Yearly Archives: 2011

All Updates, ICU, Kids, Resus

Is there nothing ketamine can't do?

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As well as the benefits of cardiovascular stability, maintenance of cerebral perfusion pressure, possibly lowering ICP and providing other neuroprotective benefits, ketamine may have other advantages. These are reviewed in a British Journal of Anaesthesia article from which I’ve selected those benefits of interest to practitioners of emergency medicine and critical care.
 

 
Additional Beneficial Effects of Ketamine

  • the dysphoric, or ’emergence’ reactions associated with ketamine may be reduced by pre-administration or co-administration of sedatives, such as benzodiazepines, propofol, dexmedetomidine, or droperidol.

  • ketamine potentiates opioid analgesia in multiple settings, reducing opioid total dose and in some groups of patients reducing postoperative desaturation

  • ketamine has possible anti-inflammatory effects demonstrated in some types of surgical patients

  • ketamine may prevent awareness, recall, or both during general anaesthesia

Ketamine: new uses for an old drug?
Br J Anaesth. 2011 Aug;107(2):123-6

All Updates, PHARM, Resus, Trauma

Lateral trauma position

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Image from sjtrem.com - click for original

The tradition of transporting trauma patients to hospital in a supine position may not be the safest approach in obtunded patients with unprotected airways. The ‘solution’ of having them on an extrication board (backboard / long spine board) to enable rolling them to one side in the event of vomiting may not be practicable for limited crew numbers.
The Norwegians have been including the option of the lateral trauma position in their pre-hospital trauma life support training for some years now.
A questionnaire study demonstrates that this method has successfully been adopted by Norwegian EMS systems.
The method of application is described as:

  • Check airways (look, listen, feel).
  • Apply chin lift/jaw thrust, suction if needed.
  • Apply stiff neck collar.
  • If the patient is unresponsive, but has spontaneous respiration: Roll patient to lateral/recovery position while maintaining head/neck position.
  • Roll to side that leaves the patient facing outwards in ambulance coupé.
  • Transfer to ambulance stretcher (Scoop-stretcher, log-roll onto stretcher mattress, or use multiple helpers, lifting by patient’s clothing).
  • Support head, secure with three belts (across legs, over hip, over shoulder)
  • Manual support of head, supply oxygen, observation, suction, BVM (big valve mask) ventilation when needed.

Different options for supporting the head in the lateral position, according to questionnaire responders, include:

  • putting padding under the head, such as a pillow or similar item (81%)
  • a combination of padding and putting the head on the lower arm (7%)
  • rest the head on the lower arm alone (10%)
  • rest the head on the ground (<1%)

 


BACKGROUND: Trauma patients are customarily transported in the supine position to protect the spine. The Airway, Breathing, Circulation, Disability, and Exposure (ABCDE) principles clearly give priority to airways. In Norway, the lateral trauma position (LTP) was introduced in 2005. We investigated the implementation and current use of LTP in Norwegian Emergency Medical Services (EMS).

METHODS: All ground and air EMS bases in Norway were included. Interviews were performed with ground and air EMS supervisors. Questionnaires were distributed to ground EMS personnel.

RESULTS: Of 206 ground EMS supervisors, 201 answered; 75% reported that LTP is used. In services using LTP, written protocols were present in 67% and 73% had provided training in LTP use. Questionnaires were distributed to 3,025 ground EMS personnel. We received 1,395 (46%) valid questionnaires. LTP was known to 89% of respondents, but only 59% stated that they use it. Of the respondents using LTP, 77% reported access to written protocols. Flexing of the top knee was reported by 78%, 20% flexed the bottom knee, 81% used under head padding. Of 24 air EMS supervisors, 23 participated. LTP is used by 52% of the services, one of these has a written protocol and three arrange training.

CONCLUSIONS: LTP is implemented and used in the majority of Norwegian EMS, despite little evidence as to its possible benefits and harms. How the patient is positioned in the LTP differs. More research on LTP is needed to confirm that its use is based on evidence that it is safe and effective.

