RECOVER CPR Advanced life support Flashcards

Question

What two factors determine the end tidal CO2 factors?

Answer 1

The EtCO2 value will be determined by two main factors: (1) minute ventilation (the product of respiratory rate and tidal volume), and (2) the amount of blood returning from the tissues to the lungs.

Answer 2

Because it is directly related to cardiac output, the EtCO2 can be used to monitor the quality of chest compressions during CPR. During CPR, the EtCO2 reflects the amount of blood returning from the body to the lungs. EtCO2 will be directly related to the cardiac output. With higher cardiac output, the EtCO2 will be higher, while with lower cardiac output, the EtCO2 will be lower.

Answer 3

Cardiac output increases dramatically upon return of spontaneous circulation ROSC; therefore, a sudden increase in EtCO2 to > 30 mmHg provides a vital clue that ROSC has occurred

Answer 4

Unlike the ECG, auscultation, direct pulse palpation or echocardiography, the end tidal CO2 can be evaluated while chest compressions are occurring

Answer 5

In any patient with a sudden increase in EtCO2 during chest compressions, it is important to assess the presence of a pulse before stopping chest compressions. In addition, you can assess for other signs of ROSC, such as voluntary motor movements, chewing on the endotracheal tube, return of the corneal or palpebral reflex, or signs of consciousness. However, until a spontaneous pulse has been definitively identified, chest compressions should be continued.

Answer 6

Verify accurate ETT placement during CPA using one of the following approaches: Direct visualization of chest movements during a positive pressure breath Direct visualization of placement through the arytenoid cartilages during intubation

Answer 7

There are 2 main reasons the EtCO2 may read zero during CPR: The ETT is in the esophagus The cuff on the ETT is not sufficiently inflated

Answer 8

If ventilation is provided at a rate faster than 10 bpm, or tidal volumes larger than 10 ml/kg are delivered, the EtCO2 will drop. In this case, the decreased end tidal CO2 is due to increased minute ventilation, not lower cardiac output. In order for EtCO2 to be a useful indicator of cardiac output during CPR, breaths must be delivered consistently at a rate of approximately 10 per minute, as described in the basic life support algorithm.

Answer 9

peripheral venous CO2 partial pressure

Answer 10

PvCO2 (peripheral venous CO2 partial pressure) should not be used as a substitute for EtCO2, as there is often very little association between PvCO2 and EtCO2 during CPA. During CPR, the PvCO2 may be much higher than the EtCO2 because of poor blood flow in the periphery and buildup of CO2 in these peripheral tissues. Using PvCO2 rather than the EtCO2 may lead the rescuer to believe that compression quality is good when, in fact, the EtCO2 may actually be low due to poor blood flow to the lungs

Answer 11

Changes in EtCO2 will reflect changes in blood flow, and are therefore useful for two main purposes during CPR: (1) evaluating the efficacy of chest compressions, and (2) identifying ROSC.

Answer 12

Compression quality (rate, depth, chest recoil) should be improved during CPR in any patient with EtCO2 values less than 15 mmHg.

Answer 13

Increasing compression depth up to one-half the width of the chest Verifying that the compression rate is between 100 and 120 compressions per minute Ensuring that compressions are being performed at the correct location on the chest based on the patient's conformation and size Taking care not to lean on the chest between compressions to allow for full elastic recoil and filling of the heart

Answer 14

Remember that increased minute ventilation (respiratory rate greater than 10 per minute and/or large tidal volumes) will decrease EtCO2, even if chest compressions are being done correctly. Therefore, in order to use EtCO2 as a measure of chest compression efficacy, ventilation must be delivered consistently at a rate of 10 breaths per minute, as described in the BLS algorithm.

Answer 15

During CPA, indirect blood pressure monitors and pulse oximeters are not useful due to the lack of adequate pulse pressure. These devices rely upon pulsatile arterial blood flow that is detectable by the machine, and during CPR, there is typically inadequate pulsatile flow for accurate readings. Attempts to determine either indirect blood pressure or oxygen saturation will result in inaccurate or undetectable results. In addition, like the ECG monitor, both indirect blood pressure monitors and pulse oximeters are highly susceptible to the motion artifact present during chest compressions. Finally, these monitors may distract resuscitative efforts by providing extraneous or inaccurate information to the team leader.

Answer 16

Because of motion artifact and lack of a consistent peripheral pulse, the pulse oximeter is unlikely to be of value during CPR. In addition, attempts to get a good signal from a pulse oximeter during CPR can distract team members from more important tasks. On the following screen, watch the video for an example of how focusing on the pulse oximeter can distract the team from doing effective CPR.

Answer 17

If a patent catheter is available, it should be used. If more than one catheter is present, the catheter closest to the heart should be used in order to improve drug delivery time. A central line will deliver drugs into the venous system closest to the heart and should be used to administer CPR drugs, if available. If only peripheral catheters are available, they should be prioritized in the following order: Jugular Cephalic Saphenous

Answer 18

The catheter closest to the heart should be used in order to improve drug delivery. dog with veins outlined In animals without a pre-existing catheter, BLS should begin promptly, and the team leader should provide direction as to the type of vascular access to be obtained. In cases with adequate team members, more than one individual may work on IV catheter placement at separate sites.

Answer 19

Regardless of the location of the catheter, following drug administration the catheter should be flushed with an isotonic crystalloid solution to facilitate flow to the heart and ultimately to the tissues. While there is no specific evidence regarding the volume of flush, in general 3-5 cc in cats, 5-10 cc in small to medium sized dogs, and 10-15 cc in large and giant breed dogs is reasonable.

Answer 20

Options for vascular access include: Percutaneous peripheral venous Venous cutdown Intraosseous (IO)

Answer 21

A smaller than average catheter (e.g., 20-22 G) may be placed more easily than a larger catheter. The initial small-bore catheter can be used during CPR for drug administration. Following ROSC, a larger bore catheter may be placed if needed.

Answer 22

The catheter is then secured with sutures to avoid dislodgment.

Answer 23

Placement of an intraosseous catheter may be considered when prompt IV access is not practical or possible, or when venous catheterization has been unsuccessful. IO catheters facilitate rapid drug delivery into the central circulation.

Answer 24

Many sites are possible for placement of IO catheters. Common sites include the humerus, the femur, and the tibia. Because the humerus is close to the heart, IO catheters in this bone will provide the fastest CPR drug delivery to the sites of action. Due to the proximity of the humerus to the thorax, where chest compressions are occurring, it is often easier to use the hindlimb during CPR. However, recall that the humerus is closest to the heart, so if it is accessible, it is the preferred site of IO catheter placement.

Answer 25

For kittens and puppies, an 18 or 20 gauge standard needle without a stylet may be used. Alternatively, the use of a spinal needle with stylet will reduce the risk of plugging the needle with bone during placement.

Answer 26

In general, IV or IO administration is preferred due to the variable absorption of drugs administered into the trachea. However, intratracheal drug administration may be considered when there is no IV or IO access readily available.

Answer 27

Drugs that may be given IT include epinephrine, atropine, and vasopressin.

Answer 28

However, sodium bicarbonate should never be administered IT.

