 (25%) of 12 urine specimens obtained by catheterization of males and in 1 (8%) of 12 specimens obtained by catheterization of females. Magnitude of bacteriuria in specimens obtained by catheterization was 10 to 1,000 organisms/ml. Bacteria also were found in specimens obtained during voiding. Each of 11 (100%) cleanly caught specimens obtained from males and 7 (58%) of 12 voided specimens from females contained bacteria. Magnitude of bacteriuria in voided specimens was usually 100 to 10,000 organisms/ml, but 3 voided specimens contained greater than 10,000 organisms/ml. Many bacteriuric specimens contained more than 1 type of organism; however, bacteria that might be suspected of causing urinary tract infections in cats were found frequently. Urinalyses were performed on 66 specimens. Completeness of urinalyses depended on the volume of specimens available, but results were normal except for evidence of hematuria in a few specimens obtained by cystocentesis or catheterization. Hematuria was usually mild and was attributed to hemorrhage caused by minor urinary tract trauma during urine collection.     

Central diabetes insipidus in five cats: clinical presentation, diagnosis and oral desmopressin therapy

Five cases of central diabetes insipidus (CDI) in domestic shorthair cats are described. All cats were under 3 years of age at the onset of clinical signs, and outdoor or outdoor/indoor cats, in which a prior trauma was either present or possible. The history included polydipsia and polyuria, and physical examination abnormalities included urinary bladder distention and dehydration. All cats had hyposthenuria with a urine specific gravity between 1.003 and 1.006. The diagnosis was confirmed by an observed inability to concentrate urine during a water deprivation test or compatible serum osmolality, followed by an increase in urine concentration after desmopressin administration. All cats in this report were treated successfully with oral desmopressin. The dose (25-50 microg q8-12h) and the response to therapy were variable. Oral desmopressin administration may serve as an effective alternative route for cat owners who find the conjunctival or nasal application of the solution an inconvenient mode of therapy.     

Feasibility of Implant Driven Micturition in Paraplegic Dogs

Objective — This study evaluates the feasibility of using existing technology for implant driven micturition in paralyzed dogs (part I) and also examines a less invasive technique for implant driven micturition (part II). Study Design — Part I. Sacral nerve root dimensions and bladder and urethral pressure responses to intradural and extradural sacral nerve root stimulation were measured to determine the optimal location and size for sacral nerve root electrodes. Part II. Sacral nerve roots were stimulated via wire electrodes introduced into the S2 foramina. Animals or Sample Population — Ten dogs (five dogs in part I and five dogs in part II). Methods — Part I. Microtip pressure transducers were used to monitor bladder and urethral pressure responses to sacral nerve root stimulation with tripolar hook electrodes. After euthanasia, sacral nerve root, and spinal canal dimensions were measured. Part II. Bipolar electrical stimulation of the sacral nerve roots was performed by introducing wire electrodes into the S2 foramina. Bladder and urethral pressures were recorded as in part I. Results — Part I. Stimulation of S1 produced an increase in urethral, but not bladder, pressure. Stimulation of S2 or S3 produced increases in bladder pressure and decreases in urethral pressure. Intradural and extradural nerve roots were not significantly different with respect to nerve dimensions or effects on nerve stimulation. Part II. High bladder pressures were achieved, but effective voiding could not be produced, primarily because of urethral resistance. Conclusions — Part I. Extradural implantation was determined to be the most appropriate site based on ease of dissection, nerve root dimensions, and decreased risk of iatrogenic trauma. Enough space is available to implant two to four tripolar spiral nerve cuffs. Part II. Transforaminal sacral nerve root stimulation did not effectively empty the bladder. Clinical Relevance — Clinical trials in paraplegic dogs are necessary to evaluate the number of sacral nerve cuff electrodes necessary to produce effective bladder emptying.     