The lateral trauma position: What do we know about it and how do we use it? A cross-sectional survey of all Norwegian emergency medical services
Scand J Trauma Resusc Emerg Med. 2011 Aug 4;19:45
Open Access Full Text

Acute Med, All Updates, ICU, Kids, PHARM, Resus, Trauma

Capillary refill time

A review of capillary refill time (CRT) reveals some interesting details about this test:

  • CRT is affected by age – the upper limit of normal for neonates is 3 seconds.
  • It increases with age – one study recommended the upper limit of normal for adult women should be increased to 2.9 seconds and for the elderly to 4.5 seconds.
  • It is affected by multiple external factors (especially ambient temperature).
  • Although it is claimed to have some predictive value in the assessment of dehydration and serious infection in children, studies vary in where and for how long pressure should be applied, and there is poor interobserver reliability.

The latest (5th Edition) of the Advanced Paediatric Life Support Manual states:
‘Poor capillary refill and differential pulse volumes are neither sensitive nor specific indicators of shock in infants and children, but are useful clinical signs when used in conjunction with the other signs described‘
In my view, it is best used as a monitor of trends (in accordance with skin temperature and other markers of perfusion), rather than by placing emphasis on the exact number of seconds of a single reading. See below for a video of my perfectly happy and healthy son demonstrating a CRT of over six seconds in a cool room during an English Summer’s day.
The authors of the review caution:
Operating rooms are cold, patients are often draped, which limits access, and because most anesthetics are potent vasodilators, the use of CRT to guide practice is not justified. The possibility of a false-positive or false-negative assessment is simply too great.


Capillary refill time (CRT) is widely used by health care workers as part of the rapid, structured cardiopulmonary assessment of critically ill patients. Measurement involves the visual inspection of blood returning to distal capillaries after they have been emptied by pressure. It is hypothesized that CRT is a simple measure of alterations in peripheral perfusion. Evidence for the use of CRT in anesthesia is lacking and further research is required, but understanding may be gained from evidence in other fields. In this report, we examine this evidence and factors affecting CRT measurement. Novel approaches to the assessment of CRT are under investigation. In the future, CRT measurement may be achieved using new technologies such as digital videography or modified oxygen saturation probes; these new methods would remove the limitations associated with clinical CRT measurement and may even be able to provide an automated CRT measurement.

Capillary Refill Time: Is It Still a Useful Clinical Sign?
Anesth Analg. 2011 Jul;113(1):120-3
The Capillary Refill Video

Acute Med, All Updates, ICU, Kids, Resus

Why I don't give vasopressors in sepsis

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It’s become popular to use the term ‘vasopressors’ or just ‘pressors’ when noradrenaline/norepinephrine or even (in some places still) dopamine are given. I have resisted this trend and continue to use the term ‘vasoactive’ drugs, on the basis that the effects they produce (and that we may desire) are not limited to a pure alpha adrenergic effect on vascular tone, but they have effects on heart rate and contractility too (as well as preload through venous effects). If you don’t believe me about noradrenaline/norepinephrine, then check out one of my favourite critical care papers of all time: the CAT study.
There are of course real pressors out there – phenylephrine acts on alpha receptors, as does methoxamine. Metaraminol predominantly acts on alpha receptors but does also cause some release of noradrenaline/norepinephrine.
Why is this important? All these drugs will fix hypotension, right? Yes, they should. However should blood pressure be our main treatment goal? What we’re really interested in is organ perfusion, which depends on regional blood flow to vital organs. It’s possible that a drug could fix the measured blood pressure and give a nice ‘macroscopic’ number, while at the same time reducing cardiac output and adversely affecting regional blood flow to organs through local vasoconstrictive effects. My view is that this is more likely with pure ‘pressors’ (like phenylephrine), which is why I avoid them in septic shock and opt for catecholamine infusions (noradrenaline/norepinephrine).
This is important in my practice setting of retrieval medicine, where, prior to interfacility transport, physicians might sometimes be tempted to ‘push pressors’ peripherally rather than insert a central venous catheter and commence a catecholamine infusion. While the former approach might be more expeditious and make the vital signs chart look pretty, one wonders about what effect this is having on tissue oxygen delivery.
A fascinating review of papers on pressor physiology1 suggests these agents have the following effects:

