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Abstract

Objectives

The aim of this study was to evaluate the use of inhalant anesthesia vs sedation for urinary catheter placement in male cats with urethral obstruction. The primary outcome measures were the incidence of complications related to catheterization, the incidence of recurrent urethral obstruction (rUO; both during hospitalization and within 1 year) and survival. The secondary aim of this study was to evaluate the association between baseline serum biochemical concentrations and antispasmodic medications with complications and short-term rUO.

Methods

We carried out a retrospective review of records from a university teaching hospital from 2009 to 2020. Cats were included if diagnosed with a urinary obstruction, based on the presence of a large, painful and non-expressible bladder, a urinary catheter was placed and hospitalization occurred for a minimum of 24 h. Collected baseline data included age, breed, weight, serum biochemical concentrations and if cats underwent sedation or inhalant anesthesia for urethral catheterization. For the comparison of inhalant anesthesia or sedation, univariate logistic regression was used.

Results

There was no statistically significant difference in complications or the recurrence of obstruction in cats with urethral obstruction that underwent inhalant anesthesia compared with sedation. All serum biochemical concentrations were significantly associated with survival. Decreased serum ionized calcium was found to be statistically significantly associated with higher complication rates (P = 0.0086), as well as short-term recurrence of obstruction (P = 0.004). Increased serum potassium concentrations were found to be statistically significantly associated with the risk of short-term recurrent urethral obstruction (P = 0.0345). No significant difference was found between the use of antispasmodic medications with short-term recurrence.

Conclusions and relevance

No significant difference was found between complications or recurrence rates when comparing the use of inhalant anesthesia to sedation protocols. Baseline serum biochemical data were significantly associated with complications, survival and short-term recurrence rates.

Keywords

Feline urethral obstruction inhalant anesthesia recurrent urethral obstruction sedation urethral catheterization

Introduction

Feline urethral obstruction (UO) is a common emergency in male cats, accounting for up to 9% of annual emergencies.¹ Feline UOs occur secondarily to a wide variety of underlying etiologies of feline lower urinary tract disease (FLUTD). FLUTD encompasses conditions including feline idiopathic cystitis (FIC), urolithiasis and urinary tract infections.¹ Characteristic signs of FLUTD and UO include stranguria, hematuria and vocalization, which – if left untreated – can lead to life-threatening metabolic derangements and death.^1–3 Management of UO includes addressing metabolic derangements, such as azotemia and hyperkalemia, urinary catheterization to relieve the obstruction and tailored treatment of the primary etiology. The most common complication of UO is recurrent UO (rUO), which may necessitate repeated hospitalizations and surgical intervention, in the form a perineal urethrostomy (PU).¹

Generally, UO carries an excellent prognosis, with survival rates around 91%.⁴ However, rUO rates remain high, ranging from 22% to 57%.^4–6 The recurrence of UO results in increased patient morbidity and mortality, in addition to a significant financial burden. The recurrence of obstruction or cases refractory to medical management may lead to euthanasia in up to 20% of cases, highlighting the importance of the prevention of recurrence and effective management strategies.^4,7 Urethral spasms and inflammation have been hypothesized to contribute to the pathophysiology of obstructions and may predispose patients to rUO.^5,8,9 The level of consciousness and anesthetic depth play a role in urethral pressure, and decreased urethral pressure may facilitate catheterization and decrease the risk of urethral trauma, stricture and spasms.^10,11 Sedation and anesthetic protocols for the management or UO are variable, and there has been limited investigation regarding their association with outcome. The veterinary literature has found that the use of epidurals in conjunction with intravenous anesthesia is safe and effective, yet the association of protocols and recurrence rates has not been investigated.^12,13 Another study evaluated the use of propofol vs ketamine and diazepam, and found that propofol was associated with a quicker time to standing.¹⁴ No differences in biochemical concentrations were noted in this study; however, complication rates and rUO were not evaluated.¹⁴

The goal of this retrospective study was to investigate the use of inhalant anesthesia vs sedation in urinary catheterization and its association with the complications and incidence of rUO during hospitalization. We hypothesized that the use of inhalant anesthesia vs sedation in cats with UO would result in a lower complication rate, as well as a lower recurrence rate. The secondary objectives of this study were to evaluate the association between presenting serum biochemical abnormalities, including blood urea nitrogen (BUN), creatinine, pH, potassium and ionized calcium (iCa), and the use of antispasmodic medications and complication rates, short-term rUO and survival.

