Acute Superficial and Deep Necrosis of Lower Limb following Femoral Arterial Cannulation in a Neonate Undergoing Arterial Switch Operation for Transposition of Great Arteries

ABSTRACT

Arterial lines are routinely used for hemodynamic monitoring and blood sampling in the operating room and in cardiac surgery intensive care unit. The complications related to arterial line insertion are very low; the knowledge of the relevant artery anatomy, skills and the experience of the operator and selection of a right size cannula plays a vital role in reducing morbidity related to arterial line insertion. We describe extensive superficial and deep necrosis of lower limb following arterial cannula insertion in a preterm neonate undergoing arterial switch procedure and discuss measures to prevent such a complication.

During cardiac surgery, radial or femoral artery is catheterized for arterial blood pressure (ABP) monitoring, sampling for blood gas analysis, and investigations. Neonates have a smaller arterial diameter relative to the catheter and are susceptible to iatrogenic trauma, vasospasm, and thrombosis. In children, the incidence of complications of femoral artery cannulation (ischemia, thrombosis, embolism, and infection) is between 0.1% and 14%.[1] Age and weight are considered risk factors for ischemic complications of arterial cannulation.[2] Neonates and infants are highly susceptible to arterial compromise.[3] Low birth weight neonates are expected to be more susceptible to arterial catheter associated complications. We describe acute deep and superficial necrosis of the right lower limb following right femoral arterial cannulation in a low-birth-weight neonate undergoing arterial switch operation (ASO) and discuss measures to prevent arterial catheter associated complications. Guardian of the patient consented for the publication of this case-report.

CASE REPORT

A 23-days-old low birth weight baby weighing 1.6 kg underwent ASO. Pre-anesthesia check-up was unremarkable. In the operation theatre, ASA monitors were applied and anesthesia induced with ketamine 4 mg and fentanyl 5 mg. Vecuronium 0.5 mg was administered to facilitate tracheal intubation with a 3 mm microcuff endotracheal tube. Lungs were ventilated to a PaCO2 of 45 mmHg with 50% O₂ in air. Anesthesia was maintained with fentanyl 1 μg/kg/h, dexmedetomidine 0.25 μg/kg/h, sevoflurane, and intermittent vecuronium.

Under ultrasonography (USG), a 4F double lumen catheter was placed in the left femoral vein and a 22G cannula (Insyte BD Infusion Therapy Systems Inc. Sandy, Utah, USA) was placed in right femoral artery without difficulty. The transduced ABP showed 60/30 mmHg. Immediately after arterial cannulation, blanching of skin around the cannula was noticed which disappeared over a few minutes. Pulse oximetry of the cannulated limb and ear lobule showed 80%, and normal plethysmograph. A small patch of discoloration reappeared around the catheter while suturing the arterial cannula [Figure 1a]. Heparin, 1 mg, was administered through the arterial cannula and papaverine (1 mg/kg diluted in 15 ml 0.9% normal saline) was infused through the cannula over the next 30 minutes, the discoloration disappeared completely. Meanwhile, right axillary artery was secured under USG. Considering the possibility of bleeding after heparinization from the femoral arterial puncture site during cardiopulmonary bypass (CPB) which may remain unnoticed under the surgical drapes, it was decided to remove the arterial cannula after completion of the surgery.

Figure 1.

(a) Shows the insertion area immediately after suturing. (b) shows discoloration after the surgical procedure

After mid-sternotomy and suitable dissection, heparin, 4 mg/kg, was administered. After achieving an activated clotting time of 550 seconds, aorto-bicaval cannulation initiated CPB and the patient was Cooled to 24°C and ASO was performed. Mean arterial pressure (MAP) during CPB was around 35 mmHg and the duration of CPB was 220 minutes. No vasoconstrictor was used during CPB. After completion of the surgical procedure and rewarming, CPB was weaned with the help of adrenaline 0.04 μg/kg/min, milrinone 0.7 μg/kg/min, and phenoxybenzamine 1 mg/kg/day. The hemodynamics at separation was ABP 55/28 mmHg, heart rate 155/min, and central venous pressure 8 mmHg. Before transferring the patient to intensive care unit (ICU), the arterial cannulation site showed mild discoloration [Figure 1b], immediately, the arterial cannula was removed. The limb showed SpO2 97% without any discoloration or temperature difference, simultaneous SpO2 at ear lobule was 100%. In the ICU, patient remained hemodynamically stable (ABP 50/30 mmHg, heart rate 150 to 160/min). The inotropes and vasodilators were continued.

On postoperative day one, the right foot below the ankle showed discoloration. The pulsations in right femoral and popliteal artery were not felt but flow was elicited on doppler evaluation. Papaverine 1 mg/kg in 0.9% saline was infiltrated around the femoral and the popliteal artery and heparin infusion was started @ 10 units / Kg /h which was later increased to 20 units /Kg /h. Portable doppler over the right lower limb showed reduced flow distal to the right common femoral artery. Vascular surgeon and plastic surgeon opined to manage the patient medically as the femoral artery was too small for any surgical procedure. Heparin infusion and 8^th hourly local papaverine infiltration was continued; additionally, nitro-glycerin patch was applied over the right metatarsal region. The discoloration progressed over the day, the entire limb below the arterial cannulation site became dark [Figure 2]. On postoperative day 2, elective fasciotomy was done due to increasing limb edema. The plastic surgeon expressed necessity of alternate day surgical debridement and vacuum assisted closure (VAC) dressing; therefore, mechanical ventilation was continued. On 8^th postoperative day, the patient underwent extensive wound debridement [Figure 3], the limb was immobilized, and the wound was dressed with Matriderm. A swab sample from the wound grew pseudomonas aeruginosa and escherichia coli for which appropriate antibiotics were started. As immediate wound debridement was not required, the trachea was extubated. One month later, split skin grafting was done with autograft and maternal skin graft [Figure 4]. After 90 days, the child was discharged home with intact limb.

