Learning from Experience – Chapters 3 and 4

INTRA-OPERATIVE

Chapter 3

Air Embolism In Neurosurgery – Clinical Diagnosis

Dr. Vasanthi Vidyasagaran*

Department of Anaesthesiology, Kauvery Hospital, Chennai, Tamilnadu, India

Case 1

A 28-year-old woman, with polycystic ovarian disease was posted for a laparoscopic ovarian cystectomy. She had no other medical illness and was assessed under ASA 1. Her preoperative investigations were within normal limits. She was taken up for surgery under General Anaesthesia.

Patient was pre-medicated with injection Glycopyrrolate 0.2 mg. and Inj. Tramadol 50 mg. After checking the anaesthesia machine, all other equipment including laryngoscope and endotracheal tube, and all drugs, patient was induced with injection Propofol 120 mg, Fentanyl 100 µg, and paralysed with Atracurium 30 mg. Good bag mask ventilation was possible. After muscle relaxation, laryngoscopy showed grade one view and trachea was intubated.

Followinginflation of the cuff, the reservoir bag felt very tight and it was very difficult to ventilate. Breath sounds were heard bilaterally, but diminished in intensity. There were also mild rhonchi. Suspecting bronchospasm, IV Hydrocortisone 100 mg, and Deriphylline were administered, but there was no improvement. Bag mask ventilation before intubation did not reveal any difficulty in ventilation and the saturation was 100%. The problem had occurred only after intubation.

It felt like an obstructed airway. Capnogram showed obstructed airway pattern and set tidal volumes were not achieved. Peak pressures began to rise. Oxygen saturation which was maintained at 100% dropped to 94%

The second differential diagnosis was a blocked tube, and it was planned to change it with a tube exchanger. On deflating the cuff, we were able to ventilate the patient a lot better and the saturation picked up to 96%. Breath sounds were heard along with a leak over the trachea. Capnogram trace was good, confirming tube was in trachea. The cuff was re-inflated, only to encounter the tight bag again.

This confirmed our diagnosis that the problem lay with the cuff of the ETT. Immediately a tube exchanger was used and the tube changed. Ventilation was resumed without any problem and the surgery was completed. Cause of this unusual tight bag following intubation was a faulty cuff.

Observing the endotracheal tube with the cuff inflated, it was noticed that the cuff was floppy, and overhanging and obstructed the Murphy’s eye. The tip of the tube was probably against the bronchial wall and hence there was a near complete obstruction to ventilation. This is more likely to happen in reused endotracheal tubes. This kind of scenario may be seen immediately after intubation or few hours after commencing the surgery, when it will become difficult to change the tube while a procedure is being done. It is very rare, but can be a serious consequence of manufacturing defect. Long hours of surgery, use of Nitrous Oxide, patient positioning, altered anatomy of trachea and bronchial tree may promote herniation of cuff.

Case 2

A young girl was posted for removal of an impacted molar tooth. No significant past medical history. General anaesthesia was induced and nasal endotracheal tube was placed. Soon after connecting to the ventilator, it was recognised that end tidal Capnogram trace showed very low levels. The anaesthetist checked for bilateral air entry. Oxygen saturations were maintained, although airway pressures were high. Senior anaesthetist was called, who checked for compliance using manual bag ventilation. Some resistance was felt. Endotracheal suctioning could not be applied through the nasal RAE tube. Hence it was decided to change the tube. This was done smoothly. On examining the used tube, it was seen that a thick mucus plug had blocked the tube causing the problem.

Lesson

If in doubt, manually ventilate using the bag and check for compliance and do not hesitate to change the tube. This may sound very basic, but there have been instances when the anaesthetist is hesitant to change the tube and land up in trouble later.

Discussion

Cuff checks are mandatory prior to use, even in new tubes. In fact, they should be inflated and deflated. Normal appearing cuffs may get damaged during intubation. It is more likely to happen during nasal intubation, but can happen during oral intubation too, where teeth, especially if it is a full set of teeth with small mouth opening, can damage the tube. Hence, when there is difficulty in ventilation, all causes must be ruled out quickly. These could be several factors like bronchospasm, kinking and position of the tube, and cuff integrity. Never reuse disposable tubes (which is sometimes done for want of adequate supply) No time must be wasted to diagnose and initiate appropriate treatment.

It is worthwhile to hand ventilate soon after intubation, before connecting to the anaesthetic ventilator. Any difficulty in ventilation can be picked up without any delay.

Auscultation with a stethoscope will also aid in early diagnosis of a complication due to aventilation. This is often not done by the anaesthetist in training in recent times.

Points to remember whilst performing nasal intubation:

Preoperatively, check for patency of nostrils, and ask for any history of nasal obstruction.

Endoscopic check of the nostril may help.

Preparation of nostrils with vasoconstrictor drops or pack with small strips of gauze soaked in lignocaine with adrenalin (making sure to keep a count and remove before intubation) and lubricating the nostrils and the tube.

A smaller tube may be required to pass through the nostrils.

Sometimes it is useful to dip the tube in hot water to soften the tube prior to nasal intubation, but remember the tube should not be too hot for fear of causing damage to the mucosa.

Positioning (sniffing in the morning air) for intubation is important Procedure – be firm, yet gentle, do not use too much force

It must be remembered that, when nasal RAE tube is used, suction catheter may not reach the end of the tube.

Once tube has been passed from nasopharynx to oropharynx, look at the tip of the tube to check for any obstruction with mucus plugs, parts of turbinate, adenoid tissue, or blood clot, whilst performing direct laryngoscopy. This obstruction should be cleared prior to intubation.

