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Biomedical subjects

N D Maynard

Publications and source records attributed to N D Maynard.

8 recordsLinked to original sources
PubMed1997

Liver function and splanchnic ischemia in critically ill patients.

STUDY OBJECTIVE: To investigate the concept that splanchnic ischemia leads to hepatic dysfunction in the critically ill. DESIGN: Prospective study and analysis of patient data. SETTING: A general ICU in an inner-city London teaching hospital. PATIENTS: Twenty-seven consecutive critically ill patients with evidence of inadequate tissue perfusion requiring pulmonary artery catheterization and mechanical ventilation. MEASUREMENTS: In all patients, we measured the hepatic metabolism of lidocaine (lignocaine) to monoethylglycinexylidide (MEGX) and the clearance of indocyanine green (both dynamic, flow-dependent tests of hepatic function) over the first 3 days following admission to the ICU. These were compared with results of standard liver function tests and related to tonometric assessment of gastric intramucosal pH (pHim) and outcome. RESULTS: There were no significant differences in bilirubin, aspartate aminotransferase, alkaline phosphatase, and prothrombin levels, or in indocyanine green clearance between survivors and nonsurvivors. On day 3, the median MEGX level was higher in survivors than in nonsurvivors (16 vs 2.4 ng/mL, p < 0.001), and the median MEGX level in nonsurvivors fell over the 3 days (20.6 to 2.4 ng/mL, p < 0.002). MEGX levels were significantly correlated with pHim (Spearman rank correlation coefficient [Rs] = 0.69, p < 0.001) as were the changes in the two measurements over the 3 days (Rs = 0.46, p < 0.02). The MEGX formation test and gastric pHim were the most discriminatory with regard to death and survival. CONCLUSIONS: Our findings suggest that critically ill patients develop significant hepatic dysfunction that is associated with a poor outcome. This is likely to be due to a mismatch between hepatic metabolic demand and blood flow, and the MEGX formation test appears to be an extremely effective means of assessing liver function and flow in this group of patients.

Critical Illness↗
PubMed1996

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.

Aged↗
PubMed1995

Increasing splanchnic blood flow in the critically III.

STUDY OBJECTIVE: To assess the effect of low dose dopexamine and dopamine on splanchnic blood flow as measured by gastric intramucosal pH, hepatic metabolism of lidocaine (lignocaine) to monoethylglycinexy-lidide (MEGX), and plasma disappearance rate of indocyanine green (ICG). DESIGN: Single-blind randomization of patients with a gastric intramucosal acidosis to receive dopexamine (ten patients), dopamine (ten patients), or saline solution (five control patients) for 2 h. SETTING: All 25 patients were in the ICU of Guys' Hospital. PATIENTS: All patients met the criteria for the diagnosis of the systemic inflammatory response syndrome, were mechanically ventilated, and had pulmonary artery catheters placed. All had a low gastric intramucosal pH and had a median first 24-h acute physiology and chronic health evaluation (II) score of 22 (range, 7 to 40). MEASUREMENTS AND INTERVENTIONS: Baseline measurements of gastric intramucosal pH, MEGX formation from lidocaine, ICG plasma disappearance rate, heart rate, mean arterial pressure, pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, oxygen uptake index, systemic vascular resistance, and arterial pH were taken. Dopexamine (1 mg.kg-1.min-1), dopamine (2.5 mg.kg-1.min-1), or 0.9% saline solution was then infused for 2 h, after which a repeated set of the measurements was taken. RESULTS: Dopexamine at a low dose had no effect on any of the systemic measurements. The median intramucosal pH rose from 7.23 to 7.35 (p < 0.005), the median ICG plasma disappearance rate from 7.6 to 11.3%.min-1 (p < 0.02), and the median MEGX concentration from 4 to 10.2 ng.mL-1 (p < 0.005). Dopamine had no effect on any of the measured variables. There were no changes in the control group. CONCLUSIONS: Low-dose dopexamine increases splanchnic blood flow as measured by gastric intramucosal pH, MEGX formation from lidocaine, and ICG clearance. The lack of any change in the systemic measurements suggests that these effects are the result of a selective vasodilatation of the splanchnic vessels. At the dose used in this study, dopamine had no effect on splanchnic blood flow. Dopexamine may be useful in the management of splanchnic ischemia in the critically ill.

Adult↗