Combined dysfunctions of immune cells predict nosocomial infection in critically ill patients

BACKGROUND

Nosocomial infection occurs commonly in intensive care units (ICUs). Although critical illness is associated with immune activation, the prevalence of nosocomial infections suggests concomitant immune suppression. This study examined the temporal occurrence of immune dysfunction across three immune cell types, and their relationship with the development of nosocomial infection.

METHODS

A prospective observational cohort study was undertaken in a teaching hospital general ICU. Critically ill patients were recruited and underwent serial examination of immune status, namely percentage regulatory T-cells (Tregs), monocyte deactivation (by expression) and neutrophil dysfunction (by CD88 expression). The occurrence of nosocomial infection was determined using pre-defined, objective criteria.

RESULTS

Ninety-six patients were recruited, of whom 95 had data available for analysis. Relative to healthy controls, percentage Tregs were elevated 6-10 days after admission, while monocyte HLA-DR and neutrophil CD88 showed broader depression across time points measured. Thirty-three patients (35%) developed nosocomial infection, and patients developing nosocomial infection showed significantly greater immune dysfunction by the measures used. Tregs and neutrophil dysfunction remained significantly predictive of infection in a Cox hazards model correcting for time effects and clinical confounders {hazard ratio (HR) 2.4 [95% confidence interval (CI) 1.1-5.4] and 6.9 (95% CI 1.6-30), respectively, P=0.001}. Cumulative immune dysfunction resulted in a progressive risk of infection, rising from no cases in patients with no dysfunction to 75% of patients with dysfunction of all three cell types (P=0.0004).

CONCLUSIONS

Dysfunctions of T-cells, monocytes, and neutrophils predict acquisition of nosocomial infection, and combine additively to stratify risk of nosocomial infection in the critically ill.

Evaluation of the effect of diagnostic methodology on the reported incidence of ventilator-associated pneumonia

BACKGROUND

The optimal method for diagnosing ventilator-associated pneumonia (VAP) is controversial and its effect on reported incidence uncertain. This study aimed to model the impact of using either endotracheal aspirate or bronchoalveolar lavage on the reported incidence of pneumonia and then to test effects suggested from theoretical modelling in clinical practice.

METHODS

A three-part single-centre study was undertaken. First, diagnostic performance of aspirate and lavage were compared using paired samples from 53 patients with suspected VAP. Secondly, infection surveillance data were used to model the potential effect on pneumonia incidence and antibiotic use of using exclusively aspirate or lavage to investigate suspected pneumonia (643 patients; 110 clinically suspected pneumonia episodes). Thirdly, a practice change initiative was undertaken to increase lavage use; pneumonia incidence and antibiotic use were compared for the 12 months before and after the change.

RESULTS

Aspirate overdiagnosed VAP compared with lavage (89% vs 21% of clinically suspected cases, p<0.0001). Modelling suggested that changing from exclusive aspirate to lavage diagnosis would decrease reported pneumonia incidence by 76% (95% CI 67% to 87%) and antibiotic use by 30% (95% CI 20% to 42%). After the practice change initiative, lavage use increased from 37% to 58%. Although clinically suspected pneumonia incidence was unchanged, microbiologically confirmed VAP decreased from 18 to 9 cases per 1000 ventilator days (p = 0.001; relative risk reduction 0.61 (95% CI 0.46 to 0.82)), and mean antibiotic use fell from 9.1 to 7.2 antibiotic days (21% decrease, p = 0.08).

CONCLUSIONS

Diagnostic technique impacts significantly on reported VAP incidence and potentially on antibiotic use.

One year outcome of intensive care patients with decompensated alcoholic liver disease

BACKGROUND

We aimed to examine the outcome of patients with decompensated alcoholic liver disease (ALD) admitted to a general intensive care unit (ICU).

METHODS

Retrospective observational cohort study of intensive care admissions over a 3 yr period was conducted. The study was set in an ICU in a UK university hospital with a tertiary liver referral unit. One hundred and ten admissions, involving 107 patients, with decompensated ALD were included. Intensive care, hospital, and 6 and 12 months mortality were recorded along with the outcome in diagnostic and organ system support subgroups. Intensive care, hospital, 6 month and 12 month mortality rates were 58, 71, 78 and 81%.

RESULTS

Hospital mortality in the sepsis/multiorgan failure group was 88%. Sixty-nine per cent of patients who were ventilated but required no other organ support survived to hospital discharge. However, the requirement for any other organ support, or a raised creatinine (>120 micromol litre(-1)) in the first 24 h, reduced the hospital survival to <15%. In those patients requiring acute renal replacement therapy, the hospital mortality was 94%.

CONCLUSION

Decompensated ALD requiring intensive care admission is associated with a high hospital mortality and consideration should be given to the futility of escalating organ support measures, particularly when renal replacement therapy is required.