Answer 29

Recall that IT administration of drugs is a stopgap measure as you continue to attempt to obtain direct vascular access via IV or IO catheterization. As soon as IV or IO access is obtained, drugs should be re-dosed via the IV or IO route.

Answer 30

There is limited experimental evidence to guide IT dosing, but in general, doses of two to ten times IV/IO doses are recommended

Answer 31

IT drugs should be diluted in 5 to 10 ml of either sterile water or saline.

Answer 32

In order for IT drugs to be effective, they must be absorbed across the tracheal/bronchial epithelium and reach the bronchial circulation.

Answer 33

A long catheter, such as a 5 French red rubber catheter, is fed through the endotracheal tube. The diluted drug is administrated through the red rubber catheter. The syringe delivers a pulse of 5 to 10 ml of air into the red rubber catheter to blow as much of the fluid out of the tube as possible. The catheter should then be withdrawn from the endotracheal tube and the ventilation bag re-connected. Two breaths should be administered rapidly to help disperse the medication throughout the pulmonary tree.

Answer 34

Drugs that may be given IT include epinephrine, atropine, and vasopressin. However, sodium bicarbonate should never be administered IT. Recall that IT administration of drugs is a stopgap measure as you continue to attempt to obtain direct vascular access via IV or IO catheterization. As soon as IV or IO access is obtained, drugs should be re-dosed via the IV or IO route.

Answer 35

Given the evidence that intratracheal (IT) drug administration leads to therapeutic plasma concentrations of most emergency drugs and the risks associated with blind intracardiac (IC) injections (such as laceration of coronary vessels), the IT route is preferred over the IC route during CPR.

Answer 36

Prompt vascular access is essential to successful outcomes in CPR. Multiple options are available, including percutaneous peripheral catheterization, venous cutdown, and intraosseous catheterization. If multiple catheters are available, the catheter that is closest to the heart and therefore provides the most rapid delivery of drugs to the central circulation should be used. If percutaneous catheterization is not immediately successful, a cutdown procedure may be performed to achieve venous access. Rapid vascular access may be obtained using intraosseous (IO) catheters as well. If venous or IO catheterization is not possible, certain drugs may be administered intratracheally. In this scenario, attempts at IV or IO catheterization should continue and drugs re-dosed as soon as vascular access is achieved.

Answer 37

Reversal Agents for Sedatives: Intravenous Drug Delivery Intramuscular or subcutaneous administration of reversal agents is not recommended in patients with CPA due to slow, unpredictable uptake. Therefore, intravenous or intraosseous administration of reversal agents is recommended in patients with CPA.

Answer 38

In general, if a reversible sedative or anesthetic agent has been administered to an animal with CPA, early intravenous treatment with a reversal agent is indicated. Even if the drug was administered several hours before the CPA occurred, reversal is generally safe and may still have some positive effects.

Answer 39

Remember from the RECOVER CPR algorithm that the first step in initiating Advanced Life Support is to connect the ECG and EtCO2 monitors. Next we should verify that our vascular access is present and patent. Only after those 2 steps are completed should reversal agents be administered. Reversal agents do not directly treat CPA, but are adjunctive therapies that may improve the chances of achieving ROSC. Always remember to follow the steps of the algorithm in order.

Answer 40

IV fluid therapy is helpful for improving cardiac output in patients with documented or suspected hypovolemia, but may be detrimental in euvolemic patients with CPA due to reduced blood flow and oxygen delivery to core organs.

Answer 41

The amount of blood flow, and hence oxygen delivered, to a tissue bed is determined by the force driving blood into the tissue bed, the resistance to flow offered by the vasculature in the tissue bed, and the force pushing back at the outflow of the tissue bed

Answer 42

The driving force for blood flow to most tissues is the mean arterial blood pressure (MAP), and the outflow force pushing back is the central venous blood pressure (CVP)

Answer 43

In hypovolemic patients with spontaneous circulation, IV fluid therapy can improve cardiac output and increase MAP because of the relationship between stretch of the ventricles and the subsequent ability of the ventricle to contract more fully due to that stretch. With increased intravascular volume provided by IV fluid therapy, the ventricles experience greater stretch and hence can contract more and increase cardiac output.

Answer 44

If a patient in CPA is euvolemic and fluids are administered intravenously, it is unlikely that cardiac output will increase significantly because the ventricles are not spontaneously contracting. Therefore, fluids administered IV will accumulate in the venous circuit, which is more distensible than the arterial circuit, resulting in increased central venous pressure (CVP) rather than increased MAP. This increase in CVP leads to higher pressure on the outflow side of the tissue bed, resulting in decreased blood flow and oxygen delivery to the tissues. Therefore, in patients in CPA that are euvolemic, fluids should be administered conservatively if at all, until ROSC is achieved and the heart is again contracting spontaneously.

Answer 45

For patients in CPA with known or suspected hypovolemia, boluses of IV fluids may be beneficial to provide additional circulating volume. Although CVP will increase, the increased stretch of the ventricles will lead to improved cardiac output, increasing MAP and improving blood flow to the tissues. Patients with trauma, severe vomiting and/or diarrhea, or hemorrhage are likely to benefit from fluids.

Answer 46

Potentially Detrimental Side Effects of Glucocorticoids There is a growing body of evidence that corticosteroids may have detrimental effects in many cases, and given the weak evidence supporting their use, glucocorticoids should be avoided unless there is a clear indication. Glucocorticoids have many potentially detrimental side effects that may be particularly dangerous in patients with CPA. Because they are counter-regulatory hormones in glucose metabolism, glucocorticoids commonly cause hyperglycemia, which can perpetuate brain injury in patients with brain ischemia, common in CPA. Glucocorticoids also very commonly lead to gastrointestinal ulceration in dogs, causing significant blood loss and/or bacterial translocation leading to septicemia. In both dogs and cats, they decrease prostaglandin production in the kidney, compromising renal perfusion and potentially leading to ischemic acute kidney injury.

Answer 47

Patients That May Benefit from Glucocorticoids However, glucocorticoids may be warranted in certain patient populations. For instance, animals that arrest in association with anaphylactic shock may benefit from anti-inflammatory doses of glucocorticoids (0.1 mg/kg dexamethasone SP IV). Patients with concurrent hypoadrenocorticism (i.e., Addison's disease) will also benefit from glucocorticoids. Finally, animals that develop critical illness-related corticosteroid insufficiency (CIRCI) after ROSC may also benefit from physiologic steroid therapy. Corticosteroids should only be used during CPR if the patient is known to have or is highly suspected of having one of these disorders. For the vast majority of patients, corticosteroids should not be administered during CPR.

Answer 48

Potential benefits of open-chest CPR (OCCPR): Better cardiac output Higher rates of ROSC Direct assessment of the heart

Answer 49

Specific indications for OCCPR include: Pleural space disease such as large volume pleural effusion or pneumothorax Pericardial effusion Patients already under anesthesia for thoracic or abdominal surgery Giant breed dogs with round chest conformations, such as Mastiffs, Saint Bernards, and some Great Danes

Answer 50

OCCPR requires: A rapid emergency thoracotomy for direct cardiac massage Closure of the thorax Post-cardiac arrest care

Answer 51

Pleural space disease, such as large volume pleural effusion or pneumothorax, is an indication for OCCPR. Because of the markedly increased intrathoracic pressure in patients with severe pleural space disease, venous return to the heart is compromised and external chest compressions are unlikely to result in forward flow out of the heart. Opening the chest relieves the pressure exerted by the pleural space disease and allows the heart to fill so that chest compressions are effective.

