Effect of dopexamine on calculated low gastric intramucosal pH following valve replacement

Abstract

Gastric tonometry was used to study the possible effect of dopexamine infusion on a low calculated intramucosal pH (pHi) as a sign of splanchnic ischemia. Measurements were made during surgery and for approximately 18 hours postoperatively on 19 non-selected adult patients undergoing valve replacement. Patients developing a postoperative pHi > 7.30 were randomized to receive dopexamine (2 micrograms.kg-1 min-1) or placebo in a double blind fashion. Eighteen patients were randomized, 10 to receive dopexamine and 8 to placebo. The calculated pHi remained unchanged for the first 2 hours in both groups. After 4 hours a significant (P < 0.05) decrease in pHi was noted in the dopexamine group which remained significantly below the placebo group during the monitoring period. The dopexamine treated patients had a significantly longer period of low pHi but the pH-gap i.e. the difference between arterial pH and pHi did not differ between the two groups. Patients with postoperative complications, defined as infections (2), myocardial infarction (1), single- (2) or multiple organ failure and death (1), did not have longer periods with pHi below 7.30. In these patients, however, a pH-gap > 0.12 occurred more often than in those without complications, indicating that an increased incidence of complications was related to a pH-gap > 0.12. It is our opinion that true mucosal ischemia is best detected by estimating the difference in carbon dioxide tension between arterial blood and mucosa. This can be expressed either directly as PCO2-gap (PtonCO2-PaCO2) or indirectly as pH-gap.

The role of vasoactive agents in the resuscitation of microvascular perfusion and tissue oxygenation in critically ill patients

“…Apart from this heterogeneity in blood flow between regional circulation and microcirculation, experimental data also suggested regional heterogeneity in blood flow between the gastric and colon region during the use of dopexamine in sepsis [78]. In postoperative cardiac surgery no difference in pCO 2 g-a between low-dose dopexamine and placebo could be detected [79]. In another study pH i did not rise despite an increment in ICG-measured splanchnic blood flow and cardiac output [80].…”

Changes in p i CO 2 reflect splanchnic mucosal ischaemia more reliably than changes in pH i during haemorrhagic shock

“…Nearly all tonometric parameters contain an arterial blood gas variable in their method of calculation, except intramucosal partial pressure of carbon dioxide (p i CO 2 ). pH i gastric mucosal pH, [HCO 3 -] bicarbonate concentration, pCO 2 partial pressure of carbon dioxide Tonometric parameter Arterial blood gas parameter pH i [13] [HCO 3 -] [H + ] gap [33] pH a [pCO 2 ] gap [15,29] p a CO 2 p i CO 2 [21] The animals were endotracheally intubated and mechanically ventilated with 50% O 2 at a rate of 10 cycles·min -1 and a positive end expiratory pressure (PEEP) of 7 cm H 2 O (Servo 900B, Siemens Elema, Solna, Sweden). During surgical preparation, tidal volume was adjusted in order to maintain normocapnia, which was confirmed using repeated measurement of arterial pCO 2 .…”

“…However, there is disagreement concerning the most suitable parameter for clinical use. Some authors recommend pH i or p i CO 2 [32], others prefer the difference between tonometric and arterial pCO 2 concentrations (pCO 2 gap) [15,29]. This variety of parameters, based on the same measurement technique, is confusing and prevents the direct comparison of data presented in the literature.…”

Acute normovolaemic haemodilution does not aggravate gastric mucosal acidosis during cardiac surgery

“…However, this effect can be blocked by the administration of ranitidine, as performed in the present study [23]. Finally, it has been demonstrated in critically ill patients that pHi depends on the arterial acid-base balance [24] and that the calculation of the difference between pHa and pHi allows detection of splanchnic perfusion and oxygenation disorders more specifically [25]. In the present study, the calculation of pHa -pHi did not provide any divergent information from the measurement of pHi itself.…”