Materials and methods

Case selection

Medical records from a university teaching hospital from the years 2009–2020 were searched for male cats presenting with a UO. Cats were included if they were diagnosed with a urinary obstruction based on the presence of a large, painful and non-expressible bladder on physical examination, a urinary catheter was placed and hospitalization occurred for a minimum of 24 h. Cats were excluded if catheterization was not performed, cats were managed on an outpatient basis, cats were euthanized on presentation or if they were transferred immediately for PU.

Data collection

Baseline data collected included age, breed and weight. Additional data collected included serum biochemical concentration at presentation, including BUN, creatinine, pH, potassium and iCa. The use of inhalant anesthesia or sedation for urinary catheter placement, in addition to re-obstruction within 24 h, re-obstruction within 1 year, complications and survival to discharge were evaluated. For the purpose of this study, inhalant anesthesia was defined as intubation and the use of gas inhalants. The use of any sedation medications, including anesthetic induction agents, without intubation and the use of inhalant gas was characterized as sedation. Complications noted included urethral stricture or tear, uroabdomen, fluid overload or congestive heart failure. Short-term re-obstruction was defined as obstruction occurring while in hospital or within the 24 h following discharge; long-term re-obstruction was defined as rUO within 1 year of the initial diagnosis.

Statistical analysis

The assumption of normality was verified using Shapiro–Wilk tests; the data were non-normally distributed and therefore presented as the median. All variables of interest were evaluated for their association with complications and rUO. Biochemical abnormalities and antispasmodic medications were also investigated for their relationship with survival. For the comparison of inhalant anesthesia or sedation, univariate logistic regression was used. For the assessment of serum biochemical abnormalities (BUN, creatinine, pH, potassium, iCa), multivariate logistic regression was used with all covariates included as the full model, then backwards model selection applied and the variance inflation factor calculated to measure the multicollinearity. Each univariate logistic regression was then performed to assess the effect of each individual covariate. To evaluate antispasmodic medications, the pairwise proportion test was used and then the Benjamini–Hochberg P value adjustment method was applied. For all analyses, P values <0.05 were considered to be statistically significant. Statistical analyses were performed using commercially available software (R version 4.0.3; R Foundation for Statistical Computing).

Results

A total of 238 cases of feline UO were identified between 2009 and 2020. Thirty-eight cases were excluded based on lack of urinary catheterization, treatment on an outpatient basis or transfer for immediate PU. Two hundred cases met the inclusion criteria and were included in the data collection and analysis. The median age of cats in this study was 5 years (range 1–16), with a median weight of 6 kg (range 3.29–12.2); the most common breed presented was domestic shorthair. The most common diagnosis was FIC (n = 184) followed by urolithiasis (n = 17); no other causes were identified. The survival rate for this study was 94.5%; 11 cats did not survive to discharge, all of which were euthanized. Seven cats were euthanized owing to concerns over the short- and long-term prognoses, while four were euthanized owing to financial constraints.

Of the 200 cases evaluated, 74 (37%) underwent inhalant anesthesia in combination with premedications, while 126 (63%) received sedation only for urinary catheterization. Drug protocols varied significantly, and 79 cats received more than one drug for sedation. The most utilized drug was propofol, with 66 cats receiving this. Forty-seven of these cats received propofol alone for urethral catheterization. Fifty-seven cats received an opioid as part of their sedation protocol: 31 received a benzodiazepine and 26 received ketamine. Less commonly utilized sedatives included dexmedetomidine, alfaxalone and acepromazine.

