· Intro: definition, problem, cause, priorities, ALS shockable algorithm
· Non-drug treatment
· Drug treatment
|
Definition |
· Chaotic ventricular depolarisation and repolarization |
|
Problem |
· No cardiac output · LOC in seconds · Eeath in minutes |
|
Causes |
· Hypotension, hypoxia, hypothermia, electrolyte disturbance · AMI, PE, tamponade, tension pneumothorax, drug/toxin |
|
Priorities |
· Early unbroken CPR (↑survival) · Early defibrillation (↑survival) · Treat causes in order of ease and likelihood |
|
ALS algorithm: shockable |
· CPR 2 mins -> rhythm check -> defibrillation (repeat) · Adrenaline 1mg: after 2nd loop, then every 2nd loop · Amiodarone 300mg: after 3 x defib |
|
Praecordial thump |
· Heel of hand -> sternum · Only if witnessed, monitored VF arrest and no ready access to defib · Mechanism of action (MoA): mechanical energy -> electrical energy (2-5J) -> mild depolarisation -> silence -> sinus rhythm · Side effects (SEs): sternal or rib fracture, myocardial contusion |
|
Defibrillation |
· Electric shock of heart between two gel pads or paddles · Device: 5kV step up transformer + capacitors in charging circuit; inductor in discharging circuit; switch between · Shock has specific magnitude and duration · 200J biphasic better than 360J monophasic o ↔/↑ effectiveness o ↓ energy -> ↓ electrical injury · MoA: depolarize whole myocardium -> silence -> sinus rhythm · SEs: skin burns, internal burns, electrocution of staff, fire/explosion |
|
Non-drug measures |
More helpful for non-shockable · IV fluid (restore blood volume, preload) · Pericardiocentesis for tamponade (restore preload) · Needle decompression of tension pneumothorax (restore preload) |
|
Adrenaline |
· Dose: 1mg · Catecholamine · At high dose α1 > β1 > β2 effect · MoA: peripheral vasoconstriction++ -> o ↑coronary perfusion pressure -> ↑defib success o ↑cerebral perfusion pressure -> ↑survival · SEs: (observed after ROSC) o ↑↑HR o ↑↑mAP · N.B. new evidence suggests adrenaline may not improve outcome |
|
Amiodarone |
· Dose: 300mg slow push · First line for refractory VF · MoA: o Class 3 > 1,2,4 antiarrhythmic o Mainly K+ channel block o Complex MoA o Stabilizes myocyte membrane -> terminate tachyarrhythmias · SEs (after ROSC) o CVS: ↓HR, ↓mAP, ↑QTc -> ↑risk of TdP o Displace highly plasma protein bound drugs -> ↑free [drug] (e.g. warfarin) o Tissue toxicity: pulmonary fibrosis, cirrhosis, hypothyroidism |
|
Lignocaine |
· Dose: 1mg/kg · Second line for refractory VF · MoA: class 1b Na+ channel blockade o Minimal ↓slope phase 0 o ↓Absolute refractory period · SE: o Cardiac: AV block, ↓ inotropy, arrhythmias o CNS: excitation (tinnitus, perioral tingling, seizure) |
|
Vasopressin |
· Dose: 40 IU once only · Alternative to adrenaline if already running · MoA: bind V1 -> peripheral vasoconstriction o ↑Cororonary perfusion pressure -> facilitate successful defib o ↑Cerebral perfusion pressure -> preserve neuronal integrity |
|
Magnesium |
· Dose: 5mmol IV slow push · Use if VF follows torsades de pointes or in the setting of hypomagnesaemia · MoA: increases membrane stability, competes for calcium · SE: vasodilatation, sedation, muscle weakness, resp failure |
|
Potassium |
· Dose: 5mmol · Indication: hypokalaemia · MoA: restore resting potential |
|
Calcium |
· 10mmol as CaCl2 · Use if: ↑[K+], ↓[Ca2+] · MoA: MSA if ↑[K+], ↑inotropy · SE: excitotoxicity of brain and heart; vascular irritation (gluconate safe peripherally) |
|
Bicarbonate |
· 1mmol/kg · Use if: metabolic acidosis, prolonged arrest · MoA: buffer · SE: worsen ICF acidosis, ↑Na+, ↑osmolality |
|
Other |
· Thrombolytics · Glucose · Specific antidotes e.g. naloxone, flumazenil |
Feedback welcome at ketaminenightmares@gmail.com