Evaluating laboratory usage in the intensive care unit: patient and institutional characteristics that influence frequency of blood sampling

Critical Bias in Critical Care Devices

Critical care data contain information about the most physiologically fragile patients in the hospital, who require a significant level of monitoring. However, medical devices used for patient monitoring suffer from measurement biases that have been largely underreported. This article explores sources of bias in commonly used clinical devices, including pulse oximeters, thermometers, and sphygmomanometers. Further, it provides a framework for mitigating these biases and key principles to achieve more equitable health care delivery.

Routine Versus On-Demand Blood Sampling in Critically Ill Patients: A Systematic Review

OBJECTIVES

We aimed to provide an overview of the current evidence on routine versus on-demand blood sampling in critical care. We assessed the reported proportion of patients exposed to daily routine blood sampling, the tests performed, characteristics associated with more frequent blood sampling, and the reported benefits and harms of routine blood sampling compared with on-demand sampling.

DATA SOURCES

We systematically searched the Cochrane Library, the Excerpta Medica Database, and the Medical Literature Analysis and Retrieval System Online for studies assessing routine versus on-demand blood testing in critically ill patients from inception to September 2022.

STUDY SELECTION

Abstracts and full texts were assessed independently and in duplicate by two reviewers.

STUDY EXTRACTION

Data were extracted independently and in duplicate by two reviewers using predefined extraction forms.

DATA SYNTHESIS

Of 12,212 records screened, 298 full-text articles were assessed for eligibility. We included 70 studies; 50 nonrandomized interventional studies and 20 observational studies. Exposure to routine blood testing was 52-100% (very low certainty of evidence). Blood testing seemed to occur more frequently in medical intensive care settings with a median of 18 blood tests per patient day (interquartile range, 10-33) (very low certainty of evidence). Mixed biochemistry seemed to be the most frequently performed blood tests across all settings (five tests per patient day; interquartile range, 2-10) (very low certainty of evidence). Reductions in routine blood testing seemed to be associated with reduced transfusion rates and costs without apparent adverse patient outcomes (low certainty of evidence).

CONCLUSIONS

In this systematic review, routine blood testing in critically ill patients was common and varied considerably. A reduction in routine blood testing appeared to be associated with reduced transfusion rates and costs without adverse effects, but the evidence was very uncertain.

Central Line Access Is Predictive of Diagnostic Blood Loss and Transfusion in the Surgical Intensive Care Unit

BACKGROUND

Most patients in the surgical intensive care unit (SICU) have anemia and undergo extensive diagnostic laboratory testing (DLT). Consequently, patients undergo RBC transfusion, and many are discharged with anemia, both of which are associated with poorer outcomes.

OBJECTIVE

To characterize DLT blood loss in the SICU.

MATERIALS AND METHODS

We performed a 1-year retrospective study of 291 patients admitted to a SICU. The number of draws, average volume, and estimated discard volume were recorded, along with clinical and laboratory findings.

RESULTS

Patients who underwent greater amounts of DLT had lower hemoglobin levels at discharge (P ≤ .001). Admissions requiring central venous catheter (CVC) access (49.8%) demonstrated significantly higher DLT draws and rates of transfusion.

CONCLUSION

Findings from this study suggest that DLT blood loss contributes to anemia in the SICU, and that the presence and duration of CVC leads to increased testing, anemia, and RBC transfusion.

A descriptive study of routine laboratory testing in intensive care unit in nearly 140,000 patient stays

To describe the relationship between the use of laboratory tests and changes in laboratory parameters in ICU patients is necessary to help optimize routine laboratory testing. A retrospective, descriptive study was conducted on the large eICU-Collaborative Research Database. The relationship between the use of routine laboratory tests (chemistry and blood counts) and changes in ten common laboratory parameters was studied. Factors associated with laboratory tests were identified in a multivariate regression analysis using generalized estimating equation Poisson models. The study included 138,734 patient stays, with an ICU mortality of 8.97%. For all parameters, the proportion of patients with at least one test decreased from day 0 to day 1 and then gradually increased until the end of the ICU stay. Paradoxically, the results of almost all tests moved toward normal values, and the daily variation in the results of almost all tests decreased over time. The presence of an arterial catheter or teaching hospitals were independently associated with an increase in the number of laboratory tests performed. The paradox of routine laboratory testing should be further explored by assessing the factors that drive the decision to perform routine laboratory testing in ICU and the impact of such testing on patient.

Comparison of time taken to obtain an arterial blood gas result at the bedside using the ProximaTM point of care machine vs. a standard remote arterial blood gas analyser: A randomized controlled trial

Introduction

The ProximaTM point of care (POC) device enables arterial blood gas (ABG) samples to be analysed without the nurse leaving the patient. The benefits of this for work efficiency have not been evaluated.

Methods

We compared the time taken to obtain an ABG result using ProximaTM versus a standard ABG sampling system. Twenty patients were randomized to ABG sampling using ProximaTM, or a standard ABG system. Nurses were observed performing all ABG sampling episodes for a minimum of 24 hours and no more than 72 hours.

Results

The mean time taken to obtain a result using ProximaTM was 4:56 (SD = 1:40) minutes compared to 6:31 (SD = 1:53) minutes for the standard ABG technique (p < 0.001). Mean time away from the patient's bedside was 3.07 (SD = 1:17) minutes using the standard system and 0 minutes using ProximaTM (p < 0.001).

Conclusions

Reduced time for blood gas sampling and avoidance of time away from patients may have significant patient safety and resource management implications, but the clinical and financial significance were not evaluated.

Reducing inappropriate arterial blood gas testing in a level III intensive care unit: a before-and-after observational study

Background: Arterial blood gas (ABG) analysis is the most frequently performed test in intensive care units (ICUs), often without a specific clinical indication. This is costly and contributes to iatrogenic anaemia. Objectives: To reduce the number of ABG tests performed and the proportion that are inappropriate. Design, setting and participants: The indications for ABG analysis were surveyed at a 58-bed level III ICU during fortnightly periods before and after a multifaceted educational intervention which included the introduction of a clinical guideline. The number of ABG tests performed during the period July-December 2017 was compared with that for the period July-December 2018. Tests were predefined as inappropriate if performed at regular time intervals, at change of shift, concurrently with other blood tests or after a treatment was ceased on a stable patient or after ventilatory support or oxygen delivery was decreased in an otherwise stable patient. The study was enrolled on the Quality Improvement Projects Register and ethics approval was waived by the local ethics committee. Results: There was a 31.3% bed-day adjusted decrease in number of ABG tests performed (33 005 v 22 408; P < 0.001), representing an annual saving of A$770 000 and 100 litres of blood. The proportion of inappropriate ABG tests decreased by 47.3% (54.2% v 28.6%; P < 0.001) and the number of inappropriate ABG tests per bed-day decreased by 71% (2.8 v 0.8; P < 0.001). Patient outcomes before and after the intervention did not differ (standardised mortality ratio, 0.65 v 0.63; P = 0.22). Conclusion: Staff education and implementation of a clinical guideline resulted in substantial decreases in the number of ABG tests performed and the proportion of inappropriate ABG tests.

