Intra-abdominal hypertension (IAH) and abdominal compartmental syndrome (ACS) represent a spectrum of severity of a disorder that affects whole-body systems including cerebral, cardiac, renal and respiratory functions and carries a significant morbidity and mortality 1,2.
Normal intra-abdominal pressure (IAP) is ∼7±3 mmHg, whereas IAH in children is defined as a sustained or repeated pathological elevation in IAP of at least 10 mmHg 3. Abdominal perfusion pressure (APP) (mean arterial pressure minus the IAP) is a more accurate predictor of visceral perfusion and a potential endpoint for resuscitation. Its normal value ranges between 40 and 50 mmHg 4.
ACS in pediatric and neonatal age group is defined as a sustained IAP of greater than 10 mmHg associated with new organ dysfunction or failure 5. It is a known complication of repair of abdominal wall defects (gastroschisis or omphalocele). Omphalocele has been called ‘a prototype for ACS’. However, there are only few reports dealing with ACS in newborns 6.
The best treatment of ACS is prevention, by recognition of the patient at risk, that allows early interventions 7. The WSACS has proposed a graded approach to the management of IAH/ACS. This approach consists of four elements: (a) serial IAP monitoring; (b) prevention of IAH and ACS; (c) medical management; and (d) surgical management 8. When indicated, decompressive laparotomy (DL) often results in immediate and dramatic improvement in all affected organ functions and in stabilization of the patient’s condition 9.
Intravesical pressure monitoring technique recommended by (WSACS) represents the most recent and reliable technique for IAP measurement in neonates 10. It is simple, easy to perform and is considered an intraoperative reference for IAP measurement that is beneficial in determining the type of abdominal closure in repair of congenital anterior abdominal wall defects in neonates 11. However, it has some pitfalls, such as bladder pressure measurements are not feasible in those with bladder trauma and malpositioning of the pressure transducer with regard to the symphysis pubis after repositioning of the patient may lead to fallacies 12.
The aim of this study was to assess the value of IAP monitoring through vesical pressure measurement in the choice and outcome of management of congenital abdominal wall defects.
Patients and methods
This is a prospective study of 25 cases sufferring from congenital anterior abdominal wall defects (gastroschisis and omphalocele) admitted to Mansoura University Children Hospital during the period from October 2013 to October 2015.
The protocol of this study design was approved by the ethical committee of our institution. An informed detailed written consent was obtained from the parents to conduct IAP monitoring through transvesical route during and after surgery for either exomphalos or gastrochisis.
This study included neonates suffering from congenital anterior abdominal wall defects (gastroschisis and omphalocele).
Parents that refused surgical interference or IVP monitoring, patients that were unfit for surgery due to unstable general conditions, patients with associated bladder anomalies as bladder exstrophy, and patients with associated anorectal malformations were excluded from the study.
After proper initial management after birth, cases were cared for in neonatal surgical ICU. Cases of gastroschisis and ruptured omphalocele were urgently prepared for surgery.
In all cases attempt of primary closure of the abdomen was carried out by interrupted sutures. Then, IVP was measured as follows. The patients were catheterized with a 6F infant feeding tube. The bladder pressure was measured directly after attempt of primary closure of the abdomen as recommended by WSACS. The urinary bladder was emptied. Normal saline was instilled into the bladder with a volume of 3 ml/kg. The feeding tube was held vertically up in the mid-axillary line at the level of iliac crest and the height of the column of saline was measured at the end of expiration. All pressures were noted in centimeters of saline (Fig. 1).
After measuring IVP, decision of closure was made according to the recommendations of Santos Schmidt et al.13. If IVP remained under 20 cm H2O, the sutures were tied and fascial closure was performed as usual. If IAP was higher than 20 cm H2O, a surgical silo was placed and staged closure was done or raising of skin flaps and skin closure was performed.
In addition, peak inspiratory pressure (PIP) was measured and APP was calculated during the attempt of closure. Operative time was recorded in minutes. We also documented if the baby needed intraoperative blood transfusion or not.
IAP, temperature, urine output, arterial blood gas, O2 saturation ratio, creatinine level and blood pressure were monitored and recorded after 12, 24 and 48 h, respectively. Great care for follow-up of manifestations of ACS and IAH was done. An IVP greater than 20 cm H2O associated with new onset end-organ compromise including hypotension, respiratory distress, increased ventilatory requirement, uncorrectable acidosis and persistent oliguria or anuria were all indicators for IAH to be dealt with.
