Gastric-arterial PCO2 gradient does not reflect systemic and splanchnic hemodynamics or oxygen transport after cardiac surgery

Gastric tonometry versus cardiac index as resuscitation goals in septic shock: a multicenter, randomized, controlled trial

INTRODUCTION

Resuscitation goals for septic shock remain controversial. Despite the normalization of systemic hemodynamic variables, tissue hypoperfusion can still persist. Indeed, lactate or oxygen venous saturation may be difficult to interpret. Our hypothesis was that a gastric intramucosal pH-guided resuscitation protocol might improve the outcome of septic shock compared with a standard approach aimed at normalizing systemic parameters such as cardiac index (CI).

METHODS

The 130 septic-shock patients were randomized to two different resuscitation goals: CI >or= 3.0 L/min/m2 (CI group: 66 patients) or intramucosal pH (pHi) >or= 7.32 (pHi group: 64 patients). After correcting basic physiologic parameters, additional resuscitation consisting of more fluids and dobutamine was started if specific goals for each group had not been reached. Several clinical data were registered at baseline and during evolution. Hemodynamic data and pHi values were registered every 6 hours during the protocol. Primary end point was 28 days' mortality.

RESULTS

Both groups were comparable at baseline. The most frequent sources of infection were abdominal sepsis and pneumonia. Twenty-eight day mortality (30.3 vs. 28.1%), peak Therapeutic Intervention Scoring System scores (32.6 +/- 6.5 vs. 33.2 +/- 4.7) and ICU length of stay (12.6 +/- 8.2 vs. 16 +/- 12.4 days) were comparable. A higher proportion of patients exhibited values below the specific target at baseline in the pHi group compared with the CI group (50% vs. 10.9%; P < 0.001). Of 32 patients with a pHi < 7.32 at baseline, only 7 (22%) normalized this parameter after resuscitation. Areas under the receiver operator characteristic curves to predict mortality at baseline, and at 24 and 48 hours were 0.55, 0.61, and 0.47, and 0.70, 0.90, and 0.75, for CI and pHi, respectively.

CONCLUSIONS

Our study failed to demonstrate any survival benefit of using pHi compared with CI as resuscitation goal in septic-shock patients. Nevertheless, a normalization of pHi within 24 hours of resuscitation is a strong signal of therapeutic success, and in contrast, a persistent low pHi despite treatment is associated with a very bad prognosis in septic-shock patients.

Splanchnic blood flow and oxygen consumption: effects of enteral nutrition and dopexamine in the elderly cardiac surgery patient

BACKGROUND

After cardiac surgery, patients are at risk of organ dysfunction because of decreased perfusion. Different measures have been used to increase the splanchnic blood flow. We compared the effects of enteral nutrition and dopexamine on the cardiac output, splanchnic blood flow and oxygen consumption.

METHODS

Sixteen patients undergoing cardiac surgery were included. Indocyanine green extraction and thermodilution were used for repeated measurements of the splanchnic blood flow and cardiac output. On the first post-operative day, indocyanine green infusion was started. Patients were randomized to start with dopexamine (Dpx group) or enteral nutrition (EN group). After 180 min, both groups received a combination of dopexamine and enteral nutrition. Blood gases from the hepatic vein and pulmonary and radial arteries were analysed repeatedly.

RESULTS

In the Dpx group, the cardiac index increased with dopexamine infusion, but not when enteral nutrition was added. In the EN group, enteral nutrition alone did not increase the cardiac index, but dopexamine addition increased the cardiac index in this group. The splanchnic blood flow increased initially in the Dpx group, but then returned to baseline and remained constant on addition of enteral nutrition. In the EN group, the splanchnic blood flow initially remained at baseline, but increased after dopexamine addition. There was no difference between the groups with regard to systemic or splanchnic oxygen consumption or the oxygen extraction ratio. In the Dpx group, lactate increased from baseline with no further increase on addition of enteral nutrition. Lactate was unchanged in the EN group.

CONCLUSIONS

Dopexamine and enteral nutrition caused no adverse effects on oxygen consumption or the oxygen extraction ratio. Enteral nutrition did not increase the splanchnic blood flow or cardiac index. Dopexamine increased the systemic blood flow with only a transient effect on the splanchnic blood flow. Dopexamine increased the lactate concentration, possibly indicating a more ischaemic condition.

