Metabolic Pattern and Lipid Oxidation During Abdominal Surgery

An improved water-soluble prodrug of propofol with high molecular utilization and rapid onset of action

Water-soluble prodrugs of propofol often carry an excess of propofol at the effective dose and have a slower onset of action. Sustained release of the original drug can result in propofol accumulation in the body after administration, causing delays in wakefulness. This situation causes the prodrug to lose the benefits of rapid onset and recovery from the effects of propofol. In the present study, HX0921 (sodium 2-(2-(2,6-diisopropylphenoxy)-2-oxoethoxy)acetate), an improved prodrug of propofol with high utilization of propofol and fast onset of action, was studied. The rate of propofol release from HX0921 was much faster than that from fospropofol (a marketed propofol prodrug) in rat plasma. The 50% effective dose (ED₅₀) of propofol, HX0921 and fospropofol to induce anesthesia in rats was 5.78, 22.19 and 42.44 mg/kg, respectively. After administration at 2 × ED₅₀, the onset time of anesthesia in the HX0921 group was significantly shorter than that in the fospropofol group (0.26 ± 0.15 min vs. 2.24 ± 0.35 min, P < 0.01) and the duration of anesthesia in the HX0921 group was also significantly shorter than that in the fospropofol group (22.35 ± 4.05 min vs. 29.15 ± 5.25 min, P < 0.01). These results suggest that the rapid onset and short action time of HX0921 was due to the rapid release and high molecular utilization of propofol carried by HX0921.

Anesthesia and bariatric surgery gut preparation alter plasma acylcarnitines reflective of mitochondrial fat and branched-chain amino acid oxidation

The period around bariatric surgery offers a unique opportunity to characterize metabolism responses to dynamic shifts in energy, gut function, and anesthesia. We analyzed plasma acylcarnitines in obese women (n = 17) sampled in the overnight fasted/postabsorptive state approximately 1-2 wk before surgery (condition A), the morning of surgery (prior restriction to a 48-h clear liquid diet coupled in some cases a standard polyethylene glycol gut evacuation: condition B), and following induction of anesthesia (condition C). Comparisons tested if 1) plasma acylcarnitine derivatives reflective of fatty acid oxidation (FAO) and xenometabolism would be significantly increased and decreased, respectively, by preoperative gut preparation/negative energy balance (condition A vs. B), and 2) anesthesia would acutely depress markers of FAO. Acylcarnitines associated with fat mobilization and FAO were significantly increased in condition B: long-chain acylcarnitines (i.e., C18:1, ~70%), metabolites from active but incomplete FAO [i.e., C14:1 (161%) and C14:2 (102%)] and medium- to short-chain acylcarnitines [i.e., C2 (91%), R-3-hydroxybutyryl-(245%), C6 (45%), and cis-3,4-methylene-heptanoyl-(17%), etc.]. Branched-chain amino acid markers displayed disparate patterns [i.e., isobutyryl-(40% decreased) vs. isovaleryl carnitine (51% increased)]. Anesthesia reduced virtually every acylcarnitine. These results are consistent with a fasting-type metabolic phenotype coincident with the presurgical "gut preparation" phase of bariatric surgery, and a major and rapid alteration of both fat and amino acid metabolism with onset of anesthesia. Whether presurgical or anesthesia-associated metabolic shifts in carnitine and fuel metabolism impact patient outcomes or surgical risks remains to be evaluated experimentally.

Absorption of carbon dioxide during laparoscopy in children measured using a novel mass spectrometric technique

BACKGROUND

Carbon dioxide (CO(2)) is absorbed during pneumoperitoneum and may cause adverse haemodynamic effects. The aim of this study was to measure the elimination of exogenous CO(2) during laparoscopy in children.

METHODS

Ten children [27.6 (56.5) months; mean (SD)] undergoing laparoscopic and nine [24.5 (17.3) months] undergoing open surgery were studied. Breath samples were collected at the line for end-tidal CO(2) and analysed for (13)CO(2)/(12)CO(2) ratio expressed as deltaPDB (difference from standard), by isotope-ratio mass spectrometry. The proportion of absorbed CO(2) was calculated comparing exhaled (13)CO(2)/(12)CO(2) before and during CO(2) pneumoperitoneum.

RESULTS

(13)CO(2)/(12)CO(2) in medical CO(2) was -32.7 (2.1) deltaPDB. (13)CO(2)/(12)CO(2) in breath of patients undergoing open procedures was -24.3 (2.4) deltaPDB at the start of operation and did not change during the operation (P > 0.2). (13)CO(2)/(12)CO(2) in breath of patients undergoing laparoscopy was -21.5 (5.4) deltaPDB at the start of insufflation, and decreased during pneumoperitoneum by 2.5 (1.6) deltaPDB, indicating absorption of exogenous CO(2). The percentage of expired CO(2) absorbed rose to 15.5 (7.7)% after 30 min of pneumoperitoneum and decreased rapidly after desufflation.

CONCLUSION

After 10 min of laparoscopy 10-20% of expired CO(2) derives from the exogenous CO(2). CO(2) absorption can be measured using a simple mass spectrometric technique.

Ventilation and metabolism during propofol anesthesia in rats

Many anesthetics are known to decrease ventilation (V(E)) and metabolic rate (MR). Because MR is known to contribute to the V(E) level, one would expect some parallelism between the changes in V(E) and MR during anesthesia. We tested this hypothesis in normoxia and hypoxia (12% O2) on male Wistar rats (n = 10; 221-288 g) by using a short-acting intravenous anesthetic, propofol. Propofol anesthesia was induced with a 7-7.5 mg kg(-1) (60-70 s) dose and maintained with a 20-22 mg kg(-1) h(-1) (<40 min) dose. In normoxia, propofol significantly decreased V(E) and MR and maintained the V(E)/MR ratio. In hypoxia, propofol decreased MR without a significant decrease in V(E), and the V(E)/MR ratio tended to increase. As a result, both in normoxia and hypoxia, propofol did not significantly increase the partial pressure of CO2 in arterial blood (PaCO2). Propofol was also associated with decreased body temperature and mean arterial pressure. The results suggest that during anesthesia, a large part of the drop in V(E) can be accounted for by the drop in MR, and that in both normoxia and hypoxia the V(E)/MR ratios and PaCO2values are maintained close to the levels of the conscious state.