Anaesthesia and pregnant patient with respiratory problems

*Notes taken from local master student program.

Bronchial Asthma

Bronchial asthma might be expected to improve during

pregnancy due to the bronchiolar relaxing effect of progesterone.

However, it has been shown that pregnancy has no

consistent effect on the course of asthma.

Medical therapy for respiratory problems is the same as in nonpregnant women.

For labor and delivery, one should use a continuous

epidural block.

Cesarean Section. 

The possibility of drug interactions should be borne in mind when taking care of pregnant women with a history of bronchial asthma. 

Different medications that have been used are 

(1) methylxanthines, e.g., theophylline, aminophylline;

(2) b-mimetic drugs, e.g., metaproterenol, albuterol

(salbutamol), terbutaline, fenoterol, inhaled b-mimetic agonists

(the primary medications for the treatment of acute

asthma at the present time); and 

(3) corticosteroids.

Regional Anesthesia. 

Studies have suggested that although regional anesthesia has minor effects on inspiratory effort, its effect on expiratory function can be significant. 

Spinal anesthesia,

Because of its more intense motor block, can affect

abdominal muscle function as well as cough strength, thus affecting expiratory function considerably. Severe bronchoconstriction following spinal anesthesia in a parturient with severe asthma has been reported.46 The author suggested that diminished epinephrine secretion from the adrenal medulla because of sympathectomy might have triggered the bronchospasm. The author prefers epidural anesthesia over spinal anesthesia as the regional anesthetic of choice in a parturient with severe asthma. An interesting study observed less dense intercostal motor block with 0.5% bupivacaine compared

to 2% lidocaine with epinephrine (this should be true

for 0.5% ropivacaine).

General Anesthesia. 

General anesthesia should be avoided in parturients with respiratory problems if possible because the endotracheal tube can trigger severe bronchospasm. However, if it is absolutely essential, several precautions involving premedication should be taken: 

(1) H2-receptor blockers like

cimetidine and ranitidine should be avoided because the H2-receptor blockade can increase the sensitivity to histamineinduced bronchoconstriction; 

(2) a nonparticulate antacid,

0.3M sodium citrate, 30 mL, should be used routinely; and

(3)atropine and glycopyrrolate can reduce oral secretions and will also cause broncodilatation; hence some anesthesiologists will use these drugs as a premedicant. 

However, these drugs can reduce gastroesophageal sphincter tone.

Induction Agents. 

Ketamine should be the drug of choice

because it can relax the bronchial muscles through central catecholamine release. 

Succinylcholine can be used for intubation.

Of the nondepolarizing muscle relaxants, vecuronium may be safer than others.

Inhalation Agents. 

Halothane, enflurane, and isoflurane allprovide bronchodilatation. 

However, ventricular tachycardia and arrhythmias can occur if halothane is used in the presence of aminophylline or b-mimetic drugs. 

Recently sevoflurane has been suggested as an alternative to halothane and isoflurane.

Inhalation anesthetics can cause uterine muscle relaxation and predispose to obstetric hemorrhage. 

Intraoperative bronchoconstriction can be effectively treated with b-mimetic drugs administered from a metered-dose inhaler.

Extubation also needs careful attention.