Category Archives: ICU

Stuff relevant to patients on ICU

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

All Updates, ICU, PHARM, Resus, Trauma

Score to predict traumatic coagulopathy

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Acute traumatic coagulopathy (ATC) is present in up to 25% of major trauma patients by the time they arrive in hospital. A predictive tool called the coagulopathy of severe trauma (COAST) score was retrospectively derived and then prospectively validated in major trauma patients in the state of Victoria, Australia. The definition of ATC was INR > 1.5 (1.0–1.3) or aPTT of > 60 s (25–38 s) on hospital presentation.
The study claims that a subgroup of patients with acute traumatic coagulopathy can be accurately identified based on simple observations in the pre-hospital phase or immediately on presentation to the ED, and that this could improve the feasibility of prospective interventional studies. Perhaps this will lead on to evaluation of pre-hospital tranexamic acid or even blood products?
At the cutoff score of ≥3, 40 coagulopathic patients would have been missed with 60 patients correctly predicted. The authors argue that while the low sensitivity of the score missed these coagulopathic patients, they had significantly better outcomes (and contained a significantly higher proportion of patients with isolated severe head injury).


Introduction: The inability to accurately predict acute traumatic coagulopathy (ATC) has been a key factor in the low level of evidence guiding its management. The aim of this study was to develop a tool to accurately identify patients with ATC using pre-hospital variables without the use of pathology or radiological testing.

Methods: Retrospective data from the trauma registry on major trauma patients were used to identify vari- ables independently associated with coagulopathy. These variables were clinically evaluated to develop a scoring system to predict ATC, which was prospectively validated in the same setting.

Results: There were 1680 major trauma patients in the derivation dataset, with 151 patients being coagulopathic. Pre-hospital variables independently associated with ATC were entrapment (OR 1.85; 95% CI: 1.12–3.06), temperature (OR 0.60; 95% CI: 0.60–0.72), systolic blood pressure (OR 0.99; 95% CI: 0.98–0.99), abdominal or pelvic content injury (OR 2.0; 95% CI: 1.27–3.12) and pre-hospital chest decompression (OR 4.99; 2.77–8.99). The COAST score was developed, scoring points for entrapment, temperature <35 ◦ C, systolic blood pressure <100 mm Hg, abdominal or pelvic content injury and chest decompression. Prospectively validated using 1225 major trauma patients, a COAST score of ≥3 had a specificity of 96.4% with a sensitivity of 60.0%, with an area under the receiver operating characteristic curve of 0.83 (0.78–0.88).
Conclusions: The COAST score accurately identified a group of patients with ATC using pre-hospital obser- vations. This predictive tool can be used to select patients for inclusion into prospective studies examining management options for ATC. Mortality in these patients is high, potentially improving feasibility of outcome studies.

Acute Med, All Updates, Guidelines, ICU, PHARM, Resus

Still no cardiac arrest survival benefit from epinephrine?

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A double blind randomised controlled trial showed significantly better rates of return of spontaneous circulation and hospital admission with the use of adrenaline (epinephrine) compared with placebo. This effect was observed with both shockable and non-shockable initial cardiac arrest rhythms. There was no statistically significant difference in the primary outcome of survival to hospital discharge.
Interesting but unfortunate political factors appear to have prevented recruitment to the required numbers of patients for this study so it is underpowered for its primary outcome of survival to hospital discharge, which in the adrenaline group was double that in the placebo group, although this did not reach statistical significance. What was supposed to be a multi-centre study became a single centre one and it was not possible to continue as the study drugs reached their expiry date and no additional funding was available.
So do ROSC and survival to admission matter? The authors make the following point:


While not the primary outcome of our study, ROSC is an increasingly important clinical endpoint as the influence of post resuscitation care interventions (i.e.: therapeutic hypothermia, managing underlying cause, organ perfusion and oxygenation) on survival to hospital discharge are recognised.

Optimum dose and timing of adrenaline remain unknown, along with whether it impacts on long-term outcomes.


BACKGROUND: There is little evidence from clinical trials that the use of adrenaline (epinephrine) in treating cardiac arrest improves survival, despite adrenaline being considered standard of care for many decades. The aim of our study was to determine the effect of adrenaline on patient survival to hospital discharge in out of hospital cardiac arrest.

