Pulse pressure variation with respiration (PPV) predicts fluid responsiveness in mechanically ventilated patients. Because this is due to transmission of airway pressures to the vasculature, it is hypothesised that low tidal volume ventilation (or non compliant lungs, or both) results in less PPV even in fluid-responsive patients. This was confirmed in a study looking at the effect of airway driving pressure (Pplat – PEEP) on PPV. The study confirmed the positive predictive value of a high PPV, but some of those patients with a ‘low’ PPV (below a commonly accepted cut-off of 13%) were still fluid responsive, which was defined as a 15% or more increase in stroke index after a fluid challenge. In fluid responders with a low PPV, (Pplat – PEEP) was less than or equal to 20 cmH20.
Take home message: In mechanically ventilated patients, PPV values <13% do not rule out fluid responsiveness, especially when (Pplat – PEEP) was less than or equal to 20
The influence of the airway driving pressure on pulsed pressure variation as a predictor of fluid responsiveness
Intensive Care Med. 2010 Mar;36(3):496-503
Monthly Archives: March 2010
Whole-body CT during trauma resuscitation
German trauma patients are more likely to survive if they have a whole body CT rather than selective scans. Or that’s what this paper would have you believe IF you’re happy with the retrospective comparison, multivariate adjustments, and potential confounders. Still, if it helps you get your radiologists to play ball, the reference is…
Effect of whole-body CT during trauma resuscitation on survival: a retrospective, multicentre studyLancet. 2009 Apr 25;373(9673):1455-61
No sedation for patients receiving mechanical ventilation
Danish intensivists demonstrate that just bolusing morphine without sedatives results in fewer days on a ventilator and a shortened ICU and hospital stay. Obviously not appropriate for some patients (therapeutic hypothermia, head injury with raised ICP, etc.) and some patients randomised to the no sedation group eventually required sedation. Delirium was three times more common in the no sedation group (20% vs 7%).
A protocol of no sedation for critically ill patients receiving mechanical ventilation: a randomised trial
Lancet. 2010 Feb 6;375(9713):475-80
Identifying sick kids is still difficult
A systematic review to identify clinical features that have value in confirming or excluding the possibility of serious infection in children presenting to ambulatory care settings resulted in the calculation of likelihood ratios. Clinical features with a positive likelihood ratio of more than 5.0 were deemed red flags (ie, warning signs for serious infection); features with a negative likelihood ratio of less than 0.2 were deemed rule-out signs.
The features identified in several studies as red flags were :
- Cyanosis (+LR range 2.66-52.20)
- Rapid breathing (+LR 1.26-9.78)
- Poor peripheral perfusion (+LR 2.39-38.80)
- Petechial rash (+LR 6.18-83.70)]
In one primary care study the following were identified as strong red flags:
- Parental concern (+LR 14.40, 95% CI 9.30-22.10)
- Clinician instinct (+LR 23.50, 95 % CI 16.80-32.70)
Temperature of 40 degrees C or more had value as a red flag in settings with a low prevalence of serious infection.
What about ruling out serious illness?
Unfortunately, no single clinical feature had rule-out value but some combinations can be used to exclude the possibility of serious infection-for example, pneumonia is very unlikely (-LR 0.07, 95% CI 0.01-0.46) if the child is not short of breath and there is no parental concern.
An accompanying editorial sums up the challenge of paediatric emergency medicine in a nutshell:
“What is clear is that in 2010 we do not know how to effectively recognise or rule out severe disease in ill children and what is more, we do not even have a cohesive national or even global research strategy to address this problem.”
Diagnostic value of clinical features at presentation to identify serious infection in children in developed countries: a systematic review.
Lancet. 2010 Mar 6;375(9717):834-45
Ketamine and procedural success
There is a myth that increased muscular tone caused by ketamine leads to an increased failure rate of joint manipulations when this agent is used for procedural sedation in the ED. This is neither borne out by the published evidence nor our own experience of a series of cases, which have been presented by Louisa Chan at a former (UK) College of Emergency Medicine Conference. At the Australasian College of Emergency Medicine Annual Scientific Conference in Melbourne these data were presented by A/Professor Taylor’s team in Victoria, which provide evidence that procedural failure rate is in fact lower with ketamine than with other commonly used sedatives. Here is the abstract reproduced with the kind permission of A/Prof Taylor:
Failure to successfully complete a procedure following emergency department sedation
DMcD Taylor1,2 for the Emergency Department Sedation Study Investigators
1Austin Health; 2University of Melbourne, Melbourne, Australia
Aims: To determine the nature and incidence of, and factors contributing to, failure to successfully complete a procedure fol- lowing sedation in the ED
Methods: Eleven Australian ED enrolled consecutive adult and paediatric patients between January 2006 and December 2008. Patients were included if a sedative drug was administered for an ED procedure. Data collection was prospective and employed a specifically designed form.
