Rick Hines has spent the last 20+ years in service to his country much of it deployed to combat zones and other unstable, austere environments and is dedicated to improving SOF Medicine. He made it a point to spend a fair amount of time with surgical teams when possible and has gained quite a bit of real world knowledge that we hope to pass on to a wider audience here. He was formerly an SF Medical Sergeant turned Team Sergeant before going on to work as the 3rd SFG(A) Senior Enlisted Medical Advisor, the Unites States Army Special Forces Command (USAFC) SEMA and within the USASOC Surgeon’s Office. Just so that there isn’t any confusion, here is the official Analgesia and Sedation guidelines from the PFC working Group.
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My name is Rick Hines and today I would like to speak with you about sedation and anesthesia in the prolonged field care, or austere environment. So who the heck is Rick Hines and what gives him the right to talk about anesthesia? I spent 29 years in the Army, and a bit over 21 of that as an SF guy, an 18D and a team sergeant. I’ve had a few deployments, combat and otherwise. I’ve been sent to remote areas, seen some crazy diseases, a bit of trauma, and I’ve even had my feelings hurt a time or two. I retired at the end of 2016 and have been a medical instructor ever since. What I will be talking about are techniques, and some may be controversial. Please defer to your medical protocols. My goal is to introduce some ideas from my experience to drive further discussion. Some of these techniques vary from the Prolonged Field Care Clinical Practice Guidelines. This is a knuckle dragger’s perspective, having the benefit of working with folks far smarter than I am. All of the opinions in this podcast are mine and don’t represent anyone else.
So what is anesthesia? According to Merriam-Webster, it is the loss of sensation, with or without the loss of consciousness.
What is analgesia? Again, Merriam-Webster says the insensibility to pain without loss of consciousness.
What is amnesia? A loss or a gap in memory.
What is akinesia? The loss or impairment of voluntary activity of the muscles.
Why do we need to know this? There are times when we want to sedate our patient to alleviate anxiety, but we want them to be able to protect their own airway. Other times, we may want them on a surgical plain. This is anesthesia. If we are doing a painful procedure, we will want to alleviate the pain. This is analgesia. If they are hemodynamically unstable, we may want them to have a bit of a painful stimuli to keep their VS up. If you do this, you want something to take away the memory of the painful event. This is amnesia. During surgery, we don’t want the patient to move. This is akinesia. This is all part of anesthesia.
I would like to introduce a term that is relatively new to me, but some of you may be familiar with: autonomic stability. To explain this remember that the autonomic nervous system has two components: the sympathetic nervous system (fight or flight); and the parasympathetic nervous system (rest and digest). Both of these systems work together to give the vascular system a certain tone. This is why your heart rate and blood pressure (BP) are about the same whether you’re standing or laying down. If the parasympathetic discharges, we see a dramatic hypotension with bradycardia. If the sympathetic discharges, we see tachycardia and hypertension. Autonomic lysis is making sure neither of these two systems discharge. This is important, especially with a trauma patient. The sympathetic is what is keeping them alive. If we are too heavy handed with our induction dose (including ketamine) we can cause this system to discharge, losing our systemic vascular resistance (SVR) leading to pulseless electrical activity (PEA). Not cool. So tread as lightly as possible with induction.
Let’s back up a bit. I would like to speak about the drugs some of us use. Most of us carry Ketamine 50mg/1ml, Midazolam (or Versed in the U.S.) 5mg/ml, and some carry Fentanyl injectable (not just the lollipop) 50mcg/ml. IV Propofol is a great drug, and you would think it is right up our alley. It has a rapid onset (less than a minute) and a short duration (3 to 10 minutes). However, many of our patients are hemodynamically unstable, and Propofol can drop their BP pretty quickly. This is a drug that requires someone to closely monitor the patient. As we are often both the surgeon and anesthesiologist (I use these terms loosely), it would be dangerous and cavalier to use this drug without a competent person solely running anesthesia. Plus, the manufacturer recommends storage at 40-72 degrees Fahrenheit, and we are often outside of this range. And once you tap a container of Propofol, you have 12 hours to use it. Bacteria grows like crazy in this stuff.
