Aneasthesia Pearls October 2012

ANAESTHESIA PEARLS
A good anaesthetist should keep following points in mind at the time of laparoscopic surgery
All patients undergoing laparoscopy should have a empty bowel. In the unlikely event of bowel damage, there is much less risk of contamination if the bowel is empty.
Good muscle relaxation reduces the intra-abdominal pressure required for adequate working room in abdominal cavity.
The inflation of stomach should be avoid during artificial ventilation using mask as this increases the risk of gastric injury during trocar insertion or instrumentation.
Anaesthesia Pearls
The distended stomach also hamper the visibility of calots triangle at the time of laparoscopic Cholecystectomy or laparoscopic bile duct surgery.
Tracheal intubation and intermittent positive pressure ventilation should be routinely used. This ensures airway protection and controls pulmonary ventilation to avoid hypocarbia.
The ventilatory pattern should be adjusted according to respiratory and haemodynamic performance of the individual patient.
Ventilation with large tidal volumes (12-15 ml/kg) prevents alveolar atelectasis and hypoxaemia and allows adequate alveolar ventilation and CO2 elimination.
Halothane increases the incidence of arrhythmia during laparoscopic surgery especially in the presence of hypercarbia so use of halothane should be avoided.
Isoflurane is the preferred volatile anaesthetic agent in minimal access surgery as it has less arrhythmogenic and myocardial depressant effects.
Patients should receive adequate airway humidification and protection against unintentional hypothermia because generally the duration of operation is more in laparoscopic surgery.
Excessive intravenous sedation should be avoided because it diminishes airways reflexes against pulmonary aspiration in the event of regurgitation.
Monitoring of PET CO2 is mandatory during laparoscopic surgery. The continuous monitoring of PET CO2 allows adjustment of the minute ventilation to maintain normal concentration of carbon dioxide and oxygen.
Airway pressure monitor is mandatory for anaesthetised patients receiving intermittent positive pressure ventilation.
Anaesthesia in Laparoscopy Dr. R.K. Mishra.
Anaesthesia for laparoscopic surgery – Paul Hayden and Sarah Cowman
Anesthesia for Laparoscopic Surgery – John H. Nguyen, MD, Pedro P. Tanaka, MD, PhD
Anesthetic Implications of Laparoscopic Surgery Anthony J. Cunningham
    • Local anesthetic systemic toxicity (LAST)

Local Estimated incidence of 4 per 10000.Lipid emulsion has emerged as a possible antidote for systemic toxicity. ASRA and AAGBIrecommend the same dosing for 20% lipid emulsion; A 1.5 mL/kg bolus administered over 1 min followed by A continuous infusion of 0.25 mL/kg/min until 10 min after hemodynamic stability is obtained Two additional boluses may be administered in the absence of a response to the first bolus, and the infusion rate may be increased to 0.5 mL/kg/min if there is persistent hypotension. Approximately 10 mL/kg lipid emulsion for 30 mins is recommended as an upper limit for initial administration.
The American Society of Regional Anesthesia and Pain Medicine (ASRA) expert panels recommendations for the prevention, diagnosis, and treatment of LAST.
   Prompt and effective airway management in order to prevent hypoxia and acidosis.
Treatment of seizures with benzodiazepines, propofol, or thiopental
Consideration of lipid emulsion administration at the first signs of LAST (after airway management); and Advanced Cardiac Life Support (ACLS) in the setting of cardiac arrest.
Modifications to ACLS include:

Avoidance of high-dose epinephrine (<1 mg/kg) as high doses have been shown to impair the function of lipid emulsion.
Avoidance of vasopressin, as animal models have found poor outcomes and pulmonary hemorrhage in the setting of lipid emulsion administration,
Avoidance of calcium-channel and beta-adrenergic blockers, and
Treatment of ventricular dysrhythmias with amiodarone instead of local anesthetics (lidocaine or procainamide).
Ref:
The Association of Anaesthetists of Great Britain and Ireland (AAGBI) also updated their guidelines for the management of severe local anesthetic toxicity in 2010.
ASRA Practice Advisory on Local Anesthetic Systemic Toxicity
    • Techniques to decrease hypotension with neuraxial anesthesia for cesarean delivery.

