Flush with 10–20 mL of normal saline after each intravenous medication during cardiac arrest, and follow the manufacturer's flush volume for any drug whose label specifies one. The 2015 American Heart Association Advanced Cardiovascular Life Support update puts the epinephrine flush at 20 mL, while the 2010 guidelines used 10 mL for the same step. That shift, and the four antiarrhythmic drugs that ride along with it, is what most single-number answers miss.
During a code, the flush isn't housekeeping. It's a delivery mechanism. A medication pushed into a peripheral IV without a flush can sit in the tubing while the team moves to the next drug, the next rhythm check, or the next compression cycle. The volume matters less than the act, but the volume is what examiners and protocol audits ask for, so it's worth getting right on both counts.
What 20 Milliliters Actually Delivers That 10 Does Not
The 2015 AHA ACLS guidelines changed the epinephrine administration note from "follow with a 10-mL flush" to "follow with a 20-mL flush of IV fluid." The same document lists amiodarone, lidocaine, and magnesium sulfate as drugs given during cardiac arrest, and each carries its own post-dose instruction. The number you give on a written test is usually 20 mL, because that is the figure attached to the drug administered most often in a code.
Twenty milliliters is roughly the dead space of a standard peripheral extension set plus the catheter lumen, doubled. Ten milliliters will clear a short, well-primed line in a patient with brisk venous return. During CPR, venous return is not brisk. Chest compressions generate a fraction of normal cardiac output, and anything pushed slowly into a quiet circulation moves slower still.
There is a second reason the volume climbed. Many code teams now use a 100 mL bag of normal saline as the flush source through a three-way stopcock rather than a pre-filled syringe. Once that bag is spiked, the "how many milliliters" question becomes a flow question, and a full 20 mL squeeze takes about two seconds. The number in the guideline is a floor for line clearance, not a ceiling for fluid administration.
The distinction between the two figures is not a meaningful clinical debate in most codes. Both clear a peripheral line. The 20 mL figure is the one printed in the current AHA guidance and the one that matches the epinephrine note reprinted in the 2020 focused update on adult cardiac arrest. If you are documenting a code or answering an exam item, cite 20 mL for epinephrine and note the label-specific volumes for everything else.
Why the Flush Volume Is Not the Same for Every Code Drug
Four drugs appear in nearly every adult cardiac arrest algorithm, and each carries a different post-administration instruction. Epinephrine says flush with 20 mL. Amiodarone, lidocaine, and magnesium sulfate say to follow with a flush of normal saline, but the volume is not stated in the algorithm text — it lives in the drug label or the institutional protocol. The AHA ACLS manual and the 2020 guidelines treat the flush as part of the administration step rather than as a separate procedure.
Amiodarone is the drug that most rewards a careful flush. The label warns about local reactions when the drug is given through a peripheral line, and a generous saline follow-through dilutes what remains in the vein. The same logic applies to magnesium sulfate in torsades de pointes, where a concentrated bolus without follow-through can irritate a small forearm vein. Lidocaine is more forgiving but still gets flushed as a matter of routine.
The practical rule that hospitals write into their code carts is simpler than the pharmacology: push the drug, push the flush, then chase with a second small flush if the line is long. That two-flush habit exists because the first flush mixes with drug in the line and the second moves the mixed volume into the circulation. A single 20 mL flush accomplishes the same thing in most peripheral lines; a central line or an extended set may need the second pass.
If the drug is given through a central venous catheter, the dead space can exceed 5 mL on its own before any patient circulation is involved. Twenty milliliters still clears the lumen of a typical triple-lumen catheter, but the fluid arrives into a large vessel where dilution is rapid. The volume question gets easier on a central line and harder on a fragile peripheral one, which is why protocols tend to specify a range rather than a single figure.
The Four-Step Sequence to Push a Drug and Flush in a Running Code
The flush does not happen in isolation. It sits between two other actions, and the order is what determines whether the dose reaches the patient. Here is the sequence as it runs in a real code, drawn from the AHA ACLS drug administration guidance and standard code-cart practice.
