Lung resection

Journal Reviewed:  Journal of Cardiothoracic and Vascular Anaesthesia
Issues: April 2000: Volume 14: Number 2
Abstracted by: Dr R Ing  FCA (Consultant Anaesthesiologist, University of the Witwatersrand)

Summary of abstracts

It is not the anaesthesiologists decision which patients are operative candidates. This must be decided by the patient (once given all possible information), the surgeon, and the doctors who are responsible for the post operative management of the patient.
The anaesthesiologist needs to review the patient's history and examination with the anaesthetic management in mind. A systematic approach allows the anaesthesiologist to anticipate problems and plan solutions prior to starting. You may also wish to briefly browse our editorial comment

1.  Preoperative Assessment for Lung Resection.

The authors of this valuable article, after a few telling generalisations, get down to the business of reviewing the 'state of the art' in assessing patients for lung resection. They note that perioperative complications are predominantly respiratory, so respiratory assessment is of paramount importance.

Initially, one can define a small subset of the population who have normal or near-normal effort tolerance. Such ASA I or II patients do NOT require further respiratory evaluation prior to lung resection. Unfortunately, most patients fall into the larger group where the lung tumour (or other indication for lung resection) is due to smoking that has also exacted its toll on pulmonary function. The authors, despairing of a single test that will predict outcome, fall back on a 'tripod' of assessment criteria:

  1. Assessment of respiratory mechanics;
  2. Determining adequacy of gas exchange; and
  3. Evaluation of cardio-respiratory reserve.

Respiratory Mechanics

For years, predicted post-operative FEV1 has been regarded as a valuable predictor of outcome. To a certain extent, this is still probably valid. The level of predicted post-operative FEV1 that the authors recommend as a 'cut-off' is 40% of normal for that individual. Any patient with a value lower than this 40% of predicted, needs further investigation prior to surgery. (Other possible parameters are the maximum voluntary ventilation, forced vital capacity or even residual volume divided by total lung capacity).

A convenient method of prediction of post-operative FEV1 is to estimate the amount of functional lung tissue remaining after surgery based on the number of 'subsegments' in each lobe. The authors' figure 2, sketched below, is useful:

A schema of the lungs showing the relative contribution of each lobe

For example, if the preoperative FEV1 is 1.8 litres and a right pneumonectomy is to be done, assuming uniform contributions to FEV1 from all subsegments, the predicted post-operative FEV1 is:

        FEV1 ppo = (20 / 42) * 1.8 = 0.86 litres,

as there will be 20 subsegments left after the 22 subsegments in the right lobe have been removed. The calculations for other predicted post-operative values (such as DLCO and VO 2 max) are similarly calculated. It would seem wise to always relate values to the normal prediction for that individual rather than nominating blanket cut-off values such as a predicted FEV1 of "under 1.0 litres".

For practical application of a similar (but not identical) formula, see the paper by Kearney et al (Chest 1994, 105(3) 753-9), where multivariate analysis showed only predicted FEV1 as a significant independent predictor of morbidity. The death rate in this study was an impressively low 1%. Of interest is that in this study age, gender, smoking history, hypercarbia, desaturation on exercise, and preoperative FEV1 under 1 litre were all NOT predictive of outcome.

Gas Exchange

The most useful test of the gas exchange capacity of the lung is the DLCO. A ppoDLCO less than 40% predicted for that patient correlates with increased respiratory and cardiac complications, and is independent of FEV 1 . The traditional values of a PaO 2 of over 60 mmHg and PaCO 2 of under 45 mmHg are questioned as reasonable cut-offs. The authors note that these latter criteria are not absolute contra-indications to surgery, with successful resections now taking place in patients violating the PaO 2 and PaCO 2 criteria, sometimes even combined with lung reduction surgery!

Cardio-respiratory reserve

Although the benchmark for prediction of outcome is still regarded by many as a predicted post-operative maximum VO 2 (VO 2 max), this has been shown to correlate well with patient effort tolerance, notably stair-climbing (3 or more flights of 20 steps/flight at 15 cm/step is acceptable), and the distance walked in 6-minutes (under 650 meters is distinctly poor, correlating with a VO 2 max of under 15 ml/kg). It is suggested (without considerable supporting literature) that the 6-minute walk and exercise oximetry might replace VO 2 max determination.

If one adheres to the time-honored gold-standard of VO 2 max, it is has been claimed that a value under 10 ml/kg/min precludes surgery, and that with values of over 20 ml/kg/min complications are infrequent.