Even if there is an equipment failure, we are responsible.

References

Kao MC. Airway obstructioncaused by endotracheal tube cuff herniation during creation of tracheal stoma. Acta Anaesthesiol Taiwan. 2005;43(1):59-62.
O’Reilly MJ, Reddick EJ,Black W, et al. Sepsis from sinusitis in nasotracheally intubated patients. A diagnostic dilemma. Am J Surg. 1984;147(5):601-4.
Hall CE, Shutt LE.Nasotracheal intubation for head and neck surgery. Anaesthesia. 2003;58(3):249-56.
Johnson KM, Lehman RE. Acute management of the obstructed endotracheal tube. Respir Care. 2012;57(8).
Hofstetter C, Scheller B,Hoegl S, et al. Cuff overinflation and endotracheal tube obstruction: case report and experimental study. Scand J Trauma Resusc Emerg Med. 2010;18(18):1-5.

Chapter 2

Alternative Medicine and Abnormal Haemodynamic Response

Case 1

A woman with history of chronic renal impairment was posted for arterio-venous fistula procedure. History suggested patient was on some holistic medicine tablets for arthritis for the past 20 years. Her blood pressure was under control with anti-hypertensives. She did not have any other systemic illness.

There was unexpected bleeding of more than 500 ml for a minor procedure and the patient was already quite anaemic with a Hb of 6 gms %. There was also a continuous oozing from the wound.

Replacement therapy with platelets, and fresh frozen plasma had to be done to bring the bleeding under control. Although platelet dysfunction exists in patients with chronic renal failure, other drugs taken by the patient may make the situation worse, and sometimes cause excess blood loss as seen in this patient. This excess bleeding could have been due to various causes including the alternative medicine tablets which she had been consuming for several years.

Case 2

A 50-year-old moderately obese man weighing 95 kg, a known diabetic was posted for manipulation of frozen shoulder under anaesthesia. It was to be done as a day care procedure. Blood investigations were within normal limits.

Anaesthesia was induced with Propofol 160 mg, and Fentanyl 100 mcg. Airway was maintained with face mask providing Oxygen, Nitrous oxide and Sevoflurane. During manipulation, he developed bradycardia. Pulse rate gradually dropped from 80 to 40 beats/min. Oxygen saturation was normal. Patient remained hemodynamically stable.

Assuming vagal response to pain, anaesthesia was deepened, and Glycopyrrolate 0.2 mg was given. Heart rate improved, but patient soon developed tachycardia. Airway was secured with a laryngeal mask and ventilation was good. Heart rate remained at 140/min for longer than anticipated with the administered dose of Glycopyrrolate, despite adequate anaesthesia and analgesia. Rhythm continued to be normal. Preservative free lignocaine 1 mg/kg was slowly infused over the next 10 min. Patient responded and his heart rate stabilized at 80/min. Recovery was uneventful. Postoperatively the family mentioned that he had been on homeopathic medicine also for arthritis for nearly ten years.

Diabetes related autonomic neuropathy may be the first reason to explain the exacerbated bradycardic response. However, the brady-tachy response despite adequate analgesia and anaesthesia may be due to autonomic imbalance aggravated by polypharmacy and drug interaction between allopathic and alternative medicines. This may simulate seratogenic crisis. This case is mentioned here to highlight the fact that unexpected events may happen when the patients are on alternative medicines.

Discussion

People across the world follow a holistic and combined approach to their medical problems. With a wide variety of herbal and naturopathic medications available, patients are on multiple treatment at the time of presentation. There is a common belief that they are totally harmless with no side effects, with benefits to the heart and kidney. Patients do not mention that during assessment.

The American Society of Anaesthesiologists on its website, recommends patients to bring all substances with prescription or over-the-counter when they meet the anaesthesiologist before surgery or on the day of surgery. Awareness has to be created among surgeons, anaesthesiologists and general public regarding the possible interactions with anaesthetic agents and complications during surgery, even if it is minor.

Some of the drugs commonly seen in our practice:

Gingko: a free radical scavenger, neuroprotective – increases risk of bleeding and hypoglycaemic effect during surgery.
Ginseng: mood enhancer, sympathomimetic – may need to be discontinued for 10 days prior to surgery.
St Johns Wart: antidepressant – seratogenic crisis may be evoked, needs to be discontinued 5 days prior to surgery.
Valerian: anxiolytic, hypnotic – potentiates GABA system, may reduce anaesthetic requirements.

Apart from these, there are other drugs resembling steroidsas well as those containing heavy metals like lead. Evaluation of the cardiac, renal, liver and the haemopoitic system preoperatively will be of immense use in those taking long term alternative medication. Even if patients do not reveal their medication history, probing questions should be asked especially in those receiving treatment for arthritis, infertility, asthma, and sinusitis.

References

Wong A, Townley SA. Herbal medicines and anaesthesia. Contin Educ Anaesth Crit Care Pain. 2011;11(1):14-7.
American Society of Anaesthesiology. What you should know about herbal and dietary supplement use and anaesthesia. Patient Information Leaflet. 2003.
Hodges PJ, Kam PCA. The peri-operative implications of herbal medicines. Anaesthesia 2002;57:889-99.
Singh Bajwa SJ Panda A. Alternative medicine and anaesthesia: Implications and considerations in daily practice. Ayu. 2012;33(4):475-80.

Learning from Experience – Chapters 3 and 4

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