The coagulative and cardiorespiratory responses to reamed intramedullary nailing of isolated fractures

We measured the changes during operation in seven markers of coagulation in a prospective series of 84 patients with fractures of the tibia or femur who were undergoing reamed intramedullary nailing. All patients were also continually monitored using transoesophageal echocardiography to assess marrow embolism. In a subset of 40 patients, intraoperative cardiopulmonary function was monitored, using pulmonary and systemic arterial catheterisation. The procedure produced a significant increase in prothrombin time, activated partial thromboplastin time, the level of prothrombin fragments F1+2 and D-dimers, and a decrease in the fibrinogen level, suggesting activation of both the coagulation and fibrinolytic pathways. There was evidence of both platelet hyper-reactivity and depletion, as estimated by an increase in beta-thromboglobulin levels and a decrease in the platelet count. In the patients who had invasive monitoring there was an incremental increase in mean pulmonary arterial pressure, with the changes being greatest during insertion of the guide-wire and reaming. The change in markers of coagulation, pulmonary artery pressure and arterial oxygen partial pressures correlated with the intraoperative embolic response. Greater changes in these parameters were observed during stabilisation of pathological fractures and in those patients in whom surgery had been delayed for more than 48 hours. Seven patients with pathological fractures developed more severe hypoxic episodes during reaming, which were associated with significantly greater arterial hypoxaemia, a fall in the right ventricular ejection fraction and an increase in the mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure and the pulmonary vascular resistance index. These changes suggested that the patients had transient intraoperative right heart strain. Eight patients developed significant postoperative respiratory compromise. They all had severe intraoperative embolic responses and, in the three who had invasive monitoring, there was a significantly greater increase in pulmonary artery pressure and alveolar-arterial oxygen gradient, and a fall in the ratio of arterial partial pressure of oxygen to the inspired oxygen concentration. Operative delay, intraoperative paradoxical embolisation and the scores for the severity of the coagulative and embolic responses were predictive of the development of postoperative respiratory complications on univariate logistic regression analysis. On multivariate analysis, however, only the embolic and coagulative scores were significant independent predictors of respiratory complications.

The coagulative and cardiorespiratory responses to reamed intramedullary nailing of isolated fractures

We measured the changes during operation in seven markers of coagulation in a prospective series of 84 patients with fractures of the tibia or femur who were undergoing reamed intramedullary nailing. All patients were also continually monitored using transoesophageal echocardiography to assess marrow embolism. In a subset of 40 patients, intraoperative cardiopulmonary function was monitored, using pulmonary and systemic arterial catheterisation.

The procedure produced a significant increase in prothrombin time, activated partial thromboplastin time, the level of prothrombin fragments F1+2 and D-dimers, and a decrease in the fibrinogen level, suggesting activation of both the coagulation and fibrinolytic pathways. There was evidence of both platelet hyper-reactivity and depletion, as estimated by an increase in β-thromboglobulin levels and a decrease in the platelet count. In the patients who had invasive monitoring there was an incremental increase in mean pulmonary arterial pressure, with the changes being greatest during insertion of the guide-wire and reaming.

The change in markers of coagulation, pulmonary artery pressure and arterial oxygen partial pressures correlated with the intraoperative embolic response. Greater changes in these parameters were observed during stabilisation of pathological fractures and in those patients in whom surgery had been delayed for more than 48 hours.

Seven patients with pathological fractures developed more severe hypoxic episodes during reaming, which were associated with significantly greater arterial hypoxaemia, a fall in the right ventricular ejection fraction and an increase in the mean pulmonary artery pressure, pulmonary capillary wedge pressure, central venous pressure and the pulmonary vascular resistance index. These changes suggested that the patients had transient intraoperative right heart strain.

Eight patients developed significant postoperative respiratory compromise. They all had severe intraoperative embolic responses and, in the three who had invasive monitoring, there was a significantly greater increase in pulmonary artery pressure and alveolar-arterial oxygen gradient, and a fall in the ratio of arterial partial pressure of oxygen to the inspired oxygen concentration. Operative delay, intraoperative paradoxical embolisation and the scores for the severity of the coagulative and embolic responses were predictive of the development of postoperative respiratory complications on univariate logistic regression analysis. On multivariate analysis, however, only the embolic and coagulative scores were significant independent predictors of respiratory complications.

Anaesthesia for gynaecological laparoscopy--a comparison between the laryngeal mask airway and tracheal intubation

In a single-blind, randomised, controlled study, we compared two anaesthetic techniques in 60 patients undergoing gynaecological laparoscopy. In the first group, ventilation was controlled, after paralysis and tracheal intubation. In the second group, a laryngeal mask airway was inserted and spontaneous or assisted ventilation allowed. There were no clinically significant differences in the intra-operative conditions of the two groups, although the procedure was quicker in the second group. The only significant difference in morbidity was a greater incidence of nausea and vomiting in the second group in the first 4 h after operation. We conclude that use of the laryngeal mask airway is an acceptable technique for elective gynaecological laparoscopy, in patients who are at low risk of regurgitation.

The alkalinisation of bupivacaine for intercostal nerve blockade

A double-blind randomised study was performed to investigate the effect of pH adjustment of bupivacaine, with adrenaline 1:200,000, on the duration of block and pain relief after intercostal nerve blockade following thoracotomy. One group (n = 10) received bupivacaine with adrenaline 1:200,000 (pH = 4.1) and the other (n = 10) received alkalinised bupivacaine with adrenaline 1:200,000 (pH = 6.9). There was no significant difference in block duration (mean 23.9 and 26.4 hours respectively) visual analogue pain scores or morphine usage. Patients were more likely to have a block during the first 12 hours if they received alkalinised bupivacaine (p less than 0.01, Chi-squared test). A progressive regression of block, not previously described, was observed, explicable by means of spread of local anaesthesia to adjacent intercostal nerves. Alkalinisation of bupivacaine with adrenaline for intercostal nerve blockade has little clinical benefit.