ISAKanyakumari - Anaesthesia Practice in Kanyakumari District

ANAESTHESIA PEARLS

ANAESTHETIC CONSIDERATION
POSTOPERATIVE PAIN MANAGEMENT
SAFE EXTUBATION

ANAESTHETIC CONSIDERATION IN AIDS PATIENTS

Dr.R. Selvakumar. M.D.D.A.DNB

Professor of Anaesthesiology,

K.A.P.Viswanatham Govt Medical College,

Trichy. Tamilnadu

The proportion of HIV infected patients coming up for surgical treatment for the co-incident illness is on the rise. The statistics says that around 38 million people are infected with the HIV virus worldwide(2008) out of them, atleast 25% of the people present themselves for incidental surgeries. So, anaesthesiologists, being involved in the anaesthetic and critical care and pain relief need to know the implications of the disease and the drugs given to treat it. An understanding of the pathogenesis of HIV and awareness of the possible drug interactions occurring with HIV therapy may help to guide the choice of anaesthetic techniques. The possibility of nosocomical transmission of HIV higelights the need for anaesthetists to enforce rigorous infection control policies to protect themselves and other theatre personnel.

NAESTHETIC CONSIDERATION IN AIDS PATIENTS

Background :

HIV is a single stranded RNA virus of the lentivirus subfamily of the reterovirus family. Two subtypes have been identified –HIV-1and HIV-2. At present , two major groups of HIV-1 subtypes have been recognized(HIV-10 and HIV-1M) . Like other reteroviruses, HIV contains the enzyme reverse transcriptase that enables viral RNA to be transcribed to DNA, which then becomes incorporated into the host cell genome and is able to replicate freely. HIV preferentially infects T helped lymphocytes(CD4 T cells) and leads to their progressive quantitative and qualitative destruction, making the host more susceptible to opportunistic infections and maliguancies.

Modes of transmission :

HIV is a virus found mainly in CD4 Tcells, macrophages and monocytes and requires a large infecting dose for transmission. HIV has been isolated from blood,CSF,Tears,saliva semen,synocial fluid, pleural fluid, peritoneal and pericardinal fluid, amniotic fluid, vaginal secretions and breast milk.

Several modes of transmission of infection exist including sexual intercourse (60-70%), mother to child transmission (during pregnancy, labour and breast feeding) (20-30%) contaminated blood, blood products(3-5%)and contaminated needles.

Clinical staging of HIV infection :

1. Asymptomatic

	No symptoms.
	Persistent generalized lymphadenopathy.

2. Mild symptoms:

	Moderate weight loss.
	(<10% body weight).
	Recurrent upper respiratory tract infection.
	Viral or fungal skin infection.
	Oral or skin lesion.

3. Advanced symptoms :

	Severe weight loss (>10% body weight).
	Chronic diarrhea, Persistent fever.
	Oral lesions or candidiasis.
	Pulmonary tuberculosis.
	Severe bacterial infections.
	Anaemia, neutropenia, thrombocytopenia.

4. Severe symptoms :

	Wasting syndrome.
	AIDS (weight loss >10% body weight with wasting or body mass index <18.5).
	Chronic diarrhea, Persistent fever.
	Encephalopathy, nephropathy, cardiomyopathy.
	Recurrent bacterial infections, Opportunistic infections, Malignancy.

Pathophysiology of HIV infection :

A thorough understanding of the pathophysiology of the disease helps in proper preoperative assessment and planning of the anaesthetic management. There may be multisystem organ involvement either due to opportunistic infection or due the drugs given to treat the HIV infection.

Cardiovascular system :

The common complications due to infection are as follows :

	Dilated cardiomyopathy.
	Pericardial effusion.
	Endocarditis and valvular besions.
	Acute coronary syndrome.
	Vasculitis.
	Pulmonary hypertension.

Respiratory system :

The following respiratory complications are seen

	Airway obstruction by Kaposi sarcoma or infections.
	Bronchitis.
	Sinusitis.
	Pneumonia.
	Atypical infections.

Gastrointestinal system :

	Difficulty or pain on swallowing.
	Increased gastric emptying time.
	Diarrhoea.
	Hepatobiliary involvement.
	Pancreasitis.

Renal system :

HIV associated nephropathy.

It necessitates the avoidance of nephrotoxic drugs and the need for adequate hydration to prevent further deterioration of renal function.

Neurological system :

HIV can affect all structures including the meninges, brain,spinalcord, peripheral nerve or muscle. There may be cognitive impairment, encephalopathy, autonomic neuropathy and seizures. Full neurological examination preoperatively with appropriate documentation is essential especially if regional anaesthesia is planned.

Heamatological system :

	Anaemia.
	Neutropenia.
	Thrombocytopenia.
	Persistent generalized lymphodenopathy.
	Haematological malignancies.
	Coagulation abnormalities.

Endocrine and metabolic system :

The drugs can cause the following side effects...

	Lipodystrophy.
	Disorders of H.P.A axis (Addison disease and cushing syndrome).
	Hyponatreamia due to S.I.A.D.H.
	Hypo or hyperthyroidism.
	Lactic acidosis.