  • conflicting data on changes in myocardial perfusion
  • increase both left and right heart afterload
  • decrease venous compliance with the potential to increase venous return although the impact of this on cardiac output is controversial
  • controversial effect on cerebral bloodflow
  • decrease bloodflow to the kidneys
  • adverse affects on gastrointestinal tract bloodflow


abstract1
Phenylephrine and methoxamine are direct-acting, predominantly α(1) adrenergic receptor (AR) agonists. To better understand their physiologic effects, we screened 463 articles on the basis of PubMed searches of “methoxamine” and “phenylephrine” (limited to human, randomized studies published in English), as well as citations found therein. Relevant articles, as well as those discovered in the peer-review process, were incorporated into this review. Both methoxamine and phenylephrine increase cardiac afterload via several mechanisms, including increased vascular resistance, decreased vascular compliance, and disadvantageous alterations in the pressure waveforms produced by the pulsatile heart. Although pure α(1) agonists increase arterial blood pressure, neither animal nor human studies have ever shown pure α(1)-agonism to produce a favorable change in myocardial energetics because of the resultant increase in myocardial workload. Furthermore, the cost of increased blood pressure after pure α(1)-agonism is almost invariably decreased cardiac output, likely due to increases in venous resistance. The venous system contains α(1) ARs, and though stimulation of α(1) ARs decreases capacitance and may transiently increase venous return, this gain may be offset by changes in afterload, venous compliance, and venous resistance. Data on the effects of α(1) stimulation in the central nervous system show conflicting changes, while experimental animal data suggest that renal blood flow is reduced by α(1)-agonists, and both animal and human data suggest that gastrointestinal perfusion may be reduced by α(1) tone.

A review of clinical articles2 reveals few evidence-based indications for true pressors. Possible situations where they may be of benefit include intraoperative hypotension, aortic stenosis, during cyanotic episodes in Tetralogy of Fallot, and some obstetric situations. In the setting of sepis, phenylephrine has been compared with noradrenaline in which an initial pilot study found a statistically significant reduction in creatinine clearance and increase in arterial lactate after initiating the phenylephrine infusion. However a subsequent randomised controlled comparison of phenylephrine with noradrenaline/norepinephrine did not show differences in cardiopulmonary performance, global oxygen transport, or regional hemodynamics, although there were only 16 patients in each group3.


abstract2
Phenylephrine is a direct-acting, predominantly α(1) adrenergic receptor agonist used by anesthesiologists and intensivists to treat hypotension. A variety of physiologic studies suggest that α-agonists increase cardiac afterload, reduce venous compliance, and reduce renal bloodflow. The effects on gastrointestinal and cerebral perfusion are controversial. To better understand the effects of phenylephrine in a variety of clinical settings, we screened 463 articles on the basis of PubMed searches of “methoxamine,” a long-acting α agonist, and “phenylephrine” (limited to human, randomized studies published in English), as well as citations found therein. Relevant articles, as well as those discovered in the peer-review process, were incorporated into this review. Phenylephrine has been studied as an antihypotensive drug in patients with severe aortic stenosis, as a treatment for decompensated tetralogy of Fallot and hypoxemia during 1-lung ventilation, as well as for the treatment of septic shock, traumatic brain injury, vasospasm status-postsubarachnoid hemorrhage, and hypotension during cesarean delivery. In specific instances (critical aortic stenosis, tetralogy of Fallot, hypotension during cesarean delivery) in which the regional effects of phenylephrine (e.g., decreased heart rate, favorable alterations in Q(p):Q(s) ratio, improved fetal oxygen supply:demand ratio) outweigh its global effects (e.g., decreased cardiac output), phenylephrine may be a rational pharmacologic choice. In pathophysiologic states in which no regional advantages are gained by using an α(1) agonist, alternative vasopressors should be sought.

These review articles reinforce my own bias against the use of pure pressors in septic shock, although clearly more clinical research is needed. I am inclined to agree with the reviewers’ concluding statement:
…in all clinical settings, phenylephrine reduces cardiac output, and in most clinical settings has been shown to significantly increase LV afterload. Thus, only in instances in which its regional effects are thought to outweigh its global effects should phenylephrine be used for the treatment of hypotension.
1. The physiologic implications of isolated alpha(1) adrenergic stimulation
Anesth Analg. 2011 Aug;113(2):284-96
2. The clinical implications of isolated alpha(1) adrenergic stimulation
Anesth Analg. 2011 Aug;113(2):297-304
3. Phenylephrine versus norepinephrine for initial hemodynamic support of patients with septic shock: a randomized, controlled trial
Crit Care. 2008;12(6):R143
Full Text available here

Acute Med, All Updates, PHARM, Resus

Pre-hospital CPAP for pulmonary oedema

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The physician-staffed mobile intensive care units of SAMU (Service d’Aide Médicale Urgente) in France provided the location for this randomised controlled trial of CPAP for acute cardiogenic pulmonary oedema.