Management of IAH if presented was by conservative measures according to the recommendation of Kirkpatrick et al.14 in the form of avoiding excessive fluid resuscitation and diuretics in combination with albumin may be used in hemodynamically stable patients to mobilize third space edema into the intravascular space. In addition, the head position was maintained at less than 20° and muscle relaxant was shown to significantly reduce IAP by improving abdominal compliance 14. DL was performed if conservative measures failed.
The type of secondary closure (fascial closure or mesh repair) and the time at which it was done for cases with silo was noted.
This study included 25 cases diagnosed as congenital anterior abdominal wall defects, 14 (56%) of them were diagnosed as gastroschisis and 11 (44%) were exomphalos. Their ages at the time of surgery ranged from 4 to 720 h with a median age of 24 h. There were more male cases (56%) than were female cases (44%). Gestational age at birth ranged from 32 to 39 weeks with a mean gestational age of 36.88±1.92. The median size of the defect was 3 cm2.
Guided by intraoperative measurement of IAP through transvesical route, primary fascial closure was successful in 60% of cases, whereas silo repair was done in six (24%) cases and skin closure in only four (16%) cases. Regarding the cases that underwent silo repair, five were managed later by secondary closure with in-lay mesh in three cases and fascial closure without mesh in two cases and one case died before secondary closure.
Operative time during the attempts of primary closure ranged from 65 to 110 min with a mean operative time of 86.72±12.01. Fourteen (56%) cases needed intraoperative blood transfusion.
Intra-abdominal pressure measurements
Table 1 and Fig. 2 show the ranges and the mean values of the different readings of the IAP, APP, and PIP. The mean IAP during attempts of closure was 22.60±6.89 versus 18.30±2.47 and 18.28±2.34 after 24 and 48 h, respectively. Fig. 2 also shows wider range of IAP during attempts of closure than all other postoperative values and also there is a high possibility of lower values of IAP in all postoperative measurements than during attempts of closure.
Correlative studies of intra-abdominal pressure
The relation between the values of IAP measured at attempts of primary abdominal closure and those measured 24 h after closure was found to be statistically significant (P=0.003). This means that intraoperative IAP monitoring is a good and sensitive predictor for estimation of postoperative IAP, which have eminent role in prevention of postoperative IAH. Similarly, the calculated APP intraoperatively was found to correlate significantly with the calculated APP 24 h postoperatively (P=0.007) (Table 2).
Statistical analysis revealed that several factors like body weight and the size of the defect have no direct effect on the incidence of IAH. On the other hand, PIP measured at attempt of primary closure was found to correlate significantly with the IAP measured at the same time (P=0.041). Accordingly, PIP also can be used as a good predictor of IAH.
On postoperative follow-up, only two cases developed IAH after abdominal closure (8%) and only one of them needed DL (4%). The IAP at end of operation of this case was 20 cm H2O and thus primary abdominal closure was done. The baby suffered anuria for 2 days. The pressure requirement on the mechanical ventilator was increased to achieve suitable tidal volume. Oxygen saturation ratio was decreasing and severe respiratory acidosis was noticed in arterial blood gases. Measurements of IAP showed a great rise up to 25 cm H2O with failure of conservative methods for management of IAH. Therefore, DL was done and exposed intestinal loops were covered by silo.
On evaluation of cases 24 h after closure, one (4%) case developed anuria, which persisted after 48 h. Furthermore, oliguria was reported in eight (32%) cases after 24 h; however, urine output became normal in five of them within the next 24 h.
Mortality occurred in eight (32%) cases, six of them among gastroschisis cases (75%) and only two (25%) among the cases of exomphalos. Table 3 demonstrates the relation between several factors and mortality. Only the measured IAP was found to be related significantly with mortality (P=0.028). By comparing mortality occurred after different methods of closure, it was found that the highest mortality rate occurred among the cases that were covered by silo (66.6%). On the other hand, cases managed by skin closure showed the least ratio among dead cases (12.5%).
Surgical management of abdominal wall defects follows five key considerations: reduce the evisceration safely, close the defect with a cosmetically acceptable outcome, and with guidance of intraoperative monitoring of IAP, identify and treat the associated anomalies then support nutrition until full independent enteral feeding is established and recognize and treat abdominal, wound, or bowel complications 15.
