Editing Coma (section)

==Causes==
Many types of problems can cause a coma. Forty percent of comatose states result from [[drug poisoning]].<ref name="Liversedge 2010 337–339">{{cite journal|last1=Liversedge|first1=Timothy|last2=Hirsch|first2=Nicholas|year=2010|title=Coma|journal=Anaesthesia & Intensive Care Medicine|volume=11|issue=9|pages=337–339|doi=10.1016/j.mpaic.2010.05.008}}</ref> Certain drug use under certain conditions can damage or weaken the [[Synaptic vesicle|synaptic]] functioning in the [[Reticular formation|ascending reticular activating system]] (ARAS) and keep the system from properly functioning to arouse the brain.<ref name="Young 2009 32–47">{{cite journal |last1=Young |first1=G. Bryan |title=Coma |journal=Annals of the New York Academy of Sciences |date=March 2009 |volume=1157 |issue=1 |pages=32–47 |doi=10.1111/j.1749-6632.2009.04471.x |pmid=19351354 |bibcode=2009NYASA1157...32Y }}</ref> Secondary effects of drugs, which include [[Arrhythmia|abnormal heart rate]] and [[blood pressure]], as well as abnormal breathing and sweating, may also indirectly harm the functioning of the ARAS and lead to a coma. Given that drug poisoning is the cause for a large portion of patients in a coma, hospitals first test all comatose patients by observing [[pupil]] size and eye movement, through the [[Vestibulo-ocular reflex|vestibular–ocular reflex]]. (See ''Diagnosis'' below.)<ref name="Young 2009 32–47" />

The second most common cause of coma, which makes up about 25% of cases, is lack of oxygen, generally resulting from [[cardiac arrest]].<ref name="Liversedge 2010 337–339" /> The [[Central nervous system|central nervous system (CNS)]] requires a great deal of oxygen for its [[neurons]]. Oxygen deprivation in the [[Human brain|brain]], or ''[[cerebral hypoxia]]'', causes sodium and calcium from outside of the [[neuron]]s to decrease and [[Glossary of biology#I|intracellular]] calcium to increase, which harms neuron communication.<ref>{{cite journal |last1=Busl |first1=Katharina M. |last2=Greer |first2=David M. |title=Hypoxic-ischemic brain injury: Pathophysiology, neuropathology and mechanisms |journal=NeuroRehabilitation |date=28 January 2010 |volume=26 |issue=1 |pages=5–13 |doi=10.3233/NRE-2010-0531 |pmid=20130351 |doi-access=free }}</ref> Lack of oxygen in the brain also causes [[Adenosine triphosphate|ATP]] exhaustion and cellular breakdown from [[cytoskeleton]] damage and [[nitric oxide]] production.<ref>{{cite journal |last1=Siwicka-Gieroba |first1=Dorota |last2=Robba |first2=Chiara |last3=Gołacki |first3=Jakub |last4=Badenes |first4=Rafael |last5=Dabrowski |first5=Wojciech |title=Cerebral Oxygen Delivery and Consumption in Brain-Injured Patients |journal=Journal of Personalized Medicine |date=25 October 2022 |volume=12 |issue=11 |pages=1763 |doi=10.3390/jpm12111763 |pmc=9698645 |pmid=36573716 |doi-access=free }}</ref>

Twenty percent of comatose states result from an ischemic stroke, brain hemorrhage, or brain tumor.<ref name="Liversedge 2010 337–339" /> During a stroke, blood flow to part of the brain is restricted or blocked. An [[ischemic stroke]], [[Intracerebral hemorrhage|brain hemorrhage]], or brain tumor may cause restriction of blood flow. Lack of blood to cells in the brain prevents oxygen from getting to the neurons, and consequently causes cells to become disrupted and die. As brain cells die, brain tissue continues to deteriorate, which may affect the functioning of the ARAS, causing unconsciousness and coma.<ref>{{Cite web |last1=Durning |first1=Marijke Vroomen |last2=RN |title=Coma: Types, Causes, Treatments, Prognosis |url=https://www.webmd.com/brain/coma-types-causes-treatments-prognosis |access-date=2024-08-14 |website=WebMD |language=en}}</ref>

Comatose cases can also result from [[traumatic brain injury]], excessive [[blood loss]], [[malnutrition]], [[hypothermia]], [[hyperthermia]], [[hyperammonemia]],<ref>{{cite book |last1=Ali |first1=Rimsha |last2=Nagalli |first2=Shivaraj |title=StatPearls |date=2024 |publisher=StatPearls Publishing |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK557504/ |chapter=Hyperammonemia |pmid=32491436 }}</ref> abnormal glucose levels, and many other biological disorders. Furthermore, studies show that 1 out of 8 patients with traumatic brain injury experience a comatose state.<ref>{{cite journal |last1=Lombardi |first1=Francesco FL |last2=Taricco |first2=Mariangela |last3=De Tanti |first3=Antonio |last4=Telaro |first4=Elena |last5=Liberati |first5=Alessandro |title=Sensory stimulation for brain injured individuals in coma or vegetative state |journal=Cochrane Database of Systematic Reviews |date=22 April 2002 |issue=2 |pages=CD001427 |doi=10.1002/14651858.cd001427 |pmid=12076410 |pmc=7045727 }}</ref>

Heart-related causes of coma include [[cardiac arrest]], [[ventricular fibrillation]], [[ventricular tachycardia]], [[atrial fibrillation]], [[myocardial infarction]], [[heart failure]], [[arrhythmia]] when severe, [[cardiogenic shock]], [[myocarditis]], and [[pericarditis]]. [[Respiratory arrest]] is the only lung condition to cause coma, but many different lung conditions can cause [[decreased level of consciousness]], but do not reach coma.

Other causes of coma include [[Epilepsy|severe or persistent seizures]], [[kidney failure]], [[liver failure]], [[hyperglycemia]], [[hypoglycemia]], and infections involving the brain, like [[meningitis]] and [[encephalitis]].