Critical Care Emergencies 9CARDIOPULMONARY RESUSCITATION(ii) Pulseless electrical activity (PEA) was formerly known as
electromechanical dissociation. It is the presence of a coordinated
electrical rhythm without detectable cardiac output
(a) survival is unlikely unless a reversible cause can be found and
treated. See the ‘4 Hs’ and the ‘4 Ts’ below.
(iii) Asystole and PEA have a poor prognosis because defibrillation is
of no use
(a) continue CPR at a compression/ventilation (C/V) ratio of
30:2, unless the airway has been secured, in which case give
compressions at a rate of 100/min and ventilations at a rate of
10/min
(b) give 1 in 10 000 adrenaline (epinephrine) 1 mg (10 mL) i.v.
(c) recheck the rhythm after 2 min of CPR. If organized with a
palpable pulse, begin post-resuscitation care
(d) resume CPR immediately if asystole or PEA persist
(e) give repeated 1 in 10 000 adrenaline (epinephrine) 1 mg (10
mL) every 3–5 min, i.e. every second cycle of the algorithm
(see Fig. 1.1)
(f) continue CPR unless the rhythm changes to VF/VT. If VF is
identified midway through a 2-min cycle, complete that cycle
of CPR before shock delivery (see above p. 7).7 Potentially reversible causes: the 4 Hs and the 4 Ts.
Always look out for the following conditions, which may precipitate cardio-
respiratory arrest and/or decrease the chances of a successful resuscitation
(see Fig. 1.1).
(i) Hypoxaemia
(a) make sure maximal up to 100% oxygen is being delivered at
15 L/min
(b) confirm ventilation at 500–600 mL tidal volume (6–7 mL/kg)
is creating a visible rise and fall of both sides of the chest.
(ii) Hypovolaemia
(a) severe blood loss following trauma, gastrointestinal
haemorrhage, ruptured aortic aneurysm or ruptured ectopic
pregnancy may cause cardiac arrest
(b) always consider this in any case of unexplained
cardiovascular collapse
(c) get senior emergency department (ED) help, and search for
the source of bleeding
(d) give warmed fluid replacement and call the surgical, vascular,
or obstetrics and gynaecology team as appropriate.
(iii) Hyper/hypokalaemia, hypocalcaemia, acidaemia and other
metabolic disorders
(a) rapidly check the potassium and calcium initially as suggested
by the medical history, e.g. in renal failure (see p. 141)