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Todd Kinnick, DO Journal Club August 11, 2004 Continuous Perineural Infusions at Home: Narrowing the Focus Regional Anesthesia and Pain Medicine January-February 2004 Chelly/Williams University of Pittsburgh School of Medicine Postoperative pain in ambulatory surgery Use of “at home” perineural infusions of local anesthetic Use has increased because of Ambulatory infusion pumps Reported beneficial outcome after wound infusion of local anesthetic Research and individuals experiences in the use of continuous nerve block techniques for postop analgesia after major orthopedic surgery Introduction of Ropivicaine and its preferential sensory block as well as a safety profile better than bupivacaine Interscalene perineural ropivacaine infusion: a comparison of two dosing regimens Ropivacaine 0.2% with a perineural infusion at 8 ml/h provides potent analgesia following moderately painful shoulder surgery High basal rate limits infusion duration because of local anesthetic reservoir Non electronic pumps are generally restricted to a maximum of 500ml and pain often extends past 60 hours Can the basal rate of an interscalene perineural ropivacaine infusion be decreased by 50% with a concurrent 200% increase in patient-controlled bolus dose without compromising infusion benefits in ambulatory patients Enrollment Unilateral shoulder surgery desiring interscalene perineural catheter Be able to understand the possible local anesthetic related complications, study protocol and care of catheter and pump Have a “caretaker” who would remain with them during the local anesthetic infusion Exclusion Criteria Any contraindication to interscalene nerve block Any known heart or lung disease Baseline O2 sats of less than 98% on room air History of opioid dependence Allergy to study medications Current chronic analgesic therapy Known hepatic or renal insufficiency Peripheral neuropathy Morbid obesity Catheter infusion regimens Ropivacaine 0.2% Basal infusion 8ml/h and 2ml/h patient controlled bolus available every 1 hour Basal infusion of 4ml/h and a patient controlled bolus dose of 6 ml available every 1 hour Portable electronic infusion pumps attached to the 500 ml reservoir Patient education Medication log Oral analgesic (oxycodone 5/500) Pair of non sterile gloves Self addressed and stamped padded envelope for pump return Effectiveness of infusion Direct Indirect Average pain worst pain Oral analgesic use Associated sleep disturbances 1650 cumulative hours of infusion data Nightly questionnaire What was the worst pain you have felt? While you were resting, what was the average pain you have felt? Did you have difficulty sleeping last night because of pain? Did you awaken last night because of pain? If yes, how many times Have you had any fluid leakage from the catheter site? Would you describe the leakage as just once in a while, or nearly continuously? How satisfied are you with your pain control? Discussion Decreasing the basal infusion rate from 8 to 4 ml/h lengthens infusion duration and provides similar baseline analgesia when patients supplement their block with large bolus dose At the expense of an increase in breakthrough pain incidence and intensity, sleep disturbances, and a decrease in analgesia satisfaction Many unanswered questions What is the best local anesthetic solution? What is the optimal volumes and durations for the infusions? What is the functional endpoint when considering the effectiveness of a post op pain protocol? Are adjuncts useful for the infusions? When are the perineural infusion indicated versus wound infusions or intra articular infusions? What role will continuous nerve infusions at home play in a number of orthopedic surgeries being performed as outpatient procedures (ie. Minimally invasive joint replacement and hip arthroscopy) Other questions Plan for physical therapy What was the surgical technique? (ACL vs ankle fusion) (ACL patellar tendon vs cadaver allograft) With new surgical technique are previously inpatient surgeries only becoming outpatient procedures? Who will field the phone calls? Low dose Bupivacaine: a comparison of hyperbaric and hypobaric solutions for unilateral spinal anesthesia Regional Anesthesia and Pain Medicine January-February 2004 Kaya/Oguz/Aslan/Kadiogullari Ankara, Turkey Background and Objectives Attempting to achieve unilateral spinal anesthesia for patients undergoing lower limb orthopedic surgery by using: Small doses of local anesthetic solution Pencil point directional needles Maintaining lateral decubitus for 15-30 minutes Hypobaric and hyperbaric bupivacaine Factors suggested to increase the rate of unilateral spinal anesthesia Lateral decubitus position Low dose of anesthetic solution Total dose of local anesthetic injected into the spinal canal in the most important factor (Doses as low as 4-6mg of bupiv for complete knee arthroscopy