Category: Commentaries

Capnography for emergency department procedural sedation and analgesia

What we already know about this topic

 
In medicine, capnography consists in the continuous measurement of partial pressure of carbon dioxide (PCO2) in the exhaled gases, operated by an infrared sensor positioned at the facemask or nasal cannula. Data are presented as a graph of PCO2 in function of time (or less frequently of expired volume), the so-called capnogram, and as a numerical value corresponding to the PCO2 at the end of expiration (end tidal CO2, ETCO2) (1,2).
Assuming steady cellular metabolism and normal tissue perfusion, ETCO2 can help detecting ventilation abnormalities, which can occur after administration of sedative agents. There is some evidence that capnography allows clinicians in the Emergency Department to detect hypoventilation early than usual monitoring (pulse oximetry, hemodynamic parameters, and clinical evaluation) and more efficiently (3), helping preventing onset of more severe adverse events such aspiration or unplanned intubation. Bellolio and colleagues provided an estimation of such complications collecting data from 5 studies including 9652 procedural sedations: estimated risk for hypoxia resulted in 23 cases per 1000 patients (defined as SatO2 < 90%), for apnea in 12,4 cases per 1000 patients, for aspiration in 1,2 cases per 1000 patients and for intubation in 1,6 cases per 1000 patients (4).
In 2014, ACEP released its Clinical Policy regarding procedural sedation in the Emergency Department in which stated that “capnography may be used as an adjunct to pulse oximetry and clinical assessment to detect hypoventilation and apnea earlier then pulse oximetry and/or clinical assessment alone in patients undergoing procedural sedation and analgesia in the ED” with a level of recommendation B (moderate clinical certainty) (2).
Since then, new evidence appeared in the medical literature, which has been reviewed and synthetized in a recently published systematic review from Cochrane Collaboration.
 

The Cochrane review (5)

Title: Capnography versus standard monitoring for emergency department procedural sedation and analgesia.
Authors: Wall BF, Magee K, Campbell SG, Zed PJ.
Bibliographic citation: Cochrane Database Syst Rev 2017; 3: CD010698.
Objective: to assess whether capnography in addition to standard monitoring (pulse oximetry, blood pressure and cardiac monitoring) is more effective than standard monitoring alone to prevent cardiorespiratory (oxygen desaturation, hypotension, emesis and pulmonary aspiration) in ED patients undergoing procedural sedation and analgesia.
Included studies: randomized controlled trials or quasi-randomized controlled trials.
Primary outcome: oxygen desaturation (percentage of oxygen saturation in arterial blood less than 90% for 30 seconds), hypotension (systolic blood pressure less than 90 mmHg), emesis and pulmonary aspiration.
Secondary outcomes: Airway intervention performed (airway repositioning manoeuvres, positive pressure ventilation, oral pharyngeal or nasal pharyngeal airway placement, endotracheal intubation), recovery time.
Number of included studies: 3.
Quality of included studies: major concerns about blinding of partecipants and personnel and blinding of utcome assessment.
Number of patients: 1272
 

Results

 

Outcome

No. of studies / No. of patients

Risk Ratio (95% C.I.)

Quality of evidence

Oxygen desaturation

3 / 1272

0,89 (0,48 – 1,63)

Moderate

Hypotension

1 / 986

2,36 (0,98 – 5,69)

Moderate

Emesis

1 / 986

3,10 (0,13 – 75,88)

Moderate

Airway interventions

3 / 1272

1,26 (0,94 – 1,69)

Moderate

 
Table 1. Results of the systematic reviews. Pulmonary aspiration was not recorded in any study. Risk ratios below 1 favors capnography use.
 
 

Outcome

No. of studies / No. of patients

Risk Ratio (95% C.I.)

Oxygen desaturation

2 / 1118

0,79 (0,37 – 1,71)

Airway interventions

2 / 1118

1,44 (1,16 – 1,79)

 
Table 2. Results of the systematic reviews. Results of sensitivity analyses with adult subjects. Risk ratios below 1 favors capnography use.
 

