Propofol emulsion reduces proliferative responses of lymphocytes from intensive care patients

Immunomodulators in anesthesia

PURPOSE OF REVIEW

Anesthetics are known to have immunomodulatory effects. These can be detrimental, inducing immunosuppression and facilitating the development of opportunistic infections, especially when used at high doses, for prolonged periods, or in patients with preexisting immune deficiency; or beneficial, modulating the inflammatory response, particularly in critical illness and systemic hyperinflammatory states.

RECENT FINDINGS

Anesthetics can have microbicidal properties, and both anti- and pro-inflammatory effects. They can act directly on immune cells as well as modulate immunity through indirect pathways, acting on the neuroimmune stress response, and have recently been described to interact with the gut microbiota.

SUMMARY

Anesthesiologists should take into consideration the immunomodulatory properties of anesthetic agents in addition to their hemodynamic, neuroprotective, and other impacts. In future, patient stratification according to the perioperative assessment of serum biomarkers associated with postoperative complications may be used to guide anesthetic agent selection based on their immunomodulatory properties.

Low dose of methylprednisolone for pain and immune function after thoracic surgery

BACKGROUND

The purpose of this study was to evaluate the effects of single low-dose preoperative methylprednisolone (MP) on the immunological function and postoperative pain of patients undergoing elective video-assisted thoracoscopic surgery under general anesthesia.

METHODS

Eighty-one patients who underwent elective video-assisted thoracoscopic surgery were randomly assigned to the MP Group or the Control Group. The T lymphocyte subsets of CD3⁺, CD4⁺, and CD8⁺, the CD4⁺/CD8⁺ ratio at T₀ (before anesthesia), T₁ (after surgery), and T₂ (24 h after surgery) were all recorded. Postoperative rest and cough pain scores, as well as postoperative adverse effects and surgery complications were also recorded.

RESULTS

Compared to T0, the levels of CD3⁺ and CD4⁺ subsets and CD4⁺/CD8⁺ were significantly decreased, the level of CD8⁺ were increased after surgery in both groups. There was no significant difference in the variation of CD3+, CD4+, CD8⁺, and CD4+/CD8+ between the MP Group and the Control Group. Both the rest and cough pain of patients in the MP Group were significantly lower as compared to the Control Group at 2, 4, 6 and 24 hours after surgery. And the incidences of nausea and vomiting and dizziness were also significantly higher in the Control Group than those in the MP Group.

CONCLUSIONS

Preoperative single low-dose of MP (1 mg/kg) has no effect on immune function. Preoperative single low dose of MP (1 mg/kg) had effective analgesic effects and could reduce the incidence of dizziness and postoperative nausea and vomiting.

A Critical Appraisal of the Effects of Anesthetics on Immune-system Modulation in Critically Ill Patients With COVID-19

Purpose

The aim of the present article was to briefly summarize current knowledge about the immunomodulatory effects of general anesthetics and the possible clinical effects of this immunomodulation in patients with COVID-19.

Methods

The PubMed, Scopus, and Google Scholar databases were comprehensively searched for relevant studies.

Findings

The novel coronavirus causes a wide spectrum of clinical manifestations, with a large absolute number of patients experiencing severe pneumonia and rapid progression to acute respiratory distress syndrome and multiple organ failure. In these patients, the equilibrium of the inflammatory response is a major determinant of survival. The impact of anesthetics on immune-system modulation may vary and includes both pro-inflammatory and anti-inflammatory effects.

Implications

Inhibition of the development of severe inflammation and/or the enhancement of inflammation resolution by anesthetics may limit organ damage and improve outcomes in patients with COVID-19.

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.

Isoflurane decreases interleukin-2 production by increasing c-Cbl and Cbl-b expression in rat peripheral blood mononuclear cells

Objective

To evaluate how isoflurane affects T-cell function by assaying interleukin (IL)-2 production and the expression of two Casitas B-lineage lymphoma (Cbl) family proto-oncogenes (c-Cbl and Cbl-b) in rat peripheral blood mononuclear cells (PBMCs).

