NICE pre-operative guidelines: Summarise NICE guidelines on pre-operative investigations.
All types of surgery:
- Communication and testing in primary care
- Consideration of existing medicines
- Check pregnancy status
- Sickle cell disease - do not routinely offer testing before surgery
- HbA1c testing for those with diagnosed diabetes only
- Urine tests (microscopy & culture) only if the presence of UTI would influence the decision to operate
- CXR - not routinely
- Echocardiography & ECG - only if heart murmur + cardiac symptoms (breathlessness, pre-syncope, syncope or chest pain), or signs and symptoms of heart failure
ASA Grades
- ASA 1 - normal health patient
- ASA 2 - patient with mild systemic disease
- ASA 3 - patient with severe systemic disease
- ASA 4 - patient with severe systemic disease that is a constant threat to life
Minor Surgery
- FBC - not routine
- Haemostasis - not routine
- Kidney function - ASA 3/4 at risk of AKI
- ECG - ASA 3/4 if no results available from past 12 months
- Lung function / ABG - not routine
Intermediate surgery
- FBC - ASA 3/4 if CVD or renal disease not recently investigated
- Haemostasis - ASA 3 / 4 - chronic liver disease, if taking anticoagulants that need to be modified or if clotting status needs to be tested
- Kidney function - ASA 2 if risk of AKI, ASA 3/4 always
- ECG - ASA 2 if CVD, renal disease or diabetes and ASA 3/4 always
- Lung function / ABG - ASA 3/4 advice from senior anaesthetist if known or suspected respiratory disease
Major Complex Surgery
- FBC - yes
- Haemostasis - ASA 3/4 - chronic liver disease, if taking anticoagulants that need to be modified or if clotting status needs to be tested
- Kidney function - ASA 1 if risk of AKI, ASA 2/3/4 always
- ECG - ASA 1 consider for >65yrs with no ECG results from past 12 months, ASA 2/3/4 always
- Lung function / ABG - ASA 3/4 advice from senior anaesthetist if known or suspected respiratory disease
Peri-operative risk scoring systems: summarise common peri-operative risk scoring systems (ASA and POSSUM).
ASA Grades
- ASA 1 - normal health patient
- ASA 2 - patient with mild systemic disease
- ASA 3 - patient with severe systemic disease
- ASA 4 - patient with severe systemic disease that is a constant threat to life
POSSUM - score of 1,2,4,8
- Operative severity - minor, intermediate, major, major +
- Number of operations within 30 days - 1, __, 2, >2
- Blood loss per operation (ml) - <100, 101-500, 501-999, >1000
- Peritoneal contamination - none, serous fluid,local pus, free bowel content, pus or blood
- Presence of malignancy - none, primary only,nodal metastases, distant metastases
- Mode of surgery - elective, ___, emergency resus of 2h possible and operation <24h after admission, emergency (immediate surgery <2h needed)
Peri-operative disease management: explain the principles of perioperative management of medical co-morbidities, including diabetes mellitus, hypertension, ischaemic heart disease, asthma, COPD, patients on anti-coagulant medications and sickle cell disease.
Minor Surgery
- FBC - not routine
- Haemostasis - not routine
- Kidney function - ASA 3/4 at risk of AKI
- ECG - ASA 3/4 if no results available from past 12 months
- Lung function / ABG - not routine
Intermediate surgery
- FBC - ASA 3/4 if CVD or renal disease not recently investigated
- Haemostasis - ASA 3 / 4 - chronic liver disease, if taking anticoagulants that need to be modified or if clotting status needs to be tested
- Kidney function - ASA 2 if risk of AKI, ASA 3/4 always
- ECG - ASA 2 if CVD, renal disease or diabetes and ASA 3/4 always
- Lung function / ABG - ASA 3/4 advice from senior anaesthetist if known or suspected respiratory disease
Major Complex Surgery
- FBC - yes
- Haemostasis - ASA 3/4 - chronic liver disease, if taking anticoagulants that need to be modified or if clotting status needs to be tested
- Kidney function - ASA 1 if risk of AKI, ASA 2/3/4 always
- ECG - ASA 1 consider for >65yrs with no ECG results from past 12 months, ASA 2/3/4 always
- Lung function / ABG - ASA 3/4 advice from senior anaesthetist if known or suspected respiratory disease
Day Surgery: recall the criteria for the suitability of patients for day stay surgery.
