Cardiovascular effects of increased intra-abdominal pressure in newborn piglets

Hemodynamic effects of increased intra-abdominal pressure in critically ill children

OBJECTIVE

To evaluate the influence of intra-abdominal pressure on the cardiac index (CI) at different intra-abdominal hypertension grades achieved when performing an abdominal compression maneuver (ACM). Evaluating the effectiveness of the ACM in distending the left internal jugular vein (LIJV).

METHODS

Prospective observational study conducted in the PICU of a quaternary care teaching hospital. Participants underwent the ACM and the IAP was measured with an indwelling urinary catheter. At each IAH grade reached during the ACM, the CI was measured by transthoracic echocardiography and the LIJV cross-sectional area (CSA) was determined by ultrasonography.

RESULTS

Twenty-four children were included (median age and weight of 3.5 months and 6.37kg, respectively). The median CI observed at baseline and during IAH grades I, II, III, and IV were 3.65L/min/m² (IQR 3.12-4.03), 3.38L/min/m² (IQR 3.04-3.73), 3.16L/min/m² (IQR 2.70-3.53), 2.89L/min/m² (IQR 2.38-3.22), and 2.42L/min/m² (IQR 1.91-2.79), respectively. A 25% increase in the LIJV CSA area was achieved in 14 participants (58%) during the ACM.

CONCLUSION

The ACM significantly increases IAP, causing severe reversible impairment in the cardiovascular system and is effective in distending the LIJV in just over half of the subjects. Even low levels of HIA can result in significant cardiac dysfunction in children. Therefore, health professionals should be aware of the negative hemodynamic repercussions caused by the increased IAP.

Abdominal compartment syndrome: risk factors, diagnosis, and current therapy

Abdominal compartment syndrome's manifestations are difficult to definitively detect on physical examination alone. Therefore, objective criteria have been articulated that aid the bedside clinician in detecting intra-abdominal hypertension as well as the abdominal compartment syndrome to initiate prompt and potentially life-saving intervention. At-risk patient populations should be routinely monitored and tiered interventions should be undertaken as a team approach to management.

Abdominal compartment syndrome: clinical aspects and monitoring

Markedly elevated intra-abdominal pressures will result in predictable hemodynamic consequences related to compromised venous return. When the hemodynamic abnormalities are associated with organ dysfunction of failure, patients suffer from the abdominal compartment syndrome. At-risk patients should be routinely monitored for intra-abdominal hypertension, and a multidisciplinary care paradigm should be established. Vigorous resuscitation of both surgical and medical patients highly correlates with IAH and ACS risk. Vigilance, prompt diagnosis, and intervention for abdominal compartment syndrome will reduce the morbidity and mortality in critically ill. Future challenges include altering resuscitation strategies to reduce ascites formation, earlier diagnosis of organ dysfunction, and intra-organ monitoring techniques.

Physiological responses to endoscopic surgery in children

The knowledge on the physiological impact of endoscopic surgery in infants and children is limited. Cardiovascular effects of pneumoperitoneum are mainly the result of an increase in intraabdominal pressure, absorption of carbon dioxide, and a stimulation of the neurohumoral vasoactive system. In infants, pneumoperitoneum alters the heart rate, mean arterial pressure, left ventricular endsystolic and end-diastolic volume, and meridional wall stress. Urine production is significantly reduced, and cerebral oxygenation and blood flow are altered. However, postoperative immune function is preserved or restored faster, and specific physiological responses to endoscopic surgery are well tolerated by otherwise healthy infants and children. The effects in children with specific conditions, such as sepsis, cancer, or organ dysfunction, remain to be investigated.

Antenatal magnetic resonance imaging is useful in providing predictive values for surgical procedures in abdominal wall defects

BACKGROUND

Antenatal magnetic resonance imaging (MRI) is useful for the diagnosis of abdominal wall defects. Its predictive value concerning the possibility of primary closure of the abdominal wall, however, has so far not been reported.

