Awareness during Anesthesia

Groups at risk for awareness:

Awareness is due to too light plane of anesthesia. It is more likely where muscle relaxants are used. They may be due to:

1-Inadequate anesthetic dose:

-Emergency surgery

-Hypotensive anesthesia

-Cardiac surgery

-Inability to monitor dose in TIVA

-Obstetric surgery

-Normal variability in MAC

2-Resistance:

-Hypermetabolic state

-Smokers

-Obesity

-Alcoholic

3-Equipment malfunction:

-Breathing circuits

-TIVA pump malfunction or line disconnection

-Vaporizers

Prevention:

-Recognize patients at risk

-Anesthesia machine pre-use check and knowing its mechanics & mechanisms

-Periodically check vaporizer level & provide adequate MAC levels

-Benzodiazepines at induction

-Use muscle relaxants ONLY when necessary

-Use of “BIS” monitoring in high-risk groups

-Be aware that some drugs may mask signs of awareness (e.g., β-blockers mask tachycardia)

Read More

Angioneurotic Edema

-A general term applied to the development of acute edema in the subcutaneous or submucous tissues.

-Anesthetic help may be sought during an attack, when edema of the lips, tongue, or larynx may cause respiratory problems.

Causes:

-Angioedema may be secondary to the release of histamine, or many other vasoactive substances such as bradykinins, prostaglandins, or leukotrienes.

-It is thought that pediatric and adult angioedemas differ. Children are less likely to require intubation or tracheostomy than adults. Recent work in adults has shown substantial increases in plasma bradykinin during attacks of hereditary, acquired, or captopril-induced angioedema.

-The development of edema may be:

1. Part of a general anaphylactoid or anaphylactic reaction to a drug, bite, sting, or the ingestion of a substance.

2. A manifestation of hereditary angioneurotic edema, a condition caused by a deficiency of C1 esterase inhibitor.

3. A result of an acquired form of C1 esterase inhibitor deficiency which usually occurs in association with a B-lymphocyte malignancy.

4. A known side effect of a drug. Recently, there have been several cases of angioedema reported, usually involving the tongue, floor of the mouth, epiglottis, and aryepiglottic folds, secondary to treatment with ACE inhibitors. Most occur in the first week of treatment but may be delayed for up to a year. Can be associated with elevated serum bradykinin levels.

Presentation:

1. There may be a history of a predisposing factor. This can be ingestion of food or a drug, an infection, bite or sting, a family history of angioedema, or a B-lymphocytic malignancy.

2. Edema of subcutaneous tissue may occur alone or be accompanied by hypotension.

3. Patients taking ACE inhibitors have developed problems in the perioperative period. Angioedema of the tongue occurred 15 min after tracheal tube removal.

4. A patient with acquired C1 esterase inhibitor deficiency undergoing cardiopulmonary bypass had massive activation of the common pathway, coagulopathy, pulmonary edema, and circulatory collapse.

Management:

1. Assessment of severity of airway obstruction.

2. If the angioedema is part of an anaphylactic or anaphylactoid reaction:

a) Give epinephrine (adrenaline) IV or IM, 0.1–0.5 mg depending on the severity.

b) If the condition is severe and involves the glottis, an airway should be established, either by tracheal intubation, cricothyroidotomy, or tracheostomy.

c) Second-line treatment includes IV fluids, chlorpheniramine IV 10–20 mg, and steroids.

3. Hereditary angioneurotic edema, or acquired C1 esterase inhibitor deficiency. These do not respond to epinephrine (adrenaline) or antihistamines, but to replacement of the deficient inhibitor by either:

a) An infusion of fresh frozen plasma.

b) Purified C1 esterase inhibitor concentrate.

Read more ☛ Acquired C1 Esterase Inhibitor Deficiency

Read More

Acquired C1 Esterase Inhibitor Deficiency

-This may be a familial or, more rarely, an acquired disorder involving the complement system.

-The acquired form is mostly associated with a B-lymphocyte malignancy, and antibodies have been detected against abnormal immunoglobulins present on the malignant B-cells. The reaction between the two causes C1 activation, which in turn produces a secondary reduction in the concentrations of C1, C2, and C4 and reduced functional activity of the C1 esterase inhibitor.

-This form must be distinguished from the physical forms of angioedema that occur in response to food, drugs, or insect bites, or in association with connective tissue disorders.

