Early post-operative care - Anesthesia

Post-operative care

The post-operative care of the patient can be divided into an early and a continued phase. The early phase lasts from the moment the patient leaves the operating room until he is discharged from the Post-Anesthesia Care Unit (PACU) or its equi-valent. The care is then continued, a phase that can extend for days or even weeks.

Early post-operative care

Based on his medical condition and the planned operative procedure, we will have classified the patient as ambulatory (also known as outpatient), as ‘post-operative admit’ (the patient comes to the hospital on the day of the operation and is admitted to the hospital after his operation), or as an inpatient (the patient is already in the hospital, or will be admitted for pre-operative preparation, and will stay there post-operatively). Two categories of patients might bypass the PACU (formerly called the Recovery Room): (i) ambulatory patients who had a minor procedure and are expected to be ready for discharge in a matter of minutes and (ii) patients requiring intensive care because of serious pre-operative med-ical problems or major operations with potential complications. Such patients are admitted directly to the Intensive Care Unit (ICU) upon completion of the operation.

 For patients coming to the PACU we consider three factors: the patient’s pre-operative condition; the effects of the just completed therapeutic (surgical, radio-logical, obstetrical, electroconvulsive) or diagnostic procedure; and the effects of the anesthetic. As we turn the patient’s care over to the PACU staff, we provide a formal “report” of his condition including the following:

·           pre-existing medical conditions with particular emphasis on pre-existing respiratory, cardiac, and chronic pain issues;

·           surgical disease, operative and anesthetic course, and any problems encoun-tered;

·           fluid status including what was administered, estimated blood loss, and urine output;

·           medications administered in the operating room. We mention antagonists given to counteract lingering neuromuscular weakness or respiratory depression or nausea and vomiting. Should the patient need more such medication, the PACU physician can either continue the already initiated treatment or, if the patient does not respond, switch to another drug;

·           concerns regarding the procedure or the patient, including the plan for post-operative pain management;

·           issues requiring follow-up such as pending laboratory evaluations or a chest radiograph to confirm central venous catheter placement.

Finally, we make certain the patient is stable, record a first set of vital signs obtained in the PACU, and ensure that all documentation is complete and correct.

In the PACU, we first worry about safety. We consider waning anesthetic drug effects as they relate to adequacy of oxygenation, which in turn requires an alert respiratory center (is there a hangover effect from CNS depressants?) and the muscle power to breathe (is there a hangover effect from muscle relaxants or a regional anesthetic?), an open airway (is there obstruction of the upper airway?), and no encumbrance to breathing from dressing, position, or the surgical proce-dure. Adequacy of oxygenation also requires adequate circulation (is the blood pressure normal and the ECG unchanged from its preoperative state?). The pulse oximeter will speak volumes to these questions. If the patient is breathing roomair and his oxygenation (as measured by pulse oximetry located peripherally) isnormal, we can be assured of adequate breathing.

We assess the central nervous system, recognizing that the patient usually will have had a number of drugs with CNS effects. With modern anesthetic techniques and drugs, we expect the patient to rally from the depressant effects of the drugs fairly rapidly and to become responsive, if not immediately oriented. Up to 25% of elderly patients will be delirious after a general anesthetic for a major surgical procedure. Once a patient is not only responsive but also oriented, we know that his brain is perfused and oxygenated.

Most patients will arrive with an intravenous infusion. If we assume that the patient is in a neutral fluid balance (blood pressure and urine output back to preoperative values), in short, if his insensible losses (about 800 mL/day) and intra-operative losses (from evaporation from exposed surfaces, e.g., intestines, bleeding and from edema caused by the surgical trauma (the so-called third space or blister)) have been replaced, fluid therapy will simply continue to replace insen-sible losses following the 4–2–1 rule (see Table 6.1).

Often enough, however, some bleeding continues – usually invisibly – into the traumatized tissue. Fluid therapy will need to be adjusted to meet the patient’s requirements as judged by cardiovascular signs and urine production. A bal-anced salt solution such as normal saline or Ringer’s lactate will serve as long as there is no need to worry about electrolytes, red blood cells, and plasma proteins.

