Increased Tissue Oxygen Tension Research Articles

Anesthesia, Microcirculation, and Wound Repair in Aging

Age-related changes in skin contribute to impaired wound healing after surgical procedures. Changes in skin with age include decline in thickness and composition, a decrease in the number of most cell types, and diminished microcirculation. The microcirculation provides tissue perfusion, fluid homeostasis, and delivery of oxygen and other nutrients. It also controls temperature and the inflammatory response. Surgical incisions cause further disruption of the microvasculature of aged skin. Perioperative management can be modified to minimize insults to aged tissues. Judicious use of fluids, maintenance of normal body temperature, pain control, and increased tissue oxygen tension are examples of adjustable variables that support the microcirculation. Anesthetic agents influence the microcirculation of a combination of effects on cardiac output, arterial pressure, and local microvascular changes. The authors examined the role of anesthetic management in optimizing the microcirculation and potentially improving postoperative wound repair in older persons.

Anesthesia, Microcirculation, and Wound Repair in Aging

Age-related changes in skin contribute to impaired wound healing after surgical procedures. Changes in skin with age include decline in thickness and composition, a decrease in the number of most cell types, and diminished microcirculation. The microcirculation provides tissue perfusion, fluid homeostasis, and delivery of oxygen and other nutrients. It also controls temperature and the inflammatory response. Surgical incisions cause further disruption of the microvasculature of aged skin. Perioperative management can be modified to minimize insults to aged tissues. Judicious use of fluids, maintenance of normal body temperature, pain control, and increased tissue oxygen tension are examples of adjustable variables that support the microcirculation. Anesthetic agents influence the microcirculation of a combination of effects on cardiac output, arterial pressure, and local microvascular changes. The authors examined the role of anesthetic management in optimizing the microcirculation and potentially improving postoperative wound repair in older persons.

THE EFFECT OF ADVANCE HYPOXIC TRAINING UPON TISSUE OXYGEN TENSION IN THE TUMOR DURING AQUTE HYPOXIA OF DIFFERENT TYPES

The tumors of rats who had not been acclimated to hypoxia subjected to acute hypoxic hypoxia (altitude chamber) as well as blood hypoxia (carbon monoxide) decreased tissue oxygen tension while histotoxic hypoxia (NaCN) on the contrary increased tissue oxygen tension. The tumor acclimated to hypoxia seems to select compensatory mechanisms mostly associated with increased tissue oxygen tension thus taking advantage of lower extent of tissue oxygen tension when subject to acute hypoxic hypoxia than in femoral muscle. All types of acute hypoxias caused a decrease of tissue oxygen tension in the malignancy.

Supplemental Oxygen, but Not Supplemental Crystalloid Fluid, Increases Tissue Oxygen Tension in Healthy and Anastomotic Colon in Pigs

Low tissue oxygen tension is an important factor leading to the development of wound dehiscence and anastomotic leakage after colon surgery. We tested whether supplemental fluid and supplemental oxygen can increase tissue oxygen tension in healthy and injured, perianastomotic, and anastomotic colon in an acutely instrumented pig model of anastomosis surgery. Sixteen Swiss Landrace pigs were anesthetized (isoflurane 0.8%-1%) and their lungs ventilated. The animals were randomly assigned to low fluid treatment ("low" group, 3 mL x kg(-1) x h(-1) lactated Ringer's solution) or high fluid treatment ("high" group, 10 mL/kg bolus, 18 mL x kg(-1) x h(-1) lactated Ringer's solution) during colon anastomosis surgery and a subsequent measurement period (4 h). Two-and-half hours after surgery, tissue oxygen tension was recorded for 30 min during ventilation with 30% oxygen. Three hours after surgery, the animals' lungs were ventilated with 100% oxygen for 60 min. Tissue oxygen tension was recorded in the last 30 min. Tissue oxygen tension was measured with polarographic Clark-type electrodes, positioned in healthy colonic wall, close (2 cm) to the anastomosis, and in the anastomosis. In every group, tissue oxygen tension during ventilation with 100% oxygen was approximately twice as high as during ventilation with 30% oxygen, a statistically significant result. High or low volume crystalloid fluid treatment had no effect on colon tissue oxygen tension. Supplemental oxygen, but not supplemental crystalloid fluid, increased tissue oxygen tension in healthy, perianastomotic, and anastomotic colon tissue.