Overall, 36 cases (18%) developed rUO within 24 h and 37 cases (18.5%) developed rUO after the initial 24 h and within 1 year of diagnosis (Table 1). Complications included urethral tear (n = 2), stricture (n = 1), uroabdomen (n = 4), acute kidney injury (n = 1), congestive heart failure (n = 1), fluid overload (n = 2), ventricular arrhythmias (n = 2) and suspected uremic encephalopathy (n = 2). Congestive heart failure was diagnosed based on echocardiographic evidence of underlying heart disease and the development of pleural effusion, while fluid overload was based on the development of pleural effusion with no noted primary heart disease.

Table 1

Complications and recurrent urethral obstruction (rUO) between anesthesia and sedation groups

Outcome	Inhalant anesthesia (n = 74)	Sedation (n = 126)	P value
Complication	28 (38)	32 (25)	0.16
rUO	25 (34)	25 (20)	0.43

Data are presented as n (%)

Thirty-eight percent of cases (n = 28/74) undergoing inhalant anesthesia experienced a complication, while 25% of cases (n = 32/126) undergoing sedation experienced a complication. There was no statistically significant difference in the rate of complications between cats undergoing inhalant anesthesia and those undergoing sedation (P = 0.16). There was no statistically significant difference in rUO between cases undergoing either inhalant anesthesia or sedation for urinary catheterization (P = 0.43).

Baseline serum biochemical concentrations and their association with survival, complications and short-term rUO, including BUN, creatinine, pH, potassium and iCa, were evaluated (Table 2). BUN was found to be statistically significantly related to survival rate; for every 10 mg/dl decrease in BUN, the odds of survival increase by 1.25 (95% confidence interval [CI] 1.12–1.41; P <0.001). BUN was also found to be statistically significantly related to rUO. For every 10 mg/dl increase in BUN, the odds of short-term rUO increased by 1.07 (95% CI 1.01–1.16; P = 0.024). Serum creatinine was found to be statistically significantly related to survival rate. With every 1 mg/dl decrease in serum creatinine, the odds of survival increased by 1.17 (95% CI 1.06–1.30; P = 0.001). pH was found to be statistically significantly related to survival. For every 0.01 increase in pH, the odds of survival increase by 1.12 (95% CI 1.06–1.21; P <0.001). pH was also found to be statistically significantly related to short-term rUO. With every 0.01 decrease in pH, the odds of short-term rUO increased by 1.07 (95% CI 1.03–1.12; P <0.001).

Table 2

Biochemical concentrations measured at admission and statistical relation to outcomes

Variable	n	Median (range)	RI	Survival P value	Complication P value	rUO P value
BUN (mg/dl)	168	40 (11–257)	10–30	<0.001*	0.076	0.024*
Creatinine (mg/dl)	162	2.4 (0.7–22)	0.5–1.5	0.001*	0.539	0.110
pH	132	7.315 (6.92–7.51)	7.31–7.42	<0.001*	0.050	0.001*
K⁺ (mEq/l)	171	4.3 (3.2–10.68)	3.9–5.3	<0.001*	0.094	0.0345
iCa (mmol/l)	132	1.2 (0.64–1.38)	1.25–1.45	<0.001*	0.0086*	0.004*

Statistically significant t (P <0.05)

RI = reference interval; rUO = recurrent urethral obstruction; BUN = blood urea nitrogen; iCa = ionized calcium

