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Shock
• -Shock is a complex syndrome involving a
reduction in blood flow to the tissues that may
result in irreversible organ damage and
progressive collapse of the circulatory system.
• -If left untreated it will result in death. Shock can
be acute but prompt treatment results in
recovery, with little detrimental effect on the
mother-However, inadequate treatment or failure
to initiate effective treatment can result in a
chronic condition ending in multisystem organ
failure, which may be fatal.
Shock can be classified as
follows:
• hypovolaemic – the result of a reduction in
intravascular volume such as in severe
obstetric haemorrhage
• • cardiogenic – impaired ability of the
heart to pump blood. In midwifery it may
be seen following a pulmonary embolism
or in women with cardiac defects.
• • neurogenic – results from an insult to
the nervous system as in uterine inversion
• • septic or toxic – occurs with a severe
generalized infection.
• • anaphylactic – may occur as the result
of a severe allergy or drug reaction.
• -This section deals with the principles of
hypovolaemic shock and septic shock,
either of which may develop as a
consequence of childbirth.
Hypovolaemic shock
• This is caused by any loss of circulating fluid
volume, as in haemorrhage, but may also occur
when there is severe vomiting. The body reacts
to the loss of circulating fluid in stages as
follows:
• Initial stage
• -The reduction in fluid or blood decreases the
venous return to the heart.
• -The ventricles of the heart are inadequately
filled, causing a reduction in stroke volume and
cardiac output.
• -As cardiac output and venous return fall,
the blood pressure is reduced.
• -The drop in blood pressure decreases the
supply of oxygen to the tissues and cell
function is affected.
Compensatory stage
• -The drop in cardiac output produces a response
from the sympathetic nervous system through
the activation of receptors in the aorta and
carotid arteries.
• - Blood is redistributed to the vital organs.
• - Vessels in the gastrointestinal tract, kidneys,
skin and lungs constrict.
• -This response is seen by the skin becoming
pale and cool. Peristalsis slows, urinary output is
reduced and exchange of gas in the lungs is
impaired as blood flow diminishes.
• -The heart rate increases in an attempt to
improve cardiac output and blood
pressure.
• -The pupils of the eyes dilate.
• - The sweat glands are stimulated and the
skin becomes moist and clammy.
• -Adrenaline (epinephrine) is released from
the adrenal medulla and aldosterone from
the adrenal cortex.
• - Antidiuretic hormone (ADH) is secreted
from the posterior lobe of the pituitary.
• -Their combined effect is to cause
vasoconstriction, increased cardiac output
and a decrease in urinary output.
• -Venous return to the heart will increase
but, unless the fluid loss is replaced, will
not be sustained.
Progressive stage
• -This stage leads to multisystem failure.
• - Compensatory mechanisms begin to fail, with
vital organs lacking adequate perfusion.
• -Volume depletion causes a further fall in blood
pressure and cardiac output.
• - The coronary arteries suffer lack of supply.
Peripheral circulation is poor, with weak or
absent pulses. Final, irreversible stage of shock
• -Multisystem failure and cell destruction are
irreparable. Death ensues.
Effect of shock on organs and
systems
• -The human body is able to compensate for loss of up to
10% of blood volume, principally by vasoconstriction.
• -When that loss reaches 20–25%, however, the
compensatory mechanisms begin to decline and fail.
• - In pregnancy the plasma volume increases, as does
the red cell mass.
• - The increase is not proportionate, but allows a healthy
pregnant woman to sustain significant blood loss at birth
as the plasma volume is reduced with little disturbance
to normal haemodynamics
• - In a woman who has not had a healthy
increase in plasma volume, or has
sustained an antepartum haemorrhage, a
much lower blood loss is required to have
a pathological effect on the body and its
systems. Individual organs are affected as
below.
Brain
• -The level of consciousness deteriorates
as cerebral blood flow is compromised.
• -The mother will become increasingly
unresponsive.
• -She may not respond to verbal stimuli
and there is a gradual reduction in the
response elicited from painful stimulation.
Lungs
• -Gas exchange is impaired as the physiological dead
space increases within the lungs.
• - Levels of carbon dioxide rise and arterial oxygen levels
fall.
• - Ischaemia within the lungs alters the production of
surfactant and, as a result of this, the alveoli collapse.
• - Oedema in the lungs, due to increased permeability,
exacerbates the existing problem of diffusion of oxygen.
- Atelectasis, oedema and reduced compliance impair
ventilation and gaseous exchange, leading ultimately to
respiratory failure.
• This is known as adult respiratory distress syndrome
(ARDS).
Kidneys
• -The renal tubules become ischaemic,
owing to the reduction in blood supply.
• -As the kidneys fail, urine output falls to
less than 20 mL/hr.
• -The body does not excrete waste
products such as urea and creatinine, so
levels of these in the blood rise
Gastrointestinal tract
• -The gut becomes ischaemic and its ability to
function as a barrier against infection wanes.
• -Gram-negative bacteria are able to enter the
circulation.
• Liver
• -Drug and hormone metabolism ceases, as does
the conjugation of bilirubin.
• -Unconjugated bilirubin builds up and jaundice
develops
• -Protection from infection is further
reduced as the liver fails to act as a filter.
• - Metabolism of waste products does not
occur, so there is a build-up of lactic acid
and ammonia in the blood.
• - Death of hepatic cells releases liver
enzymes into the circulation.