Health
Pharmaceuticals
Neurology
Neurotwitter
NeuroICU
Hydralazine
Cerebral Hemodynamics
ICP
Anti-hypertensive
Mechanism of Action
Smooth Muscle Relaxation
Arterial Vasodilation
Cerebral Blood Flow
Cerebral Autoregulation
Let’s discuss (one of the many) reasons why hydralazine should be used with caution ⚠️ in the NeuroICU
Hydralazine 💉 can NEGATIVELY ✖️ impact cerebral hemodynamics 🧠 and cause an ⤴️ in ICP 💦
But the question is, how? 🤔
A #Neurotwitter 🧵
Hydralazine 💉 can NEGATIVELY ✖️ impact cerebral hemodynamics 🧠 and cause an ⤴️ in ICP 💦
But the question is, how? 🤔
A #Neurotwitter 🧵
1/n So we know hydralazine is an anti hypertensive, but how does it work? 🧐
Full mechanism is not well understood, but proposed to
🌟 🛑 IP3-induced Ca+2 release
🌟⬆️ K+-channel opening
🌟⬆️NO formation
All which ➡️smooth muscle relaxation and arterial vasodilation
Full mechanism is not well understood, but proposed to
🌟 🛑 IP3-induced Ca+2 release
🌟⬆️ K+-channel opening
🌟⬆️NO formation
All which ➡️smooth muscle relaxation and arterial vasodilation
2/n Now, let’s review 🔑 concepts on cerebral🩸flow (CBF)
In a healthy🧠 (pink line), CBF remains relatively constant for a range of CPPs due to intact cerebral autoregulation (CA)
In contrast, injured brains (black line) have impaired CA and CBF is directly related to CPP
In a healthy🧠 (pink line), CBF remains relatively constant for a range of CPPs due to intact cerebral autoregulation (CA)
In contrast, injured brains (black line) have impaired CA and CBF is directly related to CPP
3/n Well, what factors impact CPP?
💡 The equation we have remembered by ♥️
🌟CPP = MAP - ICP
So for ex, a ⬇️MAP ➡️ ⬇️CPP and in order to compensate for ⤵️CPP, ICP will ⬆️ to maintain 🧠CBF🩸
If we change the X-axis from the previous📈for MAP, we can see this relationship
💡 The equation we have remembered by ♥️
🌟CPP = MAP - ICP
So for ex, a ⬇️MAP ➡️ ⬇️CPP and in order to compensate for ⤵️CPP, ICP will ⬆️ to maintain 🧠CBF🩸
If we change the X-axis from the previous📈for MAP, we can see this relationship
4/n So.. what about the hydralazine (HDLZ)? 🤔
⭐️HDLZ = POTENT vasodilator ▶️rapid, significant⤵️in MAP➡️⬇️CPP
⭐️HDLZ ALSO dilates cerebral vessels (arteries>veins)▶️further impairing (the already impaired) cerebral autoregulation in 🧠 injuries
But wait, there’s more! ⚠️👇🏻
⭐️HDLZ = POTENT vasodilator ▶️rapid, significant⤵️in MAP➡️⬇️CPP
⭐️HDLZ ALSO dilates cerebral vessels (arteries>veins)▶️further impairing (the already impaired) cerebral autoregulation in 🧠 injuries
But wait, there’s more! ⚠️👇🏻
5/n The “cerebral steal” phenomenon 😯
Similar to coronary🫀steal
🌟If blood vessels within abnormal brain regions are selectively responsive to vasodilators ➡️ then ⬆️perfusion in only select regions leaving other areas poorly perfused may result in risk of ischemia 🧠
Similar to coronary🫀steal
🌟If blood vessels within abnormal brain regions are selectively responsive to vasodilators ➡️ then ⬆️perfusion in only select regions leaving other areas poorly perfused may result in risk of ischemia 🧠
6/n Here is one of the first cases that was reported back in the 1970s describing increased ICP with hydralazine
🚨 alarming to note, authors found an ~ 20% reduction in SBP after a single dose of 12-18 mg of hydralazine that lead to a 110% ⬆️ in ICP ⚠️
ahajournals.org
🚨 alarming to note, authors found an ~ 20% reduction in SBP after a single dose of 12-18 mg of hydralazine that lead to a 110% ⬆️ in ICP ⚠️
ahajournals.org
Only other interesting finding was despite the drop in MAP and increase in ICP, CBF mildly increased or remained stable. This was in a case series of hypertensive emergencies and does not truly reflect how CBF would be impacted in the brain injured patient as a result of ⬆️ICP
All that being said, hope this provided insight on 1 (of the many) reasons to consider alt BP meds in 🧠injured pts!
Thanks to @pouyeah for inspiring this 🧵
Any additional pearls? @CaseyMayPharmD @KeatonSmetana @GilbertPharmD @caseyalbin @tigernole13 @AJWPharm @UFNeuroICU
Thanks to @pouyeah for inspiring this 🧵
Any additional pearls? @CaseyMayPharmD @KeatonSmetana @GilbertPharmD @caseyalbin @tigernole13 @AJWPharm @UFNeuroICU
Loading suggestions...