Which of the following would NOT result in an increase in intraocular pressure?

Which of the following would NOT result in an increase in intraocular pressure?

• A. Increase in PaCO2 from 35 to 40 mm Hg
• B. Arterial hypoxemia
• C. 100 mg IM succinylcholine
• D. Acute rise in venous pressure from coughing

Answer: (A)

Intraocular pressure tracks with factors that affect ocular venous outflow and ocular blood volume. Things that suddenly raise venous pressure in the head and neck or increase orbital contents tend to push IOP higher. Coughing abruptly elevates intrathoracic and venous pressures, which translates into higher orbital venous pressure and a rise in IOP. Succinylcholine causes muscle fasciculations that transiently increase orbital contents and push up the pressure inside the eye, also raising IOP. Arterial hypoxemia can cause vasodilation and increased ocular blood flow, which can raise IOP as well. A modest rise in arterial CO2 tension mainly affects cerebral vessels, increasing cerebral blood flow and sometimes intracranial pressure, but at typical perioperative levels it does not reliably raise intraocular pressure. Therefore a small increase in PaCO2 would not be expected to increase IOP, making it the correct choice for not increasing intraocular pressure.

Intraocular pressure tracks with factors that affect ocular venous outflow and ocular blood volume. Things that suddenly raise venous pressure in the head and neck or increase orbital contents tend to push IOP higher. Coughing abruptly elevates intrathoracic and venous pressures, which translates into higher orbital venous pressure and a rise in IOP. Succinylcholine causes muscle fasciculations that transiently increase orbital contents and push up the pressure inside the eye, also raising IOP. Arterial hypoxemia can cause vasodilation and increased ocular blood flow, which can raise IOP as well.

A modest rise in arterial CO2 tension mainly affects cerebral vessels, increasing cerebral blood flow and sometimes intracranial pressure, but at typical perioperative levels it does not reliably raise intraocular pressure. Therefore a small increase in PaCO2 would not be expected to increase IOP, making it the correct choice for not increasing intraocular pressure.