Why does hyperammonemia cause cerebral edema?
Accumulation of ammonia and glutamine leads to disturbances in the regulation of cerebral osmolytes, increased free radical production and calcium-mediated mitochondrial injury, and alterations in glucose metabolism (inducing high levels of brain lactate), resulting in astrocyte swelling.
What are the symptoms of PRES?
PRES usually has an acute onset. Most people with PRES experience headaches and seizures; many also experience visual changes, confusion and drowsiness, weakness of the arm and/or leg on one side of the body (hemiplegia), difficulty speaking, or more rarely other neurological symptoms.
What is PRES caused by?
Common triggering factors of PRES include blood pressure fluctuations, preeclampsia/eclampsia, renal failure, cytotoxic agents, and autoimmune conditions (7, 8). Recently, several etiologies and atypical features have being increasingly recognized.
How does ammonia cause astrocyte swelling?
The oxidative/nitrosative stress caused by ammonia can also lead to cell swelling by increasing the activity of Na-K-Cl cotransporter-1 (NKCC-1) on astrocytes. Treatment of astrocyte cultures with ammonium acetate results in increased activity of NKCC-1 mediated by oxidative stress/nitrosative stress (Jayakumar et al.
Why does Cushing reflex cause respiratory depression?
The Cushing reflex classically presents as an increase in systolic and pulse pressure, reduction of the heart rate (bradycardia), and irregular respiration. It is caused by increased pressure inside the skull.
Is PRES reversible?
The most common symptoms are seizure and headache. The majority of patients have hypertension or an acute increase in blood pressure. PRES is usually reversible on prompt diagnosis and treatment of underlying conditions.
What drugs cause PRES?
The chemotherapy drugs reprted to cause PRES are cisplatin, cyclophosphamide, cytarabine, doxorubicin, etpside, gemcitabine, and vincristine. (Hararichain et al, 2015). These do not have to be overdoses. Other drugs can contribute to PRES by causing severe hypertension.
Why do astrocytes swell?
While the cause or causes of astrocyte swelling are still unknown, the increased levels of blood and consequent brain ammonia may be the major contributing factors of cellular swelling. The rate of cerebral edema in patients with hepatic disorders is correlated with blood and brain ammonia levels.
What are the three signs of Cushing response?
What is Cushing’s triad? Cushing’s triad refers to a set of signs that are indicative of increased intracranial pressure (ICP), or increased pressure in the brain. Cushing’s triad consists of bradycardia (also known as a low heart rate), irregular respirations, and a widened pulse pressure.