Are we targeting too high a blood pressure intraop?

[nimbus]

Do you give fentanyl at induction? What’s your typical analgesic plan for a straight forward case? Give any long acting narcotics?

For the FESS you’re describing, did your attending not plan to give any opiate?

I’ll give fent 50-100mcg at induction for painful procedures. And additional opioid as needed. But I wait for the patient to show me they can tolerate more opioids. For nonpainful procedures or for patients with blocks, I will often omit any opioids. For the FESS, my attending didn’t want to give any opioids.

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Members don't see this ad.

 

[fakin' the funk]

3. We know patients are dehydrated preop. That has been know for the past 4 decades. A bag of fluid like LR seems quite reasonable for the vast majority of patients prior to starting any pressors/drips.

Cmon man. No they're not.

When you wake up in the morning, do you have an intravascular fluid deficit? What if you wake up at 4am and have a 12oz Gatorade and then show up for your 8am surgery?

The vast vast majority of patients don't hit the OR door hypovolemic, and if y'all aren't giving preop clear liquids you're behind on this.

I don't disagree that a liter of fluid is reasonable, but also, intraop hypotension is commonly commonly due to anesthetic effect to lower SVR. Run PPV on everyone and see -it's always low unless there's an obvious hypovolemic process eg bleeding. Pressor is indicated for many, and will benefit many patients.

 

[BLADEMDA]

The recently released MAP 65 Trial has certainly raised some questions in the critical care community this year, namely whether we just pulled a "MAP of 65 mmHg" out of our collective a$$es and have been targeting that number for years for no other reason than trying to normalize numbers for the sake of normalizing numbers.

The trial was multicenter and randomized 2600 patients aged 65 and older with vasodilatory shock to a MAP of 60-65 or to usual standard of care aka a MAP at the discretion of the clinician. Bottom line results: 90 day mortality difference was non-significant (41% in permissive group vs 43.8% in standard of care), as was serious adverse events including acute renal failure and arrhythmia. The biggest weakness of the trial is that the intervention group still spent a lot of time with a MAP above 70, however the standard of care group spent a lot of time with a MAP above 80, so at least the differential was preserved.

Both PulmCCM and PulmCrit have excellent analyses of the trial.

From PulmCCM:
" Targeting a lower mean arterial pressure does not necessarily deprive tissues of perfusion and may actually improve flow if critical closing pressures fall below mean arterial pressure. The trouble is that each organ has its own conductance curve and the slope of each organ’s curve adapts differently to an equally dynamic physiological milieu within and between patients. A patient with a 90% left main stenosis has a very low, and fixed, cardiac conductance; therefore, vasodilation of other tissue beds poses an existential risk. Whereas an 18-year old with pneumococcal bacteremia and anaphylaxis from amoxicillin will have high total body tissue conductance, a low mean arterial pressure and, potentially, preserved organ perfusion. To the credit of the 65 Trial, enrolling those at least 65 years of age is anticipated to concentrate the former, rather than the latter patient, yet mortality was lower in the permissive hypotension group [absolute risk difference, −2.85%; 95% CI, −6.75 to 1.05; P = .15] and these patients received fewer vasoactive medications. "



Personally, based on the classic teaching of the shift in autoregulatory curves, I've always been of the opinion that it's better to run geriatric pts at a MAP of ~80, especially if they have history of HTN, CAD, CVA, CKD etc. Same goes for older folks on CPB and I've always thought the general rule of "MAP = Age" while on pump is a sound idea. We've known for awhile that this logic may be dubious because as PulmCCM points out, perfusion at the local tissue bed is what really matters, but I've always seen running a slightly higher MAP at the very least as not causing any harm.

Does everyone else out there also run older pts at a slightly higher blood pressure? Does the fact that a slightly lower MAP didn't worsen mortality in critically ill geriatric pts (let alone relatively healthy and/or optimized geriatric pts coming for elective surgery) change your thinking? Or are the results of this trial not generalizable at all due to the fact that volatile anesthetics disrupt autoregulation curves?

Cmon man. No they're not.

When you wake up in the morning, do you have an intravascular fluid deficit? What if you wake up at 4am and have a 12oz Gatorade and then show up for your 8am surgery?

The vast vast majority of patients don't hit the OR door hypovolemic, and if y'all aren't giving preop clear liquids you're behind on this.

I don't disagree that a liter of fluid is reasonable, but also, intraop hypotension is commonly commonly due to anesthetic effect to lower SVR. Run PPV on everyone and see -it's always low unless there's an obvious hypovolemic process eg bleeding. Pressor is indicated for many, and will benefit many patients.

Yes, I am dehydrated in the morning and need to increase my fluid intake. As for the gatorade that is more evidence that most patients need some fluids. Finally, just because you ask patients to drink fluids the day before surgery and even the morning of doesn't mean that most of them actually complied. At my shop, we routinely encourage hydration prior to surgery but even then many are still needing fluid in the O.R.

FYI, the vast majority of patients (ASA 1-3) rarely require drips of pressors in the O.R. Typically, a little ephedrine or phenylephrine "Bump" is all most people need intraop who have a good EF. At the outpatient center most just get a bag of fluid and rarely require any pressors at all.

 

[deleted171991]

I don't disagree that a liter of fluid is reasonable, but also, intraop hypotension is commonly commonly due to anesthetic effect to lower SVR. Run PPV on everyone and see -it's always low unless there's an obvious hypovolemic process eg bleeding. Pressor is indicated for many, and will benefit many patients.

One of the reasons the PPV is low could be because one needs (much) more than 8 ml/kg of VT to see reliable PPV changes, among others. Typical 70 kg IBW patient is run at 450-500 ml of VT nowadays, at least by the good anesthesiologists.

