|Year : 2008 | Volume
| Issue : 2 | Page : 185-190
Management of Postoperative Hypoxaemia in Patients Following Upper Abdominal Laparoscopic Surgery. - A Comparative Study
Sampa Datta Gupta1, Anjana Pareek2, Tapas Ghose3, Ujjal Kumar Sarkar4, Sudakshina Mukherjee4, Anupam Goswami5, Debabrata Sarbapalli5, Samarendra Pal5
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 Acceptance||22-Feb-2008|
|Date of Web Publication||19-Mar-2010|
Sampa Datta Gupta
42 Lake Place. 1st floor. Kolkata 700029
Source of Support: None, Conflict of Interest: None
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 2021 May 12];52:185-90. Available from: https://www.ijaweb.org/text.asp?2008/52/2/185/60619
| Introduction|| |
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 %. 
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. 
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.  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.  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.  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. 
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|| |
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.
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
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.
- 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.
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,
Total sample size (n = 40) was determined by power analysis from the means and standard deviation obtained from a previously done pilot study.
- 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.
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 -
Criteria for endotracheal intubation -
- 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.
Predetermined criteria for endotracheal intubation would be identical for all groups and would include one of the following:
Untoward effects like vomiting and intolerance to therapy were observed and noted during the study and managed accordingly.
- 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)
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|| |
[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|| |
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  . 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  .
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  .
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  .
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.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]