Cerebral haemodynamics in early puerperium: A prospective study

Abstract

Aim: Prospective study on 900 consecutive puerperae to assess normal values and range of the blood flow velocity in the middle cerebral artery in both hemispheres.

Material and method: M1 and M2 segments of both middle cerebral arteries were assessed in all subjects within 96 hours of delivery. Mean flow velocity was recorded after adjusting for insonation angle. Lindegaard index (LI = middle cerebral artery-Internal Carotid Artery mean flow velocity ratio) was calculated whenever the mean flow velocity exceeded 100 cm/second. Asymmetry indexes were calculated inter hemispherically for M1 and M2 segments separately.

Results: Mean flow velocities were 74 ± 17 and 72 ± 17 in right and 73 ± 17 and 72 ± 17 cm/second in the left M1 and M2, respectively. A total of 136 subjects (12.1%) exceeded the threshold of 100 cm/second, but LI was consistently <3 in all of them. Mean flow velocity was inversely and independently correlated to haemoglobin levels and to parity. Mean asymmetry indexes were 0.25 ± 23 in M1 and 0.45 ± 25 in M2.

Conclusion: Mean flow velocity in the middle cerebral artery of healthy subjects in early puerperium is higher than in age-matched non-puerperal women and may exceed the threshold of 100 cm/second with no evidence of intracranial spasm, because of blood loss during delivery. Mean flow velocity is independently correlated with parity. Right-to-left mean flow velocity asymmetry may reach 50% as a consequence of a transient imbalance in vascular tone regulation.

Keywords: Mean flow velocity; asymmetry index; middle cerebral artery; puerperium.

Figure 1.

Upper panel: MR angiography, axial view. Proximal and distal segments of MCA marked as M1 and M2, respectively. ACA: anterior cerebral artery; SIPHON: carotid siphon; MCA: middle cerebral artery. Lower panel: Transcranial colour coded sonography, axial view. M1 and M2 segments of MCA insonated at a depth of 55–65 mm and 45–55 mm, respectively, from the skull wall (marked by the white curved line). The carotid siphon is not visible as it courses orthogonal to the scanning plane.

Figure 2.

Transcranial colour coded sonography: axial view. The sample volume is placed in the proximal segment of MCA. The spectral display of velocity is shown in the lower panel. Horizontal axis = time. Vertical axis velocity in cm/second. PSV: peak systolic velocity; EDV: end diastolic velocity; MFV: mean flow velocity; PI: pulsatility index.

Figure 3.

Distribution of velocities in the right (upper panel) and left (lower panel) proximal (M1) and distal (M2) segments of middle cerebral artery. The black line depicts the normal distribution. Horizontal axis: velocity in cm/second. Vertical axis: frequency as number of subjects.

Figure 4.

Distribution of asymmetry indexes in proximal (M1) and distal (M2) segments of MCA. The black line depicts the normal distribution. Horizontal axis: non-dimensional index of asymmetry as calculated according to Zanette’s formula: positive cases denote higher velocity in the right side MCA, negative cases denote higher velocity in the left side MCA. Vertical axis: frequency as number of subjects.