The number of thrombocytopenic parturients in the literature who received neuraxial techniques without complication has been significantly increased.

Dr Joost van Veen et al[3] after analysing 17 national and international guidelines from blood transfusion and anaesthetic societies suggested that 80 × 109/l is a safe count for placing/removing an epidural or spinal anaesthetic and 40 × 109/l is a safe count for LP for general population. This, however, is provided that:

1 The platelet count is stable.

2 There is no other acquired or congenital coagulopathy.

3 The platelet function is normal and the patient is not on an antiplatelet drug.

4 The patient is not on an anticoagulant. If the patient is on a low molecular weight heparin, 12 h should have elapsed from the last dose of a prophylactic dose or 24 h after a therapeutic dose before an epidural or spinal anaesthetic is placed.

It is possible that lower platelet counts may also be safe but there is insufficient published evidence to make recommendations for lower levels at this stage. For patients with platelet counts of 50–80 × 109/l requiring epidural or spinal anaesthesia and patients with a platelet count 20–40 × 109/l requiring a LP, an individual decision based on risks and benefits should be made.

1.  Estcourt LJ, Ingram C, Doree C, Trivella M, Stanworth SJ. Use of platelet transfusions prior to lumbar punctures or epidural anaesthesia for the prevention of complications in people with thrombocytopenia. Cochrane Database of Systematic Reviews 2016, Issue 5. Art. No.: CD011980. DOI: 10.1002/14651858.CD011980.pub2.

2. Risk of Epidural Hematoma after Neuraxial Techniques in Thrombocytopenic Parturients: A Report from the Multicenter Perioperative Outcomes Group. Anesthesiology 6 2017, Vol.126, 1053-1063.

3. Van Veen, J. J., Nokes, T. J. and Makris, M. (2010), The risk of spinal haematoma following neuraxial anaesthesia or lumbar puncture in thrombocytopenic individuals. British Journal of Haematology, 148: 15–25. doi:10.1111/j.1365-2141.2009.07899.x

Most of the dreaded events related to thyroid surgery are manifested in the post-op period, which include, but are not limited to Hemorrhage, Laryngeal edema, RLN damage, Superior laryngeal nerve damage and Tracheomalacia.

The American Society of Anesthesiologists practice guidelines for management of the difficult airway recommend that, in addition to planning for intubation, the anesthesiologist should have a preformulated strategy for extubation of such patients.

Laura Cavallone, M.D., has designed the “Extubation Algorithm” major neck and upper airway surgery. In herrecent review article, she tried to summarize some of the practical recommendations; however, the evidence behind different extubation strategies and techniques remains sparse.

Ten Golden Rules of Extubation after Thyroidectomy:

2. Use of steroids in major neck upper airway surgery Controversial and scarce data from specific literature:                                                                                                            

Data from studies in ICU setting suggest that steroids administration prior to extubation decreases the odds ratio for laryngeal edema and subsequent need for reintubation;

Dexamethasone 8 mg pre-operatively improves post-op nausea, vomiting, pain, subjective vocal function after thyroidectomy

Cons = lack/decrease of protective airway reflexes may lead to increased risk for aspiration and airway obstruction;

Caveats=easy intubation and mask ventilation are important prerequisites; increased risk of laryngospasm if performed during transition between deep anesthetized state and awake state

Cons = active protective airway reflexes may lead to increased risk of re-bleeding at the site of surgery (increased venous pressure and straining on wound).

Caveats= if pt. awake but NOT calm and cooperative, safe extubation procedures (e.g. flexible laryngoscopy, positioning of tube exchanger) may be extremely difficult

Impaired access for suction

Impaired possibility to monitor site of surgery

Fit of mask may be changed after surgery (edema)

Increased risks of post-op upper airway aspiration

6. Cuff leak test: validated methods                                                     

Measurements of expiratory tidal volumes after 4 complete respiratory cycles with the ETT cuff deflated;

Measurements of expiratory tidal volumes with cuff deflated ONLY at the end of the end-  inspiratory pause

Proposed cut-off values:

10-12% of the TV that was measured before cuff deflation (average-adult population);

 110-130 ml (average – adult population)

In the context of upper airway and neck surgery, where factors modifying airway anatomy and physiology and affecting post-extubation airway patency may have intervened intraopeartively, a thorough airway exam prior to extubation is advised. 

