Major thoracolumbar spine surgeries
require thoracotomy for achievement of ideal extent of spinal exposure, dissection, decompression and reconstruction. The front of the spine can be operated by transthoracic anterior approach.1
The outcome of spine surgery depends not only on good surgical technique but also on good anaesthetic management. The anaesthesia technique should be such that it provides stable haemodynamics during surgery.
The major complication during spine surgeries is massive blood loss which will be accentuated by inadequate exposure and suboptimal conditions. In anterior exposure to thoracic spine surgeries, these complications can be reduced by intentionally isolating and collapsing lung on operation side. The anterior exposure to thoracic spine can be enhanced by selective lung collapse achieved by one lung ventilation with double lumen endobronchial tube.2
The study was undertaken to evaluate and compare one lung anaesthesia versus two lung anaesthesia in anteriorly approached thoracic spine surgeries. The purpose of this paper is to present technical physiological advantages provided by the use of one lung anaesthesia in thoracic spine surgeries by anterior approach.
Material and Methods
A comparative study was conducted in fifty patients (undergoing thoracic spine surgeries by anterior approach), divided into two groups of twenty-five each. In group I, patientsreceived one lung anaesthesia and group II received two lung anaesthesia. The aim was to compare the efficacy of one lung ventilation with two lung ventilation on the intraoperative haemodynamics, oxygenation, acid base status and complications during thoracic spine surgeries. Even the surgical advantages such as reduced blood loss and duration of surgery, better surgical field exposure during one lung anaesthesia were noticed. Only ASA I and II patients were included of both sexes between 18 and 70 yrs of age. As most of the patients were paraplegic, weight recording was not done. Preanaesthetic evaluation was carried out in all patients and any problems stated to cardiovascular or respiratory system were looked for. Neurological deficit if any were noted. Patients less than 18 yrs of age and with difficult airway and with significant systemic problems were excluded from the study. Apart from routine blood investigations, chest X-ray, ECG were also done. Most of these patients were either paraplegic or with some neurological deficit, with ASA I and II and so pulmonary function tests were not done, therefore proper clinical examination and chest X-ray, baseline ABG analysis were mandatory.
Premedication consisted of Inj. Glycopyrrolate 4 µg/kg intramuscularly and tab Clonidine 3-4 µg/kg half an hour before induction of anaesthesia. Monitoring consisted of ECG, pulse oximetry, intraarterial blood pressure monitoring. After preoxygenation, induction of anaesthesia was done with thiopentone sodium 5-7 mg/kg. Intubation was facilitated by inj. Vecuronium 0.08 - 0.1 mg/kg. Inj. Midazolam 1 mg iv was given for sedation and Inj. Norphine 3 micro/kg for analgesia.
Intubation was done with polyvinyl chloride (PVC) double lumen tube (DLT) so as to enableone lung ventilation during thoracotomies in Group I patients ; while with regular single lumen endotracheal tubes for group II patients. Appropriate position of DLT was confirmed even after lateral decubitus positioning. Anaesthesia was maintained on oxygen and nitrous oxide (50 : 50) initially, propofol infusion for hypotensive anaesthesia and NTG infusion was also started whenever required, in order to maintain MAP minimum upto 70 mmHg.
In group I, One lung ventilation (OLV) was started when the surgeons opened the pleura. During OLV FiO2 was increased to 1.0 and oxygenation to upper lung was maintained by insufflation through Oxygen catheter. In addition, Two Lung Ventilation (TLV) was given with 100 per cent O2 every half hourly for 10 mins and also when saturation decreased below 95%. ABG analysis was done at induction, 10 minutes after commencement of OLV, every one hourly after OLV, at the closure time when there is TLV, post extubation. Intraoperative continuous haemodynamics, saturation and EtCO2 were monitored. Any intraoperative complication, duration of surgery, surgical exposure, total blood loss were noted.
As per demographic profile of the study shown in Table 1, age of the patients in both the groups ranged from 18-70 years. There were no significant differences in two groups regarding sex and operative procedures of the patients. The preoperative mean arterial pressure (MAP) in both the groups was comparable and statistically insignificant. MAP was maintained throughout stable around 70 mmHg in both the groups and there was no significant fall.
