New Technology Committee

Introduction

The mission of the New Technology Committee is to update, inform, promote dialogue and critically assess novel techniques and technologies in pediatric surgery so that our members can continue to provide the highest standards of care for infants and children. Mechanisms by which this committee shall achieve these tasks will include but not be limited to

  • critical review and evaluation of current and future approaches to pediatric surgical problems by systematic reviews
  • sponsoring surgical innovation and technology sessions within the APSA meetings
  • updating membership on new and evolving techniques within our field.

The production and publication of periodic reviews in the Journal of Pediatric Surgery, when relevant, is another method by which this committee will provide up to date analysis of technologies, devices, and surgical approaches for the entire APSA membership which is unlikely to be aware of the most current knowledge in these areas. Our committee hopes to provide a venue for review of these areas to the members so that our organization may be involved in the development and monitoring of potentially useful new technologies.

New Technology page link on apsapedsurg.org

New Technology Toolkits

Magnets in Esophageal Atresia (Bethany Slater)

The use of magnets is a nonsurgical alternative for esophageal atresia (EA) anastomosis in selected patients. The United States Food and Drug Administration has approved a catheter-based magnetic device, the Flourish® Pediatric Esophageal Atresia Device (Cook Medical, Bloomington, IN), for use in lengthening atretic esophageal ends and creating an anastomosis in patients up to one year of age. It has been federally authorized as a humanitarian use device.

Flourish device
Descriptive text is not available for this image

The device consists of an esophageal and gastric catheter each containing an inner catheter fitted with a bullet shaped neodymium iron boron magnet. The proximal portion has a central opening for insertion of a guide wire as well as a port for suctioning saliva and for injection of contrast to confirm anastomosis. The distal catheter has a channel for enteral feeds and a five ml balloon. The magnets situated in the proximal and distal esophageal pouches have opposite polarity and thus once aligned attract one another which results in lengthening of the ends. Once the magnets connect, or couple, the intervening tissue becomes ischemic and sloughs off while the outer rim heals establishing the anastomosis. The length of the gap must be within the magnetic field achievable by the two magnets to attain attraction and connection.The magnetic anastomosis procedure may be performed under anesthesia or sedation and is done under fluoroscopic guidance. After completion, daily chest radiographs are done to verify proper alignment of the magnets. Successful anastomosis is confirmed by esophagram, saliva in the gastrostomy catheter or feeds in the esophageal catheter. After confirmation, the magnets may be removed and replaced with an oro- or nasogastric tube over a wire.

In addition, there is a magnetic device approved for compassionate use that has also been developed and is undergoing clinical testing. This device has disc shaped magnets in a convex / concave orientation. Once anastomosis is achieved it is spontaneously expelled.

Advantages

The main advantage of using magnets for creation of esophageal continuity in esophageal atresia is to avoid an operation. The use of magnets for esophageal atresia may be particularly beneficial for patients with a pure esophageal atresia without a long gap or patients that have undergone multiple operations or who have other comorbidities that increase the surgical risk.

Indications for use

The distance between the upper and lower pouches must be less than four cm in length to use the Flourish Device and within the specified gap distance of other magnetic devices. Magnets can be used in pure esophageal atresia cases or with a repaired fistula. For the catheter-based magnet device, a gastrostomy with a tract able to accommodate an 18 F catheter must be present. The magnets can be used as a primary procedure for anastomosis, as a staged procedure after surgical esophageal lengthening or for a recalcitrant stricture after tracheoesophageal fistula repair.

Review of evidence

Hendren and Hale first reported the use of electromagnetic bougienage to lengthen the esophageal ends in a patient with EA facilitating later surgical repair [1]. Catheter-based magnetic anastomosis was initially described in five infants with EA in Argentina [2]. Anastomosis was achieved in all of the patients in an average of 4.8 days. A later series was published describing achievement of primary esophageal anastomosis in an additional four patients with EA using catheter-based bullet shaped magnet pairs [3]. A recent study described a two staged approach whereby young infants had an initial esophageal approximation without luminal continuity followed by magnamosis [4]. In addition, a retrospective study was recently published describing the use of the catheter-based magnet device in 13 patients. All achieved anastomosis with a 100% stricture rate and two patients required surgery for a refractory stricture [5]. Woo published a series of two patients that underwent magnetic compression stricturoplasty to treat refractory strictures after esophageal atresia repair [6].

Summary of studies using magnets for esophageal atresia

number of patients

Use of magnet

average days to anastomosis

% stricture

Takamizawa 2007 [7]

1

stricture

34

100

Zaritzky 2009 [2]

5

anastomosis

4.8

80

Zaritzky 2014 [3]

9

anastomosis

4.2

89

Lovvorn 2014 [4]

2

staged anastomosis

7.5

100

Dorman 2016 [8]

1

staged anastomosis

13

100

Woo 2017 [6]

2

stricture

8.5

100

Greenstein 2018 [9]

1

anastomosis

10

100

Slater 2019 [5]

13

anastomosis

6.3

100

Cryoablation (Nicole Wilson and Edmund Yang)

Currently, there are two primary methods used to correct pectus excavatum: the open Ravitch procedure [10] and the minimally invasive Nuss procedure [11]. Traditionally, pain control after pectus excavatum repair has been challenging. In particular, the sudden remodeling of the chest wall inherent in the minimally invasive Nuss procedure is associated with significant postoperative pain. Pain after pectus excavatum repair is caused by several factors including incisional pain, interruption of cartilaginous, muscular and ligamentous structures in the chest wall, alteration of chest wall mechanics due to the presence of a bar and pain of pleural irritation from the bar. Inadequately controlled pain can result in poor pulmonary toilet and result in sputum retention, atelectasis, pneumonia, lack of participation in physical therapy and other postoperative complications. Therefore, it is critical that pain be adequately addressed in the immediate postoperative period.

