Under anaesthesia, which factor could cause an increase in blood pressure?

Under anaesthesia, which factor could cause an increase in blood pressure?

• A. Dehydration
• B. Hypothermia
• C. Increased levels of carbon dioxide in the blood
• D. Hypocapnia

Answer: (C)

Elevated carbon dioxide levels push the body toward higher blood pressure under anesthesia because CO2 triggers the sympathetic nervous system and increases vascular resistance. When CO2 rises (hypercapnia), central chemoreceptors stimulate sympathetic outflow, which raises heart rate and contractility and causes peripheral vasoconstriction. This sympathetic activation helps raise arterial pressure even though some anesthetic agents cause vasodilation. CO2 is also a potent cerebral vasodilator, increasing cerebral blood flow, and the body responds with higher systemic pressure to maintain perfusion. Dehydration lowers blood pressure by reducing circulating volume, not increasing it. Hypocapnia causes cerebral vasoconstriction and often lowers blood flow and pressure. Hypothermia can cause vasoconstriction as well, but the classic, direct link to a rising blood pressure in this anesthesia context is hypercapnia.

Elevated carbon dioxide levels push the body toward higher blood pressure under anesthesia because CO2 triggers the sympathetic nervous system and increases vascular resistance. When CO2 rises (hypercapnia), central chemoreceptors stimulate sympathetic outflow, which raises heart rate and contractility and causes peripheral vasoconstriction. This sympathetic activation helps raise arterial pressure even though some anesthetic agents cause vasodilation. CO2 is also a potent cerebral vasodilator, increasing cerebral blood flow, and the body responds with higher systemic pressure to maintain perfusion.

Dehydration lowers blood pressure by reducing circulating volume, not increasing it. Hypocapnia causes cerebral vasoconstriction and often lowers blood flow and pressure. Hypothermia can cause vasoconstriction as well, but the classic, direct link to a rising blood pressure in this anesthesia context is hypercapnia.