Gastric intramucosal perfusion during descending aortic repair under femoro-femoral bypass

The changes in gastric mucosal perfusion during distal aortic perfusion with femoro-femoral bypass (F-F bypass) were assessed by air-automated gastric tonometry. A prospective study was performed in six patients who underwent descending aortic surgery for aortic aneurysm under F-F bypass with mild hypothermia (34 degrees C). Gastric intramucosal pH (pHi) and PaCO2-PgCO2 gap (PCO2 gap) were measured. Data are presented as means and standard deviations and analyzed by using one-way analysis of variance followed by Scheffe test. Perioperative variables of hepatorenal functions are also evaluated. The PCO2 gap significantly increased during F-F bypass (3.0 +/- 2.1 mm Hg at control, 14.2 +/- 5.5 mm Hg during F-F bypass; p = 0.004), indicating abnormal gastric mucosal perfusion during F-F bypass. Significantly low pHi was found at weaning from F-F bypass (7.35 +/- 0.05 at control, 7.21 +/- 0.10 at weaning; p = 0.009), which might be related to progressing systemic metabolic acidosis. No impairment of hepatorenal functions was observed after the surgery. Distal perfusion with F-F bypass during descending aortic surgery could impair the gastric mucosal perfusion, but may have little effect on postoperative visceral dysfunction.

Vasopressors and intestinal mucosal perfusion after cardiac surgery: Norepinephrine vs. phenylephrine

OBJECTIVES

To evaluate the potential differential effects of norepinephrine, an alpha1-, beta1-, and beta2-receptor agonist, to the alpha1-agonist phenylephrine on jejunal mucosal perfusion, gastric-arterial PCO2 gradient, and the global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A randomized, prospective, interventional crossover study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Ten patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

Each patient received randomly and sequentially norepinephrine (0.052+/-0.009 microg/kg/min) and phenylephrine (0.50+/-0.22 microg/kg/min) to increase mean arterial blood pressure by 30%.

MEASUREMENTS AND MAIN RESULTS

Data on jejunal mucosal perfusion, jejunal mucosal hematocrit, and red blood cell velocity (laser Doppler flowmetry) as well as gastric-arterial Pco2 gradient (tonometry) and splanchnic oxygen extraction were obtained before (control) and during a 30-min drug infusion period after the target mean arterial blood pressure was reached. The procedure was sequentially repeated for the second vasopressor. Both drugs induced a 40-46% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, jejunal mucosal hematocrit, red blood cell velocity, nor gastric-arterial Pco2 gradient was affected by any of the vasopressors. Splanchnic oxygen extraction increased from 38.2% to 43.1% (p<.001) with norepinephrine and from 39.3% to 47.5% (p<.001) with phenylephrine. This increase was significantly more pronounced with phenylephrine compared with norepinephrine (p<.05). Mixed venous-hepatic vein oxygen saturation gradient increased with both drugs (p<.01), and the increase was more pronounced with phenylephrine (p<.05). Splanchnic lactate extraction was not significantly affected by any of the vasopressors.

CONCLUSIONS

Phenylephrine induced a more pronounced global alpha1-mediated splanchnic vasoconstriction compared with norepinephrine. Neither of the vasoconstrictors impaired perfusion of the gastrointestinal mucosa in postcardiac surgery patients. The lack of norepinephrine-induced, alpha1-mediated impairment of gastrointestinal perfusion is not explained by a beta2-mediated counteractive vasodilation but instead by possible mucosal autoregulatory escape.

Dopexamine and its role in the protection of hepatosplanchnic and renal perfusion in high-risk surgical and critically ill patients

BACKGROUND

Dopexamine is increasingly being used in high-risk surgical and critically ill patients to preserve hepatosplanchnic and renal perfusion. This systematic review of randomized controlled trials was undertaken to investigate the clinical evidence for using dopexamine in this role.

METHODS

Data sources included Medline, Cochrane Library, EMBASE and CINAHL and reference lists of relevant articles. Randomized controlled trials which compared dopexamine treatment with a control group, in high-risk surgical and critically ill adult patients and with primary outcome measures designed to assess hepatosplanchnic and renal perfusion were included. Articles not published in English were excluded.

