Category Archives: All Updates

Acute Med, All Updates, ICU, PHARM, Resus

Supplemental oxygen decreases LV perfusion in volunteers

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Oxygen therapy in normoxic acute coronary syndrome patients is controversial, and a previous systematic review cautioned against it in uncomplicated MI. A volunteer study using cardiac imaging demonstrates the effects of supplemental oxygen on coronary blood flow.
 

OBJECTIVES: Oxygen (O2) is a cornerstone in the treatment of critically ill patients, and the guidelines prescribe 10-15 l of O2/min even to those who are initially normoxic. Studies using indirect or invasive methods suggest, however, that supplemental O2 may have negative cardiovascular effects. The aim of this study was to test the hypothesis, using noninvasive cardiac magnetic resonance imaging, that inhaled supplemental O2 decreases cardiac output (CO) and coronary blood flow in healthy individuals.
METHODS: Sixteen healthy individuals inhaled O2 at 1, 8 and 15 l/min through a standard reservoir bag mask. A 1.5 T magnetic resonance imaging scanner was used to measure stroke volume, CO and coronary sinus blood flow. Left ventricular (LV) perfusion was calculated as coronary sinus blood flow/LV mass.
RESULTS: The O2 response was dose-dependent. At 15 l of O2/min, blood partial pressure of O2 increased from an average 11.7 to 51.0 kPa with no significant changes in blood partial pressure of CO2 or arterial blood pressure. At the same dose, LV perfusion decreased by 23% (P=0.005) and CO decreased by 10% (P=0.003) owing to a decrease in heart rate (by 9%, P<0.002), with no significant changes in stroke volume or LV dimensions. Owing to the decreased CO and LV perfusion, systemic and coronary O2 delivery fell by 4 and 11% at 8 l of O2/min, despite the increased blood oxygen content.
CONCLUSION: Our data indicate that O2 administration decreases CO, LV perfusion and systemic and coronary O2 delivery in healthy individuals. Further research should address the effects of O2 therapy in normoxic patients.

Effects of oxygen inhalation on cardiac output, coronary blood flow and oxygen delivery in healthy individuals, assessed with MRI
European Journal of Emergency Medicine 2011, 18:25–30

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Pull that tongue

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A way of improving glottic visualisation when attempting fibreoptic intubation is for an assistant to perform a jaw thrust manoeuvre. This is nicely demonstrated in a video on the New England Journal website. However my retrieval medicine colleague and anaesthetist Dr Anthony Lewis pointed out the following situation and its solution:

What if they are a ‘difficult airway’ and you the jaw can’t move? Get your Magills forceps, grab the tongue and pull the tongue out. Very nice!

Acute Med, All Updates, ICU, Resus

Furosemide infusion in acute decompensated heart failure

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A randomised controlled trial of 308 patients with acute decompensated heart failure compared continuous furosemide infusion with ‘low’ dose (equal to their total daily oral loop diuretic dose in furosemide equivalents) or high dose furosemide boluses. There was no outcome difference between infusion and bolus, although the high dose (2.5 times previous oral diuretic dose 12 hourly for 48 hours) improved patients’ symptoms while causing transient elevations in serum creatinine. Editorialist Dr G Fonarow states:
‘..these findings should change current practice. Since a high-dose regimen may relieve dyspnea more quickly without adverse effects on renal function, that regimen is preferable to a low-dose regimen. Administration of boluses may be more convenient than continuous infusion and equally effective.’
 

