Tag Archives: monitoring

Tympanic monitoring for targeted temperature management

As the authors of this study point out, the reliability of tympanic temperature monitoring is still under debate. Since invasive measures of core temperature employed in the ICU may not be practicable in the pre-hospital setting, it would be helpful to employ a simpler method in the field, particular if we are implementing targeted temperature management post-cardiac arrest. In this small study of ten patients (with 558 temperature measurements) there was a high degree of correlation between tympanic and oesophageal temperature (r=0.95, p<0.0001, 95% CI 0.93 to 0.96) and also between tympanic and bladder temperature (r=0.96, p<0.0001, 95% CI 0.95 to 0.97). This finding is apparently in keeping with results obtained from patients undergoing cardiac surgery.

Objective Prehospital induction of therapeutic hypothermia after cardiac arrest may require temperature monitoring in the field. Tympanic temperature is non-invasive and frequently used in clinical practice. Nevertheless, it has not yet been evaluated in patients undergoing mild therapeutic hypothermia (MTH). Therefore, a prospective observational study was conducted comparing three different sites of temperature monitoring during therapeutic hypothermia.
Methods Ten consecutive patients admitted to our medical intensive care unit after out-of-hospital cardiac arrest were included in this study. During MTH, tympanic temperature was measured using a digital thermometer. Simultaneously, oesophageal and bladder temperatures were recorded in a total of 558 single measurements.
Results Compared with oesophageal temperature, bladder temperature had a bias of 0.019°C (limits of agreement ±0.61°C (2SD)), and tympanic measurement had a bias of 0.021°C (±0.80°C). Correlation analysis revealed a high relationship for tympanic versus oesophageal temperature (r=0.95, p<0.0001) and also for tympanic versus bladder temperature (r=0.96, p<0.0001).
Conclusions That tympanic temperature accurately indicates both oesophageal and bladder temperatures with a very small discrepancy in patients undergoing MTH after cardiac arrest is demonstrated in this study. Although our results were obtained in the hospital setting, these findings may be relevant for the prehospital application of therapeutic hypothermia as well. In this case, tympanic temperature may provide an easy and non-invasive method for temperature monitoring.

Tympanic temperature during therapeutic hypothermia
Emerg Med J. 2011 Jun;28(6):483-5

Targeted temperature management guidelines


Okay – rather than ‘therapeutic hypothermia’, the recommended phrase now is ‘targeted temperature management’. Several critical care authorities got together to produce clinical recommendations on this topic. Here are a few interesting points from the document:
On coagulation:
Hypothermia affects platelet function and prolongs the prothrombin time and partial thromboplastin time. These effects are masked when laboratory analysis is performed at 37°C, suggesting that any risk will be mitigated by rewarming.
Although not mentioned in the abstract, the authors examined the role of TTM in raised intracranial pressure (ICP):
Sufficient evidence exists to conclude that TTM does decrease ICP compared to unstructured temperature management. However, there is no sufficient evidence to make a recommendation regarding the use of targeted hypothermia to control elevated ICP to improve patent-important outcomes in TBI. The jury makes NO RECOMMENDATION regarding the use of TTM as an ICP control strategy to improve outcomes in brain injuries regardless of cause (trauma, hemorrhage, or ischemic stroke).
Regarding acute liver failure with severe cerebral edema:
there are currently no RCTs. There is a case series suggesting a strongly favorable effect. This is a powerful argument for support of an RCT evaluating TTM alone or in combination with hepatic dialysis strategies

OBJECTIVE: Representatives of five international critical care societies convened topic specialists and a nonexpert jury to review, assess, and report on studies of targeted temperature management and to provide clinical recommendations.
DATA SOURCES: Questions were allocated to experts who reviewed their areas, made formal presentations, and responded to questions. Jurors also performed independent searches. Sources used for consensus derived exclusively from peer-reviewed reports of human and animal studies.
STUDY SELECTION: Question-specific studies were selected from literature searches; jurors independently determined the relevance of each study included in the synthesis.
CONCLUSIONS AND RECOMMENDATIONS:

