Introduction

Shock is defined as a state of cellular and tissue hypoxia with either reduced oxygen delivery or poor oxygen utilisation or increased oxygen consumption with circulatory failure (collapse) and poor perfusion.

Normal aerobic metabolism is disrupted due to inadequate perfusion

Shock simply means ‘inadequate perfusion’ to maintain normal organ function.

It may be initially reversible but becomes irreversible eventually if not treated leading multiorgan failure and death.

Stages

Stage of hypoperfusion and hypoxia: Aerobic metabolism changes to anaerobic leading to lactic acidosis (metabolic acidosis).

Stage of compensatory shock: It is neuroendocrine response to maintain the perfusion of vital organs like brain, lungs and heart. Noradrenaline, renin-angiotensin and antidiuretic hormone (ADH) gets activated causing vasoconstriction of organs like gastro intestinal, kidney to divert the blood to heart, lungs and brain.

Stage of decompensatory (progressive) shock: Here compensatory mechanism fails; cell perfusion decreases causing raised intracellular sodium but low intracellular potassium. Microcirculation dysfunction can lead to the subsequent failure of the kidneys, liver, and lungs.

Stage of irreversible (refractory) shock: Here cellular ATP metabolism is lost completely leading into MOF (multiorgan failure).

Types of Shock

hypovolaemic

This type of shock results from the loss of intravascular volume, which can occur due to the loss of blood, plasma, body water, or electrolytes. It is commonly caused by conditions such as hemorrhage, vomiting, diarrhea, and dehydration.

Traumatic

This type of shock is caused by major fractures, crush injuries, burns, extensive soft tissue injuries and intra-abdominal injuries.

In this type of shock there is hypovolaemia due to bleeding both externally and internally (intraperitoneal haemorrhage) from ruptured liver or spleen or from torn vessels of the mesentery along with toxic factors resulting from fragments of tissue entering the blood stream.

Cardiogenic

This type of shock typically arises from heart-related issues, such as myocardial infarction, cardiac arrhythmias, congestive heart failure, or other heart injuries.

In this condition, the heart fails to pump blood efficiently. The left ventricle primarily fails, leading to over-distension of the right ventricle and, ultimately, increased back pressure in the pulmonary capillaries.

This results in pulmonary edema and hypoxia. Over time, the vascular volume increases due to salt and water retention by the hypoperfused kidneys.

Septic

This type of shock is most often caused by gram-negative septicemia.

Such type of shock may occur in cases of severe septicaemia, cholangitis, peritonitis or meningitis.

In the early stages, cardiac output rises while vascular resistance decreases because of dilated cutaneous arteriovenous shunts.

In late cases, vascular permeability increases, so that the blood volume decreases leading to hypovolaemia.

In more advanced cases, cardiac function becomes impaired due to toxins released by the organisms..

Anaphylactic

It is commonly seen after penicillin administration or administration of serum, dextrose, anaesthetics etc.

Such shock is usually caused by bronchospasm, laryngeal oedema and respiratory distress which totally lead to hypoxia.

This condition is worsened by massive vasodilation, leading to hypotension and ultimately shock.

It is attributed to an increased release of histamine and Slow Release Substance (SRS) of anaphylaxis, triggered by the interaction of an antigen with IgE on mast cells and basophils.

Neurogenic

This condition is caused by paraplegia, quadriplegia, spinal cord trauma, or spinal anesthesia.

Such shock is primarily due to blockade of sympathetic nervous system resulting in loss of arterial and venous tone with pooling of blood in the dilated peripheral venous system.

The heart fails to fill properly, leading to a decrease in cardiac output. Consequently, there is low blood pressure, but with a normal cardiac output, normal pulse rate, and warm, dry skin.

Common Features

Each and every type of shock has its own causes features and the treatment protocol.

features for hypovolaemic shock

The primary problem is a decrease in preload. The reduced preload leads to a decrease in stroke volume
Clinical features depend on the degree of hypovolaemia. Severe (Class III or IV) shock results in tachycardia, low blood pressures and decreased urine output.
The peripheries are cold and the patient may be confused or moribund

features of cardiogenic

The primary problem is a decrease in contractility of the heart. Reduced contractility results in a decreased stroke volume.
Left ventricular pressures rise as forward cardiac output reduces. The sympathetic nervous system is activated and consequently, systemic vascular resistance increases.
Clinically, the patient presents with tachycardia, low blood pressures and decreased urine output.
The jugular venous pulse may be raised, a S3 or S4 gallop may be present.
The lung fields may show bilateral extensive crepitations due to pulmonary oedema.
The peripheries are cold and the patient may be confused or moribund.

features of septic

These substances produce low systemic vascular resistance (peripheral vasodilatation) and ventricular dysfunction resulting in persistent hypotension.
Generalised tissue hypoperfusion may persist despite adequate fluid resuscitation and improvement in cardiac output and blood pressures. This is due to abnormalities in regional and microcirculatory blood flow. These abnormalities may lead to cellular dysfunction, lactic acidosis (anaerobic metabolism) and ultimately, multi organ failure.
Early phases of septic shock may produce evidence of volume depletion such as dry mucous membranes and cool, clammy skin.
After fluid resuscitation, the clinical picture usually aligns more with hyperdynamic shock.This includes tachycardia, bounding pulses with a widened pulse pressure, a hyperdynamic precordium on palpation and warm extremities.
Signs of possible infection include fever, localised erythema or tenderness, consolidation on chest examination,abdominal tenderness, guarding, rigidity and meningismus
Signs of end-organ hypoperfusion include tachypnoea, cyanosis, mottling of the skin, digital ischaemia, oliguria, abdominal tenderness and altered mental status.

features of anaphylactic

This occurs when a patient is exposed to an allergen to which they are sensitive, such as pollen, certain foods, food preservatives, or medications.
The anaphylactic shock that occurs in the hospital is usually due to some drug, e.g. the patient is allergic to penicillin. Latex allergy is being increasingly recognised.
The reaction can vary from mild rashes, with or without bronchospasm, to a severe anaphylactic shock. In the latter case, the patient may experience rashes, generalized edema including laryngeal edema, bronchospasm, hypotension, and, if not treated promptly, cardiac arrest.

6 Types of Shock

Table of Contents