Drug and anaesthetic importance :

HIV infected patient may be on drugs which include antiretero virals, anti tuberculous drugs, pentamidine and steroids. The following are some of the anti veterovirals with their common side effects.

Drugs	Side effects
Nucleoside analogues
1 . Zidovidine	Marrow supression,myopathy,Inhibits cytochrome p450.
2 . Lamividine.	Well tolerated. Diarhoea, headache.Peripheral neuropathy.
3 . Stavudine	Peripheral neuropathy.
4 . Tenofovir	Renal toxicity.
5 . Didanosine	Diarhoea, peripheral neuropathy.
Protease inhibitors
1 . Indinavir	Nephrolithiasis, Inhibits cytochrome p450.
2 . Saquinavir	Diarhoea,headache, Inhibits cytochrome p450.
3 . Ritonavir	Inhibits cytochrome p450, elevated triglycerides.
4 . Atazanavir	Diarhoea,jaundice.
Nonnucleosides
1 . Efavirenz	Dizziness,teratogenicity.
2 . Nevirapine	Rash, induces cytochrome p450.
Fusion inhibitors
1 . Enfuvirtide	Injection site reactions, headache ,bacterial pneumonia.
2 . Pentamidine	Bronchospasm, arrhythmias, electrolyte imbalance.
3 . Anti TB drugs	Hepatic renal dysfunction, thrombocytopenia.

Anaesthetic considerations :

Patients with HIV infection can report for HIV related problems (lymph node biopsy, drainage of abssess etc) or unrelated problems like trauma which has become very common now.

A through pre operative checkup should include...

	Careful history – to know about the presence of any serious system involvement.
	Investigations: apart from the routine investigation, special attention to be given to rule out haematological involvement.
	CD4 count (count> 500 is better): infective complications in the postoperative period is more if the count is less than 200/mm3.

General considerations in selecting the type of anesthesia :

	No surgery should be deferred on the basis of HIV positivity alone.
	ASA risk class is more important than HIV status.
	General anaesthesia is acceptable but drug interactions and multi system involvement caused by HIV should be considered.
	Regional anaesthesia is safe but the presence of local infections, coagulapathy and neuropathy should be ruled out.
	Anaesthesia and surgery decrease cell mediated immunity and the effects are more pronounced after general than regional anaesthesia.

Drug interactions :

	Anti reteroviral drugs affect cytochrome p450, so drugs which don’t depend upon this enzyme have to be used. Drugs like etomidate,atracurium,remifentanyl and desflurane are independent of metabolism by cytochrome p450.
	Midazolam and fentanyl are affected by cytochrome and are better avoided.
	Succingl cholrine should be used with caution in renal dysfunction and in the presence of myopathy.
	Cytomegalovirus adrenalitis may need steroid supplementation
	HIV associated anaemia, tachycardia, fever and hypoprotemia may necessitate more rationale use of anaesthetics.
	Oropharyngeal and oesophageal pathology may make the intubation difficult.
	Lung pathology may necessitate elective postop ventilation and a high intraoperative F1O2.
	Usage of filters to protect the anaesthetic circuit is necessary to protect from cross infection.
	HIV per se does not increase post operative complications.

HIV and Obstetrics :

The risk of transmission from the HIV infected mother to child is around 25% zidovidine mono therapy has reduced the incidence to 8% and a combination of ART and elective caesarean section has reduced the transmission to 2%. There is little evidence to suggest that HIV increases complications of pregnancy or pregnancy alter the clinical profile of HIV infections. Spinal anaesthesia is a safe choice of anaesthesia for caesarean sections taking the universal precautions.

Risk of Cross infection :

Transmission from patient to Anaesthetist :

HIV can be transmitted from the infected patient to the anaesthetist as a result of exposure to infected body fluids. This can occur either through a sharp injury or splashing of a mucoal membrane or broken skin with the patient’s body fluid especially saliva or oral secretions.

Most contaminated percutaneous injuries occur during recapping of needles or when contaminated sharps are not discarded safely.

Poor infection control practice in anesthetists puts them in risk. In a survey, anaesthetists wore gloves for 8%(peripheral vein cannulation) to 90% (central vein cannulation) of procedures performed. A needle stick injury through one pair of gloves has been associated with a 10-100 fold reduction in the inoculums. There is an additional benefit if a second pair of glove is worn. Constant vigilance and the use of universal precautions when caring for all patients are required by the anaesthetist in the operating theatre in order to avoid contracting infection from patients.

Patient to patient transmission :

Contamination of anaesthetic equipment is a potential route of HIV transmission. Airway devices like ETT should not be reused. The anaesthetic circuits are the potential sources for cross contamination. Heat and moisture exchange filters effectively filter bacteria and viruses thereby minimizing the risk of contamination of respiratory equipment.

Post exposure prophylaxis :

Following an accident with high risk body fluid, such as a needle stick injury, post exposure prophylaxis is recommended .This should commence as soon as possible after the injury, ideally within 1-2 hours, but can be considered upto 1-2 weeks after the injury. A recommended regimen is zidovudine 250mg bd, lamivudine 150mg bd plus indinarir 800mg tds for duration of 4 weeks. The high rate of toxicity and non compliance may necessitate other regiment.

