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
Independent variables
Patient’s age (in complete years), gender, weight (in kilograms), height (in meters), diagnosis, duration of surgery (in minutes).
Dependent variables
Renal dysfunction(creatinine, urea and urine output), respiratory dysfunction(Respiratory rate, SpO2, cardiovascular dysfunction(MAP, Heart rate), central nervous system dysfunction(GCS), intra-abdominal pressure duration of hospital stay, morbidity (burst abdomen, relaparotomy, wound dehiscence and wound sepsis), and mortality.
Interpretation of findings
Grading of intra-abdominal hypertension for adults
-
1.
Grade I: 12–15 mmHg;
-
2.
Grade II: 16–20 mmHg;
-
3.
Grade III: 21–25 mmHg; and
-
4.
Grade IV: >25 mm Hg
Grading of intra-abdominal hypertension for paediatrics
-
1.
Grade I: 10–12 mmHg,
-
2.
Grade II: 13–15 mmHg,
-
3.
Grade III: 16–19 mmHg; and
-
4.
Grade IV: ≥ 20 mmHg
Patients (adults) were considered to have ACS when they had IAH > 25 mmHg with evidence of a newly developed organ dysfunction. In Paediatric group, ACS was sustained IAP of greater than 10 mmHg associated with new organ dysfunction/failure. Intervention was left for the attending surgeon to decide.
Organ system derangement
Cardiovascular system
-
1.
MAP < 60 mmHg
-
2.
Heart rate > 100/min
-
3.
Both of the above
Respiratory system
-
1.
Respiratory rate > 20/min or
-
2.
SpO2 < 90 % or
-
3.
Patient in need of ventilatory support or
-
4.
Any two or all of the above
Renal system
-
1.
Serum creatinine > 106 umol/L or
-
2.
Blood urea > 6.4 umol/L or
-
3.
Urine output < 25 ml/h or
-
4.
Any two or all of the above
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
Data entry
Data was double entered into Epi Data version 3.1 with range, consistency and validity checks embedded to ensure accuracy of data. The data was stored on a computer hard drive that is password protected to ensure confidentiality and backed up on separate external hard drives kept in separate locations.
Data analysis
Univariate analysis was performed for baseline factors of the study. For continuous variables such as age; means (standard deviations) and median (interquartile range) if data was skewed, were reported. For categorical variables, proportions and percentages were reported and findings displayed in frequency distribution tables.
Multivariate analysis using the multinomial logistic regression at 95 % confidence interval and P-value <0.05 statistical significance, organ dysfunction, morbidity rate, mortality rate were considered as outcomes of IAH. Results were reported in relative risk ratios and p-value.
Quality control
The recruited research assistants were trained on the use of the data collection tool, how to do the different measurements and patient approach. The data collection tool was pretested. We cross-checked the data daily to ensure completeness with double data entry. An accurate history and physical examination of the patients was done.
Measurements of the IAP were done three times 3 min apart and the average was recorded and to increase accuracy. Standardized machines were used to measure other parameters such as SpO2, MAP, and PR etc.
Data cleaning and entry was done occasionally. There was periodic data evaluation. All questionnaires were safely stored to enable reference in case of data loss.
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.