METHODS: We conducted a double blind randomised placebo-controlled trial of adrenaline in out-of-hospital cardiac arrest. Identical study vials containing either adrenaline 1:1000 or placebo (sodium chloride 0.9%) were prepared. Patients were randomly allocated to receive 1ml aliquots of the trial drug according to current advanced life support guidelines. Outcomes assessed included survival to hospital discharge (primary outcome), pre-hospital return of spontaneous circulation (ROSC) and neurological outcome (Cerebral Performance Category Score – CPC).

RESULTS: A total of 4103 cardiac arrests were screened during the study period of which 601 underwent randomisation. Documentation was available for a total of 534 patients: 262 in the placebo group and 272 in the adrenaline group. Groups were well matched for baseline characteristics including age, gender and receiving bystander CPR. ROSC occurred in 22 (8.4%) of patients receiving placebo and 64 (23.5%) who received adrenaline (OR=3.4; 95% CI 2.0-5.6). Survival to hospital discharge occurred in 5 (1.9%) and 11 (4.0%) patients receiving placebo or adrenaline respectively (OR=2.2; 95% CI 0.7-6.3). All but two patients (both in the adrenaline group) had a CPC score of 1-2.

CONCLUSION: Patients receiving adrenaline during cardiac arrest had no statistically significant improvement in the primary outcome of survival to hospital discharge although there was a significantly improved likelihood of achieving ROSC.

Effect of adrenaline on survival in out-of-hospital cardiac arrest: A randomised double-blind placebo-controlled trial
Resuscitation. 2011 Sep;82(9):1138-43

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

Pre-hospital ECMO

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Two cases are reported of the pre-hospital institution of venoarterial extracorporeal membrane oxygenation (ECMO) for patients in cardiac arrest. One was from France and the other from Germany – both countries with mature physician-staffed pre-hospital systems. The two cases were a 9 yr old drowning victim1 and a 48 year old marathon runner2. They each received BLS then ACLS then ECMO, and both went from asystole to sinus rhythm after the institution of ECMO. Sadly both failed to neurologically recover and died in hospital.
If irreversible anoxic encephalopathy could be detected in the field, patients could be better selected for this intervention. An editorialist3 states:


Until we have a hand held device which can measure neuronal integrity on a cellular level in the field we must use our best judgement, and in many cases give the patient the benefit of the doubt by cannulating them, cooling for 24 h and then making a neurological assessment and withdrawing ECLS if necessary.

Other issues to consider are:

  • Can society afford this level of intervention?
  • Could this intervention, when associated with brain death, result in sufficiently recovered organs for transplantation?
  • How can the infrastructure be created to enable rapid institution of pre-hospital ECMO?

I suspect as the equipment becomes even more portable and self-maintaining, pre-hospital / retrieval physicians already expert in critical care interventions such as seldinger-guided vascular access will be the ones instituting this therapy. In the meantime, we await evidence of outcome benefit and some objective means of case selection.
1. Out-of-hospital extracorporeal life support for cardiac arrest—A case report
Resuscitation. 2011 Sep;82(9):1243-5
2. Out-of-hospital extra-corporeal life support implantation during refractory cardiac arrest in a half-marathon runner
Resuscitation. 2011 Sep;82(9):1239-42
3. Community extracorporeal life support for cardiac arrest – When should it be used?
Resuscitation. 2011 Sep;82(9):1117

All Updates, ICU

Glutamine in ICU

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Of interest to intensivists….


Background: Low plasma glutamine concentration is an independent prognostic factor for an unfavourable outcome in the intensive care unit (ICU). Intravenous (i.v.) supplementation with glutamine is reported to improve outcome. In a multi-centric, double-blinded, controlled, randomised, pragmatic clinical trial of i.v. glutamine supplementation for ICU patients, we investigated outcomes regarding sequential organ failure assessment (SOFA) scores and mortality. The hypothesis was that the change in the SOFA score would be improved by glutamine supplementation.

