Assessment of maternal cerebral blood flow velocity by transcranial Doppler ultrasound before delivery and in the early postpartum period

Middle Cerebral Artery Blood Flow Velocity During Normal Pregnancy

BACKGROUND

The present study aimed to evaluate resting middle cerebral artery (MCA) blood flow velocities using transcranial Doppler ultrasound (TCD) in healthy women at different stages of pregnancy, and to compare these velocities with those of normal controls.

METHODS

A total of 105 healthy normotensive pregnant women and 25 non-pregnant healthy controls were included in the study. We formed 3 groups according to gestational age: first trimester (7 to 13 wk pregnant), second trimester (14 to 28 wk pregnant), and third trimester (29 to 42 wk pregnant). Age, body mass index, heart rate, arterial blood pressure, and hematological data were recorded and TCD was performed on the subjects. Regarding TCD, we evaluated the mean cerebral blood flow velocity, the peak systolic velocity, the end-diastolic flow velocity, S/D ratio, the pulsatility Index (PI) and the resistance Index (RI).

RESULTS

The MCA mean blood flow velocities differed significantly among the groups ( P <0.001) and were higher in the controls than those of the first trimester, second trimester, and third trimester groups ( P <0.01, P <0.001, P <0.001 respectively). The MCA mean and peak blood flow velocities, and the PI and RI decreased significantly with advancing gestation.

CONCLUSIONS

TCD is a noninvasive and non-toxic method of monitoring the adaptation of the maternal cerebral blood flow in pregnancy. The progressive decreases in the MCA mean and peak blood flow velocities, PI, and RI during gestation may be the result of chemical and neuronal factors. This study supports the need for additional studies using TCD to establish normative cerebral blood flow volumes throughout pregnancy.

Pre- and Post-Hemodialysis Cerebral Blood Flow Velocity in Patients With End-Stage Renal Disease

BACKGROUND

This study assessed the consequences of hemodialysis (HD) on hemodynamic parameters of cerebral circulation by measuring middle cerebral artery blood flow velocities using transcranial Doppler ultrasound before and after a single dialysis session in patients with end-stage renal disease (ESRD).

MATERIALS AND METHODS

Fifty clinically stable patients with ESRD undergoing HD and 40 healthy controls were recruited for the study. Blood pressure, heart rate, and body weight were measured. Transcranial Doppler ultrasound evaluations and blood analyses were performed immediately before and after a single dialysis session.

RESULTS

The mean cerebral blood flow velocities (CBFVs) in the ESRD patients before HD was 65 ± 17 cm/second and did not differ from that of the normal controls (64 ± 14 cm/s) ( P = 0.735). The postdialysis CBFV also did not differ from that of the controls ( P = 0.054).

CONCLUSION

Compensatory cerebral autoregulation and chronic adjustment to therapy may be the reason for the nondeviation of the CBFV values from normality observed in both sessions.

Physiology of the cerebrovascular adaptation to pregnancy

The adaptation of the cerebral circulation to pregnancy is unique compared with other organs and circulatory systems, because the brain requires relatively constant blood flow and water and solute composition to maintain homeostasis. Thus, a major adaptation of the maternal cerebrovasculature to pregnancy is to maintain normalcy in the face of expanded plasma volume, increased cardiac output, and high levels of permeability factors. In this chapter, the effect of pregnancy on critical functions of the cerebral circulation is discussed, including changes occurring at the endothelium and blood-brain barrier (BBB), which protect the maternal brain from changes in BBB permeability. Further, pregnancy-induced changes in the structure and function of cerebral arteries, arterioles, and veins will be discussed as they relate to cerebral vascular resistance, hemodynamics, and cerebral blood flow autoregulation.

Deficiency in CD4 T Cells Leads to Enhanced Postpartum Internal Carotid Artery Vasoconstriction in Mice: The Role of Nitric Oxide

The risk of postpartum (PP) stroke is increased in complicated pregnancies. Deficiency in CD4 T cell subsets is associated with preeclampsia and may contribute to PP vascular disease, including internal carotid artery (ICA) stenosis and stroke. We hypothesized that CD4 T cell deficiency in pregnancy would result in ICA dysregulation, including enhanced ICA vasoconstriction. We characterized the function, mechanical behavior, and structure of ICAs from C57BL/6 (WT) and CD4 deficient (CD4KO) mice, and assessed the role of NO in the control of ICA function at pre-conception and PP. WT and CD4KO mice were housed under pathogen-free conditions, mated to same-strain males, and allowed to litter or left virgin. At 3 days or 4 weeks PP, mice were euthanized. The responses to phenylephrine (PE), high K⁺ and acetylcholine (ACh) were assessed in pressurized ICAs before and after NOS inhibition. Passive lumen diameters were measured at 3–140 mmHg. eNOS and iNOS expression as well as the presence of T cells were evaluated by immunohistochemistry. Constriction of WT ICAs to PE was not modified PP. In contrast, responses to PE were significantly increased in ICAs from PP as compared to virgin CD4KO mice. Constriction to high K⁺ was not enhanced PP. ICAs from WT and CD4KO mice were equally sensitive to ACh with a significant rightward shift of dose-response curves after L-NNA treatment. NOS inhibition enhanced PE constriction of ICAs from WT virgin and PP mice. Although a similar effect was detected in ICAs of virgin CD4KO mice, no such changes were observed in vessels from PP CD4KO mice. Passive arterial distensibility at physiological levels of pressure was not modified at PP. ICA diameters were significantly increased in PP with no change in vascular wall thickness. Comparison of eNOS expression in virgin, 3 days and 4 weeks PP revealed a reduced expression in ICA from CD4 KO vs. WT PP vessels which reached significance at 4 weeks PP. iNos expression was similar and decreased over the PP period in vessels from WT and CD4KO mice. Dysregulation of the CD4 T cell population in pregnancy may make ICA vulnerable to vasospasm due to decreased NO-dependent control of ICA constriction. This may lead to cerebral hypoperfusion and increase the risk of maternal PP stroke.

