Measurement of Hepatic Tissue Hypoxia Using Near Infrared Spectroscopy: Comparison with Hepatic Vein Oxygen Partial Pressure

Abstract

Hepatic hypoxia occurs during liver surgery and transplantation. The critical level associated with irreversible hepatocellular damage is unknown. Measurement of hepatic tissue oxygenation and hepatic vein oxygen partial pressure (HVPO₂) reflects oxygen supply and consumption. Near infrared spectroscopy (NIRS) can be used to monitor hepatic oxyhaemoglobin (HbO₂), deoxyhaemoglobin (Hb) and cytochrome oxidase (Cyt Ox) oxidation. This study compared regional hepatic tissue oxygenation (HbO₂, Hb and Cyt Ox) using NIRS with HVPO₂. The use of tissue oxygenation measured by NIRS and HVPO₂ as indicators of hepatic tissue hypoxia was also investigated. Large Landrace pigs (n = 5) underwent laparotomy and liver exposure. Systemic and hepatic haemodynamics were monitored continuously. NIRS probes were placed on the liver to record continuously HbO₂, Hb and Cyt Ox. Graded hypoxaemia was achieved by stepwise reduction of the fraction of inspired oxygen (FiO₂) from 30% (baseline) to 4%. A significant decrease in hepatic arterial blood flow and total hepatic blood flow was seen with severe hypoxaemia while there was no significant change to portal vein blood flow. Oxygen partial pressures in the hepatic artery, portal vein and hepatic vein decreased progressively with all grades of hypoxaemia. There was an immediate reduction of hepatic HbO₂ and simultaneous increase in hepatic Hb with all grades of hypoxaemia. Hepatic Cyt Ox was reduced significantly only with FiO₂ ≤10%. A significant correlation (p < 0.001) was found between the changes in hepatic oxygenation parameters measured by NIRS and HVPO₂. HVPO₂ measurement did not predict the reduction in intracellular tissue oxygenation demonstrated by NIRS with a decrease of Cyt Ox oxidation. In conclusion there was a good correlation between the tissue oxygenation parameters measured by NIRS and HVPO₂. However, the reduction of intracellular oxygenation found with severe hypoxaemia was demonstrated only by NIRS.

Transcutaneously measured near-infrared spectroscopic liver tissue oxygenation does not correlate with hepatic venous oxygenation in children

“…Of particular relevance to potential clinical applications were the data by ElDesoky and coworkers, who found a direct correlation between hepatic tissue hypoxia measured by liver surface NIRS in pigs and hepatic vein oxygen partial pressure during induced hypoxic hypoxemia. 11 However, in contrast to the promising animal experiments, our data show that, in children up to eight years of age, transcutaneously measured NIRS tissue oxygenation with an optode placed over the palpable liver does not correlate at all with the invasively determined SvhO 2 .…”

“…Several authors have reported on NIRS measurement of liver tissue oxygenation. [9][10][11][22][23][24][25] Most of these studies were performed in animals, with the NIRS probe attached to the liver surface after laparotomy. The investigators mainly studied relative changes of liver tissue oxygenation during naso-gastric feeding, induced hypovolemia, low cardiac output, graded hypoxia or hepatic vascular in-flow occlusion.…”

“…9,10 In animal investigations, this method allowed the monitoring of hepatic vein oxygen saturation (SvhO 2 ) as an indicator of splanchnic oxygen utilization. 11 However, data systematically assessing the validity of this assumption in children are not available.…”

Effect of graded hypoxia on the rat hepatic tissue oxygenation and energy metabolism monitored by near‐infrared and31P nuclear magnetic resonance spectroscopy

“…However, its oxygen extraction capacity approaches 100% during ischemia or hypoxia (34,35), the main mechanism for matching hepatic oxygen supply with need. There was a significant reduction of the HbT with severe hypoxia (FiO 2 ofՅ10%), which reflects the marked reduction in arterial blood flow due to the sympathetic vasoconstriction response to hypoxia (36,37).…”

Quantification of Mucosa oxygenation using three discrete spectral bands of visible light

“…Most of the work done in tissue oximtery involves near-infrared (NIR) spectra for measuring tissue oxygenation from deep tissue organs like the brain and the muscles [8][9][10]. Neverthless, few groups have investigated the potential of visible spectroscopy for a number of different clinical applications [11,12].…”