Methods: Patients (n=413) given nutrition by an enteral and/or a parenteral route with the aim of providing full nutrition were included within 72 h after ICU admission. Glutamine was supplemented as i.v. l-alanyl-l-glutamine, 0.283 g glutamine/kg body weight/24 h for the entire ICU stay. Placebo was saline in identical bottles. All included patients were considered as intention-to-treat patients. Patients given supplementation for >3 days were considered as predetermined per protocol (PP) patients.

Results: There was a lower ICU mortality in the treatment arm as compared with the controls in the PP group, but not at 6 months. For change in the SOFA scores, no differences were seen, 1 (0,3) vs. 2 (0.4), P=0.792, for the glutamine group and the controls, respectively.

Conclusion: In summary, a reduced ICU mortality was observed during i.v. glutamine supplementation in the PP group. The pragmatic design of the study makes the results representative for a broad range of ICU patients.

Scandinavian glutamine trial: a pragmatic multi-centre randomised clinical trial of intensive care unit patients
Acta Anaesthesiol Scand. 2011 Aug;55(7):812-818

Acute Med, All Updates, ICU, Resus

Nitric oxide for right ventricular cardiogenic shock

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A case report describes a patient with right ventricular cardiogenic shock due to a dissected right coronary artery1. There was deterioration despite fluid, inotropic and intraaortic balloon pump therapy, followed by improvement with the introduction of inhaled nitric oxide (iNO) at 12 to 15 ppm (a selective pulmonary vasodilator), to the point where vasoactive medication was withdrawn. The cessation of iNO was associated with deterioration which resolved with its reintroduction. It was more gradually withdrawn and the patient made a good recovery.
The rationale for the use of iNO in patients with acute RV heart failure due to MI is afterload reduction without systemic hypotension.
It has been shown to improve haemodynamics in RV MI patients with cardiogenic shock in a previous case series2 (abstract below) in which its effects on pulmonary vasodilation are thought be beneficial. In RV MI with shock increased pulmonary vascular tone is postulated to result from the following mechanisms:

  • A low cardiac output results in a decreased mixed venous blood oxygen content, which enhances pulmonary artery vasoconstriction.
  • The intravenous infusion of alpha-adrenergic vasoconstrictors can contribute to pulmonary vasoconstriction.
  • Mechanical ventilation with positive end-expiratory pressure can increase the pulmonary vascular resistance through compression of the pulmonary vasculature.
  • Interstitial pulmonary edema, which may occur in some patients with coexisting LV dysfunction, can also cause pulmonary constriction

OBJECTIVES: We sought to determine whether or not inhaled nitric oxide (NO) could improve hemodynamic function in patients with right ventricular myocardial infarction (RVMI) and cardiogenic shock (CS).

BACKGROUND: Inhaled NO is a selective pulmonary vasodilator that can decrease right ventricular afterload.

METHODS: Thirteen patients (7 males and 6 females, age 65 +/- 3 years) presenting with electrocardiographic, echocardiographic, and hemodynamic evidence of acute inferior myocardial infarction associated with RVMI and CS were studied. After administration of supplemental oxygen (inspired oxygen fraction [F(i)O(2)] = 1.0), hemodynamic measurements were recorded before, during inhalation of NO (80 ppm at F(i)O(2) = 0.90) for 10 min, and 10 min after NO inhalation was discontinued (F(i)O(2) = 1.0).

RESULTS: Breathing NO decreased the mean right atrial pressure by 12 +/- 3%, mean pulmonary arterial pressure by 13 +/- 2%, and pulmonary vascular resistance by 36 +/- 8% (all p < 0.05). Nitric oxide inhalation increased the cardiac index by 24 +/- 11% and the stroke volume index by 23 +/- 12% (p < 0.05). The NO administration did not change systemic arterial or pulmonary capillary wedge pressures. Contrast echocardiography identified three patients with a patent foramen ovale and right-to-left shunt flow while breathing at F(i)O(2) = 1.0. Breathing NO decreased shunt flow by 56 +/- 5% (p < 0.05) and was associated with markedly improved systemic oxygen saturation.

CONCLUSIONS: Nitric oxide inhalation results in acute hemodynamic improvement when administered to patients with RVMI and CS.

