Intra-abdominal Pressure as a Criterion for Abdominal Re-exploration INTRODUCTION

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1 Intra-abdominal Pressure as a Criterion for Abdominal Re-exploration Mohammed Moustafa, Mohammed Mokhtar, Gamal Saleh & Ahmed Moustafa Department of General Surgery Benha University Hospitals, Egypt ABSTRACT This prospective study was designed to evaluate the role of intra-abdominal pressure (IAP) measurement during the early postoperative period as a criterion of the need for re-exploration. The study comprised 90 patients; 60(66.7%) males and 30 (33.3%) females, with mean age 45.15±11.9. All patients were assigned to undergo exploratory laparotomy for acute abdomen for various indications. Each patient underwent single preoperative and eight-hourly postoperative serial IAP measurements for a period of 72 hours via two-ways indwelling Foley s catheter. 12 patients underwent relaparatomy, 10 had a significant increase in IAP during 1st 48 hours postoperatively followed by slow or even no decline during the next 24hours. This rise preceded the day of operative confirmation by 3±1.5 days, whereas the other 2 patients showed slow decline over 1st 72 hours postoperatively. 78 patients had uneventful course, 18 patients had mild increase in IAP levels during 1st day followed by decline over next 2 days. Whereas, 60 patients had a decline in IAP levels during the 1st 72 hours postoperatively. The specificity of the method was 76.9 %, sensitivity 83.3 %, negative predictive value 96.8 %, positive predictive value 35.7 %, with overall accuracy of 77.8 %. This study supports the role of IAP as a relevant marker for deciding the need for relaparotomy, as a part of the on-demand approach. Keywords: intra-abdominal pressure, re-exploration, urinary bladder pressure. INTRODUCTION Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are two clinical entities constituting a continuum of pathophysiologic sequelae ranging from mild elevations of intra-abdominal pressure (IAP) to the devastating effects of organ hypoperfusion and, uneventfully, to death. Although effects of increased IAP on various organs and systems have been reported over 150 years ago, pathophysiologic implications have been rediscovered and definitions and recommendations developed the last few years (1-7). Normal IAP is between 0 and 5 mmhg. IAH is defined as a sustained or repeated pathological elevation in IAP > 12 mmhg, whereas ACS is defined as sustained IAP >20 mmhg (with or without an abdominal perfusion pressure <60 mmhg) that is associated with new organ dysfunction/ failure (1,8). Historically, IAP have been measured directly via a cannula inserted into the abdominal cavity or by an intraperitoneal catheter (9-10). Indirect methods to obtain the most reliable estimation of the IAP are intra-gastric, inferior vena cava, or intravesicular pressure measurements (11). The latter is gold standard for intermittent IAP measurement as it is an effective, easy, and non-invasive technique that has been validated in both animal and human studies and shows a high degree of correlation with directly measured IAP without increased risks for either surgical wound infection or urinary tract infection (1, 12-15). The abdominal cavity may be considered to be a confined space after laparotomy and primary fascial closure. An increase in the volume of the intra-abdominal contents (bowel distension, bowel wall edema, or intra-abdominal fluid collection) will lead to an increase in the IAP 1