  1. The jury opines that the term “targeted temperature management” replace “therapeutic hypothermia.”
  2. The jury opines that descriptors (e.g., “mild”) be replaced with explicit targeted temperature management profiles.
  3. The jury opines that each report of a targeted temperature management trial enumerate the physiologic effects anticipated by the investigators and actually observed and/or measured in subjects in each arm of the trial as a strategy for increasing knowledge of the dose/duration/response characteristics of temperature management. This enumeration should be kept separate from the body of the report, be organized by body systems, and be made without assertions about the impact of any specific effect on the clinical outcome.
  4. The jury STRONGLY RECOMMENDS targeted temperature management to a target of 32°C-34°C as the preferred treatment (vs. unstructured temperature management) of out-of-hospital adult cardiac arrest victims with a first registered electrocardiography rhythm of ventricular fibrillation or pulseless ventricular tachycardia and still unconscious after restoration of spontaneous circulation (strong recommendation, moderate quality of evidence).
  5. The jury WEAKLY RECOMMENDS the use of targeted temperature management to 33°C-35.5°C (vs. less structured management) in the treatment of term newborns who sustained asphyxia and exhibit acidosis and/or encephalopathy (weak recommendation, moderate quality of evidence).

Targeted temperature management in critical care: A report and recommendations from five professional societies
Crit Care Med. 2011 May;39(5):1113-1125

Colorimetric CO2 detectors and newborns

Colorimetric CO2 detectors may fail to indicate successful tracheal tube placement in adults in certain circumstances, such as low cardiac output states, and waveform capnography is considered the gold standard. We now have data that demonstrate their inadequacy for neonatal intubation. Ideally, waveform devices should be used by all professionals who intubate patients – from paramedics to neonatologists.

AIM: Clinical assessment and end-tidal CO(2) (ETCO(2)) detectors are routinely used to verify endotracheal tube (ETT) placement. However, ETCO(2) detectors may mislead clinicians by failing to identify correct placement under a variety of conditions. A flow sensor measures gas flow in and out of an ETT. We reviewed video recordings of neonatal resuscitations to compare a colorimetric CO(2) detector (Pedi-Cap®) with flow sensor recordings for assessing ETT placement.
METHODS: We reviewed recordings of infants <32 weeks gestation born between February 2007 and January 2010. Airway pressures and gas flow were recorded with a respiratory function monitor. Video recording were used (i) to identify infants who were intubated in the delivery room and (ii) to observe colour change of the ETCO(2) detector. Flow sensor recordings were used to confirm whether the tube was in the trachea or not. RESULTS: Of the 210 infants recorded, 44 infants were intubated in the delivery room. Data from 77 intubation attempts were analysed. In 35 intubations of 20 infants both a PediCap® and flow sensor were available for analysis. In 21 (60%) intubations, both methods correctly identified successful ETT placement and in 3 (9%) both indicated the ETT was not in the trachea. In the remaining 11 (31%) intubations the PediCap® failed to change colour despite the flow wave indicating correct ETT placement.
CONCLUSION: Colorimetric CO(2) detectors may mislead clinicians intubating very preterm infants in the delivery room. They may fail to change colour in spite of correct tube placement in up to one third of the cases.