Results: Two thousand six hundred and twenty three patients were enrolled (60.3% male, mean age 39.2 years). Failure to successfully complete the procedure occurred in 148 (5.6%) cases. Most failures occurred with attempted reductions of fractured/dislocated shoulders (35 cases), hips (32), ankles (21) and elbows (14). However, failure rates were highest among fractured/dislocated hips (18.5%), digits (13.7%), femurs (11.1%), mandibles (10.2%) and elbows (9.3%). Failure rates for residents/registrars (5.9%), consultants (5.6%) and nurse practitioners (5.9%) did not differ (P = 0.92). Overall, failure rates for the various drugs (used alone or in combina- tion) did not differ (P = 0.07). However, ketamine (used alone or in combination) was associated with a much lower failure rate (2.9%) than all other sedation drugs used (midazolam 5.8%, propofol 6.5%, fentanyl 6.9%, nitrous oxide 7.1%, and morphine 7.8%).
Conclusion: Procedural failure is uncommon although some pro- cedures are at higher risk, especially dislocated hip reduction. Failure rates do not appear to be affected by the designation of the operator or the sedative drug used. However, ketamine use is associated with lower failure rates. For those procedures at higher risk of failure, the provision of optimal conditions (spe- cialist unit assistance, venue, drug selection) may minimise failure rates.
Emergency Medicine Australasia 2010;22(S1):A52-3
Ketamine use by paramedics
A poster presentation at the Australasian College of Emergency Medicine’s Annual Scientific Conference in Melbourne in November 2009 reports 100 cases of pre-hospital ketamine use for analgesia by paramedics in New Zealand – reproduced below with permission of the author:
Ketamine is a safe and effective analgesic for pre-hospital paramedic led pain relief
HM Hussey & BC Ellis
Introduction: There have been a number of reports on the use of ketamine by pre-hospital physicians, with many advocating its use as the ideal pre-hospital analgesic and sedative due to its airway and cardiovascular stability. There however is little published on its use by paramedics. This study aims to review its effectiveness and safety when administered pre-hospital by paramedics.
Method: Prospective observational study of 100 consecutive administrations by St Johns ambulance paramedics in 2008–09 using a specifically designed data sheet. Demographic data, adjuvant analgesics used, ketamine dose, pre and post dose pain scores on VNRS and physiological parameters were collected. In addition paramedics and patients completed a satisfaction rating score.
Results: The mean dose of ketamine used was 30.2 mg and the mean improvement in pain was 5.10. Ketamine was used both as a lone agent and with morphine; excellent analgesia was achieved in both groups. The most common reason for use was limb trauma followed by burns and extractions from scene. There were no episodes of hypotension or airway compromise. 15% of patients had an adverse reaction all mild and mostly comprising minor psychotropic effects. The median satisfaction rating for both paramedics and patients was ‘Good’.
Conclusion: These results back the use of Ketamine by St John’s Ambulance paramedics and the authors support its use by other pre-hospital services as a safe and effective analgesic.
Emergency Medicine Australasia 2010;22(S1):A30
Imaging for PE in pregnancy
A review article on pulmonary embolism in pregnancy reminds us that the mortality associated with untreated PE far outweighs the potential oncogenic and teratogenic risk incurred by fetal exposure to diagnostic imaging for PE.
Teratogenicity
The minimum dose of radiation associated with increased risk of teratogenicity in human beings has yet to be firmly established, but on the basis of compiled mouse, rat, and human data, radiation exposure of 0·1 Gy at any time during gestation is regarded as a practical threshold beyond which induction of congenital abnormalities is possible.
Oncogenicity
An exposure of the conceptus to 0·01 Gy above natural background radiation increases the probability of cancer before the age of 20 years from 0·03% to 0·04%.
Reassuringly, a chest radiograph, ventilation perfusion scan, and conventional pulmonary angiogram combined with CT pulmonary angiogram expose the fetus to a total of 0·004 Gy.
