Intra-abdominal hypertension among critically ill patients in an intensive care unit in Ghana

1 Introduction

Intra-abdominal hypertension (IAH) is increasingly recognised as a major factor contributing to morbidity and mortality among critically ill patients in the intensive care unit (ICU) (1, 2). Intra-abdominal pressure (IAP) must remain within a normal range to ensure optimal organ function. The capacity of the cavity to accommodate volume increases associated with diseases of intra-abdominal organs, or the rupture of hollow viscera or vessels, is constrained without a corresponding rise in IAP (3). The normal IAP is 5–7 mmHg in healthy individuals and approximately 10 mmHg in critically ill adults (4). IAH is defined as a sustained or repeated increase in IAP ≥12 mmHg. Abdominal compartment syndrome (ACS), the most severe manifestation of elevated IAP, arises when IAP exceeds 20 mmHg with new-onset organ failure. The World Society of the Abdominal Compartment Syndrome (WSACS) grades IAH from I to IV based on severity (4).

The prevalence of IAH is significantly high among ICU patients (1, 2). Studies have reported a pooled prevalence of 30%–70%, with IAH often occurring within the first 48 h of admission. This variation in reported IAH prevalence reflects differences in patient populations, underlying pathologies, and monitoring practices. Krohn's method of measuring IAP is the most widely used and utilises an indwelling urethral catheter connected to either a transducer or a saline manometer (5). It is preferred because it is relatively non-invasive, simple, and reproducible.

Historically, IAH was considered an issue primarily in patients undergoing abdominal surgery for acute pancreatitis, ileus, or hollow viscus perforation or in polytraumatised patients (6, 7). However, evidence indicates an increased occurrence in critically ill patients who receive mechanical ventilation; in non-surgical patients with sepsis, heart failure, renal failure, or an intra-abdominal infection; and in obese patients who receive large volumes of intravenous crystalloids during resuscitation (8, 9). Increased IAP, through direct mechanical effects, disrupts tissue perfusion, potentially resulting in circulatory alterations and organ dysfunction or failure.

A systematic review reported a prevalence of organ failure ranging from 6.5% to 38.1%, with the prevalence varying with ICU admission indication (10). The prevalence of organ failure was notably higher among patients with medical conditions and lowest in those admitted following scheduled surgery. The Sequential Organ Failure Assessment (SOFA), Acute Physiology and Chronic Health Evaluation (APACHE II), and Simplified Acute Physiology (SAPS II) assessment tools are used to evaluate patients and predict mortality based on physiological variables (11). Although the effectiveness of these instruments is similar, SOFA, as a predictive model for evaluating critically ill patients, is based on fewer, simpler factors, making it attractive for resource-limited environments (10–12). The duration of IAH is a significant independent predictor of other outcomes, such as duration of mechanical ventilation, mortality rate, and length of stay in the ICU (9, 13, 14).

Differences in patient characteristics across different ICU populations, along with institutional capacity and preparedness, impact the early recognition of IAH. Variation in risk factors underscores the need for a systematic evaluation of at-risk patients and standardised monitoring practices to facilitate timely intervention. Region-specific data on the prevalence and prognosis of IAH among critically ill patients will improve recognition of at-risk patients and contribute to the optimisation of monitoring and management. We therefore aimed to evaluate the prevalence, risk factors, and clinical outcomes of IAH in Ghana.

2 Materials and methods

2.1 Study design

A prospective study was conducted from 1 May to 30 November 2023 in a mixed population of critically ill patients in the ICU.

