Management of Circulation in Emergency – By Dr. Gnana Sankaralingam
Major function of circulatory system is to supply blood containing oxygen and nutrients to the brain and other parts of the body. Circulatory system consists of the heart which pumps blood into arteries which provide blood through capillaries to the tissues. Veins bring the blood back to the heart and after oxygenation by lungs, it is returned to the heart for recirculation. There should be an adequate volume of blood in the system and the blood pressure has to be maintained for circulation to be efficient. Inadequacy of volume or pressure or both, results in ciculatory collapse or shock. This is manifested as low blood pressure (hypotension), rapid thready pulse and extremities turning cold, pale and sweaty. When interruption to the circulatory function takes place, the entire body becomes compromised. Damage to brain occurs in three minutes if oxygen is deprived and little longer when sugar is deprived. Thus maintaining circulation by proper functioning of the heart is vital.
Total volume of blood circulating in the body is six litres, and heart pumps 5 litres each minute. One could lose upto 750 cc of blood without any changes to the system. If loss exceeds that, first to increase is the pulse rate due to heart pumping faster to maintain the supply. Further loss will cause blood pressure to drop, which the body counters by constricting the peripheral blood vessels. This causes the classic picture of a circulatory collapse. Assessment of patient presenting with shock includes examining the peripheries, feeling the pulse and recording the blood pressure. Shock could be calssified into hypovolaemic (loss of blood or fluids), septic (toxins or infections), neurogenic due to severe pain or cardiogenic following heart attack. Causes of large amount of blood loss are major trauma, post-partum haemorrhage (bleeding from womb after delivery), haematemesis (vomiting of blood) and haemoptysis (coughing out blood). Causes of large amount of fluid loss are burns, acute pancreatitis, diabetic keto acidosis and cholera. Since all these conditions need rapid replacement of large amounts of fluids or blood to counter the loss, intravenous access should be established using two large gauge peripheral lines in the upper limbs. Fluid administration is done and monitored by pulse and blood pressure records. Central lines are avoided initially due to complications.
Commonest cause of circulatory collapse is hypovolaemia due to a loss of blood or body fluids. In the case of traumas, external bleeding should be controlled by direct pressure. If limbs are involved and direct pressure is not successful, elevation of limb followed by application proximally of blood pressure cuff inflated above systolic blood pressure may be used temporarily. Blood loss must be replaced by blood. In the case of fluid loss, more than 10% in adults and 5% in children need to be replaced by intravenous fluids. Dehydration following fluid loss is classified into as minor (< 10% loss presenting with thirst, oral dryness and passing reduced amounts of concentrated urine), moderate (10% to 20% loss presenting with above features plus muscle weakness, sunken eyes and loss of skin turgour) and severe (>20% loss presenting in addition to other two categories with alteration in level of consciousness (drowsiness, confusion or coma), air hunger (acidotic breathing) and state of shock. Fluids infused are normal saline (0.9% sodium cloride), saline with 5% dextrose added and Hartmans (Ringer-Lactate) solution which has similar concentration of electrolytes as blood plasma.
Next common cause of circulatory collapse is cardiogenic shock which is usually caused by irregular heart beat (arrythmia) or pump failure. For proper circuation, heart should not only beat with adequate force but also maintain correct rate and rhythm. Heart needs time to refill in between contractions and if the heart rate is fast (tachycardia), time is not adequate for refilling which result in pumping out less blood. If heart rate is slow (bradycardia), though refilling is adequate, due to the slow pace of contraction, blood reaching the tissues is less. It is the same for irregular heart rhythms. When there is pump failure there is accumulation of fluid in lungs when left ventricle is affected and in parts of the body when right ventricle is affected. Initial treatment is to give supplemental oxygen to increase oxygen content of existing circulation and fluid challenge of 250ml of crystalloid (normal saline) to restore fluid volume (pre-load) and optimise cardiac output. Assessment after 15 minutes for response to fluid challenge is done and if the systolic blood pressure rises by 10%, continue fluid challenge. If not, titrate fluid to optimise circulating blood volume and consider augmenting cardiac output and elevating blood pressure. To maintain adequate perfusion, start with vasopressors such as nor-adrenaline to modulate systemic vascular resistance and if the patient has signs of poor heart output or hypoperfusion, an inotopic agent such as dobutamine which increases myocardial activity is added. If there is evidence of fluid retention diuretic such as frusemide is administered.
Other causes of circulatory collapse seen are septic (widespread infection), anaphylactic (severe allergic reaction) and spinal injury. Septic shock is commonly caused by staphylococcus and gram negative bacteria presenting with severe hypotension despite adequate fluid resuscitation and is treated with combination of broad spectrum antibiotics. It could lead to multiple organ failure and death. Anaphlactic shock is potentially fatal needing immediate administration of 1:1000 adrenaline (ingredient of Epipen given to severe allergy sufferers), followed by administration of anti-histamine and steroid. Spinal shock should be thought of in accidents involving spine, where hypotension does not correspond to amount of blood loss. Unlike other shocks, patients often present with normal or slightly faster pulse, systolic BP in the range of 70 to 90 mm and have warmer extremities.
Methods are used to monitor parameters of circulation such as pulse, pressure (arterial and venous) and heart activity (rate and rhythm). Indirect and intermittent measure of pressure and pulse are considered inadequate in unstable patients. Cuffs placed around upper arms or thighs and inflated at regular intervals are used to record pulse and pressure. Arterial pressure monitoring using a transducer system connected through a fluid filled tubing to a canula placed in an artery usually in the wrist is continuous and more acurate recording. Measurement of central venous pressure (blood within intra-thoracic part of superior or inferior vena cava) is done using an externally placed device with patient in supine position (lying flat). In this, a catheter is passed through a vein usually in neck to the vein in the chest, and the fluid within the catheter transmits pressure to the device. This gives an idea of fluid balance and becomes very useful when large amounts of fluid have to be transfused. ECG monitor is attached to the patient using electrodes to record heart beat continuously.
Devices used in emergency for ciculatory support include intra-aortic balloon pump and external pacemaker. In balloon pump, catheter with a balloon at the tip is inserted through artery in the groin into aorta in the chest and balloon is inflated with carbon dioxide or helium during diastole and rapidly deflated during systole. It improves blood flow into coronary arteries by increasing intra aortic pressure and increase cardiac output by reducing left ventricular pressure load. It is used as a temporary measure till prosthetic ventricles for long term is considered. External pacing is indicated for heart rate below 40 beats responding poorly to atropine IV, third degree heart block and in some with second degree heart block. Adhesive electrodes are placed on the chest, either both in front or one in front and other at back and connected to a pulse generator which senses the irregularity and takes appropriate action to correct it. It is a temporary measure till a permanent pacemaker is fitted. Defibrillators and cardioverters are also used in emergency to restart the heart in cardiac arrest and correct those heart rhythm abnormalities that do not respond to pharmacological agents.
