Non-invasive endoscopic technique to assess gastrointestinal perfusion

Colon Perfusion Patterns During Colorectal Resection Using Visible Light Spectroscopy

BACKGROUND

The impact of blood supply to the anastomosis on development of anastomotic leakage is still a matter of debate. Considering that bowel perfusion may be affected by manipulation during surgery, perfusion assessment of the anastomosis alone may be of limited value. We propose perfusion assessment at different time points during surgery to explore the dynamics of bowel perfusion during colorectal resection and its impact on outcome.

METHODS

In this prospective cohort study, patients undergoing elective colorectal resection were eligible. Colon perfusion was evaluated using visible light spectroscopy. Main outcome was the difference in colon perfusion, quantified by measuring tissue oxygen saturation (StO₂) in the colonic serosa, before and after anastomosis during surgery.

RESULTS

We included 58 patients between July 2013 and November 2015. Colon perfusion increased by an average of 5.9% StO₂ during surgery (95% confidence interval 3.1, 8.8; P < 0.001). The number of patients with abnormal perfusion (defined as StO₂ < 65%) decreased from 50% at the beginning to 24% by the end of surgery. Six patients (10%) developed anastomotic leaks (AL), of which five patients had abnormal perfusion at the beginning of surgery, whereas four patients had normal StO₂ at the anastomosis.

CONCLUSION

Colon perfusion significantly increased during colorectal surgery. Considering that one quarter of patients had suboptimal anastomotic perfusion without developing AL, impaired blood flow at the anastomosis alone does not seem to be critical. Further investigations including more patients are necessary to evaluate the impact of perioperative parameters on colon perfusion, anastomotic healing and surgical outcome.

The width of a gastric tube has no impact on outcome after esophagectomy

BACKGROUND

We evaluated the impact of the size of gastric tubes on tissue blood flow of the anastomotic site, the frequency of leakage and the postoperative nutritional status.

METHODS

Forty-four patients were randomly allocated to either reconstruction using subtotal stomach (n = 22) or to reconstruction using slender gastric tube (n = 22) after esophagectomy. The tissue blood flow at the anastomotic site was measured. The postoperative nutritional status of 17 patients without recurrence was examined. Possible correlations between the type of esophageal substitute and the tendency to leakage as well as postoperative nutritional status were examined.

RESULTS

There was no significant difference in the tissue blood and the frequency of leakage between the types of gastric tubes. There was no significant difference noted between the two in the postoperative nutritional status at 6 and 12 months after operation.

CONCLUSIONS

The width of gastric tube has no impact on tissue blood flow, the frequency of leakage, and the postoperative nutritional status after esophagectomy.

Microcirculatory perfusion of the canine esophagus before and after blind longitudinal dissection and thoracoscopic distal transsection

In the treatment of distal esophageal pathology, surgical mobilization and exteriorization of the thoracic esophagus can be necessary. This may threaten its vascularization. We investigated the effect of longitudinal dissection and distal transsection on the microcirculatory perfusion of the canine esophagus. Esophageal perfusion and muscular oxygenation were investigated in 11 dogs using laser Doppler fluxmetry and oxygen pressure measurements before and up to 2 weeks after longitudinal dissection with and without distal thoracoscopic transsection. Histological examination was performed at the end of the follow-up period. Distal esophageal perfusion was higher than proximal. Longitudinal dissection caused an insignificant reduction, whereas additional transsection significantly lowered esophageal perfusion, which was restored only partially during follow-up. After transsection distal muscular oxygen pressure was also significantly lower than proximal. Histologically, no significant ischemic cell damage was observed. Laser Doppler perfusion measurement is a feasible technique to measure (changes in) microcirculatory circulation of the esophageal wall. This may be useful in clinical settings to monitor the viability of the esophagus after surgical interventions. Distal transsection substantially reduces esophageal perfusion without apparent short-term histological damage.

Non-invasive measurement of colonic blood flow distribution using laser Doppler imaging

BACKGROUND

This study tested a prototype laser Doppler scanner for the measurement of human colonic blood flow.

METHODS

Blood flow distribution was assessed in human colon during operation in six controls and in six patients with inflammatory bowel disease undergoing colectomy. Image processing software analysed several hundred reading points, expressing average flow in perfusion units.

RESULTS

Blood flow in the colon was not significantly lower in the control group than in patients with inflammatory bowel disease (mean(s.e.m.) 297.8(24.5) versus 347.2(59.0) perfusion units, P = 0.12). Intestinal colonic mural blood supply was demonstrated up to a distance of 6 cm and ischaemia demarcation lines were identified before the onset of visible changes.

CONCLUSIONS

This prototype laser Doppler flowscanner overcomes the previous limitations of laser Doppler flowmeters and may have many clinical and research applications.

Assessment of human colon cancer protein kinetics in vivo

BACKGROUND

Malignancies enlarge because protein synthesis exceeds the rate of breakdown; however, the specific protein kinetic pattern remains unknown. Determining in vivo protein kinetic rates for a tumor may be useful for quantifying individual responses to a specific therapy. The aim of this study was to assess whether the growth of tumors is related to an increase in protein synthesis or an inhibition of protein breakdown.

METHODS

Five patients (age, 59 +/- 3 years) with adenocarcinoma of the colon undergoing colonoscopy were studied. Tissue protein synthesis and breakdown rates were measured in vivo for both segments of colon cancer and adjacent normal-appearing colonic mucosa by using a primed, continuous infusion of 1(13)C leucine with tissue biopsy and quantitation of regional blood flow by laser Doppler flowmetry.

