Category Archives: ICU

Stuff relevant to patients on ICU

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

Salt or sugar on the brain

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A meta-analysis suggests hypertonic saline may be more effective at lowering intracranial pressure than mannitol. An accompanying editorial cleverly entitled ‘Salt or sugar on the brain: Does it matter except for taste?’ suggests one reason hypertonic saline (HTS) has not replaced mannitol in clinical practice is that too many different regimens of HTS, in terms of concentration, dose, bolus vs. continuous infusions, and plus or minus supplementation of colloids, have been utilised. Because only 112 patients with 184 episodes of increased ICP were treated with each medication in this meta-analysis, the editorialist agrees with the authors in suggesting a larger randomised study is needed.

OBJECTIVES: Randomized trials have suggested that hypertonic saline solutions may be superior to mannitol for the treatment of elevated intracranial pressure, but their impact on clinical practice has been limited, partly by their small size. We therefore combined their findings in a meta-analysis.
DATA SOURCES: We searched for relevant studies in MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and ISI Web of Knowledge.
STUDY SELECTION: Randomized trials were included if they directly compared equiosmolar doses of hypertonic sodium solutions to mannitol for the treatment of elevated intracranial pressure in human subjects undergoing quantitative intracranial pressure measurement.
DATA EXTRACTION: Two investigators independently reviewed potentially eligible trials and extracted data using a preformed data collection sheet. Disagreements were resolved by consensus or by a third investigator if needed. We collected data on patient demographics, type of intracranial pathology, baseline intracranial pressure, osms per treatment dose, quantitative change in intracranial pressure, and prespecified adverse events. Our primary outcome was the proportion of successfully treated episodes of elevated intracranial pressure.
DATA SYNTHESIS: Five trials comprising 112 patients with 184 episodes of elevated intracranial pressure met our inclusion criteria. In random-effects models, the relative risk of intracranial pressure control was 1.16 (95% confidence interval, 1.00-1.33), and the difference in mean intracranial pressure reduction was 2.0 mm Hg (95% confidence interval, -1.6 to 5.7), with both favoring hypertonic saline over mannitol. A mild degree of heterogeneity was present among the included trials. There were no significant adverse events reported.
CONCLUSIONS: We found that hypertonic saline is more effective than mannitol for the treatment of elevated intracranial pressure. Our meta-analysis is limited by the small number and size of eligible trials, but our findings suggest that hypertonic saline may be superior to the current standard of care and argue for a large, multicenter, randomized trial to definitively establish the first-line medical therapy for intracranial hypertension.

Hypertonic saline versus mannitol for the treatment of elevated intracranial pressure: A meta-analysis of randomized clinical trials
Crit Care Med. 2011 Mar;39(3):554-9

All Updates, ICU, Resus

Norepinephrine increases preload

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Noradrenaline (norepinephrine) may improve blood pressure in part through its venoconstriction effects, providing more venous return to the heart which increases cardiac output. A study of septic shock patients supports this.
An accompanying editorial by Drs Milzman and Napoli comments: “This study tells us something we probably already knew, that norepinephrine (NE) has the ability to provide venoconstriction, increase central venous pressure, provide a marginal increase in cardiac output, and improve the MAP in patients with septic shock. Importantly, it also demonstrates that Passive Leg Raise (PLR) continues to be a good predictor of preload responsiveness even in the presence of low doses of NE.”