Methods

Adult male Sprague–Dawley rats were randomly allocated to those that underwent blood collection after brief isoflurane anesthesia (control group), immediately after 4 hours of isoflurane general anesthesia (4I group), and 1 day after 4 hours of isoflurane general anesthesia (1D 4I group). IL-1, IL-2, and IL-6 mRNA levels and c-Cbl and Cbl-b levels in PBMCs were determined by polymerase chain reaction. Ubiquitination of protein kinase Cθ (PKCθ) and phospholipase C-γ1 (PLC-γ1) in PBMCs was assessed by immunoprecipitation.

Results

The IL-2 mRNA level in rat PBMCs was significantly lower in the 4I and 1D 4I groups than in the control group. c-Cbl, Cbl-b, and ubiquitin expression was significantly increased and zeta-chain-associated protein kinase 70, PLC-γ1, and PKCθ protein levels were significantly decreased in the 4I group. Ubiquitination of PLC-γ1 and PKCθ was significantly increased in the 4I group.

Conclusion

Isoflurane influences ubiquitin, c-Cbl, and Cbl-b expression in rat PBMCs, indicating suppression of receptor tyrosine kinase signaling pathways. These results suggest that isoflurane suppresses T-cell function.

Does Propofol Sedation Contribute to Overall Energy Provision in Mechanically Ventilated Critically Ill Adults? A Retrospective Observational Study

BACKGROUND

Propofol sedation is common in critically ill patients, providing energy of 1.1 kcal/mL when administered as a 1% solution. We aimed to determine the proportion of energy administered as propofol on days 1-5 in the intensive care unit (ICU) and any association with outcomes.

METHODS

Retrospective observational study in a quaternary ICU from January-December 2012. Inclusion criteria were length of stay (LOS) ≥5 days, age ≥18 years, and provision of mechanical ventilation (MV) for ≥5 days. Outcome measures included proportion of total daily energy provided as propofol, overall energy balance, hospital mortality, duration of MV, and ICU LOS.

RESULTS

Data from 370 patients were analyzed, 87.8% (n = 325) of whom received propofol during days 1-5 in ICU. A median [interquartile range (IQR)] of 119 [50-730] kcal was provided as propofol per patient-day. Proportion of energy provided by propofol as a percentage of total energy delivered was 55.4%, 15.4%, 9.3%, 7.9%, and 9.9% days 1-5, respectively. Patients administered propofol received a greater proportion of their total daily energy prescription compared with those who were not (P < .01). Proportion of energy provided as propofol was not significantly different based on hospital mortality (P = .62), duration of MV (P = .50), or ICU LOS (P = .15).

CONCLUSION

Propofol contributes to overall energy intake on days 1-5 of ICU admission. Energy balance was higher in those receiving propofol. No association was found between the proportion of energy delivered as propofol and outcomes.

Anti-inflammatory properties of anesthetic agents

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2017. Other selected articles can be found online at http://ccforum.com/series/annualupdate2017. Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901.

The Effects of Perioperative Anesthesia and Analgesia on Immune Function in Patients Undergoing Breast Cancer Resection: A Prospective Randomized Study

Introduction: Perioperative anesthesia and analgesia exacerbate immunosuppression in immunocompromised cancer patients. The natural killer (NK) cell is a critical part of anti-tumor immunity. We compared the effects of two different anesthesia and analgesia methods on the NK cell cytotoxicity (NKCC) in patients undergoing breast cancer surgery. Methods: Fifty patients undergoing breast cancer resection were randomly assigned to receive propofol-remifentanil anesthesia with postoperative ketorolac analgesia (Propofol-ketorolac groups) or sevoflurane-remifentanil anesthesia with postoperative fentanyl analgesia (Sevoflurane-fentanyl group). The primary outcome was NKCC, which was measured before and 24 h after surgery. Post-surgical pain scores and inflammatory responses measured by white blood cell, neutrophil, and lymphocyte counts were assessed. Cancer recurrence or metastasis was evaluated with ultrasound and whole body bone scan every 6 months for 2 years after surgery. Results: The baseline NKCC (%) was comparable between the two groups (P = 0.082). Compared with the baseline value, NKCC (%) increased in the Propofol-ketorolac group [15.2 (3.2) to 20.1 (3.5), P = 0.048], whereas it decreased in the Sevoflurane-fentanyl group [19.5 (2.8) to 16.4 (1.9), P = 0.032]. The change of NKCC over time was significantly different between the groups (P = 0.048). Pain scores during 48 h after surgery and post-surgical inflammatory responses were comparable between the groups. One patient in the Sevoflurane-fentanyl group had recurrence in the contralateral breast and no metastasis was found in either group. Conclusions: Propofol anesthesia with postoperative ketorolac analgesia demonstrated a favorable impact on immune function by preserving NKCC compared with sevoflurane anesthesia and postoperative fentanyl analgesia in patients undergoing breast cancer surgery.