Expert Review of Obstetrics & Gynecology  Katherine W Arendt; Jochen D Muehlschlegel; Lawrence C Tsen
   Leg wrapping
Prehydration or co-load with intravenous colloid solution
Co-load with crystalloid intravenous solution
Lower dose intrathecal local anesthesia supplemented with opioid
Maternal left uterine displacement positioning
Consider epidural instead of spinal anesthesia
Phenylephrine infusion with rapid crystalloid co-load
Phenylephrine infusion with low-dose intrathecal bupivacaine
Phenylephrine infusion or boluses titrated to maintain a consistent heart rate
Prehydration/Cohydration
Colloid solutions have been found to be more effective than crystalloid solutions in prehydration to prevent hypotension, especially when at least 1 l of HES is used.
Crystalloid solutions are more beneficial in preventing hypotension when used as a co-load instead of as prehydration.
Ref:
Dyer RA, Farina Z, Joubert IA et al. Crystalloid preload versus rapid crystalloid administration after induction of spinal anaesthesia (coload) for elective caesarean section. Anaesth. Intensive Care 32(3), 351–357 (2004).
Ref:
Siddik-Sayyid SM, Nasr VG, Taha SK et al. A randomized trial comparing colloid preload to coload during spinal anesthesia for elective cesarean delivery. Anesth. Analg. 109(4), 1219–1224 (2009)
Ref:
Teoh WHL, Sia ATH. Colloid preload versus coload for spinal anesthesia for cesarean delivery: the effects on maternal cardiac output. Anesth. Analg. 108(5), 1592–1598 (2009).
Spinal Doses
The addition of opioids allows for lesser intrathecal local anesthetic dosing, and often lesser hemodynamic effects, while still allowing for adequate anesthesia.
Hyperbaric bupivacaine 9 mg, combined with fentanyl 20 mcg. demonstrated lesser hemodynamic effects
High-risk cardiac patients – intrathecal dose of 4–5 mg of heavy bupivacaine, along with 20–25 mcg fentanyl  and  was subsequently followed by the slow loading of epidural local anesthetic to achieve a T4 surgical level
Ref:
Ben-David B, Miller G, Gavriel R, Gurevitch A. Low-dose bupivacaine-fentanyl spinal anesthesia for cesarean delivery. Reg. Anesth. Pain Med. 25(3), 235–239 (2000).
Ref:
Hamlyn E, Douglass C, Plaat F, Crowhurst J, Stocks G. Low-dose sequential combined spinal-epidural: an anaesthetic technique for caesarean section in patients with significant cardiac disease. Int. J. Obstet. Anesth. 14(4), 355–361 (2005).
Vasopressors
Ephedrine – causes fetal acidosis and decreases in fetal base excess.
Phenylephrine – lesser fetal acid base alterations.
The phenylephrine infusion regimens are now widely employed clinically.
Ref:
Ngan Kee WD, Lee A, Khaw KS, Ng FF, Karmakar MK, Gin T. A randomized double-blinded comparison of phenylephrine and ephedrine infusion combinations to maintain blood pressure during spinal anesthesia for Cesarean delivery: the effects on fetal acid–base status and hemodynamic control. Anesth. Analg. 107(4), 1295–1302 (2008).
    • AIRWAY MANAGEMENT Part1

