ANESTHESIA IN PATIENT WITH HEAD TRAUMA PREOPERATIVE MANAGEMENT Initial resusitation: -ensure patent airway -assumed C-spine injury until radiographically proven otherwise - in-line stabilization requirement: maintaining head in neutral position during airway manipulation -adequate ventilation / oxygenation -maintaining hemodyanamic stability approximately 70% of head trauma patients have hypoxemia Hypoxemia may be complicated by: -pulmonary contusion -fat emboli -neurogenic pulmonary edema Neurogenic pulmonary edema may result from: -systemic hypertension -pulmonary hypertension Intubation -patients with head trauma are considered ‘full stomachs’ -require cricoid pressure during ventilation and intubation -thiopental 2 – 4 mg/kg or propofol 1.5 – 3 mg/kg -muscle relaxant (short acting) although succinylcholine is controversial: may increase ICP and induce hyperkalemia Options for an anticipated difficult intubation -awake intubation -fiberoptic bronchoscope -tracheostomy Contraindication -blind nasaltracheal intubation in a basilar skull fracture -signs of basilar skull fracture: CSF rhinorrhea or otorrhea, hemotympanic, ecchymosis “raccoon sign”, “battle sign” INTRAOPERATIVE MANAGEMENT Common maintenance technique: Barbiturate + opiod + N20 + muscle relaxant N20 should generally be avoided when: -air is entrained within the cranial vault -peroids of hypotension Intraoperative hypotension -may occur after induction due to: vasodilation effects of induction agents combined with presumed hypovolemia -treated with α adrenergic (phenylephrine) -volume infusion -fluid resusitation may be better corrected with colloid solutions or blood opposed to crystalloid solution infusion -advantage of colloid or blood infusion opposed to crystalloid is less incidence of cerebral edema -severe hypotension: may be treated with dopamine infusion -maintain hematocrit above 30% Useful monitors in hypotensive setting: -arterial line -central venous pressure -pulmonary artery occlusion pressure -TEE -ICP Intraoperative hypertension Commonly treated with: -additional doses of thiopental -hyperventilation -inhalational anesthetic agent -hypertension + tachycardia is often controlled with β adrenergic blockade -cerebral perfusion pressure (CePP) should be maintained between 70 – 110 mmHg -vasodilators generally best avoided until the dura is open -atropine may be used for excessive vagal tone (ex. bradycardia) Excessive hyperventilation is avoided in head trauma patients: -to avoid excessive reduction in CBF -PaC02 between 25 – 30 mmHg is considered optimal in reducing ICP and maintaining adequate CBF Common cardiac manifestations following head trauma injury include: -dysrhythmias -ecg changes including: -T wave changes -U wave changes -ST segment changes -QT interval changes Disseminated intravascular coagulation (DIC) in severe head injury associated with: -large release of brain thromboplastin -diagnosed by coagulation profile/studies Treatment of DIC includes: -platelets -fresh frozen plasma (FFP) -cryoprecipitate DIC in severe head injury often associated along with ARDS: -may require mechanical ventilation If PEEP is required, should be applied when: -ICP monitoring is being evaluated -dura is open Diabetes insipidus often seen in severe head injury involving: -the pituitary stalk -large amount of dilute urine -should be diagnosed with measurements of urine and serum osmolality -should assess the response to vasopressin ANESTHESIA FOR INTRACRANIAL MASS LESION PREOPERATIVE MANAGEMENT investigate into intracranial hypertension CT/MRI : -brain edema -midline shift > 0.5 cm -ventricular size Physical Examination Neurological assessment: +/- change in mental status +/- sensory deficits +/- motor deficits Medications Patient taking? -corticosteroids -diuretics -anticonvulsants Laboratory Evaluation: Rule out: -hyperglycemia (corticosteroid induced) -electrolyte abnormalities (diuretic and ADH effects on electrolyes) -anticonvulsant levels (ensure therapeutic levels of anticonvulsant medications) Premedication -corticosteroids: continued upto day of surgery -anticonvulsants: continued upto day of surgery -pts with nl ICP: may benefit with benzodiazepines (ex, diazepam PO, midazolam IM/IV) -pts with ↑ ICP: should avoid premedication due to possible respiratory depressants effects: ↑PaC02, ↑CBF: further↑ICP INTRAOPERATIVE MANAGEMENT Monitoring -standard monitors -arterial line -urinary bladder catherization -central venous catherization -evoked potentials -ICP monitoring Arterial line -allows for continuous blood pressure monitoring -helps to regulate and optimize adequate cerebral perfusion pressure and resultant CBF -allows for