RESULTS

Twenty-one trials were selected from the literature search. The results suggest that dopexamine may protect against colonic mucosal damage in patients undergoing abdominal aortic surgery and may improve gastric mucosal pHi in general surgical patients, especially those with preoperative gastric mucosal pHi measurements <7.35 and those undergoing pancreatico-duodenectomy surgery. Dopexamine may have beneficial effects on renal perfusion in patients undergoing cardiac surgery but appears to have little or no benefit on gastric mucosal pHi in the same patient population. In critically ill patients none of the studies demonstrated a beneficial effect of dopexamine on either hepatosplanchnic or renal perfusion.

CONCLUSION

The evidence provided by the existing studies is both inadequate and inconsistent. There is insufficient evidence to offer reliable recommendations on the clinical use of dopexamine for the protection of either hepatosplanchnic or renal perfusion in high-risk surgical patients. Furthermore, there is no current evidence to support a role for dopexamine in protecting either hepatosplanchnic or renal perfusion in critically ill patients.

EFFECTS OF DOPAMINE AND NOREPINEPHRINE ON SYSTEMIC AND HEPATOSPLANCHNIC HEMODYNAMICS, OXYGEN EXCHANGE, AND ENERGY BALANCE IN VASOPLEGIC SEPTIC PATIENTS

Dopamine is widely used to improve systemic and hepatosplanchnic hemodynamics and oxygenation during sepsis. However, some studies have suggest that norepinephrine may have beneficial effects on regional blood flow and metabolism, whereas dopamine might have deleterious effects related to redistribution of blood flow away from the intestinal mucosa or by decreasing directly the cell redox state. In 12 vasoplegic septic patients, we compared the effects of norepinephrine and dopamine on systemic and hepatosplanchnic hemodynamics, oxygenation, and energy metabolism. Catecholamines were administered in a crossover randomized order to maintain mean arterial pressure (MAP) at 80 mmHg. Hepatosplanchnic blood flow (Qspl) was determined using a continuous infusion of indocyanine green dye. Despite a similar MAP, the cardiac index was higher with dopamine than with norepinephrine (6.3 [5.3-7.3] vs. 4.3 [3.8-4.9] L.min.m) (P <0.001). Qspl was similar with both catecholamines, but the ratio of Qspl to cardiac output was significantly lower with dopamine (23.9% [17.5-33.5]) than with norepinephrine (33.5% [25.8-37]) (P <0.05). Although global O2 delivery and O2 consumption were higher with dopamine (782 [707-859] vs. 553 [512-629] mL.min.m, P <0.001 and 164 [134-192] vs. 128 [111-149] mL.min.m, P <0.001, respectively), hepatosplanchnic O2 delivery and consumption were not different. Hepatic lactate uptake was lower (0.47 [0.3-0.89] vs. 1.01 [0.69-1.34] mmol.min) (P <0.01), and hepatic venous lactate-to-pyruvate ratio was higher (15.3 [7.6-21.1] vs. 11.2 [6.6-15.1], P <0.05) with dopamine than with norepinephrine. In vasoplegic septic patients, maintaining mean arterial pressure, hepatosplanchnic hemodynamics, and oxygen exchange with dopamine requires a consequent increased cardiac output, which is responsible for an increased global oxygen demand when compared with norepinephrine. In addition, dopamine impairs the hepatic energy balance. Its position as a preferential treatment compared with norepinephrine in this context may therefore be questionable.

Methods of monitoring shock

Intensive monitoring is a crucial component of the management of shock. However, there is little consensus about optimal strategies for monitoring. Although the pulmonary artery catheter has been widely used, conflicting data exist about the utility of this device. A variety of other techniques have been developed in hopes of providing clinically useful information about myocardial function, intravascular volume, and indices of organ function. In addition, there is evolving evidence that targeting and monitoring certain physiological goals may be most important early in the course of shock. In this chapter, we examine many of the available monitoring techniques and the evidence supporting their use.

Clinical review: influence of vasoactive and other therapies on intestinal and hepatic circulations in patients with septic shock

The organs of the hepatosplanchnic system are considered to play a key role in the development of multiorgan failure during septic shock. Impaired oxygenation of the intestinal mucosa can lead to disruption of the intestinal barrier, which may promote a vicious cycle of inflammatory response, increased oxygen demand and inadequate oxygen supply. Standard septic shock therapy includes supportive treatment such as fluid resuscitation, administration of vasopressors (adrenergic and nonadrenergic drugs), and respiratory and renal support. These therapies may have beneficial or detrimental effects not only on systemic haemodynamics but also on splanchnic haemodynamics, at both the macrocirculatory and microcirculatory levels. This clinical review focuses on the splanchnic haemodynamic and metabolic effects of standard therapies used in patients with septic shock, as well as on the recently described nonconventional therapies such as vasopressin, prostacyclin and N-acetyl cysteine.

