Abdominal Decompression in Children

Abdominal compartment syndrome (ACS) increases the risk for mortality in critically ill children. It occurs in association with a wide variety of medical and surgical diagnoses. Management of ACS involves recognizing the development of intra-abdominal hypertension (IAH) by intra-abdominal pressure (IAP) monitoring, treating the underlying cause, and preventing progression to ACS by lowering IAP. When ACS is already present, supporting dysfunctional organs and decreasing IAP to prevent new organ involvement become an additional focus of therapy. Medical management strategies to achieve these goals should be employed but when medical management fails, timely abdominal decompression is essential to reduce the risk of mortality. A literature review was performed to understand the role and outcomes of abdominal decompression among children with ACS. Abdominal decompression appears to have a positive effect on patient survival. However, prospective randomized studies are needed to fully understand the indications and impact of these therapies on survival in children.


Introduction
Abdominal compartment syndrome (ACS) increases the risk of mortality in critically ill children [1]. It results in 100% mortality if left untreated [2,3]. The importance of ACS is increasingly becoming appreciated in the pediatric intensive care setting. Surgical decompressive laparotomy (DL) with open abdomen management (OA) for ACS is the definitive treatment of choice when medical and less invasive therapies have failed [4][5][6]. Its use has shown improvement in organ function and mortality, though mortality still remains high [7][8][9]. DL is an invasive therapy that is challenging to manage and often associated with significant morbidity and mortality [6,8,9]. Surveys have suggested that some physicians are hesitant to use DL in their patients [10,11]. Decompression of the abdomen has also been achieved in certain cases by less invasive therapies such as catheter decompression, escharotomy, and subcutaneous fasciotomies [12][13][14][15]. This article highlights conditions associated with ACS in children and focuses on the role of abdominal decompression in its management.

Materials and Methods
The National Library of Medicine (PUBMED) was queried for "decompressive laparotomy and children"; "decompressive laparotomy and pediatrics"; "decompression laparotomy and children"; "decompression laparotomy and pediatrics", "percutaneous drainage and abdominal compartment." These searches yielded a total of 67 articles. Eight articles were excluded for language other than English, and 37 were not selected because they were irrelevant or exclusively related to adults. Hence, 22 articles pertinent to the role of abdominal decompression in children were included for review.

Results and Discussion
There is a relative paucity of literature on ACS in children compared to adults. Publications related to abdominal decompression in children are lacking in their scope and generalizability of findings. ACS definitions differed among  long before the manifestation of ACS becomes clinically evident [20]. Therefore, the question of appropriate timing for decompression is a pressing issue that remains unclear.
Overall outcomes are also affected by the techniques used to decompress the abdomen, and the materials and management strategies applied to manage the OA and support dysfunctional failing organs that accompany the diagnosis of ACS. Definitions related to IAH and ACS in children are derived from the consensus statements put forward by the WSACS (World Society of Abdominal compartment Syndrome; http://www.wsacs.org/). However, these definitions are not all directly applicable in children and suggested definitions specific to children have been published and are presented in Table 2 [21].
The true incidence of ACS in children is difficult to determine because of the wide variety of illnesses it is associated with, the relative lack of consensus on the threshold IAP used to define ACS in children, and the paucity of publications. Studies have reported occurrence rates between 0.6 and 9.8% in single-center studies involving critically ill children [1,7,8,17,22].

Risk Factors and Conditions Associated with ACS in
Children. Risk factors that predispose patients to IAH and ACS can be grouped into four major categories based on the pathophysiology of elevated IAP. Some conditions reported to be associated with ACS in children are listed in Table 3.
There may be an increased risk for the development of ACS among children with congenital malformations and genetic disorders. In Steinau's series, 12 out of 26 children who developed ACS had at least one underlying congenital malformation or genetic disorder [9]. In two other pediatric studies, congenital malformations (included arthrogryposis, caudal regression syndrome, biliary atresia, and cystic fibrosis) were seen in 20% (n = 2) of children with ACS [7,17].
The WSACS recommends that IAP measurement be obtained if two or more risk factors for IAH/ACS are present. If IAH is detected, serial IAP measurements should be performed [4,5]. Table 3: Reported conditions associated with ACS in children.