2 which serves as a useful indirect measure for determining the intra-abdominal organ perfusion (16, 17). This prospective study was designed to evaluate role of IAP measurement during the early postoperative period as a criterion of the need for re-exploration. PATIENT & METHODS This prospective study was conducted at Emergency Surgical Department, Benha University Hospitals over a period of 30 months, started January The study comprised 90 patients 60 males and 30 females aged 22 to 75 years. All patients were assigned to undergo exploratory laparotomy for acute abdomen for various indications. Standard surgical procedures were done and primary fascial closure of the abdominal wall was attempted in all patients. The abdominal cavity was routinely drained by a minimum of one passive-type capillary drain. With Ethics Committee approval, all patients were informed and consented before surgery after explanation & discussion of the procedure. Patients who were contraindicated to measuring IAP using the bladder technique including pelvic fracture, haematuria or neurogenic bladder and those with organ failure at presentation (i.e. requiring mechanical ventilator support, inotropic drug support) and those who did not have primary abdominal fascial closure (i.e. requiring laparostoma) at the end of the laparotomy were excluded off the study. All patients underwent serial indirect measurements of IAP via two-ways indwelling Foley s catheter using a technique described by Malbrain and Jones (18). The catheter was inserted into the urinary bladder. After draining the urine, 50 cc sterile saline was injected into the bladder and the catheter subsequently clamped for 60 seconds to relax detrosal muscle and connected to the manometry system. The obtained pressures were recorded in cm H2O and converted to mmhg, using the following equation: IAP (cm H2O) / 1.36 = IAP (mmhg). Each patient underwent single preoperative and eight-hourly postoperative serial IAP measurements for a period of 72 hours, Fig.1. Postoperative care: All patients had daily clinical evaluations. Patients were considered uneventful if recovery occurred without signs of peritonitis, anastomotic leakage or ACS within 14 days after operation. Relaparotomy was performed on-demand after clinical and radiological proof of peritonitis or anastomotic leakage. The presence of IAH did not influence any therapeutic decision and it was not used in isolation as an indication for relaparotomy. Abdominal decompression was considered if the patient had two consecutive values of IAP >20 mmhg with organ failure (ACS). Relaparotomy on demand is defined as re-exploration after initial laparotomy carried out only when clinical condition of the patient deteriorates. Postoperative peritonitis was diagnosed when presence of intestinal contents, gases or pus was detected in the abdominal drains, on guided aspiration of fluid collection in the peritoneal cavity or from the wound site with signs of acute abdomen, anal bleeding, temperature >38 0 C. After collection of IAP data, the patients who did not have sustained rise in IAP were taken as an internal control group. The validity of the test was estimated as regards the sensitivity (ability of the test to pick up those who are ill), specificity (ability of the test to pick up those 2

3 who are healthy), Accuracy (ability of the test to pick up both ill and healthy), prediction of positives (probability that a positive test has the disease in question), prediction of negatives (probability that a negative test does not have the disease in question), Likelihood ratio of positives ( score that allows categorization of the test for detection of ill subjects as excellent, good, fair, poor ), Likelihood ratio of negatives ( score that allows categorization of the test for detection of healthy subjects as excellent, good, fair, poor ), Statistical analysis The collected data were tabulated and analyzed using t-test and Chi-square test. Statistical analysis was conducted using the SPSS (Version 16) for Windows statistical package. Values of P <0.05 were considered significant. RESULTS The study comprised 90 patients; 60(66.7%) males and 30 (33.3%) females, with mean age 45.15±11.9, range years. There was a non-significant (P>0.05) difference between patients with uneventful course and who underwent relaparatomy as regards the age and sex presentation. Of the 90 patients evaluated in the study group, 78 had an uneventful course and 12 underwent relaparotomy because of anastomotic leakage or failure of intestinal repair. The clinical diagnosis of the patients enrolled in this study was described in Table 1. In patients with uneventful course, 18 patients had mild increase in IAP levels during 1st day followed by decline over next 2 days. Whereas, 60 patients had a decline in IAP levels during the 1st 72 hours postoperatively. Of the 12 patients who underwent relaparatomy, 10 had a significant increase in IAP during 1st 48 hours postoperatively followed by slow or even no decline during the next 24hours. This rise preceded the day of operative confirmation by 3±1.5 days, whereas the other 2 patients showed slow decline over 1st 72 hours postoperative day. There was a significant (P<0.001) increase in IAP in patients underwent relaparatomy compared to that recorded in patients with uneventful course. None of the patients underwent an immediate abdominal decompression because none of them met the criteria for diagnosis of ACS. Data of IAP measurement in patients enrolled in this study were shown in Table 2 & Fig 2. With respect to the validity of the test, we found specificity of 76.9 % (60 out of 78) and sensitivity of 83.3 % (10 out of 12). Negative predictive value was 96.8 % (60 out of 62), and positive predictive value was 35.7 % (10 out of 28), while overall accuracy of the method was 77.8 % (70 out of 90), the likelihood ratios of positives and negatives categorize this test as a fair, Table 3. Table 1. Patients diagnosis Diagnosis Patients with Uneventful course (No of patients) 3 Patients underwent Relaparotomy (No of patients) Abdominal trauma: Rupture viscus 3 1 Splenic injury 6 - Liver injury 1 - Multi-visceral injury 7 3

4 Strangulated hernia: Inguinal 6 1 Paraumblical 7 1 Intestinal obstruction 15 3 Perforated peptic ulcer 28 2 Perforated viscus 2 1 Tubo-ovarian Abscess 3 - Total Table 2. Mean (±SD) IAP(mm Hg)of the studied patients Patients with Uneventful course Patients underwent Relaparotomy Preoperative 10.2± ±0.1 8 h 9.1± ± h 7.5± ± h 6.7± ± h 5.8± ± h 4.6± ± h 4.2± ± h 3.8± ± h 3.5± ± h 3.1± ±0.3 4

