Intra-abdominal hypertension; prevalence, incidence and outcomes in a low resource setting; a prospective observational study

Study design

A prospective observational study.

Study setting

This study was conducted in the surgery department of Mulago National Referral Hospital (MNRH), Kampala district. MNRH is Uganda’s national referral hospital. It is also the teaching hospital for the Makerere University College of Health Sciences. It has a total bed capacity of 1500, an inpatient turnover of 120,000 patients and attends to over 480,000 outpatients annually. The study was conducted between January and April 2015. Patients were followed up until discharge or death.

Participants

All patients above 7 yr that were scheduled for emergency laparotomy in the surgery department of MNRH were eligible for the study provided they were not pregnant, urinary catheterization was possible and did not have any of the following; pelvic fractures, haematuria, neurogenic bladder, cardiac, renal or respiratory conditions.

Study procedure, measurements and sample collection procedure

A patient was included in the study only after a decision to operate upon him/her was taken by the attending surgical team. Patient particulars (age, sex, tribe, weight, height, past medical history) were noted along with the diagnosis and indication for surgery. Measurement of IAP was taken three times on each occasion and the average was recorded. The measurements were done in the preoperative period and then postoperatively at 0, 6, 24 and 48 h. Zero hour was taken as time of up to 3 h after surgery. If IAP remained below 12 mmHg, measurements were discontinued after 24 h. Other parameters were measured preoperatively and then after surgery at 0, 6, 24 and 48 h. These included; blood pressure, pulse rate, respiratory rate, oxygen saturation (SpO2), temperature, urine output, Glasgow coma score, duration of surgery, blood urea, serum creatinine. Zero hour was taken as time of up to 3 h after surgery.

Post-operational findings to note include: duration of hospital stay, morbidity (burst abdomen), and mortality. The patients were followed up until discharge for morbidity (burst abdomen, relaparotomy, wound dehiscence and wound sepsis) and mortality.

Details of the measurement of the IAP

The patient was placed in supine position and catheterized with a Foley’s catheter. The bladder was drained until no urine was flowing out from the catheter. The Unometer (UnoMeter™ Abdo-Pressure™ manufactured Unomedical, Uno label 005–2) was connected to the Foley’s Catheter then 20 mls (10–20 mls in Paediatrics) of sterile saline was infused into the bladder through an opening on the Unometer (as recommended by the manufacturer of the Unometer). The tubing of the collecting bag was clamped. The symphysis pubis was the point of zero reference. The patient was told to expire and hold their breath, in that moment the pressure was measured in millimeters of mercury. The measurement was repeated three times with a gap of about 3 min between the readings.

Study variables

Organ system derangement

Central nervous system

Glasgow Coma Scale: 15–14; Mild, 13–9; Moderate, <8; Severe.

Below 14//15, was be considered as CNS dysfunction

Study size

The sample size for prevalence and incidence was calculated using the modified Keish and Leslie formula using an estimated proportion of 50.5 %, from a multicentre epidemiological study [12], and a precision of 0.05. The estimated sample size for comparing IAH and outcomes was derived from a general formula for calculating the total sample size using the z statistic for comparison of two proportions with an estimated proportion of 80 % from an Indian study [13]. The larger sample size of 141 patients was considered.

Statistical methods

Ethical consideration

Informed written consent was obtained from the participants; a translated consent form was availed to non-English speaking respondents. Accent was obtained from the children and written informed consent from the guardian. Confidentiality was observed through strict storage of data and no use of names. Ethical Approval was obtained from; Mulago Hospital ethics committee, Makerere University school of medicine ethics and research committee and the Uganda National council science and technology.

Characteristics of the study participants

Intra-abdominal hypertension

Prevalence and incidence of IAH

The prevalence of IAH in this study was 25 % paediatrics and 17.4 % adults. Overall incidence of IAH was 20 % paediatrics and 21 % adults. The incidence of IAH at 0, 6, 24 and 48 h is presented in the Table 2.

Outcomes associated with IAH among patients scheduled for emergency laparotomy

In the paediatrics group, Patients with IAH postoperatively at 6 h were more than twenty four times at risk of dying as compared to those without IAH, RRR = 1:24, 95 % CI (1.371–560.178), p-value 0.048.

In the adults group, patients with IAH preoperatively were 2.7 times more likely to develop respiratory dysfunction compared to those without IAH, RRR = 1:2.783, 95 % CI (1.148–6.744), and p-value 0.023.

Patients with IAH postoperatively at 6 h and at 24 h were noted to be more than 2.933 and 3.769 times more likely to die than those without IAH, 95 % CIs (1.017–8.464) (1.113–12.760) and p-values 0.047, 0.033 respectively

There was an increasing likelihood or risk of dying with increasing time (hrs) among patients postoperatively with IAH.

