The use of point-of-care ultrasound to guide clinical management in intra-abdominal hypertension

Abstract

Introduction

The Abdominal Compartment Society (WSACS) developed a medical management algorithm with a stepwise approach to keep intra-abdominal pressure (IAP) ≤ 15 mm Hg. The role of point-of-care ultrasound (POCUS) as a bedside modality in the critical care patients is not well studied in relation to the intra-abdominal hypertension (IAH) management algorithm.

Aim

To test the role of point-of-care ultrasound (POCUS) in the medical management of patients with intra-abdominal hypertension (IAH).

Method

We conducted a prospective observational study. Those who met the inclusion criteria were assigned to undergo POCUS and small bowel ultrasound as adjuvant tools in their IAH management.

Results

A total of 22 patients met the inclusion criteria and were included in the study. The mean age of the study participants was 65 ± 22.6 years, 61% were men, and the most frequent admission diagnoses were hepatic encephalopathy and massive ascites (five cases). Ultrasound and abdominal X-rays were comparable in confirming correct NGT position, but the ultrasound was superior in determining the gastric content (fluid vs. solid) and diagnoses of gastric paresis in two cases. Small bowel obstruction was present in four patients and confirmed with abdominal CT; two of the patients underwent surgical intervention for mesenteric vessel occlusion and transmesenteric internal hernia. Enema treatment was found to empty the bowel incompletely 72%, 56%, and 42% of the time on days 1, 2, and 3, respectively. Four patients with cirrhosis admitted with upper gastrointestinal bleeding and hepatic encephalopathy (out of a total of 8) were found to have large amounts of ascites, and US-guided paracentesis was performed.

Conclusion

POCUS can be used in the nonoperative management of IAH. It is an important tool in the diagnosis and treatment of patients with IAH.

Electronic supplementary material

The online version of this article (10.1007/s40477-020-00546-8) contains supplementary material, which is available to authorized users.

Strengths and limitations of this study

• This a prospective study using bowel ultrasound as an adjunct tool in critically ill patients

• POCUS can facilitate and guide the medical management of patients with IAH in ICU

• POCUS can be applied early in the WSACS IAH/ACS Medical Management Algorithm

• Being a single-center study and including small numbers of patients are the main limitations of the study

Introduction

Intra-abdominal hypertension (IAH) is a well-documented cause of morbidity and mortality in the critically ill and can affect almost every organ system (1). The diagnosis and management of IAH has evolved, and the importance of comprehensive strategies to reduce intra-abdominal pressure (IAP) has been recognized. Starting from awareness of the risk factors that predict the development of IAH, the appropriate measurement of IAP, and the current resuscitation options for managing this highly morbid syndrome, the Abdominal Compartment Society (WSACS) developed a medical management algorithm. The algorithm uses a stepwise approach according to the evolution of the intra-abdominal pressure and aims to keep IAP ≤ 15 mm Hg (2). In the updated 2013 WACS guidelines, the medical management of IAH and ACS is divided into five categories: (1) evacuation of intraluminal contents; (2) evacuation of intraluminal occupying lesions or extraluminal (intra-abdominal) contents; (3) improvement of abdominal wall compliance; (4) optimization of fluid administration; and (5) optimization of systemic and regional perfusion.

Point-of-care ultrasound as a bedside modality in critical care patients could be used as an adjuvant point-of-care tool during IAH management.

Methods

Study population

This was a prospective observational study. All patients admitted between the 1^st of May 2019 and the end of December 2019 with recognized risk factors for IAH/ACS were enrolled and treated according to the 2013 WSACS guidelines [2]. The study protocol was approved by the Ethical Committee of the Ahmadi hospital; informed consent was obtained from every patient or from his or her next of kin.