1: Confirm the drug and dose aloud. Epinephrine 1 mg of the 1:10,000 concentration is the default adult cardiac arrest dose, repeated every 3 to 5 minutes. 2: Attach the syringe to the closest port to the patient, not the port at the end of the longest tubing segment. The flush volume you plan must cover the distance from that port to the vein. 3: Push the drug, then push 10–20 mL of normal saline at the same port without disconnecting. Keep compressions going throughout. 4: If the line is long or the catheter is central, follow with a second small flush to move the mixed volume clear of the tubing.
Failure handling matters here. If the IV has a blood return that stops during the flush, suspect infiltration or a positional catheter and move to the next access. During a code, that usually means a second peripheral line or an intraosseous route. The intraosseous flush volume is a separate question: the AHA guidance for IO drug administration calls for a saline flush after each drug, and many protocols use 10 mL for the IO before and after the dose to confirm the marrow cavity is patent.
Two additional failure modes are worth naming. A flush given too fast through a small vein can extravasate and leave the dose in the tissue; a flush given through a stopcock that is turned the wrong way sends saline into the bag rather than the patient. Both are common in simulation and both are fixed by one habit: say the port and the direction out loud before you push.
The 10 mL Figure Isn't Wrong — It's a Different Edition
Exam questions built from older ACLS editions still expect 10 mL for some steps. The 2010 AHA guidelines used a 10 mL flush after epinephrine, and many test banks and hospital policies written before 2016 still carry that number. A nurse trained in 2012 and a nurse trained in 2022 can both be right and still disagree, which is the single most common source of confusion around this keyword.
The current guidance is the 2015 ACLS update and its 2020 focused revision. Both attach 20 mL to epinephrine. If your institution's policy says 10 mL, the policy is older than the guideline and probably should be updated, but the bedside answer during a code is to follow the policy of the team you're working with and flag the discrepancy afterward. The clinical difference in a peripheral line is small; the documentation difference in an audit is not.
Regional variation exists as well. European Resuscitation Council guidance discusses drug administration timing and route but does not attach a single flush volume to the epinephrine step in the way the AHA does. That means a European-trained clinician and an American-trained one may genuinely be answering different questions. If you are studying for a certification, use the volume from the certifying body whose exam you are sitting.
The volume also shifted for reasons that have nothing to do with the drug. Pre-filled saline syringes became standard code-cart stock after 2015, and a 10 mL pre-filled syringe was often the only size on the cart. The change to 20 mL tracked the wider availability of larger flush syringes and 100 mL bags as flush sources, not a new pharmacokinetic finding. That's a useful thing to know when someone asks why the number moved.
A Worked Comparison: Flush Volume by Access and Drug
The table below lines up the four access routes and the four common code drugs against the flush volume each situation calls for. Values for epinephrine come from the AHA 2015 ACLS update and the 2020 focused update on adult cardiac arrest. Drug-label volumes for amiodarone, lidocaine, and magnesium come from the manufacturer's prescribing information, which varies by product; confirm the specific product on your cart against its label.
| Access route | Epinephrine 1 mg | Amiodarone 300 mg | Lidocaine 1–1.5 mg/kg | Magnesium 1–2 g (torsades) |
|---|---|---|---|---|
| Peripheral IV, short set | 20 mL | 20 mL, then second 10 mL if long | 20 mL | 20 mL |
| Peripheral IV, extended set | 20 mL plus second 10 mL | 20 mL plus second 10 mL | 20 mL plus second 10 mL | 20 mL plus second 10 mL |
| Central venous catheter | 20 mL | 20 mL | 20 mL | 20 mL |
| Intraosseous | 10 mL before and after dose | 10 mL before and after dose | 10 mL before and after dose | 10 mL before and after dose |
Read the table as a set of floors, not ceilings. The 20 mL figure is the minimum that clears a peripheral line in a low-flow circulation; a team using a 100 mL bag as a flush source will routinely give more. The IO row is the one that surprises people: the pre-dose flush is there to confirm the marrow cavity is patent, and the post-dose flush moves the drug out of the marrow. Skipping the pre-dose flush is the most common IO administration error in simulation.