So absence of evidence is not evidence of absence.

Btw, I agree that patients are by far not as dehydrated as people used to think, and intraop fluid losses due to an open abdomen are also much smaller. Still, somebody with chronic HTN may be chronically hypovolemic, especially when one drops the pathologically high SVR.

 

[chocomorsel]

Don’t find nitrous as reliable as volatiles for amnesia/anesthesia and probably wouldn’t do a case with only nitrous.

I think it was a joke. Can you even do 75% nitrous? Do the machines let you do that? Something about a hypoxic gas mixture is calling to me in the recesses of my brain. What's the max nitrous one can do? I honestly don't remember as I hardly use it.

 

[anbuitachi]

Cmon man. No they're not.

When you wake up in the morning, do you have an intravascular fluid deficit? What if you wake up at 4am and have a 12oz Gatorade and then show up for your 8am surgery?

The vast vast majority of patients don't hit the OR door hypovolemic, and if y'all aren't giving preop clear liquids you're behind on this.

I don't disagree that a liter of fluid is reasonable, but also, intraop hypotension is commonly commonly due to anesthetic effect to lower SVR. Run PPV on everyone and see -it's always low unless there's an obvious hypovolemic process eg bleeding. Pressor is indicated for many, and will benefit many patients.

when i wake up in the morning i feel dry as hell... what color is your urine when you wake up? don tthink needs anywhere cloes to 2Ls but still

 

[anbuitachi]

I think it was a joke. Can you even do 75% nitrous? Do the machines let you do that? Something about a hypoxic gas mixture is calling to me in the recesses of my brain. What's the max nitrous one can do? I honestly don't remember as I hardly use it.

close to 80% . i just did a case and used 75% for last hr or so. woke up great

 

[chocomorsel]

close to 80% . i just did a case and used 75% for last hr or so. woke up great

Do they get nauseated? I've never really used it outside of pediatrics honestly.

 

[Urzuz]

What’s the controversy in saying volatile or anesthetic overdose contributes to hypotension?

There is no argument there (or shouldn’t be). The objections to your first post stemmed from the blanket, all-encompassing statement you originally made. In case you forgot, you said “If you are needing pressors intraop, you are giving too much gas (outside of blood loss, compressing vessels, other extenuating circumstances, etc)”, which is not only untrue, but dangerous.

 

[MoMoGesiologist]

One of the reasons the PPV is low could be because one needs (much) more than 8 ml/kg of VT to see reliable PPV changes, among others. Typical 70 kg IBW patient is run at 450-500 ml of VT nowadays, at least by the good anesthesiologists.

So absence of evidence is not evidence of absence.

Btw, I agree that patients are by far not as dehydrated as people used to think, and intraop fluid losses due to an open abdomen are also much smaller. Still, somebody with chronic HTN may be chronically hypovolemic, especially when one drops the pathologically high SVR.

How dare you tell us that there are certain conditions that need to be fulfilled before we use PPV/SVV for making decisions. If I see a number, I treat it. Stick to the algorithm!

 

[MoMoGesiologist]

I think it was a joke. Can you even do 75% nitrous? Do the machines let you do that? Something about a hypoxic gas mixture is calling to me in the recesses of my brain. What's the max nitrous one can do? I honestly don't remember as I hardly use it.

I thought it might be a joke. But also, don’t know enough about the poster to know if they are actually that dense.

 

[chocomorsel]

I thought it might be a joke. But also, don’t know enough about the poster to know if they are actually that dense.

Apparently it wasn't a joke.

 

[deleted171991]

I think it was a joke. Can you even do 75% nitrous? Do the machines let you do that? Something about a hypoxic gas mixture is calling to me in the recesses of my brain. What's the max nitrous one can do? I honestly don't remember as I hardly use it.

I think 75% is the max number, as long as the rest is O2. There needs to be at least 25% O2 in any mixture containing nitrous, if I'm not wrong.

 

[deleted171991]

Do they get nauseated? I've never really used it outside of pediatrics honestly.

I have not seen more nausea with the 50% nitrous than without, in adults (and I have used nitrous extensively in outpatient settings). I am not so sure about 70-75%.

 

[anbuitachi]

Do they get nauseated? I've never really used it outside of pediatrics honestly.

patient was not nauseated. i only had it on for about a bit over 1 hour or so of the case. i dont really find more nausea if i keep it short, but i also give antiemetics!

 

[BLADEMDA]

How dare you tell us that there are certain conditions that need to be fulfilled before we use PPV/SVV for making decisions. If I see a number, I treat it. Stick to the algorithm!

All I am saying is that a little fluid (1 liter) is probably a good idea in most patients. By no means am I stating we should FLOOD patients with fluid but rather use some common sense and the published data to give a little LR during the case. I don't want to start a literature debate about fluids on this thread, But, in my experience over 3 decades a little fluid really does help the situation most of the time. I am also not "bashing" pressors but making a point that fluids do play a role in patient case management.