All patients had IAP routinely measured in the supine position by urinary bladder pressure after instilling 25 ccs 0.9% NSS using preassembled kit devices (AbViser urinary catheter). To record IAP, we allowed the system to equilibrate and then note the pressure reading on the monitor at the end of expiration. The IAP reading lasts for 1–3 min, and the valve will then automatically open and the pressure reading will decrease to zero. Patients were excluded from analysis if any of the following occurred: death within 72 h, extubation or discharge from ICU within 72 h of ICU admission, or initial normal IAP (< 12 mm Hg). Demographic data, initial vital signs, admission IAP, admission abdominal perfusion pressure (APP), and clinical data were recorded for each patient. The inclusion criteria were that patients had to be the following: (1) ICU patients/minimum ICU stay of 3 days; (2) 18 years of age or older; (3) intubated and mechanically ventilated with adequate sedation (Richmond Agitation-Sedation Scale −4 or − 5); (4) able to lie in a supine position for all measurements; and (5) not exhibiting abdominal respiratory muscle activity.

A trained intensivist performed POCUS for 3 consecutive days after admission (Fig. 2).

Fig. 2.

Modified WSACS IAH/ ACS Medical Management Algorithm with the role of POCUS. Added abdominal ultrasound box

When the evacuation of intraluminal contents was indicated,

Ultrasound was used to confirm NGT position and compared with X-ray imaging for patients requiring a nasogastric tube (NGT) for intra-abdominal decompression (WSACS algorithm step 1).

Stomach and bowel US was performed daily to evaluate hollow viscous content and fluid-filled small bowel loops, dilated to > 2.5–3 cm (Fig. 2). In some cases, there were increased intestinal contents (fluid and echogenic material within the lumen of the bowel) (image 1) or increased peristalsis of the dilated segment, as evidenced by the to-and-fro or whirling motion of the bowel contents (WSACS algorithm step 2) and/or colonoscopy decompression (WSACS algorithm step 3).

When the evacuation of intra-abdominal content was indicated,

Abdominal POCUS was performed daily either to evaluate the presence of abdominal free fluid or to help percutaneous drainage (WSACS algorithm step 2).

POCUS method

Daily POCUS was performed in all patients to evaluate the stomach and bowel contents (Fig. 1).

Fig. 1.

Ultrasound scan of the abdomen in intra-abdominal hypertension

To confirm NGT position, we used a 4-point ultrasonography protocol: (1) ultrasound from either the right or left side of the patient’s neck to visualize the esophagus; (2) ultrasound of epigastrium to confirm the passage through the esophagogastric junction; (3) confirmation of the positioning in the antrum; and (4) sonography of the fundus. Finally, gastric placement of the nasogastric feeding tube was confirmed with thorax radiograph (3).

For stomach views and patients requiring NGT, images were obtained in 2D-mode, with the transducer positioned at the level of the epigastrium and left hypochondrium. The convex transducer was placed in a transverse plane, resulting in visualization of the antrum and body of the stomach. At this moment, the insertion of the NGT was commenced, and the stomach content was observed. Once the NGT was visible in the hollow viscous, a 100-mL flush of agitated saline was delivered to confirm the correct positioning.

For small and large bowel visualization, the transducer was placed at the periumbilical level and on both medium–low abdominal quadrants to observe both the right and left colon.

To screen for intra-abdominal free fluid, the POCUS landmarks were the right upper quadrant, left upper quadrant, and hypogastrium (Fig. 1), either with a longitudinal or transverse probe position. The various probe positions to enable the different POCUS windows are shown in Fig. 1. Paracentesis was performed via the insertion of a sterile percutaneous size 6 French pigtail tube with real-time direct ultrasound guidance.

Statistical analysis

The two-tailed statistical tests were performed with the Statistical Package for the Social Sciences (IBM SPSS 19). Student’s t-test was used to assess the continuous variables in the case of a normal distribution, and the Mann–Whitney test was used for non-normally distributed variables. Fisher’s exact test was used for categorical data. All p-values were two-tailed, and p < 0.05 was considered statistically significant. A descriptive statistical analysis was performed to summarize patient characteristics and study measurements.

Results

A total of 43 patients were included in the study. Twenty-one patients were excluded due to one or more of the following reasons: death, extubating or discharge from ICU before the third day of admission, or normal IAP.

The mean age of the study participants was 65 ± 22.6 years old, and 60% were men with one or more associated comorbidities, such as hypertension, diabetes, or dyslipidemia. The most frequent cause of IAH was ileus secondary to sepsis and hepatic encephalopathy with massive ascites (Table 1). Table 2 shows the data from the first three consecutive ICU days.

Table 1.