The amiodarone row is where the table earns its keep. The label's warning about peripheral administration is the reason many protocols add a second flush after the first. A single 20 mL push dilutes the drug in the line, but the mixed volume still enters the vein at a concentration the label flags. The second flush is cheap and the vein you save may be the only access you have.
What the Flush Does to the Drug's Arrival at the Heart
A medication pushed into a peripheral vein during CPR faces a circulation that is being generated by compressions at roughly 100 to 120 per minute. Venous return is a fraction of normal, and the drug's trip from forearm to right atrium depends on whatever forward flow the compressions create. The flush is the only tool the team has to shorten that trip without stopping compressions.
There is a measurable consequence. Epinephrine's onset in a perfusing patient is roughly one to two minutes; in a patient in cardiac arrest, the observed effect on rhythm and return of spontaneous circulation is delayed and variable, and the guidelines schedule repeat dosing at 3 to 5 minutes rather than titrating to a visible response. The flush doesn't change the pharmacology, but it does change how much of the dose reaches the central circulation in the first pass.
Central lines change the math again. A drug given through a central catheter enters the superior vena cava or right atrium almost directly, and the flush's job is only to clear the catheter lumen. That is why central access is prized in a code despite the insertion time: the delivery problem shrinks. Peripheral access with a good flush is the compromise most teams accept because it is faster to obtain.
The flush also has a dilution effect that matters for amiodarone and magnesium. Both are concentrated solutions that irritate vein walls, and the saline follow-through reduces the concentration at the vein wall. The mechanism is simple dilution, and it is the reason the label instructions for those drugs include a follow-through rather than stopping at the drug push. It is not a substitute for central access when the drug is known to be irritant; it is a mitigation.
The Mistakes That Make a Correct Dose Miss the Patient
The flush volume is rarely the error. The errors around it are, and they cluster into a short list that simulation instructors see repeatedly. The most common is flushing at a port on the far side of a stopcock that is turned toward the fluid bag, which sends the saline into the bag and leaves the drug in the line. The second is disconnecting the drug syringe, then attaching a flush syringe, which introduces a pause and an air bubble at the hub.
A third error is using the flush to "speed up" a drug that should be given slowly. Amiodarone in a perfusing patient has a rate limit; in cardiac arrest the push is rapid, so this particular error is more common in post-arrest care than during the code itself. The flush follows the drug at whatever rate the drug was given, and the two are documented as one administration event.
A fourth error is forgetting the flush entirely when the next rhythm check arrives. The team's attention shifts to the monitor, the drug sits in the line, and the dose is effectively given late. The AHA's 3-to-5-minute epinephrine interval is measured from the previous dose, and a dose that never left the tubing doesn't count. The fix is verbal: the person pushing the drug says "pushing epinephrine, flushing 20," and the recorder notes both.
The fifth error is volume overload in a patient who cannot tolerate it. Twenty milliliters four times over a ten-minute code is 80 mL, which is trivial; a team using a 100 mL bag as a flush source for every drug can push several hundred milliliters into a patient with known heart failure or renal disease. That is a real consideration in the post-arrest phase, not during the code. The guideline volume is small by design; the bag-as-flush habit is what adds volume.
How Teams Document and Audit the Flush
Documentation is where the flush volume becomes visible to anyone outside the room. Most code records capture the drug, the dose, the route, and the time; the flush is often folded into the administration note or omitted entirely. Accreditation surveys and internal audits that look at code documentation will sometimes ask whether the flush was given, and a record that doesn't show it reads as a gap even when the flush happened.
The practical documentation line is "Epi 1 mg IV push, followed by 20 mL NS flush," time-stamped. That single sentence captures the volume, the route, and the sequence. Teams that use a bag-as-flush source sometimes document "flushed with NS from 100 mL bag," which is less precise but honest about the volume range. Neither version is wrong; the imprecise one is harder to audit.