Effects of volume resuscitation on splanchnic perfusion in canine model of severe sepsis induced by live Escherichia coli infusion

INTRODUCTION

We conducted the present study to investigate whether early large-volume crystalloid infusion can restore gut mucosal blood flow and mesenteric oxygen metabolism in severe sepsis.

METHODS

Anesthetized and mechanically ventilated male mongrel dogs were challenged with intravenous injection of live Escherichia coli (6 x 10(9) colony-forming units/ml per kg over 15 min). After 90 min they were randomly assigned to one of two groups - control (no fluids; n = 13) or lactated Ringer's solution (32 ml/kg per hour; n = 14) - and followed for 60 min. Cardiac index, mesenteric blood flow, mean arterial pressure, systemic and mesenteric oxygen-derived variables, blood lactate and gastric carbon dioxide tension (PCO2; by gas tonometry) were assessed throughout the study.

RESULTS

E. coli infusion significantly decreased arterial pressure, cardiac index, mesenteric blood flow, and systemic and mesenteric oxygen delivery, and increased arterial and portal lactate, intramucosal PCO2, PCO2 gap (the difference between gastric mucosal and arterial PCO2), and systemic and mesenteric oxygen extraction ratio in both groups. The Ringer's solution group had significantly higher cardiac index and systemic oxygen delivery, and lower oxygen extraction ratio and PCO2 gap at 165 min as compared with control animals. However, infusion of lactated Ringer's solution was unable to restore the PCO2 gap. There were no significant differences between groups in mesenteric oxygen delivery, oxygen extraction ratio, or portal lactate at the end of study.

CONCLUSION

Significant disturbances occur in the systemic and mesenteric beds during bacteremic severe sepsis. Although large-volume infusion of lactated Ringer's solution restored systemic hemodynamic parameters, it was unable to correct gut mucosal PCO2 gap.

Noninvasive, near infrared spectroscopic-measured muscle pH and Po2 indicate tissue perfusion for cardiac surgical patients undergoing cardiopulmonary bypass*

OBJECTIVE

To determine whether near infrared spectroscopic measurement of tissue pH and Po2 has sufficient accuracy to assess variation in tissue perfusion resulting from changes in blood pressure and metabolic demand during cardiopulmonary bypass.

DESIGN

Prospective clinical study.

SETTING

Academic medical center.

SUBJECTS

Eighteen elective cardiac surgical patients.

INTERVENTION

Cardiac surgery under cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

A near infrared spectroscopic fiber optic probe was placed over the hypothenar eminence. Reference Po2 and pH sensors were inserted in the abductor digiti minimi (V). Data were collected every 30 secs during surgery and for 6 hrs following cardiopulmonary bypass. Calibration equations developed from one third of the data were used with the remaining data to investigate sensitivity of the near infrared spectroscopic measurement to physiologic changes resulting from cardiopulmonary bypass. Near infrared spectroscopic and reference pH and Po2 measurements were compared for each subject using standard error of prediction. Near infrared spectroscopic pH and Po2 at baseline were compared with values during cardiopulmonary bypass just before rewarming commenced (hypotensive, hypothermic), after rewarming (hypotensive, normothermic) just before discontinuation of cardiopulmonary bypass, and at 6 hrs following cardiopulmonary bypass (normotensive, normothermic) using mixed-model analysis of variance. Near infrared spectroscopic pH and Po2 were well correlated with the invasive measurement of pH (R2 =.84) and Po2 (R 2 =.66) with an average standard error of prediction of 0.022 +/- 0.008 pH units and 6 +/- 3 mm Hg, respectively. The average difference between the invasive and near infrared spectroscopic measurement was near zero for both the pH and Po2 measurements. Near infrared spectroscopic Po2 significantly decreased 50% on initiation of cardiopulmonary bypass and remained depressed throughout the bypass and monitored intensive care period. Near infrared spectroscopic pH decreased significantly during cardiopulmonary bypass, decreased significantly during rewarming, and remained depressed 6 hrs after cardiopulmonary bypass. Diabetic patients responded differently than nondiabetic subjects to cardiopulmonary bypass, with lower muscle pH values (p =.02).

