Radial artery pseudo aneurysm after percutaneous cannulation using Seldinger technique

Abstract

Cannulation of a peripheral artery in a patient allows for continuous blood pressure (BP) monitoring and facilitates frequent arterial blood gas (ABG) analysis. Complications include thrombosis, embolism risk, haemorrhage, sepsis, and formation of pseudo aneurysms. A 75-year-old male admitted via casualty with a collapse secondary to seizures. Patient was intubated and mechanically ventilated for 7 days. A right radial artery catheter was inserted on admission to casualty. The arterial catheter remained in situ for 7 days. Five days following its removal, the skin site appeared inflamed and a wound swab grew methicillin resistant Staphylococcus aureus (MRSA). Eight days later a distinct bulging of the radial artery was noticed. An ultrasound was done and it showed radial artery pseudoaneurysm, the diagnosis was confirmed by angiogram. Delayed radial artery pseudoaneurysm formation has only been reported in association with infection, and less than twenty of these cases have been reported in the literature.

INTRODUCTION

Peripheral arterial cannulation allows continuous blood pressure monitoring and arterial blood gas (ABG) analysis in critically ill patients. The reported complications include catheter-related sepsis in 4%, thrombosis in 38%, and peripheral embolisation in 28% of the cases.[1,2] None of these complications are known to carry significant mortality. The radial artery is the preferred site in these cases. Another less frequent complication is development of pseudo aneurysm, which is caused by disruption of the arterial wall at the site of cannulation.[3–5] The most common site for pseudo aneurysm to occur after cannulation is the femoral artery. Radial artery pseudo aneurysms occur more frequently than brachial artery pseudo aneurysms mainly because it is most commonly cannulated. The main risk factors are age, sepsis especially with methicillin resistant Staphylococcus aureus (MRSA). patients on haemodialysis, duration of catheterisations, multiple attempts, hypotensive and coagulopathic patients.[6] We describe a case of radial artery pseudo aneurysm, which occurred after cannulation. This case highlights the risk factors associated with development of pseudo aneurysms in susceptible cases.

CASE REPORT

A 75-year-old male admitted via casualty with a collapse secondary to seizures. The significant factors in his past medical history were, patient on intermittent dialysis for end stage renal disease (ESRD), left lacunar infract in temporal lobe, coronary artery bypass graft (CABG) in 2000, hypertension, chronic obstructive pulmonary disease (COPD) and atrial fibrillation. He was on multiple medications, which includes warfarin. On admission patient was confused, both pupils equal and reactive to light with a glascow coma scale of 12/15. He was tachycardic, hypotensive and tachypnoec. Investigations were positive for raised renal parameters and altered coagulation profile. Electrocardiogram and computed tomography (CT) of brain showed no new changes. On deterioration patient was intubated and mechanically ventilated for 7 days. A right radial artery was cannulated for blood pressure and ABG measurements, which remained in situ for 7 days. Five days following its removal, the skin site appeared inflamed and a wound swab grew MRSA. The inflammation initially appeared to settle; however, 8 days later a distinct bulging of the radial artery was noticed. An ultrasound was performed showing radial artery pseudoaneurysm [Figure 1]. The diagnosis was confirmed by angiogram. The radial artery was compressed as a treatment, but it ruptured after a week leading to surgical intervention. Surgical exploration of the radial artery confirmed the presence of a 6 × 5 cm pseudoaneurysm.

Figure 1.

Ultrasound image of radial artery pseudoaneurysm

DISCUSSION

Infected radial artery pseudoaneurysm is a rare complication of a frequently done procedure. There are not many studies that compare the approach and complication rates of arterial cannulation in a medical intensive care unit. A study done over a 24-month period at Howard Hospital concluded that femoral artery was the most preferred site in MICU and that vascular insufficiency followed by bleeding was the most common vascular complication after line changes using a guide wire. Arterial spasm and loss of pulse were more commonly found after new-site insertion. The site of arterial cannulation placement, timing and number of catheter site changes made no significant difference in terms of complications, which is a new finding compared to other previous reports. The rates of infection between radial and femoral artery were similar.[7] In our ICU the most preferred site for cannulation is radial artery.

There are many risk factors associated with radial artery pseudoaneurysm formation. First the complication is more common in older patients. Falk et al. in a case series in 1992 found the average age of occurrence at 71.6 years with a standard deviation of 13.5 years. Second was the duration of catheterization. The duration was important in two ways. One it was an independent factor for development of pseudoaneurysm and second the longer the duration more the chance of infection, which also increased the incidence of pseudo aneurysms. There are no specific reviews about the time frame for the development of radial artery pseudo aneurysm after cannulations.

Third and probably the most significant risk factor is the presence of S. aureus infection specifically MRSA. It is one of the commonest organisms causing catheter related sepsis. Many case reports have reported the association of such sepsis with pseudo anerusym formation.[8] The exact mechanism how this occurs is not known. We hypothesised that probably the infection might lead to weakening of the vessel wall. A review of the infection rate with duration of catheter placement showed that the cumulative risks of developing a catheter infection increased from 7% to 17% after 6 days of peripheral arterial catheter placement.[9] A recent review by Kalifa et al. in intensive care medicine journal in October 2008 recommends that systematic replacement of peripheral arterial catheters might be useful in preventing catheter-related colonisation, especially after 2 weeks of use.[10] MRSA is now being named as specifically causing pseudo anerusym and that colonisation occurs in around 20% of radial arterial catheters, although S. aureus is only isolated in around 3% of cases.[11]

In our case all of these risk factors were present. The interesting thing was that there were only 3 attempts made for the cannulation. Normally pseudo aneurysm is associated with multiple attempts. The rate of infection was also made higher by the fact that he was on dialysis. There were no external signs of infection at the cannulation site like redness or secretions. This made it much harder to guess that there was a concealed infection. The hospital protocol would be to change the cannula if there were any signs of infection or after 1 week of catheter insertion. Many guidelines have now made it mandatory for the use of ultrasound in central line insertion to minimise complications. Maybe using an ultrasound for arterial cannulation in high-risk patients might reduce the incidence of pseudo anerusyms as the number of attempts for cannulation is reduced significantly. Though all aseptic precautions were taken, there is always an increased risk of infection in patients who are immunocompromised. The investigation of choice in cases of suspected radial artery pseudo aneurysm is ultrasound.[12]

A review of literature of treating extremity pseudo aneurysms suggested that percutaneous injection of bovine thrombin under ultrasound guidance is possible as one of the minimal invasive procedures to treat the pseudo aneurysm.[13] An alternative method is compression by mechanical devices or micro vascular surgeries.

CONCLUSION

A strict vigilance and a protocol for identifying risk factors for pseudoaneurysm formations could possibly avoid these rare events. A high index of suspicion as well as prompt and aggressive surgical treatment of bacterial arteritis with or without pseudo aneurysm formation as an adjunct to intravenous antibiotics is essential to improve the prognosis of this complication. Use of ultrasound to prevent repeated attempts at cannulations should be followed in high-risk cases. A clinical review of complications and risk factors of peripheral arterial catheters used for hemodynamic monitoring in anaesthesia and intensive care medicine concluded that arterial cannulation is a safe procedure.[14]