Perioperative Vision Loss and Spine Surgery

Perioperative Vision Loss and Spine Surgery:

2019 Update on this issue of concern in surgery of the spine in the prone position. Risk factors include hypertension, diabetes, peripheral vascular disease, coronary artery disease, previous stroke, carotid artery stenosis), obesity, and tobacco use, as well as male sex. It is advised to inform patients in whom prolonged procedures, substantial blood loss, or both are anticipated that there may be an increased risk of perioperative visual loss. 

Advice is offered to maintain blood pressure, and higher in those with hypertension. Deliberate hypotension should be avoided unless deemed absolutely essential. Head position should be at or above head level in a neutral position. Crystalloid or colloid alone or in combination can be used and blood products given based on hematocrit.

Adrenergic agonists may be used on a case-by-case basis when it is necessary to correct for hypotension. Procedures may need to be staged. 


Anesthesia and Brain Health

An international consensus statement on postoperative brain health discusses current evidence on Perioperative Neurocognitive Disorder (PND) in older patients (> 65).

Much of the evidence is inconclusive at present regarding best anesthesia or preventative strategies. No specific agent or regional anesthetic has been found consistently superior, and processed EEG such as BIS  have not universally proven effective. However raw EEG may have a place despite its complexity at present. Brain perfusion if only in terms of maintaining mean arterial pressure is essential.

Baseline preoperative cognition should be assessed and documented, and consent should encompass the risks of delirium and PND.

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Buprenorphine Peri-Operatively

A review on managing Buprenorphine in the perioperative period notes the disparate views and protocols in use ranging from continuing it to weaning off and replacing with full agonists. The overall conclusion is that the ‘main impetus for discontinuation, i.e., inadequate pain management, may be based on expert opinion and not on the existing evidence’…”no evidence against continuing buprenorphine perioperatively, especially when the dose is < 16 mg SL daily.

The authors recommend that future studies require standardized reporting of median doses, details on the route of delivery, dosing schedules and any dosing changes, and rates of addiction relapse, including long-term morbidity and mortality where possible”.

Consultation with the prescribing expert in substance use would seem highly advisable when such patients present to us to balance the probable greater need for analgesics with safety and relapse potential.



Management of Anesthesia for Sickle Cell Disease

An educational article on anaesthesia management for children with sickle cell disease.  End-organ damage like cerebrovascular disease, heart failure secondary to thrombotic disease or pulmonary hypertension is seen less frequently now as is chronic kidney disease caused by ischaemic damage and loss of renal tubules. Vaccination should be comprehensive. The most common acute complications are infection and vaso-occlusive episodes. “Multiple splenic microinfarcts secondary to sickling is an early complication, with 90% of affected children reported to have functional asplenia by age 6 yr. This leads to an increased risk of bacterial infections, most notably with S. pneumoniae in addition to atypical organisms”.

Sepsis is less common with vaccination. The most common postoperative complications are vaso-occlusive episodes and Acute Chest Syndrome, reported especially after appendectomy and Cesarean, but also high after umbilical hernia repair, cholecystectomy, and splenectomy. Stroke and death were reported more rarely.

Anesthesia goals are to maintain oxygenation and hydration, avoid acidosis, and maintain normocarbia, normotension, and normothermia, as well as adequate analgesia.

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Concussion and Anesthesia

The APSF provides an article on the definition, pathophysiology and management of concussive head injuries.  Numerous alterations in brain metabolism, cerebral blood flow, and neuronal dysfunction occur, and possible deposition of beta-amyloid and neurofibrillary tangles in chronic concussions.

The authors suggest the concussed brain is vulnerable to anesthesia and it may be prudent to delay elective procedures.



Intranasal Pediatric Sedation

Young children undergoing trans-thoracic echocardiography were sedated with intranasal Dexmedetomidine 2mcg/kg plus Ketamine 1mg/kg.  Sedation was successful in 96%, onset being about 16 minutes. Cyanotic heart disease, history of sedation failure, history of congenital heart disease surgery, and fever were independent risk factors for sedation failure. There were no serious adverse cardiorespiratory side effects.

This non-opioid combination was found to be effective with an acceptable safety profile.



Diastolic Dysfunction and Adverse Cardiac Outcomes

This study focussed on isolated diastolic dysfunction (where Ejection Fraction > 50%). Less extensively studied than systolic dysfunction, diastolic dysfunction is associated with age, ischemia, hypertension and diabetes. These authors found that in patients with isolated diastolic dysfunction undergoing noncardiac surgery, 10.0% develop major adverse cardiovascular events (MACEs) during hospital stay after surgery; grade 3 diastolic dysfunction is associated with greater risk of MACEs.