IAP Measurement in Children.
Techniques used to measure IAP can be divided into two groups, the direct and the indirect method. The direct method entails placing a needle or catheter directly into the peritoneal space and transducing the pressure in the abdomen. In clinical practice, its use solely for IAP measurement is limited by the potential for complications such as bowel perforation and peritoneal contamination [23]. However, direct IAP measurement can be easily performed when a peritoneal catheter is already in place or the placement of one is indicated as a therapeutic measure. Indirect methods measure IAP via routes other than the peritoneal space. The intravesical method is the gold standard for measuring IAP [23][24][25]. Several surveys indicate that it is currently the most commonly used technique in children and adults [10,11,26]. IAP is measured via a urethral catheter placed in the bladder. A debubbled fluid column is created by infusing sterile normal saline into the bladder. The optimum volume to use in children weighing 2.7 to 50 kg is 3 mL or 1 mL/kg up to a maximum of 25 mL [19]. In children weighing more than 50 kg, 25 mL can be used as the instillation volume as recommended by the WSACS for adults [4,5]. Appropriate volumes for infants weighing less than 2.7 kg have not been determined. For accurate measurements using this method, the transducer is zeroed at the mid-axillary line with the patient in the supine position. IAP should be recorded at end expiration and when the abdominal muscles are relaxed. A period of 30-60 seconds should be allowed for equilibration of the pressure within the bladder before recording IAP [4,5]. Other indirect methods reported in the literature include the intragastric, intrarectal, intrauterine, and venacaval methods [23,25,27].

Management of IAH and ACS.
The main goals in management of IAH include recognizing its presence by objective IAP monitoring, treating the underlying cause, and preventing progression to ACS by lowering IAP.
Medical management strategies to lower IAP and improve organ perfusion can be guided by the following principles [4].
(2) Improve abdominal wall compliance by ensuring adequate sedation, analgesia, and neuromuscular blockade; removal of constrictive dressings and placing in the reverse Trendelenberg position.
(3) Optimize fluid administration by avoiding excessive fluid resuscitation (especially with crystalloids, consider using hypertonic fluids and colloids early); aiming for a net negative or zero fluid balance by the third day from initial resuscitation and begin fluid removal through judicious diuresis, ultrafiltration, or dialysis once stable.
(4) Optimize systemic and regional perfusion by goal directed fluid resuscitation, hemodynamic monitoring to guide resuscitation, and use of vasoactive medications to maintain adequate abdominal perfusion pressures. They defined ACS as sustained bladder pressure >12 mmHg that was associated with new onset organ dysfunction or failure. They demonstrated improvement of the following physiologic parameters: need for fluid resuscitation, oxygen index, mean airway pressure, vasopressor score, but urine output continued to be minimal 12 hours after DL. Overall mortality was 58% in this cohort [8]. Neville et al. demonstrated decreased oxygen requirements after patch abdominoplasty performed for clinical deterioration associated with criteria defining ACS. PIP decreased also but only in ACS survivors, and oxygen requirements decreased more significantly in survivors compared to nonsurvivors in this cohort. They defined ACS as an increase oxygen requirement and elevation in PIP associated with abdominal distention, worsening renal and cardiac function. The mortality in this cohort was 34.8% [18]. DL is the treatment of choice for most patients with IAH or ACS that is refractory to nonoperative medical management strategies and it is associated with significantly improved patient survival [68,69]. It needs to be performed before irreversible organ dysfunction occurs for better outcomes. Steinau et al. retrospectively reviewed outcomes of ACS in children using a therapeutic algorithm that focused on timely decompression. They showed a survival rate of 78.6% [9]. This is the best survival rate of ACS reported in children thus far, though their approach to abdominal decompression was proactive with IAP > 12 mmHg and only one organ dysfunction constituting triggers for DL. Optimization of conservative therapies and early decompression guided by use of a therapeutic algorithm likely contributed to improved outcomes. Cheatham and Safcsak have shown that using an evidenced based management algorithm in adult patients improved patient survival to discharge from 50 to 75%, and rates of primary fascial closure from 59 to 81% [69].
DL involves making an incision to open all layers of skin, subcutaneous tissue, fascia, and peritoneum [6]. Both midline and transverse incisions have been used in children [8,9,51]. Ideally, DL should be performed in the operating room. In situations where the patient is too unstable for transport or if an operating room is not readily available, DL can be performed in the pediatric intensive care unit (PICU). In Pearson et al.'s report 13 of 27 patients had DL performed at the bedside and 4 of 15 episodes of ACS in Beck et al.'s study had DL performed at the bedside [7,8]. Successful management of ACS using DL may depend upon the use of an open abdomen management strategy.