Table 1: Demographic profile of study group
||No. of Patients
|Age (18-70 yrs)
||P > 0.05
|Male : Female
||14 : 11
||14 : 11
||P > 0.05
The mean oxygen saturation was never less than 95 per cent in both the groups. Fig. 1 shows that maximum fall in saturation was at 10 mins after initiation of OLV (mean 95.60 ± 2.58) as compared to TLV (mean 99.40 ± 0.50) [p < 0.01], which was then improved after reinflation of upper lung.
Blood gas values in the group I entitled by selective unilateral technique remain practically stable throughout the procedure with no significant deviation from preoperative values except however for a moderate decrease in PO2 and pHt [Table 2]. Maximum fall in PO2 was observed after 10 minutes of OLV (mean 101.80 ± 20.25) as compared to TLV (mean 161.01 ± 65.31) [p < 0.01]. In group I, pH was decreased than baseline value after 10 mins of OLV (mean 7.30 ±0.10) compared to pH value in group II (mean 7.38 ± 0.08). The blood gases in the group ventilated by single lumen tube showed variation between the preoperative and operative values with increase in the PCO2, [p < 0.01] at 2-3 hours after TLV] due to decreased tidal volumes and respiratory frequency during two lung ventilation to improve surgical access and to reduce lung trauma. PaCO2 increase during OLV was much less in comparision with decrease in PaO2 and was corrected by increasing minute ventilation. Only one patient had CO2 increased upto 62 mmHg 10 mins after OLV.
The mean blood loss was 528 ml and 734 ml in group I and II respectively. The average duration of surgery was 171 mins in group I and 247 minutes in group II, [Table 3].
Surgeons graded surgical field as excellent during most of the cases of OLV (64%) as compared to 20% during TLV [Table 4].
Fig. 1 : Comparison of mean SPO2 at various time
intervals between two groups.
Fig.2 : No. of patients with “Complication” in two groups.
As shown in Fig. 2, 8 patients developed intraoperative complications in Group I as compared to 12 patients of group II. Blood loss being more in group II compared to group I except one patient had 3 litres of blood loss during excision of haemangioma at D12 level. 8 patients of group I had fall in oxygen saturation due to venous admixture, intrapulmonary shunting following collapse of the lung within 20 minutes of OLV, while 2 patients of group II had desaturation probably due to hypoventilation to provide immobile lung. Hypercarbia was noticed in 3 out of 25 patients of group II due to hypoventilation. Right to left shunt to upper lung during OLV could lead to hypercarbia which was observed in 2 patients of group I.
In group II during the compression arrhythmias were noted which were self limiting. In group II one patient had hypotension due to blood loss.
Several technical advantages of selective pulmonary ventilation with double lumen tube over the standard single lumen tube ventilation, have been documented numerous times.1,3,4 Most obvious are much improved exposure with a collapsed lung and lack of the need to retract lung vigourosly while maintaining adequate ventilation.
