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CLINICAL INVESTIGATION
Year : 2008  |  Volume : 52  |  Issue : 2  |  Page : 185-190 Table of Contents     

Management of Postoperative Hypoxaemia in Patients Following Upper Abdominal Laparoscopic Surgery. - A Comparative Study


1 Assistant Professor, Department Of Anaesthesiology, I.P.G.M.E. & R., Kolkata, 244, Acharyya Jagadish Chandra Bose Road, Kolkata 700020, India
2 P.G.Student, Department Of Anaesthesiology, I.P.G.M.E. & R., Kolkata, 244, Acharyya Jagadish Chandra Bose Road, Kolkata 700020, India
3 Clinical Tutor, Department Of Anaesthesiology, I.P.G.M.E. & R., Kolkata, 244, Acharyya Jagadish Chandra Bose Road, Kolkata 700020, India
4 Associate Professor, Department Of Anaesthesiology, I.P.G.M.E. & R., Kolkata, 244, Acharyya Jagadish Chandra Bose Road, Kolkata 700020, India
5 Professor, Department Of Anaesthesiology, I.P.G.M.E. & R., Kolkata, 244, Acharyya Jagadish Chandra Bose Road, Kolkata 700020, India

Date of Acceptance22-Feb-2008
Date of Web Publication19-Mar-2010

Correspondence Address:
Sampa Datta Gupta
42 Lake Place. 1st floor. Kolkata 700029
India
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Source of Support: None, Conflict of Interest: None


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Noninvasive ventilation has been shown to reduce acute postoperative hypoxaemia, with significant reduction in the incidence of re-intubation, complications and a trend towards lower mortality. The aim of the study was to determine the effectiveness of CPAP vs venturi therapy in early achievement of oxygenation goals and in prevention of re-intubation for management of postoperative hypoxaemia following laparoscopic cholecystectomy. Forty adult patients of ASA physical status I& II, scheduled for elective laparoscopic cholecystectomy, those were unable to maintain SpO2 > 95% breathing room air after extubation, were recruited for a prospective, randomized comparative study. Patients with PaO2 / FiO2 between 250 and 300 were included in the study and were randomly allocated to one of the two groups to receive oxygen therapy either using a CPAP of 10 cm of water and a FiO2 of 0.5 (Group A) or using a venturi mask of FiO2 of 0.5 (Group B) . All patients were observed postoperatively upto 18 h and were screened by ABG analyses at 6, 12 and 18 h of treatment. SpO2, ECG, heart rate, respiratory rate, temperature and NIBP were monitored throughout the study period. Patients in Group A showed significant improvement in early achievement of adequate oxygenation than those in Group B, although, due to intolerance to CPAP therapy two patients in Group A needed reintubation to maintain adequate oxygenation. To conclude, oxygenation using continuous positive airway pressure is a safe and effective means in improving gas exchange to treat acute postoperative hypoxaemia in conscious and cooperative patients.

Keywords: Laparoscopic cholecystectomy; Postoperative hypoxaemia; Management; CPAP, Venturi mask


How to cite this article:
Gupta SD, Pareek A, Ghose T, Sarkar UK, Mukherjee S, Goswami A, Sarbapalli D, Pal S. Management of Postoperative Hypoxaemia in Patients Following Upper Abdominal Laparoscopic Surgery. - A Comparative Study. Indian J Anaesth 2008;52:185-90

How to cite this URL:
Gupta SD, Pareek A, Ghose T, Sarkar UK, Mukherjee S, Goswami A, Sarbapalli D, Pal S. Management of Postoperative Hypoxaemia in Patients Following Upper Abdominal Laparoscopic Surgery. - A Comparative Study. Indian J Anaesth [serial online] 2008 [cited 2020 Dec 4];52:185-90. Available from: https://www.ijaweb.org/text.asp?2008/52/2/185/60619


