CPR Maike Bachmann, DVM

October 2012

Goals of the lecture

• In the human and animal field, when giving a patient CPR the goal is to have the patient survive and be neurologically be sound. Cardiopulmonary arrest in our patients is commonly associated an underlying illness, trauma, or anesthesia. The Survival to discharge after cardiopulmonary arrest is uncommon in veterinary medicine ranging from 3% -6% in dogs and 2%- 10 % in cats

• In this lecture there will be an introduction to RECOVER, a recently developed campaign on Veterinary Resuscitation. It is the goal of this campaign to design a consensus based clinical CPR guidelines for small animal medicine. We are then going then delve into a discussion on basic life support, advanced CPR, monitoring, and post resuscitation care. We will finish the lecture with a discussion on clinical guidelines for CPR, some which we have instituted in this hospital and some which will be instituted as we continue forward.

Recover

• This is an evidence and knowledge gap analysis on Veterinary CPR.

• The goal of RECOVER was to establish a better way of providing “CPR” to our patients with the outcome being survival with intact neurological function following cardiac arrest

• The goal is standardizing training goals and improved outcomes for our veterinary patients.

• Preparation and Prevention

• Basic Life support

• Advanced life support

• Monitoring

• Post cardiac arrest care

• Clinical guidelines

Basic Chain of Survivial

• Early recognition, Basic Life support, Advanced life support, Post-resuscitation care

Preparation and prevention

• Organized and pre-stocked arrest stations these should also be close to areas where animals are anesthetized- check lists, charts, and aids

Anesthetized CPA had a better outcome then CPA

• Post-CPR debriefing is safe, easy, and improves future performances

• Training increase effectiveness of CPR test standardized training programs have improved adherence to guidelines in human medicine and are needed in veterinary medicine.

• Leadership and team communication training increases effectiveness of CPR teams

• High fidelity manikins for teaching CPR are highly effective in human medicine and would be valuable in veterinary medicine

Identifying patients at risk

• Rapid recognition of CPA and Rapid initiation of CPR

Identifying the 5 H’s and 5 T’s

• 5 H’s• Hypovolemia/hemorrhage

• Hypoxia/hypoventilation

• Hydrogen ions/acidosis

• Hyperkalemia - blocked cats or hypokalemia

• Hypoglycemia

• 5 T’s• Toxins

• Tension pneumothorax

• Thromboembolism or Thrombosis

• Tamponade ( pericardial effusion)

• Trauma

Basic Life support

BLS is the immediate response to CPA•Basic life support (BLS) includes recognition of cardiopulmonary arrest (CPA), airway management, provision of ventilation, and chest compressions. •Early Initiation of high- quality basic life support is essential to create blood flow to the heart and brain as well as to limit injury to or preserve organs until spontaneous circulation resumes •BLS is separate from advanced life support (ALS)•Minimal monitoring equipment can be initiated immediately at the onset or arrest

• Immediate initiation of chest compressions with intubation and ventilation being performed simultaneously

• In human medicine studies have shown that delayed initiation of chest compressions due to prolonged intubation times have a potential negative impact

• Chest compressions should aim to compress the chest by 1/3 to half its width in lateral recumbency, at a rate of at least 100 compressions/min, allow for full recoil between compressions

• High compression rates could limit the duration of diastolic cornonary perfusion and impair recoil decompression, thereby compromising venous return.

• Optimal closed chest compressions only produce 25% to 40 % of normal cardiac output

• Utilization of the 2 minute cycles of uninterrupted chest compressions with alternation of compressors between cycles. Intercycle interruptions in compressions should be kept to a minimum; long only enough for rhythm diagnosis

Chest compression technique

Chest compression techniques for medium, large, and giant breed dogs. •(A) For most dogs, it is reasonable to do chest compressions over the widest portion of the chest to maximally employ the thoracic pump theory. •Either left or right lateral recumbency are acceptable. •(B) In keel-chested (ie, deep, narrow chested) dogs like greyhounds, it is reasonable to do chest compressions with the hands directly over the heart to employ the•cardiac pump theory, again in either recumbency. •(C) For barrel chested dogs like English Bulldogs, sternal compressions directly over the heart with the patient in dorsal recumbency may be considered to employ the cardiac pump mechanism.