Radiologic study of the canine urethra

The structure and function of the canine urethra were studied during retrograde and voiding urethrography in 9 male and 8 female dogs. The lumen of the prostatic portion of the urethra was variable in diameter. During retrograde urethrography, the lumen was narrow with streaks of contrast medium outlining mucosal folds, but during voiding, it was dilated and a spindle-shaped seminal hillock was detected. Retrograde urethrography revealed other regions of the urethra of males and females had a smooth radiographic outline. During voiding urethrography, characteristic identical urethral contractions were observed in the caudal portion of the pelvic urethra (male) and in the caudal half of the urethra (female). Contractions were progressive, occurred where striated muscle was present in the urethral wall, and resulted in an intermittent flow of urine from the urethra. In the male, contractions had a rate of 2.02 +/- 0.23 contraction/s and 1.65 +/- 0.53 in the females. Contractions may have a role in the controlled voiding of small volumes of urine necessary for the repeated marking of territory, in the passage of the ejaculate along the male urethra during copulation, and in the clearance of any residual urine from the urethra at the completion of micturition.     

Cystocentesis is essential for reliable diagnosis of urinary tract infections in cats

Urine samples were taken from 79 cats with clinical signs of acute feline lower urinary tract disease (FLUTD) by means of cystocenthesis, catheterization, or at voiding and were cultured. No bacteria were cultured from 79% of the samples taken by cystocenthesis, 55% of the samples obtained by catheterization, and 17% of the samples obtained at voiding. Samples obtained by cystocenthesis most often yielded pure cultures, whereas the voided samples were often contaminated, yielding mixed cultures. Therefore, it is difficult to interpret culture results for voided or catheterized urine samples, which may lead to overdiagnosis of urinary tract infections. E. coli was the most prevalent bacterial species. Numbers of bacteria were low (10(2) to 10(3)/ml) in three out of eight culture-positive samples taken by cystocenthesis, indicating that the number of bacteria present in the bladder of cats with urinary tract infections may be low. This may lead to underdiagnosis of urinary tract infections when interpreting culture results for voided and catheterized samples, because bacterial counts lower than 10(3) colony-forming units/ml of urine are generally considered not clinically relevant. In conclusion, cystocenthesis is the preferred method of sampling for the evaluation of cats with suspected urinary tract infection.     

Corynebacterium urealyticum urinary tract infection in dogs and cats: 7 cases (1996-2003)

OBJECTIVE: To identify clinical features of Corynebacterium urealyticum urinary tract infection in dogs and cats and antimicrobial susceptibility patterns of C urealyticum isolates. DESIGN: Retrospective study. ANIMALS: 5 dogs and 2 cats. PROCEDURE: Medical records of dogs and cats for which C urealyticum was isolated from urine samples were reviewed. Isolates from clinical cases, along with previously lyophilized unsubtyped isolates of Corynebacterium spp collected between 1977 and 1995, were examined and, if subtyped as C urealyticum, tested for antimicrobial susceptibility. RESULTS: Signalment of infected animals was variable. Prior micturition disorders were common, and all animals had signs of lower urinary tract disease at the time C urealyticum infection was diagnosed. Median urine pH was 8.0; WBCs and bacteria were variably seen in urine sediment. In vitro antimicrobial susceptibility testing of 14 C urealyticum isolates revealed that all were susceptible or had intermediate susceptibility to chloramphenicol, tetracycline, and vancomycin and most were susceptible to enrofloxacin. Thickening of the bladder wall and accumulation of sediment were common ultrasonographic findings. Contrast radiography or cystoscopy revealed findings consistent with encrusting cystitis in 3 dogs. Infection resolved in 2 dogs following surgical debridement of bladder plaques and antimicrobial administration. In 2 other dogs and 1 cat treated with antimicrobials, infection with C urealyticum resolved, but urinary tract infection with a different bacterial species developed. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that preexisting urinary tract disorders are common in dogs and cats with C urealyticum infection. Treatment with appropriate antimicrobials in combination with surgical debridement might eliminate C urealyticum infection.     