Patient characteristics, clinical data, and cause of IAH

Participant characteristics
Mean Age (years))	65 (39–71
Gender (Male)	13 (60%)
BMI (kg m−2) 27	BMI (kg m−2) 27
Clinical data
Mean SBP (mm Hg)	108.5 (83–134)
Mean HR (beats min-1)	94 (60–128)
IMV (%)	22(100%)
Mean admission IAP (mm Hg)	18 (12–34)
Mean admission APP (mm Hg)	85
Vasopressor use (n %)	18 (80%)
Diagnosis of IAH
Bowell obstruction (%)	3 (13%)
Mesenteric vessel occlusion (%)	1 (4%)
Gastrointestinal bleeding (%)	3(13%)
Clostridium colitis (%)	2 (9%)
Ascites—liver cirrhosis	4(18%)
Pancreatitis	2 (9%)
Ileus secondary to sepsis	6 (27%)
Drug-induced hemoperitoneum	1(4%)

SBP systolic blood pressure, BMI body mass index, HR heart rate, IMV invasive mechanical ventilation, IAP intraabdominal pressure, APP abdominal perfusion pressure, IAH intraabdominal hypertension

Table 2.

Data from three consecutive days on IAH treatment

	Day 1	Day2	Day3
Mean IAP (mm Hg)	17 (12–22)	14.6 (10–20)	13 (8–20)
Mean APP (mm Hg)	85.5	91.5	107
Mean SBP (mm Hg)	108.5 (83–134)	109 (90–128)	122 (101–143)
Renal replacement therapy	6	4	4
NGT tube need (n)	22	19	16
US gastric content observed (n)	22	22	22
Positive bowel content (before enema) viewed on US (n)	22	22	22
Positive bowel content (after enema) viewed on US (n)	16	10	6
Bowel movements observed in the US (n)	10	12	16
Bowel diameter > 3 cm (n)	14	8	6
Abnormal bowel content movement (n)	6	4	3
Number of patients with free abdominal fluid seen on US (n)	8	2	2
Positive moderate to a large amount of free the abdominal fluid is seen on US (n)	6	0	0
US-guided paracentesis (n)	4	0	0
Operation	2	0	0

US ultrasound, SBP systolic blood pressure, BMI body mass index, HR heart rate, IMV invasive mechanical ventilation, IAP intraabdominal pressure, APP abdominal perfusion pressure, IAH intraabdominal hypertension

Laparotomy for elevated IAP was not necessary for any of the patients due to full recovery after clinical management.

The mean IAP on admission was 17 ± 15.5 mm Hg. Two patients required surgery for mesenteric vessel occlusion and small bowel obstruction suspected by small bowel ultrasound.

All patients required an NGT for the first 24 h following admission, as confirmed by ultrasound of the stomach and agitated saline. Ultrasound was comparable with abdominal X-ray but superior in determining gastric contents (fluid vs. solid) and confirming gastroparesis. Furthermore, POCUS allowed a bedside determination of correct NGT positioning into the stomach (antrum) without exposure to radiation. There was 100% accuracy when using the US to determine NGT placement and positioning, with no false negatives or false positives observed.

The second step in the WSACS guidelines addresses intraluminal evacuation through the administration of enemas. This strategy was followed in all patients in whom the IAP remained high (above 20 mm Hg) on the second measurement (6 h after admission). The US proved useful in many ways. First, the POCUS allowed assessment of bowel activity (movements) and detection of pathological movement, e.g., to-and-fro (detected in 6 patients, 2 of whom underwent operation). Second, it allowed the identification of large bowel contents (right and left colon). Third, it allowed measurement of the diameter of the small bowel, which should normally be less than 3 cm. Small bowel obstruction is suspected when the small bowel measures more than 3.0 cm over a length of more than 10 cm and contains increased content. Fourth, POCUS allowed the identification of patients who may benefit from continued enema treatment to lower IAP.

These aspects were considered important, as most patients were medical. For example, small bowel obstruction, along with mesenteric vessel occlusion, was present in two patients, confirmed with abdominal CT, and operated upon. Enema treatment was found to empty the bowel incompletely in 72%, 56%, and 42% of instances on days 1, 2, and 3, respectively. Colonoscopy decompression was not needed in any of our patients.