Assessment of flow waves and colorimetric CO2 detector for endotracheal tube placement during neonatal resuscitation
Resuscitation. 2011 Mar;82(3):307-12

Pre-hospital transcranial Doppler

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

Pre-hospital Echo

Pre-hospital physicians in Germany performed basic echo on patients with symptoms either of profound hypotension and/or severe dyspnoea/tachypnoea where judged by the physician to be in a ‘peri-resuscitation’ state, and on patients undergoing CPR. Features noted were; cardiac motion (present or absent), ventricular function (normal, moderately impaired, severely impaired, absent), right ventricular dilatation or pericardial collection.
A few interesting findings to note:

  • In almost all patients an interpretable view was achieved; in the CPR patients, the subcostal view was best
  • In PEA patients, there was a difference in survival to admission (to discharge isn’t documented) between those with and without sonographically evident cardiac wall motion (21/38 = 55% vs 1/13 = 8%)
  • In ‘suspected asystole’, some patients had sonographically evident cardiac wall motion, and 9/37 (24%) of these survived to hospital admission vs 4/37 (11%) with no wall motion. On this point, the authors note: ‘The ECG performance and interpretation were by experienced practitioners, and this therefore raises questions regarding the accuracy of an ECG diagnosis of asystole in the pre-hospital setting‘.

Purpose of the study: Focused ultrasound is increasingly used in the emergency setting, with an ALS- compliant focused echocardiography algorithm proposed as an adjunct in peri-resuscitation care (FEEL). The purpose of this study was to evaluate the feasibility of FEEL in pre-hospital resuscitation, the incidence of potentially treatable conditions detected, and the influence on patient management.
Patients, materials and methods: A prospective observational study in a pre-hospital emergency setting in patients actively undergoing cardio-pulmonary resuscitation or in a shock state. The FEEL protocol was applied by trained emergency doctors, following which a standardised report sheet was completed, including echo findings and any echo-directed change in management. These reports were then analysed independently.
Results: A total of 230 patients were included, with 204 undergoing a FEEL examination during ongoing cardiac arrest (100) and in a shock state (104). Images of diagnostic quality were obtained in 96%. In 35% of those with an ECG diagnosis of asystole, and 58% of those with PEA, coordinated cardiac motion was detected, and associated with increased survival. Echocardiographic findings altered management in 78% of cases.
Conclusions: Application of ALS-compliant echocardiography in pre-hospital care is feasible, and alters diagnosis and management in a significant number of patients. Further research into its effect on patient outcomes is warranted.
Focused echocardiographic evaluation in life support and peri-resuscitation of
emergency patients: A prospective trial

Resuscitation. 2010 Nov;81(11):1527-33

What's a normal newborn O2 sat?

Maybe they’re not just little adults after all: the normal reference ranges for oxygen saturation in the first few minutes of life have been defined for healthy newborns:
OBJECTIVE The goal was to define reference ranges for pulse oxygen saturation (SpO2) values in the first 10 minutes after birth for infants who received no medical intervention in the delivery room.
METHODS Infants were eligible if a member of the research team was available to record SpO2 immediately after birth. Infants were excluded if they received supplemental oxygen or any type of assisted ventilation. SpO2 was measured with a sensor applied to the right hand or wrist as soon as possible after birth; data were collected every 2 seconds.

RESULTS We studied 468 infants and recorded 61650 SpO2 data points. The infants had a mean ± SD gestational age of 38 ± 4 weeks and birth weight of 2970 ± 918 g. For all 468 infants, the 3rd, 10th, 50th, 90th, and 97th percentile values at 1 minute were 29%, 39%, 66%, 87%, and 92%, respectively, those at 2 minutes were 34%, 46%, 73%, 91%, and 95%, and those at 5 minutes were 59%, 73%, 89%, 97%, and 98%. It took a median of 7.9 minutes (interquartile range: 5.0–10 minutes) to reach a SpO2 value of >90%. SpO2 values for preterm infants increased more slowly than those for term infants. We present percentile charts for all infants, term infants of 37 weeks, preterm infants of 32 to 36 weeks, and extremely preterm infants of <32 weeks.
CONCLUSION These data represent reference ranges for SpO2 in the first 10 minutes after birth for preterm and term infants.
Defining the Reference Range for Oxygen Saturation for Infants After Birth
Pediatrics. 2010 Jun;125(6):e1340-7

Out of hospital monitoring in kids

I don’t have full text access to the Journal Pediatrics, so I’m not sure what I make of this small randomised trial comparing two types of blood pressure monitoring during paediatric transport:
BACKGROUND The “golden-hour” concept has led to emphasis on speed of patient delivery during pediatric interfacility transport. Timely intervention, in addition to enhanced monitoring during transport, is the key to improved outcomes in critically ill patients. Taking the ICU to the patient may be more beneficial than rapid delivery to a tertiary care center.

