Objective
We sought to establish normative values of intraabdominal pressure (IAP) in postpartum women with and without arterial hypertension.
Study Design
Bladder pressure was measured via a Foley catheter 1 hour following completion of cesarean section in supine and semirecumbent positions in 21 patients.
Results
Mean supine IAP (6.4 ± 5.2 mm Hg) was significantly lower than semirecumbent IAP (11.6 ± 7.2 mm Hg) ( P < .05). Body mass index (BMI) was significantly correlated to IAP regardless of the gestational age (r 2 supine = 0.46, semirecumbent = 0.37; P = .004 for either). Increasing gravidity was associated with decreasing IAP. Patients with arterial hypertension had higher BMI, were delivered earlier, and had higher IAP than patients with normal arterial pressure, either in supine or semirecumbent position. However, these relationships were not significant when results were controlled for BMI.
Conclusion
Postcesarean section IAP is higher than in the general surgical population. Patients with hypertensive disorders have IAPs approaching to intraabdominal hypertension range.
The importance of abdominal compartment syndrome (ACS) has long been recognized in the trauma and critical care literature for its potentially injurious effects. ACS is the most dreaded consequence of elevated intraabdominal pressure (IAP). It is defined as IAP >20 mm Hg with new-onset multiorgan dysfunction/failure affecting the cardiovascular, renal, mesenteric, central nervous, and musculoskeletal systems. Although initially thought to primarily affect trauma patients, ACS has now been identified in a wide variety of medical and surgical conditions. In all, 8% of medical intensive care unit (ICU) patients had evidence of ACS (IAP >20 mm Hg with new-onset organ dysfunction/failure) in 1 multicenter observational trial.
Failure to recognize the presence of intraabdominal hypertension (IAH) (defined as IAP ≥12 mm Hg ) and ACS can be detrimental given its associated morbidity and mortality. Reported mortality rates from ACS range from 40-100%. It is believed that IAH and evolving ACS with its concomitant tissue and organ hypoperfusion are often overlooked in critically ill patients, with the clinical consequence ascribed to progression of the primary illness. Identification of patients at risk, early recognition, and appropriate intervention are essential to effective management. Further, the decision to proceed with surgical decompression is not one to be taken lightly given its associated morbidity. Despite primary decompression, ACS may still have a high rate of mortality. Some authors have attributed this to recurrent or persistent IAP.
The most accurate method for measuring IAP is directly via an intraperitoneal catheter. However, potential complications limit the clinical use of this method, specifically, bowel perforation and peritoneal contamination. Several indirect methods for obtaining the IAP have been developed to avoid these complications. The intravesicular (intravenous pressure [IVP]) method, first described by Kron et al, has become the gold standard.
Several studies have been undertaken to examine and quantify elevated IAPs. Kron et al defined normal postoperative pressures following abdominal surgery to range between 3–15 mm Hg. Sugerman et al described normal IAPs in 84 morbidly obese individuals and 4 healthy individuals. It was found that increased sagittal diameter was associated with increased IAP in this study. In 2001, Sanchez et al randomly selected 20 hospitalized patients in an attempt to determine normal IAP. They found that although body mass index (BMI) was positively related to an increased IAP, no such relationship was noted for sex, age, or medical/surgical histories. Subsequent to these studies, there has been a paucity of information with regard to IAP in an entirely female population and no research has been conducted in an obstetric arena, despite obstetric surgery being among the most common surgery performed daily across the world.
Preeclampsia is a common disorder complicating approximately 5% of all pregnancies and causes significant perinatal morbidity. Preeclampsia refers to a syndrome characterized by the new onset of hypertension (blood pressure >140/90 mm Hg on 2 occasions at least 6 hours, but not >7 days, apart) and proteinuria >20 weeks of gestation in a previously normotensive woman. While diagnosis of the disease appears to be straightforward, the definitive etiology is not clearly known. One of the frequent findings in patients with preeclampsia is the endothelial defect as evidenced by increased peripheral and pulmonary edema and intraabdominal transudation. Combining increased frequency of PEC in overweight patients with intraabdominal transudation it is feared that ACS could be overly diagnosed solely based on the criteria for nonpregnant population.
