Gastric hypercarbia and adverse outcome after cardiac surgery

[Gastrointestinal complications after on-pump cardiac surgery]

OBJECTIVE

To determine the incidence and independent predictors of gastrointestinal complications (GICs) following on-pump cardiac surgery.

MATERIAL AND METHODS

We retrospectively analyzed data of 9559 adults who underwent cardiac surgery in 2012-2017. Two groups of patients were distinguished: group 1 - 47 (0.5%) patients with abdominal complications followed by urgent surgery; group 2 - 9512 (95.5%) patients without complications or effective therapy.

CONCLUSION

1. Predictors of gastrointestinal complications: age >65 years, previous AF (p=0.011) and multifocal atherosclerosis (p=0.016), LV EF <40% (p=0.039), aortic cross-clamping time > 90 min (p=0.021), intraoperative blood loss over 600 ml (p=0.002), postoperative serum creatinine >140 μmol/l (p=0.005), mechanical ventilation >24 hours (p=0.023).

2. Reduced hemodilution during CPB, warm blood cardioplegia, higher perioperative values of Hb, Ht and IDO2 during cardiopulmonary bypass can prevent ischemic injury of abdominal organs during prolonged cardiac surgery.

Monitoring devices in the intensive care unit

Monitors in the intensive care unit are imperative to taking adequate care of these critically ill patients. Cardiovascular, pulmonary, and neurologic monitors are key to performing these tasks. This article gives an overview of the most common monitors that are used in the intensive care unit.

Correlation of abdominal site near-infrared spectroscopy with gastric tonometry in infants following surgery for congenital heart disease

OBJECTIVE

Splanchnic oximetry, as measured by near-infrared spectroscopy (NIRS), correlates with gastric tonometry as a means of assessing regional (splanchnic) oxygenation and perfusion.

DESIGN

Prospective, data-gathering study.

SETTING

Pediatric cardiac intensive care unit in a tertiary care children's hospital.

SUBJECTS

Neonates and infants with congenital heart disease who underwent catheter intervention or surgical repair requiring cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Twenty neonates and infants were studied within 48 hrs of surgery. We measured somatic saturation (rSO2) via NIRS sensors placed over the anterior abdomen (splanchnic bed) and dorsal lateral flank (renal bed). Somatic rSO2 readings were paired with simultaneous points of intramucosal gastric pH (pHi), measured by tonometry. The rSO2 readings were paired with serum lactate and measurements of systemic mixed venous saturation (SVO2). There was strong correlation between the abdominal rSO2 and pHi (r = .79; p < .0001) as well as between abdominal rSO2 and SVO2 (r = .89; p < .0001). There was also significant negative correlation between the abdominal rSO2 and serum lactate (r = .77; p < .0001). Correlations between the dorsal lateral (renal) rSO2 measurements and serum lactate and SVO2 were also significant but not as strong.

CONCLUSIONS

Abdominal site rSO2, measured in infants with either single or biventricular physiology, exhibits a strong correlation with gastric pHi as well as with serum lactate and SVO2. The results indicate that rSO2 measurements over the anterior abdominal wall correlate more strongly than flank rSO2 with regard to systemic indices of oxygenation and perfusion. This study suggests that the NIRS monitor is a valid modality to obtain an easy, immediate, and noninvasive measurement of splanchnic rSO2 in infants following cardiac surgery for congenital heart disease.

Monitoring oxygen transport and tissue oxygenation

PURPOSE OF REVIEW

To review recent publications in the field of oxygen delivery and tissue oxygenation. With few exceptions, we restricted our selection to clinical studies published in the English literature.

RECENT FINDINGS

No major breakthroughs have occurred in the past decade in the diagnosis or treatment of tissue hypoxia. There is renewed interest in goal-directed resuscitation when applied early in the course of treatment. Monitoring metabolic markers of tissue hypoxia continues to hold great clinical interest, in particular, tissue PCO2, near infrared spectroscopy, base deficit and blood lactate concentration. Technical issues, however, seem to restrict the widespread use of many of these techniques.

SUMMARY

There is an urgent need to develop methods to accurately and rapidly identify patients with tissue hypoxia. Perhaps the combination of gastric tonometry, near-infrared spectroscopy, urinary PO2 and continuous measures of mixed (or central) venous O2 saturation may provide the answer. An even more formidable task is that of developing effective therapy to correct tissue hypoxia while avoiding harm to the patient.

