Principle of thoracic anesthesia with determinants of operability for resection, One lung anesthesia

Dr. Rajesh Kumar

University College of Medical Sciences & GTB Hospital, Delhi

Indication/contraindication of OLV Physiological changes of OLV Lung separation techniques and

equipments

•Objectives

One-lung ventilation, OLV, means separation of the two lungs and each lung functioning independently.

OLV provides:◦ Protection of healthy lung from infected/bleeding

one◦ Diversion of ventilation from damaged airway or

lung◦ Improved exposure of surgical field

OLV causes:◦ More manipulation of airway, more damage ◦ Significant physiologic change and easily

development of hypoxemia

•Introduction

Absolute ◦ Isolation of one lung from the other to avoid spillage

or contamination Infection Massive hemorrhage

◦ Control of the distribution of ventilation Bronchopleural fistula Bronchopleural cutaneous fistula Surgical opening of a major conducting airway giant unilateral lung cyst or bulla Tracheobronchial tree disruption Life-threatening hypoxemia due to unilateral lung

disease◦ Unilateral bronchopulmonary lavage

•Indication

Relative◦ Surgical exposure ( high priority)

Thoracic aortic aneurysm Pneumonectomy Upper lobectomy Mediastinal exposure Thoracoscopy

◦ Surgical exposure (low priority) Middle and lower lobectomies and subsegmental resections Esophageal surgery Thoracic spine procedure Minimal invasive cardiac surgery (MID-CABG, TMR)

◦ Postcardiopulmonary bypass status after removal of totally occluding chronic unilateral pulmonary emboli

◦ Severe hypoxemia due to unilateral lung disease

•Indication (continued)

Upright position LDP, lateral decubitus position

•Physiology of the LDP

Distribution of ventilation

•Physiology of LDP

Physiological (postpulmonary) shunt About 2-5% CO, Accounting for normal A-aD02, 10-15 mmHg Including drainages from

Thebesian veins of the heart The pulmonary bronchial veins Mediastinal and pleural veins

Transpulmonary shunt increased due to continued perfusion of the atelectatic lung and A-aD02 may increase

•Shunt and OLV

•Two-lung Ventilation and OLV

•OLV and shunt fraction with and without anesthesia

Protective influences in response to the obligatory pulmonary shunt includes the hypoxic pulmonary vasoconstriction, HPV .

HPV, a local response of pulmonary artery smooth muscle, decreases blood flow to the area of lung where a low alveolar oxygen pressure is sensed.

•Physiology of OLV

The mechanism of HPV is not completely understood. Vasoactive substances released by hypoxia or hypoxia itself (K+ channel) cause pulmonary artery smooth muscle contraction

HPV is graded and limited, of greatest benefit when 30% to 70% of the lung is made hypoxic.

But effective only when there are normoxic areas of the lung available to receive the diverted blood flow

•HPV

HPV is inhibited by: volatile anesthetics (not N20),

vasodilators (NTG, SNP, dobutamine, many ß2-agonist),

increased PVR and hypocapnia

PEEP, vasoconstrictor drugs

(preferentially constrict normoxic lung vessels)

•Factors Affecting Regional HPV

Double-lumen endotracheal tube (DLT) Single-lumen ET with a built-in bronchial

blocker, Univent Tube Single-lumen ET with an isolated bronchial

blocker◦ Arndt (wire-guided) endobronchial blocker set◦ Balloon-tipped luminal catheters

Endobronchial intubation with a single-lumen ET

•Methods of OLV

Type:◦ Carlens, a left-sided + a carinal hook ◦ White, a right-sided Carlens tube◦ Bryce-Smith, no hook but a slotted cuff/Rt ◦ Robertshaw, most widely used

All have two lumina/cuffs, one terminating in the trachea and the other in the mainstem bronchus

Right-sided or left-sided available Available size: 41,39, 37, 35,32, 28,26

French (ID=,10.0,9.5,9.0, 8.5, 8.0, 7.0 and 6.5 mm respectively)

•DLT

Schematic diagram depicting passage of the left-sided double-lumen endotracheal tube in a supine patient.A, The tube is held with the distal curvature concave anteriorly and the proximal curve concave to the right and in aplane parallel to the floor. The tube is then inserted through the vocal cords until the bronchial cuff passes the vocalcords. The stylet is then removed. B, The tube is rotated 90 degrees counterclockwise so that the distal curvature isconcave anteriorly and the proximal curvature is concave to the left and in a plane parallel to the floor. C, The tube isinserted until either mild resistance to further passage is encountered or the end of the common molding of the twolumens is at the teeth. Both cuffs are then inflated, and both lungs are ventilated. Finally, one side is clamped while theother side is ventilated and vice versa

1. Blind technique Caution: DLT should pass without any resistanceOptimal depth of insertion for a left sided DLT is ~ patients height ~ 12 +(patients height/10) cm

2. Direct vision technique: uses fiberoptic bronchoscope, however both methods results in successful

placement in approx equal number of patients

•Method of insertion

Alternately blocking the tracheal and bronchial lumen and checking for the air entry.