The purpose of this study was to establish normative values of IAPs in postpartum women who underwent cesarean section with and without coexisting hypertensive disorders.
Materials and Methods
A total of 21 patients were prospectively enrolled from April 2007 through April 2008 at Yale-New Haven Hospital. Subjects were invited to participate provided they were to undergo a cesarean section, either primary or repeat. In all cases, a transurethral bladder (Foley) catheter was required secondary to the particular surgery. Gestational age was determined by last menstrual period and confirmed by a first-trimester ultrasound.
Following informed consent, measurements of IAP were performed at the bedside within 1 hour of surgery completion. The technique used to measure IAP was based on the method of Kron et al and modified by Cheatham et al and Fusco et al. Briefly, a pressure transducer system was assembled and flushed. A 30-mL syringe was attached to the distal stopcock. The transducer system was connected to the pressure monitoring cable and zeroed at the level of pubic symphysis. The patient was placed in the desired position (supine or semirecumbent). A drainage system was clamped distal to the collection sample port of the Foley catheter. The sampling port was cleansed with alcohol wipe and a transducer was attached.
A syringe with the stopcock turned off was turned toward the patient and the pressure bag was opened. The operator drew 25 mL of saline back to the syringe and turned the stopcock back to the pressure bag. Next, 25 mL of saline was injected into the bladder. Any air seen between the clamp and urinary catheter was expelled by opening the clamp and allowing the saline to flow past it. After the air had been expelled, the catheter was reclamped; 30-60 seconds passed before a pressure reading took place. Respiratory variation was taken into account. All measurements were recorded at the end of the expiration.
The modified method allows the patient’s catheter apparatus to be maintained as a closed system, reducing the risk for catheter-related urinary tract infection and sepsis. Additionally, it minimizes the risk to the health care provider for a needlestick or body fluid exposure while simultaneously decreasing the total time required to obtain an IAP. Criteria for exclusion included previously laboring (prior to cesarean section).
Each patient included in the study had bladder pressures measured in both the supine and semirecumbent positions (head of bed [HOB] elevation: 45 degrees). In the postoperative recovery area, the patient was placed in supine position and the Foley catheter was clamped distal to the sampling port using a previously described closed-system technique. The measuring apparatus was zeroed at the level of the symphysis pubis and the IVP obtained. The catheter clamp was released and the patient was then placed in semirecumbent position via manipulation of the head of the recovery bed. Once again, the catheter was clamped, the apparatus was zeroed at the level of the symphysis pubis and an IVP obtained. Measurements were recorded at the end of inspiration.
Data were analyzed using standard statistical methods. Descriptive statistics including means, ranges, and SD were used to describe the maximum IAP measurements for each subject. Fisher’s exact test, Student t test, and regression analysis were used as appropriate. A P value of < .05 was considered significant for all tests.
Results
A total of 21 patients were enrolled to the study ( Table ). Patients had significantly higher IAP in semirecumbent position compared to supine position (mean IAP: supine, 6.4 ± 5.2 mm Hg; semirecumbent, 11.6 ± 7.2 mm Hg; P < .05) ( Figure ). IAP was significantly correlated to prepregnancy BMI and this was not affected by estimated gestational age at the time of delivery (supine, adjusted r 2 = 0.46, P = .004; semirecumbent, r 2 = 0.37, P = .004). Patients with arterial hypertension had higher BMI (37.3 ± 10.0 vs 33.3 ± 7.7) and were delivered earlier (estimated gestational age: 35.2 ± 5.5 weeks vs 37.4 ± 3.0 weeks). Increasing gravidity was associated with decreasing IAP (beta = –0.42). However, these differences did not reach statistical significance. Compared to patients with normal arterial blood pressure, there was increased IAP both in supine and semirecumbent positions in pregnancies complicated with arterial hypertensive disorders, although these relationships were not significant when results were controlled for BMI.