Variation in Arterial and Central Venous Catheter Use in Pediatric Intensive Care Units

OBJECTIVE

Describe patient and hospital characteristics associated with Arterial Catheter (AC) or Central Venous Catheter (CVC) use among pediatric intensive care units (ICUs).

DESIGN

Hierarchical mixed effects analyses were used to identify patient and hospital characteristics associated with AC or CVC placement. The ICU adjusted median odds ratios (ICU-AMOR) for the admission ICU, marginal R², and conditional intraclass correlation coefficient were reported.

SETTING

166 PICUs in the Virtual PICU Systems (VPS, LLC) Database.

PATIENTS

682,791 patients with unscheduled admissions to the PICU.

INTERVENTION

None.

MEASURES AND MAIN RESULTS

ACs were placed in (median, [interquartile range]) 8.2% [4.9%-11.3%] of admissions, and CVCs were placed in 14.9% [10.4%-19.3%] of admissions across cohort ICUs. Measured patient characteristics explained about 25% of the variability in AC and CVC placement. Higher Pediatric Index of Mortality 2 (PIM2) illness severity scores were associated with increased odds of placement (Odds Ratio (95th% Confidence Interval)) AC: 1.88 (1.87-1.89) and CVC: 1.82 (1.81-1.83) per 1 unit increase in PIM2 score. Primary diagnoses of cardiovascular, gastrointestinal, hematology/oncology, infectious, renal/genitourinary, rheumatology, and transplant were associated with increased odds of AC or CVC placement compared to a primary respiratory diagnosis. Presence of in-house attendings 24/7 was associated with increased odds of AC placement 1.32 (1.11-1.57). Admission ICU explained 4.9% and 3.5% of the variability in AC or CVC placement, respectively. The ICU-AMOR showed a patient would have a median increase in odds of 55% and 43% for AC or CVC placement, respectively, if the same patient moved from an ICU with lower odds of placement to an ICU with higher odds of placement.

CONCLUSIONS

Variation in AC or CVC use exists among PICUs. The admission ICU was more strongly associated with AC than with CVC placement. Further study is needed to understand unexplained variation in AC and CVC use.

Sialochemical analysis in polytraumatized patients in intensive care units

The profiles of polytraumatized patients in intensive care units were characterized. Serum and salivary markers were compared with normality between Classes I and II of APACHE II and between periods of hospitalization; these results were correlated. This was a prospective study on saliva charts and collection (n = 70). Profile: male, 27 years old, blunt traumas and collisions. Serum parameters with normality: decrease in pH, creatinine at admission to Class I, and at 48 and 72 hours in both classes; K+ at 48 h in Class II; Ca+ on admission in both classes and at 72 h in Class I. Increase in urea at 72 h in Class II, glucose at all times and in all classes, and Ca+ at 48 h in both classes. Class II had high Na+ at 48 and 72 h compared to Class I. In Class I, creatinine reduction occurred in 48 h and 72 h compared to admission and an increase of Ca+ at 48 h with admission. In Class II, pH and Na+ increased at 48 h and 72 h compared to admission. K+ decreased from admission to 48 h and increased from 48 h to 72 h. Urea increased from 48 to 72 hours. Creatinine decreased from admission to 48 and 72 hours. Ca+ increased from admission to 48 hours and decreased from 48 to 72 hours. There was an increase in the saliva levels in both classes and times in relation to normality. There was an increase in urea at admission, glucose at 72 h, and Ca+ at 48 h in Class II compared with Class I. Class I urea increased from admission to 48 h and Ca+ decreased from admission to 48 h. Class II urea decreased from 48 h to 72 h. Strong or very strong positive correlation was identified between blood and creatinine saliva at all times and regular and negative Ca+ at 72 h. This study provides evidence that salivary and serum biomarkers can be used together to monitor the evolution of the clinical symptoms of ICU patients.

Patient Blood Management in Pediatric Cardiac Surgery: A Review

Efforts to reduce blood product transfusions and adopt blood conservation strategies for infants and children undergoing cardiac surgical procedures are ongoing. Children typically receive red blood cell and coagulant blood products perioperatively for many reasons, including developmental alterations of their hemostatic system, and hemodilution and hypothermia with cardiopulmonary bypass that incites inflammation and coagulopathy and requires systemic anticoagulation. The complexity of their surgical procedures, complex cardiopulmonary interactions, and risk for inadequate oxygen delivery and postoperative bleeding further contribute to blood product utilization in this vulnerable population. Despite these challenges, safe conservative blood management practices spanning the pre-, intra-, and postoperative periods are being developed and are associated with reduced blood product transfusions. This review summarizes the available evidence regarding anemia management and blood transfusion practices in the perioperative care of these critically ill children. The evidence suggests that adoption of a comprehensive blood management approach decreases blood transfusions, but the impact on clinical outcomes is less well studied and represents an area that deserves further investigation.

Predictors of intraoperative testing in adults undergoing noncardiac surgery within a regional hospital system

BACKGROUND

The use of intraoperative testing is central to anesthesia practice, and point-of-care testing (POCT) is often used. Nevertheless, POCT is costly and its contribution to patient outcome is unknown. There is a lack of guidelines to describe which patients should undergo intraoperative testing or how results should be applied. As such, we undertook a historical cohort study evaluating intraoperative testing practices within our region where POCT is not used.

METHODS

In 2012, we obtained a random sample of 1,000 adult patients undergoing noncardiac surgery in three of our health system hospitals. Patient, surgical, and testing details were extracted, and the surgical procedures were categorized using the Johns Hopkins risk guidelines. Our primary outcome was the administration of at least one intraoperative test. We used a multivariable logistic regression model to identify factors associated with testing and described the time from ordering the tests to receiving the results using descriptive statistics.

RESULTS

Study results showed that 110/1,000 (11.0%) patients underwent 413 diagnostic tests. Complete blood count was the most commonly administered test (36.3%), and the mean (standard deviation) time to obtain all test results was 29.9 (19.9) min. High-risk procedures were associated with an odds ratio (OR) of 12.3 (95% confidence interval [CI], 8.3 to 18.2; P < 0.001). Other predictors of intraoperative testing included emergency surgery (OR, 3.8; 95% CI, 2.0 to 7.2; P < 0.001), number of comorbidities (OR, 1.1; 95% CI, 1.0 to 1.2; P = 0.03), and duration of surgery (OR, 2.3; 95% CI, 1.8 to 2.9; P < 0.001).

CONCLUSION

Intraoperative testing is common and more likely in patients undergoing high-risk surgical procedures. In a central laboratory system, there is substantial time from ordering the tests to receiving the results. The clinical impact of this delay is unknown. Further evaluation is required regarding the relationship between the time required for intraoperative test results and perioperative outcomes.

The Association Between Indwelling Arterial Catheters and Mortality in Hemodynamically Stable Patients With Respiratory Failure: A Propensity Score Analysis

BACKGROUND

Indwelling arterial catheters (IACs) are used extensively in the ICU for hemodynamic monitoring and for blood gas analysis. IAC use also poses potentially serious risks, including bloodstream infections and vascular complications. The purpose of this study was to assess whether IAC use was associated with mortality in patients who are mechanically ventilated and do not require vasopressor support.