2.2 Setting

The study was conducted in the main ICU of Komfo Anokye Teaching Hospital (KATH), the largest public referral hospital in the northern part of Ghana. The hospital is situated in Kumasi, the capital of the Ashanti Region. KATH has a capacity of 1,250 beds, offering diagnostic and treatment services to approximately 300,000 patients annually. The main ICU, a level II ICU, is an eight-bed mixed surgical-medical intensive care unit with six regular beds and two isolation beds, with a surgical-medical patient ratio of approximately 7:3. Staffing includes 2 intensivists and 21 anaesthesia and intensive care specialists, comprising 4 consultant anaesthesiologists, 5 critical care fellows in training, and 12 critical care nurses of different cadres. The nurse-patient ratio is 1:1 during the day shift and 1:2 during the night shift. Patients are managed in collaboration with the primary specialty teams. Over the past 5 years, the average number of admissions to the intensive care unit has been between 100 and 150 per year.

2.3 Recruitment of study participants

Patients aged 16 years or older admitted to the ICU during the study period were enrolled consecutively (Figure 1). Patients with contraindications for urethral catheter placement or for measuring IAP, including traumatic pelvic trauma, bladder injury, pregnancy, or neurogenic bladder, and individuals who had undergone bladder-related surgery, were excluded.

2.4 Data collection

Data were collected by the principal investigator, with support from two ICU-trained intensivists working in the main ICU. A 2-day training programme was provided that focused on the content of the questionnaire, identifying subjects based on the inclusion/exclusion criteria, and obtaining consent. The research purpose and study procedure were clearly communicated to the patient or their next of kin in accordance with the standard consent protocol for ICU patients (15). Once recruited, participants’ demographic and baseline data were collected. This included age, sex, date of admission, patient category (surgical or medical), respiratory rate, oxygen saturation (SpO₂), blood pressure, and mode of ventilation. The participants’ current diagnoses, along with their previous medical and surgical history, were also recorded. The participants were then screened for IAH risk factors, and IAP measurement and SOFA score were documented. The participants’ demographic and clinical data were stripped of all identifiers.

2.5 Data collection tools

Each trained investigator was assigned to independently measure SOFA and IAP and was blinded to the other investigators’ scores. Intravesical measurement of IAP was conducted via a latex Foley urethral catheter, according to the modified Kron's technique (5). A pressure system was set up using a pressure transducer connected to a 500 mL normal saline drip and was then connected to the patient's monitor. The transducer was connected to a three-way stopcock on the urethral catheter through a sample line. The setup is similar to invasive blood pressure and central venous pressure systems, except that the 500-mL saline bag is not pressurised and the infusion is not heparinised. Before measurement, with the patient in the supine position, the transducer was placed at the level of the iliac crest and zeroed to ensure accurate measurements. Before each measurement, the urinary bladder was drained to ensure it was empty, the urine drainage system was clamped, and 25 mL of saline was then instilled into the bladder.

The intra-abdominal pressure reading was recorded 30–60 s after saline instillation, allowing the detrusor muscles to relax. The pressure was also recorded at the end of expiration with the participant in a completely supine position. IAP was assessed upon admission and subsequently at 6-h intervals for the first 48 h or until diagnosis of intra-abdominal hypertension, patient discharge, or death. Two IAP measurements were taken at each timepoint, and the average was recorded as the IAP for that timepoint. Organ dysfunction was assessed using the SOFA score, which evaluated respiratory, cardiovascular, renal, coagulation, liver, and neurological function. The SOFA score was assessed daily for 7 days following ICU admission. Mean SOFA scores were compared between patients with and without IAH at each study timepoint. All participants were followed up for 30 days. ICU length of stay and ventilator-free days were also assessed unless death or hospital discharge occurred.

A diagnosis of IAH was established in accordance with the WSACS criteria. IAH was graded as follows (4): ACS was defined as a sustained IAP greater than 20 mmHg associated with new organ dysfunction or failure. The daily median SOFA score was compared across groups, with a higher score indicating greater organ dysfunction. The primary outcome was the prevalence of IAH within 48 h of ICU admission. The secondary outcome measures were severity of organ dysfunction or failure (SOFA score), ventilation-free days, ICU length of stay, and overall mortality during the follow-up period.

