Abstract
Objectives
The aim of this study was to investigate the incidence of complications associated with arterial catheterization in cats in a veterinary hospital, and to document which factors may increase the incidence of complications.
Methods
Medical records at a referral veterinary hospital were retrospectively reviewed to identify cats that had an arterial catheter placed between January 2010 and October 2014.
Results
Thirty-five cats having 38 arterial catheters were included in the study. There was a relatively high incidence of minor complications (23.7%), with the most common being catheter occlusion. The incidence of major arterial catheter complications was low (2.63%). Duration of catheter use was positively correlated to the incidence of complications. There was also a significant correlation between catheters used for intensive care unit monitoring and incidence of complications. All cats with catheter complications survived to discharge.
Conclusions and relevance
The low incidence of major arterial catheter complications in this population of cats illustrates that arterial catheterization is a safe monitoring and diagnostic tool. The duration of catheter placement is significantly associated with the incidence of catheter complications.
Introduction
Peripheral arterial catheterization allows for continuous hemodynamic monitoring of anesthetized and critically ill patients. The placement of arterial catheters provides access for direct arterial blood pressure monitoring, arterial blood sampling and arterial blood gas analysis. In human and veterinary patients direct arterial blood pressure monitoring is considered the gold standard for measuring blood pressure.1,2 Arterial catheters can be placed in the dorsal pedal, coccygeal, femoral, auricular, radial and brachial arteries with the dorsal pedal artery being the most common site of arterial catheterization. 3
In human patients arterial catheterization is associated with complications, including catheter occlusion, infection, removal by patient, hemorrhage, arterial thrombosis, pseudoaneurysm, hematoma formation at the puncture site, catheter-related bloodstream infection, ischemic damage and distal limb necrosis.4–6 Few studies have investigated complications associated with arterial catheters in veterinary patients. Reported complications include destructive lesions of the proximal sesamoid bones secondary to arterial catheterization in three horses, ischemic distal limb necrosis with arterial thrombosis and Klebsiella pneumoniae infection in a cat, and loss of a palpable peripheral pulse in dogs and cats.7–9
In human medicine there is growing recognition of the risks associated with indwelling arterial catheter placement. In the neonatal intensive care unit (NICU) arterial catheters are placed in the radial or ulnar arteries for monitoring purposes. The femoral artery is utilized for cardiac catheterization, while the carotid artery is catheterized for extracorporeal membrane oxygenation. 10 A retrospective study found an overall incidence of arterial thromboembolic events of 1.2% in critically ill children, with most being associated with arterial catheter placement. 11 The most common complications associated with arterial catheters in the NICU are vascular spasm and thromboembolism. 10 In a 2005 prospective study by Brotschi et al, 12 there was an overall incidence of 2.3% for indwelling arterial catheter-related thromboembolic events, with an increased incidence of thrombosis in femoral artery catheterization. In one study minor complications such as catheter malfunction and catheter site infection were noted in <8% of cases, and complications warranting catheter removal only occurred in children <1 year of age. 13 A 2014 meta-analysis reported a pooled incidence of arterial catheter-related blood stream infections as 3.4/1000 catheters (0.34%), and 10/356 catheters (2.8%) in the neonatal population. 6 In general, major complications associated with arterial catheterization in adults occur in <1% of cases.4,11
There are few studies investigating the use of arterial catheters in cats.8,9 To our knowledge there are no studies identifying complications associated with the short-term and long-term use of arterial catheters in cats. The purpose of this study was to retrospectively investigate the incidence of complications associated with arterial catheterization in cats in a veterinary hospital and to document which factors may increase the incidence of complications. Our hypothesis was that there is a low incidence of major arterial catheter complications and that it is a safe procedure to perform in cats.
Materials and methods
The hospital’s medical software was searched using the term ‘arterial catheter’, to retrospectively identify cats that had an arterial catheter placed between January 2010 and October 2014. The medical records of all cats that had an indwelling arterial catheter placed were retrospectively reviewed. Cats were excluded from the study if a complete medical record was not available for review.