METHODS

This study used the Multiparameter Intelligent Monitoring in Intensive Care II database, consisting of > 24,000 patients admitted to the Beth Israel Deaconess Medical Center ICU between 2001 and 2008. Patients requiring mechanical ventilation who did not require vasopressors or have a diagnosis of sepsis were identified, and the primary outcome was 28-day mortality. A model based on patient demographics, comorbidities, vital signs, and laboratory results was developed to estimate the propensity for IAC placement. Patients were then propensity matched, and McNemar test was used to evaluate the association of IAC with 28-day mortality.

RESULTS

We identified 1,776 patients who were mechanically ventilated who met inclusion criteria. There were no differences in the covariates included in the final propensity model between the IAC and non-IAC propensity-matched groups. For the matched cohort, there was no difference in 28-day mortality between the IAC group and the non-IAC group (14.7% vs 15.2%; OR, 0.96; 95% CI, 0.62-1.47).

CONCLUSIONS

In hemodynamically stable patients who are mechanically ventilated, the presence of an IAC is not associated with a difference in 28-day mortality. Validation in other datasets, as well as further analyses in other subgroups, is warranted.

Blood loss from laboratory diagnostic tests in children

BACKGROUND

Excessive diagnostic phlebotomy in children and critically ill patients is a frequent phenomenon in many hospitals. However, little attention is paid to a single blood volume taken routinely everyday from thousands of patients worldwide. The objective of the present study was to assess the volume of a single blood sample draw for laboratory testing in a pediatric population in relation to child age and weight, number of diagnostic tests requested by physicians, laboratory needs, and size of collection tube.

METHODS

A single blood volume draw for diagnostic tests was measured in 3136 consecutive routine samples taken from children (from 1 day to 18 years old) and placed into a Microvette® or regular sampling tubes. The serum excess was calculated by taking into account the serum volume needed for the requested number of tests and the dead volume of analyzer.

RESULTS

A huge variation in blood volume draws between individual patients, regardless of the number of tests requested, has been observed. The number of blood samples placed into the microvette decreased with patients' age, with 53.9% in children younger than 1 month old and 9.3% in children older than 12 years old. There was a clear-cut increase in the mean value of the blood volume draw with an increase in children's age. Only 2% of children up to 3 years old had a blood volume draw >1 mL/kg body weight.

CONCLUSIONS

Each pediatric laboratory should have a clear-cut recommendation on the amount on blood volume necessary for the requested number of tests.

Variation in diagnostic testing in ICUs: a comparison of teaching and nonteaching hospitals in a regional system

OBJECTIVES

To explore variation in the use of diagnostic testing in ICUs, with emphasis on differences between teaching and nonteaching ICUs.

DESIGN

Retrospective review of a prospective clinical ICU database.

SETTING

Five teaching and four nonteaching ICUs in Winnipeg, Canada, during 2006-2010.

PATIENTS

All adults admitted to the nine ICUs during the study period were eligible. After excluding subgroups restricted to teaching ICUs, inter-ICU transfers, prior ICU admission within 90 days, ICU length of stay less than 12 hours, and missing death dates, 10,262 patients were evaluated.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Our primary outcome variable (TotalTesting) was the cumulative number of nine common laboratory tests, three radiologic tests, and electrocardiograms performed in each ICU. We used multivariable median regression to identify factors associated with TotalTesting, including length of stay, demographics, admission details, type and severity of acute illness, and specific medical interventions. We estimated the predictive power of variables as the decline in pseudo-R2 (a goodness-of-fit measure for median regression) when omitting those variables from the model. Median (interquartile range) TotalTesting was 27 (18-49) in teaching ICUs and 20 (13-36) in nonteaching units. With multivariable adjustment, median TotalTesting was 7.1 higher (95% CI, 6.6-7.7) in teaching ICUs. The most influential variable was length of stay, accounting for almost half of the variation. ICU teaching status was the second most important factor, greater than the degree of physiologic derangement and details of medical management.

CONCLUSIONS

After adjustment for confounding variables, patients in teaching ICUs had slightly but significantly more diagnostic tests done than those in nonteaching ICUs. In addition to increasing costs, prior studies have shown that excessive testing can cause harm in various ways and does not improve outcomes. Interventions to reduce testing should be directed to all caregivers with responsibility for ordering diagnostic tests, in both teaching and nonteaching institutions.

The importance of implementing safe sharps practices in the laboratory setting in Europe

Healthcare workers are at risk of sharps injuries and subsequent infection from more than 40 bloodborne pathogens or species. Hepatitis B Virus (HBV), Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) together account for the vast majority of cases. The Directive 2010/32/EU “Prevention from sharp injuries in the hospital and healthcare sector”, issued to protect workers from these risks, requires an integrated approach to prevention including awareness-raising, education, training, elimination of unnecessary needles, safe procedures for sharps use and disposal, banning of recapping, vaccination, use of personal protective equipment, provision of safety-engineered devices, and appropriate surveillance, monitoring, response and follow-up.

As laboratories represent a high-risk setting both in the preanalytical and analytical phase, we reviewed accidents and prevention in this setting in the light of the new legislation.

Phlebotomy is the procedure carrying the highest risk of exposure and infection, involved in 30–50% of HIV and HCV cases detected in nationwide systems following accidental blood exposures implemented since the 1990s in Italy and France. In laboratories, problems in the management of sharps containers, recapping, needle disassembly by hand and blood transfer from syringes into tubes were observed and accounted for two-thirds of injuries. These accidents could be reduced through education and monitoring of behaviours, and introduction of medical devices incorporating safety-engineered protection mechanisms with appropriate training. Laboratory staff should be immunized against HBV, and know policies and procedures for the post-exposure management and prophylaxis. The management commitment to safety is crucial to ensure the necessary support to these changes.

The impact of anemia in moderate to severe traumatic brain injury

PURPOSE

The impact of anemia and restrictive transfusion strategies in traumatic brain injury (TBI) is unclear. The purpose of this study was to examine the outcome of varying degrees of anemia in patients who have sustained a TBI.

METHODS

We performed a retrospective study of all adult patients with isolated blunt TBI admitted between January 2003 and June 2010. The impact of increasing severity of anemia (Hb ≤8, ≤9, or ≤10 g/dl measured on three consecutive draws within the first 7 days of admission) and transfusions on complications, length of stay, and mortality was examined using univariate and multivariate analysis.

RESULTS

Of the 31,648 patients with blunt trauma admitted to the trauma service during the study period, 812 had an isolated TBI, among which 196 (24.1 %) met at least one of the anemia thresholds within the first 7 days [78 % male, mean age 47 ± 23 years, Injury Severity Score 16 ± 8, and head Abbreviated Injury Scale 3.3 ± 1.0]. Using a logistic regression model, anemia even as low as 8 g/dl was not associated with an increase in mortality [AOR8 = 0.8 (0.2, 3.2), p = 0.771; AOR9 = 0.8 (0.4, 1.6), p = 0.531; AOR10 = 0.6 (0.3, 1.3), p = 0.233] or complications. However, for all patients, the transfusion of packed red blood cells was associated with a significant increase in septic complications [AOR = 3.2 (1.5, 13.7), p = 0.030].