Serum potassium concentrations were available in 171/200 cases evaluated. Median serum potassium concentrations were 4.3 mEq/l (range 3.2–10.68; reference interval [RI] 3.9–5.3). Serum potassium was found to be significantly associated with the rate of short-term rUO. For every 1 mEq/l increase in potassium, the odds of short-term rUO increased by 1.45 (95% CI 1.18–1.80; P <0.001). Serum iCa concentrations were available for 132/200 cases reviewed. Median serum iCa concentrations was found to be 1.2 mmol/l (range 0.64–1.38; RI 1.25–1.45). Serum iCa concentrations were found to be statistically significantly related to survival to discharge. For every 0.1 mmol/l increase in serum iCa, the odds of survival increased by 2.19 (95% CI 1.48–3.49; P <0.001). Serum iCa was also found to be statistically significantly related to complication rates. With every 0.1 mmol/l decrease in iCa, the odds of complications increased by 1.30 (95% CI 1.03–1.69; P = 0.032). Serum iCa was also statistically significantly related to rUO. For every 0.1 mmol/l decrease in iCa, the odds of short-term rUO increased by 1.52 (95% CI 1.14–2.05; P = 0.004).

Data for antispasmodic medication use were available for 187/200 cases. Four cats were given phenoxybenzamine and were not included in statistical analysis, based on the low number. Of the remaining 183 cases, 142 (78%) had received prazosin, 10 (5%) received amitriptyline, six (3%) received both prazosin and amitriptyline, and 22 (12%) received no antispasmodic medication. There was no statistically significant difference between any of the medications mentioned and complications (P = 0.7), short-term rUO (P = 1.0) or survival (P = 1.0).

Discussion

Feline urinary obstructions are common emergency presentations, with complications including a high rate of rUO, which may require surgical interventions or euthanasia. The goal of this study was to investigate the association of rUO and complications in cats undergoing inhalant anesthesia or sedation for urinary catheterization. Inhalant anesthesia, as compared with sedation, did not result in significant differences in either complication rates or rUO. The secondary goals of this study were to evaluate the effect of presenting serum biochemical abnormalities and antispasmodic medications on the incidence of complications and rUO. The present study found that all serum biochemical concentrations investigated had a statistically significant association with survival. Decreased serum iCa was found to be significantly associated with both a higher complication rate and rUO. Increased serum potassium concentrations were found to be significantly associated with the risk of rUO. A higher admission pH and lower admission BUN and creatinine were positively associated with survival. Similarly, higher admission potassium and lower serum iCa were negatively associated with survival. These associations likely indicate that worsening biochemical concentrations are a result of more severe disease and therefore associated with decreased survival.

BUN, pH, iCa and potassium were also found to be significantly associated with re-obstruction. Previous studies failed to find a statistically significant association between serum creatinine, BUN or potassium blood concentrations and recurrence.^2,4 The present finding of the statistically significant relationship between serum biochemical concentrations and short-term rUO could be attributed to more severe metabolic derangements being secondary to prolonged obstruction and, as a result, this may be associated with more severe urothelial injury, which may promote inflammation and urethral spasms, and increase the risk of rUO.

Hyperkalemia is common in UO due to physiological exchanges of potassium and hydrogen at the cellular level, decreased glomerular filtration rate and reabsorption of potassium in the bladder.^1,15 Hyperkalemia in UO has previously been associated with a poor prognosis, although this finding was not statistically significant and no association with rUO was appreciated.^3,4 In the present study, potassium concentrations were found to be statistically significantly associated with the risk of short-term rUO (P = 0.0345). Previous studies in people have found that potassium infusion into the urinary bladder is associated with pain and decreased bladder capacity.¹⁶ Urinary potassium levels are, in part, determined by serum potassium levels and have been shown to be elevated in systemic hyperkalemia.^17,18 Therefore, hyperkalemia may contribute to short-term rUO by increasing pain and decreased bladder capacity, as found in the human literature.¹⁶

Ionized hypocalcemia is commonly reported in critically ill cats, with an incidence of 59–93%, and more specifically in UO, with an incidence of 68–75%.^19,20 The pathophysiology of hypocalcemia in UO is suspected to be due to increased calcium binding with phosphorus secondary to decreased glomerular filtration.^15,19 Hypocalcemia has previously been associated with reduced survival, in both UO and critical illness, in dogs, cats and people, due to its essential role in vasomotor tone, cardiovascular and neuromuscular function.^4,15,19–23 In this study, iCa was significantly associated with complications, survival and short-term rUO.

