Ultrasound-Guided Evacuation of A Perineural Abscess: Illustrating Anesthesi- ologist’s Skills Beyond Anesthesia Practice

Ultrasonography (US) is nowadays widely used by anesthesiologists while performing locoregional anesthesia. The use of US beyond loco-regional anesthesia is becoming frequent [1,2,3,4]. We describe a case of US guided perineural abscess evacuation performed by an anesthesiologist familiar with loco-regional anesthesia.


Introduction
Nowadays, loco-regional anesthesia guided by ultrasound is a prevalent practice, which is especially used for the placement of perineural catheters with the aim to provide analgesia. Its use beyond perineural catheter placement is not frequently described.
We report a case of US guided perineural abscess evacuation performed by an anesthesiologist, familiar with loco-regional anesthesia. For publication of this report, the patient's written consent was obtained.

Description
A popliteal sciatic perineural catheter had been inserted by the Pain Service under ultrasound guidance in a 54-year-old man (ASA III) suffering from severe foot pain.
The patient's history included a medical history of diabetes mellitus type 2 without insulin, an atrial fibrillation, a pacemaker and an obstructive sleep apnea.
The patient's weight was 66kg and he had a Body Mass Index of 22.
The popliteal catheter was inserted in aseptic conditions. The operator was wearing a hat, mask, sterile gown and sterile gloves. The affected area had been disinfected with chlorhexidine. Sterile fields were set up by the anesthesiologist and ultrasound probe protection was used.
A first bolus of ropivacaine 0.2% was injected and the catheter was connected to a pump with the following program setting: continuous infusion of 5 mL/h, a bolus of 5 mL with a refractory period of 50 minutes.
A daily evaluation of the pain relief due was performed by a team specialized in pain management. The catheter was kept in place during 3 weeks to relieve patient's foot pain. It was then removed due to leakage and local site infection. J Anesth Surg Care 2019 | Vol 1: 103 The patient was scheduled for foot surgery the day after the catheter removal. While performing US in view of performing a popliteal sciatic nerve block, a hypo-echogenic collection was visualized adjacent to the sciatic nerve (figure 1). This collection was not present while performing the first US 3 weeks earlier.
The decision was made to evacuate the collection with a 18-gauge

Discussion
To our knowledge this is the first time a popliteal collection is drained under echographic guidance by an anesthesiologist. In the literature, only few cases of peri nervous abscesses occurring with catheter placement are described, and every each of them were surgically drained [5]. This case illustrates that echography performed by anesthesiologists can be used as a way to detect complications linked to catheter insertion as well as the treatment of these complications.
There is a difference between catheter colonization, inflammation and infection. Bacterial colonization is microbial growth on catheter tip culture. The signs of inflammation at the catheter entry site are erythema, itchiness or warmness. Catheter infection is defined as signs of systemic infection such as fever, leucocytosis, elevated infection-inflammation markers and positive blood culture, in a patient with signs of catheter entry site inflammation or evidence of abcess [6]. A meta-analysis [7] of randomized controlled trials showed that catheter colonization occurred in 6 to 69% of cases with some signs of inflammation in 3 to 9.6% and with signs of infection in 0 to 3%. Neuburger et al. [6] proposed that inflammation could be related to tissue trauma due catheter movement. Three possible explanations are proposed for peripheral nerve block infection : bloodstream diffusion, contamination of infused drugs and pathogen penetration through catheter entry [6]. It seems that the formation of a hematoma close to the insertion site of the catheter is a possible risk factor for the development of an infection. Therefore, some experts recommend to remove the catheter in the case of hematoma adjunctant to the puncture site [6]. In our patient, the inflammation markers were high. However, this can be due to catheter infection or be a consequence of his diabetic foot.
Infectious complications of perineural catheters are rarely reported in the literature, estimated at 2.4%, and only few cases report sepsis [5,6,7,8]. Lethal infection was described in one case [6]. This reveals a high colonization rate but infection remains rare.
A retrospective study [11] dealt with the use of peri- iodine [6]. It has been shown that the use of tunneled catheters would reduce infection emergence [6,8,12]. To reduce the risk of infection, avoiding hyperglycemia in the postoperative period is another important point although no consensus exists on glycemia targets [6]. In our patient, the aseptic guidelines for the placement of the catheter were respected but the catheter was not tunneled.

Conclusions
To our knowledge, this is the first case of localized treatment of an abscess performed by an anesthesiologist expert in ultrasound-guided locoregional anesthesia. This case also illustrates the importance of performing ultrasound in daily anesthesia practice.
To conclude, it seems important to suggest some recommendations of good practice to insert peri-nervous catheter and to take care of potential complications.
It is recommended to apply the basic precautions like wearing a mask, a hat, sterile gloves, a sterile gown but also to disinfect the area with chlorhexidine and to use an ultrasound probe protection.
It is suggested to remove the catheter as soon as possible (ideally maximum 72 hours after insertion Submit your manuscript to a JScholar journal and benefit from: ¶ Convenient online submission ¶ Rigorous peer review ¶ Immediate publication on acceptance ¶ Open access: articles freely available online ¶ High visibility within the field ¶ Better discount for your subsequent articles An echography control could be made to detect a prospective abscess in the area of puncture point. It would also be interesting to consult an infectious disease doctor to get his advice regarding antibiotherapy.
If an abscess is discovered, practicing this less invasive technique could give more advantages than surgical act: it requires no incision and thus no problem of healing, and provides a lower level of fear/stress for the patient. More investigations are required before recommending this practice.