frequent arterial blood gas samples which helps to monitor ventilatory status: PaC02 -zeroing the arterial line at the level of the head (external meatus of the ear) helps to monitor cerebral perfusion pressure Continous blood pressure monitoring very important during: -induction -hyperventilation -intubation -postioning -surgical manipulation -emergence Central venous catheter -generally required for patients receiving vasoactive medications -helps to assess volume status Site of CVC placement is controversial: -internal jugular vein: may impede venous drainage from the brain and may be involved with carotid artery puncture -median basilic vein: in order to avoid the complications involved with internal jugular vein CVC placement -external jugular vein good alternative for CVC placement -subclavian vein good alternative for CVC placement Urinary catheter placement -often placed due to commonly used diuretics -long nature of neurosurgical procedures -helps to assess fluid therapy management Evoked potentials -helps to assess integrity of neuropathways during neurosurgical procedures ex. VEP: helps protect optic nerve damage used during resection of large pituitary tumors Intracranial pressure monitoring -ventriculostomy: allows for the removal of CSF in order to decrease the ICP -subdural bolt -electronic ICP monitoring Induction Critical periods of patients with increased cranial pressure: -induction of anesthesia -endotracheal intubation Improved intracranial compliance, reduced ICP with: -osmotic diuresis -steroids -CSF removal via ventriculostomy s/p intubation Goal: -smooth induction -gentle intubation -avoidance of arterial hypertension: ↑BP leads to ↑ICP , results in ↓CePP and possible brain herniation ↓BP may lead to ↓ CePP creating vulnerability to cerebral ischemia Common induction includes -thiopental or propofol with hyperventilation -muscle relaxation -opiods -esmolol Benefit of propofol: short recovery time benefit of etomidate: hemodynamic stability with less cardiodepressant effects ex. unstable patient etomidate 6 – 8 mg with fentanyl 5 ug/kg in unstable cardiac patients Monitoring -standard ASA monitors -A-line -central venous catherization -urinary catherization -evoked potentials -ICP monitoring Arterial line -continuous blood pressure monitoring to ensure adequate and optimal cerebral perfusion pressure and resultant CBF -frequent ABG samples to closely monitor and regulate PaC02 -zeroing arterial line at the level of the ear (external auditory meatus) allows for closer approximation of the CePP Central venous catherization -indicated in patients requiring vasoactive medications -site of central venous catherization is controversial: Internal jugular vein Medial basilic vein: external jugular vein subclavian vein Internal jugular vein -may impede venous drainage from the brain -possible carotid puncture with complications of expanding hematoma -expanding hematoma may impede venous drainage with resultant increased ICP Urinary bladder catherization -commonly used in diuresis -long duration of surgical procedure -assessing fluid therapy Evoked potentials -helps assess and monitor integrity of nerve pathways ex. VEP helps prevent optic nerve damage used during resection of large pituitary tumor ICP monitoring -ventriculostomy: -subdural bolt -electronic ICP monitoring induction Goal: -smooth induction -gentle intubation -avoidance of arterial hypertension: ↑BP : ↑ICP: possible consequence of brain herniation ↓BP : ↓CePP: vulnerable to cerebral ischemia with resultant edema and inc ICP Critical periods for patients with increased ICP -induction of anesthesia -endotracheal intubation Methods to improve intracranial compliance in patients with increased ICP: -osmotic diuresis -corticosteroids -CSF removal via ventriculostomy before intubation Induction for mass lesion may include: -thiopental or propofol with hyperventilation deep anesthesia with hyperventilation to reduce ICP fluctations -muscle relaxation prevent straining or bucking which may increase ICP -opiods ex. fentanyl 5 – 10 ug/kg blunt the sympathetic response to both laryngoscopy and intubation -esmolol ex. 0.5 – 1 mg/kg prevent tachycardia in hypertensive patients Benefit of propfol: short recovery time benefit of etomidate : hemodynamic stability: prevent cardiodepression ex. etomidate 6 – 8 mg with fentanyl 5 ug/kg for an unstable cardiac patient induction option for a patient with reactive airway disease: thiopental with isoflurane along with hyperventilation Muscle relaxants with hemodynamic stability include: -rocuronium -vecuronium -pipecuronium -doxacurium succinlycholine may be associated with an increase in ICP