BACKGROUND: Loop diuretics are an essential component of therapy for patients with acute decompensated heart failure, but there are few prospective data to guide their use.
METHODS: In a prospective, double-blind, randomized trial, we assigned 308 patients with acute decompensated heart failure to receive furosemide administered intravenously by means of either a bolus every 12 hours or continuous infusion and at either a low dose (equivalent to the patient’s previous oral dose) or a high dose (2.5 times the previous oral dose). The protocol allowed specified dose adjustments after 48 hours. The coprimary end points were patients’ global assessment of symptoms, quantified as the area under the curve (AUC) of the score on a visual-analogue scale over the course of 72 hours, and the change in the serum creatinine level from baseline to 72 hours.
RESULTS: In the comparison of bolus with continuous infusion, there was no significant difference in patients’ global assessment of symptoms (mean AUC, 4236±1440 and 4373±1404, respectively; P=0.47) or in the mean change in the creatinine level (0.05±0.3 mg per deciliter [4.4±26.5 μmol per liter] and 0.07±0.3 mg per deciliter [6.2±26.5 μmol per liter], respectively; P=0.45). In the comparison of the high-dose strategy with the low-dose strategy, there was a nonsignificant trend toward greater improvement in patients’ global assessment of symptoms in the high-dose group (mean AUC, 4430±1401 vs. 4171±1436; P=0.06). There was no significant difference between these groups in the mean change in the creatinine level (0.08±0.3 mg per deciliter [7.1±26.5 μmol per liter] with the high-dose strategy and 0.04±0.3 mg per deciliter [3.5±26.5 μmol per liter] with the low-dose strategy, P=0.21). The high-dose strategy was associated with greater diuresis and more favorable outcomes in some secondary measures but also with transient worsening of renal function.
CONCLUSIONS: Among patients with acute decompensated heart failure, there were no significant differences in patients’ global assessment of symptoms or in the change in renal function when diuretic therapy was administered by bolus as compared with continuous infusion or at a high dose as compared with a low dose. (Funded by the National Heart, Lung, and Blood Institute; ClinicalTrials.gov number, NCT00577135.).

Diuretic strategies in patients with acute decompensated heart failure
N Engl J Med. 2011 Mar 3;364(9):797-805

All Updates, ICU, Resus

African study on cricoid pressure

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The inventor of cricoid pressure. Possibly.

A colleague told me about a cricoid pressure paper I would otherwise have missed, since I don’t normally check out the International Journal of Obstetric Anaesthesia. This was a multicentre observational study in Malawi, in which 30 women (of 4891 general anaesthetics) vomited or regurgitated during induction of anaesthesia, in 24 of whom cricoid pressure was applied. 11 of the 77 deaths that occurred were associated with regurgitation, in 10 of which regurgitation contributed to the death. Nine of these 11 mothers who died had had cricoid pressure applied. The incidence of regurgitation was lower, but not significantly so, among those who did not have cricoid pressure applied. Not sure why it took nine years to publish this work.
 

BACKGROUND: Cricoid pressure is a routine part of rapid-sequence induction of general anaesthesia in obstetrics, but its efficacy in saving life is difficult to ascertain.
METHODS: As part of a prospective observational study of caesarean sections performed between January 1998 and June 2000 in 27 hospitals in Malawi, the anaesthetist recorded whether cricoid pressure was applied, the method of anaesthesia, the use of endotracheal intubation, the occurrence and timing of regurgitation and any other pre- or intra-operative complications. Logistic regression was used to assess the effect of cricoid pressure, type of anaesthetic and pre-operative complications on vomiting/regurgitation and death.
RESULTS: Data were collected for 4891 general anaesthetics that involved intubation. Cricoid pressure was applied in 61%; 139 women vomited or regurgitated, but only 30 on induction of anaesthesia, in 24 of whom cricoid pressure was applied. There were 77 deaths, 11 of which were associated with regurgitation, in 10 of which regurgitation contributed to the death. Nine of the 11 mothers had cricoid pressure applied. Only one died on the table, the rest postoperatively. All those who died had preoperative complications.
CONCLUSION: This study does not provide any evidence for a protective effect of cricoid pressure as used in this context, in preventing regurgitation or death. Preoperative gastric emptying may be a more effective measure to prevent aspiration of gastric contents.