- Minimal blood loss expected
- Short operating time (< 1 hour)
- No expected intra-operative or post-operative complications
- No requirement for specialist aftercare
Safety - Nil by mouth policy: explain the principles of nil by mouth policy before surgery.
Preoperative fasting is the practice of a patient abstaining from oral food and fluid intake for a time before an operation is performed. This is intended to prevent pulmonary aspiration of stomach contents during general anesthesia.
The amount of time you have to go without food or drink (fast) before you have your operation will depend on the type of operation you’re having. However, it is usually at least 6 hours for food, and 2 hours for fluids. You’ll be told how long you must not eat or drink for before your operation.
Safety - Transfusion reporting - recognize the importance of reporting blood units administered to the transfusion lab.
Ensuring that incidents are reported through the Trust Incident Reporting procedure, in line with the Incident Reporting and investigation Policy, and ensuring there is resultant organisational learning through the divisional structure and more widely across the trust.
Reporting of transfusion reactions or other incidents to the Blood Transfusion Laboratory.
Any unexpected event that has an actual or potential short-term or long-term detrimental effect on a patient must be reported according to the Trust’s Incident Reporting and Investigation Policy and to the Blood Transfusion laboratory.
Incident reporting should include ‘near miss’ episodes involving procedural errors which were detected in time to prevent a serious complication of blood transfusion, for example taking the blood sample for compatibility testing from the wrong patient or labeling the blood sample with another patient’s details.
Safety - controlled drugs: recognize the importance of recording the use of controlled drugs in the controlled drug register.
- The establishment and operation of procedures to ensure safe management and use of controlled drugs by the healthcare body
- Ensuring that an organization or person acting on behalf of (or providing services under arrangements made with) the healthcare body establishes and operates appropriate arrangements for securing the safe management and use of controlled drugs by that organization or person
- Ensuring that up-to-date standard operating procedures (SOPs) regarding the management and use of controlled drugs are in place for the healthcare body and any person or organization acting on their behalf or providing services for them (see Box 1).
https: //www.guidelinesinpractice.co.uk/your-practice/receipt-supply-and-storage-of-controlled-drugs-must-be-recorded/309024.article
Respiratory - Ventilation: compare the differences between spontaneous ventilation and positive pressure ventilation.
Spontaneous breathing - the movement of gas in and out of the lungs that is produced in response to an individual’s respiratory muscles.
Continuous spontaneous ventilation - any mode of mechanical ventilation where every breath is spontaneous (e.g. patient triggered and patient cycled)
Positive pressure ventilation - a form of respiratory therapy that involves the delivery of air or a mixture of oxygen combined with other gases by positive pressure into the lungs.
Delivered in 2 forms:
- Non-invasive positive pressure ventilation ( NIPPV) - e.g. face mask with tight seal
- Invasive positive pressure ventilation (IPPV) - e.g. endotracheal tube or tracheostomy
BiPAP - Bi-level Positive Airway Pressure
- 2 levels of pressure - inspiratory positive airway pressure (IPAP) and lower expiratory positive airway pressure (EPAP) for easier exhalation
CPAP - Continuous Positive Airway Pressure
- A constant level of pressure above atmospheric pressure is continuously applied to the upper airway
- Intended to prevent upper airway collapse or reduce the work fo breathing (e.g. heart failure)
APRV - Airway Pressure Release Ventilation
- Used for acute lung injury, ARDS and atelectasis after major surgery
- Inverse ratio ventilation - exhalation time is shortened to usually less than 1 second to maintain alveoli inflation
- Continuous pressure after a brief release - most efficient, conventional mode for lung-protective ventilation
Respiratory - Anaesthetic emergencies: recall the assessment and management of anaesthetic emergencies, including asthma, pneumothorax, haemothorax, anaphylaxis, foreign body aspiration.