Functional intravascular volume deficit in patients before surgery
M. BUNDGAARD‐NIELSEN

C. C. JØRGENSEN

N. H. SECHER

H. KEHLET
First published:25 February 2010

https://doi.org/10.1111/j.1399-6576.2009.02175.x
Citations: 45
Address:
Morten Bundgaard‐Nielsen
Section of Surgical Pathophysiology 4074
Blegdamsvej 9
Rigshospitalet
DK‐2100 Copenhagen
Denmark
e‐mail: morten.bundgaard‐[email protected]
Read the full text


Abstract
Background: Stroke volume (SV) maximization with a colloid infusion, referred to as individualized goal‐directed therapy, improves outcome in high‐risk surgery. The fraction of patients who need intravascular volume to establish a maximal SV has, however, not been evaluated, and there are only limited data on the volume required to establish a maximal SV before the start of surgery. Therefore, we estimated the occurrence and size of the potential functional intravascular volume deficit in surgical patients.
Methods: Patients scheduled for mastectomy (n =20), open radical prostatectomy (n =20), or open major abdominal surgery (n =20) were anaesthetized, and before the start of surgery, a 200 ml colloid fluid challenge was provided and repeated if a ≥10% increment in SV estimated by oesophageal Doppler was established. The volume needed for SV maximization defined the intravascular volume deficit.
Results: Forty‐two (70%) of the patients needed volume to establish a maximal SV. For the patients needing volume, the required amount was median 200 ml (range 200–600 ml), with no significant difference between the three groups of patients. The required volume was ≥400 ml in nine patients (15%).
Conclusion: The majority of anaesthetized patients present with a functional intravascular volume deficit before surgery. Although the deficit in general was minor, a fraction of patients presented with a deficit that may be of clinical relevance, emphasizing the importance of the individual approach of goal‐directed fluid therapy.


NOTE: The fluid use in this study was COLLOID but I prefer 1 bag of LR.

 

[vector2]

The volume needed for SV maximization defined the intravascular volume deficit.

The bolded is the key line of the abstract. We must be very clear: Being able to augment stroke volume with a fluid challenge (that is, being volume responsive) is not synonymous with being hypovolemic or needing volume.

Even as I sit here and write this, if you give me a 500cc 5% albumin bolus I am definitely going to increase my stroke volume, but that doesn't mean that I actually was intravascularly depleted- it just means I was on the upslope of the Starling curve just like most everyone else out there. That being said, my practice is much the same and I usually empirically give most healthyish NPO patients 1L of fluid when they're coming for surgery, but we should not be synonymizing "I gave the patient so much fluid that the SV stopped going up" with "intravascular volume depletion"

 

[nimbus]

Not that it’s clinically significant but food for thought. A liter of LR has 9gm of sodium. That’s the equivalent of 9 Big Macs.

 

[vector2]

Not that it’s clinically significant but food for thought. A liter of LR has 9gm of sodium. That’s the equivalent of 9 Big Macs.

Mmmmm, check my math :

1 meq of (elemental) sodium = 23 mg

LR = 130 meq/L * 23 mg/meq = 2990 mg/L

 

[nimbus]

Mmmmm, check my math :

1 meq of (elemental) sodium = 23 mg

LR = 130 meq/L * 23 mg/meq = 2990 mg/L

Ahhhh you’re right. I didn’t account for the chloride and the lactate when I read the label. I should have said 6gm of NaCl/liter.

 

[BLADEMDA]

Minimally/moderately invasive surgery — For most adult patients undergoing relatively brief minimally or moderately invasive surgery with planned early postoperative ambulation, we administer 1 to 2 L of a balanced electrolyte solution if the procedure does not incur significant fluid shifts or blood loss. This 1 to 2 L of fluid is typically administered during surgery, over a period of 30 minutes to two hours. Such empiric but limited fluid administration for less invasive surgery in ambulatory patients addresses the mild dehydration caused by preoperative fasting and is associated with less postoperative nausea and vomiting, as well as less postoperative pain [114,115]. A smaller fluid volume is appropriate in patients with a history of heart failure or chronic obstructive pulmonary disease.

UpToDate

www.uptodate.com

 

[vector2]

Most dehydration is isotonic/normonatremic and osmolarity/electrolyte abnormalities don't appear until it's gotten moderate or severe. According to medscape cap refill, resp rate, and skin turgor are the best indicators of dehydration and all are normal when the condition is mild. Vitals signs in all likelihood will all be normal as well.

It begs the question of how does one even diagnose "mild" dehydration, or is mild dehydration synonynous with some normal guy who just randomly feels subjectively thirsty because it's been a few hours since his last cup of coffee?

 

[BLADEMDA]

Most dehydration is isotonic/normonatremic and osmolarity/electrolyte abnormalities don't appear until it's gotten moderate or severe. According to medscape cap refill, resp rate, and skin turgor are the best indicators of dehydration and all are normal when the condition is mild. Vitals signs in all likelihood will all be normal as well.

It begs the question of how does one even diagnose "mild" dehydration, or is mild dehydration synonynous with some normal guy who just randomly feels subjectively thirsty because it's been a few hours since his last cup of coffee?

All I can tell you is that in my neck of the woods with high heat and humidity many of my patients are dehydrated; we can argue whether that dehydration is mild (most of the time) or moderate (some of the time) but that doesn't alter the fact that we both think giving some LR (1-2 liters) is a good idea for the vast majority of patients.

I screen the Bun/CR routinely and that shows dehydration quite often. I try to drink at least 1-2 bottles of water every morning at the start of my day. I often wonder if overeating is also linked to inadequate hydration to some degree.

 

[BLADEMDA]

Add a glass of water to your morning routine.

“The first thing you need to start the day is not a cup of coffee, it’s a glass of water,” said Frazier. “Most of us sleep six to eight hours a night, and that’s a big chunk of the 24-hour day where we’re not drinking or eating any foods that have water naturally in it, and so when you wake up, your body is actually in a state where you’re the most dehydrated. When you wake up in the morning, you should have a full 8-ounce glass of water just to kick-start your day, just to get your body and your organs to wake up and say ‘Hey, this is what I’ve been looking for.’”

Limit your coffee intake to one cup a day.