   Introduction Top


Incidence of postoperative hypoxaemia in major elective upper abdominal surgeries is between 6 and 60%. Despite reduced incidences in postoperative pul­monary dysfunction following laparoscopic cholecystec­tomy in comparison to open cholecystectomy procedures, PaO2 still decreases and can persist for at least 24 hours postoperatively. Diaphragmatic function remains signifi­cantly impaired. Forced expiratory volume, forced vital capacity and forced expiratory flow are reduced by ap­proximately 25 %. [1]

The most common cause of postoperative hypoxaemia is an increase in right to left intrapulmonary shunting. Atelectasis is the most common cause of an increased right to left shunt. Reverse Trendelenburg position for laparoscopic cholecystectomy causes re­duction in cardiac output which causes further decrease in PaO 2 in patients with existing increased intrapulmonary shunts, which develop due to general anaesthe­sia, although, laparoscopy is often to be considered a minor surgical procedure, oxygen should be administered postoperatively, even to healthy patients . Greater re­ductions in expiratory values and slower recovery of pulmonary function after laparoscopy are reported in older patients. Moreover the combined effect of pneumoperitonium and sedation can lead to hypoventilation and arterial oxygen desaturation. Al­though no anaesthetic technique has proved to be clini­cally superior to another, general anaesthesia with con­trolled ventilation seems to be a safe technique for op­erative laparoscopy. Thoracic epidural anaesthesia does not improve lung function after laparoscopic cholecystectomy. [2]

The PaO 2 response to oxygen therapy depends on the degree of intrapulmonary shunting. Increasing the FiO 2 from 0.21 breathing room air to 1 results in a large increase in PaO 2 when shunt fraction is small. However, this will have little effect on PaO 2 in patients with large shunt fraction.

Controlled trials of noninvasive ventilation to treat patients with acute hypoxaemic respiratory failure have shown statistically significant reduction in the ratio of reintubation, length of hospital stay, incidence of infec­tions, complications and a trend towards lower mortal­ity. [3] CPAP by an external mask (mask or nasal CPAP) may be used for treatment of patients with severe hypoxaemia who have adequate carbon dioxide elimi­nation. [4] Though positive - pressure ventilation is useful in patients with severe hypoxaemia or respiratory aci­dosis. Ventilation with end-expiratory pressure improves oxygenation by increasing lung volume and not by de­creasing lung water. [5] A recent study has shown that for patients with severe hypoxaemia, NPPV is superior to conventional oxygen supplementation in preventing gas-exchange deterioration during fibreoptic bronchos­copy with better haemodynamic tolerance. [6]

Considering the results of previous studies, the aims of this study were to determine the effectiveness of continuous positive airway pressure (CPAP) therapy vs oxygen therapy using venturi mask in patients who developed acute postoperative hypoxaemia after elec­tive laparoscopic cholecystectomy in early achievement of oxygenation and prevention of intubation.


   Methods Top


After obtaining approval from Institutional Ethics Committee and written informed consent from all pa­tients, this prospective randomized study was carried out in the Department of Anaesthesiology, IPGME&R, Kolkata.

Inclusion criteria

Patients between the age group of 40 and 60 years, of both sexes, belonging to ASA class I& II., who had laparoscopic cholecystectomy with a duration of gen­eral anaesthesia ranging from 60 minutes to 180 min­utes and those developed acute postoperative hypoxaemia with a PaO 2 / FiO 2 ratio between 250 and 300 were included in study. Patients with PaCO 2 greater than 50 mm Hg were also included in the study.

Patients who were unable to maintain SpO 2 of more than 95% breathing room air after extubation 7 were divided into three categories depending on the re­port of arterial blood gas analyses­

  • When PaO 2 / FiO 2 < 250 -- they were intubated for oxygenation.
  • When PaO 2 / FiO 2 between 250 and 300 -- se­lected for study.
  • When PaO 2 / FiO 2 > 300 -- kept for observation.
Exclusion criteria : Patients with coexisting pulmo­nary diseases, cardiac diseases, postoperative PaO 2 / FiO 2 ratio <250 and >300, severe hypotension, impaired consciousness were excluded from this study.