ASTHMA
Assessment:
- Spirometry measurement of expiratory volume in 1s (FEV1) expressed as a percentage of predicted normal value
- Measurement of peak expiratory flow (PEF)
- Pulse oximetry (& ABG in those < 92% sats or FEV1 < 30% without response to treatment)
- Potassium levels (hypokalaemia caused by high-dose B-agonist therapy)
While recognizing the poor correlation between clinical signs and physiological measures, an FEV1 of <30% predicted is likely to be present in a patient who is unable to speak more than a few words with an arterial carbon dioxide tension (PaCO2) of >5.3 kPa (40 mm Hg), a quiet chest with the absence of audible wheezing, respiratory rate >30/min or pulsus paradoxus >20 mm Hg.
Management - OSHITME
O - OXYGEN - give via nasal cannula / mask to get O2 sats between 94-985
S - SALBUTAMOL - 2.5-5mg nebulised
H - HYDROCORTISONE - 100mg IV or PREDNISOLONE 40mg oral
I - IPRATROPIUM - 500mcg nebulised
T - THEOPHYLLINE - IV
M - MAGNESIUM SULPHATE - IV
E - ESCALATE CARE - if intubation and invasive ventilation are required
The administration of excessive oxygen is not without potential risks, including atelectasis and increased intrapulmonary shunting, and a reduction in cardiac output and coronary blood flow
NIPPV - useful for those with hypercapnic respiratory failure, as long as airway protection & can tolerate face mask. Will reduce work of breathing, respiratory muscle fatigue, decrease airway resistance, re-expand atelectatic areas of lung, decrease adverse hemodynamic effects of negative inspiratory pleural pressures - buying time for transfer to an ICU / HDU and for pharmacological intervention to take effect.
https://thorax.bmj.com/content/62/5/447
PNEUMOTHORAX & HAEMOTHORAX
Assessment
- Clinical assessment
- eFAST - extended focused assessment with sonography for trauma) or CXR if respiratory compromise
- Immediate CT for those without severe respiratory compromise who are responding to resuscitation or whose haemodynamic status is normal
- CXR or US as first-line for children under 16
- Do not routinely use CT for first line to assess chest trauma in children under 16
Management
- Perform decompression before imaging only if they have either haemodynamic instability of severe respiratory compromise
ANAPHYLAXIS
Pathway:
- Emergency treatment for a suspected anaphylactic reaction
- Take timed blood samples for mast cell tryptase testing as soon as possible after emergency treatment, within 1-2 hours from onset of symptoms
- Document acute clinical features - rapidly developing, life-threatening problems involving the airway (pharyngeal or laryngeal oedema) and/or breathing (bronchospasm wth tachypnoea) and/or circulation (hypotension, tachycardia) and associated skin and mucosal changes
- Observation for 6-12 hours
- Refer to specialist allergy service
- Offer appropriate adrenaline injector as interim measure before specialist allergy appointment & offer information/support to the patient
FOREIGN BODY INSPIRATION
Presentation:
- Sudden onset cough or persistent cough
- Pneumonia
- Atelectasis
- Wheezing - focal monophonic wheezing or decreased air entry
- Respiratory failure in severe cases
- Witnessed episode of choking
Management:
- Neck and CXR
- Expiratory CXR - allows visualisation fo air trapped by a valve-like effected due to partial obstruction of bronchial lumen, may see a mediastinal shift
- Life-threatening - 5 back blows or abdominal thrusts & chest compressions
- Bronchoscopy
Respiratory - Observations: recall the measurement and normal values of physiological parameters, including pulse oximetry, capnography and blood gas results.
Pulse Oximetry
- Normal 95-100%
- COPD 88-92%
- <90% abnormally low
Capnography
- End-tidal CO2 usually 35-45 mmHg
- Shows how much CO2 is present at each phase of the respiratory cycle, normally has a rectangular shape
- Measures and displays respiratory rate (12-20 breaths per minute)
Blood Gas Results
- pH - 7.35-7.45
- PaO2 - 75-100mHg
- PaCO2 - 35-45mmHg
- HCO3 - 22-26 meq/L
Circulation - Blood pressure monitoring: recall the indications for non-invasive and invasive monitoring.