Early post-operative pain

As we reassure ourselves as to the patient’s safety, we begin to consider the patient’s pain. Three points need attention: (i) surgical incisional pain will decrease over time, (ii) analgesic effects left over from the anesthetic will wane over time, and (iii) pain counteracts the CNS depressant (respiratory) effects of narcotic analgesics (Fig. 6.1). Thus, pain management in the PACU must seek a balance of three shifting slopes of which we do not know the rate of change. This translates into: watch the patient and titrate drugs to balance adequate analgesia and avoid respir-atory depression. As long as the patient cannot take oral medication, a practical approach for the acute phase of pain management in the PACU can make use of intravenous morphine in 2.0 mg increments for the average adult. It takes about 5 minutes for such a dose to show an effect. Therefore, wait at least 5 minutes before giving the next dose. Many factors influence the patient’s response to such treatment. A patient on chronic narcotic therapy will require more, a frail elderly person less. Titrate! Titrate! Titrate!

After minor surgical procedures, many patients will not require opioids at all, and most can take oral medication. The pharmacology chapter gives drugs and dosages.

There would be no need for a PACU if it were not for the occasional complica-tions that require early recognition and prompt treatment. Here is a quick review of potential problems encountered in the PACU.

Complications

Desaturation

Differential diagnosis

·           Hypoventilation Always first assist ventilation to establish normal SpO₂ and PaCO₂! Then consider causes and their treatment.

Residual neuromuscular blockadeSuspected when the patient shows anabnormal respiratory pattern, particularly the tracheal tug, i.e., downward motion of the larynx with inspiration. Test with the twitch monitor. Treat with reversal agents.

– Residual sedationConsider reversal of benzodiazepines with flumazenil.

– NarcosisTypically a slow, deep respiratory pattern; consider cautious reversalof opioids with naloxone.

– Bronchospasm (wheezing)Intubation is a strong stimulant for bronchospasm;treat with bronchodilators.

– Laryngospasm (stridor)If related to the operation, e.g., neck operation withpossible hematoma formation, it becomes a surgical emergency. Try continu-ous positive airway pressure, letting the patient exhale against resistance (5 to 10 cmH₂O) and maintaining that pressure throughout the respiratory cycle.

– PainParticularly with a subcostal incision where deep breathing is painful.

·           Ventilation/Perfusion mismatch

– AtelectasisProbably the most common cause of post-operative hypoxemia.

– Aspiration of gastric contentsParticularly in high-risk patients, or if intubationrequired multiple attempts.

– PneumothoraxEspecially after central venous access. Obtain a chest radio-graph, but be prepared to relieve the pneumothorax by puncture (2nd inter-costal space, mid-clavicular line) should a tension pneumothorax develop in the meantime.

– Pulmonary embolismThromboembolism is the most common. May needV/Q or CT scanning. Most surgical patients require some form of prophylaxis against deep vein thrombosis (DVT).

– Pneumonia

– Mainstem intubation

·           Diffusion block

– Pulmonary edema

_·            Inadequate FiO₂

Management

(i)Airway

Chin lift, neck extension; continuous positive airway pressure (CPAP) often helps. For this, use a bag and mask system (Mapleson – see The anesthesia machine) with a high flow (15 L/min) of oxygen. Apply the face mask tightly, letting the patient exhale against resistance (5 to 10 cmH₂O) and maintain that pressure throughout the respiratory cycle.

(ii)     Breathing

·           Supplemental oxygen

– Via nasal cannula, but with oxygen flows of 2 L/min the inspired O₂only increases by about 6%.

         – Via standard tent face mask for an inspired O₂of up to 50%

– Via partial rebreathing face mask for an inspired O₂of up to 80%

– Via non-rebreathing face mask for an inspired O₂of up to 95%

·           Encouragement – “take a breath!” often effective with narcotic depression

·           Bag–Mask – use with self-inflating bag or Mapleson

·           Check ventilator settings, O₂ supply and end-tidal CO₂ if the patient is intubated.

