Influence of norepinephrine and phenylephrine on frontal lobe oxygenation during cardiopulmonary bypass in patients with diabetes.

OBJECTIVE: Although utilization of vasopressors recently has been associated with reduced cerebral oxygenation, the influence of vasopressors on cerebral oxygenation during cardiopulmonary bypass in patients with diabetes is unknown. The aim of this study was to document the impact of norepinephrine and phenylephrine utilization on cerebral oxygenation in patients with and without diabetes during cardiopulmonary bypass. DESIGN: Prospective, clinical study. SETTING: Academic medical center. PARTICIPANTS: Fourteen patients with diabetes and 17 patients without diabetes undergoing cardiac surgery. INTERVENTIONS: During cardiopulmonary bypass, norepinephrine (diabetics n = 6; non-diabetics n = 8) or phenylephrine (diabetics n = 8; non-diabetics n = 9) was administered intravenously to maintain mean arterial pressure above 60 mmHg. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure, venous temperature, arterial oxygenation, and frontal lobe oxygenation (monitored by near-infrared spectroscopy) were recorded before anesthesia induction (baseline) and continuously during cardiopulmonary bypass. Frontal lobe oxygenation was lowered to a greater extent in diabetics versus non-diabetics with administration of norepinephrine (-14±13 v 3±12%; p<0.05). There was also a trend towards a greater reduction in cerebral oxygenation in diabetics versus non-diabetics with administration of phenylephrine (-12±8 v -6±7%; p = 0.1) during cardiopulmonary bypass. CONCLUSIONS: Administration of norepinephrine to restore mean arterial pressure during cardiopulmonary bypass is associated with a reduction in frontal lobe oxygenation in diabetics but not in patients without diabetes. Administration of phenylephrine also were associated with a trend towards a greater reduction in frontal lobe oxygenation in diabetics. The clinical implications of these findings deserve future consideration.

Impact of visceral obesity on cardiac parasympathetic activity in type 2 diabetics after coronary artery bypass graft surgery.

OBJECTIVE: The association between adiposity and heart rate variability (HRV) in patients with type 2 diabetes (T2D) after coronary artery bypass graft surgery (CABG) is not well documented. We evaluated the associations between indices of adiposity and HRV in patients with T2D with CABG and quantified the relationships of the volume of visceral (VVAT) and subcutaneous adipose tissue (VSAT) to HRV. DESIGN AND METHODS: One hundred and thirty-five men with T2D who underwent CABG participated in this study. HRV, BMI, waist circumference (WC), VVAT, and VSAT were measured. Correlations between indices of HRV and adiposity were evaluated and predictors of HRV modulation were identified. Patients were then divided into quartiles of VVAT and VSAT to further evaluate the influence of adiposity on HRV. RESULTS: Subjects were 65 ± 7 years old (mean ± SD) with a BMI of 30 ± 4 kg/m(2) and a WC of 105 ± 10 cm. BMI (r = -0.19) and WC (r = -0.25) were inversely correlated with low frequencies. VVAT correlated negatively with SD normal-to normal (SDNN) (r = -0.22, P < 0.01), indices of cardiac parasympathetic activity [rMSSD (r = -0.27), NN50 (r = -0.22), pNN50 (r = -0.26; all P < 0.05], and with low (r = -0.37) and high frequencies (r = -0.20; all P < 0.01). Patients with the lowest VVAT had the highest cardiac parasympathetic activity (P < 0.05). VVAT remained the best predictor of cardiac parasympathetic activity after adjustments for confounding parameters (P < 0.01). CONCLUSION: An increase in visceral adiposity, not BMI, seems to be associated with lower HRV in patients with T2D who had a CABG procedure.

Nitric oxide modulates peristaltic muscle activity associated with fluid circulation in the sea pansy Renilla koellikeri.

Nitric oxide (NO) is a well-known regulator of vascular activities in vertebrates and it has also been implicated as a vasodilatatory agent in a cephalopod. In the sea pansy Renilla koellikeri, an octocorallian representative of the most basal animals with a nervous system, we investigated the role of NO in peristalsis, an activity that moves body fluids through the coelenteron (gastrovascular cavity) of the polyps across the colony. NO donors increased the amplitude of peristaltic contractions and increased tonic contractions in relaxed preparations, but caused a relaxation of basal tension in contracted preparations. The NO synthase (NOS) inhibitors L-NAME (N(omega)-nitro-L-arginine methyl ester) and 7-nitroindazole reduced the amplitude of peristaltic contractions and lowered basal tension. In contrast, aminoguanidine, a specific inhibitor of inducible NOS, increased the amplitude but reduced the rate of peristalsis. Zaprinast, a cGMP-specific phosphodiesterase inhibitor, decreased the amplitude of peristaltic contractions, a decrease that was amplified by dibutyryl cGMP. In contrast, the inhibitor of soluble guanylyl cyclase ODQ (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one) enhanced peristalsis. Putative NOS-containing neurons, revealed by NADPH-diaphorase activity and citrulline immunohistochemistry, were observed in the basiectoderm at the base of the autozooid polyp tentacles and in a nerve-net around the oral disc. Their neurites ran up the tentacles and down to the polyp body wall, crossing from the ectoderm through the mesoglea and into the endoderm musculature where musculo-epithelial cells were also reactive. These data suggest that two distinct nitrergic pathways, one of which is mediated by cGMP, regulate peristalsis and muscle tone in the sea pansy and that these pathways may involve NOS-containing ectodermal neurons and musculo-epithelial cells.