METHODS

Between August 2001 and November 2004, antenatal MRI was performed on 9 patients with abdominal wall defects in whom surgical repair was performed immediately after birth. Areas of the abdominal cavity and exteriorized viscera were manually traced from both sagittal and axial MR images, and the data were further transmitted to a Workstation for MRI Volumetry (Advantage Windows 4.1, General Electric Medical Systems, Milwaukee, Wis). We examined the exteriorized ratio (ER), which is calculated by dividing the absolute volume of the abdominal cavity by that of the exteriorized viscera, and evaluated the predictive value by a retrospective comparison with surgical procedure.

RESULTS

In the primary closure group (n = 5), mean values of ER were 0.33 +/- 0.31 from axial and 0.45 +/- 0.31 from sagittal MR images. In contrast, in the staged closure group (n = 4), mean values of ER were 1.39 +/- 0.40 from axial and 1.34 +/- 0.42 from sagittal MR images. There was a significant difference (P < .05) between the 2 groups for both sets of images. The ER obtained from antenatal MRI correlated well with surgical procedure.

CONCLUSIONS

The ER might be useful for antenatal counseling, planning for delivery, and prediction of the most likely surgical procedure.

Haemodynamic, acid–base and blood volume changes during prolonged low pressure pneumoperitoneum in rabbits

BACKGROUND

The anaesthetic management of small infants during advanced laparoscopic surgery can be complicated by the major pathophysiological effects of increased intra-abdominal pressure. In this study haemodynamic, acid-base and blood volume changes were investigated during pneumoperitoneum in a small animal model.

METHODS

Ten fasted, anaesthetized, mechanically ventilated and multi-catheterized New Zealand rabbits were randomized to carbon dioxide pneumoperitoneum (PP, duration 210 min, pressure 8 mm Hg) or control group. Cardiac index was determined using trans-cardiopulmonary thermodilution and total blood volume was measured by thermal-dye dilution with indocyanine green using a fibreoptic monitor system.

RESULTS

In PP cardiac index (CI), central venous oxygen saturation (Scv(O(2))), total blood volume (TBV) and base excess (BE) decreased significantly during the study whereas all variables remained constant in the control group. After release of PP the measured variables did not return to baseline within 30 min [PP, baseline vs study end: CI 108 (22) vs 85 (14) ml kg(-1) min(-1), Scv(O(2)) 81.4 (8.9) vs 56.7 (9.8)%, TBV 318 (69) vs 181 (54) ml, BE -1.9 (2.7) vs -8.7 (1.8) mmol litre(-1); P<0.01].

CONCLUSION

Our animal model suggests that a decrease in CI, metabolic acidosis and hypovolaemia could occur after prolonged low pressure pneumoperitoneum in small infants, which is possibly not detectable by the standard monitor setting. Therefore, the routine use of an extended monitoring including measurement of central venous oxygen saturation and acid-base parameters should be considered during and soon after operation, when pneumoperitoneum will last longer than 2 h.

Elevated intra-abdominal pressure limits venous return during exercise inVaranus exanthematicus

The effects of treadmill exercise on components of the cardiovascular(venous return, heart rate, arterial blood pressure) and respiratory systems(minute ventilation, tidal volume, breathing frequency, oxygen consumption,carbon dioxide production) and intra-abdominal pressure were investigated in the Savannah monitor lizard, Varanus exanthematicus B., at 35°C. Compared with resting conditions, treadmill exercise significantly increased lung ventilation, gular pumping, intra-abdominal pressure, mean arterial blood pressure and venous return (blood flow in the post caval vein). However,venous return declines at high levels of activity, and mean arterial pressure and venous return did not attain peak values until the recovery period,immediately following activity. Elevating intra-abdominal pressure in resting lizards (via saline infusion) resulted in significant reductions in venous return when the transmural pressure of the post caval vein became negative (i.e. when intra-abdominal pressure exceeded central venous pressure). Together these results suggest that increments in intra-abdominal pressure compress the large abdominal veins and inhibit venous return. During locomotion, the physical compression of the large abdominal veins may represent a significant limitation to cardiac output and maximal oxygen consumption in lizards.