(iii)         Studies to consider

·           Chest radiograph if abnormal breath sounds (pneumonia, atelectasis, pneumothorax, +/− aspiration). Keep in mind, however, that a portable film may not provide the highest quality and consolidation takes some time to manifest radiographically.

·           Arterial blood gas

·           Twitch monitor if patient appears to be partially paralyzed.

Hypotension

Differential diagnosis

·           Inadequate preload

– Inadequate fluid resuscitation

– Continued hemorrhage

– Venodilation due to medications or sympathetic blockade

– Pericardial tamponade

– Pulmonary embolism

– Increased intra-abdominal pressure, e.g., big uterus pressing on vena cava

– Increased intra-thoracic pressure, e.g., tension pneumothorax

·           Poor contractility

– Residual anesthetics

– Myocardial ischemia

– Fluid overload (“far-side” of the Starling Curve)

– Pre-existing cardiac dysfunction

– Electrolyte disturbance

– Hypothermia

·           Inadequate afterload

– Sepsis

– Vasodilation due to medications or sympathetic blockade, e.g., neuraxialanesthetic

– Anaphylaxis

·           Arrhythmias

– Bradycardia

– Loss of atrial kick

Atrial fibrillation/flutter AV dissociation

– Electrolyte disturbance

Management

·           Physical examination (especially chest auscultation)

·           ECG (at least 5-lead strip) to detect arrhythmias and ischemia ACLS protocol if abnormal rhythm

·           Hemoglobin level

·           Intravascular fluid resuscitation +/− blood transfusion Supplemental oxygen

·           Elevate legs to enhance venous return Consider transthoracic echo

·           Consider chest radiograph

·           Consider invasive monitoring

·           Check electrolytes, especially Ca²⁺ for inotropy and K⁺ , Mg²⁺ for arrhythmias

Hypertension

Differential diagnosis

·           Pain

·           Pre-existing hypertension Bladder distension

·           Rebound hypertension (especially with chronic clonidine) Endocrine problem (thyroid storm, pheochromocytoma) Malignant hyperthermia

·           Delirium tremens

·           Increased intracranial pressure

Management

·           Treat pain or anxiety if present.

·           Review for pre-existing hypertension and reinstitute anti-hypertensive therapy where appropriate.

·           Check ECG.

·           Look for additional signs of malignant hyperthermia.

·           Check for high bladder dome. If Foley catheter in place, check patency, or per-form in-and-out catheterization.

We hope that none of these problems arose or that they have been dealt with successfully, at which point we are ready to discharge the patient from the PACU.

PACU discharge

A frequently used checklist is the Aldrete Recovery Score (see Table 6.2). If the sum of points reaches 9 or 10, we can discharge the patient from the PACU.

Outpatients

After outpatient procedures under local or peripheral nerve block anesthe-sia, perhaps with parenterally administered CNS depressants, e.g., midazolam (Versed®), propofol or opioids, the patient may bypass the PACU unless a med-ical condition would call for observation. It may be necessary to prescribe an oral analgesic that might include a mild opioid.

If no CNS depressant drug was used during the procedure and if the peripheral nerve block is behaving as expected (surgical anesthesia wearing off, but perhaps analgesia continuing), the patient can be discharged. We still insist that a relative or friend accompany them home because the patient will have been exposed to the stress of an operation – however minor – and will have been fasting and thus be at risk of swooning or even fainting and not being at the height of his reflex responses.

For those patients who required CNS depressants for a short operative proce-dure in which no severe post-operative pain is expected, e.g., a sigmoidoscopy under propofol sedation or a cataract removal under local anesthesia preceded by a small (0.5 to 0.75 mg/kg) dose of methohexital (Brevital®) to minimize the discomfort of the retrobulbar block, the recovery process can be completed in a matter of minutes to an hour, at which point the patient can be discharged into the care of a relative or friend for transportation home. We always assume that drug effects and hormonal disturbances will linger for a matter of several hours to a day, so that upon discharge, the patient cannot be considered ready to drive an automobile or ride a bicycle or even cross the street by himself.

For those patients who remain in the hospital following their operation, PACU discharge signals the phase of continued post-operative care.