Pregnant women in the first trimester may be exposed to many surgical procedures which cannot be postponed after delivery. Anesthesia selected in such patients may be regional or general anesthesia. Anesthetic precautions must be taken as, the teratogenic effects of some drugs as nitrous oxide, the tocolytic effects of some drugs, and prevention of preterm labor.

Adequate perfusion and oxygenation of the small gestational sac is essential in this stage of pregnancy [1,2]. The introduction of ultrasonography has greatly improved the early diagnosis of threatened abortion, with the advent of Three –Dimensional (3D) ultrasonography; it became possible to perform reliable sonographic volume calculations [3]. More recently, sub endometrial blood flow was quantitatively analyzed by using the color histogram mode in (3D) [4].

The aim of this study: To compare general anesthesia (isofluranefentanyl), and spinal anesthesia when used in the first trimester and there effects on sub-trophoblastic blood flow using the three dimensional transabdominal power Doppler ultrasonographic imaging.

The study included 20 pregnant women scheduled, in Kasr El - Aini Hospitals for surgical operation under general anesthesia, as appendectomy, cerculge, breast mass removal or breast biopsy. The Study design was prospective, cross-sectional, comparative study.

After a written consents, pregnant female divided in 2 groups each one included 10 women, all studied pregnant women of the 2 groups were subjected to full history taking and full clinical examination.

Inclusion criteria: Age less than 35 years, unremarkable medical history, up to 12 weeks pregnancy, no history of vaginal bleeding, or uterine contractions.

Exclusion criteria were, uterine pathology as myomas or malformation, pregnancy induced hypertension, gestational diabetes, or missed abortion.

Anesthetic technique, in group 1: After premedication with midazolam 0.05 mg/kg, 500 ringer infusion was started in all patients. ECG, pulse oximetry, capnography monitors were used. After cricoids pressure rapid sequence induction using 2-3 mg /kg sodium thiopental followed by 0.6 mg/kg rocuronium, after intubation ventilation was started with rate 10 per minute, and tidal volume 8-10 ml/kg to maintain end tidal CO₂ 30-35mmHg. Anesthesia was maintained in group I by 1% isoflurane.

In group 2: Spinal anesthesia was used, after positioning of the patient in the sitting position, sterilization, proper manual localization of the site of injection of 3 ml of lidocaine 2% was injected as infiltration anesthesia. 20 gauge spinal needle punctured the ligamentumflavum, when CSF came out injection of 2-4 ml of heavy bupivacaine was done, followed by assessment of the level of anesthesia. Ephedrine 20-30 mg diluted on 10 ml saline was given with increment when hypotension occurred. Trans-abdominal three dimensional power Doppler ultrasonographic measurement of sub-trophoblastic blood flow using the flow index was done for all studied women in the 2 groups as follows; when the retrochorioninic area (localized just beneath the chorionfrondom) was obtained, the Power Doppler mode was activated using Toshiba Doppler eccocee ssq-340a. Subsequently, this region was defined by a movable sector on the screen. Identical power Doppler settings (color gain, 44.8; pulse repetition frequency1,9; and color power 3) were used in all patients. The 3D- volume mode switched on; quantitative analysis of the blood flow in the outlined area was achieved by implementing the color histogram, the result of which was displayed as indices. The visualization (V1) characterizes vessel density. The flow index (F1) reflects intensity of blood flow; and the vascularization flow index (VF1) specifies both vascularization and perfusion. The indices were calculated by the built –in computer.

V1=color values (total voxel-back ground); F1=weighted color values/color value and; VF1=weighted color values (total voxels-back ground value).

Statistical analysis: Data was presented as mean (SD) and range (median), Mann Whitney test was used, SPSS version 15 (p ≤ 0.05 considered significant).

Table 1 showed that there was no significant difference in maternal gestational age and the parity in both groups.

Table 1: Maternal, gestational age, and parity of both groups.

Table 2 showed Sub-trophoblastic blood flow index before after anesthesia. Sub-trophoblastic blood flow index in general anesthesia group is significantly higher than in spinal anesthesia group.

Table 2: Sub-trophoblastic blood flow index before and after anesthesia.

In the first trimester, there is 20% of pregnant women subjected to threatened abortion and miscarriage. Surgical procedures in the first trimester expose the pregnant women to anesthesia, the effect of general or spinal anesthesia on sub-trophoblastic blood flow is important as prognostic factor during the first trimester [5]. Maintenance of subtrophoblastic blood flow is the hallmark for early gestational sac wellbeing. Uterine blood flow is determined by the equation:

Uterine arterial pressure – uterine venous pressure

Uterine vascular resistance: Any factor which will significantly decrease mean maternal arterial pressure or significantly increase uterine vascular resistance will decrease sub-trophoblastic blood flow and, ultimately, umbilical blood flow. At term, 10% of the maternal cardiac output (700 mL/min) supplies the uterus [6]. Factors which decrease trophoblastic blood flow are: Uterine Contraction decreased uterine blood flow, anesthetic drugs as intravenous induction agents, inhalation agents, isoflurane and sevoflurane, local anesthetics, pharmacological agent added to the local anesthetic, vasopressors, antihypertensive agents-adrenergic blocking drugs, tocolytic drugs, epidural and subarachnoid opiates [7].

The aim of this prospective study is to compare the quantitative effects of general anesthesia (isoflurane-fentanyl) or spinal anesthesia on sub trophoblastic blood flow by the non invasive three dimensional ultrasonography. The present study found that the sub-trophoblastic blood flow was significantly high in patient received general anesthesia than those received spinal anesthesia. The sub-trophoblastic blood flow index may be lower in the spinal anesthesia group due to lower vascular resistance that decreases the maternal blood pressure and uterine blood flow. Vasopressors as ephedrine when given for hypotension followed spinal anesthesia may increase the uterine vascular resistance and decrease the sub-trophoblastic blood flow index. Sub-trophoblastic blood flow index is an accurate quantitative method that can be used very early in the first trimester. Several studies [8,9] had evaluated the utroplacental circulation in patients using Doppler waveform analysis, and measuring the systolic diastolic ratio(S/D) from the wave form, this method is qualitative method compared to the recent abdominal three dimensional ultrasonography. The 3 – dimensional color Doppler was useful in achievement of correct display of vascular network architecture in 3 orthogonal planes, other advantages of transabdominal three –dimensional ultrasonography are the absence of trans vaginal infection with the usage of the transvaginal two dimensional ultrasonography [10,11].

This study concluded that the sub-trophoblastic blood flow was decreased in spinal anesthesia more than general anesthesia in the first trimester operations. The use of transabdominal three-dimensional power Doppler ultrasonographic imaging of the sub-trophoblastic blood flow may be helpful for evaluation of the effects of different anesthetics on sub-trophoblastic blood flow. This study also depend on the accuracy of abdominal three dimensional power Doppler ultrasonographic quantitative measurement of blood flow compared to the qualitative waveform analysis obtained by two dimensional transvaginal color Doppler ultrasound, the abdominal route also decreases the risk of ascending infection.