The Case

A 55-year-old man with chronic obstructive pulmonary disease (COPD) was brought by ambulance to the emergency department (ED) with worsening shortness of breath for the past two days. He was febrile to 101^o F, tachycardic to the 140s, tachypneic to the 30s, and hypotensive with blood pressure readings of 60s/40s. He was ill-appearing with coarse breath sounds throughout, mild end-expiratory wheezes at both lung bases, mild abdominal tenderness without guarding, no edema, and no rashes. His oxygen saturation and blood counts were normal, but lactate and procalcitonin levels were elevated, serum creatinine was 1.5 mg/dL (consistent with acute kidney injury), and chest x-ray showed bilateral infiltrates. Computed tomography (CT) of the chest was negative for pulmonary embolism but suggested infection. The patient was given was given an isotonic fluid bolus of 30 ml/kg and started on broad-spectrum antibiotics (cefepime, vancomycin, azithromycin), nebulized bronchodilators, supplemental oxygen by mask, and a norepinephrine drip. An arterial line was inserted into the left radial artery to enable close monitoring of the patient’s hemodynamic parameters. The assigned nurse left the bedside momentarily to attend to other orders. After successful placement, no arterial line set-up was immediately available, so the physician connected the vancomycin drip that was set up for infusion into the patient’s left ankle peripheral intravenous (IV) line to the left arm arterial catheter.

The Vancomycin drip was infusing through a pump and clinical alarms indicating excessive pressure did not go off. Fifteen minutes later, the patient’s nurse identified the misconnection, returned the vancomycin drip to the peripheral IV line, assessed the patient’s left hand, and noted a large hematoma and bruising. The patient’s blood pressure showed improvement with low dose norepinephrine, so another arterial line was deemed unnecessary. The patient started to complain of severe burning and his medial three fingers turned blue, mottled and cold. Doppler studies confirmed lack of flow in the radial artery. An intra-arterial thrombolytic agent (urokinase) was administered by another physician, followed by a heparin infusion for the next six hours via the catheter sheath. Angiography six hours after event revealed restoration of flow in the radial artery and improved perfusion to the extremity.

The Commentary

by Christian Bohringer, MBBS and Griffin Lee, MD

This case represents a known, but fortunately rare, complication of arterial line management. A hypotensive patient in septic shock, presumably due to bacterial pneumonia superimposed on COPD, had an arterial line appropriately placed in the radial artery for hemodynamic monitoring, but this line was inadvertently used to infuse an antibiotic. The patient experienced acute arterial thrombosis with resulting hand ischemia but responded to rapid thrombolytic and anticoagulant therapy.

Background

Unintentional misconnection of an intravenous, arterial, epidural, nasogastric, urinary or other indwelling catheter remains an ongoing risk to patient safety.¹ Misconnecting epidural infusion tubing or oxygen tubing to an intravenous catheter may have deadly consequences.² Inadvertent intraarterial injection of drugs meant for intravenous administration produces thrombotic complications and may require amputation in as many as 30% percent of cases.³ These misconnections are particularly common in critical care units because patients have multiple catheters in place in different sites, and numerous infusions are administered simultaneously. Intensive care unit staff frequently must provide care for several patients at the same time, which leads to sensory and information overload that increases susceptibility to errors. A low nurse to patient ratio has been shown to be associated with medication errors and increased mortality, in certain settings.⁴

Unintended intraarterial injection most commonly occurs when an intravenous drug user cannot aspirate blood from a patent vein because most veins are thrombosed from previous injections. When the user finally aspirates blood with the syringe, (s)he assumes that the tip of the needle is in a vein rather than in an artery.⁵ Erroneous and unintentional direct injection into an artery by a nurse or a physician is fortunately far less common than this non-medical scenario, but it can occur in several ways. An artery may be mistakenly cannulated instead of a vein, or as in this case, intravenous infusion tubing may be misconnected to an arterial catheter. Failing to label an arterial catheter correctly may contribute to this misconnection error. Unintentional cannulation of a radial or a femoral artery may occur in a patient with low blood pressure in the emergency department or in the critical care unit. In this situation, backflow from the catheter is very sluggish and fluids infuse into the artery. When staff erroneously believe the catheter to be in a vein, they may inject medications directly into it.