Open Abdomen Management. DL is often supported by
open abdomen (OA) management to avoid recurrence of ACS. OA management is achieved by leaving the fascia and the skin open, and temporarily covering the viscera. An OA with temporary abdominal closure (TAC) may also be necessary following operations in which edematous viscera preclude easy fascial closure, management of abdominal wall defects or in which an adult size organ has been transplanted into a small child [22,34,52,53,55,70,71]. The ultimate goal of OA management is to achieve prompt primary fascial closure without complications. To achieve successful primary fascial closure entails a multidisciplinary approach in management of the open abdomen [72]. The ICU team is working toward safely removing excess fluid while preserving organ function, preventing infection, and treating concurrent comorbidities. The surgical team has the task of choosing the ideal TAC technique for each patient and managing dressing changes. To avoid the development of recurrent ACS and lateral retraction of the abdominal muscles, the surgical team should constantly be seeking out the earliest optimal time for primary fascial closure. The challenge of OA management increases when delayed primary fascial closure is not achievable because abdominal wall reconstruction will need to be addressed at a later date [55]. Most pediatric studies reviewed did not focus on successful achievement of primary fascial closure after management of ACS. Three studies addressed it. A study by Steinau et al. reports 72% of patients achieved primary fascial closure in a median of 53 (range 10-63) days. Incisional hernias needing repair occurred in 27.3%, one needed closure of a stoma and another one needed relaparotomy for an ileus due to adhesions [9]. DL with OA management was used in 26 patients with ACS. Time to definitive abdominal closure averaged 8.6 days (range, 1-61 days) needing an average of 3.2 separate operations (range, 1-14) to achieve abdominal wall closure. This study did not clarify if primary fascial closure was achieved or not. Postoperative complications that could be related to DL in this study included wound infection (n = 5), fascial dehiscence (n = 1), and enterocutaneous fistula (n = 1) [8]. In another study, 11 of 23 (47.8%) patients who underwent patch abdominoplasty for ACS achieved delayed primary fascial closure. Complications in this cohort included mesh infection (n = 2), recurrent ACS (n = 1), and subsequent incisional hernia for the five patients that did not achieve primary fascial closure [18].
3.6. Temporary Abdominal Closure. Temporary abdominal closure (TAC) techniques have recently been characterized into three generations reflecting the historical evolution of the devices, from simple coverings, to contain the viscera, to closure devices to cover and aid in the gradual approximation of the abdominal edges [9,42,70,72,73]. The first generation aimed at bridging the defect and covering the abdomen, using biodegradable or synthetic materials. The second generation aimed at fluid control and improved barrier function and the third generation aimed at gradual approximation of the wound by the use of gradual manual tension such as the Wittmann patch or negative pressure [72]. Several of these techniques have been reported in children and are presented in Table 4.

