Maternal microcirculation and sidestream dark field imaging: a prospective assessment of the association between labour pain and analgesia on the microcirculation of pregnant women

Possible Impact of Spinal Anesthesia and Phenylephrine on Sublingual Microcirculation of Cesarean Delivery Patients

Background

This study was a proof of concept of a novel means to evaluate microcirculatory changes during spinal anesthesia for cesarean delivery. It sought to examine the distributive circulatory effects of spinal anesthesia and evaluate the impact of phenylephrine administration on the microcirculation of these women.

Methods

After Research Ethics Board approval, healthy, non-laboring pregnant women with singleton, term pregnancies scheduled for elective cesarean delivery were recruited. Participants were randomly assigned to receive either phenylephrine infusion or phenylephrine bolus. Spinal anesthesia was standardized. A sidestream dark-field (SDF) MicroScan^® video microscope was applied to the sublingual mucosa to obtain microcirculation videos in five different visual fields. Videos were made before and after spinal anesthesia. The resultant videos were analyzed randomly and blindly. The mean microvascular flow index (MFI) values were compared before and after spinal anesthesia. The difference in MFI following spinal anesthesia was compared between phenylephrine infusion and bolus groups.

Results

Thirty-two patients were recruited for the study; 22 patients had complete video sets for analysis. Baseline characteristics were similar between the two groups, including preoperative hemodynamics. There were no significant differences between pre- and post-spinal MFI. The post-spinal MFI within the infusion group (mean ± standard deviation: 2.74 ± 0.21) was not significantly different from the bolus group (2.56 ± 0.42, P = 0.22).

Conclusion

Despite theoretical physiological implications of spinal anesthesia and phenylephrine on the microcirculation, significant alteration of the MFI was not observed between pre- and post-spinal anesthesia (within group). Additionally, despite an eight-fold larger phenylephrine dose for continuous infusion prophylaxis used in this group of women, this did not result in a significant alteration of the microcirculation compared to those who received phenylephrine treatment for hypotension (between groups).

The microcirculatory failure could not weaken the increase of systematic oxygen extraction rate in septic shock: An observational study in canine models

OBJECT

This study aimed at exploring what level of the microcirculation alteration could weaken the decrease of ScvO2 (or the increase of O2ER) and further result in an abnormally elevated ScvO2.

METHODS

Beagles were randomly assigned into control (n = 5) and shock group (n = 5). The canines in shock group were intravenously injected with live E. coli (3.5×108 cfu/kg), and the ones in control group were injected with sterile saline. The experiment continued to the animals' death or for a maximum of 24 hours. Hemodynamic parameters, blood gas and inflammatory cytokines level were collected. Microcirculatory parameters were assessed with Sidestream Dark Field (SDF) imaging. The correlation between the microcirculation and oxygen metabolism or inflammatory cytokine, meanwhile the correlation between the oxygen metabolism and inflammatory cytokine was assessed.

RESULTS

E. coli infusion induced hypodynamic shock. The correlation between microcirculation and oxygen metabolism or inflammatory cytokine, and The correlation between the oxygen metabolism and inflammatory cytokine (O2ER vs. MFI: r = -0.700, P < 0.01; O2ER vs. PVD: r = -0.677, P < 0.01; O2ER vs. PPV: r = -0.538, P < 0.01; MFI vs. IL-6: r = -0.780, P < 0.01; PPV vs. IL-6: r = -0.621, P < 0.01; MFI vs. TNF-α: r = -0.636, P < 0.01; PPV vs. TNF-α: r = -0.561, P < 0.01) were observed.

CONCLUSIONS

The increase of O2ER cannot be weakened by the microcirculatory failure.