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Microvascular oxygen pressure in the pig intestine during haemorrhagic shock and resuscitation
M Sinaasappel1, M van Iterson, C Ince
1Departments of Anaesthesiology, Academic Medical Centre, University of Amsterdam, The Netherlands.
Abstract:
1. The aim of this study was to investigate the relation between microvascular and venous oxygen pressures during haemorrhagic shock and resuscitation in the pig intestine. To this end microvascular PO2 (microPO2) was measured by quenching of Pd-porphyrin phosphorescence by oxygen and validated for the intestines. In addition, mesenteric venous blood gasses, blood flow, ilial CO2 production and global haemodynamics were also measured. 2. In one group (n = 11), moderate shock was induced by withdrawal of 40% of the circulating blood volume. Seven of these animals were resuscitated with a crystalloid solution and four with the withdrawn blood. In a second group of three animals, a more severe shock was induced by withdrawal of 50% of the circulating blood volume; these animals were not resuscitated. 3. Baseline mesenteric venous PO2 and microPO2 values were similar (60 +/- 9 and 60 +/- 11 mmHg, respectively). During moderate shock, microPO2 dropped significantly below mesenteric venous PO2 (26 +/- 10 versus 35 +/- 8 mmHg). After resuscitation with crystalloid solution, microPO2 and mesenteric venous PO2 rose to 44 +/- 9 and 44 +/- 6 mmHg, respectively. In the group that received the withdrawn blood, values were 41 +/- 9 and 53 +/- 12 mmHg, respectively. Severe shock resulted in a drop in the mesenteric venous PO2 (n = 3) to a value similar to that seen in the moderate shock group, but the gut microPO2 dropped to a much lower value than that of the moderate shock group (15 +/- 5 versus 26 +/- 10 mmHg). 4. The results indicate that the oxygenation of the microcirculation of the gut can become lower than the venous PO2 under conditions of haemorrhagic shock.
Insights
During hemorrhagic shock, gut microvascular oxygen pressure drops below venous oxygen pressure. Resuscitation partially restores these pressures, but severe shock causes a profound decrease in microvascular oxygen levels.
Area of Science:
- Physiology
- Hemorrhagic Shock Research
- Intestinal Microcirculation
Background:
- Hemorrhagic shock significantly impacts tissue oxygenation.
- Understanding microvascular responses is crucial for effective resuscitation strategies.
Purpose of the Study:
- To investigate the relationship between microvascular and venous oxygen pressures in the pig intestine during hemorrhagic shock and resuscitation.
- To assess the impact of different resuscitation methods on intestinal oxygenation.
Main Methods:
- Measurement of microvascular PO2 (microPO2) using Pd-porphyrin phosphorescence quenching.
- Monitoring of mesenteric venous blood gases, blood flow, CO2 production, and global hemodynamics.
- Induction of moderate (40% blood withdrawal) and severe (50% blood withdrawal) hemorrhagic shock in pigs, with varying resuscitation protocols.
Main Results:
- Baseline microPO2 and mesenteric venous PO2 were similar (approx. 60 mmHg).
- During moderate shock, microPO2 significantly decreased below venous PO2 (26 vs 35 mmHg).
- Severe shock led to a more pronounced drop in microPO2 (15 mmHg) compared to venous PO2.
Conclusions:
- Gut microcirculation oxygenation can fall below venous oxygen levels during hemorrhagic shock.
- Resuscitation partially restores oxygen pressures, but severe shock indicates critical microvascular compromise.
- Findings highlight the importance of monitoring microvascular oxygenation for assessing shock severity and resuscitation efficacy.