-Recently, many patients have developed angioedema in response to treatment with ACE inhibitors, particularly enalapril and captopril. Substantial increases in plasma bradykinin have been demonstrated during attacks of hereditary, acquired, and captopril-induced angioneurotic edema.

Preoperative Abnormalities:

1. Intermittent attacks of angioneurotic edema that can involve any part of the body, and result from extravasation of intravascular fluid and protein into subcutaneous and mucosal structures.

2. As with hereditary angioneurotic edema, there is a low level of C1 esterase inhibitor, and sometimes life-threatening episodes of edema of the upper airway may develop in response to stress or local trauma, particularly dental treatment. However, attacks of edema may occur without any obvious reason, and recurrent abdominal pain may be a presenting feature.

3. As with the hereditary form, epinephrine (adrenaline), antihistamines, and steroids are ineffective for prophylaxis, and for treatment of these attacks.

4. The two conditions may be distinguished by the fact that in the acquired form the onset is late, no family history is elicited, no complement abnormalities are found in the patient’s blood relatives, and the underlying malignancy may already have been diagnosed.

5. Differentiation may now be made on measurement of the C1q subunit of C1; patients with acquired deficiency have a decreased level of C1q, compared with those with the hereditary form, in whom the C1 level is normal.

Anesthetic Problems:

1. Tracheal intubation and manipulation of the upper airway may precipitate local angioneurotic edema, for which treatment with epinephrine (adrenaline), steroids, and antihistamines is ineffective. Edema may also occur after dental extractions.

2. Although tranexamic acid has been recommended to prevent attacks in both forms, venous thrombosis has been reported after its prophylactic use during surgery in the acquired disease.

Management:

1. Progestogen derivatives: Increase the hepatic synthesis of a C1 esterase inhibitor. Its prophylactic value is acquired and hereditary disorders have been reported.

a) Danazol (200 mg TDS) should be given preoperatively but may take several days to become effective.

b) Stanozolol (0.5–8 mg/day) can also be used.

-The lower levels will be required for maintenance, whilst higher levels may be needed in the initial stages. A patient with autoimmune C1 EI, who was known to be carrying a male fetus, was given short-term therapy at 40 weeks of gestation.

2. Tranexamic acid: It should be avoided in the acquired form, especially in the presence of a thrombocytosis.

3. Fresh frozen plasma, and C1 esterase inhibitor concentrate: Used as preoperative prophylaxis and treatment.

Read more ☛ Angioneurotic Edema

Read More

Oculo-cardiac Reflex and Oculo-respiratory Reflex

1-Oculo-cardiac Reflex

Definition:

Bradycardia following traction on the extraocular muscles, especially the medial rectus.

The reflex is particularly active in children. Bradycardia may be severe and may lead to asystole. Other arrhythmias may occur, e.g. ventricular ectopics or junctional rhythm.

Bradycardia may also follow pressure on/or around the eye, fixation of facial fractures, retrobulbar block (pressure associated with local infiltration), ocular trauma, or manipulation of tissue in orbital apex after enucleation,...etc. The reflex has been used to stop SVT with an eyeball massage.

Pathway: (Figure 1)

Afferent pathways are via the trigeminal nerve (ciliary ganglion to the ophthalmic division of trigeminal nerve to Gasserian ganglion to the main trigeminal sensory nucleus).; efferents are via the vagus nerve (afferents synapse with the visceral motor nucleus of the vagus nerve located in the reticular formation and efferents travel to the heart and decrease output from the sinoatrial node).

Prophylaxis:

Reduced by anticholinergic drugs administered as premedication or on induction of anesthesia.

Management:

If it occurs, surgery should stop, and atropine or glycopyrrolate should be administered.

Retrobulbar block does not reliably prevent it; local infiltration of the muscles has been used instead.

Figure 1: Oculo-cardiac Reflex Pathway

2-Oculo-respiratory Reflex

Definition:

Hypoventilation following traction on the external ocular muscles. Reduced respiratory rate, reduced tidal volume, or irregular ventilation may occur.

Pathway:

Thought to involve the same afferent pathways as the oculocardiac reflex, but with efferents via the respiratory centers.

Heart rate may be unchanged, and the reflex is unaffected by atropine.

