The walk-in anergic patient. How best to assess the risk of sepsis following elective surgery

Preoperative lymphopaenia, mortality, and morbidity after elective surgery: systematic review and meta-analysis

BACKGROUND

In the general adult population, lymphopaenia is associated with an increased risk for hospitalisation with infection and infection-related death. The quality of evidence and strength of association between perioperative lymphopaenia across different surgical procedures and mortality/morbidity has not been examined by systematic review or meta-analysis.

METHODS

We searched MEDLINE, Embase, Web of Science, Google Scholar, and Cochrane databases from their inception to June 29, 2020 for observational studies reporting lymphocyte count and in-hospital mortality rate in adults. We defined preoperative lymphopaenia as a lymphocyte count 1.0-1.5×109 L-1. Meta-analysis was performed using either fixed or random effects models. Quality was assessed using the Newcastle-Ottawa Scale. The I2 index was used to quantify heterogeneity. The primary outcome was in-hospital mortality rate and mortality rate at 30 days.

RESULTS

Eight studies met the inclusion criteria for meta-analysis, comprising 4811 patients (age range, 46-91 yr; female, 20-79%). These studies examined preoperative lymphocyte count exclusively. Studies were of moderate to high quality overall, ranking >7 using the Newcastle-Ottawa Scale. Preoperative lymphopaenia was associated with a threefold increase in mortality rate (risk ratio [RR]=3.22; 95% confidence interval [CI], 2.19-4.72; P<0.01, I2=0%) and more frequent major postoperative complications (RR=1.33; 95% CI, 1.21-1.45; P<0.01, I2=6%), including cardiovascular morbidity (RR=1.77; 95% CI, 1.45-2.15; P<0.01, I2=0%), infections (RR=1.45; 95% CI, 1.19-1.76; P<0.01, I2=0%), and acute renal dysfunction (RR=2.66; 95% CI, 1.49-4.77; P<0.01, I2=1%).

CONCLUSION

Preoperative lymphopaenia is associated with death and complications more frequently, independent of the type of surgery.

PROSPERO REGISTRY NUMBER

CRD42020190702.

Factors predisposing to bacterial invasion and infection

BACKGROUND

Bacterial infections remain important causes of morbidity and mortality in surgical patients. Our understanding of the effects of bacteria on the host, and also the defense mechanisms available to the host, is improving all the time. Modern tools in biochemistry, immunology, and molecular biology have provided powerful methods to further our understanding of the complex interactions that contribute to our host defense response. This review reflects current thinking regarding the factors that contribute to bacterial infection and host defense response.

DATA SOURCES

This review was compiled after an extensive review of the current and historical literature, and highlights a number of areas involved in the pathogenesis of bacterial infection.

CONCLUSIONS

Bacteria can have a wide-ranging and deleterious effect on the host. Many different therapeutic approaches have been attempted to modulate the host response and limit the deleterious effects of bacteria. As our understanding of the underlying processes improves, these therapies should improve accordingly.

Delayed hypersensitivity testing as a clinical measure of cell-mediated immunity in the cat

The purposes of this study were to examine the cell-mediated immune response of the normal cat to the modified live feline viral rhinitis, calicivirus, and parvovirus (FVRCP) vaccine (Felocell CVR, Norden, Lincoln, NE), and to evaluate the intradermal skin test as a clinical measure of the immune response of cats. Vaccine and diluent were injected intradermally on the dorsal pinna of 34 normal adult cats. Skin thickness measurements, lymphocyte counts, and Concanavalin A mitogenesis indices were evaluated in 18 of these cats. Skin biopsies were obtained in 16 cats. In normal cats, the FVRCP vaccine induced a delayed hypersensitivity response characterized by a mononuclear infiltrate most pronounced at 72 h. Five cats with either feline leukemia (FeLV) or feline immunodeficiency virus (FIV) were tested and had a significantly reduced response to the skin test. The skin test provides a clinically useful method of evaluating immune function in cats and may be useful in development of a prognostic index.

Predicting infectious morbidity in elective operations

The determination of surgical risk is a major problem in general surgical practice and many studies have attempted to predict postoperative outcome. Clinical judgment is still a fundamental skill with which the experienced surgeon can estimate the risk of postoperative infectious morbidity. Predictive scores based on statistical analysis have also proven to be valid and useful tools. This discussion analyzes the importance of surgical risk prediction. With future research in this area, it is hoped that therapeutic strategies will result that will reduce or eliminate this risk.