METHODS The Improved Monitoring During Pediatric Interfacility Transport trial was the first randomized controlled trial in the out-of-hospital pediatric transport environment. It was designed to determine the impact of improved blood pressure monitoring during pediatric interfacility transport and the effect on clinical outcomes in patients with systemic inflammatory response syndrome and moderate-to-severe head trauma. Patients in the control group had their blood pressure monitored intermittently with an oscillometric device; those in the intervention group had their blood pressure monitored every 12 to 15 cardiac contractions with a near-continuous, noninvasive device.
RESULTS Between May 2006 and June 2007, 1995, consecutive transport patients were screened, and 94 were enrolled (48 control, 46 intervention). Patients in the intervention group received more intravenous fluid (19.8 ± 22.2 vs 9.9 ± 9.9 mL/kg; P = .01), had a shorter hospital stay (6.8 ± 7.8 vs 10.9 ± 13.4 days; P = .04), and had less organ dysfunction (18 of 206 vs 32 of 202 PICU days; P = .03).
CONCLUSIONS Improved monitoring during pediatric transport has the potential to improve outcomes of critically ill children. Clinical trials, including randomized controlled trials, can be accomplished during pediatric transport. Future studies should evaluate optimal equipment, protocols, procedures, and interventions during pediatric transport, aimed at improving the clinical and functional outcomes of critically ill patients.
Enhanced Monitoring Improves Pediatric Transport Outcomes: A Randomized Controlled Trial
Pediatrics. 2011 Jan;127(1):42-8

GCS in intubated patients

We use the Glasgow Coma Score to describe conscious level, derived from eye opening, verbal response, and motor response.
One problem is that if your patient is intubated, there can’t be a verbal response. There are some ways round this. Imagine your intubated patient opens eys to a painful stimulus and withdraws his limb from one:

  • Just give him the lowest score (1) for the verbal component – E2M4V1
  • Write ‘V’ (ventilated) or ‘T’ (tube), eg. E2M4VT
  • Make it up, based on what you would expect the V score to be based on the E and M scores.

Weird as it sounds, there is a model for this, demonstrated in the paper abstracted below. The Derived Verbal Score = -0.3756 + Motor Score * (0.5713) + Eye Score * (0.4233).