Read More

Tachycardia during Anesthesia

Tachycardia during Anesthesia

Definition:

-Pulse rate greater than 100 beats/min. in adults

Causes and Management:

1-Light anesthesia, Pain:

-Hypertension, sweating, lacrimation, reactive pupils, movement 

Treatment: Deepening the anesthesia, Analgesia 

2-Drug induced:

-Anticholinergic drugs, Catecholamines, Oxytocin 

3-Hypovolemia:

-Actual (due to fluid loss): 

Treatment: Fluid replacement 

-Effective (due to vasodilatation): 

Treatment: Vasopressors (α-agonists, Ephedrine) 

4-Hypercarbia:

Treatment: Check soda lime, Increase minute ventilation, and Exclude malignant hyperthermia 

5-Hypoxia:

The initial response is tachycardia 

Treatment: Of the cause

6-Cardiac dysrhythmia:

-SVT: 

Treatment: Of the cause, Carotid sinus massage, Adenosine, Verapamil, Amiodarone, Digoxin 

-VT: 

Treatment: Of the cause, Lidocaine, Amiodarone, Synchronized DC (if sustained or hemodynamically unstable) 

7-Endocrine disease:

-Pheochromocytoma, Thyrotoxic crisis 

Treatment: α-blockers, β-blockers 

8-Sepsis:

9-Malignant hyperthermia:

The first sign is tachycardia 

Treatment: According to management guidelines

Read More

Bradycardia during Anesthesia

Bradycardia during Anesthesia

Definition:

-Pulse rate less than 60 beats/min. in adults

-Pulse rate less than 80 beats/min. in infants

-Pulse rate less than 100 beats/min. in neonates

Causes and Management:

1-Hypoxia:

-Late response is bradycardia

Treatment:

-Of the cause, Oxygenation, Anticholinergics

2-Drug induced:

-High-concentration volatile anesthetics, Opioids, Succinylcholine, Anticholinesterases (Neostigmine), Low dose atropine (Benzold-Jarisch reflex, paradoxical bradycardia), β-blockers, Digoxin

Treatment:

-Decrease concentration of volatile anesthesia, Anticholinergics

3-Vagal stimulation:

- Airway instrumentation, Visceral traction, Extraocular muscle traction, Anal dilatation, Cervical dilatation

Treatment:

-Stop traction or dilatation, Anticholinergics

4-Spinal anesthesia:

-High spinal anesthesia affecting T1-T4 (Cardiac accelerator fibers)

Treatment:

-Support circulation, Anticholinergics, Ephedrine (if associated with hypotension)

5-Ischemic heart disease:

-Ischemic changes affecting the conducting system

Treatment:

-Anticholinergics if indicated

6-Endocrine disease:

-Hypothyroidism

Treatment:

-Anticholinergics

7-Metabolic:

-Hyperkalemia

Treatment:

-Correction of potassium level, Anticholinergics

8-Neurological:

-Cushing’s reflex due to increased ICP

Treatment:

-Of the cause, Anticholinergics if indicated

9-Cardiovascular fitness:

-Trained athlete (High resting vagal tone, Large stroke volume)

N.B.: Anticholinergic drugs (Atropine, Glycopyrrolate, Hyoscine)

Read More

Fat Embolism Syndrome (FES)

Fat Embolism Syndrome (FES)

➧ Fat embolism can be difficult to diagnose. It most often follows a closed fracture of a long bone but there are many other causes.

Epidemiology:

➧ Incidence of this complication ranges from 0.5 to 11% in different studies. It varies considerably according to the cause. Patients with fractures involving the middle and proximal parts of the femoral shaft are more likely to experience fat embolism. Age also seems to be a factor with young men at the highest risk.

Etiology:

1-Fractures: Closed fractures produce more emboli than open fractures. Long bones, pelvis, and ribs cause more emboli. Sternum and clavicle cause less. Multiple fractures produce more emboli.

2- Orthopedic Procedures: Intramedullary nailing of long bones, Fixation of cemented hip prosthesis.

