Anesthesia Grading Score for Patient Risk

The American Society of Anesthesiologists developed a grading score in 1963 to assess patient risk during surgery. The score ranges from one to five and uses Roman numerals to indicate the severity of a patient’s systemic disease. Patients without systemic disease are classified as grade I, while those with mild to moderate systemic disease that does not limit their activities are classified as grade II. Patients with severe systemic disease that causes functional limitations are classified as grade III, and those with severe systemic disease that poses a constant threat to life are classified as grade IV. Additionally, the letter E is added to indicate emergency surgery. Finally, patients who are moribund and unlikely to survive more than 24 hours with or without surgery are classified as grade V. This grading system helps anesthesiologists determine the appropriate level of care and monitoring needed during surgery.

Common Inducing Anaesthetic Agents and Their Uses

Propofol, etomidate, ketamine, midazolam, and thiopental are all commonly used inducing anaesthetic agents with varying properties and uses.

Propofol is the drug of choice for RSII procedures in normotensive individuals without obvious cardiovascular pathology. It has amnesic, anxiolytic, anticonvulsant, and muscle relaxant properties, but no analgesic effects.

Etomidate provides haemodynamic stability without histamine activity and minimal analgesic effects. It is used in RSI procedures in patients with raised intracranial pressure and cardiovascular conditions, often in combination with fentanyl.

Ketamine is a non-competitive glutamate N-methyl-D-aspartate (NMDA) receptor blocker that produces dissociative anaesthesia. It can be used for induction of anaesthesia in patients with hypotension, status asthmaticus, and shock, but is avoided in hypertensive patients due to relative contraindications.

Midazolam is a benzodiazepine with anticonvulsive, muscle relaxant, and anaesthetic actions. At higher doses or in combination with other opioids, it induces significant cardiovascular and respiratory depression.

Thiopental is administered intravenously as an inducing anaesthetic agent or as a short-acting anaesthetic. It is also used as an anticonvulsant agent and to decrease intracranial pressure in neurosurgical procedures.

Entonox: A Mixture of Nitrous Oxide and Oxygen

Entonox is a gas mixture of 50% nitrous oxide and 50% oxygen that is stored in cylinders. The cylinders have a French blue body with blue and white quarters at the top. It is important to note that if the gas mixture cools below its pseudocritical temperature of −6°C, the nitrous oxide and oxygen may separate out through a process called lamination. This can result in a potentially dangerous and hypoxic gas being administered.

Despite being a flammable mixture, Entonox is not considered explosive. It is effective in providing short-term analgesia and is safe for both infants and mothers. The onset of action occurs approximately 30 seconds after inhalation, and the duration of action after analgesia is approximately one minute.

It is important to distinguish nitrous oxide (N2O) from nitric oxide (NO) as they are not the same. Overall, Entonox is a useful gas mixture for providing short-term pain relief, but it must be stored and administered properly to avoid any potential risks.

Choosing the Correct Endotracheal Tube Size for an 8-Year-Old Child

When it comes to intubating an 8-year-old child, choosing the correct endotracheal tube (ETT) size is crucial. Cuffed ETTs are now considered safe for use in children, but not in neonates. To calculate the appropriate size of a cuffed ETT, use the formula (Child’s age/4) + 3.5. For an 8-year-old child, the correct size of a cuffed ETT would be 5.5 mm. If an uncuffed tube is preferred, use the formula (Child’s age/4) + 4 to calculate the tube size, which would be 6.0 mm for an 8-year-old child. It is important to note that using a cuffed tube offers more protection from aspiration. Avoid using a 4.5 mm cuffed ETT, as it is too small for an 8-year-old child.

Understanding Heat Loss During Surgery: The Role of Radiation, Convection, Conduction, Evaporation, and Respiration

During surgery, the body can lose heat through various mechanisms. Radiation, which accounts for 40% of heat loss, depends on factors such as body temperature and the environment. To combat this, patients are covered with warming methods like the Bair Hugger™. Convection, or air movement, contributes to 30% of heat loss, while conduction (5%) occurs through contact with the operating table and surrounding air. Evaporation (15%) is higher if the abdomen is open, and humidity is kept at 50% in the theatre to reduce it. Finally, respiration accounts for 10% of heat loss. Understanding these mechanisms can help healthcare professionals better manage patient temperature during surgery.

The Use of Nasopharyngeal Airways in Seizure Management

Nasopharyngeal airways are a valuable tool in managing patients with seizures. During a seizure, jaw rigidity can make it difficult to position an oropharyngeal airway, making a nasopharyngeal airway a better option. These airways are used to secure an open airway in patients with a decreased Glasgow Coma Scale (GCS) score and those who cannot tolerate an oropharyngeal airway due to an intact gag reflex. The correct size of the airway is chosen by sizing the width of the patient’s nostril to the circumference of the tube, and insertion is facilitated by using a water-based lubricant. However, nasopharyngeal airways should not be used in patients with a patent airway or those with basal skull fractures and coagulopathy.

Different Flow Rates of Cannulas for Infusions

Cannulas are small tubes inserted into a vein to administer medication or fluids. Different sizes and colors of cannulas are available, each with varying flow rates. The grey 16G cannula has the highest flow rate of 180 ml/min, while the blue 22G cannula has the lowest flow rate of 33 ml/min. The pink 20G cannula is the most commonly used in adults for standard infusions, with a flow rate of 54 ml/min. The green 18G cannula has a flow rate of 80 ml/min, and the orange 14G cannula has the largest size and highest flow rate of 270 ml/min. It is important to choose the appropriate cannula size and flow rate for each patient’s needs.

Resuscitation Council (UK) Recommendations for Choking Emergencies

When faced with a choking emergency, the Resuscitation Council (UK) recommends a specific course of action. If the patient is able to cough effectively, encourage them to do so. If not, but they are conscious, try five back blows followed by five abdominal thrusts (Heimlich manoeuvre) and repeat if necessary. However, if the patient becomes unconscious, begin CPR immediately. It is important to note that a finger sweep is no longer recommended as it can push the obstruction further into the airway. Additionally, high flow oxygen is necessary for breathing, but nasopharyngeal airways will not help in this situation. Removal with forceps is also not recommended as it can be hazardous. If the Heimlich manoeuvre fails, a cricothyroidotomy should be considered. While this procedure is recommended in the US and UK, it is not encouraged in some countries like Australia due to the risk of internal injury from over-vigorous use.

Diagnosis of Subarachnoid Haemorrhage

Subarachnoid haemorrhage can be diagnosed with a high degree of accuracy through an urgent CT scan, which can confirm the condition in 95% of patients. In most cases, a lumbar puncture is not necessary unless the patient’s medical history suggests the need for one and the CT scan results are normal. If a bloody tap is suspected, the number of red blood cells should decrease with each successive sample. If an LP is performed six hours after the onset of symptoms, the supernatant fluid should be examined for xanthochromia after centrifugation.

Cannabinoids and Their Effects

Cannabinoids are compounds found in the resin of cannabis sativa, with 9-tetrahydrocannabinol (9-THC) being the most important active component. However, the oral bioavailability of THC, whether in pure form or as part of marijuana, is low and highly variable, with effects taking anywhere from 0.5 to 3 hours to occur. Smoking marijuana also does not significantly increase bioavailability, with rates rarely exceeding 10-20%.

Interestingly, the analgesic effects of cannabinoids can be blocked by naloxone and other opioid receptor antagonists. Additionally, synthetic cannabinoids have been found to reduce inflammation caused by arachidonic acid by inhibiting eicosanoid production. Overall, the effects and limitations of cannabinoids is important for both medical and recreational use.