The variability of normal intracranial pressure

during wakefulness, during sleep, after a morning cup [s] of coffee [caffeine] after an alcoholic drink, etc….is a fascinating topic and relevant to to brain function and overall behavioural function and state.

This is a draft, is complex, still putting it together….may need to wait till there is more research on the normal and abnormal variation of intracranial pressure in spontaneously behaving animals…

Abstract

• Intracranial pressure (ICP) has the characteristic of a dynamic physiological phenomenon, and demonstrates many kinds of variation in a day. These ICP variations accompany such physiological phenomenon as respiration, pulse, etc., while ICP rises in cases where there is some intracranial pathology. It therefore is necessary to record ICP continually in order to clarify the mechanism of ICP variation due to intracranial pathology. Sleep is one of the physiological phenomena in diurnal rhythm influencing ICP. It has been observed that ICP increases during REM sleep (SREM). Intracranial Pressure V pp 358-363|  ICP Changes During Sleep in Man M. Ogashiwa K. Takeuchi

• It is known that ICP changes in humans with different body postures [15, 16]. Eftekhari, S., Westgate, C.S.J., Johansen, K.P. et al. Long-term monitoring of intracranial pressure in freely-moving rats; impact of different physiological states.Fluids Barriers CNS 17, 39 (2020). https://doi.org/10.1186/s12987-020-00199-z

• Did you know that raised intracranial pressure is further increased by coughing, sneezing, recumbency or exertion. [ Raised ICP can affect these behaviors unconsciously as the nervous system tries to avoid these behaviours under conditions of raised ICP].

• Changes to blood pressure, pulse and respiratory pattern are usually late signs of raised ICP in clinical practice. These signs are related to brain stem distortion or ischcaemia. Cushing Reflex – StatPearls – NCBI Bookshelfhttps://www.ncbi.nlm.nih.gov › books › NBK549801 by S Dinallo · 2020 

• SIGNIFICANT DEPARTURES FROM THE NORMAL PHYSIOLOGICAL STATUS CAN ADVERSELY AFFECT ICP OR CEREBRAL PERFUSION. BMJ Journals J. of Neurology, Neurosurgery and Psychiatry Volume 73, Issue suppl 1 RAISED INTRACRANIAL PRESSURE  Laurence T Dunn

• Fever increases ICP, especially after head injury. Crit Care. 2014; 18(5): 552. Published online 2014 Oct 14. doi: 10.1186/s13054-014-0552-7 Body temperature affects cerebral hemodynamics in acutely brain injured patients: an observational transcranial color-coded duplex sonography study Federica Stretti,Miriam Gotti,Silvia Pifferi,Giovanna Brandi,Federico Annoni, and  Nino Stocchetti

Seizures contribute to raised ICP.

Muscle activity may further raise ICP by increasing intrathoracic pressure and obstructing cerebral venous outflow.

Hypothermia reduces ICP.

1st reference…have to go back to find again…oops.

Hypoventilation [hypoxia OR hypercapnia] raises ICP; J Am Coll Surg. 1998 Jul;187(1):32-8. doi: 10.1016/s1072-7515(98)00126-4. Effects of hyperventilation and hypoventilation on PaCO2 and intracranial pressure during acute elevations of intraabdominal pressure with CO2 pneumoperitoneum: large animal observations

R J Rosenthal ¹, R L Friedman, A Chidambaram, A M Khan, J Martz, Q Shi, M Nussbaum

Hypertension [can be cause or consequence of raised ICP]

Airway Obstruction

Metabolic [drug induced]

Seizures

Hyperpyrexia

High altitude cerebral edema

Agitation and pain can increase blood pressure and ICP.

3rd reference [I am getting lazy but you can check out any of these points just like I did on PubMed.

Alcohol intoxication increases cerebral blood flow [in head injured patients].

Caffeine decreases cerebral blood flow [in head injured patients].

Will come back to this when there is more research on this topic in animals other than those with brain injury….

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A change in mental status or comatose patient should prompt urgent evaluation.

A classic triad of bradycardia, respiratory depression and hypertension is known as Cushing’s Triad and highly indicative of intracranial hypertension.

2nd reference

to be continued after I do my errands…..I LOVE research, it is so cool to learn these things and thank you to all the hard work done by researchers!!!