Answer 52

Pericardial effusion is an indication for OCCPR because cardiac tamponade impedes return of blood to the atria, resulting in minimal cardiac output during external chest compressions. OCCPR allows the rescuer to open the pericardium and remove the pericardial effusion.

Answer 53

OCCPR should be initiated in patients under anesthesia for thoracic or abdominal surgery. For patients undergoing thoracotomy, easy access to the heart for direct cardiac compressions is already available. For patients having abdominal surgery, rolling them into lateral recumbency for chest compressions is not feasible, and direct cardiac compressions can easily be achieved by incising through the diaphragm and compressing the heart through the diaphragmatic incision.

Answer 54

Giant breed dogs with round chest conformations In giant breed dogs with round chest conformations, OCCPR is more likely to be of benefit than closed-chest CPR. This is because they have poorly compliant chests that are difficult to compress adequately to generate enough intrathoracic pressure to provide substantial blood flow using the thoracic pump approach. On the other hand, in cats or in small dogs (<10 kg), in which external chest compressions are more effective due to higher chest compliance, OCCPR is not indicated; in these animals, internal cardiac massage is more challenging due to the small size of their thoracic cavities.

Answer 55

If OCCPR is to be pursued, it is best to begin the procedure as early in the course of a resuscitative effort as possible. This is why it is important to obtain a CPR code (red, yellow, or green) in any patient admitted to the hospital as discussed in the BLS course. In this case, because the dog has pleural space disease, OCCPR should be pursued.

Answer 56

ECG ECG monitoring is an essential part of ALS. The ECG rhythm diagnosis is the primary decision point in the ALS portion of the CPR algorithm. It is therefore important that attachment of ECG leads be a priority after BLS has been started.

Answer 57

start one-handed compressions, intubate and ventilate While Tom is likely suffering from a urethral obstruction, CPA requires immediate support of the cardiovascular system. Additionally, while intravenous fluids will likely be useful in this case, the first priority must be restoration of circulation via chest compressions in the patient with CPA. Finally, while determining the arrest rhythm will help guide ALS therapy, the first priority in any patient in CPA is initiation of BLS.

Answer 58

ECG While indirect blood pressure monitors and pulse oximeters are often desirable in emergency and critical care medicine, during CPR, these devices become less useful due to the lack of adequate pulse pressure. These devices rely upon pulsatile arterial blood flow, and during CPR, adequate pulsatile flow for device function is typically absent. Attempts to determine either indirect blood pressure or oxygen saturation will result in inaccurate or undetectable results. Equally importantly, attempts to use these monitors may distract the people available for assisting in resuscitative efforts, and provide extraneous and inaccurate recommendations for the team leader.

Answer 59

Prompt vascular access is essential for increasing the likelihood of a successful outcome of CPR. Immediate venous cutdown or placement of an IO catheter should be considered when prompt percutaneous access is not practical or possible, or when venous catheterization has been unsuccessful.

Answer 60

Explain that open chest CPR is not warranted in cats Open-chest CPR (OCCPR) has only been associated with a higher rate of ROSC than closed-chest CPR in experimental studies in dogs with VF. It is unlikely to be of benefit over closed-chest CPR in cats or in small dogs (<20 kg) because these smaller animals have greater chest compliance and the thoracic cavity is very small, making internal chest compressions very difficult.

Answer 61

Tom's initial physical exam was consistent with hypovolemic shock (pale mucous membranes, prolonged CRT, poor pulse quality) and he would likely benefit from an initial fluid bolus. 20-30 ml/kg represents 1/3-1/2 of his total blood volume (60 ml/kg in a cat) and would be a reasonable fluid bolus in this case. 90 ml/kg is an excessive amount for an initial bolus, and a fluid rate of 2 ml/kg is unlikely to address his hypovolemia rapidly enough. If Tom had been euvolemic, withholding fluids during CPR would have been most appropriate, but given the evidence of hypovolemia, a 20-30 ml/kg bolus over 15 minutes is the best choice.

Answer 62

Start chest compressions, intubate and ventilate While Ruby is likely suffering from an immune-mediated hemolytic anemia, CPA requires immediate support of the cardiovascular system. While steroids, blood products, and a fluid bolus may all be part of her initial therapy, the first priority in any patient in CPA is initiation of BLS.

Answer 63

There are consistent, repeated QRS complexes that are narrow at a rate of less than 200 per minute with no associated pulses, so this is most likely pulseless electrical activity. Had the rate been greater than 200 per minute with wide complexes, pulseless VT would have been more likely.

Answer 64

attach ecg leads

Answer 65

Electrode gel

Answer 66

Cephalic intravenous catheter

Answer 67

Atipamezole and naloxone are indicated

Answer 68

Right lateral thoracotomy (left lateral recumbency)

Answer 69

Her dog is more likely to have a good outcome with immediate open-chest CPR than with closed-chest CPR

Answer 70

Remember that non-shockable rhythms are the most common arrest rhythms in dogs and cats.

Answer 71

ECG analysis during CPR is focused on differentiating three major types of arrest rhythms: Perfusing rhythms associated with pulses Non-shockable arrest rhythms that do not require electrical defibrillation Shockable arrest rhythms that require electrical defibrillation

Answer 72

During the brief pause in compressions between cycles of BLS, the team leader should interpret the ECG and announce the rhythm diagnosis. Agreement should be reached among all team members as to the ECG rhythm diagnosis; if consensus is not reached immediately, chest compressions should be re-started and the discussion about rhythm diagnosis can continue during the next cycle of compressions. Ultimately, if consensus cannot be reached, the team leader should make the diagnosis after considering input from all team members. Chest compressions should never be stopped during a cycle of BLS strictly to evaluate the ECG. However, if there is a sudden rise in EtCO2, and a strong, palpable pulse is noted during a cycle of BLS, it is reasonable to briefly pause chest compressions to review the ECG and palpate the pulse to determine if ROSC has truly been achieved.

Answer 73

If repeated complexes are present, quickly palpate the pulse or apex beat to determine if there is blood flow associated with the complexes. If there are pulses, this is a perfusing rhythm and the patient has achieved a return of spontaneous circulation, so chest compressions can be discontinued.

Answer 74

Pulse assessment should take no more than five seconds. If there is any doubt as to whether a pulse is present, assume that one is not present and continue BLS.

Answer 75

A rate of less than 200 per minute is most consistent with pulseless electrical activity (PEA), a non-shockable rhythm. In this case, the PEA/Asystole ALS algorithm should be followed. We will discuss treatment of PEA/Asystole in detail later in the module.