“Now we are a generation of coffee drinkers with a Starbucks at every corner,” Frazier said. “I know people who drink four to five cups of coffee a day. And all of that dehydrates our system. One cup of coffee is the standard 6- to 8-ounce cup, not the 20-ounce version you see these days. Everyone is allotted their one cup of coffee or caffeine, as long as you then follow up with a supplement of a glass of water.”

Not all water is the same.

Frazier said carbonated water or sports drinks should not be considered a substitute as one of the allotted eight glasses per day.

“I think there is a mixed debate versus if carbonation dehydrates us versus hydrates us,” Frazier said. “Carbonated water has other effects that I worry about like tooth decay, because the carbonation breaks down our enamel. One carbonated drink a day shouldn’t dehydrate too much. And some people like the electrolyte drinks and I’m ok with that too, but only one or two.”

Avoid overdoing it with sodium, alcohol and processed foods.

Sodium-rich and processed foods will dehydrate, Frazier said. And with each glass of alcohol, “we should try to drink a glass of water to counter the effects.”

Juice and soda are not water.

“Some juices and pop have high sugar or fructose,” Frazier said. “Even if it’s ‘100 percent natural’ juice, I tell my patients the limit of juice per day should be that small 4-ounce juice cup. I will try to negotiate with my patients and say, ‘If you have a can of pop, you have to have a full glass of water before you have your next can of pop.’ Juice is not water. Pop is not water. Coffee is not water. We are meant to drink water throughout the day to rehydrate.”

Jenniffer Weigel is director of community relations for the Sun-Times and has had a lifelong interest in wellness and related topics. She’s a frequent contributor to the Wednesday Well section.

Doctors say most Americans are dehydrated

"The first thing you need to start the day is not a cup of coffee, it’s a glass of water," said Dr. Kendra Frazier.

chicago.suntimes.com

 

[nimbus]

Add a glass of water to your morning routine.

“The first thing you need to start the day is not a cup of coffee, it’s a glass of water,” said Frazier. “Most of us sleep six to eight hours a night, and that’s a big chunk of the 24-hour day where we’re not drinking or eating any foods that have water naturally in it, and so when you wake up, your body is actually in a state where you’re the most dehydrated. When you wake up in the morning, you should have a full 8-ounce glass of water just to kick-start your day, just to get your body and your organs to wake up and say ‘Hey, this is what I’ve been looking for.’”

Limit your coffee intake to one cup a day.

“Now we are a generation of coffee drinkers with a Starbucks at every corner,” Frazier said. “I know people who drink four to five cups of coffee a day. And all of that dehydrates our system. One cup of coffee is the standard 6- to 8-ounce cup, not the 20-ounce version you see these days. Everyone is allotted their one cup of coffee or caffeine, as long as you then follow up with a supplement of a glass of water.”

Not all water is the same.

Frazier said carbonated water or sports drinks should not be considered a substitute as one of the allotted eight glasses per day.

“I think there is a mixed debate versus if carbonation dehydrates us versus hydrates us,” Frazier said. “Carbonated water has other effects that I worry about like tooth decay, because the carbonation breaks down our enamel. One carbonated drink a day shouldn’t dehydrate too much. And some people like the electrolyte drinks and I’m ok with that too, but only one or two.”

Avoid overdoing it with sodium, alcohol and processed foods.

Sodium-rich and processed foods will dehydrate, Frazier said. And with each glass of alcohol, “we should try to drink a glass of water to counter the effects.”

Juice and soda are not water.

“Some juices and pop have high sugar or fructose,” Frazier said. “Even if it’s ‘100 percent natural’ juice, I tell my patients the limit of juice per day should be that small 4-ounce juice cup. I will try to negotiate with my patients and say, ‘If you have a can of pop, you have to have a full glass of water before you have your next can of pop.’ Juice is not water. Pop is not water. Coffee is not water. We are meant to drink water throughout the day to rehydrate.”

Jenniffer Weigel is director of community relations for the Sun-Times and has had a lifelong interest in wellness and related topics. She’s a frequent contributor to the Wednesday Well section.

Doctors say most Americans are dehydrated

"The first thing you need to start the day is not a cup of coffee, it’s a glass of water," said Dr. Kendra Frazier.

chicago.suntimes.com

That article is full of misinformation, Dr. Frazier offers many unfounded opinions in it. There may be reasons (mainly caloric) to avoid coffee, juice, and soda. But for hydration purposes they are mostly water and thus as good as water. It’s absurd to say that “carbonated beverages dehydrate you”. What would be the mechanism for that? You can survive drinking only juice or soda if water is not available or not preferred. I almost never drank water when I was growing up and still survived. During residency, my residency director and several residents survived on beer when they ran out of water on a fishing trip. Also, drinking 3-4 cups of coffee/day is associated with the greatest mortality benefit.


Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes

 

[vector2]

That article is full of misinformation, Dr. Frazier offers many unfounded opinions in it. There may be reasons (mainly caloric) to avoid coffee, juice, and soda. But for hydration purposes they are mostly water and thus as good as water. It’s absurd to say that “carbonated beverages dehydrate you”. What would be the mechanism for that? You can survive drinking only juice or soda if water is not available or not preferred. I almost never drank water when I was growing up and still survived. During residency, my residency director and several residents survived on beer when they ran out of water on a fishing trip. Also, drinking 3-4 cups of coffee/day is associated with the greatest mortality benefit.


Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes

-------------
Post-Exercise Rehydration: Effect of Consumption of Beer with Varying Alcohol Content on Fluid Balance after Mild Dehydration


Purpose
The effects of moderate beer consumption after physical activity on rehydration and fluid balance are not completely clear. Therefore, in this study, we investigated the effect of beer consumption, with varying alcohol content, on fluid balance after exercise-induced dehydration.
Methods
Eleven healthy males were included in this cross over study (age 24.5 ± 4.7 years, body weight 75.4 ± 3.3 kg, VO2max 58.3 ± 6.4 mL kg min−1). Subjects exercised on a cycle ergometer for 45 min at 60% of their maximal power output (Wmax) until mild dehydration (1% body mass loss). Thereafter, in random order, one of five experimental beverages was consumed, in an amount equal to 100% of their sweat loss: non-alcoholic beer (0.0%), low-alcohol beer (2.0%), full-strength beer (5.0%), an isotonic sports drink, and water. Fluid balance was assessed up till 5 h after rehydration.
Results
After 1 h, urine production was significantly higher for 5% beer compared to the isotonic sports drink (299 ± 143 vs. 105 ± 67 mL; p < 0.01). At the end of the 5-h observation period, net fluid balance (NFB) was negative for all conditions (p = 0.681), with the poorest fluid retention percentage for 5% beer (21% fluid retention) and the best percentage for the isotonic sports drink (42%). Non-alcoholic beer, low-alcoholic beer, and water resulted in fluid retention of 36, 36, and 34%, respectively (p = 0.460).
Conclusion
There was no difference in NFB between the different beverages. Only a short-lived difference between full-strength beer and the isotonic sports drink in urine output and NFB was observed after mild exercise-induced dehydration. Fluid replacement – either in the form of non-alcoholic beer, low-alcoholic beer, full-strength beer, water, or an isotonic sports drink of 100% of body mass loss was not sufficient to achieve full rehydration. The combination of a moderate amount of beer, with varying alcohol content, enough water or electrolyte- and carbohydrate beverages, and salty foods might improve rehydration, but more research is needed.
--------------


I'm glad science was finally able to settle the issue of whether crushing a 6pk of busch light is hydrating or not

 

[deleted162650]

Not that it’s clinically significant but food for thought. A liter of LR has 9gm of sodium. That’s the equivalent of 9 Big Macs.

You’re thinking about NS.

 

[deleted162650]

During residency, my residency director and several residents survived on beer when they ran out of water on a fishing trip.

Who brings water on a fishing trip??

The closest thing to water on a fishing trip is Coors Light.

 

[deleted171991]

-------------
Post-Exercise Rehydration: Effect of Consumption of Beer with Varying Alcohol Content on Fluid Balance after Mild Dehydration


Purpose
The effects of moderate beer consumption after physical activity on rehydration and fluid balance are not completely clear. Therefore, in this study, we investigated the effect of beer consumption, with varying alcohol content, on fluid balance after exercise-induced dehydration.
Methods
Eleven healthy males were included in this cross over study (age 24.5 ± 4.7 years, body weight 75.4 ± 3.3 kg, VO2max 58.3 ± 6.4 mL kg min−1). Subjects exercised on a cycle ergometer for 45 min at 60% of their maximal power output (Wmax) until mild dehydration (1% body mass loss). Thereafter, in random order, one of five experimental beverages was consumed, in an amount equal to 100% of their sweat loss: non-alcoholic beer (0.0%), low-alcohol beer (2.0%), full-strength beer (5.0%), an isotonic sports drink, and water. Fluid balance was assessed up till 5 h after rehydration.
Results
After 1 h, urine production was significantly higher for 5% beer compared to the isotonic sports drink (299 ± 143 vs. 105 ± 67 mL; p < 0.01). At the end of the 5-h observation period, net fluid balance (NFB) was negative for all conditions (p = 0.681), with the poorest fluid retention percentage for 5% beer (21% fluid retention) and the best percentage for the isotonic sports drink (42%). Non-alcoholic beer, low-alcoholic beer, and water resulted in fluid retention of 36, 36, and 34%, respectively (p = 0.460).
Conclusion
There was no difference in NFB between the different beverages. Only a short-lived difference between full-strength beer and the isotonic sports drink in urine output and NFB was observed after mild exercise-induced dehydration. Fluid replacement – either in the form of non-alcoholic beer, low-alcoholic beer, full-strength beer, water, or an isotonic sports drink of 100% of body mass loss was not sufficient to achieve full rehydration. The combination of a moderate amount of beer, with varying alcohol content, enough water or electrolyte- and carbohydrate beverages, and salty foods might improve rehydration, but more research is needed.
--------------


I'm glad science was finally able to settle the issue of whether crushing a 6pk of busch light is hydrating or not

Because we really needed a study to prove that inhibiting ADH increases diuresis.

 

[deleted171991]

Most dehydration is isotonic/normonatremic and osmolarity/electrolyte abnormalities don't appear until it's gotten moderate or severe. According to medscape cap refill, resp rate, and skin turgor are the best indicators of dehydration and all are normal when the condition is mild. Vitals signs in all likelihood will all be normal as well.

It begs the question of how does one even diagnose "mild" dehydration, or is mild dehydration synonynous with some normal guy who just randomly feels subjectively thirsty because it's been a few hours since his last cup of coffee?

Most dehydration results in hypernatremia (as in more water is lost than sodium). That's why we want to drink water, not to lick salt, when we get dehydrated.

Sweat is hyponatremic. Gastric secretions are hyponatremic. Respiratory loss is vapor. Eu-/hypovolemic urine is hyponatremic. One cannot lose more sodium than water except through urine, in the appropriate hormonal setting. Hypovolemia induces RAA activation and sodium retention.

So why doesn't any dehydration result in hypernatremia and hypovolemia? Because the average human has up to 6 liters of extra interstitial fluid, that can be easily mobilized. That extracellular fluid space of 14L for the 70 kg human, which equilibrates with plasma, is only 25% intravascular.