Antispasmodic medications are commonly used in the management of UO. Prazosin – an alpha-adrenergic receptor antagonist – promotes smooth muscle relaxation but has failed to consistently demonstrate a significant reduction in rUO.^5,24 The tricyclic antidepressant amitriptyline has also been evaluated as an antispasmodic drug candidate and has demonstrated efficacy in a small group of cats with calculi urethral obstruction.²⁵ The current study supports previous research that showed no significantly decreased risk of short-term rUO with the use of antispasmodic medications.

The limitations of this study involve its retrospective nature, including the lack of a control group, a discrepancy in group sizes, the lack of blinding, and the lack of standardization in sedation protocols and overall case management. Additionally, owing to the retrospective nature of the study, a power analysis was not performed. Furthermore, not all data points of interest were available for review, and medical records were lacking information of importance.

Conclusions

This study found no significant difference between inhalant anesthesia and sedation on the incidence of rUO or complication rates in cats undergoing urethral catheterization for UO. The choice of inhalant anesthesia or sedation was often based on clinician preference, comfort in performing the procedure and patient stability. Factors associated with the incidence of complications and short-term rUO, including hyperkalemia and ionized hypocalcemia on presentation, may help with the initial client discussion and expectations regarding disease course and management.

Future directions include a prospective evaluation of standardized sedation protocols and rUO, and if correction of biochemical derangements, such as hypocalcemia, influences survival or recurrence.

Footnotes

Accepted: 12 December 2022

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Ethical approval

The work described in this manuscript involved the use of non-experimental (owned or unowned) animals. Established internationally recognised high standards (‘best practice’) of veterinary clinical care for the individual patient were always followed and/or this work involved the use of cadavers. Ethical approval from a committee was therefore not specifically required for publication in JFMS. Although not required, where ethical approval was still obtained, it is stated in the manuscript.

Informed consent

Informed consent (verbal or written) was obtained from the owner or legal custodian of all animal(s) described in this work (experimental or non-experimental animals, including cadavers) for all procedure(s) undertaken (prospective or retrospective studies). No animals or people are identifiable within this publication, and therefore additional informed consent for publication was not required.

ORCID iD

Rebecca Walton

References

Osborne

Kruger

Lulich

, et al. Medical management of feline urethral obstruction. Vet Clin North Am Small Anim Pract 1996; 26: 483–498.

Seitz

Burkitt-Creedon

Drobatz

. Evaluation for association between indwelling urethral catheter placement and risk of recurrent urethral obstruction in cats. J Am Vet Med Assoc 2018; 252: 1509–1520.

Eisenberg

Waldrop

Allen

, et al. Evaluation of risk factors associated with recurrent obstruction in cats treated medically for urethral obstruction. J Am Vet Med Assoc 2013; 243: 1140–1146.

Segev

Livne

Ranen

, et al. Urethral obstruction in cats: predisposing factors, clinical, clinicopathological characteristics and prognosis. J Feline Med Surg 2011; 13: 101–108.

Reineke

Thomas

Syring

, et al. The effect of prazosin on outcome in feline urethral obstruction. J Vet Emerg Crit Care 2017; 27: 387–396.

Zezza

Reusch

Gerber

. Intravesical application of lidocaine and sodium bicarbonate in the treatment of obstructive idiopathic lower urinary tract disease in cats. J Vet Intern Med 2012; 26: 526–531.

Gerber

Eichenberger

Reusch

. Guarded long-term prognosis in male cats with urethral obstruction. J Feline Med Surg 2008; 10: 16–23.

Cooper

. Controversies in the management of feline urethral obstruction. J Vet Emerg Crit Care 2015; 25: 130–137.

Straeter-Knowlen

Marks

Rishniw

, et al. Urethral pressure response to smooth and skeletal muscle relaxants in anesthetized, adult male cats with naturally acquired urethral obstruction. Am J Vet Res 1995; 56: 919–923.