Answer 76

not shockable

Answer 77

pulseless ventricular tachycardia

Answer 78

a perfusing rhythm

Answer 79

not shockable

Answer 80

ventricular fibrillation

Answer 81

Typically, the rate for PEA is much lower (less than 50 per minute)

Answer 82

Recall that with PEA, the electrical conduction system of the heart is active and generates a measureable ECG waveform, but there is no mechanical activity in the heart and no blood flow out of the heart.

Answer 83

Recall that with pulseless VT, the ventricles are contracting, but the heart rate is so fast that there is no time for the ventricles to fill and thus no significant flow of blood out of the heart

Answer 84

The following is an example of pulseless VT. Note that in this example, the rate is 236 per minute. Also note that the QRS complexes are wider than the PEA example. Although the rate is the most reliable feature differentiating PEA from pulseless VT, the QRS complexes are also usually relatively wider in pulseless VT than in PEA

Answer 85

Recall that animals with ventricular fibrillation have random electrical and mechanical activity within the ventricles, causing them to quiver, but not to generate blood flow out of the heart.

Answer 86

pulseless electrical activity

Answer 87

Pulseless ventricular tachycardia

Answer 88

Diagnosis = Perfusing Rhythm/ROSC

Answer 89

Ventricular fibrillation

Answer 90

ALS therapy also targets the shockable rhythms (VF and pulseless VT) by stopping the uncoordinated or excessively rapid ventricular activity using electrical or mechanical defibrillation

Answer 91

These rhythms can only be differentiated by palpating a pulse. Although there may be some pulse deficits, perfusing VT will be associated with a pulse or apex beat for most ECG complexes, while patients in pulseless VT will not have pulses associated with any complexes. Additionally, animals with pulseless VT will be collapsed and unresponsive, while animals with perfusing VT will be conscious, although they may appear weak or pale.

Answer 92

Two Categories of Perfusing VT There are two categories of perfusing VT: stable VT (also called an accelerated idioventricular rhythm, or AIVR) and unstable VT

Answer 93

Both indicate underlying ventricular myocardial ischemia or disease, causing groups of myocardial cells to drive the heart rhythm rather than the SA node, as the myocardial cells are depolarizing at a rate faster than the SA node. Most commonly, these rhythms occur in dogs due to systemic diseases that affect myocardial perfusion, but occasionally they may occur because of intrinsic cardiac disease.

Answer 94

Stable VT is also called an accelerated idioventricular rhythm (AIVR)

Answer 95

It is a ventricular arrhythmia that generates blood flow sufficient for oxygen delivery to the tissues of the body, and hence the patient has a normal blood pressure. It generally results in a heart rate of less than 180 beats per minute and often alternates with a sinus rhythm.

Answer 96

In many patients, this rhythm will require no direct therapy, but if the complexes are of varying shapes and sizes (multiform ventricular premature contractions), there may be widespread myocardial ischemia or injury, and therapy may be warranted, as the patient may be at increased risk of degenerating into unstable VT or ventricular fibrillation.

Answer 97

Unstable VT is a ventricular tachyarrhythmia that generates insufficient blood flow and results in arterial hypotension (mean arterial blood pressure <80 mmHg). It may occur at any rate, but typically in dogs it results in a heart rate greater than 180 beats per minute.

Answer 98

Unstable VT may also include runs of the R on T phenomenon, where the flat baseline of the ECG disappears and the ECG takes on a “sine wave” appearance

Answer 99

Unstable VT may occur due to systemic disease resulting in myocardial ischemia, and may also reflect underlying cardiac disease.

Answer 100

In most cases, it should be treated with antiarrhythmic drugs.

Answer 101

Options for treating unstable VT or very rapid (>180 bpm) stable VT include lidocaine (2 mg/kg slow IV over 1–2 minutes; may be repeated up to three times), amiodarone (0.5 mg/kg diluted 1:10 with D5W slow IV over 1–2 minutes), or procainamide (2–6 mg/kg slow IV over 1–2 minutes). Amiodarone can cause allergic reactions in dogs, so when using it to treat VT, it is important to monitor closely for signs. All three drugs can slow the rate of ventricular myocardial cells.

Answer 102

lidocaine (2 mg/kg slow IV over 1–2 minutes; may be repeated up to three times)

Answer 103

This is a vasopressor - The catecholamine used most commonly during CPR is epinephrine, although other catecholamines such as norepinephrine, methoxamine, and phenylephrine have also been used.

Answer 104

Catecholamines cause peripheral vasoconstriction via peripheral α-1 adrenergic receptors. Epinephrine also stimulates other adrenergic receptors, such as β-1 and β-2 receptors, but these effects are unlikely to be beneficial during CPR and may, in fact, be harmful.

Answer 105

AVP (or simply vasopressin) acts independently of the adrenergic receptors via peripheral V1 receptors. Therefore, it does not have any of the negative effects caused by stimulation of the other adrenergic receptors. Epinephrine also stimulates other adrenergic receptors, such as β-1 and β-2 receptors, but these effects are unlikely to be beneficial during CPR and may, in fact, be harmful.

Answer 106

There are three options for vasopressor therapy use during CPR: low-dose epinephrine, high-dose epinephrine, and vasopressin.

Answer 107

Low-dose epinephrine (0.01 mg/kg)

Answer 108

vasopressin (0.8 units/kg)

Answer 109

High-dose epinephrine (0.1 mg/kg)

Answer 110

High-dose epinephrine (0.1 mg/kg) has been associated with substantial negative side effects and should only be considered if CPR is prolonged (>10 minutes) and as a last attempt, when CPR is becoming futile

Answer 111

In patients with acute, reversible disease in which good blood flow is being achieved (EtCO2 > 15 mmHg), continuing low-dose epinephrine even after 10 minutes of CPR is the best option. High-dose epinephrine should only be used as a last attempt in a patient in whom you feel CPR is likely becoming futile. This is why the high-dose epinephrine line is printed in light grey on the RECOVER drug and dosing chart shown below.

Answer 112

Vasopressors may be administered IV, IO or IT. Recall that the catheter closest to the heart should be used for intravascular drug therapy to expedite distribution to the sites of action.

Answer 113

Outside of the U.S., epinephrine is referred to as adrenaline.

Answer 114

It is naturally produced in the adrenal medulla

Answer 115

Epinephrine stimulates α-1, β-1 and β-2 adrenergic receptors

Answer 116

its physiologic roles are associated with the “fight or flight” response, including peripheral vasoconstriction, increased heart rate, increased cardiac contractility, and bronchodilation.

Answer 117

While it is associated with a higher rate of ROSC, it is also associated with worse neurological function in survivors and reduced hospital discharge rates.

Answer 118

Epinephrine is supplied at 1 mg/ml,

Answer 119

Low-dose epinephrine should be used initially for treatment of all non-shockable arrest rhythms

Answer 120

It may be repeated every 3-5 minutes during CPR (or every other cycle of BLS).

Answer 121

In patients with acute, reversible disease, it is recommended that low-dose epinephrine be administered even after 10 minutes of CPR to maximize the chance of survival to discharge.