Forty patients with PaO 2 / FiO 2 ratio between 250 and 300 were randomly allocated into two groups through computer-generated random number concealed in sealed envelopes to receive oxygen supplementation delivered either by a venturi mask or a CPAP system,

  • Group A (n=20) CPAP Group, where patients were oxygenated using continuous positive airway pres­sure of 10 cm of water with FiO 2 of 0.5.
  • Group B(n=20) Venturi Group, where patients were oxygenated using venturi mask with FiO 2 of 0.5.
Total sample size (n = 40) was determined by power analysis from the means and standard deviation obtained from a previously done pilot study.

All patients were observed postoperatively upto 18 h and they were screened by ABG analyses at 6, 12 and 18 h of treatment and whenever there was a doubt of hypoxaemia.

Anaesthesia was induced with fentanyl-propofol­atracurium and maintained with O 2 -N 2 O-isoflurane-fen­tanyl-atracurium. Total dose of fentanyl not exceeded 2mcg.kg -1 and end tidal carbon dioxide were maintained between 35 - 45 mm Hg. At the end of surgery 30 min prior to skin closure wounds were infiltrated with bupivacaine (0.25 %) 3 mg.kg -1 and diclofenac supposi­tories were administered per rectally to alleviate post­operative pain. Postoperative pain assessment was done with the help of VAS score.

Tramadol bolus of 0.5mg.kg -1 was reserved as res­cue analgesic for pain response.

Monitoring throughout the study period included SpO 2 %, ECG, heart rate, respiratory rate, tempera­ture and NIBP.

Main outcome of the study was determined by -

  • The achievement of oxygenation goal of a PaO 2 / FiO 2 ratio > 300, which was the primary end point.
  • Incidence of endotracheal intubation, which was the secondary end point.
Criteria for endotracheal intubation -

Predetermined criteria for endotracheal intubation would be identical for all groups and would include one of the following:

  • Failure of adequate gas exchange during CPAP/ venturi mask therapy requiring mechanical ventila­tion.
  • Loss of alertness or agitation needing sedation
  • Signs of exhaustion
  • Absence of cough, inability to maintain airway with head in flexion
  • Respiratory arrest
  • Haemodynamic instability (MAP <65 mmHg), fre­quent recurrent dysrrhythmia
  • Cardiac arrest
  • Signs of patient distress with accessory muscle re­cruitment and paradoxical abdominal motion
  • RR > 35/min
  • Respiratory acidosis (pH < 7.3 and PaCO 2 > 50 mmHg)
Untoward effects like vomiting and intolerance to therapy were observed and noted during the study and managed accordingly.

Statistical analysis -- All raw data were entered into an Excel spreadsheet and analyzed. Parametric data were analyzed using students 't' -test and qualitative data analyzed using chi-square test and a P value of < 0.05 were considered statistically significant.


   Results Top


[Table 1] Contains the summary of statistical analy­ses for the demographic profiles of patients belonging to the two groups and the duration of anaesthesia. Apply­ing students't' test for numerical data and the chi-square test for categorical data (sex of patients) it is found that the two groups are comparable in terms of demographic profiles and duration of general anaesthesia.

Baseline monitoring parameters at the time of ini­tiation of therapy are shown in [Table 2]. Applying the unpaired student's 't' test for numerical data, it is found that there is no significant difference between the two groups of patients at the time of initiation of therapy.

The changes in the PaO 2 /FiO 2 ratio between the two groups at 0 hours, 6 hours, 12 hours and 18 hours were compared[Table 3]. Although there were no sig­nificant differences in oxygenation at the end of 12 hours but at the end of 18 hours, patients belonging to group A (CPAP) showed significant improvement in oxygenation in terms of improved PaO 2 /FiO 2 ratio. At the end of 12 hours of therapy all the patients achieved adequate oxy­genation whereas only 11 out of 20 patients of venturi therapy (GroupB) could achieve PaO 2 /FiO 2 > 300.

Bar diagram in [Figure 1] shows the number of patients in both groups A and B at different time intervals (0, 6, 12 and 18 hrs ) of therapy, who have a PaO 2 /FiO 2 < 300.

At 6 h of CPAP therapy patients in Group A showed significant improvement in achieving early oxy­genation than patients in Group B who were on ven­turi therapy[Table 4] .