Life-saving or ineffective? An observational study of the use of cricoid pressure and maternal outcome in an African setting
Int J Obstet Anesth. 2009 Apr;18(2):106-10

All Updates, Kids, PHARM, Resus

Weight formula validation

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Further validation of the UK-derived Luscombe weight formula has been made in the Australian setting. The nice simple formula for estimating the weight of a child based on age is:

Weight (kg) = 3 x age(years) + 7

It was compared with other formulae including the Best Guess formula, which is a bit more difficult to apply as the formula varies according to age range. This is reported in a previous post.
The authors provide the following cautionary advice:
“Whereas age-based formulae are, in the main, easy to calculate, the evidence suggests that ethnicity and body habitus pose serious challenges to their accuracy. In comparative studies, age-based formulae were found to be less accurate than the Broselow tape and parental estimate, with parental estimate being the most accurate weight estimation method. In light of this evidence, age-based formulae should only be used when these more accurate methods are not available.”

OBJECTIVE: Several paediatric weight estimation methods have been described for use when direct weight measurement is not possible. A new age-based weight estimation method has recently been proposed. The Luscombe formula, applicable to children aged 1-10 years, is calculated as (3 × age in years) + 7. Our objective was to externally validate this formula using an existing database.
METHOD: Secondary analysis of a prospective observational cohort study. Data collected included height, age, ethnicity and measured weight. The outcome of interest was agreement between estimated weight using the Luscombe formula and measured weight. Secondary outcome was comparison with performance of Argall, APLS and Best Guess formulae. Accuracy of weight estimation methods was compared using mean difference (bias), 95% limits of agreement, root mean square error and proportion with agreement within 10%.
RESULTS: Four hundred and ten children were studied. Median age was 4 years; 54.4% were boys. Mean body mass index was 17 kg/m(2) and mean measured weight was 21.2 kg. The Luscombe formula had a mean difference of 0.66 kg (95% limits of agreement -9.9 to +11.3 kg; root mean square error of 5.44 kg). 45.4% of estimates were within 10% of measured weight. The Best Guess and Luscombe formulae performed better than Argall or APLS formulae.
CONCLUSION: The Luscombe formula is among the more accurate age-based weight estimation formulae. When more accurate methods (e.g. parental estimation or the Broselow tape) are not available, it is an acceptable option for estimating children’s weight.

Validation of the Luscombe weight formula for estimating children’s weight
Emerg Med Australas 2011 Feb;23(1):59-62

All Updates, PHARM

Performance measures for HEMS services

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A recent study highlights the need for uniform standards of outcome data collection in Helicopter Emergency Medical Services (HEMS) in Great Britain and aero-medical retrieval services in Australia. Suggested patient outcome measurements by Britsh and Australian air medical respondents to the survey included:

  1. Mortality versus TRISS predicted mortality
  2. APACHE/ TRISS predicted mortality versus actual mortality.
  3. Use of national audit tools (eg, TARN)
  4. Nationally agreed Key Performance Indicators (KPIs)
  5. Clinical outcomes benchmarked against other services
  6. In-mission clinical indicators (eg, unanticipated procedures, adverse events)
  7. Physiological scoring linked to outcome measures
  8. ISS versus survival/disability
  9. KPIs from a national body. Mortality in isolation is not a useful marker of quality
  10. Clinical KPIs provided there is a reliable method of data collection
  11. Long-term outcome
  12. Interventions performed by doctors that contribute to patient mortality/morbidity.

Background Performance outcome measures are an essential component of health service improvement. Whereas hospital critical care services have established performance measures, prehospital care services have less well-established outcome measures and this has been identified as a key issue for development. Individual studies examining long-term survival and functional outcome measures have previously been used to evaluate prehospital care delivery. There is no set of standardised patient outcome measures for Helicopter Emergency Medical Services (HEMS) in the UK or Air Medical Services (AMS) in Australia. The aim of this study is to document the patient outcome measures currently in use within British HEMS and Australian AMS.
Methods This is an observational study analysing point prevalence of practice as of November 2009. A structured questionnaire was designed to assess the method of routine patient follow-up, and the timing and nature of applied patient outcome measures.
Results Full responses were received from 17/21 (81%) British services and 6/7 (86%) Australian services. The overall response rate was 82%.
Conclusions HEMS in Britain and Australian aeromedical retrieval services do not have uniform patient outcome measures. Services tend not to follow-up patients beyond 24 h post transfer. Patient outcome data are rarely presented to an external organisation and there is no formal data comparison between surveyed services. Services are not satisfied that the data currently being collected reflects the quality of their service.