• Grade I (12–15 mmHg)
• Grade II (16–20 mmHg)
• Grade III (21–25 mmHg)
• Grade IV (> 25mmHg)

2.6 Sample size

Based on an annual average of 100–150 admissions and a 10% margin of error, a sample size of 88 participants was deemed adequate for the study after using Cochran’s correction formula (16).

2.7 Statistical analysis

Analyses were conducted using Stata® 17.0 (StataCorp). The clinical data were summarised using tables, proportions, and means with standard deviations or medians with interquartile ranges (IQRs). Prevalence was defined as the percentage of patients with IAH among those requiring critical care. IAP was measured within an hour of ICU admission and repeated every 6 h for 48 h. Logistic regression was used to determine the associations between the risk factors and IAH. P ≤ 0.05 was considered statistically significant.

2.8 Ethics

The study was approved by the Research and Development Unit of KATH and the KATH Institutional Review Board (KATH IRB/AP/064/23).

3 Results

3.1 Baseline characteristics

The study included 89 participants, with a median age of 43 years (IQR 29–58), as presented in Table 1. Among the participants, 47 (55.1%) were female. A majority (28, 31.5%) of the patients had malignancy as an underlying condition. Furthermore, 58 individuals (77.6%) were admitted to the ICU on account of post-operative critical care or circulatory failure. Table 2 presents the number of patients who developed IAH.

Table 1. Baseline characteristics.

Causes of subdural haematoma: secondary cerebrovascular accident and trauma.

Causes of life-threatening infection: pneumonia, 1; cerebral malaria, 1; cerebral abscess, 1; and urosepsis, 1.

Others: hyperacute transplant rejection reaction, 1; thrombolysis/monitoring, 1; seizure control, 2; and cardiogenic shock, 1.

Causes of diminished abdominal wall compliance: morbid obesity, 4; abdominal surgery, 9; and mechanical ventilation, 23. Causes of increased intraluminal content: ileus, 1; abdominal distension, 9. Causes of increased intra-abdominal content: acute pancreatitis, 1; intra-abdominal infection, 3. Causes of capillary leak/fluid resuscitation: sepsis, 10; acidosis, 3; massive fluid resuscitation, 10; and positive fluid balance, 67.

Table 2. Prevalence and grading of intra-abdominal hypertension cases.

Causes of subdural haematoma: secondary cerebrovascular accident and trauma.

Causes of life-threatening infection: pneumonia, 1; cerebral malaria, 1; cerebral abscess, 1; and urosepsis, 1.

Grade III: abdominal compartment syndrome.

Others: hyperacute transplant rejection reaction, 1; thrombolysis/monitoring, 1; seizure control, 2; and cardiogenic shock, 1.

Nearly all the patients (88, 98.9%) had identifiable risk factors. Moreover, 31 (39.7%), 22 (28.2%), and 25 (32.1%) patients had 1, 2, and 3 or more concurrent risk factors, respectively. The most prevalent risk factor, present in 69 patients (78.4%), was capillary leak or fluid resuscitation, which was predominantly attributed to a positive fluid balance (n = 67, 75.3%). Diminished abdominal wall compliance was the second most common risk factor, identified in 48 patients (54.6%), and was mostly (23, 26.1%) due to mechanical ventilation.

The median IAP was higher at admission than at subsequent timepoints (Figure 2). Figure 3 shows the mode of ventilation for the critically ill patients. The majority of the study participants received synchronised intermittent mandatory ventilation (SIMV) either at admission or at some point during the first 48 h of their ICU stay. The requirement for SIMV decreased over the course of the ICU stay.

3.2 Prevalence and grade of intra-abdominal hypertension

In total, 42 patients (47.2%) had intra-abdominal hypertension (IAH), with Grade I IAH being the most common (n = 27, 64.3%). Two patients (4.7%) had Grade III IAH (IAP 21–25 mmHg). The majority of IAH cases (n = 39, 92.9%) occurred within the first 24 h of ICU admission.