CONCLUSION

The presence of anemia in patients with TBI as low as 8 g/dl was not associated with increased mortality or complications, while the transfusion of red blood cells was associated with a significant increase in septic complications. Prospective evaluation of an optimal transfusion trigger in head-injured patients is warranted.

Blood conservation devices in critical care: a narrative review

Anaemia is associated with inferior outcomes in critically ill patients. It is difficult to prevent and is treated commonly with the transfusion of packed red cells. However, transfusion to augment oxygen delivery has not been shown to consistently offer a survival advantage when the haemoglobin concentration exceeds 7 g/dL. Several studies point to inferior outcomes when patients are transfused. Observational studies have confirmed that critically ill patients have frequent blood draws as part of their routine daily care. Cumulatively large volumes of blood are frequently taken, which contribute significantly towards the development of anaemia. Reducing iatrogenic blood loss may reduce the risk of developing anaemia and possibly the need for transfusion. Blood conservation devices may help to achieve this goal. The integration of blood conservation devices into routine care has been relatively slow in critical care. This review summarises the current evidence base and confirms that blood conservation devices do reduce the volume of iatrogenic blood loss. In the most recent studies, these devices have been shown to reduce transfusion requirements even in those intensive care units that follow a restrictive transfusion strategy.

Simulation of repetitive diagnostic blood loss and onset of iatrogenic anemia in critical care patients with a mathematical model

Anemia is prevalent among critical care patients and is attributed to pathologic and iatrogenic processes and bleeding. The extent that diagnostic blood loss contributes to anemia among adult critical care patients is controversial and multi-factorial. The aim of this study is to describe an erythrokinetic model that integrates rates of phlebotomy, erythropoiesis and red cell senescence with patient characteristics to predict the onset of iatrogenic anemia in an objective manner. Using sex-specific parameters, the model predicts that adults with (average body weight and average blood volume), initial hemoglobin concentration at mid-reference interval, active erythropoiesis and losing 53 mL of blood per day by phlebotomy would require 40-70 days to reach 70 g/L of hemoglobin. To mimic critical care patients with low initial hemoglobin and suppressed erythropoiesis, the influence of daily blood loss and total blood volume was predicted. Simultaneous lack of erythropoiesis, initial hemoglobin concentrations at the lower limit of the reference interval (110 g/L), low body weight and increased phlebotomy accelerated onset of ~70 g/L hemoglobin transfusion threshold to 9-14 days. This computer simulation depicts the extent that adult critical care patients with anemia risk factors could benefit from conservative test ordering practices and subsequent reduced diagnostic phlebotomy.

Effect of a laboratory result pager on provider behavior in a neonatal intensive care unit

BACKGROUND

A computerized laboratory result paging system (LRPS) that alerts providers about abnormal results ("push") may improve upon active laboratory result review ("pull"). However, implementing such a system in the intensive care setting may be hindered by low signal-to-noise ratio, which may lead to alert fatigue.

OBJECTIVE

To evaluate the impact of an LRPS in a Neonatal Intensive Care Unit.

METHODS

Utilizing paper chart review, we tallied provider orders following an abnormal laboratory result before and after implementation of an LRPS. Orders were compared with a predefined set of appropriate orders for such an abnormal result. The likelihood of a provider response in the post-implementation period as compared to the pre-implementation period was analyzed using logistic regression. The provider responses were analyzed using logistic regression to control for potential confounders.

RESULTS

The likelihood of a provider response to an abnormal laboratory result did not change significantly after implementation of an LRPS. (Odds Ratio 0.90, 95% CI 0.63-1.30, p-value 0.58) However, when providers did respond to an alert, the type of response was different. The proportion of repeat laboratory tests increased. (26/378 vs. 7/278, p-value = 0.02).

CONCLUSION

Although the laboratory result pager altered healthcare provider behavior in the Neonatal Intensive Care Unit, it did not increase the overall likelihood of provider response.

Effect of a blood conservation device in patients with preserved admission haemoglobin in the intensive care unit

An important iatrogenic cause of anaemia in the intensive care unit is loss of the discarded blood during phlebotomy via indwelling vascular catheters. A closed system blood conservation device has previously been shown to reduce the need for blood transfusion and to blunt the decrease of haemoglobin in intensive care unit patients. However such a device may not benefit patients who are admitted with a relatively preserved haemoglobin. In this sub-group analysis of a before-and-after study, 128 patients had admission haemoglobin > or =115 g/l and did not receive any blood transfusions while in the intensive care unit. In the control group of 50 patients a blood conservation device was not used, while in the active group of 78 patients the device was used. Use of the blood conservation device did not affect the haemoglobin trends when both groups were compared using the general linear model. For patients with admission haemoglobin > or = 115 g/l, use of a blood conservation device does not affect the subsequent rate of haemoglobin decline in the intensive care unit. These patients are unlikely to benefit from the use of such devices.

Comparison of complete blood counts in samples obtained from healthy dogs and cats by use of standard and microsample blood collection tubes

OBJECTIVE

To compare results of a CBC performed on blood samples obtained from healthy dogs and cats by use of standard and microsample collection tubes.

DESIGN

Evaluation study.

ANIMALS

29 healthy client-owned animals (14 dogs and 15 cats).

PROCEDURES

A blood sample (3 mL) was collected from each animal; 2.5 mL was transferred into a vacuum tube that contained sodium EDTA, and 0.5 mL was transferred into a microsample tube that contained sodium EDTA. Variables evaluated were total numbers of RBCs and WBCs, hemoglobin concentration, Hct, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration (MCHC), mean platelet volume, and plasma total protein concentration as well as neutrophil, lymphocyte, monocyte, eosinophil, basophil, and platelet counts. Results for the 2 types of tube in each species were compared by use of Pearson correlation coefficients, Passing-Bablok regression analysis, and Bland-Altman analysis.

RESULTS

The Pearson correlation coefficient was low for basophil count in cats and moderate, high, or very high for all other variables. Constant and proportional biases were identified for MCHC in dogs by use of Passing-Bablok regression analysis, although the mean difference between types of blood collection tubes was small. No evidence of constant or proportional bias for any other variable was revealed by regression analysis or Bland-Altman analysis.

CONCLUSIONS AND CLINICAL RELEVANCE

Samples obtained from healthy dogs and cats by use of microsample blood collection tubes provided clinically equivalent CBC results, compared with results for samples obtained by use of standard blood collection tubes, and minimized the total sample volume collected for diagnostic testing.

[Diagnostic blood losses in severe trauma patients]

OBJECTIVE

To analyze diagnostic (blood drawings) and iatrogenic (Continuous Renal Replacement Therapy, CRRT) blood losses (BL) in severe trauma patients.

METHOD

A one-year descriptive, prospective and observational study. We included patients over 15 years of age, admitted with severe trauma and who had a score of > or =16 on the Injury Severity Index (ISS). Those patients in whom limitation of therapeutic effort had been indicated were excluded. A total of 225 patients with 1619 days of evolution were analyzed for volume of BL/day/patient, type of diagnostic test, clinical outcome and utilization of CRRT. The variables were described as mean +/- standard deviation with the Student's T test.