Historically, analgesia was achieved with opiates administered parenterally and transitioned to enteral administration after the first few postoperative days. More recently, multimodal therapies including thoracic epidural analgesia, patient-controlled parenteral opiate administration (PCA), anti-inflammatories, gabapentinoids and muscle relaxants, have become the gold standard [12]. However, despite development of extensive multimodal analgesic regimens, the mainstay of postoperative pain management remains opioid pain medications. Concerns regarding increased risk of long term opioid use after postoperative opioid therapy [13] and management of the side effects of opioid administration (respiratory depression, itching, nausea, sedation and constipation) continue to drive the search for alternative pain management strategies.

One of the first descriptions of the clinical application of cryotherapy to produce local blocking of peripheral nerves was in 1976 by Lloyd [14]. Cryotherapy techniques have since been applied to the treatment of various neuralgias [15][16] and chronic pain [17]. Cryoablation has been shown to improve respiratory mechanics and decrease opioid use when used for postoperative pain control after thoracotomy [18][19]. Given the success with cryoablation in adult patients after thoracic surgery, there has been recent interest in using cryoablation in pediatric patients undergoing repair of pectus excavatum [12][20][21][22][23].

Physiology

Cryoablation of intercostal nerves can offer both short and long term analgesia. A cryoprobe makes use of the Joule-Thomson, or Joule-Kelvin, effect, which describes the cooling effect that occurs with expansion of a gas that passes from an area of higher pressure to a lower pressure area [24]. The gas, typically carbon dioxide or nitrous oxide, is released at high pressure and allowed to rapidly expand within the bulb of the cryoprobe, resulting in cooling of the probe tip to approximately -50° to -70°C [19].

cryoprobe
Descriptive text is not available for this image
adapted from Smiley [25]

The cryoprobe is applied directly or immediately adjacent to the peripheral nerve of interest and creates a localized freezing which induces axonotmesis in which Wallerian degeneration of the axon and myelin sheath occurs distal, and to a lesser extent proximal, to the lesion [19]. This disrupts axonal continuity between the sensory nerve endings and the central nervous system (CNS). The perineurium and epineurium are relatively resistant to freezing so they remain intact, maintain continuity and provide a scaffold between the sensory nerve endings and the CNS. Recovery and restoration of sensation is accomplished via axonal regeneration through the perineurial canal which takes place at a rate of one to three mm/day.

Moorjani investigated the histologic changes after direct application of a cryoprobe to intercostal nerves for 60 seconds [19]. Immediate histologic changes included axonal degeneration, accumulation of edema fluid, capillary stasis and that the endoneurium remained intact. They also showed that one week after cryoablation axonal swelling gradually resolved. Histologically, there were signs of Schwann cell proliferation and axonal segments had reappeared in some nerve fibers indicating partial recovery of the ablated nerve tissue. This partial recovery was progressive and complete by one month after cryoablation. Furthermore, they demonstrated that longer applications of the cryoprobe caused the same changes but the time taken for complete recovery was proportionally increased. After a standard 90 to 120 second application of a cryoprobe, complete axonal regeneration can be expected by four to six weeks [21].

Steps of the procedure

Since the use of cryoablation in the Nuss procedure is relatively novel, the surgical steps are somewhat variable and surgeon dependent. Many surgeons use the cryoICE cryoprobe (Cryo2 or 3, AtriCure, Inc., Mason, OH) which is a wand-shaped probe that can be placed into the chest under thoracoscopic guidance. It has an insulated shaft allowing minimal exposure of the cryoablation tip. The probe is used with a preprogrammed freeze/thaw cycle for 120 seconds. It cools to -60° C and effective ablation is visualized as ice crystal formation on the chest wall. The probe initially adheres to the tissues but releases from the area of ablation with warming in three to five seconds. The probe is commonly bent at the tip to facilitate longitudinal application along the inferior aspect of the rib.

Cryoablation is performed posterolaterally at the same interspace in which the pectus bar is located - two intercostal spaces above and two below the bar [21][23][26]. This usually ends up being intercostal nerves four through eight although some authors extend ablation to include the ninth intercostal nerve. Care should be taken to count the interspaces, since Horner syndrome and abdominal wall laxity are potential complications from ablating the T1-2 and T11-12 intercostal nerves, respectively. Though initial publications described subcutaneous dissection using the cryoprobe to reach the intercostal nerves [12], recent studies describe intrathoracic use of the probe bilaterally with thoracoscopic guidance. Single-lung ventilation can assist by providing better exposure of the intercostal nerves. Some authors elevate and dissect the mediastinum, then extend the thoracoscope and cryoprobe across the mediastinum to ablate the contralateral nerves [20][21] whereas some insert the thoracoscope and probe into each side for ipsilateral cryoablation [27].

There is only a single study involving the use of cryoablation for analgesia in patients undergoing modified Ravitch procedure [28]. The cryoablation was performed thoracoscopically to the pertinent intercostal spaces. This was done either before or after the Ravitch procedure.