Immunological modifications induced from products used during the perioperative period

Anesthetics and other products used during the perioperative period may influence immune function not only merely by reducing the HPA-axis stress response but also by directly modulating innate and adaptive immune responses. Most of the literature on the immune effects of anesthetics has been derived from in vitro or animal studies, due to the number of confounding variables in real life surgical settings. These immunosuppressive effects might not normally have clinical consequences for an immune-competent patient, but may act as important modifiers in postoperative morbidity and mortality. Furthermore, some inhibitory effects on neutrophil functions may provide a therapeutically beneficial effect under specific surgical clinical conditions, such as ischemia-reperfusion injury.

Anesthetics, immune cells, and immune responses

General anesthesia accompanied by surgical stress is considered to suppress immunity, presumably by directly affecting the immune system or activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Along with stress such as surgery, blood transfusion, hypothermia, hyperglycemia, and postoperative pain, anesthetics per se are associated with suppressed immunity during perioperative periods because every anesthetic has direct suppressive effects on cellular and neurohumoral immunity through influencing the functions of immunocompetent cells and inflammatory mediator gene expression and secretion. Particularly in cancer patients, immunosuppression attributable to anesthetics, such as the dysfunction of natural killer cells and lymphocytes, may accelerate the growth and metastases of residual malignant cells, thereby worsening prognoses. Alternatively, the anti-inflammatory effects of anesthetics may be beneficial in distinct situations involving ischemia and reperfusion injury or the systemic inflammatory response syndrome (SIRS). Clinical anesthesiologists should select anesthetics and choose anesthetic methods with careful consideration of the clinical situation and the immune status of critically ill patients, in regard to long-term mortality, morbidity, and the optimal prognosis.

Effects of different anaesthetic agents on immune cell function in vitro

BACKGROUND AND OBJECTIVE

Anaesthesia may affect the regulatory balance of postoperative immune response. The aim of this study was to investigate the effects of different volatile and non-volatile anaesthetic agents and particularly of clinically used agent combinations on the proliferation capacity and cytokine production of immune cells.

METHODS

Peripheral blood mononuclear cells from healthy donors were PHA-activated in the presence or absence of various concentrations of thiopental, propofol, fentanyl, sufentanil, sevoflurane, nitrous oxide and combinations of these anaesthetics. Cell proliferation was assessed by tritiated thymidine uptake. Interleukin-2 production and release of the soluble IL-2 receptor were determined by enzyme immunoassays and used as measures of lymphocyte activation.

RESULTS

Thiopental inhibited cell proliferation in a dose dependent manner (P < 0.001) and reduced sIL-2R release (2090-970 microg mL(-1); P < 0.05). Propofol reduced sIL-2R release at the high concentration of 10 microg mL(-1) (2220 pg mL(-1) 1780 microg mL(-1); p < 0.05). Fentanyl and sufentanil did not compensate for or enhance the inhibitory effects of thiopental. Nitrous oxide, but not sevoflurane, reduced the proliferation of human peripheral blood mononuclear cells (P < 0.05). In combinations with thiopental or nitrous oxide, sevoflurane compensated the inhibitory effects of these two agents. Fentanyl, sufentanil, sevoflurane and nitrous oxide did not affect PHA-induced IL-2 and sIL-2 receptor release by human peripheral blood mononuclear cells.

CONCLUSION

Thiopental and nitrous oxide have immunosuppressive activity. In contrast, sevoflurane may have a beneficial effect by alleviating the immunosuppressive effects of both substances.

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.

