Complement activation by propofol and its effect during propofol anaesthesia

The Impact of General Anesthesia on Redox Stability and Epigenetic Inflammation Pathways: Crosstalk on Perioperative Antioxidant Therapy

Worldwide, the prevalence of surgery under general anesthesia has significantly increased, both because of modern anesthetic and pain-control techniques and because of better diagnosis and the increased complexity of surgical techniques. Apart from developing new concepts in the surgical field, researchers and clinicians are now working on minimizing the impact of surgical trauma and offering minimal invasive procedures due to the recent discoveries in the field of cellular and molecular mechanisms that have revealed a systemic inflammatory and pro-oxidative impact not only in the perioperative period but also in the long term, contributing to more difficult recovery, increased morbidity and mortality, and a negative financial impact. Detailed molecular and cellular analysis has shown an overproduction of inflammatory and pro-oxidative species, responsible for augmenting the systemic inflammatory status and making postoperative recovery more difficult. Moreover, there are a series of changes in certain epigenetic structures, the most important being the microRNAs. This review describes the most important molecular and cellular mechanisms that impact the surgical patient undergoing general anesthesia, and it presents a series of antioxidant therapies that can reduce systemic inflammation.

Immune Function following Major Spinal Surgery and General Anesthesia

There are reported differences in the effects that general anesthetics may have on immune function after minor surgery. To date, there are no prospective trials comparing total intravenous anesthesia (TIVA) with a volatile agent-based technique and its effects on immune function after major spinal surgery in adolescents. Twenty-six adolescents undergoing spinal fusion were randomized to receive TIVA with propofol-remifentanil or a volatile agent-based technique with desflurane-remifentanil. Immune function measures were based on the antigen-presenting and cytokine production capacity, and relative proportions of cell populations. Overall characteristics of the two groups did not differ in terms of perioperative times, hemodynamics, or fluid shifts, but those treated with propofol had lower bispectral index values. Experimental groups had relatively high baseline interleukin-10 values, but both showed a significant inflammatory response with similar changes in their respective immune functions. This included a shift toward a granulocytic predominance; a transient reduction in monocyte markers with significant decrease in antigen-presenting capacity and cytokine production capacity. Anesthetic choice does not appear to differentially impact immune function, but exposure to anesthetics and surgical trauma results in reproducibly measurable suppression of both innate and adaptive immunity in adolescents undergoing posterior spinal fusion. The magnitude of this suppression was modest when compared with pediatric and adult patients with critical illnesses. This study highlighted the need to evaluate immune function in a broader population of surgical patients with higher severity of illness.

Alternative pathway activation of complement in laparoscopic and open rectal surgery

The study was designed to investigate whether complement is activated in patients subject to rectal surgery and whether the choice of surgical technique (open or laparoscopic) has any impact on the activation of complement. Our hypothesis is that laparoscopic surgery leads to a lower-level activation of complement than open surgery. Patients (n = 24) subject to rectal surgery owing to rectal cancer were included. The study was prospective and randomized. The patients were randomized to either laparoscopic surgery (n = 12) or open surgery (n = 12). Blood samples for determination of complement activation (C4d, Bb, C3bc and the terminal C5b-9 complex TCC) were drawn before start of surgery (T0) and at the following time-points after start of surgery: 180 min (T1), 360 min (T2), 24 h (T3) and 3-5 days (T4). A significant increase in the alternative pathway activation product Bb and in the terminal pathway activation product TCC was seen over time in both groups (P < 0.001). Bb peaked early (T1) and returned to baseline levels post-operatively, whereas TCC increased steadily with maximum values in the late post-operative period. The plasma concentrations of C4d and C3bc decreased significantly in both groups at T1 and T2 and returned to baseline levels at T4. There was no significant difference between the groups. Rectal surgery causes activation of the complement system. Complement is activated through the alternative pathway. Results mostly showed no significant differences between laparoscopic and open rectal surgery apart from lower levels of factor Bb in the former group in the perioperative period.

Complement activation and interleukin response in major abdominal surgery

The objective of this study was to evaluate whether major abdominal surgery leads to complement activation and interleukin response and whether the kind of anaesthesia influence complement activation and the release of inflammatory interleukins. The study design was prospective and randomised. Fifty patients undergoing open major colorectal surgery due to cancer disease or inflammatory bowel disease were studied. Twenty-five patients were given total intravenous anaesthesia (TIVA) with propofol and remifentanil, and 25 patients were given inhalational anaesthesia with sevoflurane and fentanyl. To determine complement activation (C3a and SC5b-9) and the release of pro- and anti-inflammatory interleukins (tumour necrosis factor-a (TNF-a)), interleukin-1b (IL-1b), IL-6, IL-8, IL-4 and IL-10), blood samples were drawn preoperatively, 60 minutes after start of surgery, 30 minutes after end of surgery and 24 hours postoperatively. Complement was activated and pro-inflammatory interleukins (IL-6 and IL-8) and anti-inflammatory interleukins (IL-10) were released during major colorectal surgery. There was no significant difference between TIVA and inhalational anaesthesia regarding complement activation and cytokine release. Major colorectal surgery leads to activation of the complement cascade and the release of both pro-inflammatory and anti-inflammatory cytokines. There are no significant differences between total intravenous anaesthesia (TIVA) with propofol and remifentanil and inhalational anaesthesia with sevoflurane and fentanyl regarding complement activation and the release of pro- and anti-inflammatory interleukins.