CONCLUSIONS

Near infrared spectroscopic-measured muscle pH and Po2 are sensitive to changes in tissue perfusion during cardiopulmonary bypass.

Effects of norepinephrine alone and norepinephrine plus dopamine on human intestinal mucosal perfusion

OBJECTIVES

To evaluate the effect of norepinephrine alone and norepinephrine combined with dopamine on jejunal mucosal perfusion, gastric-arterial pCO(2) gradient, and global splanchnic oxygen demand-supply relationship after cardiac surgery.

DESIGN

A prospective interventional study.

SETTING

A university cardiothoracic intensive care unit.

PATIENTS

Eighteen patients were studied during propofol sedation and mechanical ventilation after uncomplicated coronary artery bypass surgery.

INTERVENTIONS

After control measurements, each patient received norepinephrine (50+/-26 ng.kg.min) to increase mean arterial blood pressure by 30% followed by addition of low-dose dopamine (2.6+/-0.3 microg x kg x min). Postdrug control measurements were performed 120 min after discontinuation of the catecholamines.

MEASUREMENTS AND RESULTS

Norepinephrine induced a 32% increase in systemic vascular resistance with no change in cardiac index. Neither jejunal mucosal perfusion, assessed by laser Doppler flowmetry, nor gastric-arterial pCO(2) gradient (tonometry) was affected by norepinephrine. Splanchnic O(2)-extraction increased ( P<0.05) and this increase was positively correlated to the individual dose of norepinephrine ( r = 0.78, P<0.0001). Splanchnic lactate extraction was increased by norepinephrine ( P<0.05). None of the patients had splanchnic lactate production during norepinephrine infusion. The addition of dopamine increased cardiac index by 27% ( P<0.001) and decreased splanchnic O(2 )extraction. Dopamine increased jejunal mucosal perfusion by 32% ( P<0.001) while the gastric-arterial pCO(2) gradient remained unchanged.

CONCLUSIONS

Vasopressor therapy with norepinephrine after cardiac surgery did not jeopardize intestinal mucosal perfusion in spite of a dose-dependent increase of the global splanchnic oxygen demand-supply relationship. The addition of dopamine increased intestinal mucosal perfusion.

Apparent heterogeneity of regional blood flow and metabolic changes within splanchnic tissues during experimental endotoxin shock

We conducted a randomized, controlled experiment of prolonged lethal endotoxin shock in pigs aiming at 1) simultaneously measuring perfusion at different parts of the gut to study the potential heterogeneity of blood flow within the splanchnic region; 2) studying the association among regional blood flows, oxygen supply, and different metabolic markers of perfusion; and 3) analyzing the association between histological gut injury and markers of perfusion and metabolism. The primary response to endotoxin was a decrease in systemic and splanchnic blood flow followed by hyperdynamic systemic circulation. Redistribution of blood flows occurred within the splanchnic circulation: superior mesenteric artery blood flow was maintained, whereas celiac trunk blood flow was compromised. Mucosal to arterial PCO(2) gradients did not reflect changes in total splanchnic perfusion, but they were associated with regional blood flows during the hypodynamic phase of shock. During hyperdynamic systemic circulation, PCO(2) gradients increased heterogeneously in the gastrointestinal tract, whereas luminal lactate increased only in the colon. Histological analysis revealed mucosal epithelial injury only in the colon. We conclude that markers of perfusion and metabolism over one visceral region do not reflect perfusion and metabolism in other splanchnic vascular areas. Intestinal mucosal epithelial injury occurs in the colon during 12 h of endotoxin shock while the epithelial injury is still absent in the jejunum. Hyperdynamic and hypotensive shock induces gut luminal lactate release in the colon but not in the jejunum. The association or causality between the mucosal epithelial injury and luminal lactate release remains to be elucidated.

IMPLICATIONS

Surrogate regional markers of tissue perfusion over one region do not reflect the state of perfusion over another. Therefore, regional metabolic monitoring (microdialysis) in multiple locations is needed. Although tonometry does not differentiate between macro-level regional perfusion defect and tissue injury, intestinal luminal microdialysis detects mucosal lactate release, which may be associated with epithelial injury. The degree of correlation or causality between the two remains to be evaluated.

