Peter Nightingale

Outcome of mechanically ventilated patients who require a tracheostomy

Objective:To estimate the prevalence of, the risk factors associated with, and the outcome of tracheostomy in a heterogeneous population of mechanically ventilated patients. Design:Prospective, observational cohort study. Setting:A total of 361 intensive care units from 12 countries. Patients:A cohort of 5,081 patients mechanically ventilated for >12 hrs. Interventions:None. Measurements and Main Results:A total of 546 patients (10.7%) had a tracheostomy during their stay in the intensive care unit. Tracheostomy was performed at a median time of 12 days (interquartile range, 7–17) from the beginning of mechanical ventilation. Variables associated with the performance of tracheostomy were duration of mechanical ventilation, need for reintubation, and neurologic disease as the primary reason of mechanical ventilation. The intensive care unit stay of patients with or without tracheostomy was a median of 21 days (interquartile range, 12–32) vs. 7 days (interquartile range, 4–12; p < .001), respectively, and the hospital stay was a median 36 days (interquartile range, 23–53) vs. 15 days (interquartile range, 8–26; p < .001), respectively. Adjusting by other variables, tracheostomy was independently related with survival in the intensive care unit (odds ratio, 2.22; 95% confidence interval, 1.72–2.86). Mortality in the hospital was similar in both groups (39% vs. 40%, p = .65). Conclusions:Tracheostomy is a common surgical procedure in the intensive care unit that is associated with a lower mortality in the unit but with a longer stay and a similar mortality in the hospital than in patients without tracheostomy.

Shock index: a re-evaluation in acute circulatory failure

STUDY OBJECTIVE To evaluate the relationship between the shock index SI (ratio of heart rate to systolic arterial pressure) and cardiac function and oxygen transport in an experimental model of hemorrhage and clinical septic shock. METHODS AND RESULTS This study was conducted in a hypovolemic circulatory failure model; 40% hemorrhage in the anesthetized pig and normovolemic hyperdynamic septic patients in the intensive care unit (ICU). Hemodynamic and oxygen transport variables were measured and their relationships to SI was examined. SI was inversely related to blood loss, cardiac index (CI), stroke volume (SV), mean arterial pressure (MAP) and left ventricular stroke work (LVSW) (r = -0.73, -0.75, -0.89 and -0.75, respectively P less than 0.01) following hemorrhage in the anesthetized pig. Oxygen transport variables, i.e. oxygen delivery (DO2) and mixed venous oxygen saturation (SvO2P) (r = -0.68 and -0.74, respectively, P less than 0.01) were also inversely related to the SI. Oxygen consumption (VO2) increased initially with increasing SI and fell when SI was greater than 3.0. In clinical septic shock and following blood volume expansion, the SI was not correlated to CI, SVI, MAP or systemic vascular resistance (SVR) (r = -0.01, -0.47, -0.34 and -0.14, respectively, P-value NS) but was inversely related to LVSWI (r = -0.68, P less than 0.01). There were no relationships between the SI and oxygen transport variables (DO2, SvO2) (r = -0.02 and -0.17, P-value NS) in septic shock. CONCLUSION SI provides a non-invasive means to monitor deterioration or recovery of LVSW during acute hypovolemic and normovolemic circulatory failure and its therapy. SI may be of limited value in the assessment of systemic oxygen transport and response to therapy in clinical shock.

Comparison of the hemodynamic and oxygen transport responses to modified fluid gelatin and hetastarch in critically ill patients: a prospective, randomized trial.

ObjectiveTo compare the hemodynamic and oxygen transport responses to a rapid (<10-min) infusion of 500 mL of modified fluid gelatin (group A) or hydroxyethyl starch (group B) in patients suffering from acute hypovolemia. DesignProspective, randomized, noncrossover study. SettingUniversity hospital, general intensive care unit. PatientsTwenty-eight patients with hypovolemia mechanically ventilated for concurrent acute respiratory failure. InterventionsPatients were mechanically ventilated. Pulmonary and femoral artery catheters were used for hemodynamic monitoring. Measurements and Main ResultsHemodynamic and oxygen transport variables were determined at baseline, 15 mins, and 30 mins after the infusion of each fluid. In both groups pulmonary artery occlusion pressure, stroke volume, and cardiac index significantly increased. In neither group did heart rate decrease. Oxygen delivery increased significantly in group A patients but not in group B patients. This result was due to greater hemodilution in group B patients. ConclusionsThere are no significant differences in the hemodynamic responses to hydroxyethyl starch or modified fluid gelatin. The hemodynamic and oxygen transport effects of artificial colloid solutions may not be entirely predictable and should be monitored in critically ill patients. (Crit Care Med 1994; 22:600–605)

PERSISTENCE OF SUPPLY DEPENDENCY OF OXYGEN UPTAKE AT HIGH LEVELS OF DELIVERY IN ADULT RESPIRATORY DISTRESS SYNDROME

ObjectiveTo identify any plateau in oxygen consumption (&OV0616;o2) when oxygen delivery (&U1E0A;o2) is increased in patients with the adult respiratory distress syndrome (ARDS). DesignClinical prospective study; multiple regression analysis was done to assess the relationship between &OV0616;o2 and &U1E0A;o2 for pooled data and for each individual patient. SettingUniversity hospital ICU. PatientsTwenty consecutive patients aged 18 to 78 yrs (mean 43.5) in whom ARDS was present during their ICU stay. InterventionsMultiple measurements were obtained in individual patients (mean number of measurements 40, range 20 to 83) and mathematical models were fitted to both pooled and individual patient data. &U1E0A;o2 ranged from 212 to 1550 mL/min.m2 with a maximum of 758 to 1550 mL/min.m2 (mean 1136). Because of the large variations between patients, it was not justifiable to describe a relationship for the pooled data and each case was analyzed individually. Measurements and Main ResultsWe found the optimal regression model to be linear in 13 patients, cubic in four, and either cubic or linear in one. Two patients demonstrated no significant relationship. The relationship for the group was determined from each patients data and was best described by linear regression. ConclusionsIn no patient was there evidence of a plateau, despite high levels of &U1E0A;o2 being achieved in all patients. (Crit Care Med 1991; 19:497)