The immunomodulatory effects of prolonged intravenous infusion of propofol versus midazolam in critically ill surgical patients

Both propofol and midazolam are known to inhibit immune function. The aim of this study was to investigate cytokine production in critically ill surgical patients as early markers of immune response to prolonged infusion of propofol and midazolam. The study enrolled 40 elective patients who were to receive long-term sedation for more than 2 days. Patients were randomly allocated to one of two equally sized groups. Central venous blood samples for measurement of interleukin-1beta (IL-1beta), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were drawn prior to the start and after 48 h of infusion. After 48 h, propofol caused significant increases in IL-1beta (24%), IL-6 (23%) and TNF-alpha (4.8 times) levels, while midazolam caused significant decreases in IL-1beta (21%), IL-6 (21%) and TNF-alpha (19%). Both agents caused significant decreases in IL-8 levels (propofol: 30%, midazolam: 48%, p < 0.05). Propofol caused significant decreases in IL-2 levels (68%, p < 0.001) but increases in IFN-gamma (30%, p < 0.05), whereas there was no significant change with midazolam compared with the pre-infusion level. In conclusion, during 48 h of continuous infusion, propofol stimulated, while midazolam suppressed, the production of the pro-inflammatory cytokines IL-1beta, IL-6 and TNF-alpha, and both caused suppression of IL-8 production. Propofol inhibited IL-2 production and stimulated IFN-gamma production, whereas midazolam failed to do so. Therefore, sedative agents may have clinical implications in high-risk and immunocompromised patients.

Effects of anaesthesia on the human immune system

The ability of certain anaesthetic agents to influence the immune response has been recognized for almost 30 years. The purpose of this review is to briefly describe the different components of the immune system and examine the way in which surgery and anaesthesia influence these.

Spinal but not general anesthesia increases the ratio of T helper 1 to T helper 2 cell subsets in patients undergoing transurethral resection of the prostate

Surgical stress and anesthesia cause immunosuppression that may predispose patients to postoperative infections. T helper lymphocytes play a major role in the immune response by controlling cell-mediated and humoral immunity. The type of immune response generated is determined by the differentiation of precursor T helper cells into Th1 or Th2 cells. Each cell subset secretes a particular array of cytokines that further augment the differentiation into that subset. Th1 cells produce interferon gamma and are responsible for cell-mediated immunity. Th2 cells produce interleukin-4 and are more effective in inducing humoral immunity. Cytokine concentrations are altered during surgery and anesthesia, which may effect Th cell predominance and, therefore, subsequent immune responses. We determined Th1 to Th2 cell ratios in patients undergoing transurethral resection of the prostate (TURP) using either spinal or general anesthesia. Mononuclear cells were isolated before anesthesia, immediately after surgery, and after 24 h from patients undergoing TURP, 10 under general anesthesia and 9 under spinal anesthesia. T helper cell subsets were quantified by using flow cytometry, and the ratio of Th1 to Th2 cells was calculated. Th1 to Th2 ratios in patients receiving spinal anesthesia increased over the three time points studied (P = 0.029) but did not change in patients who had general anesthesia (P = 0.11). At 24 h, Th1 to Th2 ratios were significantly higher in the spinal group than in patients who received general anesthesia (P = 0.0157). Total T helper cell numbers remained constant. These data suggest that, from an immunological viewpoint, spinal anesthesia, but not general anesthesia, benefits the patient by maintaining Th1 cell numbers, thereby promoting cellular immunity.

IMPLICATIONS

Spinal anesthesia may result in less immunosuppression after surgery. We found that the ratio of T helper 1 to T helper 2 cells was higher in patients undergoing prostate surgery by spinal rather than general anesthesia. Th1 cells promote protective immune responses that may result in fewer postoperative infections.

Immunomodulation: an important concept in modern anaesthesia

This review summarises evidence for immunomodulatory effect of drugs administered peri-operatively. The clinical significance of the balance of pro- and anti-inflammatory cytokines may be seen in certain disease states, for example, meningococcal meningitis and Lyme arthritis. This balance may be altered peri-operatively. Traditionally, these changes are considered to be due to the stress response of surgery, the response to cardiopulmonary bypass, or endotoxaemia. This review presents in vitro evidence suggesting that drugs modulating this cytokine balance include non-steroidal anti-inflammatory agents, phosphodiesterase inhibitors and opioids, acting through effects on intracellular cyclic nucleotide messenger systems. An important consequence of the pro-inflammatory cytokine activity is increased adhesion of neutrophils. Aspects of this process may be inhibited by avoiding low blood flow states, by reducing adhesion molecule expression (for example by use of pentoxifylline), or by use of negatively charged anions such as heparin. Neutrophil activity is generally depressed by intravenous anaesthetic induction agents, but is enhanced by opioids. Natural killer cell activity, which is involved in immunity against tumour cells and virally infected cells is transiently depressed by volatile anaesthetic agents and opioids. In contrast catecholamines enhance natural killer cell activity. Whereas decrease in immunoglobulin levels occur peri-operatively, this is not thought to be as a result of drugs at clinically used concentrations but rather due to haemodilution.