RESULTS

Average blood loss of patient per day was 55.5+/-32.2 cc. Statistically significant differences were found between the blood volume drawn when the first day was compared to the second day, 73.5+/-32.2 vs. 56.3+/-21.9 (p<0.001); clinical outcome (alive vs death) 54.8+/-33 vs. 60.7+/-24.9 (p<0.05); severity (ISS<31 or > or =31) 54.65+/-20 vs. 61.5+/-28.5 (p<0.001), No RRT vs RRT: 50.9+/-18.9 vs. 97.2+/-72.6 (p<0.001).

CONCLUSIONS

The greatest diagnostic BL occurs during the resuscitation phase, in the patients who die, in those with greater severity and those undergoing CRRT.

The use of a blood conservation device to reduce red blood cell transfusion requirements: a before and after study

Introduction

Anaemia and the associated need for packed red blood cell (PRBC) transfusions are common in patients admitted to the intensive care unit (ICU). Among many causes, blood losses from repeated diagnostic tests are contributory.

Methods

This is a before and after study in a medical ICU of a university hospital. We used a closed blood conservation device (Venous Arterial blood Management Protection, VAMP, Edwards Lifesciences, Irvine, CA, USA) to decrease PRBC transfusion requirements. We included all adult (≥18 years) patients admitted to the ICU with indwelling arterial catheters, who were expected to stay more than 24 hours and were not admitted for active gastrointestinal or any other bleeding. We collected data for six months without VAMP (control group) immediately followed by nine months (active group) with VAMP. A restrictive transfusion strategy in which clinicians were strongly discouraged from any routine transfusions when haemoglobin (Hb) levels were above 7.5 g/dL was adopted during both periods.

Results

Eighty (mean age 61.6 years, 49 male) and 170 patients (mean age 60.5 years, 101 male) were included in the control and active groups respectively. The groups were comparable for age, gender, Acute Physiology and Chronic Health Evaluation (APACHE) II score, need for renal replacement therapy, length of stay, and Hb levels on discharge and at transfusion. The control group had higher Hb levels on admission (12.4 ± 2.5 vs. 11.58 ± 2.8 gm/dL, P = 0.02). Use of a blood conservation device was significantly associated with decreased requirements for PRBC transfusion (control group 0.131 unit vs. active group 0.068 unit PRBC/patient/day, P = 0.02) on multiple linear regression analysis. The control group also had a greater decline in Hb levels (2.13 ± 2.32 vs. 1.44 ± 2.08 gm/dL, P = 0.02) at discharge.

Conclusions

The use of a blood conservation device is associated with 1) reduced PRBC transfusion requirements and 2) a smaller decrease in Hb levels in the ICU.

Anemia and blood transfusion practices in the critically ill: a prospective cohort review

BACKGROUND

Nearly 75% of critically ill patients develop anemia in the intensive care unit (ICU). Anemia can be treated with red blood cell (RBC) transfusions, although evidence suggests that lower hemoglobin levels are tolerated in the critically ill. Despite such recommendations, variation exists in clinical practice.

METHODS

A prospective cohort was assessed for anemia and RBC transfusion practices in 100 consecutive adults admitted to our General Systems ICU.

RESULTS

The prevalence of anemia in this cohort was 98%. Mean blood loss via phlebotomy was 25+/-10.3 mL per patient per day. The RBC transfusion rate for the ICU stay was 40%, increasing to 70% in patients whose ICU stay was >7 days. The mean pretransfusion level of hemoglobin was 7.35+/-0.47 mg/dL for the total cohort, and 8.2+/-0.65 mg/dL for those with a history of cardiovascular disease.

CONCLUSION

Anemia was common in this critically ill cohort, with hemoglobin levels continuing to drop with ICU stay. Pretransfusion hemoglobin levels were lower than reported by others, yet the RBC transfusion rate was comparable. There was no association between anemia and phlebotomy practices in our ICU.

Anemia and red blood cell transfusion in neurocritical care

INTRODUCTION

Anemia is one of the most common medical complications to be encountered in critically ill patients. Based on the results of clinical trials, transfusion practices across the world have generally become more restrictive. However, because reduced oxygen delivery contributes to 'secondary' cerebral injury, anemia may not be as well tolerated among neurocritical care patients.

METHODS

The first portion of this paper is a narrative review of the physiologic implications of anemia, hemodilution, and transfusion in the setting of brain-injury and stroke. The second portion is a systematic review to identify studies assessing the association between anemia or the use of red blood cell transfusions and relevant clinical outcomes in various neurocritical care populations.

RESULTS

There have been no randomized controlled trials that have adequately assessed optimal transfusion thresholds specifically among brain-injured patients. The importance of ischemia and the implications of anemia are not necessarily the same for all neurocritical care conditions. Nevertheless, there exists an extensive body of experimental work, as well as human observational and physiologic studies, which have advanced knowledge in this area and provide some guidance to clinicians. Lower hemoglobin concentrations are consistently associated with worse physiologic parameters and clinical outcomes; however, this relationship may not be altered by more aggressive use of red blood cell transfusions.

CONCLUSIONS

Although hemoglobin concentrations as low as 7 g/dl are well tolerated in most critical care patients, such a severe degree of anemia could be harmful in brain-injured patients. Randomized controlled trials of different transfusion thresholds, specifically in neurocritical care settings, are required. The impact of the duration of blood storage on the neurologic implications of transfusion also requires further investigation.

Relationship between hemoglobin concentrations and outcomes across subgroups of patients with aneurysmal subarachnoid hemorrhage

OBJECTIVE

Anemia predicts poor outcome following aneurysmal subarachnoid hemorrhage (SAH). We hypothesized that this association would be stronger among patients with more severe SAH, since these patients are likely to be more vulnerable to secondary brain injury in the form of reduced cerebral oxygen delivery.

METHODS

Daily nadir hemoglobin (Hb) concentrations over 2 weeks following SAH were retrieved in 245 consecutive patients, and compared between those with a favorable versus unfavorable outcome. The analysis was repeated with patients dichotomized as follows: WFNS score 4-5 vs. 1-3; modified Fisher score (MFS) 4 vs. 0-3; and vasospasm present vs. absent. Mixed effect models and multivariable analysis using the generalized estimating equation were employed to assess correlated data with repeated measures.

RESULTS

Patients with an unfavorable outcome consistently had lower Hb concentrations, especially between days 6-11 following SAH (P ranging from <0.001 to 0.009), as well as a greater fall in Hb over time (beta = -0.07, P < 0.001). This was true regardless of WFNS score, MFS, or the presence or absence of vasospasm. However, the effect was somewhat more pronounced among patients with higher WFNS and modified Fisher scores.

CONCLUSION

Lower Hb levels are associated with worse outcomes regardless of SAH severity or the development of vasospasm. This finding may imply that a lower Hb concentration is largely a marker for a greater degree of systemic illness, rather than necessarily causing direct harm. However, the association is somewhat stronger among patients with more severe SAH. Thus, if there is a benefit for maintaining higher Hb levels with transfusions or erythropoietin, it may be more pronounced among these patients.

What factors influence arterial blood gas sampling patterns?

STUDY OBJECTIVE

To investigate if patterns of arterial blood gas (ABG) sampling were influenced by values of fractional inspiratory oxygen (FiO2), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2) and oxygen saturation (%SaO2).