Sonographic biometry of liver and spleen size long after closure of abdominal wall defects

Little is known about the fate of the liver and spleen after closure of the abdominal cavity in patients with abdominal wall defects (AWD). Therefore, counselling families for long-term follow-up and in the case of surgery for acute disease, pregnancy or trauma may be difficult. A total of 18 patients ranging in age from 7 to 18 years, with AWD closed at birth, underwent ultrasound evaluation of liver and spleen size by determination of the index of liver size (ILS) and splenic volume (SV). These values were then correlated with some anthropometric parameters such as body mass index (BMI) and weight; correlation was also sought with some clinical features such as type of defect and direct or staged closure. Nearly all subjects exhibited weight above and BMI below the 50th percentile for age. ILS and SV were significantly above normal limits in all cases and no difference was found with regard to the type of defect.

CONCLUSION

In patients having undergone surgery for abdominal wall defects, liver and spleen usually regain their normal shape and position even though size and volume appear to be larger than in normal controls.

Minimally invasive surgery in neonates

Minimally invasive surgery (MIS) has been one of the most important developments in surgery in the last century. By reducing the incision to small puncture wounds, morbidity, pain, adhesions and scarring are reduced. Due to their small size, neonates have not benefited from the advances in endoscopic surgery as rapidly as their adult counterparts. In the last 5 years, miniaturization of instruments and the development of sophisticated new techniques have enabled paediatric surgeons to apply endoscopic surgery to neonates. MIS is now being performed in both the neonatal chest and abdomen. This article reviews these new developments and discusses the potential for even further improvements in neonatal surgery in the future.

Abdominal compartment syndrome in the intensive care unit

The abdominal compartment syndrome is an increasingly recognized complication of both medical and surgical patients in the ICU setting. This syndrome has been described in a wide variety of clinical scenarios and results from a persistent elevation in intra-abdominal pressure characterized by graded organ system dysfunction. Manifestations of abdominal compartment syndrome include cardiovascular, pulmonary, renal, splanchnic, and neurologic impairment. The diagnosis of abdominal compartment syndrome requires a high level of clinical suspicion combined with an increased intra-abdominal pressure, usually obtained via urinary bladder pressure measurement. Patients at risk for abdominal compartment syndrome warrant close monitoring and we recommend prompt abdominal decompression following documentation of increased intra-abdominal pressure in the setting of physiologic compromise. Abdominal compartment syndrome can significantly contribute to the morbidity and mortality of both medical and surgical patients alike in the ICU. The signs and symptoms of abdominal compartment syndrome should become familiar to all critical care practitioners.

Anesthesia for laparoscopy in the pediatric patient

Pediatric laparoscopy is a novelty that has yet to be critically assessed in large, randomized controlled trials. Just because an operation can be performed laparoscopically does not mean it must be done that way. Many procedures can now be performed more quickly and cheaply through small incisions without the added cardiorespiratory risks seen in laparoscopy. Reports of serious complications are beginning to appear in publications. It will become important to compare laparoscopic techniques with both open surgery and the minimally invasive approach for the same procedure. Many published studies suggest laparoscopy offers significant advantages for some operations and for sicker patients. Practitioners must have a thorough understanding of the physiologic changes that follow pneumoperitoneum and extremes of positioning. As enthusiasm builds, it is essential to maintain safety standards. Endoscopists must be appropriately trained and peer reviewed. The use of virtual reality models now allows surgeons to develop and perfect their laparoscopic skills. When the laparoscopic approach is difficult, surgeons must be willing to convert to open surgery rather than persevere and risk iatrogenic damage. The role of pediatric laparoscopy has yet to be defined, although current trends suggest that it will assume an important position in pediatric surgery.