With the help of fiberoptic bronchoscopy

Chest –x ray

•Confirming position of DLT

•Confirming Position of DLT………

Sex Height(cm) Size(Fr)

Female <160 (63 inches)

35

Female >160 37

Male <170 (67 inches)

39

Male >170 41

•Selection of DLT based on adult patient sex and height

Margin of safety is low : 1. Rt. Upper lobe bronchus is short 2. Rt. u/l bronchus originates at a

distance of 1.5-2 cm from the carina

Fewer indications Doughnut shaped cuff Additional opening for the ventilation of

right upper lobe.

•Right sided DLT

Distorted anatomy of the entrance of a left main stem bronchus

•External or intraluminal tumaour compression•Descending thoracic artery aneurysm

Site of surgery involving the left main stem bronchus

•Left lung transplantation•Left sided tracheobronchial disruption•Left sided pneumonectomy•Left sided sleeve resection

•Indications for a right sided DLT

Most commonly used The bronchial lumen is longer, and a simple

round opening and symmetric cuff. Better margin of safety than Rt DLT

Can be used

◦ Left lung isolation: clamp bronchial + ventilate/ tracheal lumen◦ Right lung isolation: clamp tracheal + ventilate/bronchial lumen

•Left DLT

5%-8% of patients with primary lung carcinoma have a carcinoma of the pharynx as well

Many of these patients have previous radiation exposure or previous surgery done.

They might have distorted anatomy at or beyond carina. eg…descending thoracic aortic aneurysm, intraluminal or extraluminal tumour

Can be detected by chest-x ray and CT scan

•Difficult airway and OLV

A flexible fiberoptic bronchoscopy is essential

Primary goal is to establish an airway with the help of a SLT (awake or anesthetised) f/b the insertion of bronchial blockers.

An alternative is to insert a SLT and then insert DLT with the help of a tube exchanger

•Approach to difficult airway

1. Insertion of a SLT f/b an independent bronchial blocker

2. Use of a disposable cuffed tracheostomy cannula with an independent bb passed coaxially

3. Replacement of the tracheostomy canula with a short DLT such as NARUKE DLT

4. Placement of a small DLT through tracheostomy stoma

5. Oral access to the airway for standard placement of a DLT or blocker

•In a tracheostomised patient

Preanesthetic assessment

Anesthetic management

Postoperative management

•objectives

Fundamentals to anesthetic management of thoracic procedures

•Lung isolation to facilitate surgical access•Management of one lung anesthesia

Preoperative evaluation

done in two disjoint phases:

1. The initial clinical assessment2. The final assessment on the day

of admission

Primary function of PAC

•To identify patients at elevated risk, •To stratify perioperative management and focus resources

•Feasibility of lung resection in a high risk patient

complication incidence

Respiratory(atelectasis, pneumonia,respiratory failure)

15-20 %

Cardiovascular(arrhythmia and ischemia)

10-15%

•Perioperative complications(overall mortality 3-4%)

History Detailed history regarding the quality of life preoperatively

Respiratory mechanics

All patients should have a baseline spirometry:

•FEV1, FVC, MVV, RV/TLC

•FEV1% ( % of predicted volume corrected for age,gender and height).

•ppo FEV1 % ( predicted post operative FEV1 ) Calculated as ppoFEV1 % = preop FEV1 % (1-% functional lung tissue removed/100)

ppo FEV1 % > 40% low riskppoFEV1 % <40% major complicationppo FEV1 % <30% high risk

• Assessment of respiratory functions

Lung parenchymal tests

•ABG parameter : PaO2 < 60mm Hg PaCO2 >45 mmHg( warning indicator of increased risk, however resections are done with these figures nowadays)

•Most useful test : DLCO ppo DLco can be calculated like ppo FEV1•ppo DLco < 40 % increases respiratory and cardiac complications

•PREOP. FEV1 OR DLco < 20% Is UNACCEPTABLE and is the absolute MINIMAL value required. ( national emphysema treatment trial )