5 Table 3. Validity of the method Positive : True 10 False 18 Negative : True 60 False 2 Sensitivity 83.3% Specificity 76.9% Negative predictive value 96.8% Positive predictive value 35.7 % Accuracy 77.8 % Likelihood ratio of positives 3.6* Likelihood ratio of negatives 0.21* *: Fair method Fig. 2. Mean IAP levels of the studied patients. 5

6 DISCUSSION Patients undergoing emergency surgery are at much greater risk of IAH development than patients undergoing elective procedures and those who are likely to develop secondary peritonitis are at highest risk (19). Uncorrected IAH after laparotomoy may lead to decreased perfusion at the site of an alimentary tract anastomosis and the abdominal wound leading to an anastomotic or wound failure respectively. The resultant re-leak due to anastomotic failure may manifest much later as systemic sepsis. To date, there is no consensus on the timing of relaparotomy in these patients. However, if an elevated IAP is detected early during the postoperative period, relaparotomy could be performed before advanced postoperative peritonitis and systemic sepsis ensue (16,17,20,21). A sufficiently high level of IAP also can cause significant organ dysfunction, resulting in ACS. Development of ACS in patients undergoing laparotomy for trauma has been known to be associated with increased morbidity and mortality. Even the presence of low grade IAH can independently predict development of multiorgan dysfunction and death (22-24). With respect to the ideal frequency of IAP monitoring, almost half of respondents who measure IAP only perform measurements when they feel that it is indicated clinically. However, this method may miss patients with clinically significant elevation in IAP. This agreed with Sugrue et al., (25) who observed that clinical examination is a poor predictor of IAH. In the current study, each patient underwent single preoperative and eight-hourly postoperative serial IAP measurements for a period of 72 hours. This coincided with Sugrue (26) who suggested that measuring IAP 4 to 8-hourly is the most appropriate time to take readings as IAP values tend to rise slowly in the absence of severe intra-abdominal haemorrhage. In the present study, a significant increase in IAP was observed in patients who underwent relaparotomy during 1 st 72 hours postoperatively with a sensitivity of 83.3 %, whereas 16.7 % of the patients showed no increase in IAP. This could be attributed to different state of abdominal compliance curve as the dynamics of the abdominal wall allow great volume changes without a proportional rise in IAP values (19,27). On the contrary, patients with uneventful course, showed decline during 1 st 72 hours postoperatively. Despite no case in this study developed ACS, it is very important to consider monitoring and maintenance of IAP at low levels to prevent a possible rise in ACS incidence. This agreed with Neto et al., (27) who regarded ACS as a threatening condition with high risks and serious consequences. Moreover, Malbrain et al., (1) & Cheatham et al., (2) recommended routine measurement of IAP in postoperative intensive care unit patients. This recommendation is due in part to increasing awareness of the ACS as more than one third of patients undergoing acute abdominal general surgery will develop IAH, and one third of those will develop ACS (19). Comparative studies between on-demand and planned relaparotomy for postoperative peritonitis demonstrated no benefit from the latter approach. However, the rate of negative relaparotomies was still 31% when using the on-demand approach. Moreover, well defined and validated criteria for the selection of patients for relaparotomy within an on-demand strategy do not exist (28,29). This should pay attention to the need for other markers for ondemand relaparotomy. In the current study the likelihood ratios of positives and negatives categorize our technique as a fair test allowing early diagnosis of postoperative peritonitis as the rise of IAP preceded the diagnosis of postoperative peritonitis by 3±1.5 days. 6

7 This study supports the role of IAP monitoring as a relevant marker for detecting postoperative complications in addition to clinical assessment in patients undergoing emergency surgery, and it should be considered as an additional tool to decide the need for relaparotomy, as a part of the on-demand approach to these patients. A sustained elevation in IAP levels with no subsequent decrease precedes the occurrence of postoperative peritonitis after emergency surgery. Therefore this finding should provoke further diagnostic procedures. Initiating early examinations in response to persistently high IAP levels may help to detect postoperative peritonitis even before the problem becomes clinically apparent. This policy might further reduce the rate of negative relaparotomies. However, taking into account the small sample size of our study, further investigations are needed to confirm these preliminary data on a larger population. 7

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