10.

Cohen

Kass

Pypendop

, et al. Evaluation of urodynamic procedures in female cats anesthetized with low and high doses of isoflurane and propofol. Am J Vet Res 2009; 70: 290–296.

11.

Kim

. Effects of level of consciousness on urodynamic procedure in female cats. J Korean Med Sci 2011; 26: 803–806.

12.

Pratt

Balakrishnan

McGowan

, et al. A prospective randomized, double-blinded clinical study evaluating the efficacy and safety of bupivacaine versus morphine-bupivacaine in caudal epidurals in cats with urethral obstruction. J Vet Emerg Crit Care 2020; 30: 170–178.

13.

O’Hearn

Wright

. Coccygeal epidural with local anesthetic for catheterization and pain management in the treatment of feline urethral obstruction. J Vet Emerg Crit Care 2011; 21: 50–52.

14.

Freitas

da Cunha

Gomes

, et al. Acid-base and biochemical stabilization and quality of recovery in male cats with urethral obstruction and anesthetized with propofol or a combination of ketamine and diazepam. Can J Vet Res 2012; 76: 201–208.

15.

Lee

Drobatz

. Characterization of the clinical characteristics, electrolytes, acid base, and renal parameters in male cats with urethral obstruction. J Vet Emerg Crit Care 2003; 13: 227–233.

16.

Parsons

. The role of a leaky epithelium and potassium in the generation of bladder symptoms in interstitial cystitis/overactive bladder, urethral syndrome, prostatitis and gynaecological chronic pelvic pain. BJU Int 2011; 107: 370–375.

17.

Xavier Júnior

FAF

Morais

GB de

Pereira

TH de S

, et al. Fractional electrolyte excretion and osmolality in the early diagnosis of acute kidney injury in cats with urethral obstruction. Conjecturas 2021; 21: 45–55.

18.

Villeneuve

P-M

Bagshaw

. Assessment of urine biochemistry. In: Ronco

Bellamo

Kellum

Ricci

(eds). Critical care nephrology. Philapdelphia, PA: Elsevier, 2019, pp 323–328.

19.

Coady

Fletcher

Goggs

. Severity of ionized hypercalcemia and hypocalcemia is associated with etiology in dogs and cats. Front Vet Sci 2019; 6. DOI: 10.3389/fvets.2019.00276.

20.

Drobatz

Hughes

. Concentration of ionized calcium in plasma from cats with urethral obstruction. J Am Vet Med Assoc 1997; 211: 1392–1395.

21.

Egi

Kim

Nichol

, et al. Ionized calcium concentration and outcome in critical illness. Crit Care Med 2011; 39: 314–321.

22.

Steele

Kolamunnage-Dona

Downey

, et al. Assessment and clinical course of hypocalcemia in critical illness. Crit Care 2013; 17: R106. DOI: 10.1186/cc12756.

23.

Costello

Drobatz

Aronson

, et al. Underlying cause, pathophysiologic abnormalities, and response to treatment in cats with septic peritonitis: 51 cases (1990–2001). J Am Vet Med Assoc 2004; 225: 897–902.

24.

Hanson

Rudloff

Yuan

, et al. Effect of prazosin on feline recurrent urethral obstruction. J Feline Med Surg 2021; 23: 1176–1182.

25.

Achar

RAN

Paiva

, et al. Amitriptyline eliminates calculi through urinary tract smooth muscle relaxation. Kidney Int 2003; 64: 1356–1364.

Retrospective evaluation of the effect of inhalant anesthesia on complications and recurrence rates in feline urethral obstruction

Abstract

Objectives

Methods

Results

Conclusions and relevance

Keywords

Introduction

Materials and methods

Case selection

Data collection

Statistical analysis

Results

Discussion

Conclusions

Footnotes

Conflict of interest

Funding

Ethical approval

Informed consent

ORCID iD

References