At times we have Vecuronium 10mg/ml (or Rocuronium or Succinylcholine) for RSI (rapid sequence intubation). Succinylcholine is short acting, which is great for us, but I prefer Vecuronium as I can use it for more than just RSI. You can use it for ventilator compliance with a patient with blast lung, or pulmonary contusion (remember, it paralyzes the diaphragm so something or someone needs to breath for them). Ventilators are another podcast. Rocuronium requires refrigeration or it loses its potency, so I don’t recommend carrying that. If you are carrying Vec, make sure you have your reversal agents: Neostigmine 0.03-0.07mg/kg IV and either Glycopyrrolate or Atropine 0.4-0.6mg IV. I prefer the Atropine, since it can be used for multiple conditions, such as: nerve agent antidote (as is Midazolam), pre-surgical medication (to dry secretions and increase heart rate), and it has cardiac applications (treatment for bradycardia and PEA). Sugammadex is the current reversal agent for Vec and Roc in hospitals. If you can get this, it is also a great option. You can administer this at 2-4mg/kg IV. A good rule of thumb, if you used 20mg of Vec for RSI, I would recommend 4mg/kg of Sug as a reversal. Also, since we are carrying opioids, we need to make sure we have Narcan 0.4-2mg. You may need to repeat every 2 to 3 minutes.
Then there are your local and regional anesthesia agents such as Lidocaine 1% 10mg/ml, Lidocaine 2% 20mg/ml, Marcaine 0.25% and Ropivicaine for long term blocks. You may have noticed a trend with the Lidocaines. 1%=10mg/ml. 2%=20mg/ml. This makes the math a little easier. Finally, we should all have Zofran available (PO and IV/IM). I won’t get much into antibiotic or fluid therapy, as that would keep us here way past O’beer 30.
Let’s set up a scenario. You have an injured patient in significant pain. Evacuation time is unknown. Let’s not list imaginary wounds and let’s assume that we are Johnny trauma and all of the trauma treatments were done splendiferously. OTFC (or Fentanyl lollipop) and TXA, if applicable, have been given. Now we have some time to come up with a pain management plan.
We’ll start with anesthesia in a stick. With the concentrations mentioned earlier, take a 5cc syringe and draw up 150mg of Ketamine, 5mg of Midazolam, and 50mcg of Fentanyl. That’s 3cc, 1cc, and 1cc. For sedation, administer 2cc IV, and titrate to nystagmus. Then give 1cc PRN. Consider doubling the dose if you go IM or IN. I recommend giving Ondansetron (or Zofran) at this point (4mg IV over 2 to 4 minutes, or IM) as Ketamine makes many people yack especially when they are coming out of anesthesia. Give it before you want your patient to wake up. For RSI, give the entire 5cc IV, then follow with a paralytic, such as Vecuronium, 20mg IV. The onset will be less than 60 seconds, and the duration should be about 40 minutes or more. Some have said “what if you RSI, then can’t get the airway”? If we are going to RSI a patient, we are committing to securing their airway. One way or another, the airway must be secured. Worst case, we do a cricothyrotomy. When securing the airway, the quicker the better. I know that some say to slow push Ketamine over 60 seconds to prevent transient apnea or respiratory depression. Remember to abide by your treatment protocols. I have never seen apnea last more than 30 seconds when administering Ketamine as a normal IV push. Remember to always monitor your patient’s airway, lungs, pulse, and oxygen saturation at a minimum. Treat accordingly.
I realize that mixing medications in the same syringe or IV bag may be controversial to some. There aren’t many studies that have shown the safety and/or efficacy of mixing medications. You can reference “Total intravenous anesthesia for military surgery” by J. Restall et al, 1988 for one. Some drugs come premixed: Ketofol. In a perfect world, I would rather run each medication on its own, so if there are any reactions, or a dose needs to be adjusted, I can adjust one without adjusting them all. With that being said, sometimes we have to do things in a less than perfect world. All of the drug mixtures I will discuss I have seen used multiple times.
Before we start anesthesia, we have to be able to monitor our patient. The minimum monitoring capability you need is respirations, heart rate, BP, and pulse oximetry. Best would be all of the above with a 12 lead, end tidal CO2, and capnography. Oh yea, record the VS so you can track trends. A technique that I recently learned about is to look at the respiratory rate to determine if the unconscious patient needs pain medication. If you see their respiratory rate rise above 12 per minute, they may need some pain medication. Which pain medication will depend on what you have, and how hemodynamically stable your patient is.
