Shock

Seminar: Approach to

Shock

Abdul Waris Khan4th Year (Medicine)

Definition• Shock is the term used to describe acute

circulatory failure with inadequate or inappropriately distributed tissue perfusion resulting in generalized cellular hypoxia and/or an in ability of the cells to utilize oxygen.

Causes of shock

Abnormalities of tissue perfusion may result from:

failure of the heart to act as an effective pump mechanical impediments to forward flow loss of circulatory volume abnormalities of the peripheral circulation.

CLINICAL FEATURES OF

SHOCK

Hypovolaemic shock

Inadequate tissue perfusion:(a) Skin – cold, pale, slate-grey, slow capillary refill, ‘clammy’(b) Kidneys – oliguria, anuria(c) Brain – drowsiness, confusion and irritability.

Increased sympathetic tone:(a) Tachycardia, narrowed pulse pressure, ‘weak’ or ‘thready’ pulse(b) Sweating(c) Blood pressure – may be maintained initially (despite up to a 25% reduction in circulating volume if the patient is young and fit), but later hypotension supervenes. Metabolic acidosis – compensatory tachypnoea.

Cardiogenic shock

• Signs of myocardial failure, e.g.• Raised jugular venous pressure (JVP)• Pulsus alternans, • ‘Gallop’ rhythm,• Basal crackles, • Pulmonary oedema.

Obstructive shock

• Elevated JVP.• Pulsus paradoxus and muffled heart sounds in

cardiac tamponade.• Signs of pulmonary embolism

Anaphylactic shock

Signs of profound vasodilatation:(a) Warm peripheries(b) Low blood pressure(c) Tachycardia.■ Erythema, urticaria, pallor, cyanosis.■ Bronchospasm, rhinitis.■ Oedema of the face, pharynx and larynx.■ Hypovolaemia due to capillary leak.■ Nausea, vomiting, abdominal cramps, diarrhoea.

• Sepsis, severe sepsis and septic shock

■ Pyrexia and rigors, or hypothermia (unusual).■ Nausea, vomiting.■ Vasodilatation, warm peripheries.■ Bounding pulse.■ Rapid capillary refill.■ Hypotension (septic shock).■ Occasionally signs of cutaneous vasoconstriction.■ Other signs:(a) Jaundice(b) Coma, stupor(c) Bleeding due to coagulopathy (e.g. from vascular puncture sites, GI tract and surgical wounds)(d) Rash and meningism(c) Hyper-, and in more severe cases hypoglycaemia

Assessment of tissue perfusion

■ Pale, cold skin, delayed capillary refill and the absence ofvisible veins in the hands and feet indicate poorperfusion. ■ Metabolic acidosis with raised lactate concentration may suggest that tissue perfusion is sufficiently compromised to cause cellular hypoxia and anaerobic glycolysis. dysfunction.■ Urinary flow is a sensitive indicator of renal perfusionand haemodynamic performance

References• Kumar & Clark’s Clinical Medicine 7th edition