From the medical record the following information was recorded: signalment, reason for hospitalization (surgical vs medical), arterial catheter size, arterial catheter location, duration of catheter use, purpose for catheter placement (anesthesia monitoring vs intensive care unit [ICU] monitoring), catheter flushing method, catheter complications (major and minor) and survival to discharge. For the purpose of this study minor complications were considered those associated with arterial catheter dysfunction, including catheter occlusion (inability to flush the catheter or inability to sample arterial blood from the catheter), hematoma formation, bleeding at the puncture site and loss of a palpable peripheral pulse. Major complications were defined as serious systemic issues secondary to the arterial catheter including permanent ischemic damage and catheter site infection.
Statistical analysis was performed using open-sourced statistical software (R software; www.R-project.org/). Data were evaluated for normality using the Shapiro–Wilk test. Non-parametric correlations were performed for duration of catheter use vs survival and duration of catheter use vs complications. Further correlations were examined between purpose for catheter placement vs survival, and purpose for catheter placement vs complications. Results were considered to be statistically significant at P <0.05. Data were assessed for normality using the Shapiro-Wilk test. Data were found to be non-normally distributed (P <0.05). As such, non-parametric methods were employed. Spearman’s rank correlation rho was used to evaluate significant relationships between variables. Fisher’s exact test was used to compare incidence of complication between anesthesia patients vs ICU patients, the incidence of complication and reason for placement (anesthesia monitoring vs ICU monitoring), and incidence of complication and reason for hospitalization.
Results
The database search recovered a total of 50 cats with arterial catheterization. Fifteen cats were excluded from the study owing to incomplete or missing information from the medical record, leaving 35 cats included in the study. The median age of the cats was 10 years (range 8 months–16 years). There were 11 spayed females, 23 neutered males and one intact male cat in the study. The median weight of the cats was 4.34 kg (range 2.36–8.59 kg). A total of 38 arterial catheters were placed, with three cats having two arterial catheters placed during their stay in the hospital. The second arterial catheter was placed for ICU monitoring in those three cats.
Of the 38 arterial catheters, 30 were placed for surgical procedures (78.9%). For catheters placed for surgery, minor complications were noted in 8/30 (26.7%) arterial catheters. No major complications were noted in the catheters placed for a surgical procedure. Eight arterial catheters (n = 8/38; 21.1%) were placed in cats admitted to the hospital for a medical reason. Two (25%) arterial catheters were associated with a complication, with one being a major complication and one being a minor complication. There was no significant correlation between reason for hospitalization (surgical vs medical) and incidence of complications (P >0.05).
A 24 G 3/4 inch catheter (Sureflo; Terumo Medical) was placed in 30/38 (78.9%) cats, 2/38 (5.3%) catheters were 22 G 1 inch (Sureflo; Terumo Medical), 2/38 (5.3%) catheters were 26 G 3/4 inch (Abbocath; Abbott Pearson Medical Supplies) and catheter size was not recorded for 4/38 (10.5%) catheters. The most common site for arterial catheter placement was the coccygeal artery (n = 25/38; 65.8%), with the second most common site being the dorsal pedal artery (n = 9/38; 23.7%). The catheter site was not documented for four arterial catheters (n = 4/38; 10.5%).
The reason for catheter placement (ICU monitoring vs anesthesia monitoring vs dual purpose), duration of catheter use and the number of associated complications are listed in Table 1. A dual-purpose catheter was an arterial catheter that was initially placed for anesthesia monitoring and maintained in the ICU for continued hemodynamic monitoring or arterial blood gas sampling beyond the postoperative recovery period owing to the critical nature of the patient. The duration of time for arterial catheter use was documented for 37/38 catheters with a median length of 3 h (range 1–117 h). Arterial catheters that were associated with a complication were in use for a median length of 8 h (range 2.5–117 h). Those catheters that were not associated with a complication were in use for a median length of 1.5 h (range 1–67 h). Statistical analysis showed a significant correlation between duration of catheter use and complications (P <0.05; Table 2). There was also a significant correlation between purpose for catheter placement (anesthesia monitoring vs ICU monitoring) and incidence of complication with a significantly higher complication rate in catheters placed for ICU monitoring (P <0.05; Table 2).