A posterolateral thoracotomy incision may be used to gain access to the thorax for a number of operations. Either upon gaining access to the chest or before closure of the thorax, the intercostal nerves (one at the level of the incision, one cranial and two caudal) are identified and exposed by peeling off the parietal pleura [19]. The cryoprobe is then placed on each nerve to be ablated under direct vision and ablation proceeds according to steps similar to those outlined above. The same equipment used for thoracoscopic cryoablation can be used under direct vision with a thoracotomy incision.

The successful use of cryoablation in adolescent patients undergoing the Nuss procedure begs the question of use in younger pediatric patients during thoracotomy. Unfortunately, there have been no documented studies involving thoracotomy nerve cryoablation for analgesia in this age group. However, cryoablation has been used in younger patients for ablation of tumors [29], vascular malformations [30] and foci of cardiac arrythmias [31].

Review of the evidence for safety and effectiveness

There have been a number of studies investigating the use of intercostal nerve cryoablation in patients undergoing thoracotomy and Nuss procedure . These studies show that use of cryoablation, in conjunction with a multimodal approach to postoperative pain control, results in a decreased length of hospital stay and decreased usage of opioid analgesics both as an inpatient and after discharge.

Cryoablation literature

study

type

number of patients

procedure

length of stay (days)

length of analgesia (days)

Moorjani [19]

randomized prospective

200 (adult)

thoracotomy

not reported

*Opioid: 7

Cryo: 6

Keller [12]

retrospective

52 (pediatric)

Nuss

Epidural: 5.8

Cryo: 3.5

*Epidural: 3.96

Cryo: 3

Sujka [27]

retrospective

28 (NR)

Nuss

Epidural/PCA: 4.0

Cryo: 1.4

†Epidural/PCA: 2.6

Cryo: 1.2

Harbaugh [13]

retrospective

31 (pediatric)

Nuss

Epidural: 6

Cryo: 3

‡Epidural: 1.82 OME/kg

Cryo: 1.78 OME/kg

Graves [21]

randomized prospective

20 (adult & pediatric)

Nuss

Epidural: 5

Cryo: 3

§Epidural: 684 mg

Cryo: 268 mg

Dekonenko [32]

prospective

100 (pediatric)

Nuss

Epidural/PCA: 4

Cryo: 1

†Epidural/PCA: 3.0 Cryo: 0.9

Pilkington [28]

retrospective

29 (pediatric)

Ravitch

Epidural: 6

Cryo: 4

†Epidural: 2

Cryo: 1.5

all had a significant difference between groups; * days to cessation of use of opioid analgesics; † Days to only oral pain medication; ‡ Postoperative inpatient oral morphine equivalents (OME/kg), not significantly different; § Reported as oral morphine equivalents

The studies of cryoablation in pectus excavatum repair reviewed above are limited by their retrospective nature, rapidly evolving pain control protocols and small sample sizes. Despite these limitations the results are promising and suggest improved patient outcomes with cryoablation compared to other pain control modalities. While cryoablation is certainly promising as an additional therapy in our armamentarium, these studies demonstrate that cryoablation alone is not sufficient for postoperative pain control as it can take 24 to 36 hours to become fully effective [21][27]. In addition, its use is not without complications, side effects and associated difficulties.

Complications and side effects

As would be expected, cryoablation increases operative times. A single nerve ablation takes two minutes and typically five nerves are ablated on each side - the minimum length of time for a full cryoablation procedure is 20 minutes. Longer operative times (range: 40 to 60 minutes, mean 30 minutes) have been reported in the most recent literature [12][13][21][27][32]. One study did not demonstrate an increase in operative time for the modified Ravitch procedure when comparing cryoablation to thoracic epidural anesthesia [28]. Potential long term complications following cryoablation include chronic neuropathic pain and persistent chest wall numbness. A recent study which included 43 adult and pediatric patients, demonstrated neuropathic pain in 38.5% of adults (age older than 21 years) but an incidence of 0% in pediatric patients (age younger than 21 years) [33]. In this study, pediatric patients also had faster resolution of chest wall numbness (3.4 months versus 10.8 months) compared to adult patients. In addition, there have been previous reports of neuralgia (e.g. burning, electrical or tingling sensations) after cryoablation with an incidence reported between 20 and 30% in adult series using cryoablation after thoracotomy [34]. The Graves’ study included no reports of neuralgia in the group that underwent cryoablation. All patients had anterior chest wall numbness at initial follow-up and sensation returned to normal in all patients (6/10 at three months, 10/10 with one year) [21].

Cost

The cryoICE Probe (cryoICE Probe for Cryo Nerve Block, CRYO2, AtriCure, Inc., Mason, OH, USA) is the most common probe used for peripheral nerve ablation. The probe itself is a single use piece and is designed to be used with the AtriCure Cryo Module (ACM; cryoICE BOX V6, AtriCure, Inc., Mason, OH, USA) and the AtriCure Cryo1 Accessory Kit (composed of a Nitrous Oxide tank heater, a pressure regulator unit, and a temperature display unit). The ACM and Accessory Kit represent capital investments. Pricing for all components are negotiated at the hospital level. There are video clips on the website demonstrating some uses of the cryoICE Probe and additional information.

Indocyanine Green (ICG) (Brian Gulack, Samir Pandya, Bradley Segura, Gustavo Villalona and Stefan Scholz)

Fluorescence-guided surgery (FGS) is a medical imaging technique used to detect fluorescent labelled structures during surgery. Camera systems that detect near-infrared (NIR) light not visible to the human eye can provide information about anatomy or tissue viability to the surgeon through real time visualization in the operating field.