3-Massive soft tissue injury

4-Severe burns

5-Liposuction

6-Bone marrow biopsy

7-Bone marrow harvesting and transplant

8-Cardio-pulmonary bypass

9-Non-traumatic settings occasionally lead to fat embolism. These include conditions associated with: 

-Fatty liver

-Acute pancreatitis

-DM

-Osteomyelitis

-Bone tumor Lysis

-Pathological fractures

-Sickle cell crisis (causing bone infarcts)

-Decompression sickness

-Prolonged corticosteroids therapy

-Cyclosporine A solvent

-Parenteral lipid infusion

Sevitt’s classification:

1-Subclinical (Incomplete) form: Fat emboli present in blood and lungs, no symptoms/signs

2-Non-fulminant (Classic) form: Pulmonary dysfunction, cerebral dysfunction, petechiae

3-Fulminant form: Rare, rapid onset (within hours) of acute cor-pulmonale, respiratory failure, coma, and death.

Principal clinical features (triad) of FES:

1-Respiratory failure (dyspnea and hypoxia)

2-Cerebral dysfunction (confusion)

3-Petechiae

➧ Clinical features usually present between 24-72 h. after trauma (lucid interval). This is especially after fractures, when fat droplets act as emboli, becoming impacted in the pulmonary microvasculature and other microvascular beds, especially in the brain.

➧ Embolism begins rather slowly and attains a maximum in about 48 h.

➧ The initial symptoms are probably caused by mechanical occlusion of multiple blood vessels with fat globules that are too large to pass through the capillaries.

➧ The vascular occlusion in fat embolism is often temporary or incomplete as fat globules do not completely obstruct capillary blood flow because of their fluidity and deformability.

➧ The late presentation is thought to be a result of hydrolysis of the fat to more irritating free fatty acids which then migrate to other organs via the systemic circulation.

➧ It has also been suggested that paradoxical embolism occurs from shunting.

Clinical Presentation:

➧ There is usually a latent period of 24-72 h. between injury and onset.

➧ Symptoms: There is vague pain in the chest and shortness of breath.

➧ Signs: The onset is sudden, with:

-Restlessness

-Fever occurs, often at more than 38.3° C with a disproportionate tachycardia.

-Drowsiness with oliguria is almost pathognomonic.

➧ CNS signs: including a change in the level of consciousness, are common. They are usually non-specific and have the features of diffuse encephalopathy with acute confusion, stupor, coma, rigidity, or convulsions. Cerebral edema contributes to neurological deterioration.

Diagnostic Criteria:

A) Gurd's and Wilson’s Criteria:

-Diagnosis requires at least one sign from the major criteria and at least four signs from the minor criteria. (Table 1)

Table 1: Gurd's and Wilson’s Criteria

B) Schönfeld’s Criteria:

-Diagnosis requires a score of more than 5. (Table 2)

Table 2: Schönfeld’s Criteria

C) The clinical diagnosis is assured if all three of the following criteria are present within 72 h. after traumatic fracture:

1-Unexplained dyspnea, tachypnea, arterial hypoxia with cyanosis, and diffuse alveolar infiltrates on chest X-ray.

2-Unexplained signs of cerebral dysfunction, such as confusion, delirium, or coma.

3-Petechiae over the upper half of the body, conjunctiva, oral mucosa, and retina.

Differential Diagnosis:

➧ Dyspnea, hypoxia, and abnormal CXR: can occur with thrombo-embolism and pneumonia.

➧ Cerebral dysfunction: can occur with hypoxia or meningitis but the rash of meningococcal septicemia is all over and spreads rapidly. It can also occur as a late feature of head injury.

➧ Thrombotic Thrombocytopenic Purpura (TTP).

Investigations:

CBC: 

-Hematocrit: is decreased, occurs within 24-48 h., and is due to intra-alveolar hemorrhage. 

-Platelets: are decreased.

Serum Lipase: is increased, but this is not pathognomonic as it occurs in any bone trauma.

Serum Calcium: is decreased.

Cytological Examination: urine, blood, and sputum may detect fat globules that are either free or in macrophages. This test has low sensitivity and a negative result does not exclude fat embolism. 

Arterial Blood Gases: will show hypoxia, PaO₂ usually less than 60 mmHg, and hypocapnia. Continuous pulse oximeter monitoring may enable hypoxia from fat embolism to be detected in at-risk patients before it is clinically apparent.

ECG: Ischemia, Rt. Ventricular strain, Rt. Axis deviation, RBBB, Arrhythmia.

Chest X-ray: may show evenly distributed, fleck-like pulmonary shadows (Snow Storm appearance), increased pulmonary markings, and dilatation of the right side of the heart.

CT Head: (to rule out intracranial pathology).