Two patients of Group -A became intolerant, vom­ited and became hypoxic and to maintain arterial oxygen saturation they needed intubation, but these untoward ef­fects are not statistically significant( P< 0.15) [Table 5].


   Discussion Top


Laparoscopy results in multiple postoperative benefits including less trauma, less pain, less pulmonary dysfunction, quicker recovery and shorter hospital stay. These advantages are regularly emphasized and explain the increasing success of laparoscopy, which is proposed for many surgical procedures.

Though respiratory dysfunction is less severe and recovery is quicker after laparoscopy PaO2 still de­creases after laparoscopic cholecystectomy. During early postoperative period respiratory rates are higher after laparoscopy than in open surgery. The combined effect of pneumoperitonium and sedation can lead to hypoventilation and increased right to left intrapulmo­nary shunting as a result of diffuse airway collapse lead­ing to arterial oxygen desaturation. The relationship be­tween the functional residual capacity (FRC) of the lung and closing capacity is a prime determinant of this effect. The diaphragmatic function remains significantly impaired following laparoscopic cholecystectomy. The cause of this dysfunction may be related to diaphrag­matic tension during pneumoperitonium. Postoperative pulmonary complications contribute significantly to overall peri-operative morbidity and mortality rates. Post­operative intubation is associated with increased mor­bidity, mortality and prolonged stay in postoperative care unit. Reduction in cardiac output due to reversed Trendelenburg position can contribute to decreases in PaO 2 in patients with existing intrapulmonary shunts because of the effect of the lowered mixed venous PO 2 , which is added directly to the arterial circulation through the right - to - left shunt [8] . Arterial hypoxaemia may be present in postoperative patients who have no discern­ible change in their chest radiogram.

High flow system is one in which the gas flow of the apparatus is sufficient to meet all inspiratory require­ments. Most high flow oxygen delivery systems use the method of gas entrainment to provide a specific FiO 2 and adequate flow. Traditionally, these were referred to as "venturi devices ". The FiO 2 and total gas flow is determined by altering the size of the entrainment port, and the oxygen flow through the device. FiO 2 values from 0.24 to 0.60 are provided by air entrainment mask.

Actual documentation of hypoxaemia can often be made when the patient is breathing room air without any CPAP. Treatment of hypoxaemia by oxygen via facemask is effective in restoring PaO 2 in many cases. The PaO 2 response to breathing oxygen depends on the degree of intrapulmonary shunting. Increasing FiO 2 from 0.21 breathing room air to 1 results in large increase in PaO 2 when the shunt fraction is small but it may not improve in the presence of a large shunt frac­tion. Application of CPAP increases FRC and reduc­tion in shunt fraction resulting in improvement in arterial oxygenation even without increasing FiO 2 as in the post operative period when the FRC remains low.

Mechanical ventilation through an endotracheal tube is a lifesaving procedure for acute respiratory fail­ure. However endotracheal intubation increases patient discomfort and stress, and represents one of the most important predisposing factors for developing nosoco­mial bacterial pneumonia.

The use of CPAP by a face mask (mask or nasal CPAP ) is increasingly being used for the treatment of patients with severe hypoxaemia who have adequate carbon dioxide elimination. Good candidate for mask or nasal CPAP are patients with severe hypoxaemia re­quiring 80 % oxygen to achieve a PaO 2 above 60 mm Hg. They must have a normal or low PaCO 2 and not be in severe respiratory distress. They must be awake and alert. Mask or nasal CPAP is most useful when the cause of hypoxaemia can be quickly corrected.