Nakayama et al.16 and Chin and Wei 17 confirmed that IVP correlated well with inferior vena cava pressure, which reflects IAP, and advocated the use of IVP monitoring as a simple and reliable means of indirectly determining IAP during operations for closure of abdominal wall defects in newborn infants with omphalocele or gastroschisis. Olesevich et al.18 noted faster return to full feeding and shorter hospital stay in newborns in which primary closure was accomplished with an IVP below 20 mmHg. Santos Schmidt et al.13 and Rizzo et al.19 used a lower IVP threshold (20 cm H2O, equivalent to 15 mmHg) to decide between delayed primary closure and the staged approach. They also reported more prompt diuresis and a trend toward less ventilator support, shorter total parenteral nutrition time, and shorter hospital stay 13,19.
In our study, we used IVP threshold of 20 cm H2O as Santos Schmidt and colleagues and Rizzo and colleagues and our results concur with theirs as well as with Shimotake et al.20 who reported that IVC pressure should be kept under 20 cm H2O and found a significant relationship between IVC pressure and visceral blood perfusion guided with Doppler ultrasound.
We did routine postoperative measurement of IAP, which was not done by Olesevich et al.18, who did not believe that routine postoperative measurements of IAP are required. In our study, there was a statistically significant relationship between the values of IAP measured at attempts of primary abdominal closure and those measured 24 h after closure. This means that intraoperative IAP monitoring is a good and sensitive predictor for the postoperative course and, consequently, it has an eminent role in prevention of postoperative IAH and ACS. Accordingly, in agreement with Nakayama and colleagues and Chin and Wei, we concluded that IVP monitoring as a simple and reliable means of determining IAP. However, we believe that further studies in larger number of cases are required to decide whether or not to omit postoperative measurement of IAP depending on the intraoperative values as recommended by Olesevich et al.18.
In the current study, the IAP values measured intraoperatively correlate significantly with the calculated APP and the PIP measured at the same time. Thus, they also can be used as predictors of postoperative IAH/ACS.
In the present study, primary fascial closure was performed in 60% of cases, whereas silo repair in 24% and skin closure in 16%. This is similar to the results obtained by Santos Schmidt and colleagues and Ionescu et al.21, who reported primary closure in 54 and 58.5% of cases, respectively, with intraoperative IVP threshold of 15 mmHg. Nevertheless, Olesevich et al.18 performed primary closure in a much higher percentage of cases (79%). This may be attributed to their higher IVP threshold for closure (20 mmHg) giving better chance for primary abdominal closure. Furthermore, the larger number of cases included in their study should be considered 18.
In the present study, two (8%) cases developed postoperative IAH. This agrees with Clausner et al.22, who have shown that six out of 55 neonates suffering exomphalos (10%) showed signs of inferior venacaval compression after primary omphalocele closure. However, DL was indicated in only one case in our study (4%) after failure of conservation for 2 days. Santos Schmidt et al. 13 reported that there were no recorded cases of postoperative IAH among 22 cases underwent primary abdominal closure. Yet, they noticed temporary oligoanuria in about one-third (33.5%) of patients, which may indicate a mild degree of IAH 13.
This low incidence of postoperative IAH clarifies the great value of intraoperative monitoring of IAP and its direct effect in guiding the type of repair.
In our study, mortality ratio among cases underwent primary abdominal closure (20%), which is low in comparison with mortality ratio recorded in cases repaired with silo (66.6%).This was also confirmed in the results of Santos Schmidt and colleagues and Olesevich and colleagues and the cause might be that silo repair increased the liability for infection and intestinal injuries, which increased mortality ratio rather than primary abdominal closure. We also reported lower mortality ratio among cases underwent skin closure compared with those underwent silo repair, which makes it an appropriate way for repair if feasible.
Measurement of bladder pressure by measuring the height of the saline column is simple and easy to perform. It is an intraoperative indicator for IAP that is beneficial in determining the type of repair of congenital anterior abdominal wall defects in neonates. IAP measured during attempt of closure is a good predictor for the postoperative course, and thus it is a dependent guide regarding the decision about the method of abdominal closure.
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Conflicts of interest
There are no conflicts of interest.