Invasive:
- Induced, on-going or anticipated hypotension or wide variations in blood pressure
- End-organ disease requiring precise pressure regulation
- Need for frequent or multiple blood gas measurements
Non-invasive:
- Patients who are at risk of haemodynamic instability
Circulation - IV fluids: explain the rationale of fluid administration and the difference between colloids and crystalloids.
Colloids
- A phase-separated mixture in which one substance of microscopically dispersed insoluble or soluble particles are suspended throughout another substance
- Particles are too large to pass semi-permeable membranes so they stay in the intravascular spaces longer than crystalloids
- E.g. albumin, dextran, hydroxyethyl starch
Crystalloids
- Low-cost salt solutions with small molecules, which can move around easily when injected into the body
- E.g. saline
- Do not use crystalloids for patients with active bleeding
Adults (>16) - 1 unit of plasma to 1 unit of red blood cells to replace fluid volume
Children (<16) - 1 part plasma to 1 part red blood cells and base volume on child’s weight.
Circulation - Blood transfusion: recall the triggers for giving a blood transfusion.
- Symptomatic anaemia - SOB, dizziness, congestive heart failure, decreased exercise tolerance
- Acute sickle cell crisis
- Acute blood loss of more than 30% of blood volume
- Hb <8 g/dL (or <80)
Pain relief - Multi-modal analgesia: recall the principles of multimodal analgesia.
Combination of regional anaesthesia (single-shot or continuous central neuraxial or peripheral nerve blocks or local infiltration analgesia), opioid analgesics and non-opioid systemic analgesics (paracetamol, NSAIDs).
Pain relief - Pain: summarise approaches to the management of acute and chronic pain.
https://midessexccg.nhs.uk/about-us/the-library/medicines-management/clinical-pathways-and-medication-guidelines-1/chapter-4-central-nervous-system-2/3345-acute-and-chronic-combined-pain-guidelines-august-2019/file
Pain relief - WHO pain ladder: explain the WHO pain ladder.
Mild pain
- Non-opioid + adjuvant therapy
Mild to Moderate pain
- Weak opioid or multimodal + non-opioid + adjuvant therapy
Moderate to Severe Pain
- Strong opioid + non-opioid + adjuvant therapy
Severe to Very Severe Pain
- Interventional treatments + non-opioid + adjuvant therapy
Pain relief - Regional analgesia/anaesthesia: explain the rationale and management of regional analgesia/anaesthesia
Regional anaesthesia may be classified anatomically as follows: (a) infiltration anaesthesia (extravascular or intravascular); (b) peripheral nerve blockade (minor or major nerve block); and (c) central neural blockade (epidural or subarachnoid block).
The local anaesthetic agents commonly employed for regional anaesthesia may be classified according to their relative potency and duration of activity into: (1) agents of low potency and short duration, e.g. procaine and chloroprocaine; (2) agents of moderate potency and duration, e.g. lignocaine (lidocaine), mepivacaine and prilocaine; and (3) agents of high potency and long duration, e.g. amethocaine (tetracaine), bupivacaine and etidocaine.
In general, the onset, duration and quality of regional anaesthesia are enhanced by an increase in dose achieved by either an increase in concentration or in the volume of anaesthetic solution, and by the concomitant use of a vasoconstrictor drug, adrenaline (epinephrine). However, the local anaesthetic properties of the intrinsically more potent and longer acting agents are influenced less by the addition of adrenaline, particularly when such agents are employed for central neural blockade of the epidural type.
Pain relief - Analgesic Drugs: recall dosage, mode of administration, indications and contraindications of common analgesic drugs.
