Assessment of the perfusion in peripheral tissue beds by subcutaneous oximetry and gastric intramucosal pH-metry in elective colorectal surgery

Effect of oral hydration on skin microcirculation in healthy young and midlife and older adults

Clinically undetected underhydration lowers subcutaneous tissue oxygen, impairs healing and increases wound infection. This study examined the effect of supplemental oral hydration on noninvasive measures of skin temperature (T(s)), transcutaneous skin O(2) (PtcO(2)), and CO(2) (PtcCO(2)), and skin blood flow (laser Doppler fluxmetry [Flux]=concentration of moving blood cells [CMBC] x Velocity) in healthy adults. Nineteen Control and 18 Test (Hydrated) subjects participated. Ad libitum fluid intake was allowed before the experiment. Sensors were placed on the chest, lower legs, and feet. Time 1 resting supine T(s), PtcO(2)/PtcCO(2), and Flux/CMBC/Velocity were obtained. Then, the Test group ingested 500 mL of H(2)O. Time 2 measures were obtained 30 minutes later. Data were analyzed using ANOVA. Change in T(s), PtcO(2), PtcCO(2), and Velocity did not differ between groups. Flux increased more in the Test than in the Control group (p<0.01). The Flux change was explained by a CMBC increase (p<0.05). For midlife/older subjects only, the CMBC change was greater in the Test than in the Control group (p<0.01). Flux may be sufficiently sensitive to detect microvascular changes in response to supplemental oral hydration. These data also suggest that subtle levels of hypoperfusion due to underhydration may exist in community-dwelling healthy midlife/older adults in their natural state.

Gut intramucosal pH as an early indicator of effectiveness of therapy for hemorrhagic shock

OBJECTIVE

To determine the value of intramucosal pH for evaluating the effectiveness of treatment for hemorrhagic shock.

DESIGN

Randomized, controlled trial.

SETTING

University center, animal laboratory.

SUBJECTS

Eighteen piglets, weighing 17 to 23 kg.

INTERVENTIONS

Anesthetized animals were bled to a mean arterial pressure (MAP) of 40 to 50 mm Hg and a 70% reduction in cardiac output during a 1-hr period. This state was maintained for the next hour. The piglets were treated with crystalloid solution to restore cardiac output and MAP during the subsequent 80 mins of the experiment. Some animals were given vasoactive drugs during volume therapy to modulate splanchnic perfusion and increase the diversity of values of various variables.

MEASUREMENTS AND MAIN RESULTS

Systemic hemodynamic and oxygen transport variables were monitored. Tissue oxygen tensions were measured in the liver and abdominal subcutaneous tissue layer. Gut intramucosal pH (pHi) was determined, using a balloon tonometer. The animals were divided into responders (n=9) and nonresponders (n=9) according to whether pHi increased or decreased during resuscitation. Hemodynamic and oxygen transport variables improved in the group of responders. In the group of nonresponders, values decreased. Liver and subcutaneous oxygen tensions increased during the initial phase of resuscitation in both groups but decreased after 30 mins in the nonresponder group.

CONCLUSIONS

The change in pHi during the first hour of resuscitation could be used to divide animals treated uniformly from a hemodynamic point of view into two distinct groups with seemingly different outcome. The minimally invasive method could be of value for early evaluation of the results of treatment of hemorrhagic shock.

Gastric tonometry: precision and reliability are improved by a phosphate buffered solution

OBJECTIVE

To compare a phosphate buffered solution with normal saline as tonometric fluid in intramucosal PCO2 measurement in humans.

DESIGN

Prospective, unblinded comparison.

SETTING

Postsurgical critical care unit of a university hospital.

PATIENTS

Six septic patients.

INTERVENTIONS

Two tonometric probes were positioned in the gastric lumen in each patient. One tube was used for conventional tonometry (saline-filled balloon), while phosphate buffered solution was instilled into the second tube.

MEASUREMENTS AND MAIN RESULTS

PCO2 was determined with three blood gas analyzers (ABL 2 [Radiometer, Copenhagen, Denmark], Corning 288 [Ciba Corning Diagnostics GmbH, Neuss, Germany], and StatProfile 9 Plus [Nova Biomedical, Waltham, MA]). Eight parallel PCO2 measurements per patient were evaluated, yielding a total of 48 measurements with each tonometric solution. Intrainstrumental comparison of the PCO2 determinations demonstrated an increase of 12.3 +/- 9.9% for ABL 2, 3.10 +/- 12.9% for Ciba Corning 288, and 101.2 +/- 31.5% for StatProfile 9 Plus with the phosphate buffered solution. The PCO2 values were decreased by the following amounts when the three instruments were compared, using the saline method: 14.2 +/- 8.2% (Ciba Corning 288 vs. ABL 2); 40.7 +/- 9.9% (StatProfile 9 Plus vs. ABL 2); and 30.9 +/- 9.35% (StatProfile 9 Plus vs. Ciba Corning 288). The difference in PCO2 determination, resulting from the different instrument designs, were significant between the three blood gas analyzers (p<.001). In addition, the variance of the intramucosal PCO2 values was significant between blood gas analyzers (p<.001) with normal saline as tonometric solution, but not with phosphate buffered solution. The coefficients of determination between PCO2 values in saline and phosphate buffered solution were r2=.85 for ABL 2, r2=.81 for Ciba Corning 288, and r2=.74 for StatProfile 9 Plus. When all 48 PCO2 values were analyzed, the interinstrumental coefficients of determination within a method for saline (and for phosphate buffered solution in parenthesis) were:r2=.83 (.92) between ABL 2 and Ciba Corning 288, r2=.72 (.92) between ABL 2 and StatProfile 9 Plus, and r2=.81 (.98) between Ciba Corning 288 and StatProfile 9 Plus.