OBJECTIVE: To assess the effects of norepinephrine on cardiac preload, cardiac index, and preload dependency during septic shock.
DESIGN: Prospective interventional study.
SETTING: Medical Intensive Care Unit.
PATIENTS: We included 25 septic shock patients (62 ± 13 yrs old, Simplified Acute Physiology Score II 53 ± 12, lactate 3.5 ± 2.1 mmol/L, all receiving norepinephrine at baseline at 0.24 [25%-75% interquartile range: 0.12-0.48] μg/kg/min) with a positive passive leg raising test (defined by an increase in cardiac index ≥10%) and a diastolic arterial pressure ≤40 mm Hg.
INTERVENTIONS: We performed a passive leg raising test (during 1 min) at baseline. Immediately after, we increased the dose of norepinephrine (to 0.48 [0.36-0.71] μg/kg/min) and, when the hemodynamic status was stabilized, we performed a second passive leg raising test (during 1 min). We finally infused 500 mL saline.
MEASUREMENTS AND MAIN RESULTS: Increasing the dose of norepinephrine significantly increased central venous pressure (+23% ± 12%), left ventricular end-diastolic area (+9% ± 6%), E mitral wave (+19% ± 23%), and global end-diastolic volume (+9% ± 6%). Simultaneously, cardiac index significantly increased by 11% ± 7%, suggesting that norepinephrine had recruited some cardiac preload reserve. The second passive leg raising test increased cardiac index to a lesser extent than the baseline test (13% ± 8% vs. + 19% ± 6%, p < .05), suggesting that norepinephrine had decreased the degree of preload dependency. Volume infusion significantly increased cardiac index by 26% ± 15%. However, cardiac index increased by <15% in four patients (fluid unresponsive patients) while the baseline passive leg raising test was positive in these patients. In three of these four patients, the second passive leg raising test was also negative, i.e., the second passive leg raising test (after norepinephrine increase) predicted fluid responsiveness with a sensitivity of 95 [76-99]% and a specificity of 100 [30-100]%.
CONCLUSIONS: In septic patients with a positive passive leg raising test at baseline suggesting the presence of preload dependency, norepinephrine increased cardiac preload and cardiac index and reduced the degree of preload dependency.

Norepinephrine increases cardiac preload and reduces preload dependency assessed by passive leg raising in septic shock patients
Crit Care Med 2011;39(4):689-94

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

Cardiac arrest drugs and pupils

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Although not predictive immediately post-cardiac arrest in the emergency department, dilated unreactive pupils two or three days later on the ICU may indicate a hopeless prognosis. We know from our experience with adrenaline (epinephrine) infusions that this drug does not prevent pupils from reacting to light, but what about atropine?

A letter by Dr Sophie MacDougall-Davis in Resuscitation describes a 66 year old male patient admitted to the ICU after an intraoperative PEA arrest during which he received 3 mg intravenous atropine. Post arrest and post anaesthesia he was awake with no neurological deficit, but eight hours after the cardiac arrest his pupils remained fixed and dilated, and were dilated with only a very slight reaction the next morning and remained sluggish at forty-eight hours, normalising at seventy-two hours. A possible reason for its prolonged action may be uptake of atropine from the plasma into the aqueous humor of the eye, followed by its slow release.
Dr MacDougall-Davis cautions:

When assessing pupils in comatose cardiac arrest survivors, the potential for atropine to have a prolonged effect on pupil size and reactivity should be considered.

Atropine, fixed dilated pupils and prognostication following cardiac arrest
Resuscitation. 2011 Feb;82(2):232

All Updates, ICU, Resus

Video laryngoscope successes and failures

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With a difficult airway, video laryngoscopes can get you out of a hole – or rather into one. However they’re not guaranteed for all eventualities; a large study of Glidescope use showed:

  • Primary intubation with the Glidescope was successful in 98% of 1,755 cases and rescued failed direct laryngoscopy in 94% of 239 cases.
  • Altered neck anatomy with presence of a surgical scar, radiation changes, or mass was the strongest predictor of Glidescope failure.

 

 