SETTING

An intensive care unit (ICU) in a university teaching hospital located in the North of England, UK.

DESIGN

A retrospective, descriptive, correlation study based on patient records.

PARTICIPANTS

All patients admitted to the ICU for 24 hours or greater and who had an arterial line in situ.

MEASUREMENTS AND RESULTS

The study included the records of 65 patients consecutively admitted to the ICU. Patients in this study had more blood gases taken than reported elsewhere in the literature. While consistent correlation was found between values of FiO2, PCO2, PO2 and %SaO(2), values of PO2 were the most consistent.

CONCLUSIONS

Values of PO2 are associated with frequency of ABG sampling and to a lesser extent on FiO2. Nurses in this study opted to track changes in oxygenation using ABGs despite continuous monitoring of %SaO2.

Laboratory testing in the intensive care unit

Laboratory testing is ubiquitous among hospitalized patients and is more common among patients in the intensive care unit (ICU). Despite its high cost and prevalence, there are few data to support the current practice of laboratory testing in most ICUs. Although testing offers considerable potential benefits, it is not without risk, including misleading results, iatrogenic anemia, and therapeutic actions of uncertain benefit. Laboratory testing should be conducted as part of a therapeutic approach to a clinical problem, mindful of pretest probability of disease, the performance of the selected test, and the relative benefits and risks of testing. Considering the indication for a particular test can lead to a more rational approach to laboratory testing and better use of available tests.

Blood conservation strategies to reduce the need for red blood cell transfusion in critically ill patients

Anemia commonly affects critically ill patients. The causes are multifactorial and include acute blood loss, blood loss from diagnostic testing and blunted red blood cell production. Blood transfusions are frequently given to patients in intensive care units to treat low hemoglobin levels due to either acute blood loss or subacute anemia associated with critical illness. Although blood transfusion is a life-saving therapy, evidence suggests that it may be associated with an increased risk of morbidity and mortality. A number of blood conservation strategies exist that may mitigate anemia in hospital patients and limit the need for transfusion. These strategies include the use of hemostatic agents, hemoglobin substitutes and blood salvage techniques, the reduction of blood loss associated with diagnostic testing, the use of erythropoietin and the use of restrictive blood transfusion triggers. Strategies to reduce blood loss associated with diagnostic testing and the use of hemostatic agents and erythropoietin result in higher hemoglobin levels, but they have not been shown to reduce the need for blood transfusions or to improve clinical outcomes. Lowering the hemoglobin threshold at which blood is transfused will reduce the need for transfusions and is not associated with increased morbidity or mortality among most critically ill patients without active cardiac disease. Further research is needed to determine the potential roles for other blood conservation strategies.

Diagnostic blood loss in mechanically ventilated patients

BACKGROUND

Concern for the volume of blood loss resulting from diagnostic phlebotomy has been expressed in the literature for decades. Blood conservation strategies have been found to reduce the volume withdrawn for laboratory tests, but some patient populations may remain at risk.

OBJECTIVE

This study examines the frequency of phlebotomy and volume of diagnostic blood loss for critically ill mechanically ventilated patients in a small community hospital.

METHODS

The subjects were 43 critically ill adults who received mechanical ventilation for at least 24 hours during the first quarter of 2005. Data were collected from computerized medical records and included the frequency and types of laboratory tests performed over the course of hospitalization.

RESULTS

The mean total number of blood samples withdrawn was 69 (standard deviation = 59). The mean amount withdrawn per day was 16 mL (standard deviation = 7) with mean total volumes ranging from 57 to 1120 mL per patient. Four patients had more than 500 mL withdrawn. Chemistry analyses accounted for both the highest frequency of phlebotomy and the highest volume.

CONCLUSIONS

The daily volume of diagnostic blood loss for this population was less than the amounts previously reported in the literature, so there is some evidence of effectiveness of blood conservation strategies. However, some patients were still experiencing blood loss as the result of phlebotomy that may have been clinically significant. Additional strategies for reducing phlebotomy volumes are recommended.

Strict red blood cell transfusion guideline reduces the need for transfusions in very-low-birthweight infants in the first 4 weeks of life: a multicentre trial

BACKGROUND AND OBJECTIVES

Very-low-birthweight infants are among the most heavily transfused patients. The objective of this study was to verify if the introduction of a strict guideline would reduce the need for red blood cell transfusions in the first 4 weeks of life in these neonates.

MATERIALS AND METHODS

This was a multicentre prospective study of two cohorts of very-low-birthweight infants transfused in accordance with the recommendations of a neonatologist (Phase 1) or according to previously published guidelines (Phase 2).

RESULTS

In the first 28 days of life, 102 patients (68.5%) in Phase 1 and 117 (59.7%) in Phase 2 were transfused. The number of transfusions was 1.9 +/- 2.0 in Phase 1 and 1.4 +/- 1.6 in Phase 2 (P = 0.01). After adjusting for gestational age, blood loss and the presence of respiratory distress syndrome, the strict guideline reduced the number of transfusions in 17.6% (IC 95%-30.5% to -2.6%).

CONCLUSIONS

The strict guideline was effective in reducing erythrocyte transfusions in very-low-birthweight infants.

Blood conservation for critically ill patients

Anemia may be the most common illness of critically ill patients. The majority of critically ill patients are anemic at admission to the intensive care unit (ICU), and hemoglobin concentrations typically decline during the first 3 days of ICU stay. Hemoglobin continues to decline for patients with sepsis and higher severity of illness. This patient population may be at particular risk of adverse consequences of anemia given the cardiovascular, respiratory, and metabolic compromise frequently encountered during critical illness. The etiology of anemia of critical illness is multifactorial, resulting from phlebotomy, gastrointestinal bleeding, coagulation disorders, blood loss from vascular procedures, renal failure, nutritional deficiencies,bone marrow suppression, and impaired erythropoietin response.

Blood conservation in the intensive care unit

OBJECTIVE

To describe blood conservation strategies for critically ill patients.

DATA SOURCES

By using a predefined strategy, we searched the electronic databases of Medline, EMBASE, CINAHL, the Cochrane database of systematic reviews, Cochrane central register of controlled trials, ACP Journal Club, Database of abstracts of reviews and effects, and HealthSTAR for descriptions and evaluations of strategies of blood conservation among critically ill patients.

DATA SUMMARY

A number of blood conservation strategies have been used to prevent or treat anemia among critically ill patients. These include restrictive diagnostic phlebotomy using small-volume or pediatric phlebotomy tubes, point-of-care and inline bedside microanalysis, minimization of diagnostic sample waste, minimization of routine multiple daily phlebotomies, red blood cell salvage and antifibrinolytic agents for bleeding patients, consideration of removal of central venous and arterial catheters when no longer required for physiologic monitoring, threshold-based transfusion policy, and healthcare professional education.

CONCLUSIONS

There are many strategies of blood conservation for critically ill patients. The effects of these strategies on phlebotomy volumes, hemoglobin and hematocrit levels, transfusion requirements, clinical outcomes, as well as intensive care unit and laboratory resources and costs should be further evaluated.