CONCLUSIONS

A considerable instrumental bias in PCO2 analysis is observed when saline is used as tonometric fluid in gastric tonometry, thus preventing a reliable determination of intramucosal pH. The present in vivo data show that the accuracy and reliability of intramucosal pH measurement can be improved by the use of phosphate buffered solution as tonometric fluid.

Gastric intramucosal pH predicts outcome after surgery for ruptured abdominal aortic aneurysm

OBJECTIVE

The mortality associated with repair of ruptured abdominal aortic aneurysms (RAAA) remains obstinately high and many deaths result from multiple organ failure which is likely to be related to splanchnic ischaemia. The aim of this study is to investigate the importance of splanchnic ischaemia in determining outcome from RAAA by comparing gastric intramucosal pH with other methods of assessing the adequacy of splanchnic oxygenation.

DESIGN AND SETTING

Prospective cohort of patients following surgery for RAAA admitted to the Intensive Care Unit of Guy's Hospital, London.

OUTCOME MEASURES

Gastric intramucosal pH (pHim) and global haemodynamic, oxygen transport and metabolic variables were measured on admission, at 12 h and at 24 h after admission. Results were compared between survivors and non-survivors and Receiver Operating Characteristic (ROC) curves were constructed to assess the ability of each measurement to predict outcome.

RESULTS

The median 24 h APACHE II was 18 and the ICU mortality 45.5%. Gastric pHim was significantly higher in survivors than non-survivors at 24 h (7.42 vs. 7.24, p < 0.01). In survivors who had a low intramucosal pH (pHim) on admission there was a significant improvement over the first 24 h (7.26 to 7.40, p < 0.05), whereas in patients who subsequently died, and had a normal pHim on admission, there was a significant fall in pHim (7.35 to 7.16, p < 0.05). ROC curves showed that gastric pHim was the most sensitive measurement for predicting outcome in these patients.

CONCLUSIONS

Gastric intramucosal pH is the most reliable indicator of adequacy of tissue oxygenation in patients with RAAA, suggesting that splanchnic ischaemia may have played an important role in determining survival.

Bedside assessment of myocardial performance in the critically ill

No measurement of myocardial performance currently available in the ICU can be regarded is ideal. Table 2 summarises the main features of the major monitoring techniques. As many of the indices of myocardial performance are interdependent, quantifying the contribution of each component to overall cardiac function is not possible currently, and the clinical utility of monitoring each individually is not therefore established. Bedside measurements of LV dimensions, volumes and ejection fraction, and the other indices of systolic and diastolic function can now be made, but the case for their routine use in influencing clinical practice remains unproven. Transoesophageal echocardiography has an important and established diagnostic role and has been used successfully for continuous monitoring during surgery, but practical considerations seriously limit its potential for routine use. Radionuclide techniques allow the measurement of many of the same parameters and have the potential for continuous use, but practical problems and the additional risk of radiation exposure may limit this application in the critical care environment. Doppler techniques are non-invasive, provide continuous data and are simple to operate, but the data provided has important limitations. Although the pulmonary artery catheter has been in use for over twenty years, questions regarding the information is provides concerning myocardial function remain and the extent to which it should influence therapeutic decisions is still controversial. However with the development of additional facilities, particularly the continuous measurement of cardiac output the pulmonary artery catheter seems likely to remain the mainstay of bedside monitoring of myocardial performance in the critically ill in the immediate future.

Early detection of major complications after abdominal aortic surgery: predictive value of sigmoid colon and gastric intramucosal pH monitoring

The early detection and reversal of gastrointestinal ischaemia is thought to play a key role in minimizing the incidence of complications after abdominal aortic surgery. In an open prospective non-selective study intramucosal pH (pHi) was monitored in 27 patients undergoing elective aortic surgery and in seven submitted to emergency procedures. The pHi was monitored in the sigmoid colon in all 34 patients and in the stomach in 26. Eight patients developed major complications, four of whom had ischaemic colitis, and five died. Sigmoid acidosis (pHi below 7.10) served as an early warning; if acidosis was reversed within 2 h no major complication developed, if prolonged it was predictive of major morbidity (sensitivity 100 per cent, specificity 92 per cent). A colonic pHi below 6.86 predicted endoscopically detectable ischaemic colitis. A gastric pHi below 7.20 predicted major complications with a sensitivity of 100 per cent and specificity of 81 per cent. Both monitoring procedures were considered feasible, although monitoring in the sigmoid colon was found to be superior for the patients studied.

Evaluation of tissue oximetry in perioperative monitoring of colorectal surgery

Twenty patients undergoing elective colorectal surgery were studied during and after operation by means of tissue oximetry measuring the subcutaneous partial pressure of oxygen (PscO2) and by gastric intramural pH measurement. Mean(s.d.) PscO2 recorded 24 h after surgery was significantly lower than the peroperative value: 14(10) versus 24(14) mmHg, P less than 0.02. The postoperative PscO2 was also significantly lower than that measured in a control group of ten healthy volunteers: 14(10) versus 34(18) mmHg, P less than 0.001. The peroperative PscO2 of the patients who developed a postoperative complication was significantly lower than that of those who had an uneventful postoperative clinical outcome: 16(9) versus 32(14) mmHg, P less than 0.02. The peroperative PscO2 of the patient group with complications was also significantly lower than that of the control group: 16(9) versus 34(18) mmHg, P less than 0.02. The peroperative PscO2 of the group of patients without complications was almost identical to that of the control group. During operation only one patient developed gastric intramural acidosis. Perioperative oxygen debt and the response of subcutaneous tissue oxygen tension to oxygen breathing seemed to correlate better with clinical outcome than gastric wall pH values and the conventional parameters of tissue perfusion.