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Anaesthesia in patient with hypertension

  • Anaesthesia management is almost similar to what has been described for IHD with following additions:-
    • Antihypertensive should be continued with morning dose to be taken with sips of water.
    • Nitroprusside is the agent of choice for the treatment of moderate to severe hypertension during surgery.

Anaesthesia for Cardiovascular Surgeries

  • Most of the cardiovascular surgeries are done under cardiopulmonary bypass, so that the heart is free of any function and surgery on heart & vessels can be done.
  • Cardiopulmonary bypass (CPR) is technique that diverts venous blood away from the heart, i.e., venous blood does not return to heart, instead it goes to CPB machine where oxygen is added and CO2 is removed.
  • Then the blood is supplied to the organs of the body.
  • CPB machine acts like lung (remove CO2 & add 0) as well as like heart (pump the blood to the organ).
  • As a result, nearly all blood flow through heart and most of the flow through lungs cease.
    Unfortunately, this process is entirely non-physiological, because arterial pressure is typically below normal and blood flow is usually nonpulsatile. Therefore, to minimize organ damage during this stressful period, Systemic hypothermia (20-32°C) is usually employed.

Anaesthesia for coronary artery bypass grafting

  • Premedication:- Anxiolytic (midazolam) and analgesic opioid (fentanyl) are frequently used.
  • Induction:- Anaesthesia most commonly used-tor induction is IV anaesthetic (propofol or etomidate) along with opioid (fentanyl, sufentanil) (AllMS May 2011).
  • Maintenance:- Maintenance is by opioid-volatile anaesthetic, i.e., combination of a volatile agent along with opioid (AllMS May 2013). Isoflurane (AllMS 10), desflurane and sevoflurane are most commonly used volatile agents. 20 and halothane should be avoided (AIIMS Nov 2010).
  • Muscle relaxants:- Vecuronium (lst choice) & Rocuronium are the most commonly used muscle relaxants.
  • Total intravenous anaesthesia (TIVA) i.e., induction as well as maintenance by i.v. anaesthetic (propofol) and rernifentanil is 2nd choice (to above described mixed intravenous/inhalational anaesthesia).
  • High dose opioid anaesthesia is not used commonly now (reason has been explained earlier).

Anaestheia For Special Situations

Anaesthesia for congenital heart diseases
  1. Cyanotic heart diseases
    • Cyanotic heart diseases have predominantly right to left shunt, i.e., blood flows directly from right side of heart to left side bypassing the pulmonary circulation. This produces cyanosis because the systemic blood coming to the right side of heart cannot be oxygenated as the blood directly flow to the left side of heart without passing through the lungs.
    • Flow through the right to left shunt depends upon the difference between systemic vascular resistance and pulmonary vescular resistance. If systemic vascular resistance is less and pulmonary vascular resistance is more, the flow through right to left shunt will be more as more pulmonary vascular resistance will resist the blood to flow from right side of heart to pulmonary circulation and blood will flow to the left side of heart through the shunt. This is further helped by less systemic vascular resistance which allow the blood to flow from the left side of heart to the aorta easily providing no resistance to right to left shunt.
    • Therefore anaesthetic drug which either decreases pulmonary vascular resistance or increase systemic vascular resistance or both will decrease the flow through shunt and improves the cyanosis.
    • Ketamine (I/M or I/V) is the anaesthetic of choice as it increases systemic vascular resistance.
    • Muscle relaxant of choice is pancuronium as it also increases systemic vascular resistance because of sympathetic stimulation and vagolytic action.
  2. Acyanotic heart diseases
    • Acyanotic heart diseases (ASD, VSD, PDA) have left to right shunt and pathophysiology opposite to cyanotic heart diseases. Therefore, Anaesthetic Which decreases systemic vascular resistance should be used. Inhalational agent (lsoflurane, sevoflurane or desflurane) decrease systemic vascular resistance, therefore are the agents of choice. Sevoflurane is the inducing agent of choice in children (AIlMS Nov 2013).

Anaesthesia for coarctation of aorta in Pregnancy

  • In coarction of aorta, aorta narrows most commonly just distal to origin ofleft subclavian artery. The common clinical presentation in coarctation of aorta is:-
    • Hypotension, ischemia, distal to obstruction (Diminished circulation in abdominal organs and pulses are absent in lower extremities).
    • Hypertension proximal to the site of obstruction (increased BP in upper extremiteis and head & neck).