The hematologic system as a marker of organ dysfunction in sepsis

Sepsis with acute organ dysfunction (severe sepsis) results from a systemic proinflammatory and procoagulant response to infection. Organ dysfunction in the patient with sepsis is associated with increased mortality. Although most organs have discrete anatomical boundaries and carry out unified functions, the hematologic system is poorly circumscribed and serves several unrelated functions. This review addresses the hematologic changes associated with sepsis and provides a framework for prompt diagnosis and rational drug therapy. Data sources used include published research and review articles in the English language related to hematologic alterations in animal models of sepsis and in critically ill patients. Hematologic changes are present in virtually every patient with severe sepsis. Leukocytosis, anemia, thrombocytopenia, and activation of the coagulation cascade are the most common abnormalities. Despite theoretical advantages of using granulocyte colony-stimulating factor to enhance leukocyte function and/or circulating numbers, large clinical trials with these growth factors are lacking. Recent studies support a reduction in the red blood cell transfusion threshold and the use of erythropoietin treatment to reduce transfusion requirements. Treatment of thrombocytopenia depends on the cause and clinical context but may include platelet transfusions and discontinuation of heparin or other inciting drugs. The use of activated protein C may provide a survival benefit in subsets of patients with severe sepsis. The hematologic system should not be overlooked when assessing a patient with severe sepsis. A thorough clinical evaluation and panel of laboratory tests that relate to this organ system should be as much a part of the work-up as taking the patient's blood pressure, monitoring renal function, or measuring liver enzymes.

Continuous blood gas monitoring using an in-dwelling optode method: comparison to intermittent arterial blood gas sampling in ECMO patients

INTRODUCTION

The ability to measure postmembrane arterial blood gases is essential in the management of critically ill neonates treated with extracorporeal membrane oxygenation (ECMO). A new technology using, the Paratrend 7 system (Diametrics Medical, High Wycombe,UK) allows for continuous measurement of pH, PCO(2) and PO(2), and calculates oxygen saturation, bicarbonate, and base excess.

OBJECTIVE

To evaluate and compare the results of continuous blood gas measurement using the Paratrend 7 system with a standard system of blood gas analysis in our intensive care unit.

DESIGN

Prospective, controlled, interventional study.

SETTING

The neonatal intensive care unit of a tertiary referral center.

PATIENTS

Neonates who required extracorporeal life support and were expected to have frequent postmembrane arterial blood sampling during the testing period.

RESEARCH DESIGN AND METHOD

To enable Paratrend 7 sensor access to the ECMO circuit, the postmembrane access port extension set that is routinely used for blood drawn for blood gas analysis was used. The study began with the insertion of the Paratrend 7 sensor. Subjects remained on the study until the ECMO was discontinued and/or frequent blood gases were no longer needed. The blood gas results from the Paratrend 7 system were not used in clinical management of the patient. BLOOD GAS MEASUREMENT: During the study period, with each blood sample drawn for laboratory analysis, a printout from the Paratrend 7 monitor was recorded for comparison.

RESULTS

A total of 242 pairs of blood gas samples were collected from 10 neonates. The mean bias/precision for pH was -0.02/0.04; for PO(2) 68.35/93.44 mm Hg; and for PCO(2) 1.75/4.23 mm Hg. The correlation (r value) between the sensor reading and the blood gases were 0.89 for pH, 0.96 for PO(2), and 0.73 for PCO(2) (Table 1).

CONCLUSION

The blood gases compared in the two methods had a strong correlation for pH, PCO(2) and PO(2). Results of this study indicate that this technology provides an accurate means of monitoring continuous blood gas parameters in neonatal ECMO patients. Use of the Paratrend 7 should allow reduced health-care provider exposure to blood and decreased patient iatrogenic blood loss.

Continuous blood gas monitoring using an in-dwelling optode method: clinical evaluation of the Neotrend sensor using a luer stub adaptor to access the umbilical artery catheter

INTRODUCTION

Arterial blood gases are essential in the management of critically ill neonates. A new technology using the Neotrend system (Diametrics Medical) allows for continuous measurement of pH, PaCO(2), and PaO(2), and calculates oxygen saturation, bicarbonate, and base excess.

OBJECTIVE

To evaluate and compare the results of continuous blood gas measurement using the Neotrend system with a standard system of blood gas analysis in our intensive care unit.

DESIGN

Prospective, controlled, interventional study.

SETTING

The neonatal intensive care unit of a tertiary referral center.

PATIENTS

Neonates with respiratory distress who required respiratory support and frequent arterial blood gas sampling and had a UAC.

RESEARCH DESIGN AND METHOD

To enable Neotrend sensor access to an existing Argyle umbilical artery catheter (UAC) the catheter was cut at the 25-cm mark and connected to an 18-gauge blunt needle luer stub adaptor (Vygon 95440). The study began with the insertion of the Neotrend sensor. Subjects remained on the study until the UAC was discontinued and/or frequent blood gases were no longer needed. The blood gas results from the Neotrend system were not used in clinical management of the patient. BLOOD GAS MEASUREMENT: During the study period, with each blood sample drawn for laboratory analysis, a printout from the Neotrend monitor was recorded for comparison.

RESULTS

A total of 217 pairs of blood gas samples were collected from seven neonates. The mean bias/precision for pH was 0.01/0.04; for PaO(2) 0.72/18.5 mm Hg; and for PaCO(2) 3.96/2.63 mm Hg. The correlation (r value) between the sensor reading and the blood gases were 0.85 for pH, 0.96 for PaO(2), and 0.92 for PaCO(2).

CONCLUSION

The blood gases compared in the two methods had a strong correlation for pH, PaCO(2), PaO(2), and oxygen saturation. Although the bicarbonate and base excess values showed suboptimal statistical correlation, the difference was not clinically relevant. Results of this study indicate that this technology provides an accurate means of monitoring continuous blood gas parameters in neonatal patients. It also allows reduced healthcare provider exposure to blood and decreased patient iatrogenic blood loss.

Use of a rapid arterial blood gas analyzer to estimate blood hemoglobin concentration among critically ill adults

OBJECTIVE

To evaluate whether measurement of the hemoglobin (Hb) concentration with a blood gas analyzer approximates that determined by a conventional coulter counter in critically ill adults.

DESIGN

Prospective patient series.

SETTING

A 32-bed cardiovascular, neurosurgical, trauma and medical-surgical intensive care unit in a single Canadian center.

PATIENTS

We consecutively recruited 202 critically ill adults, the majority of whom had recent cardiac or vascular surgery, neurosurgery or trauma.

MEASUREMENTS

The nurse obtained a single arterial blood sample within a few hours of the patient's admission to the intensive care unit. The Hb concentration was determined from each blood sample in a masked fashion, using both a blood gas analyzer and a conventional laboratory coulter counter.

MAIN RESULTS

A total of 202 consecutive paired analyses were conducted. There was a highly significant correlation between the coulter counter and blood gas analyzer methods of Hb measurement (r2 = 0.98, 95% confidence interval [CI] = 0.97-0.99; P < 0.0001). Using the method of Bland and Altman, the overall mean difference in Hb concentration between the coulter counter and the blood gas analyzer was -4.3 g/l (95% CI = -11.0 to 2.4). Of the 11 (5.4%) Hb measurements that extended beyond the upper and lower 95% CI, 10 (5.0%) were within +/- 3 g/l of these confidence limits.