INTRODUCTION: The Glidescope video laryngoscope has been shown to be a useful tool to improve laryngeal view. However, its role in the daily routine of airway management remains poorly characterized.
METHODS: This investigation evaluated the use of the Glidescope at two academic medical centers. Electronic records from 71,570 intubations were reviewed, and 2,004 cases were identified where the Glidescope was used for airway management. We analyzed the success rate of Glidescope intubation in various intubation scenarios. In addition, the incidence and character of complications associated with Glidescope use were recorded. Predictors of Glidescope intubation failure were determined using a logistic regression analysis.
RESULTS: Overall success for Glidescope intubation was 97% (1,944 of 2,004). As a primary technique, success was 98% (1,712 of 1,755), whereas success in patients with predictors of difficult direct laryngoscopy was 96% (1,377 of 1,428). Success for Glidescope intubation after failed direct laryngoscopy was 94% (224 of 239). Complications were noticed in 1% (21 of 2,004) of patients and mostly involved minor soft tissue injuries, but major complications, such as dental, pharyngeal, tracheal, or laryngeal injury, occurred in 0.3% (6 of 2,004) of patients. The strongest predictor of Glidescope failure was altered neck anatomy with presence of a surgical scar, radiation changes, or mass.
CONCLUSION: These data demonstrate a high success rate of Glidescope intubation in both primary airway management and rescue-failed direct laryngoscopy. However, Glidescope intubation is not always successful and certain predictors of failure can be identified. Providers should maintain their competency with alternate methods of intubation, especially for patients with neck pathology.

Routine Clinical Practice Effectiveness of the Glidescope in Difficult Airway Management
Anesthesiology. 2011 Jan;114(1):34-41

All Updates, ICU, Resus

Anaesthesia's dirty laundry – let's all learn from it

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NAP4 is here! Is that good? Yes. Why? Because it’s the long awaited 4th National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society in the United Kingdom – a multi-phase national survey that was designed to answer the questions;

  • What types of airway device are used during anaesthesia and how often?
  • How often do major complications, leading to serious harm, occur in association with airway management in anaesthesia, in the intensive care units and in the emergency departments of the UK?
  • What is the nature of these events and what can we learn from them, in order to reduce their frequency and consequences?

The Audit identified 33 deaths and 46 cases of death or brain damage as a result of airway complications during anaesthesia, in ICU and the emergency department over a one year period in the four countries of the United Kingdom.

Some major findings include:

  • Poor planning contributed to poor airway outcomes – often a failure to plan for failure.
  • The project identified numerous cases where awake fibreoptic intubation (afoi) was indicated but was not used. A lack of suitable equipment was prevalent on ICU.
  • Problems arose when difficult intubation was managed by multiple repeat attempts at intubation.
  • Events were reported where supraglottic airway devices (SAD) were used inappropriately. Patients who were markedly obese, often managed by junior trainees, were prominent in the group of patients who sustained non-aspiration events. Numerous cases of aspiration occurred during use of a first generation SAD in patients who had multiple risk factors for aspiration and in several in whom the aspiration risk was so high that rapid sequence induction, should have been used.
  • The proportion of obese patients in case reports submitted to NAP4 was twice that in the general population
  • When rescue techniques were necessary in obese patient they failed more often than in the non-obese.

Here’s my favourite bit so far – in keeping with what the literature has already told us about this technique:

There was a high failure rate of emergency cannula cricothyroidotomy, approximately 60%. There were numerous mechanisms of failure and the root cause was not determined; equipment, training, insertion technique and ventilation technique all led to failure. In contrast a surgical technique for emergency surgical airway was almost universally successful. The technique of cannula cricothyroidotomy needs to be taught and performed to the highest standards to maximise the chances of success, but the possibility that it is intrinsically inferior to a surgical technique should also be considered. Anaesthetists should be trained to perform a surgical airway.

  • failure to correctly interpret a capnograph trace led to several oesophageal intubations going unrecognised in anaesthesia. A flat capnograph trace indicates lack of ventilation of the lungs: the tube is either not in the trachea or the airway is completely obstructed. Active efforts should be taken to positively exclude these diagnoses. This applies equally in cardiac arrest as CPR leads to an attenuated but visible expired carbon dioxide trace.
  • at least one in four major airway events reported to NAP4 was from ICU or the emergency department. The outcome of these events was more likely to lead to permanent harm or death than events in anaesthesia. Analysis of the cases identified gaps in care that included: poor identification of at-risk patients, poor or incomplete planning, inadequate provision of skilled staff and equipment to manage these events successfully, delayed recognition of events and failed rescue due to lack of or failure of interpretation of capnography. The project findings suggest avoidable deaths due to airway complications occur in ICU and the emergency department.