Answer 122

it is also associated with worse neurological function in survivors and reduced hospital discharge rates. It is believed that this negative impact is due to extreme vasoconstriction leading to more severe peripheral acidosis from poor perfusion and from increased myocardial oxygen demand during the post-cardiac arrest period. The β-1 effects of increased cardiac contractility and increased heart rate are likely to blame

Answer 123

The Effect of Acidemia – Epinephrine is most effective at physiological pH values and is progressively less effective as acidemia develops. Patients with CPA commonly develop metabolic acidosis from accumulation of lactate and uremic toxins from poor perfusion, as well as respiratory acidosis from hypoventilation and poor peripheral perfusion. Therefore, the vasoconstrictive effects of epinephrine may be blunted during CPR, and the use of an alternate vasopressor such as vasopressin may be warranted, especially in patients with prolonged CPA.

Answer 124

Patients with CPA commonly develop metabolic acidosis from accumulation of lactate and uremic toxins from poor perfusion, as well as respiratory acidosis from hypoventilation and poor peripheral perfusion

Answer 125

Via β-1 stimulation, epinephrine is also a positive inotrope and chronotrope, although this is not its primary indication in CPR. Following ROSC, this positive inotropy and chronotropy may increase myocardial oxygen demand, potentially worsening myocardial ischemia, and may lead to tachyarrhythmias. The use of high-dose epinephrine may worsen these undesirable effects.

Answer 126

epinephrine is also a positive inotrope and chronotrope, although this is not its primary indication in CPR. Following ROSC, this positive inotropy and chronotropy may increase myocardial oxygen demand, potentially worsening myocardial ischemia, and may lead to tachyarrhythmias.

Answer 127

Vasopressin is an alternative vasopressor that can be used to treat non-shockable arrest rhythms.

Answer 128

Vasopressin (also referred to as arginine vasopressin) is a hormone primarily involved in total body water balance via stimulation of V2 receptors in the renal collecting ducts. In addition to its effects on water balance via V2 receptor stimulation, vasopressin also stimulates V1 receptors on the peripheral vasculature and is a potent vasopressor when given at supraphysiological doses. This is the drug’s primary use during CPR.

Answer 129

Vasopressin is supplied as a 20 U/ml solution

Answer 130

it may be repeated every 3-5 minutes during CPR (or every other cycle of BLS).

Answer 131

dosed at 0.8 U/kg IV/IO or 4–8 U/kg IT during CP

Answer 132

Vasopressin may potentially be preferable to epinephrine in some patients because V1 receptor responsiveness is not affected by pH. Therefore, the drug is more likely to be efficacious in patients with respiratory and metabolic acidoses, which commonly occur with prolonged CPA.

Answer 133

Vasopressor therapy, either low-dose epinephrine, vasopressin, or both, should be administered once every two cycles of BLS, or every 3–5 minutes during CPR, to treat asystole or PEA. High-dose epinephrine is recommended only with prolonged CPR (>10 minutes), and should be considered a “last ditch attempt” to obtain ROSC with the understanding that it may have a negative impact on overall outcome. Administering a vasopressor every cycle of CPR leads to excessive vasoconstriction.

Answer 134

High vagal tone may occur with: Severe gastrointestinal disturbances (vomiting, diarrhea) Diseases of the respiratory tract (coughing) Ophthalmologic surgery Laryngeal manipulation, such as intubation Opioid analgesic administration

Answer 135

High parasympathetic tone to the heart via stimulation of the vagus nerve may lead to severe bradycardia and cardiac arrest. It can be caused by a number of disease processes and therapies.

Answer 136

Effects of High Vagal Tone High vagal tone causes bradycardia, and may be appreciated on an ECG as sinus bradycardia, AV block, or a pronounced sinus arrhythmia

Answer 137

This decrease in heart rate can lead to low blood pressure, decreased perfusion to the heart, and, ultimately, cardiac arrest.

Answer 138

The Use of Parasympatholytics In critically ill patients where CPA is considered imminent, parasympatholytics may prevent or treat vagally-mediated bradycardia. Prevention or treatment of bradycardia may be adequate to prevent CPA

Answer 139

For animals in CPA, parasympatholytics are often used to eliminate vagal tone, which may remove the inhibitory stimulation of the vagus nerve on the heart during CPR and increase heart rate following ROSC.

Answer 140

Atropine is the most commonly used parasympatholytic during CPR. Glycopyrrolate may also be used, but is less commonly chosen because it is less potent and longer acting, making it more difficult to titrate the dose in acute cases.

Answer 141

Atropine is a parasympatholytic drug that is widely used in veterinary medicine. IV atropine will have a brief paradoxical effect of slowing the heart rate by acting on central muscarinic receptors and causing a transient increase in vagal tone. This effect is rapidly overcome by elimination of vagal tone peripherally, leading to increased heart rate.

Answer 142

Atropine is most commonly given during CPR at a dose of 0.04 mg/kg in order to increase the heart rate

Answer 143

However, due to its longer half life, this drug should only be repeated once during a CPR attempt. It may be given either at the same time as vasopressors or on alternate cycles.

Answer 144

Atropine may be administered IV, IO, or IT, and as with all arrest drugs, should be administered through the catheter located closest to the heart.

Answer 145

If administered IT, the dose should be doubled and the drug diluted with sterile saline or water. A red rubber catheter should be passed through the ET tube and Atropine administered through the red rubber catheter, followed by an air flush.

Answer 146

Atropine causes the pupils to dilate and may block the pupillary light reflex, so evaluation of the pupil size and responsiveness may not be useful for assessing neurologic status in patients that have been treated with atropine during CPR. Additionally, ROSC will generally precede the return of the corneal reflex.

Answer 147

In cases of bradycardic arrests mediated by high vagal tone, atropine is likely to be of benefit and should be administered as soon as possible during CPR. However, the first step once CPA has been diagnosed is to begin basic life support. In addition, even in a vagally mediated bradycardic arrest, initial drug therapy should prioritize a vasopressor, as there is more evidence supporting a beneficial effect for vasopressors than for parasympatholytic drugs during CPR.

Answer 148

Acidosis limits the efficacy of catecholamines, which have the greatest effect at a normal pH of 7.4.

Answer 149

Acidosis resulting from lactate and CO2 accumulation may become severe during CPA, and pH of <7.0 is commondosis resulting from lactate and CO2 accumulation may become severe during CPA, and pH of <7.0 is common

Answer 150

Hypocalcemia commonly develops during prolonged CPA. Because calcium is essential for skeletal and smooth muscle function, hypocalcemia can have detrimental effects on cardiac function and vascular tone.

Answer 151

Myocardial Ischemia Due to decreased blood flow, myocardial ischemia and necrosis can develop with prolonged CPA. Achieving ROSC is more difficult when the myocardium becomes ischemic, and the heart becomes resistant to defibrillation if VF or pulseless VT develops, making survival less likely.

Answer 152

Asystole and PEA are considered prolonged after 10 minutes. Often, it is impossible to know the duration of CPA if the initial CPA was unobserved. In the case of an unwitnessed arrest, consider the arrest time to be the time CPR was initiated.

Answer 153

Sodium bicarbonate is a potent alkalizing agent,

Answer 154

However, administration of sodium bicarbonate can result in an increase in serum osmolarity, alkalemia, and potentially a paradoxical cerebral and metabolic acidosis.