or inguinal hernia repair with a unilateral distribution of spinal block in 60-80% of patients) Pencil point needles Low speed of intrathecal injection Use of directional injection minimizes mixing within the CSF Study population 50 ASA physical status I-II patients aged 1860 years receiving spinal anesthesia for elective unilateral orthopedic surgery (toe, foot, and or ankle) Exclusion Criteria Receiving chronic analgesic therapy Marked back arthrosis or scoliosis Obesity (BMI < 30) Diabetes with or without peripheral neuropathy Mental disturbance Materials 26 gauge atraumatic modified pencil point needle (Atraucan is a double beveled needle) Hyperbaric Bupivacaine 7.5mg Hypobaric Bupivacaine 7.5mg 1.5 ml (density = 1.026 g/ml) at 0.5 ml/s without CSF aspiration or barbotage 4.2 ml (density = .997 g/ml) at 0.5 ml/s without CSF aspiration or barbotage Lateral position was maintained for 15 minutes Results Hyperbaric Unilateral Block in 20 patients (80%) while in the lateral position which decreased to 17 (68%) once turned supine Hypobaric Unilateral Block in 19 patients (76%) while in the lateral position which decreased to 6 patients (24%) once turned supine Hemodynamic changes were similar between the two group Initially the motor block on the hyperbaric side was greater for the first 10 minutes but at the end of the operation there was no difference between the two groups Regression of the motor block was faster in the hyperbaric group Results continued No patients required GA Two patients in each group felt some discomfort during the operations and received 100 mcgs of fentanyl One patient in each group required treatment for hypotension with 250 cc bolus of 0.9 NS Followed by Ephedrine 5 mg in each group One patient in the hypobaric group received 0.5mg of atropine for bradycardia None of the patients developed post dural puncture headache or urinary retention Advantages of this technique Minimal hemodynamic side effects with higher cardiovascular stability Reduces the incidence of clinically relevant hypotension to nearly 5% Faster recovery of motor function Increase patient satisfaction for not being totally paralyzed Faster recovery of bladder function Reduced delay in patient discharge Cost of these advantages Mainly represented by the delay in preparation time because of the 15 minute stay in the lateral decubitus position Comparing preparation times of either unilateral or conventional bilateral spinal block with the same small dose results in only a 5 minute difference Statistically significant but clinically negligible What if you placed your spinal in a “block room”? Preoperative corticosteroids for reactive airway Anesthesiology May 2004 Michael Bishop, MD UW School of Medicine Reactive Airway Disease Low frequency of adverse outcomes Reversible bronchoconstriction follow intubation is probably the rule rather than the exception Severe bronchospasm seems to be a serious complication of low but finite incidence Bronchospasm severe enough to require treatment is “probably” 1 in 250 Studies--Silvanus et al Patients were selected because of airway obstruction, which was untreated for at least 1 month, and a positive response after two puffs of albuterol Included patients whose FEV1 improved by more that 10% in response to albuterol Observed mean changes of 20% the reversibility of obstruction was not only statistically significant but also clinically relevant Study groups Three groups 1. no treatment other than albuterol just before intubation 2. five days of albuterol prior to intubation 3. five days of corticosteroid plus albuterol prior to intubation Results Within 1 day both the albuterol and the albuterol-corticosteroid group had significantly improved airway resistance Regardless of whether single-dose albuterol pre induction or prolonged albuterol treatment was used most patients experienced wheezing after intubation Only one patient receiving corticosteroid in addition to five days of albuterol experienced wheezing after intubation Corticosteroids Enhance the bronchodilatory effect of beta2 adrenergic receptor agonists Direct effect of corticosteroids on smooth muscle Increase the number of beta2 adrenergic receptors and their response to their receptor agonists Corticosteroids-continued Inhalational steroids are believed to take weeks to months to attain their full effect Systemically administered corticoids may evoke this effect within 48 hours Methylprednisolone is thought to yield higher lung parenchymal concentrations than cortisol and therefore preferred in systemic asthma treatment Should every patient with a history of RA disease receive a pre op trial of steroids Recent study from New Zealand found that over 50% of individuals followed from birth to 26 yrs complained of wheezing at some point and 14.5% continued to have occasional symptoms In US, 8% incidence for asthma is often cited Which patients should we