ICU

  • failure to use capnography in ventilated patients likely contributed to more than 70% of ICU related deaths. Increasing use of capnography on ICU is the single change with the greatest potential to prevent deaths such as those reported to NAP4.
  • Displaced tracheostomy, and to a lesser extent displaced tracheal tubes, were the greatest cause of major morbidity and mortality in ICU. Obese patients were at particular risk of such events and adverse outcome from them. All patients on ICU should have an emergency re-intubation plan.

 
ED

  • Most events in the emergency department were complications of rapid sequence induction. This was also an area of concern in ICU. RSI outside the operating theatre requires the same level of equipment and support as is needed during anaesthesia. This includes capnography and access for equipment needed to manage routine and difficult airway problems.

These are just snippets – there is much more in the report, and I’m still going through it.
The Executive Summary and all other Sections of NAP4 can be downloaded here from the Royal College of Anaesthetists
 

All Updates, ICU, Resus

Longer apnoea time with roc in the obese too

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Suxamethonium increases muscle oxygen consumption as a result of skeletal muscle fasciculation. In a comparison between sux and rocuronium in rapid sequence intubation, this resulted in faster desaturation in the sux group. A further study demonstrates a similar finding in obese patients.

BACKGROUND: Rapid sequence induction may be associated with hypoxemia. The purpose of this study was to investigate the possible difference in desaturation during rapid sequence induction in overweight patients using either succinylcholine or rocuronium.
METHODS: Sixty patients with a body mass index (BMI) between 25 and 30 kg/m², American Society of Anesthesiologists class I or II, undergoing general anesthesia were randomly divided into a succinylcholine group and a rocuronium group. After a 3-min preoxygenation, patients received rapid sequence induction of general anesthesia with midazolum-fentanyl-propofol and succinylcholine (1.5 mg/kg) or rocuronium (0.9 mg/kg). Ventilation was not initiated until oxygen saturation declined to 92%. We measured the times when oxygen saturation reached 98%, 96%, 94% and 92%. Safe Apnea Time was defined as the time from administration of neuromuscular blocking drugs to oxygen saturation fell to 92%. The recovery period was defined as the time from initiation of ventilation until oxygen saturation was 97%. Arterial blood gases were taken at baseline, after preoxygenation and at 92% oxygen saturation.
RESULTS: The mean Safe Apnea Time (95% CI) was 283 (257-309) s in succinylcholine vs. 329 (303-356) s in rocuronium (P=0.01). The mean recovery period (95% CI) was 43 (39-48) s in succinylcholine vs. 36 (33-38) s in rocuronium (P=0.002). Blood gas analysis showed no difference between the two groups.
CONCLUSIONS: Succinylcholine was associated with a significantly more rapid desaturation and longer recovery of oxygen saturation than rocuronium during rapid sequence induction in overweight patients.

Desaturation following rapid sequence induction using succinylcholine vs. rocuronium in overweight patients
Acta Anaesthesiol Scand. 2011 Feb;55(2):203-8

All Updates, ICU, PHARM, Resus, Trauma, Ultrasound

Pre-hospital transcranial Doppler

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The SAMU (Service d’aide médicale urgente) guys have had a run of interesting pre-hospital publications lately. In this study, one of their ultrasound-wielding physicians travelled in a car to meet comatose head injured patients in a large semi-rural territory area with up to a 120–160-min transport time to a hospital with emergency neurosurgical capability. Pre-hospital transcranial Doppler was done, the results of which appear to have influenced treatment decisions, including the pre-hospital administration of noradrenaline (norepinephrine). I think this study has answered the ‘can it be done?’ question, but further work is needed to determine whether it really makes a difference to outcome.