Universal precautions :

Universal precautions as defined by CDC64 (Centers for disease control and prevention) are a set of precautions designed to prevent transmission of HIV to health workers while providing health care. They apply to blood, body fluids containing blood, semen, vaginal secretions, tissues, CSF, pleural, peritoneal, pericardial and amniotic fluids.

They do not apply to faeces, sputum, sweat, tears, urine and vomitus unless they contain blood.

1. Washing Hands - One of the most important requirements and the one that is most commonly ignored is washing hands, before and after seeing a patient. Strict adherence to washing hands with ordinary soap clearly reduces the risk of transmission of HIV and many other infectious agents.

2. Wearing Gloves - A pair of disposable plastic gloves have to be worn whenever the potential for a contact with the patient’s body fluid exists. At surgery, where there is a risk of injury from sharp objects, double gloving with good quality latex gloves is recommended. Fortified gloves that reduce chances of injury from sharps are not universally available and are also expensive.

3. Eye Glasses/Cap/Mask - The eyes are to be protected from split secretions by wearing goggles; the conventional glasses worn for correction of eyesight defects are open in the sides; but nevertheless give acceptable protection. The cap and mask protect the head and face from being exposed to spillage.

4. Foot Wear - The feet are notorious for little cuts and abrasions that may be contaminated by body fluids. Gumboot types of footwear are to be worn to avoid this.

5. Impervious Gown - While disposable impervious gowns are available, the cost may not be justifiable. In our conditions, use of a plastic apron under the conventional operating gown will serve the purpose.

6. Needles and Sharps - Manipulation of needles like bending and re-sheathing should be avoided. The used needles are to be deposited in thick walled puncture resistant containers for later incineration. Thick cardboard boxes discarded in the pharmacy can be for this purpose. A small square hole is made in the top for deposition of the needles. It is sent for incineration when two thirds full.

7. Surgical technique - Risk from needle prick injuries are greatest when working in depths like pelvis, the diaphragmatic hiatus or the chest. The use of the hand to direct the passage of needles is to be avoided.

While blunt needles have been shown to drastically reduce injuries, they are expensive and are not universally available.

8. Soiled linen - Soaking soiled linen for 30 minutes in 1:100 bleach solution (hypochlorite solution) kills the HIV virus completely. These can then be processed normally with washing and autoclaving as usual.

9. Metal Instruments - Metal instruments are washed with soap and water. They are then soaked in 2% Glutaraldehyde solution for 30 minutes to kill the virus. The sharp instruments are transferred to another container with fresh glutaraldehyde and soaked for a further six hours. The other instruments are autoclaved.

10. Plastic tubings - The anaesthetic tubings, tubings used for suction and those used in rotary pumps are all soaked in 2% Glutaraldehyde for six hours after cleaning with soap and water. Where available, these can also be subjected to ethylene oxide sterilization. Unfortunately a lot of hype is created, particularly in the lay press, regarding the conduct of surgical procedures on AIDS patients. Special scheduling during weekends, summary disposal of ‘’costly’’ instruments and linen are all quoted as safety measures. A pragmatic view of the situation should convince us that operating on an AIDS patient is practically no different from operating on any other patient, if universal precautions are universally followed. Routine preoperative testing may be misleading because of the window period and adherence to universal precautions is a must. One of the important defects with universal precautions is that it is not foolproof against needle injuries.

There are some new engineering devices which decrease needle stick injuries...

	Retractable lancets used for blood sampling by heel stabs and finger sampling.
	Retractable needles used for injections and immunizations.
	Shields added to needles for injections and venepuncture which are activated by the operator at the end of the procedure.
	Protected disposable scalpels with a shield that can be activated before passing the instrument between staff and before disposal.
	Blunt suture needles and...
	Intravenous cannula with blunting or guarding of the needle of the introducer that is activated when removed from the plastic cannula.

Conclusion :

Anaesthetists are primary care physicians in trauma care come across lot of screened and un-screened patients in their day today practice. Rigorous infection control practice is imperative to protect their patients and themselves. For that current knowledge about the HIV and its drug therapy is essential for optimal conduction of anaesthesia and surgery.

References :

1. The implications of HIV for the anaesthetist and the intensivist- Review article by M.S.Avidan,N.Jones and A.L.Pozniak in anaesthesia,2000. 55-344-354

2. HIV and anaesthesia- Dr.S.Parthasarathy and Dr.M.Ravishankar- Indian Journal of Anaesthesia-2007, 57(2):91-99

3. HIV and anaesthesia- Update in Anaesthesia- by Samantha Wilson.

Further reading :

1. HIV AND THE OBSTETRIC PATIENT: ANESETHETIC CONSIDERATIONS,

The Internet Journal of Anesthesiology, Volume 24, Number 1.

2. Anaesthesia and critical care for patients with HIV infection.

Contin Educ Anaesth Crit Care Pain (October 2005) 5 (5): 153-156.

