Figure 6.2 illustrates the various clinical signs seen in ongoing acute blood loss suffered by a pregnant woman related to the volume lost. The point where the pulse rate is a higher number than the systolic blood pressure is a sign of significant decompensation.
Table 6.1 Severity of blood loss during maternal haemorrhage
| Class | Loss of circulating volume (%) | Blood loss in a 70 kg pregnant woman (ml) | Signs and symptoms |
|---|---|---|---|
| I | 0–15 | <1000 | Fully compensated due to blood diversion from the splanchnic pool. No symptoms. Minimal tachycardia is likely to be the only abnormal sign. No treatment needed in an otherwise healthy woman as long as the bleeding has stopped |
| II | 15–30 | 1000–2000 | Peripheral vasoconstriction maintains systolic blood pressure. The woman may be aware of increased heart rate and may display agitation or aggression. Narrowed pulse pressure and tachypnoea are the keys to early detection, as heart rate is only modestly increased and systolic blood pressure remains normal. Peripheral vasoconstriction maintains blood pressure. Requires crystalloid fluid replacement |
| III | 30–40 | 2000–2700 | Cardiovascular system shows signs of decompensation. The woman will look unwell. Tachycardia, tachypnoea, changes in mental status, fall in systolic blood pressure. Will require crystalloid and potential blood transfusion |
| IV | >40 | >2700 | Immediately life threatening. Tachycardia, fall in blood pressure, altered mental status, evidence of negligible urine output. Loss of >50% results in loss of consciousness, requiring immediate ‐surgery as well as massive transfusion |
Figure 6.2 Clinical parameters following increasing blood loss in the pregnant and postpartum woman
Pitfalls in the recognition of shock in pregnancy
Some pregnant women do not mount a tachycardia, or can even produce a bradycardia. This can be paradoxical, due to vagal stimulation [see above] or if the woman is taking beta‐blocker medication
Women with pacemakers have a fixed upper heart rate
Athletes may have a very slow baseline heart rate
Haemoglobin concentration is a useful measure of blood loss, only after there has been fluid resuscitation
During the acute phases of loss, the haemoglobin concentration will not change. Rapid movement of fluid from the extracellular to the intravascular compartment and intravenous clear fluids, will result in a fall in haematocrit. A falling haematocrit may be the only indicator of a slow steady bleed. A rapidly falling haematocrit associated with early signs of hypovolaemia is suggestive of severe loss.
6.5 Principles of treatment
Hypovolaemic shock
Primary survey and resuscitation should be carried out according to the ABC principles. See Chapter 10 for the management of A and B.
C: Circulation
A diagnosis of hypovolaemic shock must be promptly followed by:
Restoration of adequate oxygen delivery to the tissues by restoration of adequate circulating volume and adequate oxygen carrying capacity (see Chapter 8 for intravenous fluids)
Stopping the bleeding (see Chapter 28 for major obstetric haemorrhage)
Consider haemorrhage to be of two types:
Compressible
Non‐compressible
Compressible haemorrhage is controllable by direct pressure, limb elevation, packing, by reduction and immobilisation of fractures or, in obstetric situations, compression of the uterus.
Non‐compressible haemorrhage occurs in a body cavity (chest, abdomen, pelvis or retroperitoneum). See Chapters 17, 18 and 21 for haemorrhage in trauma.
Septic shock
Septic shock complicating delivery may be caused by infection from the genital tract, but can occur with any source of infection, for example a urinary tract or chest infection.
The development of shock is due to a dysregulated systemic inflammatory and immune response to microbial invasion that results in vasodilatation, hypotension and organ dysfunction. Septic patients have a metabolic acidosis with a raised lactate, detectable on sampling of arterial or venous blood.
In trauma patients, sepsis is unlikely to cause shock at presentation. It is most likely to develop later in patients with penetrating abdominal injuries and in whom the peritoneal cavity has been contaminated by intestinal contents.
The key to management is a high degree of suspicion, rapid diagnosis and urgent treatment, as perinatal sepsis is a rapidly progressive disease. Pregnant women with septic shock will require early referral to critical care. See Chapter 7 for further information on maternal septic shock.
Cardiogenic shock
Cardiogenic shock in pregnancy is a life‐threatening condition due to failure of the ventricles to produce an adequate cardiac output. Ischaemic heart disease, valvular heart disease, arrhythmia, cardiomyopathy and pulmonary and amniotic fluid embolism are the main causes of cardiogenic shock in pregnancy.
In trauma, patients can develop cardiogenic shock due to penetrating injury, cardiac tamponade, tension pneumothorax and myocardial contusion.
There is a significant overlap in the signs and symptoms between these forms of shock and hypovolaemic shock. One distinguishing feature is the extreme air hunger and orthopnoea seen in patients suffering cardiogenic shock. Listening to the chest may give clues of congestion due to increased pressure in the pulmonary circulation causing pulmonary oedema.
Cardiogenic shock has a high mortality and mandates multidisciplinary consultant management with involvement from cardiology, cardiac surgery and critical care. Transfer to a centre able to offer complex invasive cardiac support may be required.