The radial artery, in particular, follows a variable course in different patients. It runs along the lateral aspect of the forearm in about 1% of the population.⁶   This makes the radial artery especially prone to be cannulated unintentionally and to be mistaken for a vein when the patient is hypotensive.^7,8,9

Arterial injection of drugs can cause ischemia by direct vessel injury, toxicity of the drug, thrombosis or a combination of these factors. Some drugs are very irritating to the endothelium and cause thrombosis and necrosis, while others are much less likely to cause permanent damage. Sodium thiopental, diazepam, diclofenac and antibiotics frequently induce limb-threatening ischemia when administered inadvertently into an artery.^10-14 While propofol and midazolam are also associated with pain on arterial injection, they are much less likely to cause thrombosis leading to amputation.^15,16,17 The lower incidence of limb ischemia in case of accidental intraarterial injection of propofol is one of the reasons why it has replaced sodium thiopental as the most commonly used drug for inducing general anesthesia intravenously.^18,19

Ischemic complications from arterial catheters can be prevented by choosing arteries with good collateral blood supply for cannulation. The hand and foot have excellent collateral blood flow and the radial and dorsalis pedis arteries therefore are the most commonly cannulated arteries for invasive arterial blood pressure monitoring.²⁰ The Allen test, in which both radial and ulnar arteries are occluded by manual pressure, and the operator checks hand perfusion on release of the ulnar artery, is no longer deemed useful because of its poor predictive value.²¹ Duplex ultrasonography and the plethysmograph trace of the pulse oximeter after radial artery occlusion have been advocated as better tests for determining the adequacy of collateral blood flow.²² This assessment is especially important prior to harvesting the radial artery as a conduit for coronary artery bypass grafting.

When a radial artery catheter has been in situ for a few days, the radial artery frequently exhibits partial or complete thrombosis on ultrasound after removal of the catheter.²³ Yet hand ischemia is very rare in this situation because the ulnar artery provides the dominant arterial supply to the hand. As a result of excellent collateral blood supply in the hand and foot, radial and dorsalis pedis arterial catheters are unlikely to cause thrombosis and necrosis in adults unless drugs such as antibiotics or sodium pentothal, or air, are injected directly into the catheter.

If cyanosis of the hand and fingers is detected following an inadvertent arterial injection, a vascular surgeon should be urgently consulted for advice regarding administration of intraarterial papaverine or prostaglandins, systemic anticoagulation, or catheter-directed thrombolysis. Some authors recommend maintaining the arterial catheter in place in this situation to facilitate administering these rescue medications into the artery. When systemic anticoagulation has failed, catheter-directed thrombolytic infusion has been found to be effective.²⁴ An anesthesiologist should also be consulted to perform a stellate ganglion block to improve the blood flow to the upper limb.³ When there is no clear history of inadvertent arterial injection, the catheter should be removed because it could be the cause of the ischemia.

Approaches to Improving Patient Safety:

Avoid injecting drugs and air bubbles into arterial lines

All staff who administer medications must be aware of the potential for serious thrombotic complications if drugs or air are injected directly into an artery. While a small air bubble is not a serious problem in an intravenous line unless there is a right to left intracardiac shunt, it may cause significant morbidity in an arterial line.

Adequately supervise junior staff

It is likely that the physician involved in this case had very little experience in managing critically ill patients. Inserting an arterial line without having a transducer and flushing system at the bedside was a rookie mistake. Unlike intravenous tubing, the tubing required for arterial lines is stiff and non-compliant to prevent measurement artifacts from wave summation.²⁵ An experienced physician would have easily recognized the intravenous tubing as inappropriate. Adequate supervision by a more experienced staff member would undoubtedly have prevented this event.

Prepare adequately before performing a procedure

The physician in this case inserted an arterial line without arterial line tubing, a transducer, and a flush bag ready at the bedside. This lack of adequate preparation directly contributed to the misconnection error.

Trace back the line from the catheter to the infusion pump

Whenever a line is connected to an indwelling catheter it should always be traced back to the infusion pump and to the fluid bag. This is an essential safety precaution that should become a routine habit to prevent misconnections and erroneous drug administration.²⁶

Use color coding to distinguish different lines

Epidural tubing now frequently is marked with a yellow stripe to help prevent accidental misconnection to an intravenous catheter. This color coding was put in place because unintended IV infusion of local anesthetic drugs intended for epidural infusion can be fatal for the patient. Some arterial line tubing and transducers are color-coded red to facilitate identification. Color-coding of different infusion lines can help to prevent unintended cross-connections²⁷ if the catheter is labeled with the same color as the infusion line.

Use different Luer locks for different infusion systems

The universally compatible Luer lock system has been identified as an unintended source of misconnection errors.²⁸ Different Luer lock connections have therefore been advocated for different infusion delivery systems as a means of preventing misconnection of venous, arterial, epidural and enteric feeding infusions. Wrong route medication errors from misconnection could be effectively eliminated if Luer lock connectors for different delivery systems were made incompatible with one another.²⁹

Clearly identify the location of the intravascular catheter

It is plausible that a physician might not realize that they had cannulated the radial artery instead of a forearm vein when a patient is hypotensive, and flow through the catheter is not clearly pulsatile. In this case, the operator was attempting to cannulate the radial artery and apparently believed that they had done so. However, the high-pressure alarm on the infusion pump did not go off, presumably because of low arterial blood pressure.  When the blood pressure is normal, it is difficult to infuse fluids into an artery because the high-pressure alarm on the infusion pump is triggered or blood backs up into the line because the arterial pressure exceeds the force of gravity.  