[Effects of propofol on blood concentration of cyclosporine]

OBJECTIVE

This study was designed to assess whether propofol modifies the blood concentrations of cyclosporine and lipoproteins, which bind cyclosporine.

STUDY DESIGN

Prospective open study.

PATIENTS

Fifteen consecutive grafted patients, scheduled for surgery allowing them to resume their oral treatment postoperatively. Their immunosuppressive treatment, included cyclosporine (Cy A), at a steady-state dosage.

METHODS

Blood samples were drawn and residual Cy A blood concentrations were measured the days before and after anaesthesia and before and immediately after discontinuing the propofol infusion. Serum triglycerides, cholesterol, high-density lipoprotein (HDL) concentrations were measured before and immediately after discontinuing the propofol infusion.

RESULTS

The 15 patients were given propofol by infusion for 30-210 min (mean 85 +/- 59 min). They received a total dose of propofol of 696 +/- 497 mg, a total fentanyl dose of 175 +/- 82 micrograms, and a total midazolam dose of 2.8 +/- 0.8 mg. The residual cyclosporine blood concentrations were similar the day before (142 +/- 47 ng.mL-1) and following anaesthesia (128 +/- 46 ng.mL-1) (P = 0.08). Serum cholesterol concentrations were not significantly influenced by propofol infusion, but serum triglycerides levels increased (1.46 +/- 0.66 vs 1.97 +/- 0.81 g.L-1), and HDL and LDL levels decreased (0.54 +/- 0.20 vs 0.47 +/- 0.18 g.L-1; 1.44 +/- 0.42 vs 1.28 +/- 0.37 g.L-1).

CONCLUSION

Propofol by infusion does not modify the cyclosporine concentration. It is concluded that propofol may be a suitable agent for intravenous anaesthesia in cyclosporine treated patients, provided a close postoperative monitoring of cyclosporine blood concentrations is maintained.

Propofol. An overview of its pharmacology and a review of its clinical efficacy in intensive care sedation

Propofol is a phenolic derivative that is structurally unrelated to other sedative hypnotic agents. It has been used extensively as an anaesthetic agent, particularly in procedures of short duration. More recently it has been investigated as a sedative in the intensive care unit (ICU) where it produces sedation and hypnosis in a dose-dependent manner. Propofol also provides control of stress responses and has anticonvulsant and amnesic properties. Importantly, its pharmacokinetic properties are characterised by a rapid onset and short duration of action. Noncomparative and comparative trials have evaluated the use of propofol for the sedation of mechanically ventilated patients in the ICU (postsurgical, general medical, trauma). Overall, propofol provides satisfactory sedation and is associated with good haemodynamic stability. It produces results similar to or better than those seen with midazolam or other comparator agents when the quality of sedation and/or the amount of time that patients were at adequate levels of sedation are measured. Patients sedated with propofol also tend to have a faster recovery (time to spontaneous ventilation or extubation) than patients sedated with midazolam. Although most studies did not measure time to discharge from the ICU, propofol tended to be superior to midazolam in this respect. In a few small trials in patients with head trauma or following neurosurgery, propofol was associated with adequate sedation and control of cerebral haemodynamics. The rapid recovery of patients after stopping propofol makes it an attractive option in the ICU, particularly for patients requiring only short term sedation. In short term sedation, propofol, despite its generally higher acquisition costs, has the potential to reduce overall medical costs if patients are able to be extubated and discharged from the ICU sooner. Because of the potential for hyperlipidaemia and the development of tolerance to its sedative effects, and because of the reduced need for rapid reversal of drug effects in long term sedation, the usefulness of propofol in long term situations is less well established. While experience with propofol for the sedation of patients in the ICU is extensive, there are still areas requiring further investigation. These include studies in children, trials examining cerebral and haemodynamic outcomes following long term administration and in patients with head trauma and, importantly, pharmacoeconomic investigations to determine those situations where propofol is cost effective. In the meantime, propofol is a well established treatment native to benzodiazepines and/or other hypnotics or analgesics when sedation of patients in the ICU is required. In particular, propofol possesses unique advantages over these agents in patients requiring only short term sedation.

