Anesthesia – General and Spinal
Anesthesia can be general or spinal. General anesthesia is the induction of a balanced state of unconsciousness, which is accompanied by the absence of pain sensation and paralysis of skeletal muscle over the entire body. It is induced through the administration of anesthetic drugs either intravenously or by inhalation. It is usually used during major surgery and other invasive surgical procedures. Along with this, there is also amnesia and weakening of autonomic responses. Spinal anesthesia is induction of anesthesia by administering drugs into the spinal canal. Anesthesia is to be administered only by qualified medical professionals and a proper medical history as well as clinical examination and investigations form an important part of the pre-anesthetic checkup. Irrespective of this, certain adverse effects can occur due to anesthetic drugs and bradycardia is one of them.
Causes of Bradycardia During Anesthesia Induction
Bradycardia is reduction of the heart rate below 60 beats per minute. It is a fairly common adverse effect as many anesthetic agents stimulate the parasympathetic system which decreases the heart rate.
Bradycardia can occur during all phases of anesthesia like induction, maintenance and postoperative phase but most commonly it occurs during the maintenance phase.
The various causes of bradycardia during anesthesia are:
1.Anesthetic drugs, including the following:
b. Intravenous analgesic opioids like remifentanil, alfentanil and fentanyl
2. Any drug given by the surgeon should also be considered.
3. Hypoventilation and hypoxia during anesthesia induction as well as laryngospasm and aspiration can also cause bradycardia.
4. Stimulation of vagal reflexes.
5. Surgical factors like inferior vena cava compression or pneumoperitoneum.
6. Undetected blood loss.
7. Cardiac events like hemothorax or pneumothorax.
Management of Bradycardia
Bradycardia is considered as an emergency as due to insufficient heart rate, cardiac output decreases and hence this leads to compromise in oxygen delivery to the tissues.
Management of bradycardia during anesthesia comprises of two steps:
A. Emergency management
1. Adequate ventilation and oxygenation is provided if there is any compromise in the airway.
2. The anesthetic drug is discontinued if it is known to be the cause of bradycardia.
3. Intravenous atropine is given to increase the heart rate.
4. If necessary, intravenous adrenaline is given.
B. Further care
1. If necessary, an adrenaline infusion is continued.
2. An external pacemaker is considered.
3. Urgent cardiology consultation if the situation warrants.
Associated Complications of Bradycardia
The following complications can occur along with bradycardia:
1. Hypotension – decrease of blood pressure
2. Cardiac arrest
To conclude, bradycardia during anesthesia induction is to be considered as an emergency and should be dealt with promptly. Regular close monitoring should be done till the patient is completely out of the effects of anesthesia and the heart rate returns to normal.
1. Complications in Anaesthesia, 2007 by John L Atlee.
2. Textbook of Anaesthesia, 2007 by Alan R Aitkenhead, Graham Smith, David J Rowbotham.