STUDY OBJECTIVE: The purpose of this randomized controlled trial was to determine the immediate and delayed effects of noninvasive ventilation for patients in acute cardiogenic pulmonary edema (ACPE) in addition to aggressive usual care in a medical prehospital setting.

METHODS: Out-of-hospital patients in severe ACPE were eligible for the study. Patients were randomized to receive either usual care, including conventional optimal treatment with furosemide, oxygen, and high-dose boluses of isosorbide dinitrate plus oxygen, or conventional medications plus out-of-hospital continuous positive airway pressure (CPAP). The primary outcome was the treatment success defined as all of respiratory rate less than 25 breaths per minute and oxygen saturation of greater than 90% at the end of 1-hour study. Secondary end points included death during 30 days after inclusion. Lengths of intensive care unit and hospital stays were also recorded.

RESULTS: In total, 124 patients were enrolled into the study. The 2 groups had similar baseline characteristics. For the primary outcome analysis, 22 (35.5%) of 62 patients were considered as experiencing a treatment success in the usual care group vs 19 (31.7%) of 60 in the CPAP group (P = .65). Seven patients died within 30 days in the usual care group vs 6 in the CPAP group (P = .52). There were no statistically significant differences between the treatment groups for length of stay either in hospital or in the intensive care unit.

CONCLUSION: In the prehospital setting, in spite of its potential advantages for patients in ACPE, CPAP may not be preferred to a strict optimal intravenous treatment.

Continuous positive airway pressure for cardiogenic pulmonary edema: a randomized study
Am J Emerg Med. 2011 Sep;29(7):775-81

All Updates, Guidelines, PHARM, Resus, Trauma

Prehospital Spine Immobilisation for Penetrating Trauma

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The Executive Committee of Prehospital Trauma Life Support, comprised of surgeons, emergency physicians, and paramedics, has reviewed the literature and produced the following recommendations on Prehospital Spine Immobilisation for Penetrating Trauma:


PHTLS Recommendations

  • There are no data to support routine spine immobilization in patients with penetrating trauma to the neck or torso.
  • There are no data to support routine spine immobilization in patients with isolated penetrating trauma to the cranium.
  • Spine immobilization should never be done at the expense of accurate physical examination or identification and correction of life-threatening conditions in patients with penetrating trauma.
  • Spinal immobilization may be performed after penetrating injury when a focal neurologic deficit is noted on physical examination although there is little evidence of benefit even in these cases.

Prehospital Spine Immobilization for Penetrating Trauma—Review and Recommendations From the Prehospital Trauma Life Support Executive Committee
Journal of Trauma-Injury Infection & Critical Care September 2011;71(3):763-770

All Updates, PHARM, Resus, Trauma

Pre-hospital thoracotomy

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The London Helicopter Emergency Medical Service provides a physician / paramedic team to victims of trauma. One of the interventions performed by their physicians is pre-hospital resuscitative thoracotomy to patients with cardiac arrest due to penetrating thoracic trauma. They have published the outcomes from this procedure over a 15 year period which show an 18% survival to discharge rate, with a high rate of neurologically intact survivors1.
The article was submitted for publication on February 1, 2010, and in the discussion mentions a further two survivors from the procedure performed after conducting the study. It is likely therefore in the year and a half since submission still more patients have been saved. It will be interesting to read future reports from this team as the numbers accumulate; penetrating trauma missions are sadly increasing in frequency.
Having worked for these guys and performed this procedure in the field a few times myself, I can attest to the training and governance surrounding this system. The technique of clamshell thoracotomy is well described 2 and one I would recommend for the non-surgeon.