Why measure cardiac output?

Although cardiac output is a primary determinant of global O₂ transport there are no absolute values that reflect circulatory adequacy, though very low values are of negative prognostic use. There is no agreement as to what constitutes a clinically relevant change in cardiac output. A recent clinical trial suggests that early goal-directed therapy aimed at increasing cardiac output improves survival. Thus, in some patients, measurement of cardiac output is indicated as an aid to prognosis, diagnosis and to monitor the adequacy of therapy. Gonzalez et al. compared PAC thermodilution cardiac output with indirect Fick measures of cardiac output. They found that at lower cardiac outputs (< 5 l/min) the agreement between the two techniques is good, whereas at higher flows increased differences exist between the two measures. As discussed in this commentary, this study did not address the three potential questions related to PAC monitoring of cardiac output. These questions are: can the PAC cardiac output data be used to monitor cardiac output? Do technical and physiological constraints limit the accuracy of PAC cardiac output? And; are PAC cardiac output measurement errors due to respiratory variation in pulmonary blood flow? Ways of answering each question are given.

Use of vasopressor agents in critically ill patients

Distributive shock is a common problem in intensive care. Systemic hypotension is a medical emergency and will cause end-organ injury if not reversed. There are relatively few medications available to treat distributive shock. Catecholamines are most widely used for this indication and work by stimulating alpha- and/or beta-adrenergic receptors. Vasopressin and corticosteroids may have a role in reversing refractory shock and work primary through nonadrenergic mechanisms. Shock is difficult to define using hemodynamic criteria, because the same hemodynamic values can be normal in one patient, yet represent shock in another. Thus, the appropriate therapeutic endpoints for vasopressor therapy are not uniform for all patients. Similarly, the available evidence comparing vasopressor agents in terms of safety and efficacy is limited. When used at doses necessary to reverse distributive shock, less potent vasoconstrictors (eg, dopamine) do not appear to be safer than more potent ones (eg, norepinephrine) and do not appear to be as effective.

Continuous monitoring of gastric intraluminal carbon dioxide pressure, cardiac output, and end-tidal carbon dioxide pressure in the perioperative period in patients receiving cardiovascular surgery using cardiopulmonary bypass

OBJECTIVE

To verify the hypothesis that the gastric intraluminal PCO2 (PgCO2) changes independently of the change in cardiac output (CO) during and after cardiovascular surgery using cardiopulmonary bypass (CPB), and that the elevation of PgCO2 affects the patients' morbidity.

DESIGN

Prospective, noninterventional study.

SETTING

Medical/surgical intensive care unit and operating theater of a university hospital.

PATIENTS

Sixteen adults patients receiving elective cardiovascular surgery using CPB.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

After induction of anesthesia, the patients were fitted with a gastric tube equipped at the tip with a CO2 sensor (ion-selective field effect transistor) that can continuously measure real-time PgCO2, and a pulmonary artery catheter capable of monitoring continuous CO (CCO) and end-tidal CO2. Data from the devices was uploaded to a personal computer every 2 mins until the catheter was pulled off based on clinical judgment (PgCO2 values were blinded to everyone except the investigator). One patient expired as a result of multiple organ failure subsequent to sepsis, and postoperative morbidity assessed by the peak SOFA (sequential organ failure assessment) score (mean +/- SD 6.9 +/- 3.5; range, 2-13) was correlated with the peak PgCO2 during intensive care unit stay (mean +/- SD 74.1 +/- 30.7 mm Hg; range, 45-169 mm Hg) (p < .01, by regression analysis). The peak PgCO2 during surgery (mean +/- SD 71.1 +/- 18.1 mm Hg; range, 44-115 mm Hg) had no correlation with the postoperative morbidity. From analysis of CCO before, during, and after returning from the above 60 mm Hg of PgCO2, PgCO2 changed independently of CCO.

CONCLUSIONS

PgCO2 changed independently of CCO, and its postoperative elevation was related to morbidity, even in the group of patients with a good outcome. Continuous monitoring of PgCO2 is useful for the detection of morbidity and can be expected to help elucidate the pathophysiology of change of PgCO2.