Retrograde flow of spermatozoa into the urinary bladder of rams

Retrograde flow of spermatozoa into the urinary bladder of rams during electroejaculation (EE) was examined. In experiment 1, semen and 4 consecutive samples of the urine released during the first post-EE micturition were collected once a week from 6 rams for 5 weeks during the nonbreeding season. The overall mean concentration per milliliter and the mean total number of spermatozoa in the urine ranged from 3.06 to 4.32 X 10(6) and from 80 to 2,865 X 10(6), respectively. The spermatozoal concentration in sequential urine samples was not different between samples, indicating that these spermatozoa had mixed with the urine before micturition. The percentage of the total number of spermatozoa displaced during EE, which flowed into the urinary bladder (retrograde flow), varied among rams (range 3.9% to 80%). The overall mean percentage of retrograde flow during the nonbreeding season was 28.3%. In experiment 2, a catheter was implanted into the urinary bladder of 6 rams (4 rams were from experiment 1), and semen was collected over 4 weeks during the subsequent breeding season. A urine sample was collected from the implanted catheter before EE. Immediately after semen collection, urine was collected by evacuating the bladder. The spermatozoal concentration in the pre-EE urine ranged from 0 to 1.3 X 10(6) (mean +/- SD, 0.17 +/- 0.38 X 10(6)) and was significantly (P less than 0.0001) lower than the spermatozoal concentration in the post-EE urine, which ranged from 1.10 to 22.55 X 10(6) (mean +/- SD, 9.46 +/- 11.30 X 10(6)).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of asphyxia and potassium on canine and feline electrocardiograms.

The effects of asphyxia and potassium on the electrocardiogram (ECG), lead II, were recorded from dogs and cats anesthetized with sodium pentobarbital and halothane. Electrocardiographic recordings were made during control periods, during asphyxia (occluded endotracheal tube), during infusion of an isotonic KCl solution and during infusion of an isotonic NaCl solution. Arterial and venous blood gas partial pressures (PaCO2, PvCO2, PaO2 and and PvO2), plasma Na+ and K+ concentrations, heart rate and mean arterial blood pressure were measured during control periods, asphyxia and during the periods of infusion. The vagi were severed to assess the effect of vagal tone on the ECG changes. The characteristic ECG changes during asphyxia and the electrolyte imbalances resulting from infusion of isotonic KCl and NaCl were determined during sodium pentobarbital and halothane anesthesia in both dogs and cats. The combination of halothane and high PCO2 caused cardiac arrhythmias. Spontaneous recovery from ventricular fibrillation, as a result of hyperkalemia, was recorded from cats. Disappearance of the P waves, which is characteristic of hyperkalemia, was infrequent in this study and the U waves associated with hypokalemia were not found. Severing the vagi did not alter the ECG changes characteristic of asphyxia, hyperkalemia and hypokalemia. It was found that asphyxia and infusion of fluids high or low in potassium can produce ECG changes in both dogs and cats that can be correlated with blood gas partial pressure changes or plasma potassium concentrations.     

Amoxycillin and clavulanic acid combination in the treatment of experimentally induced bacterial cystitis in cats

Clavulanic acid (CA) competitively inhibits beta-lactamase hydrolysis of penicillins in vitro. Treatment with amoxycillin combined with clavulanic acid (A-CA) was compared with placebo in a blind study in cats with experimental cystitis caused by Escherichia coli demonstrating in vitro resistance to amoxycillin. Bacterial cystitis was induced in 20 cats by bladder infusion of 5 ml of 0.05 per cent alcoholic salicylic acid followed after 24 hours by a brain-heart infusion broth of E coli (10(8) colony forming units ml-1) previously found to be resistant to amoxycillin in vitro (minimum inhibitory concentration over 512 micrograms ml-1). Four days after infection, cats were randomly divided into two groups of 10 and treated with amoxycillin combined with clavulanic acid or placebo for 10 days. When compared to the placebo-treated group, the A-CA treated group showed: reduced quantitative bacterial counts in urine on days 7 (P less than 0.001) and 14 (P less than 0.02); reduced culture positive urine on days 7 (P less than 0.001) and 14 (P less than 0.001); and less severe inflammation on histological examination of the bladder and urethra (P less than 0.01). It was concluded that A-CA was effective in reducing the bacterial count and reducing the histopathological changes in the bladder and urethra in an experimental model of acute bacterial cystitis in cats infected with an E coli demonstrating in vitro resistance to amoxycillin.     