 

[BLADEMDA]

Most dehydration results in hypernatremia (as in more water is lost than sodium). That's why we want to drink water, not to lick salt, when we get dehydrated.

Sweat is hyponatremic. Gastric secretions are hyponatremic. Respiratory loss is vapor. Eu-/hypovolemic urine is hyponatremic. One cannot lose more sodium than water except through urine, in the appropriate hormonal setting. Hypovolemia induces RAA activation and sodium retention.

So why doesn't any dehydration result in hypernatremia and hypovolemia? Because the average human has up to 6 liters of extra interstitial fluid, that can be easily mobilized. That extracellular fluid space of 14L for the 70 kg human, which equilibrates with plasma, is only 25% intravascular.

What we do know is that for most patients (outpatient) without Resp. compromise, normal EF, etc having a typical non invasive surgery that being hydrated with some LR reduces post op N/V and pain. In the hospital setting, I found many elderly patients are extremely dry with high BUN/CR as their medical doctor is concerned about CHF. Typically, these elderly patients need fluid in the O.R. and we have known this fact for 30+ years.

Hydration and outcome in older patients admitted to hospital (The HOOP prospective cohort study)

Background: older adults are susceptible to dehydration due to age-related pathophysiological changes. We aimed to investigate the prevalence of hyperosmolar dehydration (HD) in hospitalised older adults, aged ≥65 years, admitted as an emergency ...

www.ncbi.nlm.nih.gov

 

[BLADEMDA]

Hypotension Kills:

Care of elderly patients: a prospective audit of the prevalence of hypotension and the use of BIS intraoperatively in 25 hospitals in London - Perioperative Medicine

Background Anaesthesia is frequently complicated by intraoperative hypotension (IOH) in the elderly, and this is associated with adverse outcome. The definition of IOH is controversial, and although management guidelines for IOH in the elderly exist, the frequency of IOH and typical clinically...

perioperativemedicinejournal.biomedcentral.com

Hypotension occurs frequently during anaesthesia and is associated with adverse outcomes in the elderly. These include stroke, compromised postoperative neurological performance, acute kidney injury, myocardial infarction, and increased 30-day and 1-year mortality (Bijker et al 2009; Bijker et al 2012; Yocum et al. 2009; Sun et al. 2015; Walsh et al. 2013; Monk et al 2005; Mascha et al 2015). Thus, the Association of Anaesthetists of Great Britain and Ireland (AAGBI) guidelines recommend IOH should be avoided in older patients (Griffiths et al. 2014),

 

[vector2]

Most dehydration results in hypernatremia (as in more water is lost than sodium). That's why we want to drink water, not to lick salt, when we get dehydrated.

Sweat is hyponatremic. Gastric secretions are hyponatremic. Respiratory loss is vapor. Eu-/hypovolemic urine is hyponatremic. One cannot lose more sodium than water except through urine, in the appropriate hormonal setting. Hypovolemia induces RAA activation and sodium retention.

So why doesn't any dehydration result in hypernatremia and hypovolemia? Because the average human has up to 6 liters of extra interstitial fluid, that can be easily mobilized. That extracellular fluid space of 14L for the 70 kg human, which equilibrates with plasma, is only 25% intravascular.

This is the key part. Obviously the losses aren't perfectly isotonic in most situations but my point is that making the diagnosis of *mild* dehydration based on labs is essentially impossible since it will be compensated for by the phenomena you describe.

 

[BLADEMDA]

Clinical Anesthesiology
MAY 5, 2016
Myocardial Injury Within Month of Surgery Is Third Leading Cause of Death


Cleveland and Hamilton, Ontario—Among inpatients aged 45 years or older having noncardiac surgery, 9% will experience myocardial injury within the 30 days after the procedure. About 80% of these injuries are clinically silent, detected only by troponin elevation. Mortality, however, is nearly identical for symptomatic and asymptomatic troponin elevations. Within 30 days of surgery, 10% of patients with elevated troponin concentrations will die, making myocardial injury the leading cause of postoperative death and the third leading cause of death overall in the United States.
“When mean arterial pressure [MAP] decreases below a threshold of about 65 mm Hg, the risk of myocardial injury starts to increase,” said Daniel I. Sessler, MD, the Michael Cudahy Professor and Chair of the Department of Outcomes Research at the Cleveland Clinic. “By the time MAP reaches 55 mm Hg, it takes just one minute to significantly increase the risk of death. The deeper and longer the hypotension, the greater the risk. These observations are consistent with the theory that supply/demand mismatch contributes to postoperative myocardial injury—although it is not a major cause of nonoperative myocardial infarctions (MIs).”
“The combination of patient characteristics, anesthetic drugs and intraoperative bleeding … [contributes] to hypotension and resulting perioperative myocardial infarction,” P. J. Devereaux, MD, PhD, told Anesthesiology News. “Some MIs that occur within the perioperative setting are due to [intraoperative] supply/demand mismatch,” he said. Dr. Devereaux is a university scholar and professor in the Departments of Clinical Epidemiology & Biostatistics and Cardiology at McMaster University Health Sciences Centre, in Hamilton, Ontario.
“Interestingly,” Andrea Kurz, MD, noted, “few myocardial infarctions occur intraoperatively. They happen during hospitalization, most within two to three days after surgery,” she said. “It might be that intraoperative hypotension causes myocardial injury that just doesn’t become apparent until one to three days after surgery. Or it might be that patients who become hypotensive during surgery also become hypotensive after surgery, and that is when the injury occurs.” Dr. Kurz is professor and chair of the Department of General Anesthesiology at the Cleveland Clinic, where she is also vice chair of the Department of Outcomes Resear

 

[BLADEMDA]

Whether you agree with any of my posts or not isn't the point. My point is that the overwhelming body of evidence strongly suggest that severe hypotension for any length of time (more than 2-3 minutes) is poorly tolerated in patients especially those at risk. I firmly believe that most "experts" will review your anesthetic record and come to the same conclusion regarding your BP management intraoperatively. For those of us that practice in the USA I strongly suggest maintaining a "reasonable" BP intraop for your surgical patients. For me, that means the use of LR and pressors to maintain a MINIMUM MAP above 65 for healthy, younger patients and a MINIMUM MAP above 75 for the elderly. I tend to be cautious and typically aim for a slightly higher MAP than some on this board.