Indocyanine green (ICG) is the only NIR fluorescent agent currently approved for human use. ICG is a safe, water-soluble compound that received FDA approval in the 1950s. Despite the bright green color of the reagent to the human eye, its use as a contrast agent is based on its robust fluorescence in the NIR range. Applications for ICG in the pediatric world are emerging.

Indocyanine green can be used for arteriogram, venogram or general perfusion assessment of tissues such as intestinal before anastomosis or soft tissue pedicles during plastic surgery. ICG gets exclusively cleared by the liver through the bile ducts and is applied in fluorescence cholangiography. When administered intradermally, ICG becomes protein bound and confined to clearance via the lymphatic system which is used to facilitate sentinel lymph node detection and biopsy.

Scientific basis

ICG is one of the most frequently employed NIR fluorophores used for FGS. ICG is a water-soluble, anionic, amphiphilic tricarbocyanine probe with a molecular weight of 776 Da which rapidly binds to plasma proteins in the body. The excitation peak is 780 nm and the emission peak is at 820 nm which places outside the range of most tissue autofluorescence. ICG was first produced in 1955 by the Kodak Research Laboratories. It was approved by the FDA for retinal angiography in 1959. Historically, it has been used to measure cardiac output, hepatic function and retinal angiography [35]. Throughout its history, ICG has maintained a high safety index as the number of allergic reactions is very low (1:10,000, as reported by manufacturer). ICG also allows multiple repeated uses due to its short half-life of 150 to 180 seconds and is cleared exclusively by the liver.

After intravenous application, ICG remains largely protein-bound in the intravascular space and is cleared by the liver with an intravascular half-life of approximately three minutes. From the vasculature, ICG undergoes uptake by hepatocytes and hepatic clearance. This can be detected within minutes, peaks over the course of hours and continues for over a day after typical dosing.

Clinical applications

Fluorescence-guided surgery utilizes cameras that can visualize the near-infrared wavelength of ICG. Specialized systems are available for open procedures, thoracoscopic/laparoscopic procedures and robotic procedures. Numerous options are available including the Artemis (Quest Medical Imaging), IMAGE1 S™ Rubina NIR/ICG Technology (Storz), SPY and PINPOINT (Stryker, Novadaq), and Firefly (Intuitive) among others.

One of the most common utilizations for this technology is in biliary surgery - most notably cholecystectomy. Both laparoscopic and robotic utilization of this technology for cholecystectomy are widely reported in the adult literature - but much less frequently in the pediatric literature. In the adult literature, ICG has been found to be noninferior to conventional plain radiographic intraoperative cholangiogram for identifying biliary structures. However, it cannot be used to identify distal common bile duct stones [36]. Although some reports have identified quicker cystic duct identification and a decrease in operative time, there is debate over whether its use has any benefit for uncomplicated cholecystectomy when compared to conventional intraoperative cholangiogram [37]. Use in children is much less frequently reported but those who have report similar findings to the adult population. The Buffalo group reported its use in 31 cases at their institution with no associated complications [38]. They utilized 2.5 mg (2.5 mg/ml solution) of ICG injected just prior to trocar placement. The University of California San Francisco group has also reported good results from direct injection of ICG into the gallbladder at time of surgery (1 ml of 0.25mg/ml solution) [39]. There have also been reports utilizing ICG technology during the Kasai procedure, both for diagnosis as well as intraoperative assistance. Utilizing 0.1 to 0.5 mg/kg injection twenty-four hours prior to laparotomy, multiple studies have found that ICG can improve identification of bile excretion and the extent of the atresia [40][41]. Although still only utilized at a few select centers, this technology has the potential to revolutionize this procedure.

The other common use of near-infrared imaging with ICG in the adult population is the evaluation of bowel viability especially for colorectal operations or other signs of tissue perfusion such as for flaps in plastic surgery. Reports are rare in the pediatric population and have demonstrated feasibility but not superiority over traditional procedures. In the adult population, it is often used to assess for bowel viability prior to an anastomosis and studies have found that it often leads to alterations in the site of the anastomosis (although no study has proven a reduced risk of anastomotic leaks to date). The dose in adults is 15 mg (5 mg/ml concentration) which is given immediately at the time of assessment. The dose in children is much smaller - from 0.05 to 0.1 mg/kg in infants to 5 mg in children. There is little to no data in children about its use regarding viability at the time of anastomosis. A few groups have reported experimental data utilizing ICG in the assessment of necrotizing enterocolitis, but again with no demonstrated benefit.

ICG uptake in hepatocellular carcinoma has been well studied in adults and it has also been found to work well with hepatoblastoma for evaluation of the primary neoplasm as well as the identification of thoracic metastases. While all liver and cancer cells uptake ICG, normal liver cells excrete it at a faster rate, which allows visualization of the malignant cells if the ICG is given well before surgery [42]. ICG injection for primary tumors should be four days prior to the procedure to allow normal hepatocytes enough time to excrete the fluorescent marker. Normal pulmonary parenchyma excretes ICG much faster, so injection for a planned hepatoblastoma metastatectomy can be closer to 24 hours prior to the procedure [43][44].