Ok. We just sent this person for a ride. What kind of ride is this? Let’s break down our drugs. Ketamine is a dissociative in larger doses. Some say that the patient knows what is going on, but just doesn’t care. I don’t really buy that. That sounds more like an opioid response. If you give an anesthesia dose, this person is going on a ride. I’m talking riding the dragon through the outer quadrants of space and time…an out of body experience. Think Timothy Leary and LSD. “Turn on, tune in, drop out”. (you younger folks will need to google it). At higher doses, what kind of trip is the patient taking? That depends on their state of mind going into the trip. If I’m administering Ketamine, this patient is probably having a bad day (i.e. they have had a significant traumatic event, or at least have had their feelings hurt). So we can expect a bad trip. Here there be monsters, Aarrgghh. With lesser doses their sedative hypnotic state is influenced by their sensory input. Their visual, auditory, and sense of smell will influence this state. They can follow basic commands. I have heard it described as being in another dimension, but having our dimension bleed over into it. Just keep in mind, that’s why we disarm before administering Ketamine. This is where the other drugs come in. Midazolam is to help guide the patient to their happy place. It also helps alleviate the muscle rigidity common with Ketamine. But this will not provide much pain relief. The Fentanyl is to aid in treating the pain. It is short acting, but works well with Ketamine and reduces the amount of opioid and ketamine you need to use to control pain. Less opioids, less adverse opioid effects – especially respiratory depression, apnea, and/or a dropping the patient’s BP. As a lazy medic, anything that makes my life easier is great by me. Plus, if it is better for the patient, BONUS!
So now what? We have this person down and have their pain under control. How do we maintain that? We can keep bolusing as needed, but that gets tiresome and is more work for us. So we might as well do like real medical professionals and run a drip (or intravenous anesthesia).
Let’s start small. If you are within that one hour or so bubble, you can use the one hour bag. Remember, in a perfect world you would administer these through their own lines so that you can adjust drip rates accordingly. But our world has just become a surrealistic nightmare, so we will keep this simple…for now. Still, make sure you have at least two lines, IV or IO. During transport, you may lose one, and remember, Murphy is always out there. In a 50cc NS bag, inject the anesthesia in a stick. In other words: 150mg Ketamine, 5mg Midazolam, and 50mcg of Fentanyl. Using a 15gtts admin set, run 0.5 to 2.0mg/kg/hour. If you have trouble getting 50cc bags, use what you can get and do the math for that volume. I know. Math. Use your favorite drip rate app. For an 80kg patient, run 4 drop every 60 seconds for the low end, and up to about 12 drop per 60 seconds as your max. I recommend piggybacking this on a line of NS run TKO (to keep open). IV catheters often clot off if you run them this slow. Remember, you knocked your patient down to the level you wanted with the anesthesia in a stick. This drip is to maintain that level. So the dosing rang goes from sedation to surgical plain.
At this point we would run our IV antibiotic. Most of us use 1 gram of Invanz per day, but Ancef is a common pre-surgical antibiotic. Choose whatever is appropriate for your patient. Follow your treatment protocol. This would also be a good time to run your second dose of TXA, if your patient qualified for a first dose. And keep your patient warm. I don’t care how warm the ambient temperature is. If your patient is shocky, they are probably cold. A warm patient is usually a perfusing patient. The medications you give your patient will be more effective if the person is warm. Also, this is the part of the lethal triad that we can most easily effect. Warm the fluids you are running and actively warm your patient. This will make your life easier, and, oh yea, it is good for the patient. Remember, a Surgeon focuses on the procedure. When acting as an Anesthesiologist, you are responsible for staying focused on the entire patient. However long, you are responsible for their wellbeing.
Back to the scenario. So, what if we are someplace more remote with a longer Evac time? We can mix up a five hour bag. Take a 250cc NS bag and add 750mg of Ketamine, 25mg of Midazolam, and 250mcg of Fentanyl. Run it at the same rate as the one hour bag if you are using a 15gtts/ml admin set. Don’t forget to re-dose the Zofran every 8 hours. So far, not too complicated, right?
Remember that using local or regional anesthesia can reduce your need for sedation and/or anesthesia. It can also reduce or negate the need for opioids. Using either ultrasound guided, and/or a nerve stimulator (stimiplex), or simply anatomically placing regional anesthesia can be very effective. A multimodal approach is strongly recommended. Remember to calculate the max dose for your patient, and don’t go past it (i.e. Lidocaine 1% without epinephrine for a 70kg patient. At 4.5mg/kg, your max is 315mg). You can even dilute whatever agent you decide to use. A 50% solution is often just as effective. Volume is more important than concentration. Especially if you don’t do this every day, and your placement may be a bit off. If you have both the Stimiplex and an ultrasound, I would get placement with the Stimiplex, and confirm with the ultrasound. This will save your supplies, make your life easier, oh, and yes, it will make the patient a lot more comfortable.