Figure 2.

Shows discoloration in the evening of post-operative day 1

Figure 3.

Shows the affected limb on 8^th postoperative day during debridement

Figure 4.

Shows the limb after skin grafting

In a similar incidence about a month later, a patient undergoing redo intracardiac repair developed limb discoloration following femoral arterial cannulation, the arterial cannula was removed immediately after administering heparin and papaverine and the surgery was postponed. A doppler study showed small caliber of the artery. One week later, the patient underwent intracardiac repair using axillary artery for monitoring; there was no arterial line-related complication.

DISCUSSION

Femoral artery is relatively easy to cannulate and secure and have low incidence of complications.[4] Femoral artery pressure reflects true aortic pressure while coming off CPB, particularly, in neonates and infants where peripheral artery (radial artery) is very small.[5] Tissue ischemia, resulting from embolization and/or vasospasm, is a known complication of arterial cannulation in neonates.[6] Neonates have several risk factors that predispose them to thrombosis and catheter induced ischemia.[7] Vascular spasm is a common complication of arterial cannulation in neonates and is usually temporary and reversible.[8] The size of the arterial catheter in relation to the vessel diameter is a major contributor to arterial spasm.[9,10] Spasm of the femoral artery has been reported when the catheter diameter exceeds >50% of the arterial diameter. In infants and children, the catheter diameter can easily be >50% of the arterial diameter which increases the likelihood of arterial spasm.[11] Frequently, several attempts are required to catheterize the vessel, resulting in intimal damage with subsequent clot formation. It is also worth noting that the femoral artery is a single trunk that perfuses the lower extremity. There are no other major collateral vessels for the arterial supply of the lower extremity. Therefore, complete obstruction of the femoral artery leading to ischemia may have devastating consequences.[12] The mechanical insertion of arterial cannula damages the vascular endothelium, exposing the vessel’s subendothelial tissue and collagen to the circulating blood. Platelets then adhere and aggregate, releasing adenosine diphosphate and thromboxane A2, a platelet stimulator as well as a powerful vasoconstrictor. These occurrences can result in vasospasm around the catheter insertion site, complete occlusion, and tissue ischemia.[13] Additionally, in neonates, during CPB, MAP is maintained around 30-35 mmHg, and following ASO, on the day of surgery, afterload is kept low and a systolic ABP of 50-55 mmHg is aimed. Apparently, relatively large cannula as compared to native artery, vascular spasm following cannulation, single trunk artery without major collateral, low MAP during CPB, vasospasm following cannula removal and low systolic ABP in the postoperative period led to acute limb ischemia, and superficial and deep necrosis. Systemic heparinization and local nitro-glycerin (NTG) ointments have been used to relieve spasm with varied success.[12] Papaverine, an opium alkaloid with vasodilatory and spasmolytic action is used in cardiac patients to relieve arterial spasm, and also to prolong the patency of arterial catheters in neonates.[13] Papaverine, 1 mg/kg, diluted to 1 mg/ml in 0.9% saline is infused over 5-10 minutes.[14] It inhibits the oxidative phosphorylation and calcium flux, during muscle contraction thereby causing vascular dilatation. Reflex vasodilatation using warm compress to the unaffected limb while elevating the affected limb may relieve severe vasospasm within 6-8 hours. Continuous lumbar epidural blockade or caudal blockade can also improve limb circulation. The measures described are useful when the acute limb ischemia is diagnosed after surgery; however, if the ischemia is noted before the start of surgery, immediate removal of the cannula and local measures to counter vasospasm as described may help prevent limb ischemia. Further, it is appropriate to postpone the surgery and cannulate an alternative artery for the perioperative monitoring as was practiced in the second case and offers the safest option. Following this complication, we have started monitoring SpO₂ of the femoral artery cannulated limb; additionally, we monitor the limb for discoloration and temperature variation 4^th hourly.

In view of possibility of devastating complications of femoral arterial cannulation in neonates, the following precautions is suggested—an experienced anesthesiologist should cannulate the artery under USG with a smallest possible arterial cannula; the artery should be punctured below the inguinal ligament but before it branches into superficial and deep femoral artery, and multiple attempts and trans-fixation of the artery puncturing posterior wall should be avoided. If cannulation is unsuccessful, the puncture site should be compressed. The caliber of the artery and that of cannula should be compared and if the caliber size of cannula is >50% of arterial caliber, alternative artery should be considered for cannulation. At present, 22G is the smallest arterial cannula available with us, we explored the availability of 24G arterial cannula but it is not available.

CONCLUSION

Arterial compromise following femoral arterial cannulation can be a devastating experience for the care givers, patient, and the parents. Perhaps, the small caliber of the artery, a disproportionally larger arterial cannula, hypothermia and low MAP during CPB, and strategy to reduce afterload and to facilitate LV function after ASO, precipitated acute lower limb ischemia following arterial cannulation. The cannula should be immediately removed, if ischemic changes are noted before the start of surgery and an alternate site such as axillary artery is used for monitoring.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.