CT Chest: (to rule out chest pathology).

Management:

A) Supportive

1-Ensuring good arterial oxygenation: High flow rate of oxygen is given to maintain the arterial oxygen tension in the normal range.

2-Restriction of fluid intake and Diuretics: to minimize fluid accumulation in the lungs so long as circulation is maintained.

3-Maintenance of intravascular volume: is important because shock can exacerbate the lung injury caused by FES. Albumin has been recommended for volume resuscitation in addition to the balanced electrolyte solution, because it not only restores blood volume but also binds fatty acids, and may decrease the extent of lung injury.

4-Mechanical ventilation (APRV) and Positive End-Expiratory Pressure (PEEP): may be required to maintain arterial oxygenation.

B) Pharmacological

1-Corticosteroids: Methylprednisolone (membrane stabilizer, decreases endothelial damage caused by free fatty acids).

2-Low dose heparin: 2500 u / 6 h. (reduce the degree of pulmonary comprise and intravascular coagulation despite the risk of hemorrhage and intravascular lipolysis).

3-Dextran-40: (decreases intravascular thrombosis when ESR is elevated).

4-Ethanol: (decreases lipolysis)

5-Dextrose: (decreases free fatty acid mobilization)

6-DVT prophylaxis

7-Nutrition

C) Surgical:

1-Prompt surgical stabilization of long bone fractures within 24 h. reduces the risk of the syndrome.

2-Use of vacuum or venting during reaming of long bones.

3-Prophylactic IVC filter in at-risk patients.

Prognosis:

➧ The mortality rate from FES is 5-15%. Even severe respiratory failure associated with fat embolism seldom leads to death.

➧ The prognosis is worse in older patients and those with more severe injury but is not affected by gender.

➧ Criteria of bad prognosis: Sevitt’s class, Serum lipase, Lipuria, ARDS.

Prevention:

➧ Early immobilization of fractures seems to be the most effective way of reducing the incidence of this condition.

Read More

Bone Cement Implantation Syndrome (BCIS)

Bone Cement Implantation Syndrome (BCIS)

Bone Cement constituents:

-Bone cement is an acrylic polymer that is formed by mixing two sterile components: 

a) Powder:

1-Polymer: Polymethyl methacrylate/co-polymer (PMMA) 

2-Initiator: Benzoyl peroxide (BPO) 

b) Liquid:

1-Monomer: Methyl methacrylate (MMA) 

2-Accelerator: N, N-Dimethyl para-toluidine (DMPT)/diMethyl para-toluidine (DMpt) 

-To make the cement radiopaque, a contrast agent is added, either zirconium dioxide (ZrO₂) or barium sulphate (BaSO₄). 

-When the two components are mixed, the liquid monomer polymerizes around the pre-polymerized powder particles to form hardened PMMA. During this polymerization process, heat is generated, due to an exothermic reaction, and reaches temperatures of around 82–86 °C. 

Incidence:

-The incidence of BCIS in cemented orthopedic procedures is approximately 20%. 

-The incidence of a severe reaction resulting in cardiovascular collapse within this group is 0.5-1.7%. 

Orthopedic procedures incidence:

-Cemented hemiarthroplasty (highest incidence) 

-Total hip replacement 

-Knee replacement surgery 

BCIS typically occurs during:

-Bone cementation and prosthesis insertion 

-Femoral reaming (before cementation) 

-Joint reduction and limb tourniquet deflation (after cementation) 

Patients at high risk of cardio-respiratory compromise:

-Male sex 

-Increasing age 

-ASA class III / IV 

-Significant cardiopulmonary disease 

-Chronic obstructive pulmonary disease 

-Use of diuretics 

-Use of warfarin 

Conditions that can increase the incidence of BCIS:

-Osteoporosis, Bone metastasis, and Concomitant hip fractures. 

These conditions may be associated with increased or abnormal vascular channels, through which marrow contents can more readily migrate into the circulation, resulting in emboli. 

Pathophysiology of BCIS:

a) Embolization of the Medullary Contents:

-During surgical cementation and prosthesis insertion, the cement is intentionally pressurized to force it into the interstices of the bone, to improve bonding between the cement and bone. 

-The cement then expands in the space between the bone and the prosthesis, further pressurizing air and the medullary contents, forcing them into circulation. These embolic contents include fat, marrow, cement, air, bone particles, and aggregates of platelets and fibrin. 