• Cardiac pump –directly exert force on the heart and generate force on the heart and generate blood by changing the dimension of the individuals cardiac chambers

• Thoracic pump – increased intrathoracic pressure during chest compressions , secondarily compressing the aorta and collapsing the vena cava leading to blood flow out of the thorax

• Sternal compression – dislocates the costalchondral junctions –cardiac pump mechanism established

Chest compressions for small animals < 10 kgs

Chest compression techniques for small dogs and cats.•A) For most cats and small dogs (<10 kg) with compliant chest. The use of a 1-handed technique to accomplish circumferential chest compressions with the hand wrapped around the sternum directly over the heart may be considered. •(B)An alternative chest compression method for cats and small dogs is the 2-handed technique directly over the heart to employ the cardiac pump mechanism. This method may be considered in larger cats and small dogs with lower thoracic compliance, or in situations in which the compressor is becoming fatigued while doing 1-handed compressions.

• Controlled airway, usually via ET intubation

• ventilation rate of 10 breaths/min without interruption of chest compressions

• Acceptable tidal volume per breath is 10ml/kg with a 1 second inspiratory time

• Why not give more?

• What is the driving force for a breath?

( what we are targeting is normocapnia will avoiding arterial hypoxemia )

If you are by yourself – BLS

The ratio of chest compressions to Breath is

30:2

Advanced Life Support (ALS)

• The RECOVER ALS program was designed to evaluate the vasopressors, positive inotropes, anticholinergics, correction of electrolyte disturbances, volume deficits, severe anemia, and prompt defibrillation.

• If BLS and ALS are performed promptly, initial return of spontaneous circulation rate may be as high as 50% in dogs and cats

ALS key recommendations

• Standard dose epinephrine (0.01 mg/kg IV ) is the preferred dose for CPR – easy way to do the math = a dog weighs 5.0 kgs move the decimal point over to the left twice and you will get the ml’s of epinephrine that need to be given to a patient. • ( epi is 1 mg /ml )

• Rapid defibrillation is warranted in animals with observed progression to pulses of VT or VF, preferentially using a biphasic (BP) defibrillator

• Biphasic – current flows in one direction in the first phase of the shock and then reverses for the 2nd phase. – Gold standard device. They pose less risk of injury to the heart.

• Defibrillation should follow a cycle of CPR in unwitnessed pulses VT or VF

• Reversal of anesthetic agents can correction of acid –base electrolyte disturbances is advisable

Turn off the inhalant

• Open chest CPR might be considered in select cases with access to postcardiac arrest support

Vasopressors and vagolytic therapy

• A crucial aspect of restoring myocardial function is improving coronary perfusion pressure

• Vasopressors increase aortic pressures by increasing peripheral vascular resistance directing more of the intravascular volume to the central circulation.

• Vagolytic therapy, specifically atropine, should be used to counteract high vagal tone.

• Epinephrine• Standard recommendations ( 0.01 mg/kg/IV ) q. 3-5 minutes

• Vasopressin • 0.8 U/kg IV • with or without epinephrine is an appropriate intervention in

CPR• Vasopressin my benefit in patients with prolonged CPA, asystole,

or CPA with associated hypovolemia • Atropine • Data supports that the use of atropine during CPR is limited. Most

studies use it as an additional drug, rather than a sole drug• For animals with high vagal tone ( vomiting, ileus) subsequent

bradycardia/asystole

• Evidence suggests that low- dose epinephrine and vasopressin are first line pharmacologic agents in CPR, providing peripheral vasoconstriction to improve blood flow to heart, brain, and enhanced the change for recovery

Other medication

• Antiarrhythmic drugsIn cases of asystole, PEA, pulseless VT and VF

There is no compelling evidence that supports the routine use of antiarrhythmic drugs improve outcome of dogs and cats with cardiac arrest.

• Steroid • There is no evidence that corticosteroid administration is

beneficial or harmful in the ALS phase of CPR.

• Studies suggest that in other diseases it has a harmful effect

• At this time it is not recommended to use steroids in patients that you are providing CPR to

• Naloxone• In dogs and cats with cardiac arrest and suspected narcotic

depression secondary to opioids naloxone may be beneficial

• There are 2 perspectives for the use of naloxone

1. use in opioid overdoses

2. positive inotrope and antiarrhythmic mediated by reversal of endogenous endorphins.

Electrolyte Disturbances

• Electrolyte disturbances associated with CPA may exist prior to the arrest or may develop during CPR subsequent to metabolic acidosis, drug therapy, or other metabolic derangements. • There is no evidence that suggests treatment to mild

electrolyte disturbances. • Moderate to severe hyperkalemia influences myocardial

function and should be treated. *Blocked cats*• Severe ionized hypocalcemia may be treated and calcium

therapy is warranted in symptomatic calcium channel blocker overdosage

Calcium

• Calcium is vital in cellular communication ( signaling ) as well as muscle contraction in skeletal, cardiac, and smooth muscles. Adequate calcium concentrations are required or cardiac contractility

• There is a clear relationship between low ionized calcium levels and poor outcome in CPR.