Comment and conclusions

Use of capnography resulted in an increased utilization of airway interventions with a non-significant reduction in detected hypoxia. Airways interventions in included studies were as follows: verbal or physical stimulation, airway realignment, use of oxygen supplementation, airway repositioning maneuver, positive pressure ventilation, oral/nasal airway placement, endotracheal intubation. Among them, endotracheal intubation was never performed and there were just two patients necessitating positive pressure ventilation.
Patients included in the trials considered for this meta-analysis are young: in Campbell study (Campbell 2016), median age is 45 in control group and 47 years in intervention group while in Deitch one, median age is 37 in control arm and 31 years in intervention arm (Langhan study recruited pediatric subjects). This constitutes a limitation to the applicability of results, considering that, for example, patients undergoing procedural sedation because of cardiologic interventions (e.g., cardioversion) are seldom older.   
In Campbell and Deitch studies, propofol was used in the vast majority of cases while in Langhan one ketamine was chosen in 97% of procedures; for this reason, results of this meta-analysis must be applied with caution if other sedative agents are used.
In this systematic review, about 77% of the patients were enrolled in just one Emergency Department in Canada; taking into account the wide variability of clinical practice, operational settings and spectrum of patients which ca be observed in Emergency Medicine, the perspective offered by the present work is probably too much restricted for drawing firm conclusions.
Absence of blinding both for clinicians involved in delivering the interventions and detecting the outcome may introduce bias: the awareness of monitoring technology employed may influence, even unconsciously, the operator behavior and ultimately, the outcome occurrence and detection. This could be even more relevant because physicians in the three studies were free to use their own judgment to intervene in the case of ETCO2 increases.
Heterogeneity is relevant for every outcome evaluated and is mainly explained by the differences in age of the patients and in the definition of hypoxia.
Use of capnography resulted in an increased utilization of low impact airway interventions with a non-significant reduction in hypoxia incidence in high a restricted population of young patients managed by highly skilled emergency physicians. More evidence is needed to clarify the impact of this diagnostic technology in a broader population of patients, including older subjects in the first place. Indeed, with present data we cannot exclude that in real life situations, where procedural sedation is delivered by emergency physicians with varying degrees of expertise in more aged and less healthy patients, capnography may offer a significant benefit in the prevention of severe adverse events.
 
Bibliography
 
  1. Nagler J, Krauss B. Capnography: a valuable tool for airway management. Emerg Med Clin N Am 2008; 26: 881–897.
  2. Godwin, Burton JH, Gerardo CJ, Hatten BW, Mace SE, Silvers SM, Fesmire FM. Clinical Policy: Procedural Sedation and Analgesia in the Emergency Department. Ann Emerg Med 2014; 63: 247-258.
  3. Miner JR, Heegaard W, Plummer D. End-tidal Carbon Dioxide Monitoring during Procedural Sedation. Acad Emerg Med 2002; 9:275–280
  4. Bellolio MF, Gilani WI, Barrionuevo P, Murad MH, Erwin PJ, Anderson JR, Miner JR, Hess EP. Incidence of Adverse Events in Adults Undergoing Procedural Sedation in the Emergency Department: A Systematic Review and Meta-analysis. Acad Emerg Med 2016; 23(2):119-34.
  5. Wall BF, Magee K, Campbell SG, Zed PJ. Capnography versus standard monitoring for emergency department procedural sedation and analgesia. Cochrane Database Syst Rev 2017; 3: CD010698.
  6. Campbell SG, Magee KD, Zed PJ, Froese P, Etsell G, LaPierre A, Warren D, MacKinley RR, Butler MB, Kovacs G, Petrie DA. End-tidal capnometry during emergency department procedural sedation and analgesia: a randomized, controlled study. World J Emerg Medn 2016; 7 (1): 13-18.
  7. Deitch K, Miner J, Chudnofsky CR, Dominici P, Latta D. Does End Tidal CO2 Monitoring During Emergency Department Procedural Sedation and Analgesia with Propofol Decrease the Incidence of Hypoxic Events? A Randomized, Controlled Trial. Ann Emerg Med 2010; 55(3): 258-264.
  8. Langhan ML, Shabanova V, Li F-Y, Bernstein SL, Shapiro ED. A Randomized Controlled Trial of Capnography During Sedation in a Pediatric Emergency Setting. Am J Emerg Med 2015; 33(1): 25–30.

 

 

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