Basic Characteristics of the study participants

In both the paediatrics and adults groups, there was a male predominance that is 65 % in paediatrics and 80.7 % in adults; a similarity is seen in a number of studies. A study done in India had 76 % males [13], a study in children 57 % male [14], in USA two studies were done which reflected males 70 % [15] and 72 % [16]. The mean age in the paediatrics group was 14.25 years (SD ± 3.16) and adult age was 34.4 yrs (SD ± 13.72). The median age for paediatric and adults group was 15 and 30 years respectively which is consistent with the Uganda population statistics which show that Uganda has a young population [17]. In this study, intra-abdominal sepsis had 66 % of the study population, which is similar with findings from Khan et al. (2010) where 64 % presented with intra-abdominal sepsis.

Intra-abdominal pressures

The mean IAP before and after emergency laparotomy were 15.4 (SD ± 3.6) mmHg and 14.21 (SD ± 5.0) mmHg, respectively. The mean IAP in the study group of Khan et al. before and after decompressions were 16.6 (SD ± 9.4) mmHg and 10.3 (SD ± 3.1) mmHg, respectively [13]. Meldrum et al. reported higher values of preoperative IAP, 27 (SD ± 2.3) [15]. This can be explained by the observation that in our study, 66 % of the patients had peritonitis secondary to gut perforation leading to elevated IAP which, after decompression and removal of liters of fluids and gas, returned to normal level immediately.

Prevalence of IAH

The prevalence of IAH in our study was 25 % paediatrics and 17.4 % adults. In the adults group, this was slightly lower than Murtaza et al. who showed a prevalence of 28 % [18], however this can be explained by the fact that Murtaza et al. looked at ICU patients who are generally sicker than the general patients we looked at. Again in the paediatrics group, the prevalence was lower compared to Ozden et al. with 49.3 %, this is still explained by the different study populations, and this study was carried out in the emergency ward setting compared to NICU or PICU.

Incidence of IAH

In the adult group, the incidence of IAH in literature varies from 2 to 81 % depending on the values used to defined IAH and patient population [19, 20]. However, only a few studies have reported the incidence in paediatrics, 12.6 % Thabet et al. [21], and 9 % Divarci et al. [14]. The incidence of IAH in our study was 20 % paediatrics and 21 % adults. The incidence in the adult group at the 0, 6, 24 and 48 h postoperatively was 8.1, 12.8, 8.7 and 8.7 % respectively. At 6 h the incidence of IAH increases and then drop at 24 and 48 h, this is similar to Khan et al. reported 0 % at 0 h, 3.55 % at 6 h and 0 % at 24 h [13]. The incidence of 21 % in the adults group is high therefore close attention should be paid to these patients postoperatively to avoid poor outcome. The incidence in paediatrics group at 0, 6, 24 and 48 h was 15, 0, 5 and 0 %.

Outcome factors associated with IAH

In the adults group, the statistically significant outcomes associated with IAH include mortality and respiratory system dysfunction. Preoperative IAH was significantly associated with respiratory system dysfunction while post-operative IAH was significantly associated with mortality. Khan et a[13]l reported similar findings and the preoperative respiratory dysfunction is explained by the splintage of the diaphragm as the IAP progressively raises, however the after surgery respiratory function could have improved due to the decompression from surgery.

The mortality associated with IAH postoperatively at 6 and 24 h shows at need to objectively measure IAP in patients at risk hence early recognition and proceeds with effective intervention.

In the paediatrics group, the significant outcome associated with IAH after multivariate analysis was mortality at 0 h, which could be explained by probable delay in surgical intervention or recognition and appropriate treatment of IAH.

Limitation of the study

The measurements may have varied depending on whether if they were taken at end of inspiration or at the end of expiration which may have led to under estimation of the readings. Sessions were conducted to train the research assistants to correctly measure the IAP.

IAP measurements were between 6 h interval; hence we may have missed episodes of IAH between measurements.

At IAP measured omitted at 48 h if pt has no episode of IAH, pre-op and post-op up to 24 h. This was done for the concern of causing urinary tract infections in the patients, hence the reading 48 h was to be assumed as normal (but this was not analysed) hence our few numbers at 48 h.

Recommendations

Objective routine IAP measurements should be considered for all patients undergoing emergency laparotomy. Clinical protocols should be designed to guide the management of patients with IAH in the accidents and emergency surgery wards. Resources should also be channeled towards procurement of equipment required to monitor the IAP in these patients. More studies are needed to demonstrate proper guidelines on monitoring of IAP in patients undergoing emergency laparotomy.