Influence of increased abdominal pressure on steady-state cardiac performance

The effect of steady-state increases in abdominal pressure (Pab) on cardiac performance was studied in seven acutely instrumented swine with pneumoperitoneum (PP). The animal was placed on volume-preset ventilation, and PP was created by air insufflation. Cardiac output (CO), right atrial (Pra), left atrial (Pla), pericardial (Ppe), and abdominal inferior vena cava pressures (Pivc) were measured while Pab was increased from baseline to 7.5, 15, and 30 mmHg (PP7.5, PP15, and PP30, respectively). Cardiac function curves of the right and left ventricle (RV and LV, respectively) were compared between baseline and PP30. CO presented biphasic changes, with an inital slight increase at PP7.5 followed by a fall at PP30. A significant discrepancy was observed between Pra and Pivc at PP15 and PP30, consistent with development of a "vascular waterfall." Transmural Pla (Pla - Ppe) showed parallel changes with CO, whereas transmural Pra (Pra - Ppe) exhibited a sustained increase. The RV cardiac-function curve was more depressed than was that of the LV at PP30; this suggests an increased RV afterload produced by the elevated airway pressure. These results support the hypothesis that our previously proposed concept of abdominal vascular zone conditions (M. Takata, R. A. Wise, and J. L. Robotham. J. Appl. Physiol. 69: 1961-1972, 1990) is also applicable to steady-state hemodynamic analyses. The abdominal zones appear to play an important role in determining CO, with increases in Pab, by modulating systemic venous return and the LV preload. Simultaneous measurements of Pra and Pivc may provide useful information in the hemodynamic care of patients with elevated Pab.

Transdiaphragmatic pressure gradients and the lower esophageal sphincter after tight abdominal wall plication in the rat

BACKGROUND

Gastroesophageal reflux (GER) is increasingly recognized as a complication of surgical closure of gastroschisis and omphalocele.

AIM

This study tests the hypothesis that forceful abdominal wall closure reinforces the transdiaphragmatic pressure gradients that constitute the main GER-driving force and challenges the antireflux barrier.

MATERIALS AND METHODS

Abdominal and esophageal pressures as well as lower esophageal sphincter pressures (LESP) and length (LESL) were measured in 17 adult rats before tight abdominal wall plication, after it, and 1 week later.

RESULTS

This maneuver increased the transdiaphragmatic expiratory gradient from 0.67 +/- 1.31 to 6.97 +/- 2.68 mm Hg (P < .01) and the inspiratory gradient from 4.36 +/- 1.13 to 10.79 +/- 2.31 mm Hg (P < .01) by markedly increasing both the expiratory (from 1.47 +/- 0.74 to 9.44 +/- 1.85 mm Hg; P < .01) and inspiratory (from 0.98 +/- 0.69 to 6.83 +/- 1.55 mm Hg; P < .01) intraabdominal pressures. These changes were transient, and all pressures became normal after 1 week. The antireflux barrier functioned properly under these new conditions because both LESP and the diaphragmatic pinch-cock pressure (DPP) increased, from 20.3 +/- 3.63 to 26.5 +/- 4.31 mm Hg (P < .01) and from 16.4 +/- 7.25 to 22.5 +/- 4.36 mm Hg (P < .01), respectively, while LESL remained unchanged.

CONCLUSION

Tight abdominal wall plication in the rat generates high intraabdominal pressures and thus reinforces the transdiaphragmatic pressure gradients, but these conditions elicit a healthy barrier response with sphincteric reinforcement. In addition, these changes are transient and fade out some time after operation. These facts should be taken into account for understanding the pathogenesis of GER after repair of abdominal wall defects in human babies.

The abdominal compartment syndrome

1. ACS is caused by an acute increase in intra-abdominal pressure, usually as a result of intra-abdominal hemorrhage. 2. The most common and significant complications are respiratory and renal failure. 3. Abdominal decompression promptly reverses the complications of ACS. 4. Failure to recognize and treat ACS is inevitably fatal.