It is unsurprising that severe grade 3 diastolic dysfunction is a higher risk, although this was a retrospective study and most patients had echocardiography due to an already higher risk status because of age and cardiovascular disease.

Other higher risk factors were also extracted from the study: age ≥70 years, body mass index <18.5 kg/m2, hypertension, coronary heart disease, arrhythmia, renal insufficiency, regular glucocorticoid therapy, symptomatic diastolic dysfunction, ASA classification grades III and IV, intraoperative use of vasopressors or antihypertensives, intraoperative fluid infusion rate ≥9.0 mL/kg/h, cancer surgery, duration of surgery ≥120 minutes, and medium- and high-grade complexity of surgery. BMI > 30 was interestingly associated with a lower risk.



Graduated Compression Stockings and DVT

The Cochrane group weigh in on the common thromboembolism deterrent (TED), or graduated compression  stockings (GCS).

The evidence is supportive in surgical patients, not so clear in the medical setting.

“There is high‐quality evidence that GCS are effective in reducing the risk of DVT in hospitalised patients who have undergone general and orthopaedic surgery, with or without other methods of background thromboprophylaxis, where clinically appropriate. There is moderate‐quality evidence that GCS probably reduce the risk of proximal DVT, and low‐quality evidence that GCS may reduce the risk of PE. However, there remains a paucity of evidence to assess the effectiveness of GCS in diminishing the risk of DVT in medical patients”.



Perioperative management of direct oral anticoagulants (DOACS) in cardiac surgery

An international consensus on managing new oral anticoagulants in patients having cardiac surgery provides pertinent information that will enlighten their use outside cardiac surgery also.

Measurement of DOACS may be useful in emergencies or uncertainty, or in significant renal or hepatic dysfunction; however, such measurement as well as routine coagulation testing is not recommended. Greater caution is also needed in the elderly. Dabigatran is particularly dependent on renal function.

Normal prothrombin time or activated partial thromboplastin time results exclude excess levels of dabigatran, rivaroxaban and edoxaban, but not apixaban. Normal thrombin time precludes significant dabigatran plasma levels, and the aPTT shows some correlation here also – for precise measurements, the diluted thrombin time (dTT), the ecarin clotting time or the ecarin chromogenic assay may be used. For the precise measurement of drug concentrations of all FXa inhibitors, chromogenic and calibrated anti‐FXa tests are recommended.

Reversal agents: for dabigatran, idarucizumab is available; for the FXa inhibitors, andexanet alpha has been approved in the US, and ciraparantag is currently under investigation. Ultrafiltration and Hemodialysis are also discussed for Dabigatran, and non-specific approaches of varying efficacy include prothrombin complex concentrate, fibrinogen concentrate, tranexamic acid and/or factor VIIa.

In general, withholding for 2 days is appropriate. For Dabigatran, this may need 3-5 days depending on renal function. Resumption at therapeutic doses is recommended after 2-3 days and after removal of chest drains. (In the non-cardiac surgery setting, resumption may be sooner depending on bleeding risk). Prophylactic doses may be needed sooner after surgery for thromboembolic prophylaxis. Bridging agents are not recommended for interruptions less than 4 days, as increased bleeding without lower thromboembolism is reported. Individualized approaches may be needed based on CHA2DS2‐VASc Score and bleeding risk.

From an anesthesia perspective, neuraxial anesthesia performance should be equated with high bleeding risk and longer interruption may be the preferred – the ASRA provides one such set of guidelines.

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National Emergency Laparotomy Audit (NELA)

The National Emergency Laparotomy Audit (NELA)  2016-2017 is released and provides information on how performance in England and Wales matches benchmarks, and how institutions can compare their performance.

Overall, compared with 2013:

  • hospital stays are about 15 days (4 days less)
  • 30 day mortality 9.5% (down from 11.8%)
  • 87% received a pre-operative CT Scan (up from 80%)
  • One year mortality was 77%, and three year mortality 66%
  • 75% of patients now receive an assessment of risk (up from 71% last year, and 56% in Year 1).

More negative findings were:

  • 76% of patients with sepsis did not receive antibiotics in the one-hour time frame.
  • 77% did not receive geriatric consult even though half were over 70 years old
  • 27% of patients needing the most urgent surgery did not get to the Operating Room in the recommended timeframes
  • Only 66% of consultant anesthesiologists and surgeons (attending physicians) were present in the OR after hours, and 90% during daytime.

NELA Recommendations include:

1. improving outcomes and reducing complications
2. ensuring all patients receive an assessment of their risk of death
3. delivering care within agreed timeframes for all patients
4. enabling consultant input in the perioperative period for all high risk patients
5. effective multidisciplinary working
6. supporting quality improvement.