Number of catheters placed (n = 38), reason for catheter placement, duration of use and number of complications (n = 10)
ICU = intensive care unit
Comparison of survival and arterial catheter complication in 36 cats in relation to duration of catheter use and hospitalization in the intensive care unit (ICU)
Represents a statistically significant correlation (P <0.05)
The majority of catheters (36/38; 94.7%) were flushed by a continuous infusion of 0.9% sodium chloride solution containing heparin sodium 2000 U/l attached to a pressure bag. At our institution arterial catheters maintained by continuous flush method are attached to a pressure transducer (DTXPlus Blood Pressure Transducer; Argon Medical Devices) using non-compliant tubing and the pressure bag is inflated to deliver 1 drop of heparinized saline per min through a 10 drop/ml administration set. One catheter was flushed intermittently using heparin saline flushes; however, the frequency or number of times it was flushed was not documented in the patient’s medical record and one catheter had no flushing method recorded.
There were no reported arterial catheter complications for the majority of the cats in this study (n = 27/35; 77.1%). Minor complications were noted for nine arterial catheters (n = 9/38; 23.7%) of which all were catheter occlusion. One major complication was noted, with one cat suffering ischemic injury secondary to a coccygeal arterial catheter resulting in tail amputation (1/38; 2.6%). Of the 35 cats included in this study, 74.3% (n = 26/35) were discharged home, 20% (n = 7/35) were euthanized, and 5.7% (n = 2/35) died. All of the cats with minor and major catheter complications survived to discharge.
Discussion
The aim of the present study was to investigate the incidence of complications secondary to arterial catheterization in a population of cats in a veterinary referral hospital. Compared with complications associated with arterial catheters in people, there was a relatively high incidence of minor complications (23.7%). The most common complication in this study was catheter occlusion. The minor complication rate in the present study was similar to a recent survey of arterial catheters in anesthetized dogs and cats in which a minor complication – loss of a peripheral pulse – was documented in 22.3% of animals. 9 The results of the current study showed a low incidence of major arterial catheter complications (2.6%). There was a single major complication associated with one arterial catheter in this study with the cat suffering ischemic damage at the coccygeal arterial catheter site resulting in tail amputation. Despite the relatively high incidence of minor complications, there was no correlation between arterial catheter complications and death, as all cats with catheter complications survived to discharge.
Neonates and children were considered a model for cats in this study to try and identify a similar patient population to cats based on their small vessel size. Arterial catheterization in children is considered technically difficult owing to low body weight and small arterial diameter, often requiring multiple puncture attempts.12,14 In a recent veterinary study of arterial catheters, which included 13 cats, no association between catheter complications and number of attempts at placement was identified. 9 The number of attempts at catheter placement could not be evaluated in the present study owing to lack of information regarding puncture attempts in the medical records.
A decreased incidence of vascular thrombosis has been noted in adults when compared with children owing to larger vessel diameter. 12 Smaller arterial diameter has been associated with a greater incidence of vessel occlusion and placement of larger catheters has been associated with increased incidence of occlusive thrombi. 15
A 2016 prospective study of ultrasound-guided femoral arterial access in pediatric cardiac catheterizations found that smaller patient size, number of access attempts, experience of operator, sheath size and length of procedure were not significant predictors of loss of arterial pulse. 16 In this 2016 study a smaller arterial diameter, specifically a femoral artery diameter <3 mm, was the only statistically significant predictor of loss of arterial pulse. 16 Significance of arterial catheter size could not be determined in the present study as most catheters were 24 G. However, based on data in human medicine it stands to reason that cats may have a higher risk of catheter occlusion owing to small arterial diameter.
A case of ischemic distal limb necrosis resulting in mid-femoral amputation was previously described in a cat with arterial catheterization associated with a K pneumoniae infection. 8 Histopathology of the limb revealed necrosis of the dorsal metatarsal skin and subcutaneous tissues, as well as thrombosis of multiple small and large vessels, including an artery in the anatomic location of the dorsal metatarsal artery. 8 In the present study, the cat with ischemic injury to the tail had two arterial catheters placed in the coccygeal artery during its hospital stay. The first catheter was in use for 5 h and the second catheter was in use for 117 h.