The pivotal role of the surgeon in the results achieved in gastroschisis

A single neonatal surgical unit treated 42 cases of gastroschisis over a 12-year period (1981-1993). The surgical management of each case was individualised, but every attempt was made to perform a primary repair when possible, based on the premise that this strategy gave the best outcome. The eviscerated intestine was evaluated with the patient under general anaesthesia. Serosal peel was not removed and intestinal atresias were not repaired. Gangrenous intestine was resected. The contents of the bowel were emptied proximally via a large naso-gastric tube and distally via the anus with warm saline lavage. The anterior abdominal wall was stretched and then reduction of the prolapse attempted. Following maximal enlargement of the peritoneal cavity, it was left to the operator to decide whether primary repair was possible and, indeed, permissible in each instance. Staged repairs necessitated the use of silastic pouches. Respiratory and intestinal insufficiency were managed by intermittent positive-pressure ventilation and total parenteral nutrition (TPN). Over one-half of the cases (24 of 42) were under 2.5 kg at birth. Intra-uterine growth retardation was unusual. Ten babies were delivered for obstetrical indications by Caesarean section: 50% were pre-term and in 4 pre-natal diagnosis of a ventral abdominal wall anomaly had been made. The transmural defects were all sited at the umbilicus and were to the right of a consolidated cord in 41 instances. Midgut necrosis due to torsion was encountered in 1 case; 3 further cases with intestinal atresia occurred. Primary closure was obtained in 30 (71%) of the cases reviewed. A prosthetic pouch was used in 12 patients for on everage 10 days in 10 uncomplicated cases. The average length of time in days of tertiary care given to 25 uncomplicated cases treated by primary fascial closure was: ventilatory support 4; intensive care treatment 8; and nutritional source TPN 20. There were 5 deaths (12%): 1 was unpreventable due to prenatal intestinal infarction; 2 were due to abdominal compartment syndrome with renal failure, and, intestinal ischaemia complicating primary and planned staged repairs; 1 caused by intestinal infarction due to torsion of bowel in a pouch; and 1 due to invasive infection. The role played by the strategy taken by the surgeon in the management of gastroschisis is crucial to the outcome. The creation of a compartment-like syndrome produced uncorrectable complications in this series of cases in both primary and staged abdominal wall closures. Minor degrees of this complication proved to be reversible in some patients, which was the reason for the wait-and-see attitude adopted in the management of this problem, often with fatal outcome. Where intra-peritoneal pressure monitoring is not used, the operating surgeon relies on unscientific observations for decision-making at the operating table. The time from birth to operation in 25 of the reviewed cases was on average 5 1/2 h. Of this group, 20 were outborn babies. This is unsatisfactory, but as shown by this review, even in the absence of prenatal management, which should ensure prompt repair, satisfactory results are still possible.

Jack A. Barney Resident Research Award. Cardiopulmonary hazards of perihepatic packing for major liver injuries

BACKGROUND

Perihepatic packing has been shown to result in pathologic intra-abdominal hypertension. Although now recognized as impairing abdominal organ perfusion, the extent to which perihepatic packing affects cardiopulmonary function has not been elucidated.

METHODS

We analyzed a 3-year experience with 11 patients who sustained major hepatic injuries requiring perihepatic packing to control hemorrhage. Pertinent hemodynamic indices consisting of pulmonary capillary wedge pressure (PCWP), cardiac index (CI), oxygen delivery index (DO2), and systemic vascular resistance (SVR), and pulmonary indices consisting of peak airway pressure (PAP), mean airway pressure (MAP), static compliance (CST), and PaO2/FiO2 were measured in the surgical intensive care unit immediately before and after packs were removed.

RESULTS

Unpacking resulted in a significant increase in CI (3.1 +/- 0.4 to 4.2 +/- 0.6 L/min/m2), DO2 (539 +/- 41 to 689 +/- 43 mL min/m2), CST (26 +/- 6 to 36 +/- 4 mL/cm H2O), and PaO2/FiO2 (162 +/- 44 to 237 +/- 53 cm H2O), as well as a significant decrease in PAP (47 +/- 9 to 29 +/- 6 cm H2O), MAP (34 +/- 4 to 27 +/- 3 cm H2O), PCWP (21 +/- 4 to 13 +/- 3 mm Hg), and SVR (1,239 +/- 162 to 887 +/- 130 dyne/cm5).

CONCLUSIONS

Abdominal compartment syndrome following temporary perihepatic packing can result in significant cardiopulmonary compromise. While perihepatic packing can be an early life-saving procedure, timely alleviation of the secondary syndrome may be critical to the ultimate salvage of patients with marginal cardiopulmonary reserve.

Abdominal compartment syndrome

Abdominal compartment syndrome is still a controversial entity. We report on a patient who developed the classical hemodynamic, respiratory, and renal changes of abdominal compartment syndrome after surgical intervention for blunt abdominal trauma. A decompressive laparotomy improved the situation dramatically.