 

[nimbus]

Whether you agree with any of my posts or not isn't the point. My point is that the overwhelming body of evidence strongly suggest that severe hypotension for any length of time (more than 2-3 minutes) is poorly tolerated in patients especially those at risk. I firmly believe that most "experts" will review your anesthetic record and come to the same conclusion regarding your BP management intraoperatively. For those of us that practice in the USA I strongly suggest maintaining a "reasonable" BP intraop for your surgical patients. For me, that means the use of LR and pressors to maintain a MINIMUM MAP above 65 for healthy, younger patients and a MINIMUM MAP above 75 for the elderly. I tend to be cautious and typically aim for a slightly higher MAP than some on this board.

I agree. I just haven’t found LR boluses to be effective in treating hypotension unless you give at least a liter.

 

[nimbus]

You’re thinking about NS.

No I incorrectly calculated the sodium content of LR when I calculated it off the label of a bag. @vector2 corrected my mistake. A liter of LR has about 3g elemental sodium and 6gm NaCl. NS has slightly more but not 9g.

Not that it’s clinically significant but food for thought. A liter of LR has 9gm of sodium. That’s the equivalent of 9 Big Macs.

Mmmmm, check my math :

1 meq of (elemental) sodium = 23 mg

LR = 130 meq/L * 23 mg/meq = 2990 mg/L

Ahhhh you’re right. I didn’t account for the chloride and the lactate when I read the label. I should have said 6gm of NaCl/liter.

View attachment 309830

 

[fakin' the funk]

One of the reasons the PPV is low could be because one needs (much) more than 8 ml/kg of VT to see reliable PPV changes, among others. Typical 70 kg IBW patient is run at 450-500 ml of VT nowadays, at least by the good anesthesiologists.

I guess you'll just have to believe that I do it correctly ‍♂

Incidentally - on the topic of PPV - venoconstrictors will lower PPV.

Whether you agree with any of my posts or not isn't the point. My point is that the overwhelming body of evidence strongly suggest that severe hypotension for any length of time (more than 2-3 minutes) is poorly tolerated in patients especially those at risk. I firmly believe that most "experts" will review your anesthetic record and come to the same conclusion regarding your BP management intraoperatively. For those of us that practice in the USA I strongly suggest maintaining a "reasonable" BP intraop for your surgical patients. For me, that means the use of LR and pressors to maintain a MINIMUM MAP above 65 for healthy, younger patients and a MINIMUM MAP above 75 for the elderly. I tend to be cautious and typically aim for a slightly higher MAP than some on this board.

While there's no evidence to support MAP 75 target in really any population, I think the important idea here is that there is a time dependent "dose" of hypotension associated with poor outcomes and it happens below a MAP of 65.

Incidentally, to keep an elderly or decrepit person with lots of comorbid conditions at a map of 75 under proper depth of general anesthesia is going to require vasopressor most of the time.

 

[BLADEMDA]

I guess you'll just have to believe that I do it correctly ‍♂

Incidentally - on the topic of PPV - venoconstrictors will lower PPV.


While there's no evidence to support MAP 75 target in really any population, I think the important idea here is that there is a time dependent "dose" of hypotension associated with poor outcomes and it happens below a MAP of 65.

Incidentally, to keep an elderly or decrepit person with lots of comorbid conditions at a map of 75 under proper depth of general anesthesia is going to require vasopressor most of the time.

I find that a little bolus push of ephedrine and phenylephrine is often enough to keep the MAP above 75. I also find that a spontaneously breathing patient can tolerate higher amounts of volatile anesthetic than an intubated patient. But, intubated patients only need muscle relaxant and 0.7 MAC of agent to undergo surgery safely. Many midlevel providers exceed that 0.7 MAC by at least 50% or more. These days we have sugammadex readily available as well which makes the use of muscle relaxants even safer.

As for the evidence of MAP of 75 I have a question for you. If you use a 30% reduction in baseline MAP as severe hypotension then what MAP are you likely to see in an elderly patient population in the preop area? In my neck of the woods I see a lot of chronic hypertension in the preop area in a range that some of you may cancel the case. Thus, a MAP of 75 still represents a significant reduction in BP from baseline.


"The AAGBI recommend avoiding >20 % drop in systolic blood pressure (Griffiths et al. 2014), whilst drops of >30 % mean arterial pressure (MAP) and MAP <55 mmHg have been associated with stroke, myocardial ischaemia, and kidney injury (Bijker et al. 2009; Walsh et al. 2013) "

 

[MoMoGesiologist]

I find that a little bolus push of ephedrine and phenylephrine is often enough to keep the MAP above 75. I also find that a spontaneously breathing patient can tolerate higher amounts of volatile anesthetic than an intubated patient. But, intubated patients only need muscle relaxant and 0.7 MAC of agent to undergo surgery safely. Many midlevel providers exceed that 0.7 MAC by at least 50% or more. These days we have sugammadex readily available as well which makes the use of muscle relaxants even safer.