This study included 40 patients who were enrolled in a randomized trial to compare the efficacy of CPAP with standard oxygen therapy using venturi mask. Pa­tients who had postoperative hypoxaemia ( those who were unable to maintain SpO2> 95 % at FiO 2 0.21 ) after laparoscopic cholecystectomy were randomly al­located to receive either CPAP ( Group-A ) with oxy­gen supplementation at an FiO 2 of 0.5 or oxygen therapy using venturi mask at an FiO 2 of 0.5 (Group-B). The effectiveness of therapy was assessed by intermittent measurements of arterial blood gases and determining the primary end point of the study i.e. time to achieve a PaO 2 /FiO 2 ratio > 300. The secondary end point of the study was to determine the incidence of reintubation in the two groups of patients. CPAP group (GroupA) re­vealed significant improvement in early achievement of adequate oxygenation than venturi therapy group (Group B), however two patients of the CPAP group needed postoperative reintubation due to signs of exhaustion, vomiting and intolerance to treatment with tight fitted mask. Smith RA et al in 1980 showed in their study that the use of CPAP by an external mask ( mask or nasal CPAP ) is increasingly being used for treatment of patients with severe hypoxaemia who have adequate carbon dioxide elimination. Good candidate for mask or nasal CPAP are patients with severe hypoxaemia requiring more than 80% oxygen to achieve PaO 2 above 60 mm Hg. They must have a normal PaCO 2 ,and not be in severe respiratory distress. They must be awake and alert [4] .

Saul GM, in 1982 showed in their study that posi­tive - pressure ventilation is useful in patients with se­vere hypoxaemia or respiratory acidosis. Ventilation with end-expiratory pressure improves oxygenation by in­creasing lung volume [5] .

Massimo Antonelli et al in 2002 showed in their study that in patients with severe hypoxaemia, NPPV is superior to conventional oxygen supplementation in pre­venting gas-exchange deterioration during FOB with better hemodynamic tolerance [6] .

Therefore, in conscious and cooperative patients noninvasive positive pressure ventilation is a safe and effective means for patients with acute respiratory fail­ure (ARF), improving gas exchanges and reducing the rate of complication related to mechanical ventila­tion. Continuous positive airway pressure ( CPAP ) delivers a constant pressure both in inspiration and expiration during spontaneous breathing which opens the collapsed and under ventilated alveoli, decreases intra­pulmonary shunt, improves lung compliance, improves oxygenation, decreases work of breathing, lowers left ventricular transmural pressure, decreases afterload and thereby improves cardiac output.

Though benefits of this therapy must be weighed against the cost, potential adverse effects and require­ment for close observation compared to other types of bronchial hygiene therapy.

To conclude that, to treat acute postoperative hypoxaemia in conscious and cooperative patients, oxy­genation using continuous positive airway pressure is a safe and effective means, improving gas exchange.

 
   References Top

1.Morgan GE, Mikhail MS, Michael J. Murray Anesthesia for Patients with Respiratory Disease. Clinical Anesthesiology 2006; 23: 571 - 584.  Back to cited text no. 1      
2.Miller RD. Anaesthesia for laparoscopic surgery. Miller's An­esthesia 2006, 57 : 2285 - 2299.  Back to cited text no. 2      
3.Miller RD. Postanesthesia Care Unit, Miller's Anesthesia 2006; 71: 2703-2727.  Back to cited text no. 3      
4.Smith RA, Kirby RR, Gooding JM, et al. Continuous positive airway pressure (CPAP) by face mask. Crit Care Med 1980; 8: 483.  Back to cited text no. 4      
5.Saul GM, Feeley TW, Mihm FG. Effect of graded administra­tion of PEEP on lung water in noncardiogenic pulmonary edema.Crit Care Med 1982; 10: 667.  Back to cited text no. 5      
6.Antonelli M, Conti G, Rocco M et al. Noninvasive positive­pressure ventilation vs conventional oxygen supplementation in hypoxemic patients undergoing diagnostic bronchoscopy. Chest 2002; 121: 1149-1154.  Back to cited text no. 6      
7.Antonelli M, mailto:[email protected]?subject= Hel­met CPAP Vs Venturi O2 to Treat Early ALI/ARDS., study by ClinicalTrials.gov identifier NCT00342368.  Back to cited text no. 7      
8.Odeberg S, Ljungqvist O, Svenberg T, et al. Haemodynamic effects of pneumoperitonium and the influence of posture during anaesthesia for laparoscopic surgery. Acta Anaesthesiol Scand 1994 ; 38: 276.  Back to cited text no. 8      


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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