Rectal lactate levels in endoluminal microdialysate during routine coronary surgery

The aim of this prospective study was to determine the feasibility of intestinal endoluminal microdialysis as a new method for clinical monitoring of the adequacy of splanchnic perfusion in the large bowel. A microdialysis catheter for continuous lactate, glycerol, glucose and pyruvate measurements attached to a tonometric catheter was placed into the lumen of the recto-sigmoid junction prior to surgery in 13 patients undergoing elective cardiac surgery with cardiopulmonary bypass (CPB). Lactate was also measured in blood and muscle. CPB was associated with a 10-fold increase in luminal lactate from 0.16 (0.01) to 1.67 (0.38) mmol x l(-1) (p < 0.001). Muscular lactate increased from baseline levels 1.20 (0.21) to 1.77 (0.36) mmol x l(-1) during CPB (p = 0.01), but the muscular lactate-pyruvate ratio remained unchanged. Arterial lactate increased only slightly from 0.9 (0.05) to 1.1 (0.06) mmol x l(-1) (p = 0.027) during CPB. Increased lactate concentrations in the large bowel during CPB are suggestive of local lactate production consistent with impaired oxygen delivery. Intestinal endoluminal microdialysis is a potential clinically applicable method for monitoring intestinal metabolism. Combined with tonometry, microdialysis provides the opportunity to monitor both circulation and metabolism in the rectal mucosa.

Effects of intra-aortic balloon counterpulsation on parameters of tissue oxygenation

BACKGROUND AND OBJECTIVE

To investigate the effects of intra-aortic balloon pump therapy on parameters of global and regional oxygenation in patients undergoing cardiac surgery.

METHODS

As part of a large surveillance study in cardiac surgery patients (n=266) we retrospectively analyzed the course of 28 patients requiring intra-aortic balloon pump therapy. Patients were grouped according to the time point of pump insertion (during weaning from cardiopulmonary bypass: group early intra-aortic balloon pumping (n=17); after admission to the intensive care unit: group late intra-aortic balloon pumping (n=9). Haemodynamic and tonometric variables, arterial lactate, and use of catecholamines were measured hourly.

MEASUREMENTS AND RESULTS

Cardiac index increased in both groups after intra-aortic balloon pump insertion (2.2+/-0.5 baseline; 3.4+/-0.8 L min-1 m-2 4 h later (group early intra-aortic balloon pumping); 2.8+/-0.5 baseline, 3.6+/-L min-1 m-2 4 h later (group later intra-aortic balloon pumping), each P<0.05), there were no differences between groups. Arterial lactate values increased in group later intra-aortic balloon pumping after pump insertion to a maximum 2 h later (8.4+/-6.1 mmol L-1 baseline; 12.7+/-7.4 mmol L-1, P<0.05), and decreased continuously afterwards. The difference of arterial and gastric CO2 showed a sharp decrease after pump insertion in group later intra-aortic balloon pumping (26.4+/-9.8 baseline; 7.0+/-11.1 mmHg, P<0.05). There were no differences between groups. Epinephrine doses were higher in group later intra-aortic balloon pumping (P<0.05).

CONCLUSIONS

Intra-aortic balloon pump therapy improved global and regional splanchnic oxygenation in cardiac surgery patients with low-cardiac-output syndrome. Gastro-intestinal tonometry could provide additional information concerning tissue oxygenation. Patients with later intra-aortic balloon pump insertion needed more catecholamine therapy to achieve similar haemodynamic values.

Increased concentrations of l -lactate in the rectal lumen in patients undergoing cardiopulmonary bypass †

BACKGROUND

Gut ischaemia may contribute to morbidity in patients after cardiopulmonary bypass (CPB), but little is known about the metabolic state of the large bowel in such patients. Therefore we estimated the concentrations of L-lactate and Pco(2) in rectal mucosa in patients undergoing cardiac surgery with or without the use of CPB.

METHODS

Patients undergoing coronary artery bypass grafting (CABG) (n=12) or off-pump CABG (n=10) were subjected to equilibrium dialysis of the rectal lumen during the procedure and in the first 4 h afterwards. Dialysate concentrations of L-lactate and Pco(2) were measured using an auto-analyser and compared with values obtained in healthy subjects (n=10).

RESULTS

During CPB, a 2- to 3-fold increase in luminal concentrations of L-lactate was observed (CABG vs off-pump CABG, P=0.05; CABG vs healthy subjects, P<0.01). The dialysate concentrations of L-lactate were higher than the mean systemic values (luminal-arterial gradient mean (sd) 0.9 (1.0) mmol litre(-1), P<0.05), and the two values were positively correlated (P<0.05). Luminal L-lactate concentrations remained elevated 4 h after the operation. In contrast, dialysate Pco(2) was equally high in patient and control groups and substantially higher than values observed in arterial blood.

CONCLUSIONS

Uncomplicated CPB is associated with moderate but sustained increases in luminal concentrations of L-lactate in the rectum, indicating metabolic dysfunction of the mucosa in the large bowel.

Abdominal organ injury after cardiac surgery

Gastrointestinal complications occur in about 2.5% of patients undergoing cardiac surgery, are associated with a high mortality (about 33%), and account for nearly 15% (and perhaps increasing) of all postoperative deaths. The various complications and risk factors are reviewed. Splanchnic ischemia prior to, during, and especially postoperatively appears to be an important cause of these complications. In addition, splanchnic ischemia is hypothesized to be one cause of the systemic inflammatory response syndrome and multiorgan failure that may follow cardiac surgery. The physiology of splanchic perfusion and the effects of cardiac surgery, including cardiopulmonary bypass, on it are reviewed. Finally, possible methods to minimize splanchnic ischemia and reduce the incidence of abdominal complications are discussed.