All of this talk about anesthesia, but we haven’t spoken about what to do if the patient is either hemodynamically stable or unstable, and how this relates to our pain management. Our real concern with an unstable patient is the Fentanyl. This will drop our patient’s BP and respiratory rate. In a shocky patient, this causes more work for us. No me gusta trabajar. For this scenario, remember, we are Johnny trauma, so all compressible hemorrhage is controlled, however, our patient is still decompensating (increased heart rate, decreased respiratory rate, BP, oxygen saturation). As part of our damage control resuscitation, we are using fluids to try to maintain our patient’s MAP (mean arterial pressure) around 65. Like I said before, I’m not going to get into fluid therapies. Give your patient the appropriate fluid for their condition (crystalloids, colloids, or blood products). Fluid therapy is another podcast. The formula for calculating MAP is 2 x the diastolic + the systolic BP, divided by 3. For us simple trauma monkeys without fancy equipment, this means the patient is A/O x3 (or alert and oriented to person, place, and time), with a radial pulse and warm hands and feet. A MAP of 65 allows perfusion of the organs (brain, lungs, heart, and kidneys ect.) theoretically without resuscitating to bring the pressure high enough to blow clots. At least that’s the hope. With this patient, I strongly recommend running your drugs in separate lines. With a good regional block, you may only need the Ketamine drip.
Now, with a hemodynamically unstable patient, we can administer Fentanyl in small boluses, 12.5mcg. This way we can titrate to the patient’s MAP. Basically we will resuscitate our patient till their MAP is 65, then give a slow bolus of Fentanyl. If their MAP drops, fluid resuscitate to bring the MAP back up to 65. If the patient is in pain, give the next bolus of Fentanyl. Continue as necessary until the patient no longer decompensates when being administered Fentanyl, or you turf them off. Another technique is to give your patient a Ketamine bolus in addition to their Ketamine drip. Many of us like this technique because it is less likely to drop the Patient’s MAP. Remember, Damage control resuscitation is meant to deliver our patient as hemodynamically stable as possible to surgery. This will give them the highest possible chance of surviving the surgery, and making a recovery.
What if I have more patients than I have meds for? How can I stretch my supplies? I would look at what you are using the drug for and how your patient is responding. Ketamine is our main drug. It is the last one I would look to skimp on. One thing you can consider is half dosing your Midazolam. Or better yet, why are we using Midazolam? We want to put them in their happy place, so they have a good trip and we avoid re-emergence syndrome, and some amnesia. So we can give a dose of Midazolam when we knock the patient down, and another when we wake them up, or after a painful procedure. Another idea is to cut back on the Fentanyl and see how your patient tolerates the dose reduction. Or better yet, if you have a good regional you can do without Fentanyl. If your patient can swallow PO meds, or if they have an NG tube, you can give them some Percocet or whatever PO pain medications you have, to combine with your Ketamine. You can also give an NSAID with acetaminophen and get an effect comparable to Percocet. Just use with caution in a hemodynamically unstable patients as NSAIDs can effect coagulopathy. Be creative to save your injectables for when things get worse (as they often do).
What if you need to perform a surgical procedure, or other painful treatment, on your patient? If they are riding fine on Ketamine and a regional block, you may want to give a bolus of Midazolam and/or Fentanyl just prior to performing the painful procedure. If you do need to knock your patient down to a surgical plain, try to minimize their time spent there. Patients that are intubated and kept on a surgical plain for long periods tend to have poor outcome. Doctors without borders published a study on this. If you screw up your patient, you lose all of your cool points. Don’t lose your cool points.
So, after all of this nerd talk, let me mention medical supplies. Let’s say we want to be prepared to treat two patients. One is none, and two is one, and all of that nonsense. In other words, if you have one and it is lost, you have none. Always plan for contingencies. This is a material and labor intensive event that you need to plan and train for. To hold a patient for 24 hours, you will need 5 of the 5 hour bags. For two patients running 24 hours, you will need 10 of the 5 hour bags. If you expect your evacuation to take longer, you will need more. I cannot emphasize enough that you need to plan ahead and have adequate supplies.
To wrap this nerd fest up, remember that long term pain management is both supply and labor intensive. It requires planning and training. We all like to imagine ourselves taking care of our teammates when we are at our best. Now imagine doing this when you are exhausted, both physically and emotionally. Imagine that you are injured yourself. Plan and train for those bad days and you can make them a little less bad. And remember the three SF rules: Always look good; never get lost; and if you get lost, at least you look good. Good luck.