1. Use of inhaled nitric oxide in the treatment of right ventricular myocardial infarction
Am J Emerg Med. 2011 May;29(4):473.e3-5
2. Hemodynamic effects of inhaled nitric oxide in right ventricular myocardial infarction and cardiogenic shock
J Am Coll Cardiol. 2004 Aug 18;44(4):793-8

All Updates, ICU, Resus, Ultrasound

Ultrasound to detect difficult laryngoscopy

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A pilot study suggests sonographic measurements of neck soft tissue thickness may predict difficult laryngoscopy. Laryngoscopy was difficult in patients with increased thickness of the anterior neck soft tissue at the level of the hyoid bone and thyrohyoid membrane. The authors suggest that anterior neck soft tissue thickness cutoff value of 2.8 cm at the thyrohyoid membrane level can potentially be used to detect difficult laryngoscopy, but that this would require further validation since in this pilot study there were only six subjects in the difficult laryngoscopy group.


Objectives:  Prediction of difficult laryngoscopy in emergency care settings is challenging. The preintubation clinical screening tests may not be applied in a large number of emergency intubations due to the patient’s clinical condition. The objectives of this study were 1) to determine the utility of sonographic measurements of thickness of the tongue, anterior neck soft tissue at the level of the hyoid bone, and thyrohyoid membrane in distinguishing difficult and easy laryngoscopies and 2) to examine the association between sonographic measurements (thickness of tongue and anterior neck soft tissue) and difficult airway clinical screening tests (modified Mallampati score, thyromental distance, and interincisor gap).

Methods:  This was a prospective observational study at an academic medical center. Adult patients undergoing endotracheal intubation for an elective surgical procedure were included. The investigators involved in data collection were blinded to each other’s assessments. Demographic variables were collected preoperatively. The clinical screening tests to predict a difficult airway were performed. The ultrasound (US) measurements of tongue and anterior neck soft tissue were obtained. The laryngoscopic view was graded using Cormack and Lehane classification by anesthesia providers on the day of surgery. To allow for comparisons between difficult airway and easy airway groups, a two-sided Student’s t-test and Fisher’s exact test were employed as appropriate. Spearman’s rank correlation coefficients were used to examine the association between screening tests and sonographic measurements.

Results:  The mean (±standard deviation [SD]) age of 51 eligible patients (32 female, 19 male) was 53.1 (±13.2) years. Six of the 51 patients (12%, 95% confidence interval [CI] = 3% to 20%) were classified as having difficult laryngoscopy by anesthesia providers. The distribution of laryngoscopy grades for all subjects was 63, 25, 4, and 8% for grades 1, 2, 3, and 4, respectively. In this study, 83% of subjects with difficult airways were males. No other significant differences were noted in the demographic variables and difficult airway clinical screening tests between the two groups. The sonographic measurements of anterior neck soft tissue were greater in the difficult laryngoscopy group compared to the easy laryngoscopy group at the level of the hyoid bone (1.69, 95% CI = 1.19 to 2.19 vs. 1.37, 95% CI = 1.27 to 1.46) and thyrohyoid membrane (3.47, 95% CI = 2.88 to 4.07 vs. 2.37, 95% CI = 2.29 to 2.44). No significant correlation was found between sonographic measurements and clinical screening tests.

Conclusions:  This pilot study demonstrated that sonographic measurements of anterior neck soft tissue thickness at the level of hyoid bone and thyrohyoid membrane can be used to distinguish difficult and easy laryngoscopies. Clinical screening tests did not correlate with US measurements, and US was able to detect difficult laryngoscopy, indicating the limitations of the conventional screening tests for predicting difficult laryngoscopy.

Pilot Study to Determine the Utility of Point-of-care Ultrasound in the Assessment of Difficult Laryngoscopy
Acad Emerg Med. 2011 Jul;18(7):754-8

All Updates, ICU, Resus, Ultrasound

Ultrasound-Guided Radial Artery Catheterization

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In case you needed some evidence – a systematic review supports ultrasound guidance as a means of improving insertion success of radial artery catheters


BACKGROUND: Ultrasound guidance commonly is used for the placement of central venous catheters (CVCs). The Agency for Healthcare Research and Quality recommends the use of ultrasound for CVC placement as one of its 11 practices to improve patient care. Despite increased access to portable ultrasound machines and comfort with ultrasound-guided CVC access, fewer clinicians are familiar with ultrasound-guided techniques of arterial catheterization. The goal of this systematic review and meta-analysis was to determine the utility of real-time two-dimensional ultrasound guidance for radial artery catheterization.