Defibrillation

• In dogs and cats with cardiac arrest due to VF or pulseless VT the use of prompt defibrillation is associated with a markedly higher rate of chance for survival.

• BP defibrillation is preferable to monophasic defibrillation.

• Selection of the appropriate energy level for an animal size device • Monophasic 5+/- 1 J/kg

• Biphasic 3 +/- J/Kg

• Minimize of impedance by creating optimal contact between the paddles and the chest

• There is less evidence that stacking shocks is beneficial and rather one shock followed by compressions for 2 minutes etc. Has a better outcome – this minimizes the time without blood flow and reduces myocardial hypoxemia

• Any Subsequent shocks should be increased by 50% once should be considered.

Timing of defibrillation

• Evolving Concepts in CPR support the 3 –phase model of CPR• 1st pahse lasting approximately 4 minutes and termed the

electrical phase

• 2nd phase, the circulatory occurs between 4-10 minutes after CPA and is associated with energy depletion and potentially reversible cellular damage

• 3rd After 10 minutes of no circulation, the metabolic phase begins, and is characterized by ischemia injury that require more advanced strategies then BLS and ALS

• Immediate defibrillation is warranted if the duration of VF is 4 minutes or less

• In arrests that have lasted longer then 4 minutes, one cycle of CPR before defibrillation may help replenish energy substrates and increase the likelihood of successful defibrillation

Other ALS topics

• Open chest CPR• Open chest compression is more effective than closed chest

CPR

• In open- chest CPR requires a skillful team and demands advanced postcardiac arrest support

• In cases of significant intrathoracic disease, such as tension pneumothorax or pericardial effusion, it may be advisable to promptly perform open –chest CPR.

• Defibrillation should be readily available.

Intravenous vs. intratracheal drug administration

• Faced with the lack of venous or IO access, intratracheal administration of epinephrine, atropine, and vasopressin may be considered.

• If it is chosen, a 10 fold increase in the dose of Epi. ( 0.1 mg/kg) should be given

• It should be delivered via a catheter to the level of the carina or ideally farther distal into the bronchial tree.

• The drug should be diluted in sterile water ( saline cane by used )

Anesthetic –related arrest

• Animals under anesthesia should be resuscitated aggressively

• Careful monitoring during anesthesia may permit more rapid recognition and potentially improve outcome.

• Lipid rescue may be considered in animals with CPA due to local anesthetic drugs or in association with other lipophilic drugs.

Monitoring

• Monitoring is divided into 3 important aspects of CPR• Confirm CPA and endotracheal intubation

• Monitoring options during CPR

• Monitoring options following return to spontaneous circulation

• Time spent verifying an absent pulse may delay onset of CPR; chest compression should be initiated immediately for apneic, unresponsive patients• Palpation of FP versus assessment for other signs of life pupil size,

agonal breathing, thoracic auscultation• Loss of FP and radial artery doppler signal may occur before

complete cardiac arrest. Doppler pulse sounds are not a reliable tool for the dx of cardiac arrest.

• ECG analysis of unresponsive patient may help to rule out CPA, or be used to evaluate for rhythms requiring specific therapeutic approaches. Pauses in chest compressions to evaluate the ECG rhythm should be minimized• Enables identification of rhythms that can be treated with

defibrillation

• End- tidal CO2 may be used to identify Et placement. And to evaluate efficacy of CPR. Under physiologic conditions, PETCO2, severs as a close est. of the alveolar partial pressure of CO2. PETCO2 is very responsive and sensitive indicator that almost immediately increases upon ROSC .

• EtCO2 monitoring is useful to identify ROSC and may be prognostic for the likelihood for ROSC

• When a PETCO2 remains < or equal to 10 mmHg despite maximal effort and the ECG is not showing electrical activity discontinuation of the resuscitation attempt can be considered.

• Patient monitoring following ROSC should be directed at identifying abnormalities that may portend another CPA, and should be tailored to each patient

• Blood pressure monitoring – noninvasive monitoring such as the doppler sphygmomanometry or oscillometric methods are not useful to evalute CPR but have a role in postresuscitation care. Arterial catheters are impractical to place during CPR, however be useful during postresuscitation care.