The management of Cesarean delivery in a parturient with paroxysmal nocturnal hemoglobinuria complicated by severe preeclampsia

PURPOSE

To describe the anesthetic and peripartum management of a parturient with paroxysmal nocturnal hemoglobinuria complicated by severe preeclampsia, review the pathophysiology of this condition, rationale for thromboembolic prophylaxis, and its implications on the choice of labour analgesia and anesthesia.

CLINICAL FEATURES

A 35-yr-old primigravida was diagnosed with paroxysmal nocturnal hemoglobinuria at 18 weeks gestation following new onset pancytopenia. Venous thromboembolic prophylaxis with low molecular weight heparin (LMWH) was started, and continued despite a persistent thrombocytopenia. At 34 weeks, labour was induced after she developed signs of severe preeclampsia, and intravenous magnesium sulfate therapy was commenced. The use of a twice daily dosing regime of LMWH, along with severe thrombocytopenia contraindicated neuraxial anesthesia. As a result, labour analgesia was provided with an intravenous patient-controlled analgesia system with fentanyl. The patient subsequently had an uneventful Cesarean delivery under general anesthesia. Anticoagulation with LMWH was restarted postoperatively, and continued for six weeks postpartum. She was discharged home on day 20 postpartum, on oral prednisolone under the care of the hematologists.

CONCLUSION

Paroxysmal nocturnal hemoglobinuria is associated with an increased risk of venous thromboembolism, and so anticoagulation therapy assumes primary importance. The use of LMWH for prophylaxis in combination with thrombocytopenia may contraindicate neuraxial anesthesia. General anesthesia should be aimed at preventing or exacerbating complement mediated intravascular hemolysis.

Mechanism of injection pain with long and longmedium chain triglyceride emulsive propofol

PURPOSE

t has been suggested that long-medium chain triglyceride (LCT/MCT) emulsive propofol causes less injection pain than long chain triglyceride (LCT) emulsive propofol because of the decreased propofol concentration in the aqueous phase. Alternatively, LCT propofol generates bradykinin causing the injection pain and activates complement, but these effects when using LCT/MCT propofol have not been examined. To identify the mechanism for reduced pain with LCT/MCT propofol, injection pain, bradykinin generation and complement activation with use of both propofol products were compared.

METHODS

Two hundred adult patients randomly allocated to two groups were given 1.5 mg x kg(-1) iv of either LCT propofol or LCT/MCT propofol at a rate of 200 mg x min(-1) in a double-blind manner and were asked to grade pain scores. In another study, bradykinin and activated complement 3 (C3a) concentrations were measured using blood obtained from 13 healthy volunteers mixed with saline, LCT propofol or LCT/MCT propofol.

RESULTS

There was a significant difference in pain scores between groups, showing a lower incidence of injection pain in the LCT/MCT propofol group. The bradykinin concentrations in blood mixed with LCT and LCT/MCT propofol were significantly higher than in blood mixed with saline. The C3a concentrations showed similar results.

CONCLUSIONS

LCT/MCT propofol causes less pain on injection compared with LCT propofol. Bradykinin generation and complement activation are similar with both LCT and LCT/MCT propofol. Thus, the reason for less pain on injection with LCT/MCT propofol may be attributed to a decreased concentration of propofol in the aqueous phase.

Impact of Inverse Plasma Filtration on Complement Activation in Porcine Blood

During extracorporeal circulation, activation of the complement system as a bioincompatibility reaction upon contact with artificial surfaces is well known. This may induce adverse effects for the patient as well as for the bioreactor when using a hybrid liver support system. At present, the achievable clearance rates in hybrid liver support systems are restricted by the limitations of blood flow through the capillaries of the plasma filter. In order to enhance clearance rates it is desirable to develop a high-flow plasma separation unit in which the activation of the complement system is as low as possible. Conventional plasma filters operating in normal and in inverse (blood flow around the capillaries and the capillary lumen serving as plasma compartment) modes were investigated applying an in vitro circuit (n = 4 in each group). For this purpose heparinized porcine blood was used. Complement activation was measured as generation of the soluble membrane attack complex, SC5b-9. With a normal flow mode the maximum achievable filtration rates varied from 25 to 40 mL/min, whereas the maximal filtration rates with an inverse flow mode varied from 40 to 100 mL/min. While these values were significantly higher than those with regularly operating plasma filters, there was no significant difference between normal and inverse mode in the production of SC5b-9. We conclude that the outer surface of the investigated conventional plasma filtration membranes is suitable for an inverse mode and does not lead to an excessive activation of the complement system upon dynamic blood contact. Thus, the inversion of the blood and the plasma compartments may be a possible way forward in the development of a high-flow plasma separation filter.

Effects of general anaesthesia on inflammation

General anaesthesia accompanied by surgical stress may influence the inflammatory responses that are essential for maintaining the homeostatic state during the postoperative course. Severe dysregulation of the inflammatory process may provoke or aggravate postoperative complications, e.g. increased susceptibility to infections, inadequate stress reactions and hypercatabolism. Anaesthetics have been suspected of impairing various functions of the immune system either directly, by disturbing the functions of immune-competent cells, or indirectly by modulating the stress response. In the past, conflicting data on the possible immunological side effects of anaesthetics have been published. Potential reasons for these controversial findings include heterogeneous patient study groups with diverse pre-existing diseases, lack of standardisation of surgical procedures, major differences in the length and severity of surgical tissue injury and a small number of randomised studies. Although the immunological effects are of minor consequence in subjects with normal immune functions, the suppression of cellular and humoral immunity following surgery and general anaesthesia may be relevant in patients with pre-existing immune disorders.