9. Risk of vocal cord paralysis after major neck and upper airway surgery

Reported rates of RLN injury vary greatly in literature; rate reported also depends on the method of examining the larynx (e.g. temporary palsy: 1.4% to 38%)   

 • Uncertain role of nerve monitoring during thyroid, PPV 40% and NPV 100%

 Thyroid surgery remains the most common cause of bilateral vocal fold immobility; non-thyroid surgeries (other neck, intracranial and intra-thoracic procedures) are the main cause of iatrogenic monolateral vocal cord paralysis

Monolateral paralysis more than 50% of times is asymptomatic; bilateral presents with stridor/airway obstruction.

10. Flexible laryngoscopy for post-extubation airway exam

Recommend as “the gold standard method to examine the larynx after thyroidectomy”

1 Call for help.

4 Low-dose propofol e.g. 0.25 mg.kg−1 intravenously may help

5 Propofol (1–2 mg.kg−1 intravenously) Whilst low doses of propofol may be effective in early laryngospasm, larger doses are needed in severe laryngospasm or total cord closure

6 Suxamethonium 1 mg.kg−1 intravenously. Worsening hypoxia in the face of continuing severe laryngospasm with total cord closure unresponsive to propofol requires immediate treatment with intravenous suxamethonium succinylcholine. The rationale for 1 mg.kg−1 is to provide cord relaxation, permitting ventilation, re-oxygenation and intubation should it be necessary

8 Atropine may be required to treat bradycardia

9 In extremis, consider a surgical airway.

Management of post-obstructive pulmonary oedema:

The negative intrathoracic pressure created by forceful inspiratory efforts against an obstructed airway can lead to post-obstructive (non-cardiogenic) pulmonary oedema. The commonest cause is laryngospasm (> 50%), but post-obstructive pulmonary oedema. Post-obstructive pulmonary oedema occurs after 0.1% of all general anaesthetics. It is more common in young muscular adults (male:female ratio 4:1)

Negative intrathoracic pressure results in increased venous return (preload) to the right ventricle and increase in the pulmonary capillary blood volume. Hypoxic pulmonary vasoconstriction facilitates fluid shifts into the interstitium. Right ventricular afterload also increases as hypoxia, acidosis and negative intrathoracic pressure increase pulmonary vascular tone. This may result in a shift of the interventricular septum into the left ventricular outflow tract, increasing left ventricular diastolic dysfunction and promoting pulmonary oedema.

Management of post-obstructive pulmonary oedema:

1 Treat the cause: relieve the airway obstruction

2 Administer 100% O2 with full facial CPAP mask. In addition to relieving upper airway obstruction, CPAP may reduce oedema formation by increasing mean intrathoracic pressure and minimise alveolar collapse by increasing functional residual capacity, improving gas exchange and reducing the work of breathing

3 Nurse the patient sitting upright

4 If there is fulminant pulmonary oedema with critical hypoxaemia, tracheal intubation and mechanical ventilation with PEEP are necessary. Less severe hypoxia responds to supplemental oxygen and/or non-invasive ventilation, or CPAP [200]

5 Intravenous opioids may help reduce subjective dyspnoea

6 Chest radiography may exclude other complications of difficult airway management and causes of hypoxia (gastric aspiration, pre-existing infection, pneumothorax, barotrauma, pulmonary collapse)

7 Frank haemoptysis may necessitate direct laryngoscopy and/or flexible bronchoscopy

8 Diuretics are often administered, but their efficacy is unproven.

1. Extubation Algorithm for Major Neck and Upper Airway Surgery. Presented by Laura Cavallone, M.D., Washington University School of Medicine in St. Louis, Missouri. Society for Head and Neck Anesthesia.

2. Guidelines: Difficult Airway Society Guidelines for the management of tracheal extubation. Anaesthesia. Volume 67, Issue 3 March 2012 Pages 318–340.

Doctors at KK Women’s and Children’s Hospital (KKH), Singapore  have developed the world’s first fully-automated system to enhance the management of blood pressure in women undergoing caesarean section under spinal anaesthesia.