Treatment of hypertension upon induction may include: Vasodilators are generally avoided until the dura is open: -esmolol bolus -NTP -deepening anesthesia with thiopental or propofol -NTG -hyperventilation with lose dose isoflurane (less than 1 MAC) -Hydralazaine -CCB Treatment of intraoperative hypotension may include: Vasopressors in incremental doses: -ephedrine -phenylephrine Positioning of patient during a neurosugical procedure: mass lesion Supine position: head elevation within 15 – 30 degree excessive head flexion/extension -frontal craniotomy -facilitate venous drainage -may restrict jugular venous drainage -temporal craniotomy -facilitate CSF drainage -restricted drainage may lead to ↑ICP -parieto-occipital craniotomy Maintenance Techniques -nitrous –opiod –muscle relaxant -opoid – lose dose inhalational agent -total intravenous anesthesia (TIVA) Periods of greatest stimulation include: -laryngoscopy / intubation -skin incision -dural opening -periosteal manipulation -closure optimizing ICP reduction and maintaing adequate CePP intraoperative hyperventilation: PaC02 25 –30 mmHg Intravenous fluid management -glucose free isotonic cystalloid or colloids are preferred (ex. LR, NS) -glucose containing iv fluids avoided due to vulnerability of hyperglycemia (corticosteroid induced hyperglycemia) -hyperglycemia may increase ischemic brain injury -fluid requirements in neurosurgical procedures generally are lower than calculated fluid requirements -reduced iv fluid administration in order to prevent further cerebral edema and increase in ICP POSTOPERATIVE MANGEMENT Emergence -patients with removal of mass lesion are generally extubated at the end of the case -emergence should be well controlled and smooth Straining and bucking on the ETT may may cause: -intracranial hemorrhage -increase in ICP -cerebral edema Patients who remain intubated should be: -sedated -paralyzed -hyperventilated Model of a well controlled and smooth emergence: -while the skin is being closed, try having the patient begin breathing spontaneously -once the dressing is intact and the table is back in optimal orientation for emergence discontinue all inhalational anesthetics -deliver 100% oxygen -reverse neuromuscular blockade -may administer iv lidocaine 1.5 mg/ kg rapid awakening allows for neurological assessment postoperatively the patient should be closely monitored in the ICU for neurological function and hemodynamic stability ANESTHESIA MANAGEMENT FOR INTRACRANIAL ANEURYSM PREOPERATIVE MANAGEMENT -blood should be available prior to the start of the procedure -determine whether rupture of the cerebral aneurysm has occurred -investigate into presenting signs if increased ICP -review CT imaging for hydrocephalus, ventricular enlargement and or midline shift Relative contraindications for elective hypotension include history of: -hypertension -renal insufficieny -cardiac disease -cerebral vascular disease Premedication: -patients with normal ICP generally may receive sedation pre-induction -patients with increased ICP generally should avoid sedation pre-induction to avoid the risk of hypercarbia INTRAOPERATIVE MANAGEMENT blood should be available prior to the start of the procedure Overall goal of intraoperative management includes: -prevent rupture of the cerebral aneurysm -prevent rebleeding of the cerebral aneurysm -prevent factors which may create cerebral ischemia -prevent factors which may initiate cerebral vasospasm Intraoperative monitoring -ASA monitors -intra-arterial line -central venous catheter -pulomary artery pressure Intraoperative hypertension: sudden increases in arterial blood pressure should be avoided -may be avoided with deeper levels of anesthesia -deep level of anesthesia may be occomplished by: -adequate fluid resusitation guided by CVP trend with increased surgical level of anesthesia May occur during: -tracheal intubation -surgical stimulation Intraoperative hypotension -reduces transmural tension across the aneurysm -decreases risk of rupture of cerebral aneurysm -decreases risk of rebleeding from ruptured cerebral aneurysm -facilitates surgical clipping -improves surgical visualization in amidst of bleeding -may decrease surgical blood loss -more pron in patients with preoperative use of CCB (nimodipine, nicardipine ) -due to decrease systemic vascular resistance (SVR) of CCB use Cerebral protection during intraoperative hypotension -use of temporary vascular clips -thiopental administration -mild hypothermia Intraoperative hyperventilation -generally avoided to prevent excessive decreases in CBF clinical example: hyperventilation should be avoided in a patient with cerebral aneurysm with cerebral vasospasm