METHODS: A comprehensive literature search of Medline, Excerpta Medica Database, and the Cochrane Central Register of Controlled Trials by two independent reviewers identified prospective, randomized controlled trials comparing ultrasound guidance with traditional palpation techniques of radial artery catheterization. Data were extracted on study design, study size, operator and patient characteristics, and the rate of first-attempt success. A meta-analysis was constructed to analyze the data.

RESULTS: Four trials with a total of 311 subjects were included in the review, with 152 subjects included in the palpation group and 159 in the ultrasound-guided group. Compared with the palpation method, ultrasound guidance for arterial catheterization was associated with a 71% improvement in the likelihood of first-attempt success (relative risk, 1.71; 95% CI, 1.25-2.32).

CONCLUSIONS: The use of real-time two-dimensional ultrasound guidance for radial artery catheterization improved first-pass success rate.

Ultrasound-Guided Catheterization of the Radial Artery
Chest. 2011 Mar;139(3):524-9

Acute Med, All Updates, ICU, Resus

Early CT may rule out subarachnoid haemorrhage

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A multicentre Canadian study challenges the practice of routine lumbar puncture after negative CT in patients with suspected subarachnoid haemorrhage. CT scanning within six hours was highly sensitive, although a few cases of initially misinterpreted CTs “illustrate the importance of having a qualified radiologist with a high level of skill interpreting the head scans in a timely manner“.

Nearly 2% of patients were lost to all follow-up; the authors point out that even if a quarter of these patients could have experienced a subarachnoid haemorrhage, the corresponding negative likelihood ratio for a computed tomography performed within six hours rises to only 0.024 (0.007 to 0.07). They assert:

Such a likelihood ratio could be incorporated into the informed discussion surrounding the risks and benefits of lumbar puncture after negative results on computed tomography for this diagnosis

They point out that when CT imaging is obtained more than six hours after headache onset, clinicians should continue to be cautious because of the decreasing sensitivity for subarachnoid haemorrhage beyond this time.


Objective To measure the sensitivity of modern third generation computed tomography in emergency patients being evaluated for possible subarachnoid haemorrhage, especially when carried out within six hours of headache onset.

Design Prospective cohort study. Setting 11 tertiary care emergency departments across Canada, 2000-9.

Participants Neurologically intact adults with a new acute headache peaking in intensity within one hour of onset in whom a computed tomography was ordered by the treating physician to rule out subarachnoid haemorrhage.

Main outcome measures Subarachnoid haemorrhage was defined by any of subarachnoid blood on computed tomography, xanthochromia in cerebrospinal fluid, or any red blood cells in final tube of cerebrospinal fluid collected with positive results on cerebral angiography.

Results Of the 3132 patients enrolled (mean age 45.1, 2571 (82.1%) with worst headache ever), 240 had subarachnoid haemorrhage (7.7%). The sensitivity of computed tomography overall for subarachnoid
haemorrhage was 92.9% (95% confidence interval 89.0% to 95.5%), the specificity was 100% (99.9% to 100%), the negative predictive value was 99.4% (99.1% to 99.6%), and the positive predictive value was 100% (98.3% to 100%). For the 953 patients scanned within six hours of headache onset, all 121 patients with subarachnoid haemorrhage were identified by computed tomography, yielding a sensitivity of 100% (97.0% to 100.0%), specificity of 100% (99.5% to 100%), negative predictive value of 100% (99.5% to 100%), and positive predictive value of 100% (96.9% to 100%).

Conclusion Modern third generation computed tomography is extremely sensitive in identifying subarachnoid haemorrhage when it is carried out within six hours of headache onset and interpreted by a qualified radiologist

Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study
BMJ. 2011 Jul 18;343:d4277