CTRI

The Caesarean section, a crucial procedure in obstetrics, is the best way to successfully deliver a foetus in a number of circumstances. ¹ In order to get the best results and give the expectant mother a safe and comfortable labouring experience, a team approach is essential. It’s critical to identify the anaesthesia type that has minimal negative effects on mother and foetus.

The type of anaesthesia chosen for LSCS is dependent on many factors such as the urgency, the reason why LSCS is being performed, preference of the parturient as well as coexisting medical problems. There are numerous reasons to use general anaesthesia including life-threatening foetal compromise, unsuccessful regional anaesthesia, contraindication to local anaesthesia, when the regional anaesthesia might not have enough time to be used, maternal request. ²

Previously, general anaesthesia was considered to be the technique of choice, but now, the number of LSCS done under general anaesthesia have significantly reduced. ³ Securing an airway is more difficult in a pregnant female than in the general population due to physiological and anatomical changes occurring during pregnancy. ⁴ The obstetric airway may be affected by anatomical changes such as oedema in the upper airway, breast enlargement, and increase in weight. ⁴ A study done on parturient, shows that there is a link between a decreased length of neck, obesity, a receding mandible, and prominent maxillary incisors that makes intubation harder. ⁵ Aspiration of the gastric contents is also one of the major concerns.

Throughout the past two decades, Lower Segment Caesarean Section is being done under regional anaesthesia, this way the problem of securing a difficult airway during general anaesthesia is being avoided. ² Complimentary to the choice of anaesthesia, the development of comparatively safer choices of local anaesthetics, such as Ropivacaine and Levobupivacaine have further cemented the safety of Regional Anaesthesia as the choice of anaesthesia.

Although historically general anaesthesia has been utilised when there is a threat to the mother or the foetus, while neuraxial methods are recommended in less urgent situations, due to its relative simplicity and quicker onset of effect, in cases of urgent caesarean sections, spinal anaesthesia is advocated. It involves injecting local anaesthetics into the subarachnoid space with a spinal needle. This subarachnoid block is primarily administered between the L3 and L4 and L5 subarachnoid spaces.

Postpartum haemorrhage (PPH) is one of the leading causes of maternal mortality with uterine atony being the cause in about 50% cases. ⁷ By using uterotonic drugs properly, it can be decreased. The most often utilised uterotonic substance is oxytocin. The risk of PPH can be decreased by up to 40% by regularly utilising oxytocin as a prophylactic measure. ⁸

Yet, because oxytocin acts on oxytocin receptors found in the heart and major vessels, it has the unfavourable effect of causing hypotension and reflex tachycardia.⁹ To treat this hypotension, various vasopressors such as Ephedrine, Mephentermine and Phenylephrine are used. Among this, Phenylephrine has displayed a faster and better control of blood pressure (BP) during spinal anaesthesiaâ€‘induced hypotension. ¹⁰

Phenylephrine an alpha agonist with a short duration of action that can be administered as a bolus or as an infusion at titrated dosages to treat oxytocin-induced hypotension.¹¹

Phenylephrine co-administration has been found to reduce the effects of oxytocin on cardiac output, heart rate and systemic vascular resistance. ¹² At higher doses Phenylephrine can cause reflex bradycardia along with decreased cardiac output. ¹³

There are very few studies which have discussed a minimum dose with a better efficacy of phenylephrine, used during co-administration with oxytocin to reduce the hemodynamic changes of oxytocin

Therefore current study will be done to compare two different doses of phenylephrine which are required to prevent adverse cardiovascular changes due to oxytocin in females undergoing LSCS under spinal anaesthesia.