Background: Investigation of the feasibility and usefulness of pre-hospital transcranial Doppler (TCD) to guide early goal-directed therapy following severe traumatic brain injury (TBI).
Methods: Prospective, observational study of 18 severe TBI patients during pre-hospital medical care. TCD was performed to estimate cerebral perfusion in the field and upon arrival at the Level 1 trauma centre. Specific therapy (mannitol, noradrenaline) aimed at improving cerebral perfusion was initiated if the initial TCD was abnormal (defined by a pulsatility index >1.4 and low diastolic velocity).
Results: Nine patients had a normal initial TCD and nine an abnormal one, without a significant difference between groups in terms of the Glasgow Coma Scale or the mean arterial pressure. Among patients with an abnormal TCD, four presented with an initial areactive bilateral mydriasis. Therapy normalized TCD in five patients, with reversal of the initial mydriasis in two cases. Among these five patients for whom TCD was corrected, only two died within the first 48 h. All four patients for whom the TCD could not be corrected during transport died within 48 h. Only patients with an initial abnormal TCD required emergent neurosurgery (3/9). Mortality at 48 h was significantly higher for patients with an initial abnormal TCD.
Conclusions: Our preliminary study suggests that TCD could be used in pre-hospital care to detect patients whose cerebral perfusion may be impaired.

Pre-hospital transcranial Doppler in severe traumatic brain injury: a pilot study
Acta Anaesthesiol Scand. 2011 Apr;55(4):422-8

All Updates, ICU, PHARM, Resus

Tube tip top tip

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I’m not sure what this offers over purpose-built supraglottic airways, but effective ventilation may be achieved after failure of mask ventilation by siting a tracheal tube with its tip in the pharynx and the cuff inflated with 20 mls. The tube ‘is gently inserted 10—14cm, dependent on patient size, or until any resistance is felt, in caudal direction by letting the tip of the tube follow the palate and the posterior pharyngeal wall (in order to place the tip of the tube posterior to the epiglottis)’. As long as the tube tip or Murphy eye is not in the oesophagus, ventilation should be possible. The hand position maintains a jaw thrust while closing the mouth and occluding the nostrils.


BACKGROUND: Mask ventilation occasionally fails. Alternative readily available and simple methods to establish ventilation in these cases are needed.

METHODS: Retrospective description of cases in which a new technique, tube tip in pharynx (TTIP) ventilation, was employed for restoring ventilation in case of failed facemask ventilation during induction of anaesthesia. The technique involves a standard endotracheal tube and can be performed single-handed: A standard endotracheal tube was placed via the mouth with the tip in the pharynx and the cuff was inflated. By placing the fourth and fifth fingers below the ramus of the mandible, the third finger below the lower lip, the second finger above the upper lip and on one side of the nose and the first finger on the other side of the nose, an open airway is restored. Chin lift is inherent in the grip, thus contributing to opening of the airway.

RESULTS: In all four cases of failed mask ventilation the anaesthetist could establish an open airway and subsequent ventilation without the need for an assistant. There were no indications of gastric insufflation.

CONCLUSION: The TTIP technique established ventilation in all four patients after abandoned facemask ventilation. The technique only involves one person and an endotracheal tube and warrants to be included in the armamentarium of anaesthetists. Further prospective studies are needed to refine the technique and delimit its indications.

Tube tip in pharynx (TTIP) ventilation: simple establishment of ventilation in case of failed mask ventilation
Acta Anaesthesiol Scand. 2005 Feb;49(2):252-6

All Updates, ICU, Resus, Trauma

Fever in head injury might not be bad

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Thanks to Michael McGonigal MD for highlighting this in his excellent Trauma Professional’s Blog:

  • Body temperature does not necessarily reflect brain temperature
  • Low brain temperature was independently associated with a worse outcome in a recent study
  • Brain temperature within the range of 36.5°C to 38°C was associated with a lower probability of death in this study
  • There are no randomised studies on which to base the practice of aggressive cooling of febrile patients with traumatic brain injury