NON-OPIOIDS
Paracetamol
- No demonstrable anti-inflammatory activity
- Less irritant to stomach
- Overdose causes hepatic damage not apprent for 4-6 days
Aspirin
Indications: Headache, transient MSK pain, dysmenorrhoea, pyrexia, anti-platelet
Contraindications: Gastric irritation (can se enteric coated preparations), warfarin sodium interaction
Other NSAIDS
- Chronic disease + pain + inflammation
- Short-term treatment of mild to moderate pain
- Dysmenorrhoea, secondary bone tumours, post-operative analgesia
OPIOIDS + NON-OPIOIDS
- Reduce scope for effective titration of individual components in management of pain of varying intensity
- E.g. 8mg codeine phosphate + paracetamol / aspirin
- Full dose opioid - e.g. 60mg codeine phosphate
- SE: N&V, constipation, drowsiness, respiratory depression, dependence
ADDITION OF CAFFEINE
- Stimulant
- Enhances analgesic effect
- SE: Alerting effect, mild habit-forming effect, provocation of headache
MORPHINE
- Most valuable opioid analgesic for severe pain
- SE: N&V, euphoria, mental detachment
- Given regularly every 4 hours, or every 12-24 hours as modified-release preparations
BUPRENORPHINE
- Opioid agonist and antagonist properties
- Withdrawal symptoms, pain, abuse potential, dependence
- Longer duration of action than morphine - 6-8 hours
- Partially reversed by naloxone hydrochloride
DIAMORPHINE HYDROCHLORIDE (Heroin!)
- Less nausea and hypotension
- Palliative care!
- Effective doses injected in smaller volumes
ALFENTANIL, FENTANYL, REMIFENTANIL
- Injection for intra-operative analgesia
- Available in transdermal drug delivery system as a self-adhesive patch changed every 72 hours
METHADONE HYDROCHLORIDE
- Less sedating than morphine, acts for longer periods
- Do not administer more than twice daily to avoid the risk of accumulation and opioid overdose
- Used instead of morphine in occasional patient who experiences excitation or exacerbation of pain with morphine
OXYCODONE HYDROCHLORIDE
- Efficacy and side-effect profile similar to that of morphine
- Second-line drug if morphine is not tolerated or does not control the pain
PENTAZOCINE
- Agonist and antagonist properties and precipitates withdrawal symptoms - e.g.pain in patients dependent on other opioids
- Avoided after MI as may increase pulmonary and aortic blood pressure as well as cardiac work
PETHIDINE HYDROCHLODIRDE
- Prompt but short-lasting analgesia
- Less constipating
- Higher doses is less potent
- Used in labour, but morphine or diamorphine hydrochloride is preferred for obstetric pain
TAPENTADOL
- Opioid receptor agonist
- Inhibits noradrenaline reuptake
- N&V & constipation less likely to occur
TRAMADOL HYDROCHLORIDE
- Opioid effect
- Enhancement of serotonergic and adrenergic pathways
- Fewer side effects, psychiatric reactions have been reported though
CODEINE PHOSPHATE
- Relief of mild to moderate pain where other painkillers such as paracetamol or ibuprofen have proved ineffective
DIHYDROCODEINE TARTRATE
- Similar efficacy to codeine phosphate
- Higher doses provide additional pain relief at the cost of more nausea and vomiting
MEPTAZINOL
- Low incidence of respiratory depression
- Onset 15 minutes, length of action 2-7 hours
NB: Post-operatively - morphine most widely used.
Pain relief - Anti-emetic drugs: recall dosage, mode of administration, indications and contraindications of common anti-emetic drugs.
ANTIHISTAMINES - e.g. promethazine
- Vomiting during pregnancy
PHENOTHIAZINES
- Dopamine antagonists
- Act centrally by blocking CTZ
- For N&V associated with diffuse neoplastic disease, radiation sickness, emesis caused by opioids, GA, cytotoxics
- E.g. prochlorperazine, perphenazine, trifluoperazine, chlorpromazine hydrochloride
- Can be administered by rectal suppositories, buccal tablets
HALOPERIDOL & LEVOMEPROMAZINE
- In terminal illness - antipsychotic drugs
METOCLOPRAMIDE HYDROCHLORIDE
- Acts directly on GI tract
- Superior to phenothiazines for emesis associated with gastroduodenal, hepatic and biliary disease
DOMPERIDONE
- Acts at CTZ
- Less likely to cause sedation and dystonic reactions as doesn’t cross BBB
- Used to treat nausea caused by dopaminergic drugs in Parkinson’s
GRANISETRON & ONDANSETRON