CONCLUSIONS

An arterial blood gas analyzer may provide a valid alternative method to the traditional coulter counter for the rapid assessment of Hb concentration among critically ill adults. Since issues related to its safety, quality control, data entry and cost savings have yet to be addressed, however, use of such point of care testing should be viewed as a supplement to conventional laboratory testing.

Pilot study of the accuracy of bedside glucometry in the intensive care unit

OBJECTIVE

To evaluate the accuracy of bedside glucometry among critically ill patients.

DESIGN

Prospective audit, with sequential specimen collection.

SETTING

Thirty-two-bed cardiovascular, neurosurgical, and medical-surgical intensive care unit in a single Canadian center.

PATIENTS

Ten critically ill adults, who were sequentially followed during their intensive care unit stay. Eight had diabetes mellitus, and three were in shock.

MEASUREMENTS AND MAIN RESULTS

Repeat arterial blood samples were obtained by the attending nurse, who withdrew a portion of the sample and performed reflectance glucometry at the bedside. The remainder was immediately sent in a vacuum-sealed plasma separation tube to the hospital laboratory, and analyzed using a conventional plasma glucose analyzer by a laboratory technologist. Sequential samples were taken at intervals of at least 12 hrs of one other. A total of 105 arterial glucose pairs were obtained. There was a significant correlation between the laboratory and glucometry determined glucose concentrations (intraclass correlation coefficient = 0.86, p <.0001). The overall average laboratory-glucometry glucose difference was -0.04 mmol/L (95% confidence interval [CI] -2.3-2.2 mmol/L). Five out of 105 values (4.8%) lay beyond these confidence bounds. The square of the Pearson correlation coefficient (r(2)) between the mean glucose level and the laboratory-glucometry glucose difference was not significant (0.01, 95% CI 0.005-0.04; p =.22), suggesting the absence of any trend between rising glucose concentration and the laboratory-glucometry difference.

CONCLUSIONS

Bedside glucose testing of arterial whole blood samples may be an accurate alternative to laboratory plasma glucose measurement among critically ill adults, within approximately 2.3 mmol/L of certainty. Because previous studies have suggested that this bedside technique may be prone to a moderate degree of error among patients in shock as well as those with an abnormal blood pH or hematocrit, larger studies are needed to confirm our findings.

Point-of-care testing

Point-of-care testing technology rapidly is changing the way physicians practice medicine by facilitating the availability of biochemical parameters immediately or almost immediately. The constant evolution and developments in [figure: see text] microchemistry and computer technology will make this area a dynamic part of medicine with the constant emergence of improved and newer technologies. Clinicians must not forget, however, that the best analyzer and monitor is the physician, nurse, or other health care worker in direct contact with the patient, constantly reassessing, re-examining, and integrating all of the physiologic and biochemical data in the context of the history and physical examination. If POC testing is implemented, its goal should be to improve and assist in patient care.

Sequential organ scoring as a measure of effectiveness of critical care

We performed an observational nonrandomised study in a critical care unit of a large district general hospital in England to establish whether sequential organ scoring could be used as a measure of effectiveness of intensive care. The degree of organ dysfunction of 75 consecutive patients admitted to the critical care unit whose duration of stay exceeded 48 h was measured using the Logistic Organ Dysfunction System score. The trends in organ dysfunction of survivors and non-survivors were significantly different with function improving in survivors and remaining constant or worsening in non-survivors. In both groups, the degree of organ dysfunction decreased over the first three days of intensive care. On an individual patient basis, we achieved no change or an improvement in organ score over this period in 80% of patients. In terms of individual organ function, intensive care consistently improved scores relating to the cardiovascular, respiratory and renal systems over the first 72 h of care, but not the neurological, hepatic or haematological systems. In conclusion, daily organ scoring usefully reflects the ability of an intensive care unit to stabilise or reverse physiological dysfunction.

The use of a blood conservation pressure transducer system in critically ill patients

We tried to determine if a blood conservation pressure transducer system reduced blood transfusions, increased haemoglobin concentration or reduced line infections in critically ill patients. One hundred patients were randomly allocated to conventional or blood conserving systems attached to systemic and pulmonary arterial catheters. Intravascular lines were cultured after removal. There were no significant differences in transfusions or haemoglobin concentration. Blood conservation: median units transfused, 2 (range 0-19); mean haemoglobin at 7 days, 11.2 g.dl-1 (SD, 1.0). Conventional: median units, 2 (range 0-34); mean haemoglobin at 7 days, 11.1 g.dl-1 (SD 1.0). Thirty-seven of 99 arterial lines were colonised in the controls compared with 29 of 96 in the blood conservation group. Patients who required haemofiltration in both groups had significantly increased transfusion requirements. Haemofiltration: median 6 units (range 0-34) vs. non-haemofiltered: median 1 (range 0-14; p < 0.001). There were no significant differences in transfusions, haemoglobin concentration or line colonisation with the blood conservation system. There is considerable potential for blood conservation during haemofiltration.

Important role of nondiagnostic blood loss and blunted erythropoietic response in the anemia of medical intensive care patients

OBJECTIVE

To determine incidence, severity, characteristics, and causes of anemia and transfusion requirements in medical intensive care patients.

DESIGN AND SETTING

Open prospective clinical study in a 24-bed medical intensive care unit in a tertiary-care university hospital.

PATIENTS

Patients (N = 96) treated in the intensive care unit for >3 days.

INTERVENTIONS

None.

MEASUREMENTS

Parameters of erythropoiesis and red blood cell metabolism, including hemoglobin, reticulocyte counts, serum iron, transferrin, ferritin, haptoglobin, vitamin B12, folic acid, and erythropoietin concentrations were determined serially. Diagnostic blood loss and red blood cell transfusions were recorded, and the total blood loss was estimated from changes in hemoglobin concentrations and the amount of hemoglobin transfused.

MAIN RESULTS

The median hemoglobin concentration was 12.1 g/dL at admission and 11.2 g/dL at the end of the intensive care unit stay. A total of 74 patients (77%) suffered from anemia and received 257 red blood cell units, approximately half of which were given within the first 5 days. Three patients who received 19 red blood cell units were admitted with acute gastrointestinal bleeding, but in the remainder, a median total blood loss of 128 mL/d was not (n = 60) or not solely (n = 11) a result of overt bleeding. Diagnostic blood loss declined from a median of 41 mL on day 1 to <20 mL after 3 wks and contributed 17% (median) to total blood loss. Acute renal failure, fatal outcome, and simplified acute physiology score >38 on admission were associated with a 5.8-, 7.0-, and 2.8-fold increase in total blood loss. Reticulocyte counts and erythropoietin concentrations were inappropriately low for the degree of anemia, and plasma transferrin saturation was mostly <20%.

CONCLUSIONS

Anemia is frequent and results in a high requirement for red blood cell transfusions in the medical intensive care setting. A major proportion of blood loss is not caused by overt bleeding or diagnostic blood sampling but, rather, may result from various other reasons, e.g., occult gastrointestinal bleeding and renal replacement therapy. The erythropoietic response to anemia is blunted, probably as a consequence of an inappropriate increase in erythropoietin production and diminished iron availability. (Crit Care Med 1999; 27:2630-2639)