Monitoring Microcirculatory Blood Flow with a New Sublingual Tonometer in a Porcine Model of Hemorrhagic Shock

Abstract

Tissue capnometry may be suitable for the indirect evaluation of regional hypoperfusion. We tested the performance of a new sublingual capillary tonometer in experimental hemorrhage. Thirty-six anesthetized, ventilated mini pigs were divided into sham-operated (n = 9) and shock groups (n = 27). Hemorrhagic shock was induced by reducing mean arterial pressure (MAP) to 40 mmHg for 60 min, after which fluid resuscitation started aiming to increase MAP to 75% of the baseline value (60–180 min). Sublingual carbon-dioxide partial pressure was measured by tonometry, using a specially coiled silicone rubber tube. Mucosal red blood cell velocity (RBCV) and capillary perfusion rate (CPR) were assessed by orthogonal polarization spectral (OPS) imaging. In the 60 min shock phase a significant drop in cardiac index was accompanied by reduction in sublingual RBCV and CPR and significant increase in the sublingual mucosal-to-arterial PCO2 gap (PSLCO2 gap), which significantly improved during the 120 min resuscitation phase. There was significant correlation between PSLCO2 gap and sublingual RBCV (r = −0.65, p < 0.0001), CPR (r = −0.64, p < 0.0001), central venous oxygen saturation (r = −0.50, p < 0.0001), and central venous-to-arterial PCO2 difference (r = 0.62, p < 0.0001). This new sublingual tonometer may be an appropriate tool for the indirect evaluation of circulatory changes in shock.

Methane Exhalation Can Monitor the Microcirculatory Changes of the Intestinal Mucosa in a Large Animal Model of Hemorrhage and Fluid Resuscitation

“…The microcirculation of the sublingual area is frequently investigated, as it is considered a suitable GI region for non-invasive approaches, assuming that the changes might indicate the condition of the microcirculation in more distal sections, such as the ileum. Indeed, earlier studies demonstrated that tissue carbon dioxide pressure in the sublingual area is tied to changes in the small intestinal microcirculation in a hemorrhagic shock and fluid resuscitation model (22). In the present study, we could not detect a correlation between the sublingual microcirculation and the serosal or mucosal components of ileal microperfusion in the resuscitation phase, and this finding highlights the difference between the two methods.…”

Recent Advances Of Mucosal Capnometry And The Perspectives Of Gastrointestinal Monitoring In The Critically Ill. A Pilot Study

“…Similar findings have been reported, using sublingual capnometric monitoring during bleeding, in both human and animal studies [6,7]. The results of a haemorrhagic shock model in pigs, when complex hemodynamic and blood gas measurements were performed in addition to sublingual capnometry and orthogonal polarisation spectral imaging (OPS) during severe bleeding, were recently detailed [8]. The results suggest that, sublingual to arterial PCO 2 gap values, correlated well with microcirculatory parameters gained by videomicroscopy, and the combination of capnometric monitoring with arterial and central venous blood gas parameters may improve the diagnostic accuracy of haemodynamically relevant haemorrhage or other types of hypoperfusion.…”

Impairment of Mesenteric Perfusion as a Marker of Major Bleeding in Trauma Patients

“…The measurement of the partial pressure of carbon dioxide (pCO 2 ) in tissues is a potentially feasible method for the indirect evaluation of microcirculation [109,110]. Tonometry utilizes the principle that at equilibrium the partial pressure of a diffusible gas such as CO 2 is equal in the mucosa and in the lumen of a viscus.…”

“…The difference between pCO 2 in the sublingual mucosa and arterial pCO 2 is considered to be predictive of mortality in acute circulatory failure, especially with a cutoff level of 70 mmHg [112,125]. Moreover, the sublingual area is easier to access and free of some limitations of gastric tonometry, such as potential interference of gastric acid [110,126]. The benefits of sublingual capnometry for the management of critically ill or severely injured patients were studied for decades with promising results [12,125,[127][128][129][130][131]; however, its clinical use did not become widespread [112].…”