EFFECT OF DIFFERENT NOREPINPHRINE APPLICATION METHODS IN CAESARIANES ON HYPOTENSION AFTER SPINAL ANESTHESIA

EFFECT OF DIFFERENT NOREPINPHRINE APPLICATION METHODS IN CAESARIANES ON HYPOTENSION AFTER SPINAL ANESTHESIA INTRODUCTION Spinal anesthesia in cesarean sections is a frequently used anesthesia technique today. The most common complication associated with spinal anesthesia is hypotension. Systemic vascular resistance and cardiac output decrease due to sympathetic blockade, and when this is accompanied by bradycardia and contractility, hypotension develops(1,2,3).

Maternal hypotension is a condition that can cause negative consequences such as nausea, vomiting, and dizziness in pregnant women who undergo spinal anesthesia. In addition, it increases the likelihood of fetal acidosis, hypoxia, and neonatal neurological damage. Therefore, it is necessary to treat maternal hypotension effectively. In the current treatment of maternal hypotension, intravenous fluid administration, treatments such as ephedrine, phenylephrine, and norepinephrine are used (4,5,7). Among these drugs, ephedrine is the first preferred vasopressor (4). For this reason, its efficacy and safety, and the use of different doses have been extensively studied (5,7). Ephedrine is a vasopressor with both direct and indirect effects in the treatment of hypotension due to neuraxial block in obstetrics with its alpha and beta agonist effects. The most important disadvantage of ephedrine is that it has a slow onset and weak effect, difficulty in titration, development of tachyphylaxis, causing maternal tachy-arrhythmias and fetal acidosis (9). Ephedrine easily crosses the placenta and causes fetal tachycardia, an increase in noradrenaline concentration in the umbilical artery (UA), and a decrease in pH and base excess (BE). An increase in fetal metabolic rate, an increase in fetal O2 consumption and CO2 production, and an increase in lactate level are observed through beta-adrenergic stimulation (9). Phenylephrine, on the other hand, is a pure alpha-agonist agent that is more potent (phenylephrine/ephedrine: 80:1), easy to titrate, effectively treats hypotension and nausea-vomiting, has minimal placental transfer, and does not cause fetal acidosis and changes (10-11). However, the disadvantage of phenylephrine is that it decreases maternal heart rate and cardiac output (12). Another vasopressor drug used in the treatment of hypotension in recent years is norepinephrine. Norepinephrine is both an α-receptor agonist and a weak β-receptor agonist (7,8). Theoretically, it lowers heart rate and cardiac output less.

There are previous studies in which norepinephrine was administered only as a prophylactic or only infusion to prevent hypotension after spinal anesthesia in cesarean sections. However, there are not enough studies reporting which of these application methods are more effective. Therefore, in our study, cesarean section under spinal anesthesia was planned; We aimed to investigate the effectiveness of norepinephrine differential administration methods on preventing maternal hypotension.

WORKING PROTOCOL After the approval of the faculty ethics committee, the written and verbal consent of the patients will be obtained, and a double-blind randomized study will be initiated.

Pregnant women over the age of 18, with ASA (American Society of Anesthesiologists physical status) ≤ III, body weight 50-100 kg and height 150-180 cm, with a single pregnancy planned for cesarean section under elective conditions under spinal anesthesia, will be included in the study.