Postoperative Pain Management

European Society of Regional Anaesthesia and Pain Therapy

According to the International Association for the Study of Pain (IASP), pain is defined as "An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage." (IASP 1979)

The goals of effective and appropriate pain management are to:

	Improve quality of life for the patient
	Facilitate rapid recovery and return to full function
	Reduce morbidity
	Allow early discharge from hospital

Postoperative pain can be divided into acute pain and chronic pain:

	Acute pain is experienced immediately after surgery (up to 7 days)
	Pain which lasts more than 3 months after the injury is considered to be chronic pain

The type of pain may be somatic (arising from skin, muscle, bone), visceral (arising from organs within the chest and abdomen), or neuropathic (caused by damage or dysfunction in the nervous system). Patients often experience more than one type of pain.

Choice of assessment tool

A preoperative discussion with the patient and relatives can include the following:

	Discuss the patient's previous experiences with pain and preferences for pain assessment and management.
	Give the patient information about pain management therapies that are available and the rationale underlying their use.
	Develop with the patient a plan for pain assessment and management. Select a pain assessment tool, and teach the patient to use it. Determine the level of pain above which adjustment of analgesia or other interventions will be considered.
	Provide the patient with education and information about pain control.

Treatment options

Effective treatment of postoperative pain includes a number of factors, including good nursing, non-pharmacological techniques, such as distraction, and balanced (multimodal) analgesia to provide adequate pain relief with optimal drug combinations used at the lowest effective doses.

Treatment options in relation to magnitude of postoperative pain expected following different types of surgery:

Pharmacological options of pain management:

Non-opioid analgesics	Paracetamol, NSAIDs, including COX-2 inhibitors, Gabapentin, pregabalin
Weak opioids	Codeine Tramadol Paracetamol combined with codeine or tramadol
Strong opioids	Morphine Diamorphine Pethidine Piritramide Oxycodone
Adjuvants	Ketamine Clonidine

Morphine and weak opioids :

Administration	(i) Intravenous. (ii) Subcutaneous by continuous infusion or intermittent boluses via indwelling cannula. (iii) Intramuscular (not recommended due to incidence of pain. 5-10 mg 3-4 hourly).
Dosage : IV PCA Subcutaneous	Bolus: 1-2 mg, lockout: 5-15 min (usually 7-8 min), no background infusion. 0.1-0.15 mg/kg 4-6 hourly, adapted in relation to pain score, sedation and respiratory rate.
Monitoring	Pain score, sedation, respiratory rate, side effects.
Comments	Side effects such as nausea, vomiting, sedation and apnoea. No other opioid or sedative drug should be administered.

Codeine

Administration	Oral
Dosage	3 mg/kg/day combined with paracetamol. A minimum of 30 mg codeine/tablet is required.
Monitoring	Pain score, sedation, side effects.
Comments	Analgesic action is likely to be due to conversion to morphine. A small number of patients derive no benefit due to absence of the converting enzyme.

Tramadol:

Administration	(i) Intravenous: inject slowly (risk of high incidence of NV). (ii) Intramuscular. (iii) Oral administration as soon as possible.
Dosage	50-100 mg 6 hourly.
Monitoring	Pain score, sedation, respiratory rate, side effects.
Comments	Tramadol reduces serotonin and norepinephrine reuptake and is a weak opioid agonist. In analgesic efficiency, 100 mg tramadol is equivalent to 5-15 mg morphine. Sedative drugs can have an additive effect.

Paracetamol:

Administration	(i) Intravenous: Start 30 min before the end of surgery. (ii) Oral administration as soon as possible. Duration: as long as required.
Dosage	4 x 1 g paracetamol/day (2 g propacetamol/day). Dose to be reduced (e.g. 3 x 1 g/day) in case of hepatic insufficiency.
Monitoring	Pain scores.
Comments	Should be combined with NSAID and/or opioids or loco-regional analgesia for moderate to severe pain.

Combination of codeine + paracetamol:

Administration	Oral.
Dosage	Paracetamol 500 mg + codeine 30 mg. 4 x 1 g paracetamol/day.
Monitoring	Pain score, sedation, side effects.
Comments	Analgesic action is likely to be due to conversion to morphine. A small number of patients derive no benefit due to absence of the converting enzyme.

NSAIDs:

Administration	(i) Intravenous: administration should start at least 30-60 min before end of surgery. (ii) Oral administration should start as soon as possible. Duration: 3-5 days.
Dosage	(i) Conventional NSAIDs include: ketorolac: 3 x 30-40 mg/day (only IV form) diclofenac: 2 x 75 mg/day ketoprofen: 4 x 50 mg/day (ii) Selective NSAIDs include: meloxicam 15 mg once daily COX-2 inhibitors are now licensed for postoperative pain management. They are as efficient as ketorolac but reduce GI side effects. Examples include: parecoxib: 40 mg followed by 1-2 x 40 mg/day (IV form) or celecoxib: 200 mg/day. However, there is some debate due to cardiovascular risks in patients with arteriosclerosis.
Monitoring	Pain scores. Renal function in patients with renal or cardiac disease, elderly patients, or patients with episodes of severe hypotension. Gastrointestinal side effects. Non-selective NSAIDs would be combined with proton inhibitors (i.e. omeprasol) in patients at risk of gastrointestinal side effects.
Comments	Can be added to the pre-medication. Can be used in association with paracetamol and/or opioids or local regional analgesia for moderate to severe pain.