Mild Hypercapnia Increases Subcutaneous and Colonic Oxygen Tension in Patients Given 80% Inspired Oxygen during Abdominal Surgery

Supplemental perioperative oxygen increases tissue oxygen tension and decreases incidence of wound infection in colorectal surgery patients. Mild intraoperative hypercapnia also increases subcutaneous tissue oxygen tension. However, the effect of hypercapnia in patients already receiving supplemental oxygen is unknown, as is the effect of mild hypercapnia on intestinal oxygenation in humans-although the intestines are presumably the tissue of interest for colon surgeries. The authors tested the hypothesis that mild intraoperative hypercapnia increases both subcutaneous tissue and intramural intestinal oxygen tension in patients given supplemental oxygen. Patients undergoing elective colon resection were randomly assigned to normocapnia (n = 15, end-tidal carbon dioxide tension 35 mmHg) or mild hypercapnia (n = 15, end-tidal carbon dioxide tension 50 mmHg). Intraoperative inspired oxygen concentration was 80%. The authors measured subcutaneous tissue oxygen tension in the right upper arm and intramural oxygen tension in the left colon. Measurements were averaged over time within each patient and, subsequently, among patients. Data were compared with chi-square, unpaired t, or Mann-Whitney rank sum tests; P < 0.05 was significant. Morphometric characteristics and other possible confounding factors were similar in the groups. Intraoperative tissue oxygen tension in hypercapnic patients was significantly greater in the arm (mean +/- SD: 116 +/- 29 mmHg vs. 84 +/- 25 mmHg; P = 0.006) and colon (median [interquartile range]: 107 [81-129] vs. 53 [41-104] mmHg; P = 0.020). During supplemental oxygen administration, mild intraoperative hypercapnia increased tissue oxygen tension in the arm and colon. Previous work suggests that improved tissue oxygenation will reduce infection risk via the proposed pathomechanism, although only an outcome study can confirm this.

Effects of isovolaemic haemodilution on oxygenation of liver and skeletal muscle

Hydroxyethyl starch is frequently used for volume substitution during surgical procedures and for isovolaemic haemodilution. Haemodilution has also been shown to improve tissue oxygen tension in skeletal muscle: However, effects of this volume substitute on tissue oxygen tension of the liver during haemodilution remains unknown. Fourteen foxhounds were anaesthetized with fentanyl/midazolam and mechanically ventilated with 30% oxygen. Following splenectomy animals were randomly assigned to a control group without haemodilution but fluid substitution with Ringer's lactate (Group C) or underwent isovolaemic haemodilution to a haematocrit of 25% with hydroxyethyl starch 70/0.5 (Group H). Haemodynamic parameters and oxygen transport during 100 min following isovolaemic haemodilution were measured. Liver oxygen tension was recorded using a flexible polarographic electrode tonometer, whereas in the muscle a polarographic needle probe was used. Animal characteristics and baseline haematocrit were similar in both groups. At baseline the tissue oxygen tension of liver and skeletal muscle were not different between groups. Haemodilution with hydroxyethyl starch 70/0.5 provided augmentation of mean liver tissue oxygen tension (baseline: 46 +/- 13 mmHg; 20 min: 60.3 +/- 12 mmHg; 60 min: 60 +/- 16 mmHg; 100 min: 63 +/- 16 mmHg; P < 0.05 vs. baseline), while oxygen tensions in Group C remained unchanged (baseline: 48 +/- 16 mmHg; 20 min: 52 +/- 19 mmHg; 60 min: 49 +/- 12 mmHg; 100 min: 52 +/- 16 mmHg) and no differences could be detected between groups. Oxygen tension in skeletal muscle changed as follows: Group H - baseline: 24 +/- 32 mmHg; 20 min: 32 +/- 3 mmHg; 60 min: 33 +/- 7 mmHg; 100 min: 33 +/- 11 mmHg. Group C - baseline: 22 +/- 6 mmHg; 20 min: 21 +/- 3 mmHg; 60 min: 24 +/- 4 mmHg; 100 min: 18 +/- 4 mmHg (P < 0.05 vs. baseline, p < 0.05 vs. Group C). In this animal model, isovolaemic haemodilution with hydroxyethyl starch 70/0.5 increased tissue oxygen tension in liver and skeletal muscle in comparison with baseline values. However, when compared between groups haemodilution only resulted in an increase of tissue oxygen tension in the muscle but not in the liver.