The novel Double Intravenous Vasopressor Automated (DIVA) System detects and responds rapidly to low blood pressure and/or slow heart rate in real-time by autoadministering a precise amount of the recommended medication to manage reduced blood pressure (vasopressor). The system uses an advanced decision algorithm to ensure enhanced patient safety.

Enhanced management of low blood pressure during c-section under spinal anaesthesia

Peri-operative hypotension during spinal anaesthesia for caesarean section is common owing to the loss of sympathetic tone and the physiological predisposition of pregnant women to hypotension. The consequences of maternal hypotension are potentially severe, affecting both the mother and child. Maternal effects include nausea, vomiting and headache attributable to inadequate organ perfusion; fetal adverse effects may include fetal acidosis and poor neurological outcomes because of a lack of placental vascular autoregulation, which renders its perfusion pressure-dependent. While several strategies, both pharmacological and nonpharmacological, have been used to treat hypotension, the optimal treatment is still debatable. Non-pharmaco-logical methods alone are often not effective; hence, the use of vasopressors is often required. Recent data support the use of alpha-1 adrenergic agonists such as phenylephrine, although ephedrine (a mixed alpha- and beta-adrenergic agonist) may be useful in the event of concomitant hypotension with bradycardia.
Optimal timing and dosing of vasopressors is dependent on accurate and timely blood pressure monitoring. Conventional non-invasive blood pressure monitoring occurs at 60 second intervals – which could result in a potential delay in detecting rapid blood pressure changes within these 60 seconds.

Setting a new standard in speed and accuracy, the DIVA System is an automated dual-pump system which innovatively integrates continuous non-invasive blood pressure monitoring to ensure closed-loop vasopressor administration during the surgery. It continuously measures and records blood pressure and heart rate every second, allowing the extremely rapid detection of blood pressure changes and episodes of low blood pressure. When low blood pressure and/or slow heart rate are detected, the DIVA System automatically and promptly administers the precise amount of the appropriate vasopressor required to restore optimal blood pressure – making the process much more efficient than manual administration.

Study: DIVA System clinically effective in management of blood pressure

B. L. Sng et al conducted a randomised, controlled, double-blinded trial involving 213 healthy women who underwent elective caesarean delivery under spinal anaesthesia using 11 mg hyperbaric bupivacaine with 15 lg fentanyl and 100 lg morphine. The automated vasopressor group had better systolic pressure control, with 37/106 (34.9%) having any beat-to-beat systolic pressure reading < 80% of baseline compared with 63/107 (58.9%) in the control group (p < 0.001). There was no difference in the incidence of reactive hypertension, defined as systolic pressure > 120% of baseline, with 8/106 (7.5%) in the automated vasopressor group vs 14/107 (13.1%) in the control group, or total dose of vasopressors. The automated vasopressor group had lower median absolute performance error of 8.5% vs control of 9.8% (p = 0.013), and reduced incidence of nausea (1/106 (0.9%) vs 11/107 (10.3%), p = 0.005).

Results showed that the DIVA System is clinically more effective in maintaining blood pressure during caesarean section under spinal anaesthesia, as it is able to detect and normalise blood pressure fluctuations more quickly and effectively than traditional physician administered techniques using conventional blood pressure monitoring.

How the DIVA System works

The DIVA System calculates the amount of vasopressor to administer using a customised algorithm based on integrated blood pressure data from a continuous non-invasive arterial blood pressure (CNAPTM) monitoring system. A closedloop feedback system controls vasopressor administration, ensuring that the patient receives only the precise dosage required (Figure 1).

1.Two alternating finger cuffs measure the patient’s arterial blood pressure and heart rate per second.

Benefits of the DIVA System

• Non-invasive, rapid and automatic detection and response to low blood pressure and slow heart rate

• Delivers individualised optimal vasopressor dosing regimen

• Maintains systolic blood pressure near baseline blood pressure

• Alleviates pre-delivery nausea and vomiting

Ref:

1. Sng BL, Wang H, Assam PN, Sia AT. Assessment of an updated double-vasopressor automated system using Nexfin for the maintenance of haemodynamic stability to improve peri-operative outcome during spinal anaesthesia for caesarean section. Anaesthesia. 2015 Jun;70(6):691-8.

2. Sing Health Medical News. https://www.singhealth.com.sg/Pages/home.aspx