In adult patients a higher incidence of occlusion and catheter dysfunction has been reported when the duration of catheterization is greater than 72 h. 15 Similarly, other studies in human medicine note an increase in arterial catheter complications as the duration of catheter placement increased.5,17,18 However, a 2005 retrospective study investigating radial and brachial arterial catheterization in neonates and infants did not find that longer duration of catheterization led to a higher rate of complications, and there was no reported major complications such as ischemic damage or tissue necrosis observed in this cohort. 14 In a 2017 study of arterial catheters in anesthetized dogs and cats no major complications were noted; however, the longest duration of use in a patient was 42.5 h with most catheters being removed ⩽10 h after insertion. 9
In the present study, both catheters that were in place for more than 72 h had complications and one was associated with the major complication of ischemic damage. While the median duration of catheter use in this study was longer for those catheters associated with complications compared with those without complications, the authors were unable to make a detailed recommendation for catheter removal, based on the small number of cases and retrospective nature of this study. In cats with arterial catheters in place, frequent catheter inspection, catheter flushing and palpation of arterial pulses is warranted to minimize the risk of complications.
The significance of arterial catheter location was unable to be determined in the present study as the majority of catheters were placed in the coccygeal artery. In human medicine collateral circulation and vessel diameter were reviewed for various catheterization sites and advantages and disadvantages were documented for each site without one being preferred. 19 In the 2017 study by Trim et al 9 the dorsal pedal artery was most commonly catheterized, followed by the coccygeal artery; however, the location of catheters in cats was not specified so a direct comparison with the present study was unable to be made. Future studies with a larger population are needed to determine whether catheter location is related to the incidence of catheter complications in cats.
A study in children found that the incidence of arterial catheter related infection and associated septicemia was zero. 20 A 2005 study in neonates and infants reported infection rates of 0.5%, 0.7% and 2.3% in patients that were grouped according to their weight, with higher infection rates in patients that weighed more. 14 In the present study there was no reported infection related to arterial catheters. However, no arterial catheters were submitted for culture. It is hospital policy that all catheter sites are inspected daily with catheters being removed and cultured if there is concern for infection and no catheter cultures were submitted for any cat in this study.
In this study, arterial catheter occlusion was the most commonly noted catheter complication. An occlusion or lack of catheter patency could be due to vasospasm or occlusion secondary to thrombosis leading to inability to flush the catheter or inability to draw blood from the catheter. This distinction of why the catheter was occluded was unable to be made in the current study by retrospectively reviewing the medical records. A recent study did not identify a risk factor for arterial occlusion in anesthetized cats and dogs. 9
To better determine the incidence of infection and thrombosis associated with arterial catheterization in feline patients, future prospective arterial catheter studies should include frequent pulse palpation, Doppler ultrasonography to rule out thrombosis, observation of the catheter site for signs of inflammation and infection, and culture of catheters upon removal.
There was a statistically significant correlation between the use of an arterial catheter placed for the purpose of monitoring in the ICU and the incidence of catheter complications. Although illness severity scores were not used in the present study, patients that required arterial catheterization for arterial blood sampling and invasive blood pressure monitoring in the ICU were arguably more critical and had a longer duration of catheter use than those used solely for monitoring during anesthesia. In addition to a longer duration of catheter placement being associated with increased complications, ICU patients that had catheters in place for longer may have also been more mobile during their hospital stay, leading to an increase in catheter complications. Owing to the retrospective nature of this study the degree of movement for each patient was unable to be assessed.
Future prospective studies are needed to determine if there are additional factors associated with catheter complication in ICU patients other than duration of use, as the authors suspect that the cause is likely multifactorial. Factors to be considered include illness severity score, presence of hypotension, use of vasopressors and evidence of hypercoagulability. Arterial catheter removal should be considered in all ICU patients as soon as their catheter is no longer being used for invasive blood pressure monitoring or arterial blood sampling.
The main limitation of this study is its retrospective nature. Future prospective studies are needed to obtain more detailed information regarding arterial catheterization in cats, including aseptic technique for catheter placement, reasons for catheter removal, routine checking for presence of a palpable pulse distal to the catheter site, daily monitoring of the catheter site, culture of catheters to rule out infections as a cause of complications and the role that vasopressors may play in arterial catheter-related complications.
Conclusions
The low incidence of major arterial catheter complications in this population of cats illustrates that arterial catheterization is a safe monitoring and diagnostic tool.
Although there was a relatively high incidence of minor complications characterized by catheter occlusion, this did not lead to any serious sequelae as all cats with arterial catheter complications survived to discharge. In addition, the results of the present study suggest that duration of catheter placement is significantly associated with the incidence of catheter complications. We recommend that arterial catheters be removed as soon as they are no longer needed for arterial blood sampling or invasive blood pressure monitoring.
Footnotes
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.