- In patients receiving cytotoxics and post-operative N&V
PALONOSETRON
- Moderately or highly emetogenic cytotoxic chemotherapy
- Combination with netupitant (neurokinin 1-receptor antagonist)
DEXAMETHASONE
- Associated with cancer chemotherapy
- Used alone or in combination with metoclopramide hydrochloride, prochlorperazine, lorazepam, 5HT3-receptor antagonist
APREPITANT & FOSAPREPITANT & ROLAPITANT
- Neurokinin 1-Receptor Antagonists
- Aprepitant - chemotherapy
- Fosaprepitant - prevention of cisplatin-based chemotherapy
- Rolapitant - chemotherapy prevention
- Given with dexamethasone + 5HT3-receptor antagonist
NABILONE
- Synthetic cannibinoid
- Add on treatment for chemotherapy-induced nausea and vomiting unresponsive to conventional anti-emetics
PREGNANCY
- Antihistamine - e.g. promethazine
- Prochlorperazine or metochlopramide hydrochloride alternative
- 24-48 hours without symptoms settling then seek specialist opinion
- Hyperemesis gravidarum - regular antiemetic therapy, IV fluids, electrolytes, nutritional support, thiamine
POST-OP
- 5HT3-receptor antagonists
- Droperidol
- Dexamethazone
- Phenothazines - e.g. prochlorperazine
- Antihistamines - e.g. cyclizine
MOTION SICKNESS
- Hyoscine hydrobromide
- Antihistamines
- Promethazine (if require sedative effect)
- Cyclizine or Cinnarizine - less sedating
NB: Domperidone, metochlopramide hydrochloride, 5HT3-receptor antagonists, phenothiazines ineffective in motion sickness.
VESTIBULAR DISORDERS
- Betahistine dihydrochloride - analogue of histamine
- Vertigo, tinnitus, hearing loss associated with Meniere’s disease
- Diuretic combined with salt restriction - vertigo associated with Meniere’s disease (also antihistamines - cinnarizine, phenothiazines - prochlorperazine)
Temperature control - Homeostasis: recall the normal homeostatic control of temperature and explain how this is affected by anesthesia.
Perioperative hypothermia develops in three distinct phases:
(1) anaesthetic-induced vasodilation during induction of anaesthesia results in core-to-peripheral redistribution of body heat and decreases core temperature 1–1.5°C during the first hour of general anaesthesia
(2) subsequently core temperature decreases linearly as heat loss to the environment exceeds metabolic heat production
(3) after 3–5 h of anaesthesia, core temperature often stops decreasing.
This core temperature plateau results from reactivation of thermoregulatory vasoconstriction which decreases cutaneous heat loss and constrains metabolic heat to the core thermal compartment.
Perioperative hypothermia is associated with numerous complications such as myocardial ischaemia, increased risk of wound infection and coagulopathy. On the other hand temperatures only 1–3°C below normal provide substantial protection against cerebral ischaemia and hypoxaemia in numerous animal species. Consequently, most anaesthesiologists believe mild hypothermia is indicated during operations likely to cause cerebral ischaemia such as carotid endarterectomy and neurosurgery or cardiac procedures.
Temperature control - Warming devices: recall methods of warming patients during surgery, including warm air blanket, fluid warmers and heat moisture exchangers.
WARM AIR BLANKET
Filters air and then forces warm air through a disposable blanket which covers the patient before, during and after surgery
FLUID WARMERS
A medical device used in healthcare facilities for warming fluids, crystalloid, colloid, or blood product, prior to being administered (intravenously or by other parenteral routes) to body temperature levels in order to prevent hypothermia in physically traumatized or surgical patients.
HEAT AND MOISTURE EXCHANGER
Devices used in mechanically ventilated patients intended to help prevent complications due to drying of the respiratory mucosa, such as mucus plugging and endotracheal tube (ETT) occlusion.
Emergence: recognise the requirements for emergence from anaesthesia and the indications for ongoing sedations.
Receptors:
- Gamma-aminobutyric acid type A (GABAA) receptors
- N-methyl D-aspartate (NMDA) receptors
- α2 receptors
- Opioid receptors
- Neuronal hyperpolarization-activated cyclic nucleotide-gated (HCN) family channels
- Two-pore domain potassium (K2P) channels.