July 2010 C.Thompson: visual prompt for the DAS guidelines
Download Wall visual DAS guidelines.doc
Wall visual DAS guidelines
This case series reports on 65 consecutive children sedated for CT or MRI with intramuscular dexmedetomidine, administered either once or twice at a dose of 1-4 mcg/kg, the exact dose left to provider discretion, to achieve a target Ramsay score of 4 (asleep but briskly responsive to a light stimulus). 4 patients out of 65 required a second IM dose to achieve a Ramsay score of 4. Once Ramsay 4 was achieved, no other agents were given for the duration of the procedure. The mean dose was about 2.5 mcg/kg.
All 65 children successfully completed the study. Though 9 out of 65 patients developed transient hypotension, there were no adverse events that required intervention. 65 patients is not enough to conclusively demonstrate safety, but 100% efficacy is hard to beat.
Average time to sedation was 13 minutes. The average time from the end of the study to recovery was 22 minutes in the MRI group and 17 minutes in the CT group, with wide confidence intervals, i.e. there was no difference in recovery times.
   Suxamethonium is safer because it wears off quickly, potentially life saving in the can’t intubate can’t ventilate scenario
Suxamethonium produces faster and more optimal intubating conditions.
The contraindications to the use of sux are easy and obvious to spot
We are familiar with suxamethonium so why change?
Rebuttal
   If you think that you are safe using suxamethonium because the apnoeic period of sux is only 6 minutes, you are kidding yourself. 6 minutes of apnoea will likely lead to arrest, especially in an already compromised patient in a can’t inutbate can’t ventilate scenario.
The longer duration of action of rocuronium is actually an advantage, not a disadvantage. You’ll find this out when you try repeat laryngoscopy or a rescue technique – LMA, BVM, or a cric on a patient that is no longer paralysed and starting to move after the sux has worn off. This is where things start to really get interesting (not in a good way). Given that rocuronium can now be reliably and rapidly reversed with Sugammadex (although not available everywhere yet) the timing argument is irrelevant even if it were correct.
Suxamethonium may lead to faster desaturation as a result of increased O2 utilization secondary to motor fasciculations.
Sux maybe safe most of the time, but often, we are intubating in a hurry, without a full history on the patient – contraindications may not be obvious, until the patient arrests post intubation.
The Facts
Rocuronium
   Dose = 1.2mg/kg
Time of onset = approximately 50 seconds
Duration of effect = up to 40 minutes
Reversible – yes, Sugammadex (not available everywhere) takes 2-3 minutes
Suxamethonium (Succinylcholine in the US)
Dose = 1-1.5mg/kg
Time of onset = approximately 50 seconds
Duration of effect 6-12 minutes
Reversible – no
Summary
In the ED setting, when comparing roc at 1-1.2mg/kg to sux at 1-1.5mg/kg, there is:
No significant difference in time to intubate.
No significant difference in intubating conditions.
No significant difference in intubating success rate.
So whilst sux doesn’t suck (it’s actually a great drug), roc totally rocks 🙂
Amit Maini, ED Trauma Critical Care blog.
Pearls from the article include:
Pre-oxygenation extends the duration of safe apnoea in emergency tracheal intubation
Patients with normal respiratory drive should be pre-oxygenated for 3 minutes or take 8 maximal inhalation/exhalation breaths
NIV (non-invasive ventilation) should be considered for pre-oxygenation and ventilation during the onset phase of muscle relaxation in patients who cannot achieve saturations greater than 93-95 % with high FiO2
Patients should be positioned in the head up position whenever possible. In patients with spinal precautions, reverse trendelenburg can be used
Apnoeic oxygenation can extend the duration of safe apnoea when used with sedation and muscle relaxants. A nasal cannula set at 15L/min is an effective means of providing this during ED intubations.
For intubation, patients should be positioned to maximize upper airway patency before and during the apnoeic period, using ear to sternal positioning. Nasal airways and jaw thrust may help to create a patent airway.
In patients at high risk of desaturation, rocuronium may provide a longer duration of safe apnoea than succinylcholine.
You may not be familiar with one technique that we mention below, so-called “DSI” or Delayed Sequence Intubation.
Standard RSI consists of the simultaneous administration of a sedative and a paralytic agent and the provision of no ventilations until after endotracheal intubation. This sequence can be broken to allow for adequate preoxygenation without risking gastric insufflation or aspiration; we call this method “delayed sequence intubation” (DSI).
Managing difficult airways in obese patients. The best part is the simple mnemonic that makes it so easy to remember.
OBESE – AIRWAY

AIRWAY CORRECTION

Ref:
Positioning for Intubation in Morbidly Obese Patients A & A May 2006 vol. 102 no. 5 1592
THE MNEMONIC:
Remember with obese patients, build a BIG RAMPPPP
B:  BUY TIME: Increase FiO2, NIV, Optimise Medical Rx
I:  INDICATION FOR INTUBATION: do you really need to do it & do it now?
G:  GET HELP: Anaesthetics, ICU, ENT, Nurses, Orderlies
R:  RAMP: Build a big ramp!
A:  APNOEIC OXYGENATION: use nasal prongs to maintain diffusion of O2
M:  MINIMAL DRUGS: local anaesthetic spray/neb, ketamine/ketofol +/- sux/roc
P:  PRE-OXYGENATE WITH NIV
P:  PARALYSIS – ONLY IF NEEDED
P:  PLAN FOR FAILURE: Surgical airway kit by the bedside
P:  POST INTUBATION CARE
Ref:
Managing the Obese Difficult Airway
Posted in ANAESTHESIA PEARLS 2012

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