While there are numerous utilizations of near-infrared fluoroscopy in adult thoracic surgery, many of these are rarely needed in children such as lymph node mapping. The most common utilization reported in children is the identification of pulmonary segments in order to aid in lobe sparing pulmonary resection for congenital pulmonary airway malformations (CPAM). By ligating the arterial supply of the target segment prior to ICG injection, the intersegmental plane is much more easily identified, theoretically reducing the risk of a prolonged postoperative air leak [45]. Others have utilized intrabronchiole injection of ICG but this may be much more difficult in infants due to the small size of the airways [46]. Lastly others have recommended utilization of this technology to identify persistent air leaks although its efficacy has not been tested in vivo [47].

Doses and timing of indocyanine green

application

dose (concentration)

timing

laparoscopic cholecystectomy

children: 2.5 mg (2.5 mg/ml)

Infants: 0.1 mg/kg mg (2.5 mg/ml)

just prior to trocar placement to 18 hours prior*

biliary atresia

0.5 mg/kg (2.5 mg/ml)

24 hours prior to operation

bowel viability/tissue perfusion

small children: 0.05 to 0.1 mg/kg (0.125-0.25 mg/ml)

older children: 5 mg (2.5 mg/ml)

just prior to assessment

hepatoblastoma primary

0.5 mg/kg (not specified)

four days prior to procedure

hepatoblastoma lung metastases

0.5 mg/kg (not specified)

24 hours prior to procedure

identification of pulmonary segment

0.5 mg/kg (not specified)

following ligation of segmental artery

thoracic duct

0.5 mg/kg (5 mg/ml)

injection into inguinal lymph node 60 minute prior

* there is a variation in reports; earlier injection may lead to increased fluorescence of the biliary tree at time of operation

Side effects and complications

The side effect profile of ICG is favorable. It does contain sodium iodide and has been reported very rarely to cause anaphylaxis or urticarial reactions. Furthermore, iodine uptake studies should not be performed for a week following use. Lastly there is no data to support or contraindicate use in pregnant or nursing mothers [48].

Capital investment and case cost estimates

ICG can be acquired from multiple vendors with a cost of about $50 to $85 per 25mg vial. Significant cost is associated with purchasing the technology and the tools needed for ICG fluorescent imaging ranging from $30k to $60k. Some older minimally invasive systems such as Stryker 1588 Advanced Imaging Modalities (AIM) Platforms already include SPY Fluorescence technology and may be readily available in your hospital. The technology could be used by multiple pediatric subspecialities such as general and thoracic surgery, plastic surgery, neurosurgery and transplant surgery. Pricing for all components are negotiated at each hospital system level and may differ significantly.

Ultrasound in Pediatric Surgery (Farokh Demehri and Marcus Jarboe)

Ultrasound (US) has become an increasingly important tool for the pediatric surgeon – both as a diagnostic and interventional instrument. As a radiation free imaging modality, US is particularly well suited for the pediatric population, where other nonradiating modalities such as magnetic resonance imaging require sedation. In addition, the low fat content of most pediatric patients provides excellent US images for diagnosis or procedures. The use of US guidance for various procedures has allowed the application of precision minimally invasive techniques for children. By allowing image guided needle placement, US allows for increased patient safety via increased accuracy and reduced morbidity compared to landmark based percutaneous or open techniques. Despite these benefits, US remains a skill dependent imaging technique and it requires significant education and practice to allow the surgeon to appreciate the benefits of US guided procedures. Rather than addressing the wide range of US capabilities – from vascular US to diagnostic abdominal imaging [49] - this guideline is aimed at the surgeon considering the adoption of US guided techniques in her or his practice with tips on US equipment options and some considerations for a few US guided procedures.

Selecting an Ultrasound Device

Cost is highly variable depending on systems and probe/transducer selections. Good, high image quality can be obtained for the $50 to 60,000 range as of 2020. Transducers and probes add significant cost at about $8 to 12,000 per probe. Specialty probes such as laparoscopic and endorectal probes can be much more. The relationship with hospital and ultrasound manufacturers also plays a role in the price.

Image quality is of great importance. Structures in children are small and poor image quality makes identifying and targeting these small structures very difficult. Good image quality can be found in the less expensive ultrasound machines but care must be taken to select the correct machines because not all manufactures have the same image quality in their base models. The ultrasound you select also should be able to give the user good image quality without multiple adjustments.

Probes or transducers are important features of the ultrasound. Which probes to purchase is dependent on what the machine will be used for. For vascular access (which in children is usually very superficial - even for the central vessels) high frequency linear probes are best. Linear probes can usually be recognized by the straight flat surface of the probe. “Hockey-stick” probes fall into this category, with an ergonomic advantage for needle placement in certain procedures. The high frequency of the probe gives very good image quality with excellent spatial resolution. However, the high frequency ultrasound waves will not penetrate soft tissue very far so it is not suited for such work. For deeper structures (like abscess drainage) lower frequency curved probes work well. The lower frequency allows deeper tissue penetration (although in children there is rarely need for large depth penetration-unlike fetal imaging for example). The curved surface of the probe also creates an image with wider field of view as the imaging goes deeper into the body. Abdominal imaging such as Focused Assessment with Sonography for Trauma (FAST) usually requires a low frequency probe. There are also several specialty probes such as laparoscopic and endorectal probes which can be used for specific purposes.

There is rarely as much room as is ideal in the operating room or on the wards. A small footprint is very useful in allowing the user to place the machine/screen in the appropriate position for optimal use. A large screen size also helps in circumstances where you cannot get the machine as close to the user as is optimal. In general, smaller footprints and larger screen size is best.