Performance measurement in British Helicopter Emergency Medical Services and Australian Air Medical Services
Emerg Med J. 2011 Feb 3. [Epub ahead of print]

All Updates, Resus, Ultrasound

IVC collapse depends on breathing pattern

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A high degree of sonographically-visualised collapse of the inferior vena cava (IVC) during inspiration suggests a volume-responsive cardiac output. This inspiratory collapse is said to be due to a fall in intra-thoracic pressure. However, the IVC traverses the abdominal compartment and is therefore under the influences of hepatic weight, intra-abdominal pressure, and venous return of pooled splanchnic and lower extremity blood.
Diaphragmatic descent, which increases intra-abdominal pressure, may contribute to the respiratory change in IVC diameter. This was borne out in a volunteer study in which diaphragmatic breathing was compared with chest wall breathing. With diaphragmatic breathing there was a trend for a larger IVC collapse index (median 0.80, range 0.48–1.00 vs. 0.57, range 0.13–1.00, P = 0.053). The authors state:
“These findings suggest that during inspiration the IVC, in addition to responding to falling intra-thoracic pressure, may also be compressed with diaphragmatic descent and have implications regarding the use of IVC diameters to estimate the central venous pressure without knowing the manner of breathing, intra-abdominal pressure, or magnitude of diaphragmatic excursion.”
The take home message for me is that there is probably a more complex mechanism of IVC behaviour during respiration than is often taught, and that breathing pattern and abdominal issues may influence the IVC diameter and degree of collapse seen on ultrasound. This might not however negate the correlation between a high degree of collapse and fluid-responsiveness, which is what I’m looking for in my patients with shock or hypotension.
Incidentally the first author of this study is Bruce Kimura, a pioneer of focused echo in the emergency setting and author of a fantastic little book all about the parasternal long axis approach, which seems to be impossible to source on the web at the moment.

AIMS: Although the inspiratory ‘collapse’ of the inferior vena cava (IVC) has been used to signify normal central venous pressure, the effect of the manner of breathing IVC size is incompletely understood. As intra-abdominal pressure rises during descent of the diaphragm, we hypothesized that inspiration through diaphragmatic excursion may have a compressive effect on the IVC.
METHODS AND RESULTS: We measured minimal and maximal intrahepatic IVC diameter on echocardiography and popliteal venous return by spectral Doppler during isovolemic inspiratory efforts in 19 healthy non-obese volunteers who were instructed to inhale using either diaphragmatic or chest wall expansion. During inspiration, the maximal diaphragmatic excursion and popliteal vein flow were compared between breathing methods. The IVC ‘collapsibility index,’ IVCCI, was calculated as (IVC(max)-IVC(min))/IVC(max). The difference in diaphragmatic excursion between diaphragmatic and chest wall breaths in each subject was correlated with the corresponding change in IVCCI. Diaphragmatic breathing resulted in more diaphragmatic excursion than chest wall breathing (median 3.4 cm, range 1.7-5.8 vs. 2.2 cm, range 1.0-5.2, P= 0.0003), and was universally associated with decreased popliteal venous return (19/19 vs. 9/19 subjects, P< 0.004). The difference in diaphragmatic excursion correlated with the difference in IVCCI (Spearman’s rho = 0.53, P= 0.024).
CONCLUSION: During inspiration of equivalent tidal volumes, the reduction in IVC diameter and lower extremity venous return was related to diaphragmatic excursion, suggesting that the IVC may be compressed through descent of the diaphragm.