Regional analgesia:

Continuous Central Neuraxis Blockade (CCNB)
CCNB remains the first choice for a number of indications, such as abdominal, thoracic, and major orthopaedic surgery, where adequate pain relief cannot be achieved with other analgesia techniques alone.

	Continuous Infusion (CI): An easy technique that requires little intervention. The cumulative dose of local anaesthetic is likely to be higher and side effects are more likely than with the other two techniques.
	Intermittent Top-up: Results in benefits due to frequent patient/staff contact but can produce a high staff workload and patients may have to wait for treatment.
	Patient-Controlled Epidural Analgesia (PCEA): This technique produces high patient satisfaction and reduced dose requirements compared with CI. However, sophisticated pumps are required and accurate catheter position is important for optimal efficacy.

Examples of local anaesthetics and opioids and doses in epidural analgesia

Local anaesthetics/opioids	Ropivacaine Sufentanil 0.5-1 μg/ml 0.2% (2 mg/ml) or Levobupivacaine or Bupivacaine 0.1-0.2% (1-2 mg/ml)	Sufentanil 0.5-1 μg/ml or Fentanyl 2-4 μg/ml
Dosage for continuous infusion (thoracic or lumbar level)	6-12 ml/h
Dosage for patient controlled infusion (lumbar or thoracic)	Background: 4-6 ml/h Bolus dose:2 ml (2-4 ml) Minimum lockout interval 10 min (10-30 min) Recommended maximum hourly dose (bolus + background): 12 ml

Continuous Peripheral Nerve Blockade (CPNB)

After major orthopaedic lower limb surgery, clinical studies show peripheral nerve blocks are as effective as epidural and that both are better than IV opioids.

Examples of local anaesthetics and doses in continuous peripheral nerve analgesia:

Site of catheter	Local anaesthetics and dosage
	Ropivacaine 0.2% Bupivacaine 0.1-0.125% Levobupivacaine 0.1-0.2%
Interscalene	5-9 ml/h
Infraclavicular	5-9 ml/h
Axillary	5-10 ml/h
Femoral	7-10 ml/h
Popliteal	3-7 ml/h

Patient Controlled Regional Analgesia (PCRA) can be used to maintain peripheral nerve block. A low basal infusion rate (e.g. 3-5 ml/h) associated with small PCA boluses (e.g. 2.5-5 ml - lockout: 30-60 min) is the preferred technique.

Infiltration blocks
Pain relief may be achieved by infiltration of the wound with local anaesthetic. The technique is easy to perform by the surgeon at the time of surgery.

Local anaesthetic infiltration

Local anaesthetic

Volume

Additives

Intra-articular instillation

Knee arthroscopy

	0.75% Ropivacaine
	0.75% Ropivacaine

	20 ml
	20 ml

	Morphine 1-2 mg
	Morphine 1-2 mg

Shoulder arthroscopy

0.75% Ropivacaine

10-20 ml

Intra-peritoneal instillation

Cholecystectomy

0.25% Ropivacaine

40-60 ml

Gynaecological

0.75% Ropivacaine

20 ml

Wound infiltration

Inguinal hernia

	0.25-0.5% Ropivacaine
	0.25-0.5% Levobupivacaine
	0.25-0.5% Bupivacaine

	30-40 ml
	30-40 ml
	Up to 30 ml

Thyroid surgery

	0.25-0.5% Ropivacaine
	0.25-0.5% Levobupivacaine
	0.25-0.5% Bupivacaine

	10-20 ml
	10-20 ml
	Up to 20 ml

Perianal surgery

	0.25-0.5% Ropivacaine
	0.25-0.5% Levobupivacaine
	0.25-0.5% Bupivacaine

	30-40 ml
	30-40 ml
	Up to 30 ml

Paediatric analgesia

Assessment of pain in children :

Many scales are available and the scale chosen should be appropriate for the child's age :

	A VAS or face scale can be used from 5- 6 years of age.
	For younger children, behaviour scales and/or physiological stress parameters are used (Children and Infants Postoperative Pain Scale - CHIPPS).

Children and Infants Postoperative Pain Scale (CHIPPS)

Described in 2000, the scale uses a measurement of five items, each rated as 0, 1, or 2 based on the following parameters:

Item	Score 0	Score 1	Score 2
Crying	None	Moaning	Screaming
Facial expression	Relaxed smiling	Wry mouth	Grimacing
Posture of the trunk	Neutral	Variable	Rear up
Posture of the legs	Neutral	Kicking	Tightened
Motor restlessness	None	Moderate	Restless

Total score indicates how the baby should be managed according to the scale :

	0 - 3 No requirement for treating pain.
	4 - 10 Progressively greater need for analgesia.

