Intraabdominal pressure effects on the brain
Interestingly, intra-abdominal hypertension impacts intra-cranial pressure.[1] In fact, IAH is and independent risk factor for secondary brain injury after traumatic brain injury.[2] The physiology is fairly straight forward: As intra-abdominal pressure goes up, it pushes up the diaphragms, reducing intra-thoracic volume and causing elevated intrathoracic pressure. Elevated intra-thoracic pressure results in elevated central venous pressure and subsequent elevated internal jugular venous pressure. The result is a functional obstruction of cerebral venous outflow, resulting in increases in intra-cranial pressure and reduction in cerebral perfusion pressure.[3, 4] Citerio et al graphically demonstrated the direct correlation between IAH and ICP in a clinical setting.[3] They found that artificially induced IAP elevation led to immediate (in seconds) and significant increases in ICP, internal jugular pressure and central venous pressure (See figure).
Figure: Effect of IAP elevation on ICP and CVP
Figure: This figure from Citerio el al demonstrates the direct correlation between IAP and multiple other pressure measurements.[3] As demonstrated in the graph, IAP elevation leads to immediate (in seconds) and significant increases in ICP, IJP and CVP due to direct transmission of the IAP into the thorax, the central veins and the jugular veins. The result is venous outflow obstruction from the brain and concomitant elevations of ICP.
Marinis conducted an animal trial to assess the impact of elevated IAP on CNS perfusion (ICP, CPP, lactate and IL-6).[11] They found that an IAP of 20 mm Hg resulted in a significant increase in ICP with a resulting decrease in CPP and rises in measurable CSF lactate and interleukin-6 - suggesting that these changes in pressure did lead to cellular ischemia in the brain.
This physiologic insult is not just of academic interest. Joseph et al in the Baltimore Shock Trauma neurocritical care unit measure IAP in all their patients with significant and difficult to control intracranial pressure problems. When all medical therapy fails and the ICP remains high, these doctors frequently decompress the abdomen to relieve the ICP – reporting “good outcomes” in most patients who respond.[5] Deeren describes a simultaneous reduction in both IAP and ICP in patients with non-traumatic brain injury when they were treated with neuromuscular blockade – suggesting a less aggressive initial intervention than that employed by Joseph.[1] Other treatment options have been described such as continuously applied negative abdominal pressure to the closed abdominal wall.[6] Other authors report similar success with reducing ICP using IAH interventional therapies.[7, 8, 12, 13] The impact of IAH on ICP also has implications in trauma surgery since any use of laparoscopic technology leads to substantial elevations in IAH and may cause further CNS ischemia or even herniation.[9, 10]
Figure – IAP
and ICP changes from Deeren 2005
Figure: This figure from Deeren et
al[1] demonstrates the impact of neuromuscular blockade on patients
with intraabdominal hypertension. Neuromuscular blockade relaxes the
thoraco-abdominal wall, resulting in an increase in the
intra-abdominal volume, hence a decrease in the intra-abdominal
pressure. The result of this decrease in pressure on the abdomen is
a decrease in pressure transmitted via the chest into the cerebral
vasculature and a drop in ICP.
Clinical recommendations
· Patients with neurotrauma and other causes of intracranial pressure elevation should be screened for risk factors that can cause intra-abdominal hypertension – those who qualify should have their IAP measured, monitored and treated to assist in reducing ICP.
· All patients with intractable ICP elevations should have their IAP measured to ensure elevated IAP is not contributing to their ICP problems. If they have elevated IAP it should be aggressively treated to ensure it is not leading to cerebral perfusion deficits. (click here for treatment recommendations for IAH)
· In all patients with intracranial hypertension, preventive measures should be implemented to avoid increases in IAP (click here for medical treatment recommendations for IAH – steps 1 and steps 2)
· Beware of laparoscopic procedures in patients with ICH since this will increase their IAP and much of that pressure will be transmitted directly to their intracranial vault.
References:
1.
Deeren, D.H., H. Dits, and M.L. Malbrain,
Correlation between
intra-abdominal and intracranial pressure in nontraumatic brain
injury. Intensive Care Med, 2005.
2.
De laet, I., G. Citerio, and M.L. Malbrain,
The influence of
intraabdominal hypertension on the central nervous system: current
insights and clinical recommendations, is it all in the head?
Acta Clin Belg Suppl, 2007(1): p. 89-97.
3.
Citerio, G., et al.,
Induced abdominal compartment syndrome increases intracranial
pressure in neurotrauma patients: a prospective study. Crit Care
Med, 2001. 29(7): p.
1466-71.
4.
Bloomfield, G.L., et al.,
A proposed relationship
between increased intra-abdominal, intrathoracic, and intracranial
pressure. Crit Care Med, 1997.
25(3): p. 496-503.
5.
Joseph, D.K., et al.,
Decompressive laparotomy to treat intractable intracranial
hypertension after traumatic brain injury. J Trauma, 2004.
57(4): p. 687-95.
6.
Saggi, B.H., et al.,
Treatment of intracranial hypertension using nonsurgical abdominal
decompression. J Trauma, 1999.
46(4): p. 646-51.
7.
Bloomfield, G.L., et al.,
Treatment of increasing
intracranial pressure secondary to the acute abdominal compartment
syndrome in a patient with combined abdominal and head trauma. J
Trauma, 1995. 39(6): p.
1168-70.
8.
Nagpal, S., et al.,
Decompressive laparotomy to treat intractable cerebral hypoxia.
J Trauma, 2009. 67(5): p. E152-5.
9.
Al-Mufarrej, F., et al.,
Laparoscopic procedures in
adults with ventriculoperitoneal shunts. Surg Laparosc Endosc
Percutan Tech, 2005. 15(1):
p. 28-9.
10.
Irgau, I., Y. Koyfman, and J.I. Tikellis,
Elective intraoperative
intracranial pressure monitoring during laparoscopic
cholecystectomy. Arch Surg, 1995.
130(9): p. 1011-3.
11. Marinis, A., et al., Ischemia as a possible effect of increased intra-abdominal pressure on central nervous system cytokines, lactate and perfusion pressures. Crit Care, 2010. 14(2): p. R31. (Open access article - click here for full text)
12. Dorfman, J.D., et al., Decompressive Laparotomy for Refractory Intracranial Hypertension After Traumatic Brain Injury. Neurocrit Care, 2011.
13. Popugaev, K.A., et al., [Intraabdominal hypertension and secondary abdominal compartment-syndrome in the patient with craniopharyngioma in postoperative period]. Zh Vopr Neirokhir Im N N Burdenko, 2011. 75(1): p. 66-71.