Intraoperative glucose administration influences respiratory quotient during paediatric anaesthesia

Validation of an alternative technique for RQ estimation in anesthetized pigs

BACKGROUND

Respiratory quotient (RQ) is an important variable when assessing metabolic status in intensive care patients. However, analysis of RQ requires cumbersome technical equipment. The aim of the current study was to examine a simplified blood gas-based method of RQ assessment, using Douglas bag measurement of RQ (Douglas-RQ) as reference in a laboratory porcine model under metabolic steady state. In addition, we aimed at establishing reference values for RQ in the same population, thereby generating data to facilitate further research.

METHODS

RQ was measured in 11 mechanically ventilated pigs under metabolic steady state using Douglas-RQ and CO-oximetry blood gas analysis of pulmonary artery and systemic carbon dioxide and oxygen content. The CO-oximetry data were used to calculate RQ (blood gas RQ). Paired recordings with both methods were made once in the morning and once in the afternoon and values obtained were analyzed for potential significant differences.

RESULTS

The average Douglas-RQ, for all data points over the whole day, was 0.97 (95%CI 0.95-0.99). The corresponding blood gas RQ was 0.95 (95%CI 0.87-1.02). There was no statistically significant difference in RQ values obtained using Douglas-RQ or blood gas RQ for all data over the whole day (P = 0.43). Bias was - 0.02 (95% limits of agreement ± 0.3). Douglas-RQ decreased during the day 1.00 (95%CI 0.97-1.03) vs 0.95 (95%CI 0.92-0.98) P < 0.001, whereas the decrease was not significant for blood gas RQ 1.02 (95%CI 0.89-1.16 vs 0.87 (0.80-0.94) P = 0.11.

CONCLUSION

RQ values obtained with blood gas analysis did not differ statistically, compared to gold standard Douglas bag RQ measurement, showing low bias but relatively large limits of agreement, when analyzed for the whole day. This indicates that a simplified blood gas-based method for RQ estimations may be used as an alternative to gold standard expired gas analysis on a group level, even if individual values may differ. In addition, RQ estimated with Douglas bag analysis of exhaled air, was 0.97 in anesthetized non-fasted pigs and decreased during prolonged anesthesia.

A mini review of dolphin carbohydrate metabolism and suggestions for future research using exhaled air

In the 1960s, I explored some aspects of carbohydrate metabolism in healthy bottlenose dolphins (Tursiops truncatus). Their physiological picture resembled what had been described for hyperthyroid diabetics. Dolphins have elevated thyroid hormone turnover, and fasting dolphins maintain a relatively high level of plasma glucose. After dolphins ingest glucose, plasma levels remain high for many hours. Interestingly, plasma glucose must exceed 300 mg/dL (about twice as high as the human threshold) before glucose appears in urine. Due to their diabetes-like states, trainability, and unique natural respiratory anatomy and physiology, dolphins may offer useful clues to metabolites in the breath that may be used to non-invasively monitor diabetes in humans. Dolphins take very rapid and deep breaths that are four or five times as deep as humans and other terrestrial mammals, making them ideal for physiological assessment using non-invasive exhaled air. Avenues for successfully identifying breath-based markers for metabolic disease and physiology in dolphins can be done with both modern technology and the evolutionarily advantageous canine nose. This review summarizes aspects of dolphin metabolism previously learned and offers new directions for diabetes research that may benefit both dolphin and human health.

A novel isotonic balanced electrolyte solution with 1% glucose for intraoperative fluid therapy in neonates: results of a prospective multicentre observational postauthorisation safety study (PASS)

BACKGROUND

Neonates have a higher metabolic rate and an increased risk of perioperative hypoglycemia and lipolysis, but during anesthesia, both oxygen consumption and metabolic rate are decreased, and this may lead to reduced intraoperative glucose requirements.

OBJECTIVE

The objective of this prospective multicentre observational postauthorisation safety study was to evaluate the intraoperative use of a novel isotonic balanced electrolyte solution with a low glucose concentration of 1% (BS-G1) in neonates with a particular focus on changes in acid-base, electrolyte, and glucose concentrations.

METHODS

Following the local ethics committee approval, neonates with a postmenstrual age under 45 weeks and an ASA risk score of I-IV undergoing intraoperative administration of BS-G1 were enrolled. Patient demographics, the performed procedure, adverse drug reactions, hemodynamic data, and the results of blood gas analysis before and after infusion were documented with a focus on changes in acid-base, electrolyte, and glucose concentrations.