There are numerous different technologies and adjustments on ultrasounds that change image quality and character. Some machines make it easy to adjust their machines to optimal image quality while others require an extensive, deep understanding of ultrasound to obtain reasonable images. For the pediatric surgeon it is general best to have simple machines with superior image quality.

Equipment in the operating room tends to take a beating. All ultrasound systems are not equal in durability. Many of the specialty probes are more fragile and need more extensive decontamination and so it is important to have protective containers for these probes. The more frequently used probes need to be durable.

Technical principles

While many machines have numerous dials and knobs that allow fine tuning of the image and detailed calculations, most of these adjustments are beyond the routine needs of the pediatric surgeon. The four core settings to be familiar with on a given machine are

  • transducer selection - this selects the appropriate probe as described above
  • gain - this increases the image signal or brightness. This may allow selective gain adjustment of the deep and shallow aspects of the image. For needle guided procedures, setting the image to a high gain can made needle identification easier.
  • depth - this allows adjustment of the depth of signal shown. This should be adjusted to the minimum depth necessary to include the relevant anatomy.
  • color Doppler - This is helpful to identify vascular structures during an anatomic scan by adding a blue/red color to areas with flow. This often involves a reduction in image quality, so it is not recommended to leave this on while performing a procedure.

For longitudinal/in line needle guidance the ultrasound probe is oriented parallel to the needle axis. This enables visualization of the entire length of the needle. The needle can then be advanced with the tip’s location known relative to nearby major structures. This orientation is ideal for internal jugular access because inadvertent puncture of the carotid artery or lung can be avoided. A common mistake using this approach is to lose sight of the needle itself and to instead view the movement of the surrounding tissue. Losing clear visualization of the needle tip defeats the purpose of in line orientation yet is easy to do with subtle movement of the transducer. This approach requires patience because fine adjustments of the transducer head keep it aligned directly over the needle trajectory.

With transverse needle guidance the transducer head is oriented perpendicular to the vessel and needle axis producing a cross sectional view of both. The needle is inserted at a 45 degree angle at the midpoint of the transducer, producing excellent left-right resolution. Because the needle is seen in cross section, however, it appears as only a small point on the display, with the location and depth of the needle tip unknown. This can be remedied by regularly sliding the transducer down the trajectory of the needle past the tip until it disappears and then back until it reappears so that the tip location is known as the needle is walked down into the vessel.

Developing and improving skill

Formal image guidance courses - Image guided techniques are a valuable set of tools for diagnosis, management, and therapy. To incorporate them into your armamentarium, learning the basics of the different imaging technologies is invaluable: how the technology works, how to optimize your image, and getting comfortable with the US, fluoroscopic, or MRI machines. Image-guided intervention courses are available through several critical care and surgical societies.

Repetition and practice to hone skills - Especially in the case of ultrasound, image guidance is a tool that should be utilized as much as possible and incorporated in as many cases as possible to maintain familiarity and comfort. Developing skills comes with repetition and practice, utilizing ultrasound/imaging for every day cases such as central line placement or abscess drainage is an ideal way of keeping in practice.

Partnering with interventional radiology colleagues - Even after taking a course, learning from others is always encouraged. Interventional radiologists, other surgical colleagues familiar with image guidance techniques and ultrasound technicians are all great resources. Having your colleagues available for assistance is an invaluable resource both early in developing image guidance skills and later when performing complex or challenging cases. In addition, developing the habit of reviewing all images you order followed by reading the report is an effective way of testing yourself to make sure you have seen what the experts saw.

Specific US guided procedures

Central venous catheter (CVCs) placement is among the most common procedures performed by pediatric surgeons. Over the last two decades there has been a paradigm shift from the use of landmark techniques to US guidance in both children and adults largely due to its increased rate of success and improved safety profile. However, in a report by the American Pediatric Surgery Association in 2015, 38% of respondents believe US guidance for CVC placement is unnecessary and only 66% of pediatric surgeons always us US when placing internal jugular CVCs [50].

Bruzoni studied 150 pediatric patients for whom central access was randomized to either US- or landmark guided. Success within three attempts was achieved in 95% of the US group versus 74% of the landmark group (p=0.0001) [51]. There was no statistical difference in complication rate. In a randomized trial of US only versus US and fluoroscopy guided subclavian CVC placement conducted by Pang US guided venous puncture was more accurate for catheterization (p=0.002). There was no significant difference in the mean length of the operation (seven minutes in US group versus six minutes in fluoroscopy group) [52].

A meta-analysis looking at 1100 patients by Gurien found improved cannulation but no statistical difference in complication rate or arterial punctures between US guided CVC insertion versus landmark technique [53]. A study of over 2000 patients by Criss looked at a complete shift in practice of an entire group of pediatric surgeons at a single center from the traditional landmark approach to ultrasound guidance over a two-year transition period. By the end of the transition, pneumothorax complications went from one to zero percent [54].

Emergent extracorporeal membrane oxygenation (ECMO) can be difficult when performed under high pressure situations. Failure or difficulties often result in patient death or serious morbidity. As with central access, ultrasound can be helpful in both catheter placement and optimizing flow. Exact placement of the cannulas offers multiple advantages in flow and safety [49]. Although fluoroscopy and plin radiographs are helpful, ultrasound or echocardiography can often ensure that cannula tip placement is optimal and quickly give the surgeon an idea of volume status and right atrial filling in times of flow problems. Using both fluoroscopy and echocardiography for placement of Avalon® bicaval venovenous ECMO cannulas has been shown to decrease flow related problems requiring cannula repositioning [55]. Similarly, Kashiura found there was a statistically significant decrease in complication rate when US or fluoroscopy was used to place ECMO cannulas without delaying ECMO circuit start time [56].