During the second stage of the WSACS medical management algorithm, the US was a useful adjuvant tool for diagnosing moderate-to-large amounts of free intra-abdominal fluid. Special attention was given to cirrhotic patients who were admitted with upper gastrointestinal bleeding.

Four patients in this group (out of a total of 8) were found to have large amounts of ascites, and US-guided paracentesis was performed (Fig. 2). The average amount of ascites removed was 3400 ± 1.6 mL, and removal resulted in a significant decrease in the average IAP, which dropped from 18 ± 4.1 mm Hg to 13 ± 2.0 mm Hg in all four patients.

Discussion

Intra-abdominal pressure should be measured regularly in critically ill patients, every 4 to 6 h according to the guidelines for high-risk patients [4]. An early IAH diagnosis can lead to a shorter ICU stay, shorter ventilation, lower incidence of ventilator-associated pneumonia, and higher survival in IAH/ACS [5, 6].

POCUS is widely used in the field of critical care medicine [7], and bowel ultrasound is an important diagnostic tool in reaching diagnosis rapidly in abdominal emergencies. Bedside US, performed by an intensivist, has good diagnostic accuracy in small bowel obstruction (SBO). [8, 9]. In this study, we had two patients with small bowel obstruction, and two of them were managed surgically. Adding bowel and abdominal ultrasound at the start of the algorithm in managing patients admitted to the medical ICU with IAH will decrease the incidence of missing abdominal issues requiring surgery. A fluid-filled small bowel lumen > 2.5 cm is consistent with the diagnosis of SBO (10). The presence of dilated small bowel loops (> 25 mm in the jejunum or > 15 mm in the ileum) was the most sensitive (94%) and specific (94%) sonographic finding for SBO in the hands of emergency physicians (10). Other signs that should be screened for are increased intestinal contents (fluid and echogenic material within the lumen of the bowel) and increased peristalsis of the dilated segment, as evidenced by the to-and-fro or whirling motion of the bowel contents [11]. Visualization of small and large bowel obstruction with ultrasound is as good as computed tomography and superior to plain X-rays, but computed tomography is superior to ultrasound in terms of the etiologic definition for both small bowel obstruction and large bowel obstruction [12].

We also focused on the first two stages of the WSACS algorithm and applied ultrasound for specific interventions at each stage (escalating from 1 to 4). We used POCUS as an adjuvant tool for IAH management and focused our efforts on steps 1 to 3 of stage one (“evacuate intraluminal content”) and steps 1 and 2 of stage two (“evacuate intraluminal occupying lesions or extra-luminal content”).

Decompression of intraluminal content is recommended in patients with grade I IAP, starting with the insertion of NGT. The NGT was passed under direct US guidance with the probe on the epigastrium, allowing for direct visualization of the tip of the NGT as it was directed to its ideal position close to the pylorus, and confirmed with 100 ml agitated saline with 10 ml air (Fig. 2). A 100% accuracy rate was observed when using the US to determine NGT placement and positioning. POCUS was used to assess gastric contents after using the prokinetics and on the third ICU day or before removing the NGT.

In the first two steps of the second stage of the WSACS medical management algorithm, ultrasound identified moderate-to-large amounts of free intra-abdominal fluid in cases of cirrhotic patients with ascites requiring ultrasound-guided paracentesis and drug-induced hemoperitoneum, and it was also useful in patients with severe acute pancreatitis. All enrolled patients demonstrated reductions in IAP, and subsequently better clinical performance, during their first 3 days of admission.

The small number of patients, the observational design of the study, and the fact that this work is a single-center study are the main limitations of the study.

Conclusion

POCUS can be used in the non-operative management of IAH and ACS. It is an important tool in the diagnosis and treatment of patients with IAH.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Author contributions

ZIB wrote the article, OSM shared in the discussion and with MM, REE and TMZ shared in collecting the data and revision of the manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article. The research was performed as part of the employment of the authors in Kuwait Oil Company.

Data availability statement

Data are available upon reasonable request. The data that support the findings of this study are available from the corresponding author upon reasonable request.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Disclaimers

The author(s) declared no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Patient and public involvement

Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research. Patient consent for publication Not required.