The effect of breathing manner on inferior vena caval diameter
Eur J Echocardiogr. 2011 Feb;12(2):120-3

All Updates, Resus

Alfentanil for Procedural Sedation

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An evaluation of single-agent alfentanil for procedural sedation in the ED has been published by the team at Hennepin County Medical Centre. A short-acting opioid, alfentanil induces 7 to 9 minutes of pain relief after a single bolus of 10 mcg/kg, a duration of action similar to that of propofol. It produces analgesia and sedation but not amnesia. In this study of 148 adult patients, alfentanil doses and the use of supplemental oxygen were at treating physician discretion. it appeared to be effective for ED procedural sedation but displayed a rate of airway or respiratory events leading to an intervention similar to that of previous reports of deeper sedation with propofol. The authors state ‘Despite very high rates of procedural pain and recall, subjects remained highly satisfied.’

STUDY OBJECTIVE: We administer alfentanil sedation for minor procedures in the emergency department (ED), and our primary objective is to assess the incidence of airway and respiratory adverse events leading to an intervention. Our secondary goals are to assess for other adverse events, the depth and duration of sedation, the incidence of subclinical respiratory depression, and patient perceptions of the quality of the sedation.
METHODS: In this observational study of adults receiving alfentanil for ED procedures, we recorded the incidence of airway or respiratory adverse events leading to an intervention (increase/addition of supplemental oxygen, bag-valve-mask ventilation, airway repositioning, or stimulation to induce breathing). Secondary goals were assessed with monitoring (including capnography), the Observer’s Assessment of Alertness/Sedation (OAA/S) scale, and postprocedure patient visual analog scale ratings of pain, recall, and satisfaction.
RESULTS: Airway or respiratory events leading to intervention were observed in 39% of the 148 subjects (supplemental oxygen 18%, bag-valve mask 3%, airway repositioning 2%, stimulation 18%); none were clinically significant. The median OAA/S nadir was 4 (interquartile range 3 to 5). Median patient ratings were positive (pain 26 mm, recall 98, satisfaction 100 mm).
CONCLUSION: Alfentanil appears effective for ED procedural sedation but displays a rate of airway or respiratory events leading to an intervention similar to that of previous reports of deeper sedation with propofol.

Alfentanil for Procedural Sedation in the Emergency Department
Ann Emerg Med. 2011 Feb;57(2):117-21

All Updates, PHARM

EMS makes a difference

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A Position Statement of the National Emergency Medical Services Advisory Council summarises the substantial evidence base documenting improved patient outcomes resulting from prehospital interventions and emergency medical services (EMS) systems. The fully referenced document is available in free full text .

The document concludes with this summary:

  • EMS makes a difference by producing clinically meaningful reductions in time to definitive treatment and improved health outcomes for patients with STEMI. Trained EMS providers are proficient in the capture and interpretation of 12-lead ECGs, can andshould make or participate in triage decisions to bypass closer hospitals in favor of to PCI-capable facilities, when clinically indicated. Efforts should continue to educate the public to call 9-1-1 at the first sign of a heart attack.

  • EMS makes a difference by decreasing the times to CPR and defibrillation, defined as the two critical factors for surviving cardiac arrest.

  • EMS makes a difference and is a critical component of effective stroke care. EMS must advocate for quality, standardized stroke protocols, performance improvement systems and training, and expedient transport of stroke patients to specialty care centers. EMS systems must partner with their dispatch agencies to ensure the use of quality Emergency Medical Dispatch protocols that provide proper stroke care instructions and activate appropriate resources. Efforts should continue to educate the public to call 9-1-1 at the first sign of a stroke.

  • EMS makes a difference by improving survival and neurological function for patients with respiratory emergencies. Proper prehospital care decreases the need for intubations and the number of required hospital admissions and improves cerebral performance in patients with respiratory distress. The addition of CPAP to the EMS tool kit provides immediate and longer-term benefits and further reduces hospitalization rates and healthcare costs.