Don’t worry…if you really want to use this, you don’t have to memorise that equation; there is an online calculator for it here and if you try it you’ll see this patient gets a derived verbal score of 2.3, and therefore a GCS of 7.3! Your decision now whether to round up or down. (In the meantime, I’ve given the patient a V of 1 and called it GCS E2M4VT=7.)
Alternatively, of course, you could try a better validated score that gives more information, the FOUR score, as validated here. The problem is, most people won’t know what you’re talking about.
The conundrum of the Glasgow Coma Scale in intubated patients: a linear regression prediction of the Glasgow verbal score from the Glasgow eye and motor scores.
Meredith W, Rutledge R, Fakhry SM, Emery S, Kromhout-Schiro S.
BACKGROUND: The Glasgow Coma Scale (GCS), which is the foundation of the Trauma Score, Trauma and Injury Severity Score, and the Acute Physiology and Chronic Health Evaluation scoring systems, requires a verbal response. In some series, up to 50% of injured patients must be excluded from analysis because of lack of a verbal component for the GCS. The present study extends previous work evaluating derivation of the verbal score from the eye and motor components of the GCS.
METHODS: Data were obtained from a state trauma registry for 24,565 unintubated patients. The eye and motor scores were used in a previously published regression model to predict the verbal score: Derived Verbal Score = -0.3756 + Motor Score * (0.5713) + Eye Score * (0.4233). The correlation of the actual and derived verbal and GCS scales were assessed. In addition the ability of the actual and derived GCS to predict patient survival in a logistic regression model were analyzed using the PC SAS system for statistical analysis. The predictive power of the actual and the predicted GCS were compared using the area under the receiver operator characteristic curve and Hosmer-Lemeshow goodness-of-fit testing.
RESULTS: A total of 24,085 patients were available for analysis. The mean actual verbal score was 4.4 +/- 1.3 versus a predicted verbal score of 4.3 +/- 1.2 (r = 0.90, p = 0.0001). The actual GCS was 13.6 + 3.5 versus a predicted GCS of 13.7 +/- 3.4 (r = 0.97, p = 0.0001). The results of the comparison of the prediction of survival in patients based on the actual GCS and the derived GCS show that the mean actual GCS was 13.5 + 3.5 versus 13.7 + 3.4 in the regression predicted model. The area under the receiver operator characteristic curve for predicting survival of the two values was similar at 0.868 for the actual GCS compared with 0.850 for the predicted GCS.
CONCLUSIONS: The previously derived method of calculating the verbal score from the eye and motor scores is an excellent predictor of the actual verbal score. Furthermore, the derived GCS performed better than the actual GCS by several measures. The present study confirms previous work that a very accurate GCS can be derived in the absence of the verbal component.
The conundrum of the Glasgow Coma Scale in intubated patients: a linear regression prediction of the Glasgow verbal score from the Glasgow eye and motor scores.
J Trauma. 1998 May;44(5):839-44 (if you have full text access to Journal of Trauma the best bit about this article is the discussion on pages 844-5 in which surgeons wrestle with the meaning of the word ‘conundrum’ and the spelling of ‘Glasgow’).

End tidal CO2 in cardiac arrest

Measuring end-tidal CO2 in cardiac arrest patients is helpful for

  1. confirming tracheal tube placement
  2. assessing the effectiveness of chest compressions
  3. predicting likelihood of return of spontaneous circulation (ROSC), in that a persistently low ETCO2 tends to predict death, whereas a high or rising ETCO2 is associated with a higher chance of ROSC.

It may be however that its predictive ability depends on the type of cardiac arrest, and how far into the resuscitation you’ve got when you measure the ETCO2. Consider this new study from Slovenian pre-hospital emergency physicians:
Methods: The study included two cohorts of patients: cardiac arrest due to asphyxia with initial rhythm asystole or pulseless electrical activity (PEA), and cardiac arrest due to arrhythmia with initial rhythm VF or pulseless VT. The causes of asphyxia were: asthma, severe acute respiratory failure, tumor of the airway, suicide by hanging, acute intoxication, pneumonia and a foreign body in the airway.PetCO2 was measured for both groups immediately after intubation and repeatedly every minute, both for patients with or without return of spontaneous circulation (ROSC). We compared the dynamic pattern of PetCO2 between groups. Resuscitation procedures were performed by an emergency medical team (emergency medical physician and two emergency medical technicians or registered nurses) in accordance with 2005 ERC Guideline
Results: Between June 2006 and June 2009 resuscitation was attempted in 325 patients and in this study we included 51 patients with asphyxial cardiac arrest and 63 patients with VF/VT cardiac arrest. The initial values of PetCO2 were significantly higher in the group with asphyxial cardiac arrest (6.74 ± 4.22 kilopascals (kPa) versus 4.51 ± 2.47 kPa; P = 0.004). In the group with asphyxial cardiac arrest, the initial values of PetCO2 did not show a significant difference when we compared patients with and without ROSC (6.96 ± 3.63 kPa versus 5.77 ± 4.64 kPa; P = 0.313). We confirmed significantly higher initial PetCO2 values for those with ROSC in the group with primary cardiac arrest (4.62 ± 2.46 kPa versus 3.29 ± 1.76 kPa; P = 0.041).