[Intra-abdominal pressure]

The abdominal pressure is a hydrostatic one, which can be measured in the bladder, the rectum and the stomach. In physiologic conditions, the abdominal pressure is variable, with peaks as high as 100 to 200 mmHg at the time of defecation, cough. The increase in abdominal pressure elicited by abdominal distension or compression acts directly on the abdominal compartment, indirectly on the thoracic compartment, and modifies the circulation and the ventilation. Venous return is decreased as the inferior vena cava is compressed. The systemic resistances are also increased as the abdominal vessels are compressed. Therefore the circulation is mainly distributed to the superior part of the body. Although the cardiac output is decreased, the usual haemodynamic parameters remain in the normal range: arterial pressure is increased, heart rate is unchanged, central venous pressure is increased, cardiac failure is unusual. The abdominal distension is also responsible for a restrictive respiratory syndrome, mainly due to the ascension of the diaphragm. The compression of the abdominal content explains renal effects and the decreased diuresis. A sustained increase in abdominal pressure occurs in several clinical conditions. During coelioscopy, abdominal pressure is a under control and the cardiovascular effects are minor. Insufflation with CO2 carries the risk of hypercapnia, gas embolism and pneumothorax. During abdominal tamponade, anuria is directly related to the level of pressures. At an abdominal pressure over 25 mmHg, anuria is common and decompression becomes essential. The G suit increases arterial pressure either by elevating vascular resistances or increasing blood content in the upper part of the body. Therefore cardiac tolerance can be decreased especially in cardiac patients. The adverse effects of abdominal pressure can also be observed in case of peritoneal dialysis and ascites. The risk of regurgitation associated with an increased abdominal pressure must also be kept in mind. The abdominal pressure plays an important role in anaesthesia as well as in surgery. Therefore its measurement, which is easy, should become a routine.

Management of catastrophic neonatal midgut volvulus with a silo and second-look laparotomy

The case of a neonate with midgut volvulus and severe intestinal ischemia extending from the ligament of Treitz to the midtransverse colon is presented. Management consisted of abdominal silo application at the initial exploration to obviate the adverse physiological consequences of increased intraabdominal pressure from reperfusion edema of the intestine. The majority of the intestine was salvaged, and a short segment of ileum was resected. This method of treatment resulted in optimal ventilatory status, renal function, and cardiac performance. The advantages of temporary prosthetic wound coverage in selected cases of midgut volvulus include greater physiologic stability through the avoidance of "intraabdominal hypertension" and the ability to monitor the status of the intestine at the bedside.

Anesthesia for pediatric laparoscopic cholecystectomy

We report the general anesthetic events and clinical concerns encountered with a laparoscopic cholecystectomy in a 19-month-old toddler. Carbon dioxide was insufflated to create a pneumoperitoneum, with resulting intra-abdominal pressures ranging from 5 to 11 mmHg. The end-tidal partial pressure of carbon dioxide (PETCO2) rose as high as 48 mmHg (a 10 mmHg increase from baseline), requiring a 68% increase in minute ventilation to achieve preinsufflation values. Careful monitoring of ventilation, PETCO2, and intra-abdominal pressure are recommended for optimal anesthetic management of the pediatric laparoscopic cholecystectomy patient.

Prediction of successful primary closure of congenital abdominal wall defects using intraoperative measurements

To determine whether intragastric pressure (IGP) and central venous pressure (CVP) would reliably predict successful primary closure of congenital abdominal wall defects (omphalocele/gastroschisis) in newborn infants, we developed the following prospective intraoperative management protocol. Following a temporary trial of fascial closure, infants who had an IGP less than 20 mm Hg or an increase in CVP of less than 4 mm Hg were primarily closed. If IGP was greater than 20 mm Hg or if CVP increased by more than 4 mm Hg, the temporary closure of the abdomen was reopened and a prosthetic silo was placed. Ten infants who were less than 24 hours old and averaged 2.7 kg (range, 1.4 to 4.2 kg) and 37-weeks gestation (range, 32 to 41 weeks) were studied. Eight infants met criteria for primary closure. Their IGP averaged 14 +/- 4 mm Hg (+/- SD) (range, 8 to 19 mm Hg), and their increase in CVP averaged 1 +/- 2 mm Hg (range, -2 to 3 mm Hg). In the two infants who required staged repair, IGP averaged 25 +/- 1 mm Hg (+/- SD) (range, 24 to 25 mm Hg), and the increase in CVP averaged 7 +/- 1 mm Hg (range, 6 to 8 mm Hg). All patients were anesthetized with fentanyl (12.5 micrograms/kg) and paralyzed with metocurine (0.3 mg/kg) intraoperatively. There were no postoperative complications in either group of patients related to increased intraabdominal pressure, and all patients were extubated within 48 hours of the initial surgery. We conclude that the intraoperative measurement of changes in IGP and CVP can serve as a guide to the operative management of congenital abdominal wall defects and can reliably predict successful outcome following repair.