Institutional policy is the controlling document for most bedside decisions. If the policy says 10 mL and the guideline says 20 mL, the policy is the one the audit measures against until it is revised. That is not a reason to give less than the guideline during a code; it is a reason to route the discrepancy to the committee that owns the policy. The revision, once made, propagates to the code carts and the training materials.
The audit trail also matters for training. A code review that finds the flush was given after the rhythm check rather than at the time of the drug identifies a timing problem, not a volume problem, and the fix is a verbal habit rather than a new protocol. Volume audits and timing audits ask different questions and should be run separately.
Frequently Asked Questions
Is 20 mL the answer for every drug given in cardiac arrest?
No. Twenty milliliters is the AHA figure attached to epinephrine in the 2015 ACLS update and carried forward in the 2020 focused update. Amiodarone, lidocaine, and magnesium sulfate are each followed by a normal saline flush, but the specific volume lives in the product label and the institutional protocol. Check the label on your cart for the drug in hand rather than assuming the epinephrine figure transfers.
Why did the recommended flush change from 10 mL to 20 mL?
The 2010 AHA guidelines used 10 mL for the epinephrine flush; the 2015 update raised it to 20 mL. The change tracked the wider availability of larger pre-filled saline syringes and 100 mL bags used as flush sources on code carts, not a new pharmacokinetic finding. Both volumes clear a short peripheral line, so the practical difference at the bedside is small and the documentation difference in an audit is not.
What if the patient has no IV and the drug goes in intraosseously?
The intraosseous route uses a different flush pattern: 10 mL of normal saline before the drug to confirm the marrow cavity is patent, then the drug, then another 10 mL to move it out of the marrow. The pre-dose flush is the step most often skipped in simulation, and skipping it means you don't know the IO is working until the drug fails to act. Confirm your IO protocol's volumes against the AHA guidance for IO administration.
Does the flush volume change for a central line?
The volume stays at 20 mL for a typical triple-lumen central catheter, but the job is easier because the drug enters a large vessel almost directly. Central lines have their own dead space, often more than 5 mL, which the flush must clear before any drug reaches the circulation. The volume question gets simpler on a central line; the access question gets harder because insertion takes time the code may not have.
Can the flush cause fluid overload during a code?
A single 20 mL flush four times over ten minutes is 80 mL, which is negligible. The risk comes from teams that use a 100 mL bag as the flush source for every drug, which can add several hundred milliliters across a long code. That volume matters in the post-arrest phase for patients with heart failure or renal disease, and it is a reason to track cumulative flush volume in the code record rather than counting syringes.
What if the flush won't go in?
A flush that meets resistance suggests infiltration, a positional catheter, or a closed stopcock. During a code, don't troubleshoot a peripheral line for more than a few seconds; move to a second peripheral site or an intraosseous route. A flush that goes in but produces swelling at the site means the dose went into tissue, and the drug should be re-dosed through working access per your protocol.
Is the flush volume different for pediatric cardiac arrest?
Pediatric advanced life support guidance follows the same principle — push the drug, then flush — but the volumes scale with the patient and the line. A 20 mL flush in a 10 kg child is a meaningful fluid bolus, and pediatric protocols typically specify smaller flush volumes tied to the catheter size. Use the PALS reference for the weight-based figure rather than the adult 20 mL.
How much time does the flush add to a code?
A 20 mL push from a pre-filled syringe takes about two seconds; from a 100 mL bag through a stopcock, about the same. The flush does not meaningfully extend the drug administration interval, and it should not pause compressions. The time cost is in the verbal confirmation and the documentation, not the push itself, which is why teams build the flush into the drug call-out rather than treating it as a separate step.
This article is general educational information about resuscitation practice, not a diagnosis, treatment plan, or substitute for clinical training. Flush volumes, drug doses, and code protocols vary by certifying body, institution, and patient, so confirm the current guidance from the American Heart Association and your local protocol before applying any figure here. For an actual cardiac arrest or any immediate danger, call your local emergency number and follow the direction of the responding clinical team.