Answer 155

Therefore, it should be reserved for use only in cases of prolonged CPA, and preferably in animals in which severe metabolic acidosis has been explicitly diagnosed by blood gas analysis.

Answer 156

α-1 receptors are more responsive to catecholamines at a physiological pH (near 7.40). In cases of prolonged CPA with documented metabolic acidosis, sodium bicarbonate therapy may be useful to maximize the effectiveness of epinephrine.

Answer 157

Excessive bicarbonate therapy during CPR in dogs has been associated with pH values of up to 7.8 and dissociation between arterial and CSF pH that might contribute to post-CPR cerebral depression

Answer 158

Therefore, judicious use of sodium bicarbonate, preferably only after documentation of severe metabolic acidosis (pH less than 7.0) with blood gas analysis, is warranted.

Answer 159

Bicarbonate may be administered at 1 mEq/kg IV or IO if you document a pH < 7.0. It should not be administered IT because it is not effective and can lead to pulmonary irritation

Answer 160

If hyperkalemia is documented during CPR, treatment with 10% calcium gluconate IV (0.5 mL/kg) is recommended. This therapy normalizes the difference between resting membrane potential and threshold potential in cardiac cells.

Answer 161

If hypocalcemia is documented during CPR, administration of 10% calcium gluconate IV (0.5 mL/kg) is reasonable to improve cardiac contractility and vascular tone.

Answer 162

BLS . Although ALS interventions should be initiated as soon as possible, the first step for any patient in CPA is to start BLS.

Answer 163

Atropine and low dose epinephrine . Lexi was documented to have sinus bradycardia just before she developed asystole, likely due to high vagal tone from her episode of vomiting. Vasopressor therapy is the highest ALS priority when treating patients with asystole. Because Lexi likely had a vagally mediated CPA, atropine should be administered at the same time as the epinephrine. Because Lexi had an ECG monitor in place at the time she developed CPA and the arrest rhythm (asystole) was diagnosed, you should not wait until the end of the next cycle to administer ALS therapies.

Answer 164

High dose epinephrine . Vasopressors (epinephrine and vasopressin) are the mainstay of treatment for asystole and PEA, and anticholinergics, such as atropine, may also be helpful during CPR (in animals experiencing bradycardic arrest due to high vagal tone). In cases of prolonged CPR, high-dose epinephrine may be administered. The use of sodium bicarbonate should be avoided unless there is a blood gas indicating severe acidosis, and routine use of calcium gluconate is not recommended unless you have documented low calcium.

Answer 165

calcium gluconate If hyperkalemia is documented during CPR, treatment with 10% calcium gluconate IV (0.5 mL/kg) is recommended. This therapy normalizes the difference between resting membrane potential and threshold potential in cardiac cells. Sodium bicarbonate is only indicated in patients with severe acidemia (pH less than 7.0). Dexamethasone is only indicated in patients with documented adrenal insufficiency. Peripheral venous CO2 is a poor surrogate for arterial CO2 during CPR because poor peripheral blood flow reduces CO2 clearance. Ventilatory rate should be maintained at 10 breaths per minute regardless of the peripheral CO2 partial pressure. Finally, low-dose epinephrine and vasopressin are part of the standard ALS algorithm.

Answer 166

Pulseless electrical activity

Answer 167

Achieve peripheral vasoconstriction

Answer 168

Atropine should be administered every other cycle of CPR

Answer 169

Vasopressin

Answer 170

start chest compressionsTrue

Answer 171

non-shockable

Answer 172

start chest compressions

Answer 173

Because VF and VT are the result of abnormal pacing of groups of ventricular myocardial cells by the myocardial cells themselves rather than the natural pacemakers, the goal of electrical defibrillation is to depolarize as many of these cells as possible, driving them into their refractory period and stopping the ineffective activity. This means that the ultimate goal of electrical defibrillation is to stop all electrical and mechanical activity in the ventricles in order to permit the resynchronization of the electrical activity of the heart.

Answer 174

If defibrillation is successful, the natural pacemakers (the SA node and/or the AV node) should then begin driving the myocardial cells, which may permit the return of a perfusing rhythm. In other words, the goal of defibrillation is to stop the chaotic activity in order to permit synchronized contraction to occur, guided by either the sinus node or another of the natural cardiac pacemakers.

Answer 175

Three approaches to defibrillation have been described: Electrical Mechanical Chemical

Answer 176

There is extensive evidence showing that of the 3, electrical defibrillation is by far the most effective approach. Although we will discuss each of the options for defibrillation, if an electrical defibrillator is available, the other 2 types of defibrillation should never be used.

Answer 177

– Recall that ventricular fibrillation is chaotic, uncoordinated electrical activity and contraction of ventricular myocardial cells, causing the heart to quiver. There is no cardiac output and no blood flow to the tissues.

Answer 178

Electrical Defibrillation – Electrical defibrillation is accomplished by a device that delivers an electric shock to the heart via either chest paddles or adhesive patches for external defibrillation or internal paddles directly on the ventricles for internal defibrillation.

Answer 179

Mechanical Defibrillation – Mechanical defibrillation may be attempted using a precordial thump. Unfortunately, recent studies have shown the precordial thump to have minimal effects on ventricular fibrillation, and this procedure is only recommended if an electrical defibrillator is not available. Do not thump if you have a defibrillator.

Answer 180

Chemical Defibrillation – Chemical defibrillation using acetylcholine/potassium chloride, bretylium tosylate, lidocaine, and magnesium have been described in the experimental literature, but have not been shown to be useful in any clinical studies, and several have been shown to reduce the efficacy of electrical defibrillation. Therefore, chemical defibrillation is not recommended.

Answer 181

Electrical defibrillation is the most effective treatment for VF and pulseless VT.

Answer 182

There are two types of electrical defibrillators: Monophasic Biphasic

Answer 183

Automated electrical defibrillators (AED), which are widely available for use in sudden cardiac arrest in people, may potentially be useful in dogs, but because they deliver a standard adult human energy dose and were developed using ECGs collected from humans, their applicability in dogs and cats is unknown. In addition they use adhesive pads rather than paddles, requiring shaving before use. Therefore, the use of manual defibrillators with variable dosing is recommended for veterinary patients. A large amount of energy is required to simultaneously depolarize the majority of ventricular myocardial cells with electrical current administered to the body surface. This large amount of energy can lead to myocardial injury. The lowest potentially effective defibrillator dose should always be used to minimize injury.

Answer 184

Biphasic defibrillators can successfully terminate VF at lower defibrillation energy than monophasic defibrillators, in turn leading to less myocardial injury. Therefore, biphasic defibrillators are preferred if they are available.

Answer 185

Although electrical defibrillation is the most effective treatment for VF and pulseless VT, it requires a large amount of electrical energy to be applied to the heart. This can lead to myocardial injury, the severity of which is proportional to the amount of energy applied.

Answer 186

Devices for delivering a shock to the patient include hand paddles, posterior paddle assemblies, pediatric hand paddle inserts, adhesive patches, and internal defibrillation paddles for use during open-chest CPR.