The relative merits of various methods of indirect measurement of intraabdominal pressure as a guide to closure of abdominal wall defects

Visceral ischemia secondary to increased intraabdominal pressure (IAP) following closure of abdominal wall defects presents a serious postoperative problem. Currently, the method of closure and postoperative management are determined by clinical impressions rather than measurement of IAP. In this study various methods of indirectly measuring IAP were compared in 17 rabbits in which IAP was sequentially increased with an intraabdominal balloon. Vesical and inferior vena caval (IVC) pressures were found to have good statistical correlation with IAP. Other methods tested were gastric, rectal, superior vena caval, femoral and brachial artery, and rectus compartment pressures. All were found to be poor indicators of actual IAP. In nine of the rabbits, radiolabeled microspheres were used to assess cardiac output and visceral blood flow. Renal blood flow was very sensitive to increased IAP with dramatic impairment at IAP above 10 to 15 mmHg. Small intestinal flow was less sensitive and did not become significantly diminished until IAP exceeded 25 to 30 mmHg. Our studies suggest that vesical and IVC pressure monitoring should be used to evaluate IAP in the clinical setting. If IAP is in excess of 10 to 15 mmHg surgical intervention is indicated to prevent the development of renal ischemia.

Intragastric pressure measurement: a guide for reduction and closure of the silastic chimney in omphalocele and gastroschisis

In newborn infants with omphalocele or gastroschisis, traditional criteria for reduction of the herniated viscera either primarily or after application of a Silastic chimney have been the baby's color, respiratory rate, and lower extremity turgor. These are not always accurate or immediately apparent. In order to define more objective guidelines for reduction, measurements of intragastric pressure through a gastrostomy tube using a water manometer were carried out. The validity of this pressure measurement was demonstrated in five puppies where intra-abdominal pressure correlated well with inferior vena cava pressure and intragastric pressure measured through a gastrostomy tube (R = .98 and .99, respectively). Over a 3.5-yr period, 25 newborn infants with omphalocele (9) or gastroschisis (16) were treated. Ten underwent primary closure, and 15 were treated by placement of a Silastic chimney with serial reduction and closure. Manual reductions were performed once or twice daily to a maximum intragastric pressure of 20 cm water. Greater pressures demonstrated cardiovascular and respiratory comprise both experimentally and clinically. The mean time required for removal of the Silastic chimney was 4.7 days. There were no infections related to the chimney. There were 2 early and 5 late deaths, a 28% mortality rate. The remaining patients are alive and well. Intragastric pressure measurement in patients with omphalocele or gastroschisis provides objective criteria for safe primary closure and Silastic chimney reduction, shortens the time of reduction, and reduces the number of associated circulatory, respiratory, and septic complications.

Use of Teflon mesh for repair of abdominal wall defects in neonates

Since 1975, we have employed Teflon mesh sutured to the fascial rim in four newborns with giant omphaloceles, with approximation of skin flaps over the mesh. By stabilizing the anterior abdominal wall, the Teflon mesh has prevented formation of large ventral hernias. The mesh has been retained in place for a year or longer, until the growth of the child permits excision of the prosthesis and fascial approximation without difficulty. A similar technique has been successfully employed in a fifth neonate following transabdominal correction of congenital bilateral eventration of the diaphragm to avoid unacceptable increase in intra-abdominal pressure with primary closure of the abdominal wall. The Teflon mesh appears ideally suited for this technique. It is well incorporated into the fascial rim with minimal foreign body reaction. At the time of secondary repair, the mesh can easily excised from the smooth underlying pseudomembrane covering the bowel. All infants achieved stable abdominal walls by this technique. Three patients have undergone excision of the Teflon mesh and fascial repair at 12, 15, and 36 mo of age without difficulty.