Doses of analgesic agents in children

NSAIDs and Paracetamol :

Drug	Dose
Diclofenac	Oral, rectal	1 mg/kg/8h
Ibuprofen	Oral	10 mg/kg/8h
Ketorolac	0.5 mg/kg/8h or continuous infusion
Paracetamol	Rectal	40 mg/kg; followed by 30 mg/kg/8h
	Oral	20 mg/kg; followed by 30 mg/kg/8h
	Newborn, rectal	20 mg/kg and 30 mg/kg/12h
	Newborn, oral	30 mg/kg and 20 mg/kg/8h

Opioids :

Drug	Dose
Morphine	Newborn	0.02 mg/kg/8h
	Newborn (for continuous infusion)	5-15 μg/kg/h
	Children	0.05-0.1 mg/kg/6h
	Children (for continuous infusion)	0-30 μg/kg/h
Fentanyl	According to surgery	2-10 μg/kg
	In ICU	2-5 μg/kg/h
	Oral transmucosal fentanyl citrate lollipop	15-20 μg/kg
Remifentanil	Surgery	0.5-1 μg/kg/min
	ICU	0.1-0.05 μg/kg/min
Codeine	Mainly used in combination with paracetamol (suppositories or syrup)	0.5-1 mg/kg/4h

Examples of local anaesthetics and mean doses for single shot epidural

Local anaesthetic	Caudal block	Lumbar block	Thoracic block
Bupivacaine	0.25%	2.5 mg/kg	2 mg/kg
Levobupivacaine0.2-0.25%	2-2.5 mg/kg	1.4-2 mg/kg	0.8-1 mg/kg
Ropivacaine 0.2%	2 mg/kg	1.4 mg/kg	0.8-1 mg/kg

Examples of local anaesthetics and mean doses for continuous infusion via epidural catheter

Local anaesthetic	Newborns and infants (up to 1 year)	Older children (> 1 year)
Bupivacaine 0.125% Levobupivacaine 0.1% Ropivacaine 0.1%	0.2 mg/kg/h	0.3-0.4 mg/kg/h

Adjuvant drugs for epidural use

Drug	Dose
Morphine	0.02-0.05 mg/kg
Fentanyl	1-2 μg/kg or 0.5-1 μg/kg/h
Sufentanil	0.2-0.3 μg/kg
Clonidine	1-2 μg/kg single shot or 3 μg/kg/24h in epidural infusion
Ketamine	0.5 mg/kg

Examples of local anaesthetics and mean doses for continuous peripheral nerve block in children

Local anaesthetic/adjuvant	Newborns and infants (up to 1 year)	Older children (> 1 year)
Ropivacaine 0.2% or Levobupivacaine 0.25%	0.2 mg/kg/h	0.4 mg/kg/h
Clonidine can be added as adjuvant	3 μg/kg/h

Ref:

Postoperative Pain Management – Good Clinical Practice, Produced in consultation with the European Society of Regional Anaesthesia and Pain Therapy.

Safe Extubation

Dr.K.Sudarshan
Consultant Anaesthesiologist
ORTHO ONE hospital, Coimbatore

Tracheal extubation is a critical step during emergence from general anaesthesia. It is not simply a reversal of the process of intubation because conditions are often less favourable than at the start of anaesthesia. At extubation, there is a transition from a controlled to an uncontrolled situation. Anatomical and physiological changes, compounded by time pressures and other constraints, contribute to a situation that can be more challenging for the anaesthetist than tracheal intubation. Although the majority of problems following extubation are of a minor nature, a small but significant number have serious consequences, including hypoxic brain injury and death.

All anaesthetists will at some point experience difficulty with or after tracheal extubation. Whilst tracheal intubation has been extensively studied, including the prediction, mechanism and incidence of difficult tracheal intubation coupled with established guidelines, tracheal extubation has received little attention. Despite tracheal extubation being recognised as a situation that can be potentially life threatening, there is little literature and guidelines are based on limited scientific evidence and mainly expert opinion.

Data from the UK suggest that respiratory complications are common at extubation and during recovery In the fourth National Audit Project (NAP4) of the Royal College of Anaesthetists and the DAS, major airway complications occurred during emergence or in recovery in approximately one third of the reported cases relating to anaesthesia. Closed-claims data from the US have demonstrated morbidity and mortality associated with extubation . Following the publication of the ASA guidelines for management of the difficult airway, there was a statistically significant reduction in airway claims arising from injury at induction of anaesthesia. However, claims arising from injury intra-operatively, at extubation and during recovery did not change. Death or brain injury was more common in claims associated with extubation and recovery than those occurring at the time of induction of anaesthesia

Problems at extubation: why is extubation hazardous?

Exaggerated laryngeal reflexes

Breath holding, coughing and bucking (a forceful and protracted cough that mimics a Valsalva anoeuvre) are physiological responses to airway stimulation and are associated with increases in arterial blood pressure, venous pressure and heart rate.

Laryngospasm

It is a protective exaggeration of the normal glottic closure reflex, and is produced by stimulation of the superior laryngeal nerve. Laryngospasm is often triggered by the presence of blood, secretions or urgical debris, particularly in a light plane of anaesthesia. Nasal, buccal, pharyngeal or laryngeal irritation, upper abdominal stimulation or manipulation and smell have all been implicated in the aetiology of laryngospasm. Clinical experience suggests that intravenous anaesthesia using a propofol-based technique is associated with a lower incidence of complications related to exaggerated airway reflexes, and there is some evidence to support this.

