Prolonged observation time reveals temporal fluctuations in the sublingual microcirculation in pigs given arginine vasopressin

Intravital videomicroscopy of sublingual microcirculation is used to monitor critically ill patients. Existing guidelines suggest averaging handheld video recordings of ∼20 s in duration from five areas. We assessed whether an extended observation time may provide additional information on the microcirculation. Pigs (n = 8) under general anesthesia were divided between two groups, one with manually held camera, in which microcirculation was assessed continuously for 1 min in five areas, and one with a fixed camera, in which the observation time was extended to 10 min in a single area. The microcirculation was challenged by infusing arginine vasopressin (AVP). In the fixed group, ischemic acute heart failure was induced by left coronary microembolization, and the AVP infusion was repeated. All recordings were divided into 20-s sequences, and the small-vessel microvascular flow index (MFI) was scored and averaged for each measurement point. When administering 0.003, 0.006, and 0.012 IU·kg(-1)·min(-1) of AVP, we observed that the small-vessel MFI in the fixed 10-min group was significantly reduced (2.03 ± 0.38, 0.98 ± 0.18, and 0.48 ± 0.11) compared with both the initial 20 s (2.77 ± 0.04, 2.06 ± 0.04, and 1.74 ± 0.06; P < 0.05) and the 1-min total (2.63 ± 0.09, 1.70 ± 0.07, and 1.33 ± 0.16; P < 0.05) in the handheld group. In acute heart failure, the cardiac output decreased to half of the preischemic values. Interestingly, the small-vessel MFI was more affected by the administration of 0.001 and 0.003 IU·kg(-1)·min(-1) of AVP in acute heart failure (1.62 ± 0.60 and 1.16 ± 0.38) compared with preischemic values (2.86 ± 0.09 and 2.03 ± 0.38; P < 0.05). In conclusion, a prolonged recording time reveals temporal heterogeneity that may impact the assessment of microcirculatory function.