3.3 Predictors of intra-abdominal hypertension

The presence of malignancy (OR 5.28, 95% CI 1.87–14.89, p = 0.002), having a higher number of risk factors (OR 9.89, 95% CI 3.67–26.64, p < 0.001), and post-operative care (OR 3.49, 95% CI 1.42–8.55, p = 0.006) were significantly associated with IAH in the univariate analysis. Circulatory failure was inversely associated with IAH (OR 0.35, 95% CI 0.12–0.98, p = 0.045). However, in the multivariate analysis, the occurrence of IAH in critically ill patients increased by more than 11-fold with a higher number of risk factors, after adjustment for age (OR 11.37, 95% CI 3.84–33.66, p < 0.001) (Table 3).

Table 3. Predictors of intra-abdominal hypertension.

CI, confidence interval.

3.4 Organ dysfunction, ventilator-free days, ICU stay length, overall mortality, and intra-abdominal hypertension

Table 4 compares the mean SOFA scores, ventilation-free days, length of stay, and mortality rate of the patients with and without IAH. The mean SOFA scores for the first 7 days of admission were significantly higher among the patients with IAH compared with those with normal IAP (e.g., Day 1: 8.42 vs. 6.25, p = 0.01; Day 7: 6.09 vs. 3.27, p = 0.02). Patients with normal IAP had significantly more ventilator-free days than those with IAH (21.3 vs. 13.5 days, p < 0.001). The duration of ICU stay was comparable, with an average of 9.19 days versus 7.23 days (p = 0.70). More than 40% of patients with IAH died, which was statistically significantly different to those with normal IAP (19 vs. 9, p < 0.01).

Table 4. Organ dysfunction, length of stay, mortality, and intra-abdominal hypertension.

SD, standard deviation.

4 Discussion

This prospective study demonstrated that IAH is common among critically ill patients admitted to a mixed ICU in Ghana. To our knowledge, it is one of the first prospective studies from West Africa to utilise serial IAP monitoring and standardised WSACS definitions to evaluate the epidemiology and clinical significance of IAH in a resource-limited critical care setting.

The observed prevalence of 47.2% confirms that IAH represents a substantial burden among critically ill patients in sub-Saharan Africa (2, 17). Although lower than figures reported in Kenya and Egypt, the prevalence remains within the range reported internationally, supporting the view that IAH is a common but under-recognised complication among clinically ill ICU patients. Our findings may reflect the fact that a substantial number of patients in this cohort were admitted primarily for routine postoperative critical care. In contrast to reports from other studies, in which IAH frequently developed after the first day of ICU stay, the majority of IAH cases in our cohort were diagnosed at or shortly after admission (1, 18). This observed pattern may reflect delayed presentation or a higher percentage of patients with advanced physiological derangement before ICU admission. Patients with underlying diagnoses of hollow viscus perforation, acute haemorrhagic pancreatitis, and cerebral malaria are often very sick, and elevated IAP may already be established at the time of critical care initiation. ACS was diagnosed in 4.8% of the patients with elevated IAP, a rate comparable to 3.6%–5.0% reported in previous studies. Higher rates have been documented among patients with sepsis, major trauma, and complex surgical emergencies. The observed rate in our cohort reflects the fact that a substantial number of the patients were admitted primarily for routine postoperative critical care.

The prevalence of IAH varies, reflecting differences in patient demographics, underlying conditions, and monitoring practices. The majority of the IAH cases were of secondary origin, similar to an eastern African study; however, our study included a relatively higher proportion of women. The majority of the participants had IAH upon admission or developed it within 6 h of ICU admission.