•Assessment of respiratory functions continued……………

Laboratory exercise testing

•Gold standard•Vo2 max (maximum oxygen consumption) is the most useful predictor of post operative outcome.•Vo2 max < 15 ml/kg/min is unacceptable•Vo2 max >20 ml/kg/min has fewer complication

EXPENSIVE

Stair climbing tests

•5 flights of stairs ~ V02 max >20 ml/kg/min•2 fight of stairs ~ Vo2 max ~ 12 ml/kg/min -- very high risk(climbing should be at patients own pace without stopping,1 flight of stairs = 20 steps withs each step of 6 inches )

• Assessment of respiratory functions continues………

cardiopulmonary interactions(most important assessment of respiratory function)

Six minute walk test(6MWT)

< 610 m/ 2000 ft ------ Vo2 max< 15 ml/kg/min ~fall in SpO2 > 4% during exercise( increased morbidity and mortality)

ppo V02 max < 10 ml/kg/min is an absolute contraindication mortality rate is approximately 100%

V-P scintigraphy

Should be considerd for any patient of pneumonenctomy having a preop FEV1 &/or Dlco <80%• performed at rest while FEV1 is a forced maneuver

• Assessment of repiratory functions continues……………

Split lung function test

•These tests have not shown sufficient predictive value or validity for universal adoption and are hence not recommended any longer

•Replaced by spirometry/ DLco/ exercise tolerance & V/Q scaning.

• Assessment of repiratory functions continued……………

Respiratory mechanics

FEV1(ppo>40%) MVV, RV/TLC, FVC

Cardiopulmonary reserve

Vo2 max >15ml/kg/min

Stair climbing>2 flight

6MWT>610m/2000ft

Exercise SpO2 < 4 %

Lung parenchymal

function

Dlco (ppo >40%) PaO2 >60PaCO2 <45

• The three legged stool of pre thoracotomy respiratory assessment

•Ischemia : intermediate risk surgery

• 5% incidence post thoracotomy

• peaks on 2 and 3rd post op day

• ACC/AHA guidelines to be followed

•Arrhythmias•Right ventricular

dysfunction

cardiovascular

•Perioperative mortality is 19% in pt. developing deranged KFT in periop. Period as against 0% in those having normal KFT

•Increased risk in pt. having h/o renal impairment

• use of diuretic

• use of NSAIDS

•Hence I/op fluid management and intensive perioperative fluid management is essential

Renal dysfunction

•Rate of respiratory complication doubles(40%) and cardiac complications (40%) triples in elderly

Age

•Concomitant medical conditions

Problems in a COPD patient

Respiratory drive,CO2 retainers,

Increased role of HPV

Nocturnal hpoxemia because of rapid shallow breathing in a REM sleep

Right ventricular dysfunctionBullaeFlow limitation : stage I :FEV!>50% no significant dyspnoea ,hypoxemia or hypercapniaStage III :FEV1 <35% --life expectancy <3 years post thoracotomy

•Concomitant medical conditions continues…….

Time Course Beneficial Effects

12–24 hr Decreased CO and nicotine levels

48–72 hr COHb levels normalized, ciliary function improves

1–2 wk Decreased sputum production

4–6 wk PFTs improve

6–8 wk Immune function and metabolism normalizes

8–12 wk Decreased overall postoperative morbidity and mortality

•Beneficial effects of smoking cessation and time course

Mass effects Obstructive pneumonia,lung abscess, superior vena cava syndrome, tracheobronchial distortion , pancoast syndrome, recurrent laryngeal nerve or phrenic nerve palsy, chest wall or mediastinal extension

Metabolic effect

Lambert – Eaton syndrome, hypercalcemia, hyponatremia, cushing syndrome

Metastases Particularly to brain, bone , liver and adrenal

Medications Chemotherapy agents , pulmonary toxicity ( bleomycin,mitomycin C), cardiac toxicity(doxorubicin), renal toxicity ( cisplatin )

•Anesthetic considerations in lung cancer patients (“the 4 Ms” )

•Preoperative therapy for COPD

the risks and benefits of the

various forms of post-

thoracotomy analgesia should be explained to

the patient

Potential contraindication

s such as coagulation problems, sepsis, or neurologic

disorders should be determined

American Society of Regional

Anesthesia (ASRA)

an interval of 2 to 4 hours

before or 1 hour after catheter placement for prophylactic

heparin administration.