• Venous blood gas may have a better predictor value for for ROSC than arterial blood gas values are directly related to cardiac output and tissue perfusion (there is evidence that venous mixed blood gas values changed to a greater degree during the resuscitation period than did the arterial samples.

• In cases where there is cardiac arrest due to electrolyte abnormalities, the measurement of serum electrolytes may allow for direct therapy in addition to standard CPR.

Post cardiac arrest

• Hemodynamic optimization protocols during the CPA phase are clinically feasible and potentially useful in unstable animals- CO instability after CPA can be attributed to the disease. To maintain adequate organ perfusion following ROSC.

• There is good evidence to advocate normoxemia versus hyperoxemia or hypoxemia in the early PCA period

• Evidence suggests neurological benefit of mild hypothermia (33+/- 1’C) in the early postresuscitation period, and that fast rewarming after induced or uninduced hypothermia may be harmful

• There is no evidence to support routine administration of corticosteroids, anti-seizure medication, mannitol, or metabolic protectants after cardiac arrest

• Low –dose corticosteroid tx in patients with persistent hypotension requiring sympathomimetic support may be considered – addisons disease

• Hypertonic saline may be considered in animals that are suspected in having cerebral edema as evidenced by coma or obtundation after cardiac arrest

• More PCA care in a specialty center with advanced monitoring may have outcome benefits

• The goal in PCA is hemodynamic optimization• Fluid

• Pressors

• Central venous blood oxygen saturation

• Blood lactate

• CVP/Arterial pressures

• Fluid therapy there is no evidence currently that supports or does not support fluid support post ROSC

• There is not evidence the particular pressor usage compared to standard care results in better outcome.

• Support of ventilation and oxygenation

Rapid normalization of blood oxygen, carbon dioxide, pH, and reoxygenation of ischemic tissue is the primary objective in PCA period.

• Oxygen supplementation

There is good evidence to advocate for normoxia/normoxemia vs hyperoxemia in early PCA

• Hypothermia after Cardiac Arrest

Lowering the patients’s core temperature to 32-34’C is widely used in human patients that are in a coma.

There is a beneficial effect on neurologic intact survival of mild hypothermia ( core temperature of 33+/- 1’C ) institutes as soon as possible and maintained for >12 hours.

• Rewarming rate after cardiac arrest

• Slower rewarming rates of rewarming after accidental or therapeutic hypothermia, slower rewarming rates appear preferred over a faster rate.

• Neuroprotective, metabolic, and supportive strategies

There is no evidence to support routine administration of corticosteroids, anti-seizure medication, mannitol, or metabolic protectants after cardiac arrest

Low –dose corticosteroid tx in patients with persistent hypotension requiring sympathomimetic support may be considered – addisons disease

Hypertonic saline may be considered in animals that are suspected in having cerebral edema as evidenced by coma or obtundation after cardiac arrest

Cardiac algorithm

• CPR algorithm chart. This chart summarizes the clinical guidelines most relevant to the patient presenting acutely in CPA. The box surrounded by the grey dashed line contains, in order, the initial BLS and ALS actions to be taken when a patient is

• diagnosed with CPA:

• (1) administration of chest compressions,

• (2) ventilation support,

• (3) initiation of ECG and EtCO2 monitoring,

• (4) obtaining vascular access for drug administration, and

• (5) administration of reversal agents if any anesthetic/sedative agents have

• been administered.

• The algorithm then enters a loop of 2-minute cycles of CPR with brief pauses between to rotate compressors, to evaluate the patient for signs of ROSC, and to evaluate the ECG for a rhythm diagnosis.

• Patients in PEA or asystole should be treated with vasopressors and, potentially, anticholinergic drugs. These drugs should be administered no more often than every other cycle of CPR.

• Patients in VF or pulseless VT should be electrically defibrillated if a defibrillator is available, or mechanically defibrillated with a precordial thump if an electrical defibrillator is not available.

• Immediately after defibrillation, another 2-minute cycle of BLS should be started immediately.

Post Cardiac Arrest Care

• Figure 2: Post-cardiac arrest (PCA) care algorithm. This chart summarizes a comprehensive treatment protocol for PCA care that

• includes components of controlled ventilation and oxygenation, goal-directed hemodynamic optimization, and neuroprotective strategies.

• The sequence shown reflects the order in which each component should be assessed and treatment initiated. Assessment and

• initiation of treatment for the subsequent component will likely commence before the endpoints of the previous component have been completely met. Thus respiratory, hemodynamic, and neuroprotective treatment strategies will be initiated in parallel in most cases.