RESULTS

Segments of colon cancer had a significantly (p < 0.05) greater rate of protein synthesis as quantitated by both the fractional rate of protein synthesis (Ca 45.4% +/- 5.0%/day versus nl mucosa 35.7% +/- 3.1%/day; mean +/- SEM) and by the tissue synthesis rate (Ca 69.4 +/- 9.0 versus nl mucosa 51.6 +/- 5.2 mumol/L leucine/day/100 gm tissue). Regional blood flow was significantly elevated in the cancer (Ca 110.9 +/- 5.8 versus nl mucosa 91.2 +/- 2.9 ml/min/100 gm), which contributed to commensurate rates of tissue breakdown (Ca 28.6 +/- 2.0 versus nl mucosa 28.2 +/- 2.4 mumol/L leucine/day/100 gm).

CONCLUSIONS

These results illustrate that human colon cancers grow in vivo as a result of increases in protein synthesis. Furthermore, increases in regional blood flow limit the rate of tissue protein breakdown of colon cancer, thereby contributing to growth of the malignancy. These findings support the contention that therapeutic strategies aimed at negating this inherent increase in protein synthesis or limiting blood flow may effectively limit the growth of malignancies. This methodology may also provide an index for evaluating the effectiveness of future therapies aimed at reducing tumor growth for individual patients.

Dynamics of skin blood flow in human sepsis

OBJECTIVE

The study was undertaken to determine if sepsis alters the pattern of vasomotion and reactive hyperaemia in the skin.

DESIGN

This was a prospective, observational study.

SETTING

The study was performed in the medical and surgical intensive care units of a tertiary referral hospital.

PATIENTS AND PARTICIPANTS

11 patients with sepsis (using Bone's criteria [1]), were compared with 19 patients recovering from coronary artery bypass grafting who were used as non-septic controls. Nineteen normal volunteers were also studied.

MEASUREMENTS AND RESULTS

Skin blood flow was measured on the forearm using laser Doppler flowmetry at rest and after 2 min arterial occlusion with a tourniquet. The resting blood signal was analyzed by calculating the mean skin blood flow, the power of the skin blood flow signal (variance) and the power spectrum. The rate of recovery after arterial occlusion was determined by calculating the peak increase in skin blood flow and the time constant of the decay of skin hyperaemia back to baseline flow. Patients with sepsis had a mean skin blood flow of 6.24 (3.48) ml min-1 per 100 g tissue compared with 4.35 (1.41) ml min-1 per 100 g tissue for the patients after coronary artery bypass grafting (p < 0.05). The septic patients also showed a marked increase in the fraction of total power in the 0.1-0.15 Hz frequency band (0.19 (0.17) versus 0.068 (0.033), p < 0.05), a decreased peak hyperaemic response (40 (23)% increase in flow above baseline after cuff release versus 147 (19)%) and a prolonged time constant for recovery from hyperaemia (22.8 (12.7) versus 11.7 (8.5) seconds, p < 0.05). These results imply an increased local rather than central control of skin blood flow.

CONCLUSION

The laser Doppler flowmeter allows local rather than global haemodynamics to be studied. Abnormalities of skin blood flow control are found in sepsis, and this technique may prove useful to monitor the effects of treatment, especially if the use of laser Doppler flowmetry can be extended to other organs at risk of damage during sepsis such as gastro-intestinal mucosa.

Laser Doppler flowmetry for estimation of bone blood flow: studies of reproducibility and correlation with microsphere technique

The blood flow in the femoral condyles of six pigs was measured by the microsphere technique and by laser Doppler flowmetry (LDF) before and after clamping of the external iliac artery. A significant decrease in the bone blood flow was found with both microsphere and LDF measurements, and a high correlation was found between the two methods. After release of the arterial clamp, the LDF values rapidly returned to approximately the same values as before clamping. In a second part of the study, the LDF output signal was studied in the intertrochanteric area of eight patients. The reproducibility of two LDF measurements at the same location was within 15%. The temporal variability of the LDF signal during 10 min of recording showed only slight variations. It is concluded that LDF is relative in nature and that the mean LDF output signal is suitable for monitoring dynamic responses of the bone blood flow to various stimuli. Several consecutive measurements have to be performed if the blood flow at different locations of a specific bone are to be compared with each other.

Laser Doppler assessment of human colonic blood flow

We have used laser Doppler flowmetry to assess human colonic blood flow in patients with healthy mucosa and in those with active proctitis. We report a significant correlation between colonic serosal laser Doppler flux readings and serosal tissue oxygen tension (n = 45: r = 0.671: p = 0.001). Mucosal blood flow was measured using the PF309 probe of a Perimed Pf2b set on 12 kHz frequency shift. There was no significant difference throughout the colon in healthy patients. The flow in rectal mucosa was significantly higher in patients with proctocolitis than in normal mucosa.

Human gastric perfusion: evidence for non-uniformity of blood flow

Post-mortem injection studies have demonstrated marked differences in the course and distribution of arterioles in the stomach, but evidence of differential perfusion in man is lacking. Using the non-invasive laser Doppler technique, we studied 38 patients referred for gastroscopy for dyspeptic symptoms. Flux measurements were made at nine sites: distal oesophagus, cardia, mid-body and antrum on lesser and greater curves, and pre- and post-pylorus. In all cases the stomach was macroscopically normal. Flux in the proximal stomach was significantly greater than that in the antrum, (P less than 0.001, Student's t test). This in vivo study demonstrates a flow gradient related to the previously demonstrated anatomical differences.