**5.3 Extracorporeal CPR (ECPR)**

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capnography.

**5. Circulation support**

hospital cardiac arrest.

**5.2 Mechanical CPR devices**

added advantage of using this device [56, 57].

unsuccessful in emergencies with high chances of unrecognized-esophageal intubation. Comparatively, insertion of supraglottic devices is easier. A stepwise approach to airway management including bag and mask, supraglottic devices, and the endotracheal tube is commonly followed during CPR. This stepwise approach has

One of the serious complication in airway management during CPR is unrecognized esophageal intubation. There are few methods of confirming the correct placement of endotracheal tube which have been applied and tested in various settings. Waveform capnography is the most reliable method used to ensure the correct placement of an advanced airway device. This non-invasive monitoring has high sensitivity and specificity with very low false-positive rates [50]. Waveform capnography is an indicator of pulmonary blood flow and guides the quality of CPR. The use of esophageal detection devices and airway ultrasound during CPR is limited due to the lack of RCT and have considered inferior to waveform

The efficacy of CPR chiefly depends upon the negative intrathoracic pressure which drives the venous return and cardiac output. Inspiratory impedance threshold device was put forward for the first time in the mid-1990s by Lurie. With the help of a pressure-sensitive unidirectional valve between the patient and the ventilation tool, it augments the negative intrathoracic pressure created during chest recoil which in turn increases venous return and hence improves cardiac output. As per 2010 guidelines by American Heart Association guidelines for CPR, it was put underclass 2b recommendation [51]. Two randomized studies have been conducted until now. In the first study, non-blinded randomized control study active compression and decompression device was used along with the ITD, the results showed a statistically significant survival benefit of 3% with this intervention [52]. In the second blinded study, ITD was used along with CPR; however, it was discontinued due to the futility of the intervention [53]. Due to these discrepancies in the outcome, ITD, when used with CPR, may offer no advantage but it may offer some survival benefit when used with a compression-decompression device. To date, no studies have been conducted on the use of ITD during in-

There is a constant emphasis on the term "high quality" used along with CPR. For a resuscitation to be successful with good neurological outcome, chest compressions need to be adequate. Clinical studies have demonstrated that the CCs quality is often poor and variable [54, 55]. These limitations lead to the invention of mechanical CPR devices, that can provide automated, high-quality CCs without any risk of fatigue. Two trials, CIRC and LINC trials, have failed to demonstrate any

Various studies have been conducted to compare the mechanical device to the manual CC so far, none of them demonstrated any significant difference between the two methods. It is suggested to use mechanical CPR devices in situations where sustained high-quality CC are not possible like where safety is at risk, conditions where fatigue may impair the delivery of high-quality CPR (Hypothermic arrest) or

in certain procedures (coronary angiography, preparation for ECPR).

never been validated in any human studies or RCT.

**5.1 Inspiratory impedance threshold device (ITD)**

**6**

Extracorporeal membrane oxygenation is also known as extracorporeal life support. It provides mechanical support to circulation as well as an extracorporeal gas exchange when the conventional resuscitation techniques fail [58]. Since its introduction in 1972, its role has been explored in various fields including cardiac arrest [59, 60]. ECMO can be a ray of hope for the patients who fail to respond to conventional CPR and helps extend the recovery period for treatable causes of cardiac arrest. It is necessary to familiarize oneself with the hemometabolic effects and limitations of ECMO to extract maximum benefit for a selected group of patients. It is expected to be more successful in IHCA and OHCA where early and effective CPR was started on time. The major challenge is gaining vascular access which can be difficult in an emergency scenario as well as time-consuming. Time is very crucial in cardiac resuscitation, ECPR time may be divided into two parts: time taken to start ECMO and time to achieve temperature management. The ideal time suggested by previous studies is between 30 and 60 min [61–63]. Successful ECPR demands coronary angiography/PCI along with temperature management. The CHEER trial covered 26 patients (11 OHCA and 15 IHCA) with refractory cardiac arrest who were given ECPR. The results were dramatic with a successful resuscitation of 92% and survival to hospital discharge was achieved in 54% cases [64].

Although evidence is limited, ECPR is recommended in cases of refractory CPR. The major limitation of this technique is a lack of resources and training to deliver ECPR.

#### **6. Pharmacological advances**

Various drugs have been used during cardiopulmonary resuscitations in OHCA and IHCA with different efficacy in terms of patients' survival, survival to discharge, and survival to neurological outcomes. Task forces have given their recommendations based on available literature with preferences given to RCTs and systemic reviews than observational studies. The pharmacological drugs used have been different in different cardiac arrest clinical situations depending on the patient profile, presence of intravenous access, and institutional protocols.

#### **6.1 Epinephrine**

International Consensus on CPR in 2015 suggested the use of epinephrine with weak recommendations considering short term benefits like ROSCs and uncertainty in long term benefits like improvement in neurological outcomes. The standard dose considered is 1 mg epinephrine. There is a weak recommendation of using high dose epinephrine (0.2 mg/kg) compared to standard-dose epinephrine (1 mg bolus). ACLS also recommend the use of intravenous epinephrine as the first choice of the drug during cardiac resuscitation. Epinephrine increases the perfusion to brain and heart by its alpha-1 mediated vasoconstriction and increases heart rate and myocardial contractility by its beta-1 mediated properties. Early administration of epinephrine is suggested in non-shockable rhythm compared to shockable VF/ pulseless VT rhythm. The appropriate timing of administration has not been suggested by international resuscitation guidelines.

#### **6.2 Vasopressin**

Use of vasopressin in place of standard-dose epinephrine has not been suggested by any task forces or resuscitation guidelines due to lack of any evidence suggesting

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no improvement in short term benefits like ROSC and admission to discharge criteria or any long term benefits in quality of life/neurological outcomes. The combination of epinephrine and vasopressin has also been non-superior to epinephrine alone in improving clinical outcomes in patients [65–67].