Intraoperative diuresis -once the dura is opened -facilitates surgical exposure -reduces tissue trauma from surgical retraction ex. mannitol diuresis Intraoperative diuresis prior to dura opening : -rapidly decreases ICP which may promote rebleeding -tamponading effect of the dura upon the aneurysm is removed -resultant increased risk of rebleeding -therefore best to avoid osmotic diuresis prior to dura opening ANESTHESIA MANAGEMENT FOR ARTERIOVENOUS MALFORMATION Anesthetic management of arteriovenous malformation: -blood should be available in the OR prior to the start of the procedure -preparation for expectant extensive blood loss -large bore IV access -direct intra-arterial pressure monitoring -embolization prior to surgery helps to reduce operative blood loss -surgical access facilitated by hyperventilation and mannitol diuresis -altered cerebral autoregulation may occur due to surgical resection of AVM lesion -altered cerebral autoregulation may lead to hyperemia and cerebral edema due to increased BP -control of blood pressure often accomplished with β blockers ANESTHESIA FOR STEREOTACTIC SURGERY Stereotactic procedures indicated for treatment of: -disorders of involuntary movement -diagnosis / treatment of deeply positioned brain tumors -intractable pain -epilepsy Stereotactic procedures may be performed under: -local anesthesia: allows for periodic evaluation of patients status -sedation/amnesia: accomplished with a propofol infusion. Patient should have a normal ICP for sedation -general anesthesia in case of emergency craniotomy. Issues involved in converting from local anesthesia to general anesthesia may include: -platform and localizing frame attached to patient’s head for stabilazation -limited range of motion of neck while mask ventilation prior to intubation (due to localizing frame) Possible options for emergent airway management while converting to general anesthesia (ex. emergent craniotomy) -ETT intubation first definitive preference -LMA alterative to a failed ETT intubation -mask ventilation last resort amidst emergent conditions awake intubation with fiberoptic bronchoscope: -ideal and safe modality of airway management under limited exposure and movement of the patient’s airway ex. stereotactic head frame limiting: -range of motion of neck -exposure/visibility for direct laryngoscopy ANESTHESIA FOR SURGERY OF THE SPINE Spine surgery commonly performed for: -symptomatic nerve root compression -cord compression due to degenerative changes -correct deformities ex. scoliosis -decompress the spinal cord -spinal fusion s/p spinal trauma -spinal tumor resection -vascular malformation -abscess Compression of nerve root may occur: -protrusion of an intervertebral disk into the spinal canal -protrusion of an osteophytic bone segment into the spinal canal Herniation of intervertebral disc -usually occurs at L4-L5 or C5-C6 -usually occurs in patients between ages 30 –50 yrs PREOPERATIVE MANAGEMENT Evaluate for: -limited range of motion of the neck -neck braces which may complicate airway management -pre-existing respiratory impairment -pre-existing neurological impairment (document) INTRAOPERATIVE MANAGEMENT Factors which may complicate intraoperative anesthetic management: -prone position -multiple levels often involved -instrumentation (Harrington rod, pedicle screw fixation) -potential for large amounts of intraoperative blood loss Positioning during spine surgery prone position: -induction of anesthesia and intubation in supine position -patients turned into prone position with smooth gentle positioning requiring at least 4 people -neck must remain in neutral position -head may be displaced to the side in the prone position or faced down with use of a cushioned holder -parallel foam rolls for the chest to rest on facilitates ventilation -arms should be to the side with elbows flexed to prevent excessive abduction of shoulders Physiologic/ hemodynamic changes which may occur while positioning in prone position: -blunted or inhibited postural sympathetic reflexes -resultant hypotension -impedance to venous return due to abdominal compression -possible increased intraoperative blood loss due to epidural vein engorgement Extra caution in prone position to avoid: -corneal abrasions -retinal ischemia due to pressure on the ocular globe -pressure necrosis Vulnerable areas to pressure necrosis while in prone position include: -nose -ears -forehead -breast -genitalia Supine position: -allows for anterior approach to the cervical spine Supine position may increase risk of intraoperative damage of: -traceha -esophagus -recurrent laryngeal nerve -sympathetic chain -carotid artery -jugular vein