-When these medullary contents embolize, they may reach the lungs, heart, and/or coronary circulation, causing the characteristic hypoxia and right ventricular dysfunction, leading to hypotension. 

b) Histamine release, Hypersensitivity, and Complement activation:

-Contact with bone cement (Methyl Methacrylate), leads to an increase in blood levels of anaphylactoid complements (C3a and C5a) and histamine, which are potent mediators of vasoconstriction and bronchoconstriction. 

-These mediators result in an increase in pulmonary vascular resistance, causing ventilation/perfusion disturbances, hypoxia, right ventricular failure, and cardiogenic shock. 

Clinical Picture:

-Hypoxia 

-Sudden loss of arterial blood pressure 

-Pulmonary hypertension 

-Arrhythmias 

-Loss of consciousness 

-Cardiac arrest 

-Under general anesthesia, a significant drop in systolic blood pressure (SBP) may herald cardiovascular collapse, whilst a sudden drop in end-tidal pCO₂ may indicate right heart failure leading to a catastrophic reduction in cardiac output. 

-In an awake patient under a regional anesthetic, early signs of BCIS may include dyspnea and/or altered sensorium. 

BCIS Severity Spectrum:

a) Non-fulminant BCIS:

-Characterized by a significant, yet transient, reduction in arterial oxygen saturation and SBP in the peri-cementation period. 

b) Fulminant BCIS:

-With profound intraoperative cardiovascular changes, progressing to; arrhythmias, shock, or cardiac arrest. 

Classification of BCIS Severity: based on the degree of hypoxia, hypotension, and conscious level (Table 1)

Table 1: Classification of BCIS Severity

Prophylaxis:

a) Anesthesia:

1-Ensure adequate hemodynamic optimization pre- and intra-operatively 

2-Keep SBP within 20% of the pre-induction value 

3-Prepare vasopressors in case of cardiovascular collapse 

4-Confirm awareness that cement is about to be prepared/applied 

5-Maintain vigilance for cardiorespiratory compromise 

b) Orthopedic:

1-Inform the anesthetist before cement application 

2-Wash and dry the femoral canal 

3-Apply cement retrograde, utilizing a suction catheter and intramedullary plug in the femoral shaft 

4-Avoid excessive pressurization (3rd generation technique) 

Management:

-Administration of 100% inspired oxygen is first-line therapy, with airway control if necessary. 

-Invasive hemodynamic monitoring (if not already in place), should be established. 

-In cases of severe BCIS (when the patient has been arrested, or in a peri-arrest condition), standard advanced cardiopulmonary life support (ACLS) algorithms and procedures should be followed. 

-Fluid resuscitation to maintain Rt. Ventricle preload, and inotropes to support ventricular contractility.

-Vasopressors (such as Phenylephrine and Noradrenaline) primarily cause peripheral vasoconstriction, and increase aortic blood pressure, which in turn supports coronary artery blood flow, and thus improves myocardial perfusion and contractility. 

-Use of vasopressors and inotropes should be continued into the postoperative period as necessary, under the management of the intensive care unit (ICU).

Read More

Anesthetic Precautions for Bloody and Lengthy Surgery

Anesthetic Precautions for Bloody and Lengthy Surgery

A) Precautions for Bloody Surgery

1-Decrease blood loss by:

➧ The surgical site elevation is 10-15°

➧ Use of tourniquet

➧ Local infiltration of epinephrine

➧ Use of topical hemostats 

➧ Application of hypotensive anesthesia

➧ Controlled mechanical ventilation (decrease venous return → decrease Cardiac output and PaCO₂)

➧ Use antifibrinolytic agents: (Aprotinin, Epsilon Amino Caproic Acid, Tranexamic acid)

➧ Use desmopressin (DDAVP)

➧ Keep patient normothermic

➧ Give IV Calcium (to prevent citrate toxicity and help coagulation)

➧ Restrict diagnostic phlebotomies

➧ Avoid: (Atropine, Ketamine, Pancuronium) (increase: Heart rate, Blood pressure, Endogenous catecholamines)

2-Restore Blood loss rapidly by:

➧ Prepare type-specific, cross-matched blood

➧ Preoperative autologous blood donation

➧ Apply normovolemic hemodilution

➧ Use cell saver devices (Blood Salvage)

➧ Insert wide bore IV cannulae

➧ Use blood substitutes

➧ Use rapid infusion devices

➧ Use blood warmers

B) Precautions for Lengthy Surgery

1-Decrease Hypothermia by:

➧ Monitoring by a temperature probe

➧ Increase ambient room temp. ≥ 24° (in Adults), ≥ 26° (in Pediatrics)

➧ Cotton wrapping of the limbs and head

➧ Use a warming blanket/mattress

➧ Warm IV fluids

➧ Warm irrigating fluids

➧ Warm humidified inspired gases

➧ Use low-flow anesthesia

➧ Use blood warmers

2-DVT prophylaxis.

