Squadrone, 2005

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Continuous Positive Airway Pressure for Treatment of Postoperative Hypoxaemia

Early treatment with CPAP reduces the need for intubation, ICU stay, the incidence of pneumonia, infection and sepsis in patients who develop hypoxaemia after major abdominal surgery.

Level of Evidence: 1⁺ (RCT with a low risk of bias)

Citation/s: Squadrone V, et al. Continuous Positive Airway Pressure for treatment of Postoperative Hypoxaemia: A Randomized Controlled Trial. JAMA Volume 293; Feb 2005 Page 589-595

Lead author's name and email: V. Marco Ranieri, (marco.ranieri@unito.it).

Three-part Clinical Question: Does the use of CPAP lead to a decreased need for endotracheal intubation compared to standard therapy alone in patients with postoperative hypoxaemia?

Search Terms: 1) Postoperative hypoxemia (90); 2) Continuous positive airways pressure (395) 1) + 2) = 1

The Study: Single-blinded randomized controlled trial with intention-to-treat.

The Study Patients: Consecutive patients who developed severe hypoxaemia after major elective abdominal surgery.

Inclusion Criteria: a) Laparotomy (elective) with viscera exposure>90 mins b) Extubation post op and breathing O2 (FiO2 = 0.3) and thereafter developed PaO2/FiO2 < 300.

Exclusion Criteria: Patient Characteristics: a) >80 years or < 18 years old b) NYHA II, III or IV c) Valvular heart disease or pacemaker d) Dilated cardiomyopathy e) Unstable angina, recent MI or cardiac surgery within previous 3 months f) COPD g) Tracheostomy h) BMI > 40 or chest wall abnormalities i) Sepsis or infection j) Preop pH < 7.3 with PaCO2 > 50 mmHg; Hb< 7 or Cr > 3.5mg/dl

Control group: (N = 104; 104 analyzed): Oxygen given through a Venturi mask with an FiO2 of 0.5 for 6 hours after which they received a trial of FIO2 of 0.3 for 1 hour, and the PaO2/FiO2 measured

Experimental group: (N = 105; 105 analyzed): Oxygen given at an FiO2 of 0.5 with a CPAP of 7.5cmH2O via a CPAP helmet (lead to a very low intolerance rate of 4%). Given for 6 hours and received a similar trial to control group of FiO2 of 0.3 for 1 hour via a venturi mask, and the PaO2/FiO2 ratio measured

The Evidence:

Outcome	Time to Outcome	CER	EER	RRR	ARR	NNT
Endotracheal Intubation	7 days post surgery	0.1	0.01	90%	0.090	11
Endotracheal Intubation	95% Confidence Intervals:			29% to 100%	0.029 to 0.151	7 to 34
Pneumonia	1 week postoperatively	0.1	0.02	80%	0.080	13
Pneumonia	95% Confidence Intervals:			16% to 100%	0.016 to 0.144	7 to 61
ICU Stay > 4 days	4 days	0.13	0.04	69%	0.090	11
ICU Stay > 4 days	95% Confidence Intervals:			12% to 100%	0.015 to 0.165	6 to 65

Measure	Control Group		Experimental Group		Difference	95% CI
Measure	Mean	SD	Mean	SD	Difference	95% CI
PaO2/FiO2 Ratio	341	32	432	45	-91	NS
Time to achieve oxygenation goal	28	27	19	22	9	NS

Non-Event Outcomes	Time to outcome/s	Control group	Experimental group	P-value
Postoperative Infection	1 week postoperatively	10%	3%	0.03
Sepsis Postoperatively	1 week postoperatively	9%	2%	0.03

EBM questions:

1. Do the methods allow accurate testing of the hypothesis: Yes. . Blinding impossible, however to minimize bias a standard criteria for intubation was practiced.

2. Do the statistical tests correctly test the results to allow differentiation of statistically significant results? Yes. Initial powering took into consideration previous studies, which predicted a 10% intubation rate in the patients included (would need 600 patients). Stopped early due to effectiveness of CPAP (p<0.016).

3. Are conclusions valid in light of the results? Yes. However this was a fairly specific patient group, which may not reflect all postop laparotomy patients. It is not clear why specifically surgery lasting more than 90 mins was chosen.

4. Did results get omitted and why? No

5. Did they suggest further areas of research? No

6. Did they suggest ant recommendations based on the results, and were they appropriate? Yes. They suggested the use of CPAP in post op hypoxaemia after bowel surgery is advantageous and relatively cheap.

7. Is this study relevant to my clinical practice? Yes. However the practicalities of the use of CPAP in the recovery room and HDU are not as straight forward as in the centre where the trial was carried out.

8. What level of evidence does this represent? 1+

9. What grade of recommendation can I make form this study? B

10. What grade of recommendation can I make when this study is considered along with other available evidence? N/A

11. Should I change my practice in light of these results? Yes

12. I may be inclined to perform a trial of CPAP in postop laparotomy patients as opposed to oxygen alone, but nursing time and equipment availability may prove problematic. Undoubtedly though the results of this well designed trial are promising in reducing intubation rates of patients requiring oxygen postop laparotomy, which may be as high as 30-50% as stated in this paper.

Appraised by: Pam Doherty SpR Department Anaesthesia and Intensive Care, Western Infirmary, Glasgow; 07 June 2005

Email: pamdoherty@doctors.org.uk

Citation: EBM Critical Appraisals. Scottish Intensive Care Society EBM Group. Doherty P. 2005. Squadrone V, et al. Continuous Positive Airway Pressure for treatment of Postoperative Hypoxaemia: A Randomized Controlled Trial. JAMA Volume 293; Feb 2005 Page 589-595.

Reviewed & Edited by CC & KR

Kill or Update By: June 2007

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