A significant difference in PetCO2 values for those with and without ROSC was achieved after five minutes of CPR in both groups (asphyxial arrest: 6.09 ± 2.63 kPa versus 4.47 ± 3.35 kPa; P = 0.006; primary arrest: 5.63 ± 2.01 kPa versus 4.26 ± 1.86; P = 0.015)
In mmHg, the PetCO2 values for those with and without ROSC after five minutes of CPR was: asphyxial arrest: 42.3 ± 20 mmHg versus 34 ± 25.5 mmHg; P = 0.006; primary arrest: 42.8 ± 15.3 mmHg versus 32.3 ± 14.1 mmHg; P = 0.015
Graphically, this difference in ROSC vs non-ROSC PetCO2 for both groups appeared to be even greater at ten minutes, with higher statistically significance (p<0.001), although the values of PetCO2 are not given in the paper.
In all patients with ROSC the initial PetCO2 was again higher than 1.33 kPa (10.1 mmHg).
Conclusions: The dynamic pattern of PetCO2 values during out-of-hospital CPR showed higher values of PetCO2 in the first two minutes of CPR in asphyxia, and a prognostic value of initial PetCO2 only in primary VF/VT cardiac arrest. A prognostic value of PetCO2 for ROSC was achieved after the fifth minute of CPR in both groups and remained present until final values. This difference seems to be a useful criterion in pre-hospital diagnostic procedures and attendance of cardiac arrest.
The authors summarise with the following key messages:

  • Initial values of PetCO2 are higher in asphyxial cardiac arrest than in primary cardiac arrest.
  • Initial values of PetCO2 in asphyxial cardiac arrest do not have a prognostic value for resuscitation outcome.
  • The prognostic value of PetCO2 for ROSC was achieved after the fifth minute of CPR in both groups and remained present until the final values.
  • The values of PetCO2 seem to be useful in differentiating the causes of cardiac arrest in a pre-hospital setting.

I think that last one’s a bit of a stretch. For me, this paper confirms that the longer you are into a cardiac arrest resuscitation, the worse news a low PetCO2 is. The lack of predictive value of initial PetCO2, particularly in the asphyxia group, is interesting but not surprising.
The dynamic pattern of end-tidal carbon dioxide during cardiopulmonary resuscitation: difference between asphyxial cardiac arrest and ventricular fibrillation/pulseless ventricular tachycardia cardiac arrest
Critical Care 2011, 15:R13

Passive leg raising during CPR

Measuring end-tidal carbon dioxide (ET CO2 ) is a practical non-invasive method for detecting pulmonary blood flow, reflecting cardiac output and thereby the quality of CPR. It has also been shown to rise before clinically detectable return of spontaneous circulation (ROSC).
Passive leg raising (PLR) increases venous return and may therefore augment cardiac output and in a cardiac arrest this may be reflected by an elevation in ETCO2.
A Swedish observational study of 126 patients with out of hospital cardiac arrest due to a likely cardiac aetiology underwent tracheal intubation with standardised ventilation and chest compressions (either manually or using the LUCAS device, as part of larger study of mechanical chest compressions according to a cluster design). Patients were stratified to receive either PLR to 20 degrees or no PLR. ETCO2 was measured during CPR, either for 15min, or until the detection of ROSC.

Hang on I think that's overdoing it a bit

During PLR, an increase in ETCO2 was found in all 44 patients who received PLR within 15s (p=0.003), 45s (p = 0.002) and 75 s (p = 0.0001). Survival to hospital discharge was 7% among patients with PLR and 1% among those without PLR (p = 0.12). Among patients experiencing ROSC (60 of 126), there was a marked increase in ETCO2 1 min before the detection of a palpable pulse.
Passive leg raising during cardiopulmonary resuscitation in out-of-hospital cardiac arrest—Does it improve circulation and outcome?
Resuscitation. 2010 Dec;81(12):1615-20