OBSTRUCTIVE SLEEP APNOEA

AND ANAESTHESIA

BY Dr. Chamika HuruggamuwaRegistrar in Anaesthesiology

TH KANDY

INTRODUCTION

• OBSTRUCTIVE SLEEP APNOEA (OSA) is a sleep-related breathing disorder characterized by repeated episodes of Apnoea and Hypopnoea during sleep.

• SLEEP DISORDERED BREATHING IN CHILDREN• SDB in children encompasses primary snoring, upper airway

resistance syndrome, obstructive hypopnoea and obstructive sleep apnoea

• Primary snoring is defined as noisy breathing during sleep without desaturation or obstructive episodes and without daytime symptoms.

• Upper airways resistance syndrome (UARS) is defined as snoring associated with sleep disruption and arousal, with daytime symptoms but no abnormalities of gas exchange at night.

• Obstructive hypoventilation (OH) occurs when upper airways resistance is increased sufficient to cause paradoxical ventilation (loss of synchrony between thoracic and abdominal movements), with desaturation and or carbon dioxide retention.

• Obstructive sleep apnoea (OSA) is the most severe form of SDB when children demonstrate cessation of nasal/oral airflow during sleep with preserved thoracic and abdominal respiratory effort and oxygen desaturation

• Apnoea -Complete cessation of airflow for more than 10 seconds

• Hypopnoea - Airflow reduction more than 50% for more than 10 seconds.\

‘OSA syndrome’

• Clinical entity of OSA resulting in • Excessive daytime sleepiness• Other symptoms such as unrefreshing sleep, poor

concentration, fatigue and morning headaches.

EPIDEMIOLOGY• In middle age, the prevalence of overt OSA is

approximately 4% in men and 2% in women• It is estimated that 80% of patients are undiagnosed, with

sleep study data estimating sleep disordered breathing having a prevalence of 24% in men and 9% in women.

• OSA is strongly correlated with obesity, in particular morbid obesity (Body mass index >40 kg/m2, or a BMI >35 kg/m2 with significant co-morbidities).

• It is found in 40% of obese females and 50% of obese males.

The most common aetiology of SDB in children is

• Adenotonsillar hypertrophy.• chromosomal abnormalities such as Downs syndrome• craniofacial abnormalities associated with severe mid-face hypoplasia such

as Aperts or Crouzons syndrome; Treacher-Collins or Pierre Robin sequence• (micrognathia); cerebral palsy (hypotonia); sickle cell disease (lymphoid

hyperplasia); papillomatosis,• cystic hygroma (foreign body). • Obesity is becoming an increasingly common cause of OSA in older children

PATHOPHYSIOLOGY• The body is in its most relaxed state during REM sleep, Tone of the pharyngeal dilator muscles(musculus genioglossus and musculus geniohyoideus)

Pharyngeal Airways Collapse - Airway obstruction Inspiratory efforts increase

Negative pressures produced by the diaphragm and intercostal muscles promote a collapse of the oropharynx

With airway obstruction,

Inspiratory efforts increase as arterial oxygen desaturation

Partial arousal from sleep and a sudden opening of the airway.

A short period of hyperventilation follows, until sleep deepens and airway obstruction recurs,

Repeating the cycle.

The result is blood gas oscillation and sleep fragmentation

In obese patients,• increased adipose tissue in the neck and pharyngeal

tissues narrows the airway further, predisposing to airway closure during sleep.

In non-obese patients, • Tonsillar hypertrophy or craniofacial skeletal

abnormalities may lead to airway narrowing and sleep apnoea.

OSA In Pregnancy

• During pregnancy, intermittent SDB occurs in more than 50% of women. Snoring and OSA are independently linked to hypertension in pregnancy.

• CPAP therapy has been demonstrated to be a safe and acceptable adjunct for blood pressure management in the group of women with OSA and associated hypertension.

• Some reports have associated fetal growth retardation with OSA

Physiological changes Arising from repetitive airway obstruction

• Arterial hypoxaemia, • Arterial hypercarbia, • polycythaemia, • systemic hypertension, • pulmonary hypertension, • cardiac rhythm disturbances and • Right ventricular failure. • There is an increased incidence of heart disease, cerebrovascular events and

sudden death.

Children with OSA have

• Failure to thrive, .• possibly due to reduced caloric intake, increased work of

breathing at night, or reduced secretion of growth hormone • CNS complications • Learning and behavioural problems as a consequence of sleep

disturbance. • There is some evidence that the CNS complications may be related to

an inflammatory response secondary to repeated nocturnal hypoxia.

• Cardiovascular complications.• Severe OSA with repeated nocturnal hypoxia is associated

with pulmonary hypertension • may result in right heart failure.

Diagnosis of OSA

• History and Examination• Predisposing conditions combined with a

• history of snoring, • restless sleep, • headaches,• and daytime sleepiness should alert to the possibility of OSAS

STOP-BANG questionnaire

Polysomnography (psg)PSG examinations includeRecordings of heart rhythm (ECG), Electroencephalography (EEG), Blood pressure,Eye movements,Electromyography.

Snoring volume,Oro-nasal airflow, Peripheral pulse oximetryare usually also recorded.