Evaluation of the effects of stress in cats with idiopathic cystitis

OBJECTIVE: To determine the effects of stress in cats with feline idiopathic cystitis (FIC) by evaluating bladder permeability, sympathetic nervous system function, and urine cortisol:creatinine (C:Cr) ratios during periods of stress and after environmental enrichment. DESIGN: Prospective study. ANIMALS: 13 cats with FIC and 12 healthy cats. PROCEDURE: Cats subjected to an acute-onset moderate stressor for 8 days received IV injections of fluorescein. Serum fluorescein concentrations were determined and compared with those of controls to evaluate bladder permeability, and urine C:Cr ratios were compared to evaluate function of the hypothalamic-pituitary-adrenal (HPA) axis. Plasma catecholamine concentrations were analyzed in a subset of cats. After 8 days of moderate stress, cats were moved to an enriched environment, and tests were repeated after 21 days. RESULTS: Serum fluorescein concentrations were significantly higher in cats with FIC at all time points. In the cats in which plasma catecholamine concentrations were determined, concentrations of dihydroxyphenylalanine, norepinephrine, and dihyroxyphenylglycol were significantly higher in cats with FIC at all time points, whereas no differences in urine C:Cr ratio between groups were observed. CONCLUSION AND CLINICAL RELEVANCE: Cats with FIC appeared to have altered bladder permeability, most notably during the period of initial stress. The increase in plasma dihydroxyphenylalanine concentration suggests that there may be stress-induced increase in the activity of tyrosine hydroxylase, which catalyzes the rate-limiting step in catecholamine synthesis. In contrast, no effects of stress on C:Cr ratios were observed, which suggests there was dissociation between the sympathetic nervous system and HPA-axis responses to stress.     

ASSOCIATIONS BETWEEN ULTRASOUND AND CLINICAL FINDINGS IN 87 CATS WITH URETHRAL OBSTRUCTION

Urethral obstruction is a life‐threatening form of feline lower urinary tract disease. Ultrasonographic risk factors for reobstruction have not been previously reported. Purposes of this retrospective cross‐sectional study were to describe urinary tract ultrasound findings in cats following acute urethral obstruction and determine whether ultrasound findings were associated with reobstruction. Inclusion criteria were a physical examination and history consistent with urethral obstruction, an abdominal ultrasound including a full evaluation of the urinary system within 24 h of hospitalization, and no cystocentesis prior to ultrasound examination. Medical records for included cats were reviewed and presence of azotemia, hyperkalemia, positive urine culture, and duration of hospitalization were recorded. For medically treated cats with available outcome data, presence of reobstruction was also recorded. Ultrasound images were reviewed and urinary tract characteristics were recorded. A total of 87 cats met inclusion criteria. Common ultrasound findings for the bladder included echogenic urine sediment, bladder wall thickening, pericystic effusion, hyperechoic pericystic fat, and increased urinary echoes; and for the kidneys/ureters included pyelectasia, renomegaly, perirenal effusion, hyperechoic perirenal fat, and ureteral dilation. Six‐month postdischarge outcomes were available for 61 medically treated cats and 21 of these cats had reobstruction. No findings were associated with an increased risk of reobstruction. Ultrasonographic perirenal effusion was associated with severe hyperkalemia (P = 0.009, relative risk 5.75, 95% confidence interval [1.54–21.51]). Findings supported the use of ultrasound as an adjunct for treatment planning in cats presented with urethral obstruction but not as a method for predicting risk of reobstruction.     

Effects of remifentanil infusion regimens on cardiovascular function and responses to noxious stimulation in propofol-anesthetized cats

OBJECTIVE: To evaluate the effects of 2 remifentanil infusion regimens on cardiovascular function and responses to nociceptive stimulation in propofol-anesthetized cats. ANIMALS: 8 adult cats. PROCEDURES: On 2 occasions, cats received acepromazine followed by propofol (6 mg/kg then 0.3 mg/kg/min, i.v.) and a constant rate infusion (CRI) of remifentanil (0.2 or 0.3 microg/kg/ min, i.v.) for 90 minutes and underwent mechanical ventilation (phase I). After recording physiologic variables, an electrical stimulus (50 V; 50 Hz; 10 milliseconds) was applied to a forelimb to assess motor responses to nociceptive stimulation. After an interval (> or = 10 days), the same cats were anesthetized via administration of acepromazine and a similar infusion regimen of propofol; the remifentanil infusion rate adjustments that were required to inhibit cardiovascular responses to ovariohysterectomy were recorded (phase II). RESULTS: In phase I, heart rate and arterial pressure did not differ between remifentanil-treated groups. From 30 to 90 minutes, cats receiving 0.3 microg of remifentanil/kg/min had no response to noxious stimulation. Purposeful movement was detected more frequently in cats receiving 0.2 microg of remifentanil/kg/min. In phase II, the highest dosage (mean +/- SEM) of remifentanil that prevented cardiovascular responses was 0.23 +/- 0.01 microg/kg/min. For all experiments, mean time from infusion cessation until standing ranged from 115 to 140 minutes. CONCLUSIONS AND CLINICAL RELEVANCE: Although the lower infusion rate of remifentanil allowed ovariohysterectomy to be performed, a CRI of 0.3 microg/kg/min was necessary to prevent motor response to electrical stimulation in propofol-anesthetized cats. Recovery from anesthesia was prolonged with this technique.     