US is particularly effective in the subpopulation of pediatric patients whose central vasculature is inaccessible by traditional approaches. These patients typically have a prior history of ECMO cannulation, inflammatory bowel disease, prior central venous access or renal disease. In a study of 142 cannulations in low birth weight preterm infants, Breschan demonstrated safety and feasibility of US guided access of the brachiocephalic vein for CVC placement. The success rate was 94% within three attempts. Three patients had inadvertent arterial punctures [57]. In a series of 11 patients, Criss described a novel technique that allows for access to the superior vena cava from a supraclavicular approach in situations where the brachiocephalic vein itself is occluded or inaccessible [54]. These techniques provide a method of access in challenging vascular access situations and should remain a potential tool in the surgical armamentarium in difficult central lines.

Internal anal sphincter botox injection is used to treat chronic obstructive defecation when the internal anal sphincter is unable to relax as associated with Hirschsprung disease and internal anal sphincter (IAS) achalasia. Injection of botulinum into the IAS allows for relaxation of the sphincter without the risk of permanent sphincter damage or incontinence following myectomy or myotomy. Traditionally, these injections are done blindly in the operating room. However, the sphincters in children are very small and difficult to target with feel alone. As one may expect, ultrasound guidance of the botulinum toxin injection has been shown to improve the durability of the initial injection thus decreasing the need for subsequent injections and more definitive operative management for functional obstructive defecation [58]. The US guidance helps improve the accuracy of the injection by showing precisely the location of the needle in relation to the small sphincter complex.

Gastrostomy tube (GT) placement for enteral access is one of the most common procedures performed by pediatric surgeons. Originally developed as an open (i.e. Stamm) procedure, there are a variety of techniques to place gastrostomy tubes that have developed over the decades including laparoscopic, percutaneous endoscopic gastrostomy (PEG), and fluoroscopically guided. The PEG has been used both as a routine technique for GT placement but also in in circumstances where entering the abdomen may be difficult such as in a patient with multiple past abdominal operations. Unfortunately, major complications with PEG occur with variable incidence (five to 17%) and include colonic perforation, small bowel injury, solid organ injury, bleeding and infection [59]. This has prompted surgeons to develop adjuncts to PEG to allow for safer placement. Real time US guided GT placement is a new technique that appears safe, efficient and effective [60]. It relies on transabdominal US for direct visualization while inserting a small gauge needle into a stomach filled with saline. The ultrasound guidance also provides a means of visualizing the stomach while pushing away other structures (e.g. bowel) and identifying organs that may be inadvertently injured (e.g. liver, bowel) with other percutaneous methods. The benefit of US guided GT is especially useful in those patients whose adhesive disease may otherwise preclude a safe entry laparoscopically.

Replacement of a tube that inadvertently falls out or is malfunctioning is a common occurrence. These are frequently replaced at bedside. However, improper placement can result in a number of complications including perforation, fistula creation, peritonitis and sepsis. The standard approach to ensure proper placement is use of contrast fluoroscopy. US guidance can also be useful for quick and safe replacement of gastrostomy tubes in the emergency department or clinic.

Pediatric inguinal hernia repair has gone through an evolution from an open to minimally invasive approach using laparoscopy and needle ligation of the internal ring. Reino-Pires and colleagues recently published a study looking at the feasibility, reliability and safety of US guided percutaneous ligation of the internal inguinal ring in rabbits as a surrogate for indirect inguinal hernia repair in the female pediatric patient [61]. They performed the procedure using a 20-guage peripheral intravenous catheter and a 2-0 monofilament nonabsorbable suture on 28 rabbits that were divided into two groups – one that simulated the human female inguinal hernia and the second that simulated the male’s morphology. The procedure was followed by laparoscopic exploration to evaluate the quality of the repair. During laparoscopy, they found complete and reliable suture repair 66.7% of the time and inappropriate suturing 16.7% of the time in the simulated female hernia group. Inappropriate suturing included a large gap or distal ligation. In the male group, there was a 76.9% complete but unreliable ligation meaning no gap in the closure but the spermatic cord was entrapped. Currently, the senior author offers this approach to female patients which were recently presented at the 2019 American Pediatric Surgical Association conference. This approach is an example of the continued evolution of surgical procedures due to ongoing advances in imaging technology.

Traditionally, open biopsy for soft tissue lesions has been the standard for diagnosis and tissue analysis. However, the use of image guidance percutaneous biopsy is increasingly being used for diagnosis and characterization of malignant benign soft tissue masses. In a study of 180 pediatric soft tissue lesions undergoing computerized tomography or US guided percutaneous core needle biopsies, Metz found image guided percutaneous biopsies to be safe with a highly diagnostic rate (97%) with sufficient tissue for necessary ancillary testing. The study also showed a relatively large number of core needle specimens could be obtained (mean 8.9 core needle biopsies) with a very low complication rate (one percent) [62].