Answer 187

When using hand paddles, they should be placed on opposite sides of the thorax approximately over the costochondral junction directly over the heart.

Answer 188

When using hand paddles, they should be placed on opposite sides of the thorax approximately over the costochondral junction directly over the heart. This allows the maximum amount of current to pass directly through the ventricles, increasing the likelihood of successful defibrillation. To accomplish this, the patient must be placed in dorsal recumbency. Sufficient electrode gel or paste must be applied to the paddles to ensure electrical contact with the skin, and animals with long hair may need to be shaved to achieve contact. The paddles must be pressed firmly against the chest wall to ensure contact. Alcohol, which is highly flammable, should never be used in place of electrode paste or gel

Answer 189

A posterior paddle assembly, which is a flat paddle replacement for one of the hand paddles, can improve the efficiency and safety of defibrillation, minimizing the interruption to compressions and eliminating the need to place the patient in dorsal recumbency. The flat paddle is coated with gel or paste and placed under the patient’s thorax. Defibrillation is then accomplished using a standard hand paddle on the upward facing chest wall. Chest compressions can resume immediately while the posterior paddle is still in place.

Answer 190

For cats and small dogs, pediatric hand paddle inserts are recommended if available, to direct more of the current through the heart. The large surface area of the adult paddles may lead to more current bypassing the heart through the skin and subcutaneous and muscle tissues, decreasing effective dose delivery. If pediatric paddles are not available, use of the adult paddles is acceptable.

Answer 191

Adhesive defibrillation patches can be used in dogs and cats but they require the chest to be shaved in order for contact to be achieved. This may result in prolonged delays in chest compressions, and should only be used if hand paddles or a posterior paddle assembly are not available.

Answer 192

During open-chest CPR, defibrillation is accomplished using internal defibrillation paddles. These paddles are much smaller than devices used for external defibrillation. It is also important to use a lower dosing scheme for internal defibrillation to avoid serious myocardial injury. If you have internal paddles, be sure that your chart includes a separate dosing scheme for internal defibrillation. Before use, internal defibrillation paddles may be wrapped in 0.9% saline-soaked gauze to facilitate contact with the ventricles, if desired. The paddles should be placed on either side of the ventricles and firmly pressed against the heart to facilitate contact. Between uses, the paddles should be sterilized according to manufacturer recommendations and kept in sterile packaging in the crash cart.

Answer 193

Electrical Phase During the first four minutes after the onset of CPA, known as the electrical phase, ATP stores in the heart are usually sufficient to sustain cell membrane potentials and metabolic demands, which minimizes ischemic damage.

Answer 194

Circulatory Phase The next six minutes are called the circulatory phase, during which reversible ischemic injury due to ATP depletion occurs

Answer 195

Metabolic Phase After 10 minutes without perfusion, the metabolic phase begins, which is characterized by potentially irreversible ischemic injury.

Answer 196

Early electrical defibrillation is associated with better outcomes, but in some cases, one full cycle of BLS should be administered before defibrillating. Once circulation to the tissues ceases in a patient in CPA, ischemic injury to the tissues begins.

Answer 197

Witnessed, Monitored Arrests – Patients experiencing sudden CPA while being monitored with an ECG and noted to convert from a perfusing rhythm into VF or pulseless VT are in the initial electrical phase and have experienced minimal ischemic injury. The heart is capable of re-establishing a perfusing rhythm quickly if the VF or pulseless VT can be terminated immediately. Therefore, BLS should be initiated and continued only long enough to charge the defibrillator. Once the defibrillator is charged, the patient should be defibrillated immediately. After the defibrillation, BLS should be restarted and continued for a full cycle before rechecking the ECG, unless other signs of ROSC develop, such as a sudden increase in EtCO2 or development of palpable pulses.

Answer 198

Unwitnessed Arrests – Patients discovered in CPA with an initial arrest rhythm of VF or pulseless VT diagnosed before initiation of BLS should receive a full two-minute cycle of BLS before defibrillation. Because of the likelihood that the patient with an unwitnessed arrest has entered the circulatory or metabolic phase, a full cycle of BLS will provide perfusion to the heart and restoration of ATP stores, increasing the likelihood of a successful defibrillation. Shocking an ischemic heart depleted of ATP is unlikely to restore a perfusing rhythm and will result in additional myocardial injury. Note that if the RECOVER algorithm is being followed, this circumstance should not occur, as BLS should be started before an ECG monitor is attached.

Answer 199

Shockable Rhythm Diagnosed during an Inter-cycle Pause in BLS – If a shockable rhythm is diagnosed after a full two-minute cycle of BLS, during the brief inter-cycle pause in chest compressions, BLS should be resumed immediately and continued only as long as it takes to charge the defibrillator, at which time BLS should be paused and the patient defibrillated. Because perfusion of the heart has been provided by the BLS delivered during the previous cycle, the patient is in the electrical phase and immediate defibrillation is warranted.

Answer 200

If electrical defibrillation is successful, there will be no blood flow out of the heart, so it's very important to restart BLS immediately after the electrical defibrillation attempt.

Answer 201

After each defibrillation attempt, BLS should be resumed immediately and continued for another two-minute cycle. The patient can be assessed for evidence of ROSC during this cycle by pulse palpation and EtCO2 monitoring, but resumption of BLS should not be delayed to interpret the ECG, as direct conversion to a perfusing rhythm may not have occurred and longer pauses in chest compressions are associated with worse outcomes. Note that this is in contrast to older CPR guidelines, which recommended three stacked shocks in patients with VF that did not respond to an initial defibrillation attempt. More recent studies have shown poorer outcomes with a stacked shock approach, likely due to the lack of perfusion during the repeated defibrillation attempts in the absence of continued BLS.

Answer 202

Note that, in contrast to drug administration for the non-shockable rhythms, which is repeated every other cycle of BLS (every 3-5 minutes), defibrillation for the shockable rhythms should be repeated every cycle of BLS (every 2 minutes).

Answer 203

– If the patient is still in VF or pulseless VT at the end of the two-minute cycle of BLS, the defibrillator dose may be increased by 50% and the patient defibrillated again, followed immediately by another two-minute cycle of BLS. The dose may be increased each time defibrillation is attempted at the end of each two-minute cycle of BLS, to a maximum dose of 10 J/kg. The evidence for dose escalation is stronger for monophasic defibrillators than for biphasic defibrillators. Two-minute cycles of BLS followed by electrical defibrillation should be repeated until ROSC is achieved, conversion to a non-shockable rhythm (asystole or PEA) occurs, or the CPR attempt is abandoned.

Answer 204

Avoid Alcohol Alcohol, which is occasionally used to facilitate ECG recording, should be avoided during CPR, as it is highly flammable and could cause a skin burn or the fur to catch fire if VF or pulseless VT develops and electrical defibrillation is indicated. Electrode gels and pastes are non-flammable and should be used during CPR to improve ECG electrode contact.