Correct hypotension prior to inserting an arterial or central venous catheter

In some cases, it is appropriate to correct hypotension with intraosseous fluid infusion or vasoactive drugs before inserting a vascular catheter, particularly in a vessel that may be technically difficult to cannulate. Ultrasound can be helpful to prevent inadvertent arterial cannulation during central venous catheter insertion (including central catheters that are inserted into artery-adjacent peripheral veins such as the brachial vein), especially when blood pressure remains low despite vasopressor therapy. Two-dimensional ultrasound shows the thick wall of an artery and Doppler ultrasound identifies pulsatile flow in the artery. If the patient’s blood pressure in this case had been corrected before line insertion, the high-pressure alarm on the infusion pump would have alerted the staff to the arterial location of the catheter and the misconnection.

Display arterial and central venous pressures on the monitor

Displaying the pressure measured at the tip of the catheter on the monitor will help identify if the catheter is in an artery or a vein. The stopcock on a three way tap in the line can be turned while looking at the pressure trace on the monitor to confirm that the line is truly venous rather than arterial, before any injection. When the patient remains very hypotensive and pressure measurements cannot distinguish whether the catheter is in an artery or a vein, it may be helpful to analyze the partial pressure of oxygen on a blood gas sample obtained from the catheter. The oxygen saturation on the pulse oximeter can then be compared with that on the blood gas sample to determine if the catheter is in an artery or in a vein.

Clearly label arterial catheters

An arterial catheter should always be clearly labelled. This is especially important when cannulating the brachial or femoral artery because these locations are frequently used for both arterial and venous catheters. When the radial artery has an unusual course, and the catheter is thus in an uncommon location, the catheter also needs to be labelled unambiguously as arterial. This information should be clearly communicated to the bedside nurse as well.

Ensure communication between staff inserting the catheter and staff administering medications

There needs to be a clear line of communication between the staff inserting the catheters and the staff who administer medications through them. Infusion systems in the intensive care unit are often complex and an explanation of how the lines are connected is an important part of the handover process when transferring patient care from one staff member to another.

Cannulate arteries with good collateral blood supply

The radial and dorsalis pedis arteries are most commonly used for arterial blood pressure monitoring in adults. These sites limit the risk of ischemia due to collateral arterial circulation. When cyanosis and poor perfusion are noticed, and there is no history of unintended arterial injection, the catheter should be removed. In this case, an unintended vancomycin injection was the cause of arterial thrombosis, but the arterial catheter was kept in situ to facilitate infusion of urokinase and heparin, followed by a repeat angiogram.

Continuously monitor skin color and perfusion of the limb distal to the arterial line

This patient complained of severe burning pain in his fingers. His digits were cold, mottled and blue. Regular visual monitoring of a limb with an arterial line is especially important in sedated patients who may not be able to alert staff to their symptoms. The perfusion of the catheterized limb should be compared to that of another, non-catheterized extremity to determine if the problem is due to the arterial catheter or to a shock state with impaired perfusion to all four extremities.

Consult early and emergently with specialists

A vascular surgeon and a radiologist should be consulted emergently when there is a suspicion of acute arterial thrombosis, for limb-saving treatments such as intraarterial thrombolysis, papaverine, systemic heparinization and thrombectomy.  Early treatment prevented necrosis and the need for amputation in this case. An anesthesiologist is also frequently consulted to place a stellate ganglion block. This injection of local anesthetic in the neck blocks the sympathetic nerve fibers, dilates the blood vessels and improves perfusion of the upper limb.

Take Home Points

• Unintended arterial injections frequently cause necrosis and may require amputation.
• Inexperienced staff need adequate supervision especially in high-stake environments such as the critical care unit, the emergency department and the operating room.
• Color coding should be implemented to reduce misconnection errors between different infusion systems, but different Luer-lock connections may provide a better solution in the future.
• Ultrasound can be helpful to prevent inadvertent arterial cannulation during central venous catheter insertion, especially when blood pressure remains low despite vasopressor therapy.
• Arterial lines need to be labelled clearly.
• Arterial and central line pressure traces should be displayed on the monitor.
• Limbs with arterial lines should be carefully monitored for signs of ischemia.
• Urgent consultation with a vascular surgeon, a radiologist and an anesthesiologist may help to avert necrosis when ischemia is suspected.

Christian Bohringer, MBBS
Professor of Clinical Anesthesiology
Department of Anesthesiology and Pain Medicine
UC Davis Health
chbohringer@ucdavis.edu

Griffin Lee, MD
Anesthesiology Resident
Department of Anesthesiology and Pain Medicine
UC Davis Health
grilee@ucdavis.edu

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