Typically, laryngospasm causes signs of upper airway obstruction (including stridor) that can precede complete airway obstruction and requires an immediate response (Appendix 1A). If not relieved promptly, laryngospasm may result in post-obstructive pulmonary oedema (also known as negative pressure pulmonary oedema) and hypoxic cardiac arrest. The equivalent response in the lower airway is bronchospasm.

Reduced airway reflexes

Many factors can contribute to a reduction in pharyngeal tone, causing collapse and airway obstruction. Residual neuromuscular blockade has been shown to increase the incidence of postoperative respiratory complications. Train-of-four ratios of 0.7–0.9 are associated with impaired pharyngeal function, airway obstruction, and increased risk of aspiration and attenuation of the hypoxic ventilatory response. Reduced laryngotracheal reflexes increase the risk of aspiration and airway soiling. Partial or complete airway obstruction with forceful inspiratory effort generates a significant negative intrathoracic pressure, which opens the oesophagus increasing the risk of regurgitation. The presence of blood in the airway is significant if airway reflexes are obtunded, because the aspiration of blood clots can cause complete airway obstruction.

Depletion of oxygen stores at extubation

Following extubation, the aim is to provide an uninterrupted supply of oxygen to the patient’s lungs. Various factors that contribute to rapid depletion of oxygen stores and a reduction in arterial oxygen Saturation.

Pathophysiological Causes

	Reduced functional residual capacity Hypoventilation		Cardiovascular instability
	Diffusion hypoxia		Neurological dysfunction
	Atelectasis		Metabolic derangement
	Ventilation ⁄ perfusion mismatch		Electrolyte disturbances
	Problems related to airway reflexes Shivering		Airway injury

Pharmacological Causes

	Neuromuscular blocking drugs Opioids
	Residual anaesthetic agents

Human & other factors

	Inadequate equipment		Interruption of oxygen supply during
	Inadequate skilled assistance		patient transfer
	Access to airway e.g. dressings ⁄ gastric tubes ⁄ rigid fixators		Communication difficulties (e.g. language, mental capacity)
	Patient position		Removal of oxygen by agitated or uncooperative patient

Airway injury

Injury to the airway may be the result of direct trauma following surgical or anaesthetic intervention, or it may be indirect due to subsequent bleeding, swelling or oedema. Any surgery or insult in or around the airway can cause problems following extubation. Thyroid surgery, laryngoscopy, panendoscopy, and maxillofacial, cervical spine, carotid and other head ⁄ neck procedures can cause direct airway compromise due to haematoma, oedema, altered lymphatic drainage, vocal cord paralysis and tracheomalacia [54, 55]. Patient position (prone or prolonged Trendelenburg positions), duration of surgery, fluid overload and anaphylaxis may contribute to airway oedema.

Anaesthetic airway injury may result from laryngoscopy, or insertion and presence of a tracheal tube or airway adjuncts. Periglottic trauma may result from transoesophageal echocardiography probes and nasogastric tubes, from the use of inappropriately large tube sizes and excessive cuff pressure or from incorrectly positioned tracheal tubes (e.g. with a cuff inflated within the larynx). Problems resulting from airway injury often do not become apparent until after tracheal extubation; direct problems include crico-arytenoid joint dysfunction and vocal cord palsy, and indirect problems may result from pressure effects secondary to haematoma, oedema or mediastinitis . The ASA closed-claims analysis of airway injury during anaesthesia showed that 33% of injuries occurred at the larynx, 19% at the pharynx, 18% at the oesophagus, 15% at the trachea, 10% at the temporo mandibular joint and 5% at the nose.

Human factors

The environment at extubation is not as favourable as at intubation. Equipment, monitoring and assistance may be inadequate. Patient factors contributing to extubation problems may be compounded by distraction, time pressure, operator fatigue, lack of equipment or skilled assistance and poor communication.

Managing extubation

There is a lack of compelling evidence to support a ‘one size fits all’ extubation strategy for every patient. There is, however, a general agreement that good preparation is key to successful airway management and that an extubation strategy should be in place for every patient.

General principles

Extubation is an elective process, and it is important to plan and execute it well. The goal is to ensure uninterrupted oxygen delivery to the patient’s lungs, avoid airway stimulation, and have a back-up plan, that would permit ventilation and re-intubation with minimum difficulty and delay should extubation fail. Since the introduction of the DAS unanticipated difficult intubation guidelines, the concept of a stepwise approach has been widely accepted. This approach has been used to aid decision making and safe management of extubation.

The Difficult Airway Society extubation guidelines describe the following four steps:

Step 1: Plan extubation.

Step 2: Prepare for extubation.

Step 3: Perform extubation.

Step 4: Post-extubation care: recovery and follow-up.