Functionally, the drug-receptor interaction leads to several changes in cortical and subcortical signals, inducing alterations in the connectivity across brain regions. Complex mechanisms underlie alterations of cortico-cortical and cortical-subcortical functional connectivity. The different general anesthetics activate different molecular patterns, expressed as different functional alterations in brain connectivity and different electrophysiological correlates.
Volatile agents, for instance, interfere with frontal-posterior connectivity and this effect reverberates on the gamma (20–60 Hz) oscillations which have a pivotal role in arousal and maintenance of consciousness.
Again, propofol provokes a quick anteriorization of alpha rhythms (8–12 Hz) and promotes the propagations of slow-delta oscillations across the cortex, inducing a functional disruption of the connectivity between distinct cortical areas.
Yet, dexmedetomidine impairs the thalamo-cortical functional connectivity mostly expressed as spindle waves (12–16 Hz) in the frontal area.9 The matter is extremely complex, as alterations in connectivity within distinct brain regions lead to different depths of anesthesia.
Thus, changes in thalamic-cortical connectivity lead to the induction of the loss of consciousness (LoC) whereas changes in the cortico-cortical functional connectivity and a further impact on cortico-subcortical functioning induce the completion of the induction mechanism and the maintaining of the surgical anesthesia status.
During the AE phase, mechanisms responsible for LoC and anesthesia maintenance are gradually reversed. Nevertheless, these “passive” processes are associated with specific awakening mechanisms.
Of note, these active processes include several ascending arousal brain pathways where the thalamus plays a key role.
Apart from the thalamus, other arousal-promoting brain regions such as the substantia nigra, the ventral and laterodorsal tegmental areas of the midbrain, the dorsal raphe, and the locus ceruleus (LC) as well as the basal forebrain (BF), and lateral hypothalamus are involved. Thus, it has been postulated the existence of a mesencephalic arousal pathway.
The hypothalamus is also implicated in these wake-promoting processes. Orexin also known as hypocretin, is an endogenous wakefulness-promoting substance.
Hypothalamic orexinergic neurons are involved in both the sleep-to-wake transition and maintenance of wakefulness.
This orexinergic system is functionally connected with other structures such as basal ganglia that regulate the awakening processes during the AE. Interestingly, serotonergic neurons in the dorsal raphe nucleus receive projections from orexinergic neurons, concurring in sleep-wakefulness modulation.
Among these complex arousal networks, there are the LC norepinephrine (LCNE) system and posterior hypothalamic histaminergic tuberomammillary nuclei (TMN). In particular, the LCNE is the main structure of the so-called LCNE arousal system which includes the posterior cingulate cortex, thalamus, and basal ganglia. Another arousal pathway is the brainstem ascending reticular arousal system (ventral and dorsal pathways) which originates from the pontine/midbrain regions and develops cholinergic cortical projections through interactions with the thalamus, hypothalamus, and the BF region.
In summary:
i) AE is not just a passive process due to a cessation of the action of general anesthetics
ii) the arousal mechanisms at the end of GA are produced by structures deeper in the brain, rather than being activated within the neocortex
iii) rather than a single awakening system, it is more correct to refer to an arousal network. It is composed by the cholinergic basal forebrain, dopaminergic ventral tegmental area, anterior cingulate cortex, orexinergic hypothalamic, serotonergic raphe, LCNE, and histaminergic TMN neurons.
Recovery - Observations: recall the observations measured in recovery.
- HR
- RR
- SpO2
- BP
- Temperature
- Sedation Score - AVPU, Michigan sedation score, GCS
- Pain Score
- Nausea Score
Physical assessment:
- Airway, Breathing, Circulation & Disability Assessment
- Baseline Observations including RR, Resp effort, SpO2, HR, BP, Temp
- O2 requirements
- IV fluids
- Analgesia
- Urine output
- Reportable blood loss
- Assessment of wound sites / dressings
- Presence of drains and patency of same
- NGT in situ
Recovery - Discharge: recall the criteria for discharge from recovery.
PACU Discharge Criteria:
- Clinical observations within age-appropriate limits
- Observations which fall within shaded areas of clinical observation chart, should be managed following the Medial Emergency Response Procedure
- Core temperature >36 degrees or >36.6 degrees for neonates
- Sedation score 2 or less (UMSS)
- No active vomiting
- Pain Managed
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