BACKGROUND: Prehospital cardiac arrest associated with trauma almost always results in death. A case of survival after prehospital thoracotomy was published in 1994 and several others have followed. This article describes the result of prehospital thoracotomy in a physician-led system for patients with stab wounds to the chest who suffered cardiac arrest on scene.
METHODS: A 15-year retrospective prehospital trauma database review identified victims of stab wounds to the chest who suffered cardiac arrest on scene and had thoracotomy performed according to local standard operating procedures.
RESULTS: Overall, 71 patients met inclusion criteria. Thirteen patients (18%) survived to hospital discharge. Neurologic outcome was good in 11 patients and poor in 2. Presenting cardiac rhythm was asystole in four patients, pulseless electrical activity in five, and unrecorded in the remaining four. All survivors had cardiac tamponade. The medical team was present at the time of cardiac arrest for six survivors (good neurologic outcome): arrived in the first 5 minutes after arrest in three patients (all good neurologic outcome), arrived 5 minutes to 10 minutes after arrest in two patients (one poor neurologic outcome), and in one patient (poor neurologic outcome) the period was unknown. Of the survivors, seven thoracotomies were performed by emergency physicians and six by anesthesiologists.
CONCLUSIONS: Prehospital thoracotomy is a well-established procedure in this physician-led prehospital service. Results from this and other similar systems suggest that when performed for the subgroup of patients described, significant numbers of survivors with good neurologic outcome can be expected.

1. Thirteen Survivors of Prehospital Thoracotomy for Penetrating Trauma: A Prehospital Physician-Performed Resuscitation Procedure That Can Yield Good Results
J Trauma. 2011 May;70(5):E75-8
2. Emergency thoracotomy: “how to do it”
Emerg Med J. 2005 January; 22(1):22–24
Full text available here

All Updates, PHARM, Resus, Trauma

Exsanguinating cardiac arrest not always fatal

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The British Military has developed a reputation for aggressive pre-hospital critical care including (but not limited to) the use of blood products and tourniquets, and coordinated field hospital trauma care. They now report the outcomes for patients with traumatic cardiac arrest, mainly from improvised explosive devices. Of 52 patients, 14 (27%) demonstrated return of spontaneous circulation (ROSC), of whom four (8%) survived to hospital discharge with a neurologically good recovery. Resuscitative thoracotomy (RT) was performed on 12 patients (8 in the ED), including all four survivors. RT enabled open-chest CPR, release of pericardial tamponade, lung resection and compression of the descending thoracic aorta for haemorrhage control.
No patients who arrested in the field survived, although one of the neurologically well-recovered survivors arrested during transport to hospital and was in cardiac arrest for 24 minutes. The authors propose this individual’s survival was in part due to ‘the high level of care that he received during retrieval, including haemorrhage control, tracheal intubation and transfusion of blood products‘.
Asystole was universally associated with death but agonal / bradycardic rhythms were not. In keeping with other studies, cardiac activity on ultrasound was associated with ROSC.


AIM: To determine the characteristics of military traumatic cardiorespiratory arrest (TCRA), and to identify factors associated with successful resuscitation.

METHODS: Data was collected prospectively for adult casualties suffering TCRA presenting to a military field hospital in Helmand Province, Afghanistan between 29 November 2009 and 13 June 2010.

RESULTS: Data was available for 52 patients meeting the inclusion criteria. The mean age (range) was 25 (18-36) years. The principal mechanism of injury was improvised explosive device (IED) explosion, the lower limbs were the most common sites of injury and exsanguination was the most common cause of arrest. Fourteen (27%) patients exhibited ROSC and four (8%) survived to discharge. All survivors achieved a good neurological recovery by Glasgow Outcome Scale. Three survivors had arrested due to exsanguination and one had arrested due to pericardial tamponade. All survivors had arrested after commencing transport to hospital and the longest duration of arrest associated with survival was 24min. All survivors demonstrated PEA rhythms on ECG during arrest. When performed, 6/24 patients had ultrasound evidence of cardiac activity during arrest; all six with cardiac activity subsequently exhibited ROSC and two survived to hospital discharge.

CONCLUSION: Overall rates of survival from military TCRA were similar to published civilian data, despite military TCRA victims presenting with high Injury Severity Scores and exsanguination due to blast and fragmentation injuries. Factors associated with successful resuscitation included arrest beginning after transport to hospital, the presence of electrical activity on ECG, and the presence of cardiac movement on ultrasound examination.

Outcomes following military traumatic cardiorespiratory arrest: A prospective observational study
Resuscitation. 2011 Sep;82(9):1194-7