RESULTS

  In 66 neonates (ASA I-IV; postmenstrual age 38 ± 4, range 25-45 weeks; body weight 2.9 ± 0.9, range 0.65-4.6 kg), the mean infusion rate was 10.4 ± 3.2 (range 4.5-19.6) ml·kg(-1) ·h(-1) BS-G1. During the infusion, hemoglobin, hematocrit, bicarbonate, base excess, anion gap, strong ion difference, and calcium decreased, and chloride and glucose increased significantly within the physiological range. All other measured parameters including sodium and lactate remained stable. Neither hypoglycemia (glucose < 3 mm) nor hyperglycemia (glucose > 10 mm) was documented after BS-G1 infusion. No adverse drug reactions were reported.

CONCLUSION

The study shows that the intraoperative use of an isotonic balanced electrolyte solution with 1% glucose and a mean infusion rate of 10 ml·kg(-1) ·h(-1) helps to avoid acid-base dysbalance, hyponatraemia, hypoglycemia, ketoacidosis, and hyperglycemia in surgical neonates. A careful intraoperative monitoring and adaptation of the infusion rate as needed is crucial because the glucose and fluid requirements may vary widely between subjects.

[Monitoring oxygen consumption in energy metabolism in pediatric anesthesia: clinical utility]

OBJECTIVES

To determine changes in oxygen consumption as a marker of energy metabolism during general inhaled anesthesia in pediatric patients and to identify factors that might influence consumption.

MATERIAL AND METHODS

Prospective, observational, double-blind study in children under inhaled anesthesia in spontaneous ventilation. We monitored heart rate electrocardiogram, noninvasive blood pressure, respiratory frequency, carbon dioxide (CO2) end-expiratory pressure, oxygen saturation by pulse oximetry, state entropy, response entropy, esophageal temperature, and (by indirect calorimetry) oxygen consumption and the respiratory quotient. Capillary blood was extracted every 5 minutes to determine lactate concentration.

RESULTS

Thirty-six patients (ASA 1-2) between 5 and 11 years old were included. Mean (SD) oxygen consumption was 0.6 (0.12) mL x kg(-1)min(-1) at baseline, 5.3 (03) mL x kg(-1) min(-1) during maintenance of anesthesia, and 8.1 (1.1) mL x kg(-1) min(-1) on awakening. A progressive increase was detected in lactic acid concentration, from a baseline mean of 0.8 (0.1) mmol/L to 2.2 (0.9) mmol/L half an hour later; the change was unrelated to oxygen consumption. After correcting the flow of normal saline solution to 0.9%, a significant increase in oxygen consumption (P < .05) was detected. Factors that were significantly correlated (P < 0.1 and r of +/- 0.95) were temperature (oxygen consumption decreased > 10% for each degree centigrade decrease), inspired oxygen fraction > 0.8; sharp changes in the expired CO2 fraction exceeding 2 standard deviations (+/- 6), use of nitrous oxide in the gas mix (inspired nitrous oxide fraction > 20%), the length of the sampling line, and increased respiratory frequency. A model with 3 factors was constructed to explain the kinetics of oxygen consumption during anesthesia.

CONCLUSIONS

Oxygen consumption monitoring may provide an indirect indicator of homeostatic changes during surgery. The ideal system for carrying out such monitoring during anesthesia remains to be found, and the values to guide the anesthesiologist in deciding whether or not to intervene immediately still need to be determined.

Peri-operative hyperglycemia: a consideration for general surgery?

BACKGROUND

Intraoperative hyperglycemia in cardiac and neurosurgical patients is significantly associated with morbidity. Little is known about the perioperative glycemic profile or its impact in other surgical populations or in nondiabetic patients.

METHODS

A systematic review of blood glucose values during major general surgical procedures reported since 1980 was conducted. Data extracted included blood glucose measures, study sample size, gender distribution, age grouping, study purpose, surgical procedure, anesthetic details, and infusion regime. Excluded studies were those with subjects with diabetes insipidus, insulin-treated diabetes, renal or hepatic failure, adrenal gland tumors or dysfunction, pregnancy, and emergency or trauma surgery.

RESULTS

Blood glucose levels rose significantly with the induction of anesthesia (P < .001) in nondiabetic patients. At incision, 2 hours, 4 hours, and 6 hours, 30%, 40%, 38%, and 40% of studies, respectively, reported hyperglycemia.

CONCLUSIONS

Factors that confound or protect against significant rises in perioperative glycemic levels in nondiabetic patients were identified. The findings facilitate investigating the impact of hyperglycemia on general surgical outcomes.