Effect of coarctation of Aorta on Pregnancy

  • Coarctation of aorta may lead to compromise of placental circulation, because the placental circulation is derived from uterine artery, which is a branch of internal iliac artery (all the vessels originating distal to coarctation will have diminished perfusion). So, the fetal circulation is in a compromised state in coarctation of aorta.
  • Therefore any decrease in cardiac output or cardiac return is deleterious to the fetus because the placental circulation is already compromised on account of coarctation.
  • So any anaesthetic procedure or drug which causes hypotension should be avoided in these patients.
  • Regional anaesthetic procedures such. as spinal anaesthesia and epidural anaesthesia should be avoided in these patients because hypotension is the most common side effect of these procedures.
  • The consequence of decreased venous return and decreased systemic vascular resistance as a result of these procedures would be hazadrous to the patient.
  • General anaesthesia is the preferred technique for performing cesarian section in patient with coarctation of aorta as it has advantage of more rapid induction, less hypotension and better airway & ventilation.

Anaesthesia in mitral stenosis

  1. There are following issues which should be considered in MS surgery –
    • Heart rate:- In mitral stenosis cardiac output remains relatively fixed. Increase in heart rate decreases diastolic ventricular filling (by decreasing diastole time) and hence the stroke volume & cardiac output. Therefore the drugs which cause tachycardia should not be used. On the other hand slight decrease in heart rate is beneficial as it improves diastolic filling & stroke volume. But, it should be slight decrease not significant as cardiac output also depends on heart rate (CO = Stroke volume x heart rate). Therefore, the drug which causes slight reduction in heart rate is ideal, e.g. xenon
  2. BP:- Hypotension causes reflex tachcardia and tachycardia is not tolerable in MS. Therefore, drugs which cause decrease in systemic vascular resistance and hypotension should be avoided.
  3. Myocardial contractility :- Drugs that decrease myocardial contractility should be avoided as these drug reduce cardiac output.
  4. Pulmonary vascular resistance:- Drugs that increase pulmonary vascular resistance should be avoided as these may exacerbate pulmonary hypertension caused by mitral stenosis.
Thus, Anesthesia in MS is best accomplished by ';se of drugs with 'minimal effect OJ) heart rate, myocardial contractility, Cardiac output and systemic and pulmonary vascular resistance. Drugs used are ~
  1. Preanesthetic medication:- Small dose ofbenzodiazepine
  2. Muscle relaxant:- Rocuronium
  3. Induction:- Slow thiopentol administration or low dose narcotic (morphine/fentanyl)
  4. Maintenance:- Often a nitrous oxide/narcotic anesthetic or balanced anaesthesia that includes low concentration of a volatile anaesthetic can achieve the goal. Xenon is an ideal agent as it causes slig/tt reduction in heart rate (beneficial in MS) with no other effect on cardio-vascular system (AlIMS-IO).
    β-blockers, CCBs or digitalis are used to control heart rate.

Cerebral protection during cardiovascular surgery

  • The brain is very vulnerable to ischemic injury because of its relatively high oxygen consumption and near-total dependence on aerobic glucose metabolism. As cardiopulmonary bypass causes ischemia to brain, it should be protected from ischemic 'Injury. Methods of cerebral protection are:-

  1. Hypothermia
    1. It is the most effective method for protecting the brain during focal and global ischemia. Indeed, profound hypothermia is often used for up to 1 hr of total circulatory arrest with little evidence of neurological impairment.
    2. Hypothermia provides cerebral protection by decreasing basal and electrical metabolic requirments throughout the brain.
  2. Anaesthetic agents
    1. Amongst intravenous anaesthetic agepts, barbiturates (thiopentone), etomidate and propofol are cerebroprotective. They decrease cerebral metabolic rate, oxygen demand and ICT.
    2. Thiopentone provides greatest protection against focal ischemia amongst intravenous agents (AIHfS02).
    3. Amongst inhalational agents, isoflurane is the agent of choice because it appears to provide the greatest protection against cerebral ischemia.
    4. Anaesthetic agents are protective against focal ischemia, however no anaesthetic agent has consistently been shown to be protective against global ischemia. Only hypothermia is truely protective.
Electroencepbalographic changes during anaesthesia



• Inhalational agent (subanaesthetic)

• Barbiturates (small doses)

• Benzodiazepens (small dose)

• Etomidate (small doses)

Nitrous oxide (AlIMS May 2011)

Ketamine (AlIMS Nov 2012)

Mild hypercapnia

Sensory stimulation

Inhalational agents (1-2 MAC)






Marked hypercapnia

Hypothermia (AIIMS Nov 2013)

Hypoxia (early) (AlIMS May 2014)

Hypoxia (late) ischemia

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