An important finding of this study was the strong association between cumulative IAH risk factors and subsequent development of IAH. Patients with more predefined risk factors had more than 10-fold increased odds of developing IAH. This finding supports the use of structured risk assessment tools to identify patients who may benefit most from targeted IAP monitoring. The majority of centres identify mechanical ventilation and a positive fluid balance as major risk factors, both of which were evident in our mixed ICU population (19, 20). Mehrdad et al. reported a significant relationship between ventilation mode and IAP, demonstrating that IAP is affected by SIMV (21). Daily spontaneous awakening and breathing trials (SBTs) are effective for evaluating readiness for extubation, potentially reducing ventilation duration and minimising complications associated with elevated airway pressure (22). Judicious use of sedatives can improve the accuracy of respiratory drive assessment, hasten the return of spontaneous respiration, and support successful SBTs (23). Strategies to optimise fluid balance and prevent fluid overload indirectly facilitate early weaning by reducing abdominal oedema and enhancing diaphragmatic mechanics (24). In our population, conservative fluid strategies, such as monitoring stroke volume variation, cardiac output, lactate levels, and urine output and tailoring fluid delivery to actual physiological needs, are of paramount importance. Secondly, the use of vasopressors in the absence of fluid responsiveness is crucial to prevent unnecessary interstitial accumulation that could lead to IAH. IAH has been associated with adverse outcomes in several studies (4, 25). The overall effect of IAH on patient outcomes may be a function of its severity. Traditionally, a higher IAH grade is associated with higher mortality, and vice versa, which does not align with the findings in this cohort, where the cases were mostly Grades I and II. Elevation in IAP due to direct mechanical effects disrupts tissue perfusion, potentially leading to circulatory alterations and organ dysfunction or failure (9, 26). The prognosis of IAH deteriorates with an increasing number of organ failures per patient. Patients who developed IAH demonstrated consistently higher SOFA scores throughout the observation period. However, because the SOFA scores were already elevated early after ICU admission, it remains unclear whether IAH directly contributed to worsening organ dysfunction or whether it primarily reflected greater underlying illness severity. Future studies incorporating time-dependent analyses are required to clarify this relationship.

The patients with IAH experienced significantly higher mortality than those without IAH. While this observation is consistent with previous reports (4, 25), our study was not designed to establish a causal relationship between IAH and mortality. The higher mortality rate observed among patients with IAH may partly reflect greater baseline physiological derangement, as evidenced by higher SOFA scores throughout ICU admission. Thus, it is important to provide holistic care for the underlying disease when treating any patient.

Several limitations should be acknowledged. A single-centre design and relatively small sample size may limit external validity. As IAP was measured only in the first 48 h, this may miss late-onset IAH, although the majority of the adverse clinical outcomes of IAH were predominantly diagnosed within the first 24 h. The predominance of neurosurgical postoperative patients may limit comparability to other mixed medical-surgical units. Residual confounders in IAP measurement cannot be excluded, as the patients who developed IAH also had higher disease severity scores. The sample size was primarily calculated to estimate prevalence and may not have been adequately powered for a multivariable analysis of predictors.

Despite these limitations, this study challenges the assumption that IAH is predominantly a surgical or post-laparotomy phenomenon, as the majority of the IAH cases occurred in patients with non-abdominal critical illnesses.

5 Conclusion

Intra-abdominal hypertension is a common and clinically significant condition in ICU patients in Ghana. There is a more than 10-fold increase in IAH risk in patients with a higher number of predisposing risk factors, independent of age or admission diagnosis. Targeted monitoring of IAP among critically ill patients with multiple recognised risk factors may facilitate earlier identification of IAH and prompt intervention. Further multicentre studies are required to determine whether routine IAP surveillance improves patient-centred outcomes and should be incorporated into standard ICU practice.

Correction Note

This article has been corrected with minor changes. These changes do not impact the scientific content of the article.

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Footnotes

Edited by: Alparslan Turan, Cleveland Clinic, United States

Reviewed by: Theodoros Aslanidis, Agios Pavlos General Hospital, Greece

Filip Konecny, McMaster University, Canada