Gokul, B J (2010) Assessment of cerebral vascular resistance in cirrhotic patients with hepatic encephalopathy using transcranial color doppler ultrasonography. Masters thesis, Madras Medical College, Chennai.
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Abstract
INTRODUCTION : Patients with liver cirrhosis have hyperdynamic circulation, characterized by increased cardiac output, decreased peripheral vascular resistance and arterial hypotension. Transcranial Doppler (TCD) allows observation of the velocity waveform in the major cerebral blood vessels. Some studies with TCD have shown that the mean cerebral blood velocity, an indicator of cerebral blood flow, is decreased or unchanged in patients with chronic liver disease. Dillon [et al.] reported that the mean cerebral blood velocity is decreased in advanced cirrhotic patients without encephalopathy. Lagi [et al.] showed no difference in the mean cerebral blood velocity between cirrhotic patients with ascites and healthy controls. Guevera [et al.] measured the cerebral resistive index instead of cerebral blood velocity in cirrhotics and demonstrated that the resistive index is higher in cirrhotics with ascites than in healthy controls. Pulsatility and resistive indices are widely accepted as an indicator of vascular resistance. These parameters are more accurate than measurement of cerebral blood flow velocity. Hepatic (portal-systemic) encephalopathy is a serious complication of chronic liver disease and is broadly defined as an alteration in mental status and cognitive function occurring in the presence of liver failure. Gut-derived neurotoxins that are not removed by the liver because of vascular shunting and decreased hepatic mass cause the symptoms that we know of as hepatic encephalopathy. Ammonia levels are typically elevated in patients with hepatic encephalopathy, but the correlation between severity of liver disease and height of ammonia levels is often poor. Other compounds and metabolites that may contribute to the development of encephalopathy include certain false neurotransmitters and mercaptans. Proposed mechanisms for pathogenesis of hepatic encephalopathy 1. Accumulation of toxins (Ammonia, Mercaptans) 2. Enhanced GABAergic neurotransmission 3. Accumulation of false neurotransmitters Evidence for reproducible alterations in soluble guanylate cyclase, nitric oxide (NO), and related pathways also has been published. It is possible that alteration in cerebral blood flow could contribute to pathogenesis of encephalopathy. This study was done to evaluate the cerebral hemodynamic parameters using TCD in cirrhotic patients with and without encephalopathy and compared then with healthy controls. AIM OF THE STUDY : The aim of this study is to assess the resistive and pulsatility indices which are indicators of cerebral vascular resistance in cirrhotic patients with hepatic encephalopathy using transcranial Doppler ultrasonography. CONCLUSION : Cerebral pulsatility and resistive indices of the middle cerebral artery are significantly higher in cirrhotic patients compared to controls indicating higher cerebral vascular resistance in cirrhotic patients. Patients with Child-Pugh C have higher resistive index compared to Child-Pugh A indicating that the cerebral resistance (RI) increases with the severity of liver cirrhosis. Serum bilirubin significantly correlates with cerebral pulsatility index and therefore the cerebral resistance. The cerebral pulsatility and resistive indices are higher in patients with hepatic encephalopathy compared to patients without encephalopathy. The cerebral pulsatility and resistive indices are higher in patients with grade II encephalopathy compared with patients without encephalopathy. Hence hepatic encephalopathy is clearly related to the cerebral vascular resistance and could play a role in its pathogenesis.
| Item Type: | Thesis (Masters) |
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| Uncontrolled Keywords: | cerebral vascular resistance ; cirrhotic patients ; hepatic encephalopathy ; transcranial ; color doppler ; ultrasonography. |
| Subjects: | MEDICAL > Gastroenterology |
| Depositing User: | Kambaraman B |
| Date Deposited: | 13 Jul 2017 04:07 |
| Last Modified: | 13 Jul 2017 04:07 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/1558 |
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