  • EMS makes a difference by allowing EMS providers to use diagnostic tools such as blood glucometry, pulse oximetry, and 12-lead ECGs to efficiently evaluate patients and determine whether more advanced evaluation is necessary.

  • EMS makes a difference by treating many diabetic patients at home without the need for transport; thereby improving patient satisfaction and decreasing healthcare costs.

  • EMS makes a difference by accurately identifying patients experiencing out-of-hospital cardiac arrest who have no realistic chance of survival and determining whether transport to a hospital is warranted, thus reducing transports, decreasing hospital and patient costs, and increasing the availability of EMS resources.

  • EMS makes a difference with its expanding role in the healthcare system. EMS has the potential to provide improved patient outcomes and more customer satisfying primary care while offering clinically appropriate alternatives to hospital transport in addition to standard 9-1-1 responses. In a fully integrated healthcare system, EMS will provide preventive services, acute care, and overall community health.

  • EMS makes a difference in trauma care by providing rapid assessment, early notification to trauma centers, and rapid triage and transport to trauma centers, when appropriate. EMS will continue to be the community’s safety net.

  • EMS makes a difference with pediatric shock patients when shock is recognized and treated aggressively. The healthcare system must advocate for a systems approach to pediatrics similar to trauma, STEMI, and stroke systems of care and standardized training for all healthcare providers.

 

EMS Makes a Difference: Improved clinical outcomes and downstream healthcare savings
free full text

Acute Med, All Updates, ICU, PHARM, Resus

In V.Fib and talking to you!

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Some patients with severe refractory heart failure are kept alive thanks to implantable pumps such as the left ventricular assist device (LVAD). Many emergency physicians are likely to be unfamiliar with these but could encounter patients who have them. One particular peculiarity is that latter generation devices maintain non-pulsatile flow and provide or assist cardiac output independent of cardiac rhythm. In extreme situations patients can have life-sustaining cardiac outputs without palpable pulses or even audible heart sounds.

Click on image for Wikipedia article

A great example of how weird this can get is provided by a case of a 66 year male with an LVAD (HeartMate II (Thoratec Corporation)) who presented due to spontaneous discharge of his internal cardioverter-defibrillator (ICD). He was alert but had no pulses, and no detectable blood pressure using both a manual sphygmomanometer and an automated non-invasive blood pressure device. His 12 lead showed ventricular fibrillation. An invasive blood pressure showed a mean arterial pressure (mAP) of 80 mmHg. Several hours later his VF was successfully terminated and his mAP remained 80 mmHg
Some interesting points made by the authors include:

  • CPR was unnecessary in this guy but in cases of severe RV dysfunction it might need to be done to provide flow into the LV.
  • A danger of CPR in patients with an LVAD is the risk of damage to the device or ventricular rupture

LVAD use is significantly increasing so we can expect to encounter more episodes of previously impossible presentations to our emergency departments.

ABSTRACT
Optimal medical treatment, cardiac resynchronization, and the use of an implantable cardioverter defibrillator are established therapies of severe congestive heart failure. In refractory cases, left ventricular assist devices are more and more used not only as bridging to cardiac transplantation but also as destination therapy. Ventricular arrhythmias may represent a life-threatening condition and often result in clinical deterioration in patients with congestive heart failure. We report a case of asymptomatic sustained ventricular fibrillation with preserved hemodynamics caused by a nonpulsatile left ventricular assist device. Consecutive adequate but unsuccessful discharges of the implantable cardioverter defibrillator were the only sign of the usually fatal arrhythmia, prompting the patient to consult emergency services. Electrolyte supplementation and initiation of therapy with amiodarone followed by external defibrillation resulted in successful restoration of a stable cardiac rhythm after 3.5 hours.

Asymptomatic Sustained Ventricular Fibrillation in a Patient With Left Ventricular Assist Device
Ann Emerg Med. 2011 Jan;57(1):25-8.