Step 1: Plan Extubation

An outline extubation plan should be in place before induction of anaesthesia and reviewed throughout and immediately before performing extubation. Planning involves an assessment of the airway and general risk factors. The following questions may aid in the decision making process , answers to which will help determine whether extubation is ‘low-risk’ or ‘at-risk’

	Are there airway risk factors? was the airwaynormal ⁄ uncomplicated at induction? has the airway changed?
	Are there general risk factors?

Low-risk extubation:

This is a routine or uncomplicated extubation. The airway was normal ⁄ uncomplicated at induction and remains unchanged at the end of surgery, and no general risk factors are present.

‘At-risk’ extubation:

	Pre-existing airway difficulties
	Peri-operative airway deterioration
	Restricted airway access

Other things to consider

Tracheal extubation: awake or anaesthetized?

When deciding when to extubate, two main considerations should be taken care:

	was there any previous difficulty in controlling the airway?;
	what is the risk of pulmonary aspiration?

As a general rule, patients should be extubated awake. The endpoint for wakefulness in these studies was taken as swallowing; the incidence of respiratory complications dramatically decreased when extubation was performed when eyes were open, with spontaneous ventilation.

Extubation under deep anaesthesia decreases cardiovascular stimulation and reduces the incidence of coughing and straining on the tube. However, the incidence of respiratory complications has been found to be greater after extubation under deep anaesthesia.

Patient position

Despite advances in anaesthesia, the reported incidence of pulmonary aspiration in the perioperative period has not decreased in the last three decades; it varies from 2.9 to 10.2 per 10 000 anaesthetics.4 Mortality rates of patients who have aspirated vary from 0 to 4.6%.4 The traditional practice of extubating in the left lateral, head-down position maintains airway patency by positioning the tongue away from the posterior pharyngeal wall and also protects the airway from aspiration. In children, extubation in the recovery position while still anaesthetized is still common practice.

Step 2 – Prepare for extubation

Preparation is aimed at the final optimisation of airway, general and logistical factors to ensure the best possible conditions for success extubation. Together with planning (step 1), preparation (step 2) enables the risk stratification of extubation into ‘low-risk’ and ‘atrisk’ categories, and should always precede extubation (step 3)

Final evaluation and optimisation of airway factors. The airway should be reassessed at the end of surgery and before extubation. This review should be used to finalise the extubation plan and to determine the most appropriate rescue plan for re-intubation should extubation fail.

Airway

It is essential to consider whether bag-mask ventilation would be achievable. Oedema, leeding, blood clots, trauma, foreign bodies and airway distortion can be assessed by direct or indirect laryngoscopy.

Larynx

A cuff-leak test may be used to assess subglottic calibre. Clinically, the presence of a large audible leak when the tracheal tube cuff is deflated is reassuring: the absence of a leak around an appropriately sized tube generally precludes safe extubation

Lower airway

It is important to consider factors in the lower airway that may contraindicate extubation, such as lower airway trauma, oedema, infection and secretions. Gastric distension splints the diaphragm and restricts breathing. Gastric decompression with an oro ⁄ nasogastric tube is advisable if high-pressure facemask ⁄ supraglottic airway ventilation has been necessary.

Final evaluation and optimisation of general factors.

Neuromuscular block should be fully reversed to maximise the likelihood of adequate ventilation, and restore protective airway reflexes and the ability to clear upper airway secretions. The use of a peripheral nerve stimulator to ensure a train-of-four ratio of 0.9 or above is recommended and has been shown to reduce the incidence of postoperative airway complications.

Extubation is an elective process, which should be carried out in a controlled manner with the same standards of monitoring, equipment and assistance that are available at induction. Tracheal extubation can take as long to perform safely as tracheal intubation, and this should be considered when organising list schedules, or sending for the next patient. Communication is essential, and the anaesthetist, surgeon and theatre team all play an important role.

Step 3: Perform extubation

Step 3 involves the actual performance of extubation Any extubation technique used should ensure minimum interruption in oxygen delivery to the patient’s lungs.

	Building oxygen stores (pre-oxygenation)
	Suction
	Alveolar recruitment manoeuvres
	Bite block:

Extubation Algorithm

Summary:

Guidelines are useful in infrequent, life-threatening situations, and have been shown to improve outcomes. Several national guidelines for management of the airway have been published, but none has addressed extubation in detail. Extubation differs from intubation, in that it should always be an elective process with adequate time available to the anaesthetist for methodical management.

Extubation practice is highly variable, and is not often formally addressed in training. Technical and nontechnical factors can contribute to adverse events at extubation but outcomes are improved by planning, organisation and communication.

The DAS extubation guidelines promote the concept of an extubation strategy, involving a stepwise approach to planning, preparation and risk stratification, aimed at clear identification and management of patients ‘at risk’ during extubation.

The evidence base for extubation practice is limited, so inevitably some of the recommendations in these guidelines are based on expert opinion.

Awake extubation is the preferred technique for most patients. However, deep extubation, laryngeal mask exchange, remifentanil infusion and the use of airway exchange catheters may be beneficial in certain clinical situations.

Delaying extubation or performing an elective tracheostomy should be considered when it is unsafe to extubate.

ISA KANYAKUMARI

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