Skin and soft tissue infections such as cellulitis and abscesses are common in the pediatric population. US has long been the modality of choice for evaluating and diagnosing abscesses although there is less literature regarding drainage. US guidance allows for direct visualization of the needle or scalpel while avoiding surrounding structures. Gaspari retrospectively reviewed 377 patients who presented for potential skin abscess. 137 of the patients undergoing US guided drainage were compared to those who underwent abscess drainage without US guidance. The failure rate was statistically lower when US guidance was used (4.4% versus 15.6%; p < 0.005) [63]. Given the relative safety, efficacy and ease of use, US should be used in all cases of suspected abscess.

Fluoroscopy has been invaluable in the localization of radiopaque foreign bodies (FB). However, with radiolucent FBs, pediatric surgeons are forced to rely on palpation and exploration making the operation difficult and often requiring larger incisions and soft tissue destruction to gain access to the FB. Ultrasound guidance is excellent in this situation where the FB will typically have a different echogenicity than the surrounding tissue thereby making the FB easily visible. Mosquito or crocodile forceps are ideal instruments for removal of the FB while using needle localization in combination with ultrasound guidance. This reduces the required incision length and surrounding tissue damage during the extraction.

Image guidance can also be used for tube thoracostomy placement when compared to an open approach. Computerized tomography, fluoroscopy, US or any combination of these techniques may accurately guide chest tube placement. Image guidance is selected based on which modality will best image the pleural lesion (pneumothorax versus effusion) and best guide placement of the drain. US guidance allows visualization of the needle real time as it enters the pleural cavity without inadvertent insertion into other structures (e.g. diaphragm, lung, liver or heart and subcostal vessels). A study by Miraglia retrospectively looked at 25 patients who had pigtail chest tubes placed with real time US and report no major complications. They noted that when using direct US visualization there is no need for a follow-up chest radiograph [64]. A 16-year retrospective study by Lewis looked at 285 children had 303 pigtail catheters placed using US guidance for parapneumonic effusions and empyema. The investigators placed 7-F drains or 8.5-Frfor children older than years. The treatment was successful in 93% of patients after a single drain (98.2% success after a 2nd or 3rd drain placed). There was a 7.8% complication rate which included five periprocedural complications, 14 bronchopleural fistulae and four patients whose drains fell out prematurely. Five patients required surgery for treatment failure but in the last five years of the study no patient required surgical intervention.

Crohn disease is challenging in the pediatric population. Perirectal fistulizing Crohn disease with recurrent abscesses and fistulae is particularly difficult to treat. The principal in managing perirectal Crohn disease is abscess drainage and Seton placement while avoiding any fistulotomies or surgical procedure that would jeopardize continence. To this end, endorectal US (ERUS) has been utilized both as a diagnostic and therapeutic modality in the management of fistulizing Crohn disease. In a retrospective study of 25 children who underwent 42 ERUS procedures, Rosen used ERUS to evaluate suspected perianal disease, guide precise Seton placement through the fistulae and evaluate for persistent periSeton inflammation. The purpose of this postSeton placement surveillance with ERUS was to determine the best time for seton removal. When there was resolution of periSeton inflammation on ERUS the Setons were removed. Although not powered for statistical significance, those that had ERUS surveillance were noted to have experienced a longer perianal symptom free disease course [65].

Lymphatic (LMs) and venous malformations (VMs) are specific forms of vascular malformations commonly seen in children. US is routinely used to diagnose the lesions. The most common treatment for these lesions is sclerotherapy which is nearly always performed with image guidance (ultrasound with or without fluoroscopy). Access to the lesion is performed with US guidance and the injection is performed with ultrasound or fluoroscopic guidance to avoid extravasation. To this end, Blaise demonstrated safe and effective results using US guidance to inject VM’s with polidocanol microfoam with 95.8% of patients having improvement in their symptoms with an average of 2.3 sessions [66]. Scorletti demonstrated similar results with the use of sodium tetradecyl sulfate [67]. LMs, on the on the other hand, are typically injected with doxycycline. For both lesions, once the procedure is completed a compression stocking is placed over the area and left in place for two to three days. This procedure may be repeated in eight to 10 weeks until there is no longer recanalization, swelling or pain.

With increasing comfort with procedural US, one may consider an endless array of new ways to use US for surgical purposes. In theory, many things that can be diagnosed with US may be intervened upon with US guidance. New areas that are being explored include the use of contrast enhanced ultrasound to detect solid organ injury or for distal colostogram/cloacogram in anorectal malformations [68].

Complications

While there are no known risks or complications associated with the use of diagnostic US, when used as a tool to enable a procedure the risks inherent to that procedure remain. For example, US guided CVC placement may still result in any of the usual CVC related complications such as pneumothorax, hemothorax, arterial injury, or catheter malposition. When used effectively in experienced hands, however, US decreases the risks of these complications compared to landmark based approaches while reducing operative time.

Capital Investment and cost estimates

The cost of a portable US machine for procedures varies widely - roughly from $10,000 to over $150,000. Newer handheld US devices are at a lower price point but have generally been designed for bedside point of care diagnostic purposes rather than for surgical procedures. For practical purposes, a surgical US allows the use of a sterile cover, provides high enough image quality for needle placement and can be positioned in an operating without difficulty. Commonly used US brands include: Sonosite , BK Ultrasound, GE and Mindray – among others. In general, an US machine represents a capital investment and pricing for all components are negotiated at the hospital level.

Additional Resources

Innovative Therapy White Paper

The APSA New Technology Committee has provided a set of opinions/guidelines that can be used by APSA members and their institutions to inform and advice decision making related to the introduction and establishment of new technology into surgical practice.

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