Catheter Decompression.
Abdominal decompression by catheter decompression is gaining favor because of its less invasive quality and decreased morbidity associated with its use. Abdominal decompression has been achieved by percutaneous catheter decompression in situations in which intra-abdominal fluid plays a significant role in the underlying diagnosis [14,31,37,49]. Bedsides, sonography can assist in distinguishing patients with progressive IAH predominately related to intraperitoneal fluid, from those with bowel wall edema or a space-occupying lesion, where catheter decompression will not be useful and may lead to unnecessary complications.
Percutaneous drainage (PD) of peritoneal fluid can prevent the progression of IAH to ACS altogether or may allow time to stabilize the patient for DL [14,31,49,50]. Improvement in physiologic criteria has been seen with insertion of PD for IAH and ACS. A retrospective review was performed of 32 neonates who had IAP monitoring. Clinical presentation was divided into I and II grade signs. I grade signs included increased abdominal circumference, reduced abdominal wall compliance, and ultrasound confirmation of fluid in the abdominal cavity. II grade signs included necrotizing enterocolitis, septic shock, renal failure, low cardiac output, increased central venous pressure, delayed capillary refill time, acute respiratory failure, increased PaCO 2 , decreased PaO 2 , oliguria/anuria, and weak or absent femoral artery pulses. Twenty-eight patients met criteria for IAH, defined as IAP > 10 mmHg with each I grade sign and two symptoms from II grade signs while ACS was defined as IAP > 20 mmHg, with each I grade sign plus at least three symptoms of grade II signs. Insertion of a PD was performed in all cases. After insertion, resolution of symptoms was observed in all patients but with varying improvements in clinical parameters and measurements [12]. A study including 10 PICU patients with ACS reported a decrease in IAP and ventilatory parameters and an increase in urine output rapidly after abdominal decompression performed by PD in 5 patients and DL in 2 patients. The two patients with DL subsequently died while only one of the five with PD died. Overall mortality in this study was 40%. Latenser et al. in a pilot study compared PD with DL in adult and pediatric patients with greater than 40% total body surface area (TBSA) burns. There was reduction in IAP after catheter placement in all nine patients with IAH. Only 4 patients with failed PD required emergent DL after developing ACS. They concluded that PD is safe and effective as a decompression modality for decreasing IAH and preventing ACS in patients with less than 80% TBSA burns [14]. It can be very useful in patients where DL is less desirable because of a high surgical risk. PD successfully avoided the need to perform a DL in an anticoagulated-patient undergoing extracorporeal life support who developed ACS [37].
Paracentesis using angiocatheters, peritoneal dialysis catheters, and hemodialysis catheters have been reported [14,31,49,74]. Needle decompression was reported in a child with ACS resulting from tension pneumoperitoneum [45]. The successful use of a Penrose drain has been reported in a very-low-birth-weight (VLBW) neonate weighing only 650 gm [75].
Complications with catheter decompression have not been well reported in the literature. Latenser et al.'s study reported peritoneal contamination that did not progress to peritonitis in one patient [14]. The VLBW neonate developed hernias at the catheter insertion sites upon removal of the Penrose drain, resulting in the need for reconstructive laparoscopic surgery [75]. Some patients have progressed to death in spite of decompression by catheter placement [49]. It is important to note that when IAH or ACS is not ameliorated by catheter decompression and aggressive medical management, DL should be performed immediately [74].
DL was widely considered the only therapeutic option for abdominal decompression in the recent past but less invasive methods of abdominal decompression like catheter decompression are gaining favor because of the decreased morbidities they may offer compared to DL with OA management. Only patients with moderate amounts of free intraperitoneal fluid and no surgical intra-abdominal pathology may benefit from this procedure. Patients with no surgical intra-abdominal pathology and insignificant amounts of intraperitoneal fluid will need other means of decompression. Minimally invasive subcutaneous fasciotomy has been described in adults but its use has not been reported in pediatrics. It entails subcutaneous division of the linea alba between cutaneous incisions or subcutaneous anterior medial rectus abdominis fasciotomy through small skin incisions (with drainage of intra-abdominal fluid) [76,77].
Reported complications with OA management include intra-abdominal abscesses, enteroatmospheric fistulae, and herniae when primary fascial closure cannot be achieved. It is difficult to tease out morbidity or mortality associated with DL or OA management from morbidity and mortality related to the underlying cause and the progression of ACS itself. However, arguments for its benefits can be made based on the improvements in physiologic parameters and when death from ACS is imminent, in its absence [78]. Large randomized studies could help answer this question but based on the few publications that suggest benefit with its use, it might become ethically challenging not to provide DL in the control group when the need arises. Few studies have looked at long-term complications from DL and OA management. A questionnaire was sent to the parents of 22 ACS-survivors following DL with a resulting  Critical Care Research and Practice 9 response rate of 72.7% (16/22). According to the responses to the questionnaire, the scar area brought physiological or psychological discomfort to 10 of 16 children. Of those, subjective impediment degree was put at 100% by five children, at 80% by one child, and at 50% by two [9]. An adult study looking at the long-term impact of DL on physical and mental health, quality of life, and subsequent employment showed that DL initially decreased physical, but not mental health perception compared with that of the United States general population, and that abdominal wall reconstruction restores physical and mental health to normal levels [79]. Another similar but prospective study amongst adults compared patients discharged with an incisional hernia, and primary fascial closure after DL, to the general public. It demonstrated that at 6 months postdecompression, physical and social functions were significantly decreased among the incisional hernia group but not the primary fascial closure group. By 18 months, the incisional hernia group had normal physical and mental health. The two groups had decreased but similar quality-adjusted life years and similar ability to resume employment. They concluded that ACS does not appear to have a long-term impact on physical or mental health, whether same admission primary fascial closure is possible or a chronic incisional hernia is required. ACS is not as debilitating and life altering as might be expected [80].

Conclusions
ACS is a potentially lethal condition associated with a wide variety of conditions some of which are seemingly innocent at presentation. Clinicians should screen children in the intensive care unit at risk for developing ACS on an ongoing basis. ACS must be recognized early. Clear consensus definitions specific to pediatric patients based on organized studies are still necessary and will help in ACS recognition. Appropriate treatment options supporting organ function and timely assessment for catheter or surgical decompression should be employed. Current therapies being utilized for abdominal decompression appear to have a positive impact on patient survival. However, prospective randomized studies are needed, to fully understand the indications and impact of therapies directed at IAH and ACS management on survival in children. A number of children who would have died without intervention may survive after management of ACS by abdominal decompression, but may acquire varying physiological and psychological complications. Long-term studies to understand the impact of abdominal decompression techniques need to be conducted in children.