Initially the double lumen tube was used as a mean of preventing contamination of the noninvolved lung but the indications for its use were rapidly expanded by Bjork and associates.5,6
Since one lung ventilation have been advocated not only for pulmonary resection but for a variety of thoracic procedures. Despite advantages, there is some reluctance to the use of DLT routinely in thoracic surgeries due to technical problems with tube placement and complications like desaturation. The major objection to their use is that hypoxaemia may result due to venous admixture caused by total collapse of one lung.7-9 The correct choice and positioning of DLT is crucial, therefore one lung ventilation increases technical and physiological challenge.10,11
In the last few decades spine surgery has evolved into a specialty in its own right. The treatment of spinal deformities evolved from physiotherapy and body casting through surgical approaches for stabilization initially by posterior approach. Recently adopted anterior transthoracic approach provides excellent exposure for repair and stabilization of deformities.1,12 McElvein R. et al13 utilized transthoracic exposure for anterior spinal surgeries. Anterolateral thoracic incision allowed orthopaedic surgeon an unlimited approach to thoracic spine. The surgeries conducted exclusively by one lung ventilation provided improved operative field with the lung collapsed and allowed extensive resection of the affected vertebrae and considerable debridment.2,4,12
In the current study 25 patients (Group I) among 50 patients of ASA Group I and II status undergoing thoracic spine surgeries received one lung ventilation and remaining 25 patients (Group II) received two lung ventilation. An effort has been made in the study to compare two techniques of one lung ventilation and two lung ventilation during thoracic spine surgeries, based on the perioperative haemodynamics, blood gas studies, blood loss and duration of surgery. Aalto et al14 studied cardiorespiratory function during thoracic anaesthesia comparing TLV and OLV with or without PEEP. The transition from TLV to OLV is followed by marked decrease in PaO2. However, in most patients arterial oxygen content is not seriously affected due to maintenance of SaO2 values. In most patients systemic and pulmonary arterial pressures, cardiac output and oxygen delivery were maintained on the same level during OLV as during TLV. Individual changes in oxygen delivery are often due to changes in cardiac output than to changes in arterial oxygen content. They observed that PEEP has no obvious beneficial or deleterious effects on cardiorespiratory functions during OLV.
Generally majority of patients in both the groups remained stable haemodynamically. Throughout the surgeries with both the techniques systolic, diastolic and mean arterial pressure were maintained clinically though there were few statistical difference mean arterial pressure never fallen down below 70 mmHg in both the techniques.
The major objection to the use of one lung ventilation is that hypoxaemia may result due to venous admixture caused by total collapse of the lung. Fall in oxygen saturation in connection with the use of double lumen tubes has been previously reported.7,15 Lunding and Fernandes16 observed decrease in pO2 in most patients receiving OLV, when the chest was opened whether 25, 50 or 100% oxygen was used. The patients with hypoxia were increased, in their study when partial collapse of the lung was made total and that rise in inspired oxygen concentration can abolish hypoxia during both the conditions. They found that with 100 per cent oxygen pO2 was atleast 85 mmHg during total collapse. Malmkvist studied the effect of intermittent inflation of the collapsed lung with oxygen during OLV. PaO2 was always higher in the inflation group than the corresponding times in control group except before the first inflation. In present study the mean oxygen saturation was maintained at 95 per cent even during one lung ventilation. In some cases initiation of OLV was followed by significant decrease in oxygen tension. However in most patients arterial oxygen content is not seriously affected due to maintenance of SaO2 values by maintaining FiO2, 100%, Intermittent reinflation and continuous oxygen insufflation of the collapsed lung.17-19
Even on serial arterial blood gas analysis; mean pO2 was never below hypoxaemic limit i.e. 70 mmHg. Acid base balance does not change significantly in both the groups except few incidences of metabolic acidosis which were corrected. Elimination of carbon dioxide was not significant problem during one lung ventilation.4 The carbon dioxide tension was higher in group II might be because of hypoventilation to keep the lung away from surgical field.
Wood and Campbell4 et al studied physiological and technical advantages of selective unilateral ventilation in more than 200 patients undergoing thoracic procedures without operative mortality and morbidity. The blood gases in selective ventilation remained stable throughout with no significant deviation from preocclusion values except, however moderate decrease in pO2. The group ventilated by single lumen tube showed a definite increase in pCO2 and decreases in pH and pO2 . Although the physiological shunting was five times greater with both techniques as compared to preoperative values, lower values were observed with selective ventilation. Selective unilateral ventilation provides physiological advantages over single lumen tube ventilation because it effects better ventilation of the dependent lung, which has greater perfusion than the contralateral side.
Improvement of surgical exposure due to collapse of the upper lung in one lung ventilation during thoracotomy, significantly reduced the duration of surgery and blood loss during surgery. The comparative study was conducted from 1997-1999 by Dr. Vasant Rao, et al2 between minimal incision technique of endoscopic spinal surgeries and open thoracotomies for thoracic spine surgeries. The one lung anaesthesia was used in both techniques showed reduce duration of surgery with minimal complications.
In this study, three patients of group I had desaturation as compared to 2 patients in group II. Major blood loss occurred in 3 patients of group II as compared to only 1 patient of group I. Hypercarbia was seen in three patients of group II as compared to 2 patients in group I. The incidence of other complication was comparable between two groups.
