The significance of intra-abdominal pressure in neurosurgery and neurological diseases: a narrative review and a conceptual proposal

Abstract

Intra-abdominal pressure (IAP) is a physiological parameter that has gained considerable attention during the last few decades. The incidence of complications arising from increased IAP, known as intra-abdominal hypertension (IAH) or abdominal compartment syndrome in critically ill patients, is high and its impact is significant. The effects of IAP in neurological conditions and during surgical procedures are largely unexplored. IAP also appears to be relevant during neurosurgical procedures (spine and brain) in the prone position, and in selected cases, IAH may affect cerebrospinal fluid drainage after a ventriculoperitoneal shunt operation. Furthermore, raised IAP is one of the contributors to intracranial hypertension in patients with morbid obesity. In traumatic brain injury, case reports described how abdominal decompression lowers intracerebral pressure. The anatomical substrate for transmission of the IAP to the brain and venous system of the spine is the extradural neural axis compartment; the first reports of this phenomenon can be found in anatomical studies of the sixteenth century. In this review, we summarize the available knowledge on how IAP impacts the cerebrospinal venous system and the jugular venous system via two pathways, and we discuss the implications for neurosurgical procedures as well as the relevance of IAH in neurological disorders.

Intracranial Hypertension and Intra-abdominal Pressure. Is it Worth Measuring?

“…Mechanisms proposed to explain this change include reduced blood flow to the lumbar venous plexus (leading to increased pressure in the cerebrospinal fluid [CSF]), increased pressure of carbon dioxide (PaCO2), and reduced cerebral venous return by the jugular system. [12][13][14] This hypothesis meets and underlies the Monro-Kellie doctrine, in which states that the intracranial volume is equal to the volume of cerebral blood (3-10%) plus the volume of CSF (8-12%) plus the volume of brain tissue, which consists of more than 80% water. While the total intracranial volume remains identical, the ICP remains constant.…”

“…Thus, whenever there is an increase in IAP, there will be an increase in intrathoracic pressure, which reduces cerebral venous return through the jugular system, leading to an increase in cerebral blood volume and intracranial hypertension. 8,11,12 In a study conducted by Joseph et al, they have monitored parameters of patients (n ¼ 29) with head trauma and sustained increase in ICP, even with surgical (decompressive craniectomy) and pharmacological (barbiturates) management. In their study, these patients were evaluated before and after performing decompression laparotomy, resulting in the data shown in ►Table 1.…”

A Clinician’s Guide to Management of Intra-abdominal Hypertension and Abdominal Compartment Syndrome in Critically Ill Patients

“…Other conditions associated with "physiologically" increased IAP include pregnancy [18] and liver cirrhosis with ascites [19]. Although this chronic IAP elevation may contribute to chronic forms of organ failure, including chronic kidney failure in patients with congestive heart disease and obesity [20] or pseudotumor cerebri in patients with obesity [21], slight increases from a higher starting value may have limited implications in critically ill patients. As such, an IAP of 16 mmHg may be insignificant if the baseline value was 13 mmHg, where it may cause organ injury if the baseline value was 6 mmHg.…”

Clinical Anatomy of the Extradural Neural Axis Compartment: A Literature Review

“…1,2,[4][5][6][7]10,16 A fatty matrix and small valveless venous plexuses are the characteristic and major components of the EDNAC. 1,2,[4][5][6][8][9][10][11][12][13] Therefore, except for those in the skull base, most intracranial dural sinuses (e.g., the superior and inferior sagittal, straight, transverse, and sigmoid sinuses) reside in the interperiosteodural space but might not be in the EDNAC, because they are not imbedded in a fatty matrix. 17,18 The methods used by investigators to investigate aspects of the EDNAC have included anatomical microdissection, vascular injections and/or casting, epoxy sheet plastination, histological examination, and even electron microscopy.…”

“…7 Contained within this fatty matrix are plexuses of small valveless, epidural veins, allowing bidirectional flow of blood. 1,2,[4][5][6][8][9][10][11][12][13] This epidural adipovenous tissue is irregularly distributed and varies in amount throughout the length of the EDNAC. In certain locations, the EDNAC also transmits nerves, in addition to arteries and larger veins, before they continue on their extracranial or extraspinal course.…”