The Apnoea/Hypopnoea Index (AHI)

• Number of Apnoea and Hypopnoea periods lasting 10 s or longer per hour of sleep

The American Academy of Sleep Medicine• definitions of Hypopnoea to include • (i) 30% airflow reduction and 4% desaturation or • (ii) 50% reduction in nasal pressure signal excursions with

associated 3% desaturation or arousal, respectively

• AHI > 5 mild• > 15 moderate OSA• >30 severe

RISKS ASSOCIATED WITH ANAESTHESIA• OSA is associated with increased peri-operative morbidity and

mortality. • The peri-operative risk increases in proportion to the severity of

OSA. Sedation, Analgesia or Anaesthesia

potential loss of the airway caused by the use of anaesthetic, sedative and opioid drugs

• Difficult intubation and postoperative respiratory depression and airway obstruction are also possible.

PREOPERATIVE MANAGEMENT

• Preoperative Screening STOP-Bang model• signs of cardiomegaly -CXR. may demonstrate prominent central

pulmonary arteries. An ECG reveals signs of right ventricular hypertrophy (right axis deviation, peaked P waves, tall R waves in lead V1).

• Echocardiography confirms the diagnosis of • Pulmonary hypertension, Right ventricular hypertrophy +/-

dilatation. • Adenotonsillar hypertrophy may contribute in part to OSA and

these children may benefit from tonsillectomy.

Preoperative treatment• The gold standard of treatment for OSA is the nocturnal

use of nasal continuous positive airway pressure (nCPAP) delivery devices.

• A nasal mask provides positive airway pressure • Pressure requirements range from 5 to 20 cmH2O,

depending on the severity of the obstruction. • Preoperative use of nasal CPAP may lead to improvement

in condition prior to surgery and better postoperative compliance with the device.

• Mandibular advancement devices may be used for mild OSA. These devices position the mandible forward, pulling the tongue away from the posterior pharyngeal wall.

• Uvulopalatopharyngoplasty is no longer performed for the surgical management of OSA.

• Preoperative weight loss can also be recommended.

Preoperative planning• Elective surgery should be postponed until the patient has

been fully investigated and treated. • Review of previous anaesthetic notes grading ease of

direct laryngoscopy and intubation should be sought.

INTRAOPERATIVE MANAGEMENT

• Premedication• BDZs as premedication relaxes upper airway musculature,

reducing the pharyngeal space

• hypopnoea, and consequently hypoxia and hypercapnia preoperatively.

• Ideally all sedative premedications should be avoided, or used extremely cautiously.

Choice of Anaesthetic Technique

• Local or Regional Anaesthesia is preferred mode of anaesthesia.

• General anaesthesia with a secured airway is preferred to deep sedation without a secure airway.

• Intraoperative CPAP may be helpful.

• Common anaesthetic drugs that have been shown to cause pharyngeal collapse include

• propofol, TPS, opioids, BDZ, NMB and N2O

Intubation technique

• OSA Difficult intubation.

• Cormack laryngoscopy grade III and IV views in 90% of patients with OSA

• Equipment necessary to handle a difficult airway should be readily available prior to induction,

• Adequate preoxygenation• Laryngoscopy optimal ‘sniff’ position.• Awake fibreoptic intubation should be made if an airway problem is

suspected.. • Adverse effects associated with difficult airway management include

death, brain injury, cardiorespiratory arrest, airway trauma and damage to teeth.

• Children with severe OSA have increased opioid sensitivity and have been estimated to require 50% less opioid than normal children

• This is postulated to be due to up-regulation of μ opioid receptors

• Simple analgesics should be used (and for general• surgical procedures in children with OSA, regional

blocks); • opioid analgesia should be kept to a minimum in the

postoperative period.

Extubation• The patient conscious, communicative, and breathing

spontaneously with an adequate tidal volume and oxygenation.

• semi-upright or lateral position, after complete reversal of neuromuscular blockade.

• OSA was independently associated with significantly increased odds of emergent intubation and mechanical ventilation, NIV, respiratory failure, and atrial fibrillation

• Mokhlesi B, Hovda MD, Vekhter B, Arora VM, Chung F, Meltzer DO. Sleep-disordered breathing and postoperative outcomes after elective surgery: analysis of the nationwide inpatient sample. Chest 2013;144:903–14

POSTOPERATIVE MANAGEMENT• Respiratory depression and repetitive apnoeas are common immediately

following extubation.• Supplemental oxygen should be administered continuously to all OSA patients

until they are able to maintain their baseline oxygen saturation whilst breathing room air.

• The ASA recommend OSA patients should be monitored for three hours longer than usual before being discharged from a facility.

• Oxygen administration will not prevent apnoea

Reduce the duration of apnoea and the degree of resulting oxygen desaturation.• postoperative nasal continuous airway pressure

• Upper airway surgery - prolonged period of tracheal intubation postoperatively, in view of the potential for significant airway swelling

• HDU/ICU care• Adequate pain relief remains a priority in OSA• Non opioid analgesics –PCM,Tramadol,clonidine,ketamine,NSAIDS.• Regional nerve blocks

• Day-case surgery and OSA???

• Sufferers of OSA, due to their fragmented poor quality sleep, are a potential danger to themselves and to others who may be dependent upon their judgement and vigilance,,,,,,,,……

• awareness of the potential of OSA in ourselves must be considered if we are to perform our anaesthetic duties without endangering the lives of our patients.

THANK YOU…..!!!