Pulmonary embolism in pregnancy
Lancet. 2010 Feb 6;375(9713):500-12
Procalcitonin reduced antibiotic use
In a multicentre study in France, adult patients expected to stay in the intensive care unit for more than 3 days who had suspected bacterial infections were randomised to have antibiotics started or stopped based on predefined cut-off ranges of procalcitonin concentrations (n=307 patients) or to receive antibiotics according to present guidelines (control, n=314). Patients in the procalcitonin group had significantly more days without antibiotics than did those in the control group (14∙3 days [SD 9·1] vs 11∙6 days [SD 8∙2]; absolute difference 2∙7 days, 95% CI 1∙4 to 4∙1, p<0∙0001) without a difference in 28-day or 60-day mortality or ICU length of stay. An editorial points out that as an open-label trial, a treatment bias might have occurred because physicians were aware that their patients had had procalcitonin measurements taken, raising the question as to whether the procalcitonin concentrations themselves or simply the act of measuring procalcitonin led to the recorded reduction in antibiotic use.
The study used the following guidelines for starting, continuing, or stopping of antibiotics according to procalcitonin concentrations:
Guidelines for starting of antibiotics – Excludes situations requiring immediate antibiotic treatment (eg, septic shock, purulent meningitis)
- Concentration <0·25 μg/L – Antibiotics strongly discouraged
- Concentration ≥0·25 and <0·5 μg/L – Antibiotics discouraged
- Concentration ≥0·5 and <1 μg/L – Antibiotics encouraged
- Concentration ≥1 μg/L – Antibiotics strongly encouraged
If blood sample taken for calculation of procalcitonin concentration at early stage of episode, obtain a second procalcitonin concentration 6–12 h later
Guidelines for continuing or stopping of antibiotics
- Concentration <0·25 μg/L – Stopping of antibiotics strongly encouraged
- Decrease by ≥80% from peak concentration, or concentration ≥0·25 and <0·5 μg/L – Stopping of antibiotics encouraged
- Decrease by <80% from peak concentration, and concentration ≥0·5 μg/L – Continuing of antibiotics encouraged
- Increase of concentration compared with peak concentration and concentration ≥0·5 μg/L – Changing of antibiotics strongly encouraged
Use of procalcitonin to reduce patients’ exposure to antibiotics in intensive care units (PRORATA trial): a multicentre randomised controlled trial
Lancet. 2010 Feb 6;375(9713):463-74
Cardiocerebral resuscitation
An emergency medical service introduced a cardiocerebral resuscitation protocol and compared outcomes with a standard ACLS protocol.
Cardiocerebral resuscitation (CCR) was defined as:
- initiation of 200 immediate, uninterrupted chest compressions at a rate of 100 compressions ⁄ min
- analyzing the rhythm and delivering a single defibrillator shock, if indicated
- 200 more chest compressions before the first pulse check or rhythm reanalysis
- epinephrine (1 mg intravenous or intraosseous) as soon as possible or with each 200 compression cycle
- endotracheal intubation delayed until after three cycles of chest compressions
Data was analysed from a registry including data on 3515 patients from 62 EMS agencies, some of which instituted CCR (in a total of 1024 patients). Outcome predictors were identified using logistic regression analysis and
Individuals who received CCR had better outcomes across age groups. The increase in survival for the subgroup with a witnessed Vfib was most prominent on those <40 years of age (3.7% for standard ALS patients vs. 19% for CCR patients, odds ratio [OR] = 5.94, 95% confidence interval [CI] = 1.82 to 19.26). Neurologic outcomes were also better in the patients who received CCR (OR = 6.64, 95% CI = 1.31 to 32.8). Within the subgroup that received CCR, the factors most predictive of improved survival included witnessed arrest, initial rhythm of Vfib⁄Vtach, agonal respirations upon arrival, EMS response time, and age. Neurologic outcome was not adversely affected by age.
Cardiocerebral Resuscitation Is Associated With Improved Survival and Neurologic Outcome from Out-of-hospital Cardiac Arrest in Elders
Academic Emergency Medicine 2010;17(3):269 – 275
Collapsible IVC predicts 'low' CVP
The IVC undergoes a change in diameter during the respiratory cycle. Investigators compared the degree of sonographic IVC respirophasic diameter change with CVP in 73 patients and found >= 50% change in diameter predicted a CVP< 8 mmHg with 91% sensitivity (95% CI 71% to 99%) and 94% specificity (95% CI 84% to 99%). The positive predictive value was 87% (95% CI 66% to 97%), and the negative predictive value was 96% (95% CI 86% to 99%). Presumably the rather arbritrary CVP of 8 was chosen because of its importance as a target for goal directed therapy in sepsis guidelines. A more meaningful endpoint such as a fluid responsive cardiac output might be a more clinically relevant application of this technique, which had been demonstrated previously.
Emergency Department Bedside Ultrasonographic Measurement of the Caval Index for Noninvasive Determination of Low Central Venous Pressure
Ann Emerg Med. 2010 Mar;55(3):290-5