Effects of anaesthesia and surgery on the immune response

Alterations have been found to occur in every component of immune response during anaesthesia and surgery. These alterations represent the body's general physiological responses and are mainly dependent on the extent of surgery, as well as other factors such as the patient's age and health status, medication and blood transfusion. Anaesthetic and operative complications have profound effects on these responses. Basically, the immune response to anaesthesia and surgery is a beneficial reaction, needed in local host defences and wound healing and in preventing the body from making autoantibodies against its own tissues. The responses may, however, contribute to the development of postoperative infections and spread of malignant disease. During uncomplicated conventional surgery, the immune response usually passes clinically unnoticed without any harmful effects. Absent responses and excessively high responses, on the other hand, harm the patient. Our understanding of immunological phenomena and our possibilities of controlling mediator activation are now lagging behind the technical advances made in operative treatment. If we want to decrease operative morbidity and mortality to below their present levels, more attention should be directed to immune responses to major surgery, injuries and operative complications with massive mediator release which place the surgical patient at risk. Experimental evidence suggests that results of treatment in injured and operated patients can in the future be improved by controlling immune responses and their mediator systems. Our current level of knowledge of immune responses is already helping us to avoid many immune-mediated complications. However, routine interference with these responses is not indicated.

Complications of infection and immunologic status after surgery for patients with esophageal cancer

Correlations between defective cell-mediated immunity (CMI) and infections following surgery for esophageal cancer were evaluated. Peripheral lymphocytes, T cells, B cells, PHA transformation, and PPD skin test were measured in 81 patients with esophageal cancer, 58 with gastric cancer, and 50 healthy controls. The depression of CMI was predominant to a similar extent in patients with esophageal cancer and in those with gastric cancer. The average level of PHA transformation immediately before surgery was significantly lower in the esophageal cancer patients with fatal septic complications than in those without such problems. Although preoperative radiation therapy markedly depressed the levels of the four parameters, this association was also noted in 28 patients not given radiation. It thus appears that PHA transformation may be valuable in the prediction of fatal septic complications after major surgery in patients with esophageal cancer.

Systemic and peritoneal host defense in peritonitis

Most of the work of host defense has been carried out in mixed patient populations. It is now clear that elective preoperative surgical patients have totally different host defense capabilities as compared to posttrauma patients or those suffering from peritonitis. Specific cell-mediated immune studies need to be repeated in these 2 patient groups as well. What will contribute clinical relevance to these studies will be the means to correct the defects. If these defects or--more correctly termed--abnormalities of host defense are, indeed, important and contribute to an increased sepsis rate and mortality from sepsis in affected patients, then correcting them should reduce these complications. This hypothesis can only be tested when such means become available. The issues of most interest in the next few years will be the significance of serum albumin in host outcome, the role of immunomodulators, the involvement of cytokines in the overall process of host defense, and the use of specific nutritional support regimens targeted to the immune system.

Ranitidine for prevention of postoperative suppression of delayed hypersensitivity

Cell-mediated immunity was assessed by skin testing with seven delayed-type common antigens in 20 patients undergoing major abdominal surgery and in 20 nonoperative control subjects. The 20 surgical patients were randomized to perioperative ranitidine (50 mg every 6 hours for 72 hours) or no ranitidine. The 20 control subjects received either no ranitidine or ranitidine in the same dosage as the surgical patients. Skin tests were performed 2 days before and 1 day after operation with the same time schedule in the control subjects. Postoperatively, the diameter of the positive skin test area decreased in each of 10 patients without ranitidine (p less than 0.006) but increased in 9 and was unchanged in 1 of the ranitidine-treated patients (p less than 0.01). The skin test changes were similar during the two tests in ranitidine-treated surgical patients and the nonoperative control subjects. Ranitidine did not amplify the response in the nonoperated group. The potential role of histamine blockade in reversal of other aspects of postoperative immunosuppression and reduction in the risk of infection should be explored.

Clinical assessment of host defense

Host defense mechanisms are a determinant of infection. Anergy in surgical patients is a signal of broadly based immune deficits, which include abnormalities in specific and local nonspecific antibacterial defenses and related life-threatening sepsis. Analysis of these abnormalities and other risk factors allows us to generate a long-predictive equation of individual probability of death.