As for the evidence of MAP of 75 I have a question for you. If you use a 30% reduction in baseline MAP as severe hypotension then what MAP are you likely to see in an elderly patient population in the preop area? In my neck of the woods I see a lot of chronic hypertension in the preop area in a range that some of you may cancel the case. Thus, a MAP of 75 still represents a significant reduction in BP from baseline.


"The AAGBI recommend avoiding >20 % drop in systolic blood pressure (Griffiths et al. 2014), whilst drops of >30 % mean arterial pressure (MAP) and MAP <55 mmHg have been associated with stroke, myocardial ischaemia, and kidney injury (Bijker et al. 2009; Walsh et al. 2013) "

What’s the lowest MAP you will go in your elderly hypertensives for their ortho surgery when surgeon asks for “controlled hypotension”? Do you ever tell the surgeon no, and how?

 

[vector2]

Do you ever tell the surgeon no

Yes.

, and how?

"Umm....no."*








* "but I'll be glad to give some TXA and send a type and match"

 

[BLADEMDA]

What’s the lowest MAP you will go in your elderly hypertensives for their ortho surgery when surgeon asks for “controlled hypotension”? Do you ever tell the surgeon no, and how?

Most ortho surgeons are very reasonable. I explain the rationale for keeping BP MAP above 75. For those that complain I let them bitch but still keep the BP where I think it is appropriate. That’s why I like arterial lines. I can move the transducer to make the BP appear lower than it is. This makes everyone in the room happy

 

[fakin' the funk]

I find that a little bolus push of ephedrine and phenylephrine is often enough to keep the MAP above 75. I also find that a spontaneously breathing patient can tolerate higher amounts of volatile anesthetic than an intubated patient. But, intubated patients only need muscle relaxant and 0.7 MAC of agent to undergo surgery safely. Many midlevel providers exceed that 0.7 MAC by at least 50% or more. These days we have sugammadex readily available as well which makes the use of muscle relaxants even safer.

As for the evidence of MAP of 75 I have a question for you. If you use a 30% reduction in baseline MAP as severe hypotension then what MAP are you likely to see in an elderly patient population in the preop area? In my neck of the woods I see a lot of chronic hypertension in the preop area in a range that some of you may cancel the case. Thus, a MAP of 75 still represents a significant reduction in BP from baseline.


"The AAGBI recommend avoiding >20 % drop in systolic blood pressure (Griffiths et al. 2014), whilst drops of >30 % mean arterial pressure (MAP) and MAP <55 mmHg have been associated with stroke, myocardial ischaemia, and kidney injury (Bijker et al. 2009; Walsh et al. 2013) "

Salmasi paper from Anesthesiology 2017 suggests 20% reduction from baseline is similar to MAP 65 to use clinically as a threshold below which risk increases.

That said, patient with a known severe lesion (untreated coronary stenosis, spinal cord perfusion, untreated carotid stenosis etc) gets MAP > 75-80 from me. Such patients are somewhat rare so the paper above doesn't reflect this population.

 

[BLADEMDA]

Salmasi paper from Anesthesiology 2017 suggests 20% reduction from baseline is similar to MAP 65 to use clinically as a threshold below which risk increases.

That said, patient with a known severe lesion (untreated coronary stenosis, spinal cord perfusion, untreated carotid stenosis etc) gets MAP > 75-80 from me. Such patients are somewhat rare so the paper above doesn't reflect this population.

So, for patients with known severe hypertension (below your cancel threshold) and elderly (over 70) what MAP do you want to target? I would argue that MAP of 75-80 is the right MINIMUM MAP for this group of patients. These of the type of people I see most of the time in my practice.

 

[deleted162650]

MAP > age.

 

[Hork Bajir]

Curious what people are using as a “cancel threshold” for preop BP? My perspective might be skewed because my patient population is mostly vasculopaths, who have often had one or more of their antihypertensives held on the day of surgery... But seeing preop SBP>190 is unfortunately not a rarity in my world, and if I canceled all of these patients I would be canceling quite a few surgeries. My usual response to preop HTN is to shrug and say that propofol is a great antihypertensive.

Of course, I understand that there is subtlety to the situation, and I would probably look at those numbers differently if I was working in an outpatient surgery center

 

[Urzuz]

Curious what people are using as a “cancel threshold” for preop BP?

What time of day are we talking about?

 

[vector2]

Curious what people are using as a “cancel threshold” for preop BP? My perspective might be skewed because my patient population is mostly vasculopaths, who have often had one or more of their antihypertensives held on the day of surgery... But seeing preop SBP>190 is unfortunately not a rarity in my world, and if I canceled all of these patients I would be canceling quite a few surgeries. My usual response to preop HTN is to shrug and say that propofol is a great antihypertensive.

Of course, I understand that there is subtlety to the situation, and I would probably look at those numbers differently if I was working in an outpatient surgery center

Usually DBP > 110. But I almost never cancel unless the pt is symptomatic/has active, ongoing organ injury or unless the procedure is high risk involving huge hemodynamic swings/fluid shifts etc.

 

[coffeebythelake]

The sicker they are, the more comorbdities they have, the closer I want to keep their hemodynamics where they normally live.

 

[drmwvr]

The sicker they are, the more comorbdities they have, the closer I want to keep their hemodynamics where they normally live.

Where do you find that number? An often repeated phrase, but what it comes down to is the blood pressure the nurses in pre-op measure. Odds are nowhere near the mean they "live" at averaged over 24 hrs. Probably significantly higher I'd think...