Effects of propofol and Intralipid on immune response and prostaglandin E2 production

The present study evaluated the effects of propofol and its solvent Intralipid on the immune response and in vivo prostaglandin E2 production in patients during induction of anaesthesia and in healthy volunteers after Intralipid injection. Fifteen female patients (median age 48 years, ASA 1-2) scheduled for uterine dilatation and curettage were randomly assigned to two groups. In group 1 propofol (median dose 3.1 mg.kg-1) and in group 2 thiopentone (median dose 6.0 mg.kg-1) were injected intravenously over 60 s. Surgery was started after collection of the last blood sample. In the second part of this study, Intralipid 10% 0.3 ml.kg-1 was injected intravenously in eight healthy volunteers (four women and four men, median age 32 years) over 60 s. Plasma bicyclo-PGE2 concentrations increased during anaesthesia induction in both anaesthetic groups (p < 0.01). By contrast, no changes were seen in plasma bicyclo-PGE2 concentrations after Intralipid injection in volunteers. Lymphocyte proliferative responses to mitogens did not change during anaesthesia induction in patients. In volunteers, Intralipid injection caused a slight increase in T-cell percentages (p < 0.01) and unstimulated lymphocyte proliferative responses (p < 0.05), but it did not affect other lymphocyte subsets and immunoglobulin production. Intralipid and propofol were not found to be immunosuppressive at clinical doses used during anaesthesia induction.

[Use of Diprivan in burn patients]

The use of propofol should be avoided in the first 48 hours after a burn injury, as a major haemodynamic instability characterizes this period. For excision and/or grafting, propofol is mainly used as an induction agent. Maintenance of anaesthesia requires higher doses, often in the range of 15 mg.kg-1.h-1, and varying with each patient and the stage of the burn. Propofol is most appropriate in anaesthesia for dressing changes, considering the repetition of the procedures, interfering least with enteral nutrition and the quality of recovery, considered as essential. Combined with alfentanil or fentanyl, the dose of propofol is titrated to obtain the desired effect, from a simple sedation with patient co-operation to total anaesthesia.

[Does the lipid emulsion of Diprivan explain some pharmacological effects?]

In currently available experimental or clinical studies, there is no report of any adverse effect related to the lipid emulsion of propofol, for procedures not exceeding on average four hours of duration. General anaesthesia produced by propofol alone is associated with only moderate alterations of blood lipid concentrations. Therefore there is no restriction to the use of propofol. In the absence of precise data, it is recommended not to use propofol infusion in congenital hyperlipaemias (e.g., hyperchylomicronaemia). The lipid emulsion of propofol may alter the rheological properties of circulating blood, platelet aggregation, chemotactic activity of neutrophils and lymphocytes functions. These alterations are always limited. Furthermore, most studies which have recorded these effects are not directly applicable to clinical practice and additional studies are necessary. There are no data demonstrating that propofol would increase surgical bleeding or the incidence of postoperative infections. Since there is a low probability of these adverse effects, they should not limit the use of propofol.

Propofol infusion anaesthesia and immune response in minor surgery

This study was set up to evaluate the effects of propofol infusion anaesthesia on immunological function in minor surgery. Twenty-seven patients (median age 51 years, ASA 1-2) scheduled for minor breast surgery were randomly assigned to two groups. Anaesthesia was induced in group 1 with propofol 2.5 mg.kg-1 and maintained with propofol 12 mg.kg-1 x h-1 and 30% O2 in air, whereas in group 2 anaesthesia was induced with thiopentone 4 mg.kg-1 and maintained with 70% N2O in O2. Fentanyl and vecuronium were used in both groups. The percentages of T cells (p < 0.001), B cells (p < 0.01) and memory T cells increased (p < 0.01) in both groups. T helper cell percentages increased in the propofol but not in the thiopentone group (p < 0.05). The percentages of natural killer cells decreased from pre-induction values in both groups (p < 0.001). No changes were seen in lymphocyte proliferative responses. Minor breast surgery under propofol or conventional combined anaesthesia had only minor effects on the immune response. The higher percentage of T helper cells after propofol anaesthesia compared to conventional combined anaesthesia is beneficial, but its clinical importance remains to be determined.