A systematic review of respiratory function

The following approach is recommended:-

  • All Patients
    • Exercise tolerance
    • ppoFEV 1
    • Post-operative analgesia explained
    • Discontinue smoking
  • ppoFEV 1 <40%
    • DLCO
    • Echocardiography specifically to see right ventricular function
  • Cancer Patients
    • Mass effects - Obstructive pneumonia, Lung abscess, SVC syndrome, tracheobronchial distortion, Pancoast's syndrome, recurrent laryngeal nerve or phrenic nerve paresis, chest wall or mediastinal extension
    • Metabolic effects - Eaton-Lambert syndrome, hypercalcaemia, Cushing's syndrome
    • Metastases - Brain, bone, liver and adrenal glands
    • Medications - Pulmonary toxicity (bleomycin, mitomycin), cardiac toxicity (doxorubicin), renal toxicity (cisplatin).
  • COAD Patients
    • Arterial blood gas
    • Physiotherapy
    • bronchodilators
  • Patients with and increased risk of renal failure
    • Electrolytes
    • Creatinine
    • Urea

Expected post thoracotomy anaesthetic management
Predicted postoperative FEV 1

>40% 30-40% <30%
Early extubation
Ensure the patient is warm, comfortable and alert.
Consider Extubation
Consider the results of the exercise test, DLCO, Echo and associated diseases
May need staged weaning from mechanical ventilation.

Thoracic epidural analgesia

In addition, the article contains many valuable pointers for the practising anaesthetist. These include sections on evaluation of other intercurrent disease, pre-operative optimization (including steroids, physiotherapy, cessation of smoking and lessening the impact of neoplasms both locally and systemically), analgesia, and pointers on assessing the ease of lung isolation which can be obtained from the pre-operative plain chest film and CT scan.
A review of the respiratory drive in COAD patients explains why giving oxygen, which may slightly increase their carbon dioxide levels, is still essential and will NOT cause apneoa!
The section on predicting desaturation during one-lung ventilation is also a good read. All in all, a rewarding and worthwhile article!

Article 1: Preoperative Assessment for Pulmonary Resection
Journal:  J Cardiothorac Vasc Anesth, Vol 14, No 2, 2000: 202-211
Article type:  Literature Review
Authors:  Slinger PD, Johnston MR


Editorial pointers


There have been several recent articles examining the vexing question "How do we pre-operatively assess the risk of lung resection?" The overall tone of these articles has been similar. Interested readers might wish to consult the article highlighted above, or one of the following:

Bolliger CT, Perruchoud AP European Respir J 1998 11 198-212

Wyser C, et al Am J Respir Crit Care Med 1999 159 1450-6

A recurrent emphasis in all of these articles is performing tests of exercise tolerance and/or predicting post-operative pulmonary function. Wyser et al went so far as to apply Bolliger's formal stepwise algorithm to assess patient suitability for surgery, with five out of 137 patients being deemed 'unsuitable' (two on the basis of ischaemic heart disease, and three on the basis of a low VO 2 ), and the remainder undergoing surgery.

We are intrigued by several points:

  1. The 'absolute' rejection criterion of a VO 2 max of under 10 ml/kg/min that we encounter in several studies is based on very few cases. We read of one study where three patients had a VO 2 max of under 10, and all died (Bolliger CT et al, Chest 1995 Aug 108(2) 341-8, also published in German in Pneumologie 1996 May 50(5) 334-41); in an older study (Bechard D & Wetstein L, Ann Thorac Surg 1987 Oct 44(4) 344-9) 3/7 patients with a VO 2 max under 10 ml/kg/min died. Does anyone have a large series of patients with such low values for VO 2 max? We doubt it.

  2. If a patient has very poor 'objective criteria', and a small peripheral non-small-cell carcinoma (NSCC) of the lung, should they be denied surgery? In the series of Bechard and Wetstein, four out of seven patients with 'ultra-low' VO 2 's still survived ! If you consider that a patient with NSCC is doomed to die nastily if the tumour is not resected, these may seem like good odds.

  3. Perhaps the most striking deficiency in all of the studies that we have encountered is a failure to assess the patient as a whole. There is a considerable literature attesting to the importance of pre-operative nutritional status as a predictor of post-operative outcome, yet none of the studies above even mentions the nutritional status of patients undergoing lung resection.

We are left with the uneasy feeling that rather than performing complex, expensive and poorly predictive tests, the authors of the various studies should sit down and talk to their patients, perhaps perform a subjective global assessment of their nutritional status, and limit pulmonary assessment to a brisk six-minute walk, and perhaps an FEV1 related to the magnitude of the planned surgery!



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