Hyperbaric oxygen therapy and in vitro fertilization—a pilot study

Objective: To determine the safety, tolerability and effects of hyperbaric oxygen therapy (HBO) when used during ovarian stimulation for IVF. Angiogenesis and oxygen delivery is critical to the preovulatory ovarian follicle. Impaired angiogenesis in the ovary has been hypothesized to contribute to reduced fertility and increased errors of meiosis in older reproductive age women. Hyperbaric oxygen therapy (HBO) greatly increases tissue oxygen tension and VEGF concentrations, leading to increased angiogenesis in hypoxic tissues.

SUPPLEMENTAL OXYGEN ADMINISTRATION DURING ISOFLURANE ANESTHESIA INCREASES SKELETAL MUSCLE OXYGEN TENSION

S152 INTRODUCTION: The major defense against surgical wound infections is oxidative killing by neutrophils. [1] Therefore, perioperative supplemental oxygen administration may decrease the incidence of wound infections, which has been confirmed in a bacteria-infection model in pigs. [2] However, tissue oxygen availability in humans is a complex function of arterial oxygen tension and local blood flow. Increased arterial oxygen tension (hyperbaric oxygenation) in critically ill patients without anesthesia is associated with increased systemic vascular resistance [3] and peripheral vasoconstriction [4] resulting in a reduction of tissue oxygen supply. [5] Because administration of volatile anesthetics are generally associated with peripheral vasodilation, it is likely that supplemental oxygen administration during isoflurane anesthesia may increases tissue oxygen tension. METHODS: After IRB approval and consent, we studied patients undergoing elective colon surgery. They were anesthetized with isoflurane, and randomly assigned to or 80% (Group 1; n=10) 30% (Group 2; n=8) inspired oxygen in nitrogen during surgery. Perioperative anesthetic, fluids, and blood transfusion management were determined by protocol. Skeletal muscle tissue oxygen tension was measured by an automatically stepwise driven polarographic needle probe (Eppendorf-pO2-Histograph) placed in the quadriceps muscle. Arterial pO2 was measured from arterial blood probes. All measurements were determined 15 min after induction of anesthesia (30% inspired oxygen) and postoperatively during 1.0% endexspired isoflurane concentration (30% versus 80% inspired oxygen). Results were compared using ANOVA, Mann-Whitney-U and Wilcoxon. Rank-Test-Test. RESULTS: After induction of anesthesia baseline arterial PO2 and tissue oxygen tension (tPO2) did not differ between groups. Postoperative arterial oxygen tension was significantly greater in patients given 80% than 30% oxygen (349 +/- 77 vs. 114 +/- 36 mmHg; p<0.001). The mean tPO2 was also significantly higher during administration of 80% than 30% oxygen (group 1 vs. group 2: 48 mmHg vs. 24 mmHg; p<0.001). The pooled histograms showed a shift to the right toward higher oxygen tensions during 80% oxygen administration. Postoperative muscle tissue PO2 values below 10 mmHg were significantly reduced in group 1 when compared to the baseline and group 2 (p<0.01). DISCUSSION: Our data indicate that supplemental oxygen administration during isoflurane anesthesia increases skeletal muscle tissue oxygen tension. Because the first few hours following bacterial contamination constitute a decisive period during which infection is established, [6] supplemental oxygen administration during isoflurane anesthesia may reduce the wound infection rate.

Chinese herbal medicine increases tissue oxygen tension.

An herbal medicine widely used in China, anisodamine, was investigated to determine its effect on the tissue PO2 of an important neural tissue, the retina. The anisodamine was injected intravenously over 10 min into anesthetized cats. Although it reduced mean blood pressure an average of 26%, anisodamine simultaneously increased tissue PO2 an average of 20%. It may therefore be useful in treating clinical conditions thought to be secondary to tissue hypoxia, such as diabetic retinopathy and sickle cell crises.