an interval of 12 to 24 hours

before and 24 hours after

catheter placement is

recommended for LMWH

•To discuss post op analgesia

>40%

•Extubate in the OR

•Patient AWaC (alert ,warm and comfortable)

30-

40%

•Extubation on the basis of

•Exercise tolerance,Dlco,V/Q scan, associated diseases

<30%

•Staged weaning

•Consider extubation if >20% + thoracic epidural analgesia

• Think about post thoracotomy anesthetic management(based on ppo FEV1%)

High percentage of ventilation or perfusion to the operative lung

preoperatively

Poor PaO2 during two-lung ventilation particularly in the lateral position

intraoperatively

Right sided thoracotomy

Normal preoperative spirometry or restrictive lung disease

Supine position during OLV

• Increased risk of hypoxemia

avoid inadvertent withdrawal of those drugs that are taken for concurrent medical conditions

For surgeries like oesophageal reflux surgeries aspiration prophylaxis are routinely ordered preoperatively

do not routinely order preoperative sedation or analgesia for pulmonary resection patients

Mild sedation short-acting benzodiazepine is often given immediately before placement of invasive monitoring lines and catheters.

an antisialagogue (e.g., glycopyrrolate) is useful to facilitate fiberoptic bronchoscopy

It is a common practice to use short-term intravenous antibacterial prophylaxis

•Premedication

Oxygenation : significant desaturation( SpO2<90%) occurs in 1-10% of

patients inspite of high FiO2 (1.0). PaO2 offers a better margin of safety then SpO2 Decreased initial PaO2 and rapid fall in PaO2 after initiation

of OLV is a good indicator of subsequent desaturation. Useful to measure PaO2 before and 20 minutes after OLV

Capnometry Less reliable then PaCO2 PaCO2-EtCO2 gradient increased

Other components of minimum mandatory monitoring : BP,ECG,temperature

•Intraoperative monitoring

Arterial line:Surgical compression of heart & great vessels l/t hypotension•CVP : non reliable , useful postoperatively•Pulmonary artery catheters: less reliable for OLV• unsurety about the location of the tip• signficant u/l differences in lung perfusion.• complications

Continuous spirometry monitoring of inspired and expired volume auto-PEEP•aids in assessing and managing pulmonary air leak during

pulmonary resection

Transesophageal echocardiography :continuous real time monitoring ofmyocardial function and preload•Potential indication: hemodynamic instability,pericardial

effusion,cardiac involvement by tumour,air emboli,pulmonary thromboendarterectomy, thoracic trauma,lung transplantation.

•Difficult in pt. having esophageal pathology,

•Invasive monitoring

The majority of thoracic procedures are performed with the patient in the lateral position

monitors will be placed and anesthesia will usually be induced with the patient in the supine position

hypotension on turning the patient to or from the lateral position

All lines and monitors will have to be secured during position change and their function reassessed after repositioning

anesthesiologist should take responsibility for the head, neck, and airway during position change

Endobronchial tube/blocker position and the adequacy of ventilation must be rechecked by auscultation and fiberoptic bronchoscopy after patient repositioning.

•Positioning

1.    Dependent eye    2.    Dependent ear pinna    3.    Cervical spine in line with thoracic spine  4.    Dependent arm:    a.    Brachial plexus    b.    Circulation    5.    Nondependent arm :    a.    Brachial plexus    b.    Circulation   

• “Head-to-toe” survey for neurovascular injury after position change

Fluid Management for Pulmonary Resection Surgery

   1.    Total positive fluid balance in the first 24-hour perioperative period should not exceed 20 mL/kg.

   2.    For an average adult patient, crystalloid administration should be limited to < 3 L in the first 24 hours.

   3.    There should be no fluid administration for third space fluid losses during pulmonary resection.

   4.    Urine output > 0.5 mL/kg/hr is unnecessary.

   5.    If increased tissue perfusion is needed postoperatively, it is preferable to use invasive monitoring and inotropes rather than to cause fluid overload.