In conclusion, though one lung ventilation increases technical and physiological challenge,19 it provides advantages over single lumen tube ventilation during anteriorly approached thoracic spine surgeries like improved exposure; minimal blood loss; minimal haemodynamic and ventilatory disturbances. Thus one lung ventilation is a safer and more practical method of ventilation in major thoracic spine surgeries by anterior approach.
- McElevin RB, Nasca RJ, Dunhan WK, et al. Transthoracic exposure for anterior spinal surgery. Ann Thorac Surg 1988; 45 : 278-83.
- Vasanth Rao, Talwalkar L, Chand AK. Endoscopic Spinal surgery and Anaesthetic considerations. Indian Journal Anaesth 2004; 48 (1) : 41-3.
- Nelson A, Burton Donald C Watson, Brodsky JB. Advantages of a New Polyvinyl chloride Double lumen tubes in thoracic surgery. Ann Thorac Surg 1983; 36 (1) : 78-84.
- Wood RE, Campbell D, Razzak MA, et al . Surgical advantages of selective unilateral ventilation. Ann Thorac Surgery 1972; 14 : 173-80.
- Bjork VO, Carlens E. fiberg O. Endobronchial Anaesthesia. Anaesthesiology 1953; 14 : 60.
- Bjork VO, Carlens E. The prevention of spread during pulmonary resection by use of double lumen catheter. J Thorac Surg 1950; 20 : 151.
- Kerr JH, Smith AC, Prys Roberts C, et al. Observation during endobronchial anaesthesia - Oxygenation. Br J Anaesth 1974; 46 : 84-92
- Khanom T, Branthwaite MA. Arterial oxygenation during one lung anaesthesia -A study in man. Anaesthesia 1973; 28 : 132-8.
- Khanom T, Branthwaite MA. Arterial oxygenation during one lung anaesthesia -A study in man. Anaesthesia 1973; 28 : 280-90.
- Benumof JL. Separation of two lungs (DLT insertion). Anaesthesia for thoracic surgery Philadelphia : WB Saunders, 2nd edition 1995 : 330-99.
- Benumof JL. Conventional and differential lung managementof one lung ventilation. Anaesthesia for thoracic surgery Philadelphia : WB Saunders, 2nd edition 1995 : 406-31.
- Mack MJ, Reagan JJ, McAfee PC, et al. Video assisted Thoracic surgery for the anterior approach to the thoracic spinel. Ann Thorac Surg 1995; 59 : 1100-6.
- McElvein RB, Nasca RJ, et al. Transthoracic exposure for anterior spinal surgery. Ann Thorac Surgery 1988; 45 : 278.
- Aalto Setala M, Heinonen J, et al. Cardiorespiratory functions during thoracic anaesthesia. Comparision of TLV and OLV with or without PEEP. Acta Anaesthesia Scand 1975; 19 : 287-95.
- Fiser WP, Friday CD, Read RL. Changes in arterial oxygenation and pulmonary shunt during thoracotomy with endobronchial. J Thorac Cardiovasc Surg 1982; 83 : 523-31.
- Lunding M, Fernandes A, Arterial oxygen tension and acid base stauts during one lung annaersthesia. Acta Anaethesia Scand 1967; 11: 43-53.
- Capan LM, Turndorf H, Chandrakant. Optimization of arterial oxygenation during OLV. Anaesth Analg 1980; 59 : 847-51
- D. Jan Rees, Scott R, Wansbrongh. Percent shunt and arterial oxygen tension during continuous insufflation of oxygen to the nonventilated lung. Anaesth Analg 1982; 61 : 507-12.
- MalmKvist G. Maintenance of oxygenation during one lung ventilation - effect of intermittent reinflation of collapsed lung with oxygen. Anaesth Anlag 1989; 68 : 763-6.
- Benumof JL, Alfrey D. Anaeshesia for thoracic surgery. Anaesthesia, Fifth Edition, Miller RD, Churchill Livingstone ; New York, 2000; 665-752.