3-Pressure sore prophylaxis (Padding of pressure points).

4-Eye protection (Tap and Pad).

5-Invasive monitoring (CVP, IBP).

6-Avoid N₂O (causes: Bone marrow depression, Megaloblastic anemia, Agranulocytosis, Peripheral neuritis, Immune response depression).

7-Use Isoflurane (More rapid recovery).

8-Insert nasogastric tube (to avoid gastric distension).

9-Use high volume, low-pressure ETT cuff (with frequent monitoring of intracuff pressure or use intracuff saline).

10-Avoid hypovolemia (by: Monitoring, Fluid chart, IV fluids).

Read More

Propofol Related Infusion Syndrome (PRIS)

➧ It is a rare syndrome that affects patients undergoing long-term treatment with high doses of the anesthetic and sedative drug propofol. 

➧ It is associated with high doses and long-term use of propofol (>4 mg/kg/hr for more than 24 hours). It occurs more commonly in children, and critically ill patients receiving catecholamines and glucocorticoids are at high risk.

Clinical Picture:

➧ Arrhythmias 

➧ Progressive Myocardial Failure 

➧ Cardiovascular Collapse 

➧ Lipemia 

➧ Hypertriglyceridemia 

➧ Acute Renal Failure 

➧ Rhabdomyolysis 

➧ Metabolic acidosis 

➧ Hyperkalemia 

➧ Hepatomegaly 

➧ Green urine (phenol metabolites), (Figure 1) 

➧ It is often fatal 

Figure 1: Green Urine

Laboratory Results:

➧ Elevated serum lactate 

➧ Elevated CPK 

➧ Myoglobinuria 

➧ Hyperkalemia 

➧ Hypertriglyceridemia

ECG changes:

➧ ST elevation in precordial leads V1 to V3

Predisposing factors for developing PRIS:

➧ Propofol dose >4 mg/kg/h 

➧ Propofol infusion >48 h 

➧ Presence of “triggering factor” (i.e. catecholamine infusion or corticosteroids) 

➧ Inadequate delivery of carbohydrate 

➧ Critical Illness 

➧ Severe Cerebral Injury 

➧ Sepsis 

➧ Pancreatitis 

➧ Trauma

Prevention:

➧ Avoid high propofol doses and minimize the duration of infusion in high-risk patients 

➧ Avoid lipid overload by assessing all sources of fat calories (e.g., parenteral nutrition, enteral nutrition). 

➧ Monitoring of serum triglycerides in any patient receiving propofol in doses >4 mg/kg/h or >48 is highly recommended. 

➧ Assure adequate provision of carbohydrates. 

➧ Depletion of carbohydrate stores can promote mobilization of fat stores and increase lipid metabolism. This, in turn, increases circulating fatty acid load and may predispose patients to PRIS. 

➧ Theoretically, it is, therefore, possible that early adequate carbohydrate intake may prevent PRIS by preventing the switch to fat metabolism. 

➧ There is some suggestion that providing a carbohydrate intake of 6–8 mg/kg/min. can suppress fat metabolism and thus prevent PRIS.

Treatment: (Supportive) 

➧ Early recognition of the syndrome and discontinuation of the propofol infusion reduces morbidity and mortality. 

➧ Once a patient presents with symptoms compatible with PRIS, propofol infusion should be discontinued promptly and an alternative sedative agent should be initiated. 

➧ Cardiovascular support by the combination of vasopressors and inotropes. 

➧ Cardiac pacing should be considered. 

➧ Hemodialysis or hemofiltration to decrease the plasma concentrations of circulating metabolic acids and lipids. 

➧ Extracorporeal membrane oxygenation (ECMO) for combined respiratory and circulatory support. 

Read More