•Anesthetic management

use of N2O/O2 mixtures is associated with a higher incidence of post-thoracotomy radiographic atelectasis (51%) in the dependent lung than when

air/oxygen mixtures are used (24%).

also tends to increase pulmonary artery pressures in patients who have pulmonary hypertension

N2O inhibits HPV

N2O is contraindicated in patients with blebs or bullae

N2O is usually avoided during thoracic anesthesia

Use of nitrous oxide

anesthetic technique should optimize the myocardial oxygen supply/demand

Thoracic epidural anesthesia/analgesia is recommended high incidence of coexisting reactive airway disease,

added airway manipulation by the DLT or bronchial blocker

Thus, need anesthetic technique that decreases bronchial irritability, causes bronchodilation, and avoids release of histamine

For intravenous induction of anesthesia either propofol or ketamine, & for maintenance of anesthesia, propofol and/or any of the volatile anesthetics are recommended

•Cardiovascular and Respiratory goals

All of the volatile anesthetics inhibit HPV in a dose-dependent fashion :

◦ halothane > enflurane > isoflurane

In doses less than or equal to 1 MAC, the modern volatile anesthetics depress HPV minimally

Hence TIVA has no proven benefit against 1 MAC inhalational anesthesia

•Choice of Anesthetic

Parameter Suggested Guidelines/ Exceptions

Tidal volume 5-6 mL/kg Maintain:

  Peak airway pressure < 35 cm H2O

  Plateau airway pressure < 25 cm H2O

Positive end-expiratory pressure

5 cm H2OPatients with COPD: no added PEEP

Respiratory rate 12 breaths/min

Maintain normal Paco2; Pa-ETco2 will usually increase 1-3 mm Hg during OLV

Mode Volume or pressure controlled

Pressure control for patients at risk of lung injury (e.g., bullae, pneumonectomy, post lung transplantation)

Suggested ventilatory parameters for OLV

 Therapies for Desaturation during One-Lung Ventilation

Severe or precipitous desaturation: Resume two-lung ventilation (if possible).

Gradual desaturation:

   1.    Ensure that delivered Fio2 is 1.0.

   2.    Check position of double-lumen tube or blocker with fiberoptic bronchoscopy.

   3.    Ensure that cardiac output is optimal; decrease volatile anesthetics to < 1 MAC.

   4.    Apply a recruitment maneuver to the ventilated lung (this will transiently make the hypoxemia worse).

   5.    Apply PEEP 5 cm H2O to the ventilated lung (except in patients with emphysema).

   6.    Apply CPAP 1-2 cm H2O to the nonventilated lung (apply a recruitment maneuver to this lung immediately before CPAP).

   7.    Intermittent reinflation of the nonventilated lung

   8.    Partial ventilation techniques of the nonventilated lung:   

a.    Oxygen insufflation   b.    High-frequency ventilation   c.    Lobar collapse (using a bronchial blocker)

   9.    Mechanical restriction of the blood flow to the nonventilated lung

• Respiratory failure

• cardiac herniation

• torsion of a remaining lobe after lobectomy

• dehiscence of a bronchial stump

• hemorrhage from a major vessel

•Post operative complications

Early major

leading cause of postoperative morbidity and mortality

Acute respiratory failure after lung resection is defined as:

◦ acute onset of hypoxemia (PaO2 < 60 mm Hg) or hypercapnia (PaCO2 > 45 mm Hg

◦ use of postoperative mechanical ventilation for more than 24 hours

◦ reintubation for controlled ventilation after extubation

◦ incidence of respiratory failure after lung resection is between 2% and 18%

•Post operative respiratory failure

thoracic epidural analgesia :

prevention of atelectasis and

secondary infections

better preservation of the functional

residual volume

efficient mucociliary clearance

alleviation of the inhibiting

reflexes acting on the

diaphragm

Chest physiotherapy,

incentive spirometry, and

early ambulation are

crucial

provide better oxygenation, treat

infection, and provide vital organ

support without further damaging

the lungs.

• To minimise pulmonary complications postoperatively

•incision (intercostal nerves T4-T6),

•chest drains (intercostal nerves T7-T8),

•mediastinal pleura (vagus nerve, CN X),

•central diaphragmatic pleura (phrenic nerve, C3-C5),

•ipsilateral shoulder (brachial plexus).

multiple sensory afferents :

Hence there is no one analgesic technique that can block all these various pain

afferents, so analgesia should be multimodal.

The ideal post-thoracotomy analgesic technique will include three classes of

drugs: opioids, anti-inflammatory agents, and

local anesthetics.

Post operative analgesia

•Opioids:effective in controlling background pain but the acute pain component associated with cough or movement requires plasma levels that produce sedation and hypoventilation

•NSAIDS :reduce opioid consumption more than 30%.particularly useful treating the ipsilateral shoulder pain

•Ketamine: less respiratory deppression

•Dexmedetomidine: described as an useful adjunct

Systemic Analgesia:

•Intercostal nerve blocks

•Interpleural blocks

•Epidural analgesia

Local Anesthetics/Nerv

e Blocks:

Post op analgesia continues…

Thank you