There are few prospective studies reporting the effect of spontaneous temperature changes on outcome after severe traumatic brain injury (TBI). Where studies have been conducted, results are based on systemic rather than brain temperature per se. However, body temperature is not a reliable surrogate for brain temperature. Consequently, the effect of brain temperature changes on outcome in the acute phase after TBI is not clear. Continuous intraparenchymal brain temperature was measured in consecutive admissions of severe TBI patients during the course of the first 5 days of admission to the intensive care unit (ICU). Patients received minimal temperature altering therapy during their ICU stay. Logistic regression was used to explore the relationship between the initial, the 24-h mean, and the 48-h mean brain temperature with outcome for mortality at 30 days and outcome at 3 months. Multifactorial analysis was performed to account for potential confounders. At the 24-h time point, brain temperature within the range of 36.5°C to 38°C was associated with a lower probability of death (10-20%). Brain temperature outside of this range was associated with a higher probability of death and poor 3-month neurological outcome. After adjusting for other predictors of outcome, low brain temperature was independently associated with a worse outcome. Lower brain temperatures (below 37°C) are independently associated with a higher mortality rate after severe TBI. The results suggest that, contrary to current opinion, temperatures within the normal to moderate fever range during the acute post-TBI period do not impose an additional risk for a poor outcome after severe TBI.

The effect of spontaneous alterations in brain temperature on outcome: a prospective observational cohort study in patients with severe traumatic brain injury.
J Neurotrauma. 2010 Dec;27(12):2157-64

All Updates, ICU, Kids, Resus, Ultrasound

Kids tracheal tubes – formulas galore

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An ultrasound study of paediatric airways showed sonographic measurement to be a better predictor of tracheal tube size (using a formula – derived and then validated – to estimate external tube diameter) than traditional formulae for selecting the internal tube diameter based on age. Since the measurements, taken at the lower edge of the cricoid cartilage, were made after patients were paralyzed, and were performed without ventilation or positive end-expiratory pressure to minimize fluctuation in tracheal diameter, taking about 30 seconds, this is not something I anticipate applying in critical care practice. However, the paper does provide a good opportunity to revise some of the existing formulae. They used:
(1) The Cole formula for uncuffed tubes: ID (intenal diameter) in mm= (age in years)/4 + 4
(2) The Motoyama formula for cuffed ETTs in children aged 2 yr or older: ID in mm = (age in years)/4 + 3.5
(3) The Khine formula for cuffed ETTs in children younger than 2 yr: ID in mm = (age in years)/4 + 3.0
The formula established in the study was:

  • cuffed ETT outer diameter (OD) = 0.46 x (subglottic diameter) + 1.56

  • uncuffed ETT OD = 0.55 x (subglottic diameter) + 1.16

Age in months also correlated with optimal ETT size in mm, although the correlation was weaker than for subglottic diameter:

  • cuffed ETT OD = 0.027 x (age) + 5.2

  • uncuffed ETT OD = 0.030 x (age) + 5.4

BACKGROUND: Formulas based on age and height often fail to reliably predict the proper endotracheal tube (ETT) size in pediatric patients. We, thus, tested the hypothesis that subglottic diameter, as determined by ultrasonography, better predicts optimal ETT size than existing methods.
METHODS: A total of 192 patients, aged 1 month to 6 yr, who were scheduled for surgery and undergoing general anesthesia were enrolled and divided into development and validation phases. In the development group, the optimal ETT size was selected according to standard age-based formulas for cuffed and uncuffed tubes. Tubes were replaced as necessary until a good clinical fit was obtained. Via ultrasonography, the subglottic upper airway diameter was determined before tracheal intubation. We constructed a regression equation between the subglottic upper airway diameter and the outer diameter of the ETT finally selected. In the validation group, ETT size was selected after ultrasonography using this regression equation. The primary outcome was the fraction of initial cuffed and uncuffed tube sizes, as selected through the regression formula, that proved clinically optimal.
RESULTS: Subglottic upper airway diameter was highly correlated with outer ETT diameter deemed optimal on clinical grounds. The rate of agreement between the predicted ETT size based on ultrasonic measurement and the final ETT size selected clinically was 98% for cuffed ETTs and 96% for uncuffed ETTs.
CONCLUSIONS: Measuring subglottic airway diameter with ultrasonography facilitates the selection of appropriately sized ETTs in pediatric patients. This selection method better predicted optimal outer ETT diameter than standard age- and height-based formulas.

Prediction of Pediatric Endotracheal Tube Size by Ultrasonography
Anesthesiology. 2010 Oct;113(4):819-24