EARLY AND SMALL CHANGES IN SERUM CREATININE CONCENTRATIONS ARE ASSOCIATED WITH MORTALITY IN MECHANICALLY VENTILATED PATIENTS

Emerging evidence suggests that minor changes in serum creatinine concentrations are associated with increased hospital mortality rates. However, whether serum creatinine concentration (SCr) on admission and its change are associated with an increased mortality rate in mechanically ventilated patients is not known. We have conducted an international, prospective, observational cohort study enrolling adult intensive care unit patients under mechanical ventilation (MV). Recursive partitioning was used to determine the values of SCr at the start of MV (SCr0) and the change in SCr ([&Dgr;SCr] defined as the maximal difference between the value at start of MV [day 0] and the value on MV day 2 at 8:00 am) that best discriminate mortality. In-hospital mortality, adjusted by a proportional hazards model, was the primary outcome variable. A total of 2,807 patients were included; median age was 59 years and median Simplified Acute Physiology Score II was 44. All-cause in-hospital mortality was 44%. The variable that best discriminated outcome was a SCr0 greater than 1.40 mg/dL (mortality, 57% vs. 36% for patients with SCr0 ≤1.40 mg/dL, P < 0.001). Among patients with SCr0 less than or equal to 1.40 mg/dL, &Dgr;SCr greater than 0.31 discriminated mortality (56% vs. 34%, P < 0.001). In multivariate analysis, geographic area, advanced age, severity of illness, reason for MV, and cardiovascular and hepatic failure were also associated with mortality. Our study suggests that SCr0 greater than 1.40 mg/dL and, in patients with low baseline SCr, a &Dgr;SCr greater than 0.31 are predictors of in-hospital mortality in mechanically ventilated patients.

Transforming growth factor-β1 869T/C, but not interleukin-6 −174G/C, polymorphism associates with hypertension in rheumatoid arthritis

OBJECTIVES Part of the deleterious effects of systemic inflammation on the cardiovascular system of patients with RA may be exerted via increased propensity to hypertension. IL-6 and TGF-beta1 are important regulators of the inflammatory response. In some, but not all, studies, IL6 -174G/C (rs1800795) and TGFB1 869T/C (rs1982073) gene polymorphisms have been associated with hypertension in the general population. The present study addressed their potential association with hypertension in RA patients. METHODS TGFB1 869T/C and IL6 -174G/C were identified in 400 RA patients and 422 local, non-RA controls using real-time PCR and melting curve analysis. Binary logistic and linear regression models were used to identify the independence of the effects of the polymorphisms on hypertension. RESULTS Genotypic and allelic frequencies of the two polymorphisms were similar in RA and controls. Within the RA group, there was no significant association between IL6 -174G/C and hypertension, but TGF 869T-allele carriers had significantly increased prevalence of hypertension compared with CC homozygotes (70.2 vs 55.2%; P = 0.023). This association remained significant after adjustment for other hypertension risk factors and medication (odds ratio = 1.96; 95% CI 1.02, 3.77; P = 0.044), and was more pronounced in patients with increased systemic inflammation. CONCLUSIONS This study suggests an association of TGFB1 869T/C, but not of IL6 -174G/C, with hypertension in RA patients. If this finding is confirmed in prospective studies, this polymorphism could be used as a screening tool for RA patients with higher risk of developing hypertension and lead to increased surveillance and earlier treatment.

An Assessment of the Acute Kidney Injury Network Creatinine-Based Criteria in Patients Submitted to Mechanical Ventilation

BACKGROUND AND OBJECTIVES The aim of our study was to assess the new diagnostic criteria of acute kidney injury (AKI) proposed by the Acute Kidney Injury Network (AKIN) in a large cohort of mechanically ventilated patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This is a prospective observational cohort study enrolling 2783 adult intensive care unit patients under mechanical ventilation (MV) with data on serum creatinine concentration (SCr) in the first 48 hours. The absolute and the relative AKIN diagnostic criteria (changes in SCr ≥ 0.3 mg/dl or ≥ 50% over the first 48 hours of MV, respectively) were analyzed separately. In addition, patients were classified into three groups according to their change in SCr (ΔSCr) over the first day on MV (ΔSCr): group 1, ΔSCr ≤ -0.3 mg/dl; group 2, ΔSCr between -0.3 and +0.29 mg/dl; and group 3, ΔSCr ≥ +0.3 mg/dl). The primary end point was in-hospital mortality, and secondary end points were intensive care unit and hospital length of stay, and duration of MV. RESULTS Of 2783 patients, 803 (28.8%) had AKI according to both criteria: 431 only absolute (AKI(A)), 362 both relative and absolute (AKI(R+A)), and 10 only relative. The relative criterion identified more patients when baseline SCr (SCr₀) was <0.9 mg/dl and the absolute when SCr₀ was >1.5 mg/dl. The diagnosis of AKI was associated with mortality. CONCLUSIONS Our study confirms the validity of the AKIN criteria in a population of mechanically patients and the criterias relationship with the baseline SCr.