Effectiveness of nebulized dexmedetomidine for treatment of post-dural puncture headache in parturients undergoing elective cesarean section under spinal anesthesia: a randomized controlled study

PURPOSE

The need for effective treatment for post-dural puncture headache (PDPH) is a growing research entity. This study aimed to test the effectiveness of additional dexmedetomidine (DEX) to PDPH conservative management and evaluate its cerebral hemodynamic effects trans-cranial Doppler.

METHODS

This prospective randomized double-blind controlled trial was conducted on 43 post-partum females suffering from PDPH with visual analog score (VAS) ≥ 4 and Lybecker score ≥ 2. The study subjects were allocated into control group [n = 22] received nebulization of 4 mL 0.9% saline and DEX group [n = 21] received nebulization of 1 µg/kg DEX diluted in 4 mL 0.9% saline twice daily that was continued until achieving VAS score ≤ 3 and Lybecker score < 2 and/or for a maximum of 72 h. Both groups received routine conservative management. The primary outcome was the VAS and Lybecker scores and the secondary results were the DEX effects on cerebral vessels and the occurrence of any adverse effects.

RESULTS

VAS and Lybecker scores were significantly lower in DEX group. The middle cerebral artery mean flow velocity was significantly lower, and the pulsatility index was considerably higher after DEX nebulization compared to placebo. Two patients in the control group were indicated for epidural blood patch.

CONCLUSION

The addition of DEX nebulization (1 µg/kg twice daily) to the PDPH conservative care effectively relieved the symptoms and lowered pain scores which could be due to its analgesic and cerebral vasoconstrictive effects.

TRIAL REGISTRATION

This study was approved by the research ethical committee of Faculty of Medicine, Zagazig University with the reference number (ZU-IRB#: 6075/26-4-2020) and it was registered under clinicaltrials.gov (NCT04327726).

Cerebral Blood Flow Regulation in Pregnancy, Hypertension, and Hypertensive Disorders of Pregnancy

The regulation of cerebral blood flow (CBF) allows for the metabolic demands of the brain to be met and for normal brain function including cognition (learning and memory). Regulation of CBF ensures relatively constant blood flow to the brain despite changes in systemic blood pressure, protecting the fragile micro-vessels from damage. CBF regulation is altered in pregnancy and is further altered by hypertension and hypertensive disorders of pregnancy including preeclampsia. The mechanisms contributing to changes in CBF in normal pregnancy, hypertension, and preeclampsia have not been fully elucidated. This review summarizes what is known about changes in CBF regulation during pregnancy, hypertension, and preeclampsia.

Transcranial Doppler role in prediction of post-dural puncture headache in parturients undergoing elective cesarean section: prospective observational study

PURPOSE

Post-dural puncture headache (PDPH) may be resulted from significant changes in cerebral blood flow, which could be visualized by Transcranial Doppler (TCD). This study was performed to investigate if TCD can be used to predict the occurrence of PDPH in high-risk patients.

METHODS

This prospective observational study was conducted on ninety ASA I and II pregnant females undergoing elective cesarean section (CS) under spinal anesthesia. TCD was performed to all patients within 24 h before the operation, at 24 h and 48 h in the post-operative period to measure mean velocity (MV) and Gosling pulsatility index (PI) in the right middle cerebral artery. For 5 days postoperatively, all patients were assessed and the PDPH patients were identified, their pre- and post-puncture TCD measurements were compared with the corresponding measurements of PDPH-free patients and ROC analysis was done to evaluate the predictive value of TCD parameters.

RESULTS

17 patients (18.8%) developed PDPH. PDPH group was significantly higher regarding MV and significantly lower with regard to PI at all times except for the pre-spinal PI. The MV values in all patients showed statistical significant increase within the first 48 h after CS as compared with those before delivery. In PDPH group there was high statistical significant decrease in PI values at 24 h and 48 h compared to the pre-puncture values. The pre-puncture MV was the parameter of the best accuracy for predicting PDPH with a cutoff of MV > 68.4 cm/s and the post-puncture PI at 24 h was the best predictive of PDPH with a cutoff value of < 0.75.

CONCLUSION

TCD might prove a useful tool in predicting PDPH suggesting that higher pre-puncture MV with a cutoff value > 68.4 cm/s and post-puncture lower PI at 24 h with a cutoff < 0.75 are the best predictive parameters.

TRIAL REGISTRATION

This clinical trial was registered with ClinicalTrials.gov (NCT03464253).