consider for steroid treatment? Need to be realistic and recognize that the scheduled procedure may drive how aggressive we are with pre op steroids Highest risk patient Undergo abdominal or thoracic surgery and are at greatest risk for post op pulmonary complications Worst pulmonary function Attempts to improve lung function to personal best Any reason not to treat patients aggressively with corticosteroids Brief courses do not seem to be associated with significant effects on wound healing or infection Meta analysis of 51 studies (2,500 patients) found that a high pre op dose of methylprednisolone of 15-30 mg/kg was not associated with a significant increase in complication rates Delay surgery Many patients find high doses of steroids somewhat unpleasant Is there any reason to withhold beta blockers from high risk patients with CAD during non cardiac surgery Anesthesiology, January 2004 Kertai, Bax, Klein, Poldermans Erasmus Med Center, Rotterdam, Netherlands How often are beta blockers underused? Schmidt et al, (Arch intern med 2002) 158 patients undergoing major noncardiac surgery, of 67 were eligible to receive perioperative beta blockers only 25 (37%) did so Survey of Canadian Anesthesiologists 93% agreed beta blockers were beneficial in patients with known CAD 57% reported beta blocker use in these patients 34% of the regular users continued taking beta blockers beyond the early post op period What may be the reason for withholding beta blockers? May not be effective enough in reducing perioperative cardiac events Limited experience with respect to timing and dosing of perioperative beta blockers Contraindications to beta blockers Availability of effective alternative cardioprotective treatment strategies “Classic” contraindications Severe left ventricular dysfunction, exacerbation of reactive airway disease, Insulin dependent diabetes, worsening of symptoms of PVD Several investigators have demonstrated that PBB and long term use of “cardio selective” beta blockers (bisoprolol, atenolol, or metoprolol) was well tolerated with no substantial increase of adverse effects with these “classic contraindications” Potential absolute contraindications Major AV nodal conduction disease in the absence of a pacemaker Severe asthma or strong reactive airway disease In such situation, alpha 2 or less invasive anesthetic and surgical techniques should be considered Cardiovascular effects of beta blockade Supply and demand variables reduction in heart rate (increasing diastolic perfusion time) Diastolic time is curvilinearly related to HR, increasing rapidly below 75 BPM Reduction in Contractility (reducing O2 demand) Via reversal of the Bowditch-Treppe effect (increasing contractility with increasing HR) Cardiovascular effects of beta blockers (continued) Little influence on the primary variables influencing plaque vulnerability (lipid accumulation, matrix degradation, etc) Vulnerable plaques are stabilized through decreases in sympathetic tone Indirectly influence the determinants of shear stress Reduce inflammation Cardiovascular effects of beta blockers (continued) Potent antiarrhythmic effects (especially in setting of acute ischemia) Reduction in circulating free fatty acids via inhibition of lipolysis may protect against ventricular fibrillation Enhanced rate control in atrial dysrhythmias As a result of these properties of beta blockers, the intensity of myocardial ischemia is reduce and the extent of the MI can be decreased Studies Mangano et al 200 patients atenolol vs placebo in non cardiac surgery No difference in the incidence of perioperative MI Long term follow up 10% mortality with atenolol and 21% mortality with placebo Poldermans et al Bisoprolol and average of 30 days preop with the dose adjusted to achieve resting HR of 60 BPM Continued to receive beta blockers for two years selective beta1 blocker (bisoprolol) reduced cardiac death and MI in high risk patients for as long as 2 years after major vascular surgery Timing, hemodynamic targets and duration of PBB Practice guidelines of the American College of Cardiology/American Heart Association Start as soon as the eligibility of a high risk patient for surgery is confirmed (days to weeks before) Goal of resting HR of 60 BPM This would be most accurately assessed by response to exercise or adrenergic challenge Intermediate or high risk who are already receiving beta blockers need dobutamine stress echo Alternative cardioprotective treatment strategies Prophylactic coronary revascularization Coronary bypass grafting (combined risks of CABG and noncardiac surgery might exceed the risk of noncardiac surgery alone) Angioplasty with coronary stent placement (delay of surgery of a t least 6 weeks) Lipid lowering medications Poldermans et al demonstrated that statin use was associated with a more than 4 fold reduction of perioperative mortality in patients undergoing vascular surgery