A comparison of cardiorespiratory variables during isoflurane-fentanyl and propofol-fentanyl anaesthesia for surgery in injured cats

OBJECTIVE: To compare haemodynamic and respiratory variables during isoflurane-fentanyl (IF) and propofol-fentanyl (PF) anaesthesia for surgery in injured cats. STUDY DESIGN: Prospective, randomized, controlled clinical study. ANIMALS: Thirty-three client-owned injured cats undergoing orthopaedic surgery. MATERIALS AND METHODS: Pre-anaesthetic medication was intravenous midazolam 1 mg kg(-1), butorphanol 0.4 mg kg(-1) and ketamine 2 mg kg(-1). Anaesthesia was induced with propofol (P) and maintained with either: (a) a continuous rate infusion (CRI) of fentanyl (F) 0.02 mg kg(-1) hour(-1) and isoflurane (initial end-tidal concentration of 1%), (b) a fentanyl CRI (dose as before) and sevoflurane (initial end-tidal concentration of 2%) or (c) a CRI of propofol (12 mg kg(-1) hour(-1)). All three techniques were given to effect until surgical anaesthesia was achieved. Heart rate and rhythm (ECG), mean arterial blood pressure, respiratory rate, tidal volume and end-tidal CO(2) concentration were recorded. Venous blood gas analysis was performed before and after sedation, and at the end of anaesthesia. Blood chemistry and blood cell counts were assessed before, at the end of, and 24 hours after anaesthesia. The variables recorded from cats anaesthetized with IF and PF were compared. RESULTS: Mean end-expiratory isoflurane concentration was 1.19 +/- 0.19%. The propofol infusion rate was 11.4 +/- 0.8 mg kg(-1) hour(-1). No significant differences between the two groups in heart rate were identified; no cardiac dysrhythmias were recorded. Mean arterial blood pressure was significantly lower in IF cats during skin incision (p = 0.01), during surgery without intense surgical stimulation (p < 0.01) and during surgery with intense surgical stimulation (p = 0.01). Nine of 11 cats in the IF group were markedly hypotensive (34-49 mmHg) while seven of 11 cats in group PF were mildly hypotensive (49-59 mmHg). One of 11 cats in group IF and nine of 11 cats in group PF required intermittent positive pressure ventilation (IPPV) to maintain end-tidal CO(2) levels below 6.66 kPa (50 mmHg). CONCLUSION AND CLINICAL RELEVANCE: Despite the necessity to ventilate the lungs of cats in the PF group, arterial blood pressure was better maintained. Propofol-fentanyl anaesthesia is better for surgery in injured cats providing the means to impose IPPV are available.     

Preservation of striated-muscle urethral sphincter function with use of a surgical technique for perineal urethrostomy in cats

It has been reported that perineal urethrostomy resulted in impairment of striated-muscle urethral sphincter function in male cats, as measured by urethral pressure profilometry and electromyography (EMG). Our study was undertaken to describe and evaluate a surgical technique for perineal urethrostomy that reduces trauma to the urethral branches of the pudendal nerve. Perineal urethrostomy was performed on 10 healthy neutered cats after demonstrating that they had normal urethral sphincter function by urethral pressure profilometry (maximal urethral closure pressure [MUCP] = 151 +/- 52 cm of water) and EMG activity at the level of the striated-muscle sphincter before surgery. All cats had normal urethral sphincter function 1 week (MUCP = 194 +/- 19 cm of water, EMG activity present) and 3 weeks (MUCP greater than 200 cm of water, EMG activity present) after surgery. These results indicated that preservation of the urethral branches of the pudendal nerve during urethrostomy preserved striated-muscle urethral sphincter function.