Answer 205

Call Out “CLEAR” The individual operating the defibrillator should be careful to call out “CLEAR” prior to delivering the charge, and should ensure that all personnel are away from the patient and treatment table before delivering the shock. “CLEAR” is the signal to stop touching the patient OR any object that might conduct electricity, such as metal treatment tables or pools of fluid making contact with the patient. When the person operating the defibrillator calls out “CLEAR”, it means that they are confident that they can maintain the animal in the same position (i.e., dorsal recumbency) when everyone else lets go of the animal.

Answer 206

Avoid Contact The person administering the shock is at the highest risk from the procedure. When two hand paddles are used, care should be taken to avoid contact with the patient’s limbs, as they have a tendency to rest on the rescuer when the patient is held in dorsal recumbency. The use of exam gloves may reduce the risk of shock, but care must be taken to prevent electrode gel or fluid from forming a bridge over the glove to the rescuer’s forearm. In addition, the rescuer should avoid leaning on the treatment table, which could also form a conductive path between the patient and the rescuer.

Answer 207

The precordial thump delivers 5–10 joules of energy to the heart.

Answer 208

– A precordial thump is performed by striking the chest directly over the heart. The location of the heart can be estimated by pulling the elbow caudodorsally over the chest until it is roughly at the level of the costochondral junction. This will be over the third to fifth intercostal space. In medium to large breed dogs, the rescuer should strike the chest with as much force as possible. In small dogs and cats, care should be taken to not overly traumatize the heart.

Answer 209

The goal of anti-arrhythmic therapy is to terminate the pathological rhythm by acting on specific parts of the cardiac cycle. While anti-arrhythmic therapies are commonly used in patients with ectopy, their role in CPR is less well established.

Answer 210

The two most extensively studied anti-arrhythmic drugs for prolonged pulseless VT and VF are Amiodarone and Lidocaine.

Answer 211

The two most extensively studied anti-arrhythmic drugs for prolonged pulseless VT and VF are Amiodarone and Lidocaine. Amiodarone is believed to be the most effective for increasing the rate of ROSC with electrical defibrillation in patients with pulseless VT or VF. However, lidocaine may be considered as an alternative if amiodarone is not available, as it is much more widely available in veterinary practices, and specific veterinary benefits of amiodarone over lidocaine have not been established.

Answer 212

Remember that all anti-arrythmic drugs have the potential to be arrhythmogenic, so administration of anti-arrhythmic therapy in conjunction with electrical defibrillation should only be considered in patients with refractory VF or pulseless VT lasting at least 10 minutes (5 cycles of BLS).

Answer 213

It is useful for treatment of stable ventricular tachycardias as well as during CPR in conjunction with electrical defibrillation for prolonged VF/pulseless VT

Answer 214

Amiodarone is a class III anti-arrhythmic agent and prolongs phase 3 (the repolarization phase) of the action potential in cardiac cells. However, it has other anti-arrhythmic properties as well, such as beta blocking and potassium-channel blocking in the SA and AV nodes, slowing the pacemakers and atrial-ventricular conduction.

Answer 215

Dosing – During CPR, amiodarone may be given slowly IV/IO over 1–2 minutes at a dose of 5 mg/kg. If possible, it should be diluted to 0.5 mg/ml with D5W prior to administration. It should not be given IT.

Answer 216

Side Effects – The major potential side effect is anaphylaxis, leading to hypotension and severe hives (urticaria) due to the vehicle in some formulations of the drug. This is less likely with the aqueous amiodarone solution, which is the preferred formulation for use in dogs. Patients demonstrating these signs upon ROSC should be given diphenhydramine (2 mg/kg IM) and dexamethasone SP (0.1 mg/kg IV). Vasopressors may be considered if hypotension develops. Newer preparations are less likely to cause anaphylaxis.

Answer 217

– In people, prolonged VF and pulseless VT respond better to amiodarone than to any other drug, or to repeated attempts at electrical defibrillation without additional antiarrhythmic therapy. The clinical utility of amiodarone in veterinary patients is unknown, but there is some experimental evidence that it is beneficial in dogs with prolonged VF/pulseless VT. If available, in prolonged VF/pulseless VT, amiodarone should be administered. If amiodarone is not available, lidocaine may be considered in these patients.

Answer 218

Lidocaine is a class 1B antiarrhythmic that blocks fast sodium channels in the ventricular myocardium, shortening the action potential and slowing the ventricular rate.

Answer 219

Like amiodarone, lidocaine is useful for treatment of stable ventricular tachycardias as well as during CPR in conjunction with electrical defibrillation for prolonged VF/pulseless VT. In unstable VT, lidocaine administration may increase the fibrillation threshold, preventing deterioration of VT into VF.

Answer 220

One study using monophasic defibrillation showed that after VF developed, treatment with lidocaine increased the energy required to successfully electrically defibrillate the dogs. More recent data in humans and pigs showed that lidocaine actually decreased the defibrillation threshold with biphasic defibrillation, resulting in successful defibrillation with lower energy in patients with prolonged VF. Due to lidocaine’s widespread availability, it is a reasonable drug to consider for adjunctive therapy for prolonged VF/pulseless VT (longer than 10 minutes, or 5 cycles of BLS) if biphasic defibrillation alone is not successful despite high-quality BLS and ALS interventions. If a monophasic defibrillator is being used, lidocaine may be given, but it may require higher defibrillation energies to be effective

Answer 221

During CPR, vasopressors provide peripheral vasoconstriction, which diverts blood from the periphery to the core, improving myocardial perfusion

Answer 222

During CPR, vasopressors provide peripheral vasoconstriction, which diverts blood from the periphery to the core, improving myocardial perfusion. However, peripheral vasoconstriction increases afterload, potentially decreasing cardiac output. Catecholamines like epinephrine can potentially worsen arrhythmias like VT and VF. For this reason, vasopressors are only recommended in patients with prolonged VF and pulseless VT (greater than 10 minutes, or 5 cycles of BLS).

Answer 223

Epinephrine is the most commonly used vasopressor during CPR, but as described in Module 2 (Treating the Patient: Asystole and PEA), ephinephrine is an agonist at all adrenergic receptors. Therefore, in addition to peripheral vasoconstriction, substantial β-1 agonism occurs, which has the potential to worsen ventricular arrhythmias in patients with VF/pulseless VT. Therefore, low-dose epinephrine (0.01 mg/kg IV/IO/IT every 3–5 minutes) is reserved for patients with VF/pulseless VT that has been refractory for at least five cycles of BLS and electrical defibrillation (longer than 10 minutes). High dose epinephrine (0.1 mg/kg) is not recommended for treating shockable arrest rhythms because of the potential to worsen the arrhythmia due to the β-1 effects

Answer 224

Vasopressin (0.8 IU/kg IV/IO/IT every 3–5 minutes) may be preferable to epinephrine in patients with prolonged VF/pulseless VT, as it does not require a normal pH for efficacy, and it acts only as a vasopressor, without the β-1 effects that may worsen ventricular arrhythmias in these patients. However, studies comparing epinephrine to vasopressin for patients with prolonged VF/pulseless VT are lacking.

Answer 225

Administer a slow IV bolus of lidocaine

Answer 226

Immediately resume chest compressions and defibrillate again if the patient is still in VF at the end of the next BLS cycle.

Answer 227

Amiodarone IV

Answer 228

Using alcohol on ECG clips